Amplifier Voltage Gain matching your Preamp and Amplifier

P

PENG

Audioholic Overlord
As you might have expected of me, PENG, I read the specs before ordering. I suspect the problem is one or more of the following:

- The 975 doesn't have an output level problem; it has an input sensitivity problem, and has substantially less than unity gain.

- The 975 has an unusually low input impedance, perhaps because of a design defect, and is somehow stressing the cheap output devices of certain components, like the cheap Sony BD player. (I doubt this is the reason, but I don't know.)

- The 2V output spec is simply incorrect, or wasn't met in the first version of the product, which I have. (I suspect this is the real reason.)

- The ATI AT602 gain is not 28db, it is only 24db, which is woefully low. If you look at the ATI web site, which was my reference, gain is listed at 28db. If you read the owners manual, I just noticed it is listed at 24db. 24db, if correct, is the lowest gain I've ever encountered for a power amplifier. (24db of gain in conjunction with less output from the 975 than advertised could be a double whammy.)

So, I'm thinking this is a genuine case of components that are just incompatible, especially when the electronics chain is pair with a set of JBL speakers that are probably 82db/2.83v/m, sensitivity-wise. And I'm also thinking that y'all ought to consider the silliness of being so dismissive of a situation that when discussed gets an immediate match from an audience with such a small population.
I did expect you to read the specs, that's why I asked for explanation instead of doubting you. And you did not disappoint.:D

To add to your list of suspected causes, I noticed that the output impedance is stated as:

"Output Impedance (Main-RCA) <1 KΩ"

So it could be 999 ohms and that is not low for sure, but probably just a minor factor, as most amps, presumably including the AT602, should have input impedance >10K. Still, when you add everything up, that Outlaw is probably only good for amps with >32 dB gains.

If it has decent input sensitivity and reasonably low output impedance, even 1V can drive the 24 dB gain AT602 to its rated output but it certainly can't do anything to the ATI's larger amps.

fmw may be right about in the majority of cases, but I do think it's time manufacturers be more specific about their preamp outputs. As it is now, it seems to me most of them are vague, you just can't draw conclusions without seeing bench test data. Fortunately so far any of my AVR, preamps and prepros have no trouble driving any of my power amps. I hope that Outlaw is the only one that failed you.
 
N

Niklasmagnus

Audiophyte
I read the article but still dont fully understand how to set up my Receiver /minidsp / Power amps.
I run a Marantz SR7009 to Minidsp and then to one Crown CTs600 for the subs. And from Marantz to one Crown CT4150 for LCR.

Marantz is speced for 1,2 V output (I guess at Chanel 0 dB in AVR settings)
Minidisp Bal are set for 2 V input (0,9 V optional) and fixed 2V output
CTs600 has sensitivity 1.4 V
CT4150 has sensitivity 1.4 V

I have then measured the RCA pre outoputs on the Marantz in stereo mode with a Volt meter. AVR master volume 0dB, REW -3dBFS, connected by HDMI from PC to AVR. PC volume 100%. Crossover 250Hz main / sub. Sinus tone 60 Hz for sub and 1000 Hz for main.
Adjusted the channel levels in AVR for hitting correct Volt according to "input side".
AVR preout LCR: +2.5 dB > 1,46 V (for the CT4150)
AVR preout sub: -1 dB > 1.99 V (for the minidsp)
Minidsp fixed 2 V (for the CTs600)

Ive been following this guide, page 21:
h t t p s : / / w w w .oaudio.de/out/media/Multi-Sub_SetUp2x4.pdf#page37

Are I doing this correct or not, need some support.
 
P

PENG

Audioholic Overlord
I read the article but still dont fully understand how to set up my Receiver /minidsp / Power amps.
I run a Marantz SR7009 to Minidsp and then to one Crown CTs600 for the subs. And from Marantz to one Crown CT4150 for LCR.

Marantz is speced for 1,2 V output (I guess at Chanel 0 dB in AVR settings)
Minidisp Bal are set for 2 V input (0,9 V optional) and fixed 2V output
CTs600 has sensitivity 1.4 V
CT4150 has sensitivity 1.4 V

I have then measured the RCA pre outoputs on the Marantz in stereo mode with a Volt meter. AVR master volume 0dB, REW -3dBFS, connected by HDMI from PC to AVR. PC volume 100%. Crossover 250Hz main / sub. Sinus tone 60 Hz for sub and 1000 Hz for main.
Adjusted the channel levels in AVR for hitting correct Volt according to "input side".
AVR preout LCR: +2.5 dB > 1,46 V (for the CT4150)
AVR preout sub: -1 dB > 1.99 V (for the minidsp)
Minidsp fixed 2 V (for the CTs600)

Ive been following this guide, page 21:
h t t p s : / / w w w .oaudio.de/out/media/Multi-Sub_SetUp2x4.pdf#page37

Are I doing this correct or not, need some support.
I am not exactly clear how you are doing it as the numbers would depend on the specific minidsp models, I assume your have the non HD model but not sure it you have the 2V or 4V balanced version.

I would simply do the following, assuming your goal is just to level match all channels including the subwoofer channel:

The quickest way:
Since your system is controlled by the SR7009, simply run auto setup and let Audyssey does it for. (This is the best way). This should get you more accurate results for the subwoofers.

The manual way:
Once everything is hooked up, adjust the levels for all channels (setup/speakers/Manual setup/levels) so that the spl meter using "C" weighting slow read the same for all channels including the subwoofers.

Using the voltmeter:

This could work if you know the sensitivities of each speakers and subs, as well as the exact gain of the power amps. The specs say 31 dB for the CTs600 and 27 dB for the CT4150 but a) those numbers are typically approx, to one decimal point hopefully) and b) the sensitivities of the speakers in their location are unknown, so I highly doubt you can level match them properly using the voltmeter method.
 
M Code

M Code

Audioholic General
The key point for setting pre-out & main-in levels is to set it high enough for the best dynamic range and not to the highest as to introduce more noise or cause overload or clipping..
IMHO... After many years of setting up multiple systems for stereo, multi-channel and pro-audio using various components I prefer to set the levels @ about 70% rotation. Then if final tweaking is required U can go up/down as needed..

Just my $0.02... ;)
 
N

Niklasmagnus

Audiophyte
I am not exactly clear how you are doing it as the numbers would depend on the specific minidsp models, I assume your have the non HD model but not sure it you have the 2V or 4V balanced version.

I would simply do the following, assuming your goal is just to level match all channels including the subwoofer channel:

The quickest way:
Since your system is controlled by the SR7009, simply run auto setup and let Audyssey does it for. (This is the best way). This should get you more accurate results for the subwoofers.

The manual way:
Once everything is hooked up, adjust the levels for all channels (setup/speakers/Manual setup/levels) so that the spl meter using "C" weighting slow read the same for all channels including the subwoofers.

Using the voltmeter:

This could work if you know the sensitivities of each speakers and subs, as well as the exact gain of the power amps. The specs say 31 dB for the CTs600 and 27 dB for the CT4150 but a) those numbers are typically approx, to one decimal point hopefully) and b) the sensitivities of the speakers in their location are unknown, so I highly doubt you can level match them properly using the voltmeter method.
The MiniDSP is a non HD Balanced with in 0,9/2 V and fixed out 2V.

As I did it was to set the Vrms for the outputs according the above and then use a SPL meter to level the volume by adjusting on the power amps gain control.

If doing the quick way, running Audyssey, the problem is, as I understand, that the level for the pre-sub might go higher then 2V and minidsp will clip the signal?
And the "opposite" for the pre-out LCR are if Vrms is too low I want get full amplification from the CT4150?
 
P

PENG

Audioholic Overlord
The MiniDSP is a non HD Balanced with in 0,9/2 V and fixed out 2V.

As I did it was to set the Vrms for the outputs according the above and then use a SPL meter to level the volume by adjusting on the power amps gain control.

If doing the quick way, running Audyssey, the problem is, as I understand, that the level for the pre-sub might go higher then 2V and minidsp will clip the signal?
And the "opposite" for the pre-out LCR are if Vrms is too low I want get full amplification from the CT4150?
If you use spl meter to monitor spl, while adjusting the level then okay..

So you measure the voltages just to make sure they are all below 2V?

If you don't sit too far you are likely fine, but it depends on your seating distance and desired spl.

The minidsp2x4 balanced apparently has two versions, the newer one can output 4V balanced, 2 V unbalanced. If yours can only do 2V balanced, then there is a good chance the CT4150 may clip. So how far do you sit and what's your spl requirement?
 
N

Niklasmagnus

Audiophyte
If you use spl meter to monitor spl, while adjusting the level then okay..

So you measure the voltages just to make sure they are all below 2V?

If you don't sit too far you are likely fine, but it depends on your seating distance and desired spl.

The minidsp2x4 balanced apparently has two versions, the newer one can output 4V balanced, 2 V unbalanced. If yours can only do 2V balanced, then there is a good chance the CT4150 may clip. So how far do you sit and what's your spl requirement?
Please read my original post so you understand my question.
 
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P

PENG

Audioholic Overlord
Please read my original post so you understand my question.
Wow, that almost sounded rude, but may be I misunderstood something. I read your original post at least twice and I thought I needed more info in order to answer you question. In any case I took the time to read the manuals of your two power amps, the minidsp 2X4 and the 2X4 balanced as I am only experienced in the 2XHD. I asked your seating distance not out of concern about clipping while taking measurements, but about clipping when you are actually using the system. I should have asked about your speaker's sensitivity too, but anyway I'll withdraw those questions. Sorry for asking (in trying to offer help that you obviously don't seem to need).

Back to your only question in your original post, that is "Are I doing this correct or not, need some support. " (copied and pasted from your post#62). For reason I mentioned earlier, I really couldn't say you did it correctly, or not until more info was provided in your follow up post.

You post#65 made things much clearer, as now we know your have the minidsp 2X4 balanced (that offers both unbalanced and balanced connection options), so that means you can use the unbalanced input with the SR7009, and that you were using a spl meter while adjusting the receiver's channel levels. So then I answered your earlier question by saying: If you use a spl meter to monitor spl, while adjusting the level then okay.." I could have said please read my post for my answer, but that would be a little rude..

Since you added a second question in post#65: "If doing the quick way, running Audyssey, the problem is, as I understand, that the level for the pre-sub might go higher then 2V and minidsp will clip the signal?", and I responded: "If you don't sit too far you are likely fine, but it depends on your seating distance and desired spl." That was actually wrong on my part because Audyssey's test tone (pink noise) for calibration is at -30 dBFS, so unless you sit (mic positions)really/unrealistically far, like doing it outdoor, and you speakers have exceptionally low sensitivity, the chance of clipping should be practically 0. I should have just told you not to worry about clipping at all.

To conclude, I would say you did do it correctly, in trying to balanced the levels of all channels including the sub's, but doing it with a -3 dBFS tones are unnecessarily loud. The minidsp is rated for 2 V maximum, so why push it so close? (you said 1.99V). Audyssey's test tone is at -30 dBFS, so if you do your tests with a -20 dBFS, you won't have to be concerned about clipping at all. Again, you did it right, I am only offering my 2 cents (feel free to ignore it), about using a lower level tone, and the resulting lower voltages.
 
N

Niklasmagnus

Audiophyte
Wow, that almost sounded rude, but may be I misunderstood something. I read your original post at least twice and I thought I needed more info in order to answer you question. In any case I took the time to read the manuals of your two power amps, the minidsp 2X4 and the 2X4 balanced as I am only experienced in the 2XHD. I asked your seating distance not out of concern about clipping while taking measurements, but about clipping when you are actually using the system. I should have asked about your speaker's sensitivity too, but anyway I'll withdraw those questions. Sorry for asking (in trying to offer help that you obviously don't seem to need).


Back to your only question in your original post, that is "Are I doing this correct or not, need some support. " (copied and pasted from your post#62). For reason I mentioned earlier, I really couldn't say you did it correctly, or not until more info was provided in your follow up post.

You post#65 made things much clearer, as now we know your have the minidsp 2X4 balanced (that offers both unbalanced and balanced connection options), so that means you can use the unbalanced input with the SR7009, and that you were using a spl meter while adjusting the receiver's channel levels. So then I answered your earlier question by saying: If you use a spl meter to monitor spl, while adjusting the level then okay.." I could have said please read my post for my answer, but that would be a little rude..

Since you added a second question in post#65: "If doing the quick way, running Audyssey, the problem is, as I understand, that the level for the pre-sub might go higher then 2V and minidsp will clip the signal?", and I responded: "If you don't sit too far you are likely fine, but it depends on your seating distance and desired spl." That was actually wrong on my part because Audyssey's test tone (pink noise) for calibration is at -30 dBFS, so unless you sit (mic positions)really/unrealistically far, like doing it outdoor, and you speakers have exceptionally low sensitivity, the chance of clipping should be practically 0. I should have just told you not to worry about clipping at all.

To conclude, I would say you did do it correctly, in trying to balanced the levels of all channels including the sub's, but doing it with a -3 dBFS tones are unnecessarily loud. The minidsp is rated for 2 V maximum, so why push it so close? (you said 1.99V). Audyssey's test tone is at -30 dBFS, so if you do your tests with a -20 dBFS, you won't have to be concerned about clipping at all. Again, you did it right, I am only offering my 2 cents (feel free to ignore it), about using a lower level tone, and the resulting lower voltages.
Sorry, not my intention to sound rude. This was a double misunderstanding from my side. Thanks you so much for giving me the well written answer and not just give me the middle finger.

Using the voltmeter:

This could work if you know the sensitivities of each speakers and subs, as well as the exact gain of the power amps. The specs say 31 dB for the CTs600 and 27 dB for the CT4150 but a) those numbers are typically approx, to one decimal point hopefully) and b) the sensitivities of the speakers in their location are unknown, so I highly doubt you can level match them properly using the voltmeter method.
So the LCR speakers are Jamo D500 and the subs are DIY scan speak 30w/4558t00 I 95 liter sealed boxed. So I don’t have the exact numbers other then the data from their websites, but I guess that’s not good enough in same way we cannot take dB number for real of the Crowns from website.
So this is a dead end, if I understand.?.

If you use spl meter to monitor spl, while adjusting the level then okay..

So you measure the voltages just to make sure they are all below 2V?

If you don't sit too far you are likely fine, but it depends on your seating distance and desired spl.

The minidsp2x4 balanced apparently has two versions, the newer one can output 4V balanced, 2 V unbalanced. If yours can only do 2V balanced, then there is a good chance the CT4150 may clip. So how far do you sit and what's your spl requirement?
I measured and adjusted the voltages on the AVR pre-out sub to make sure it was below 2V since minidsp are 2 V sensitive. For pre-out LCR I measured and adjust to >1,4 V to match CT4150 sensitivity 1,4V so I will get full power. In my understanding this was the way to do it, but I´m questioning myself on all my understanding about this now.
Ref: h t t p s : / / w w w.minidsp.com/applications/dsp-basics/gain-structure-101

I sit about 3 meters from sub, 3 M from centre and 3,5 m from LR. I have not played with SPL requirements, only trying to get even level speaker to speaker running the AVR channel levels setting noise.

Yes, my minidsp2x4 bal is an older version with 0.9/2V in and fixed 2 V out.

Wow, that almost sounded rude, but may be I misunderstood something. I read your original post at least twice and I thought I needed more info in order to answer you question. In any case I took the time to read the manuals of your two power amps, the minidsp 2X4 and the 2X4 balanced as I am only experienced in the 2XHD. I asked your seating distance not out of concern about clipping while taking measurements, but about clipping when you are actually using the system. I should have asked about your speaker's sensitivity too, but anyway I'll withdraw those questions. Sorry for asking (in trying to offer help that you obviously don't seem to need).
Again, sorry. The Jamo D500 are 89 dB/1 watt and 4 ohm. My sub driver are 89 dB and 4 ohm, not sure what the driver+ box are.

You post#65 made things much clearer, as now we know your have the minidsp 2X4 balanced (that offers both unbalanced and balanced connection options),so that means you can use the unbalanced input with the SR7009, and that you were using a spl meter while adjusting the receiver's channel levels. So then I answered your earlier question by saying: If you use a spl meter to monitor spl, while adjusting the level then okay.." I could have said please read my post for my answer, but that would be a little rude..
The minidsp can be runned as unbalanced with the wiring on page 24 in manual:
H t t p : / / w w w.minidsp.com/images/documents/miniDSP%20Balanced%202x4%20and%20Kit%20-%20User%20Manual%20v2.2.pdf

Since you added a second question in post#65: "If doing the quick way, running Audyssey, the problem is, as I understand, that the level for the pre-sub might go higher then 2V and minidsp will clip the signal?", and I responded: "If you don't sit too far you are likely fine, but it depends on your seating distance and desired spl." That was actually wrong on my part because Audyssey's test tone (pink noise) for calibration is at -30 dBFS, so unless you sit (mic positions)really/unrealistically far, like doing it outdoor, and you speakers have exceptionally low sensitivity, the chance of clipping should be practically 0. I should have just told you not to worry about clipping at all.

To conclude, I would say you did do it correctly, in trying to balanced the levels of all channels including the sub's, but doing it with a -3 dBFS tones are unnecessarily loud. The minidsp is rated for 2 V maximum, so why push it so close? (you said 1.99V). Audyssey's test tone is at -30 dBFS, so if you do your tests with a -20 dBFS, you won't have to be concerned about clipping at all. Again, you did it right, I am only offering my 2 cents (feel free to ignore it),about using a lower level tone, and the resulting lower voltages.
Since I don’t really know what I´m doing here I followed the guide and on page 21 they state one should use REW and -3 dBFS tones.
h t t p s : / / w w w .oaudio.de/out/media/Multi-Sub_SetUp2x4.pdf#page37

I would love to make this much easier, plug and play. And I do think I make it too complex since people with AV processor are probably not doing measurements and manual adjustments with voltmeter and SPL meter for every channel. And as I understand by doing it this complex I´m not able to run Audyssey for peq since it might change all channel level setting. So just following some rule of thumb sound quite good.

The key point for setting pre-out & main-in levels is to set it high enough for the best dynamic range and not to the highest as to introduce more noise or cause overload or clipping..

IMHO... After many years of setting up multiple systems for stereo, multi-channel and pro-audio using various components I prefer to set the levels @ about 70% rotation. Then if final tweaking is required U can go up/down as needed..

Just my $0.02... ;)
This is the rule of thumb I guess for you experiences. So you set the power amp gain on ~70%. Are you also setting ~70 % in MiniDSP software for sensitivity and output?

PENG do you have any input?

Thank you so much for helping me!
 
P

PENG

Audioholic Overlord
So the LCR speakers are Jamo D500 and the subs are DIY scan speak 30w/4558t00 I 95 liter sealed boxed. So I don’t have the exact numbers other then the data from their websites, but I guess that’s not good enough in same way we cannot take dB number for real of the Crowns from website.
So this is a dead end, if I understand.?.
Not sure what you are asking, is it still about clipping concern? The Jamo D500 LCR's sensitivity is 89 dB/2.83V/1M, and impedance is 4 ohms. If so, yes you need to be careful if you want to stay clear of the clipping point of the pre out and the power amp for the following reasons.

If you sit 3.5 M from the LCR, you will need about 500 W to hit reference level 105 dB peak, with 1 speaker. The D500 is rated 150 W long term, 200 W short term, so yes you can forget about 105 dB (reference) spl.

The Crown CT4150 is rated 125 W/4 ohm. It should be fine if you are happy with not more than 100 dB peak, 80 dB average. The 100 dB peak/80 dB average estimated spl are based on my assumption that your speakers are placed near a wall, so they should be getting about 3 dB of room gain. For 2 speakers playing at the same time you can expect about 3 dB louder on average. Even 80 dB average is quite loud for most people.

As to clipping or not, assuming Crown audio's website is accurate about the gain of the CT4150, with voltage gain of 27 dB, to output 125 W/4 ohm, the input voltage (that is output from the AVR) would need to be about 1 V, so no worry about clipping at all!!

Caution: I would add that the voltage needed could be anywhere between about 1 V to 1.25 V. I am giving you a range because Crown audio is not consistent about the CT4150's gain/sensitivity specs. On the website they say it is 27 dB (that would obviously be the best case scenario),but on the cut sheet it shows 25 dB, yet in the manual it says 26 dB, what a mess!!.

I measured and adjusted the voltages on the AVR pre-out sub to make sure it was below 2V since minidsp are 2 V sensitive. For pre-out LCR I measured and adjust to >1,4 V to match CT4150 sensitivity 1,4V so I will get full power. In my understanding this was the way to do it, but I´m questioning myself on all my understanding about this now.
Ref: h t t p s : / / w w w.minidsp.com/applications/dsp-basics/gain-structure-101
I read that linked applications note. They suggested -3 dBFS because a) that is the maximum REW can do, and more importantly b) they want to make sure even at that high SPL, the AVR's pre out voltage does not exceed the minidsp's rated input voltage. There is no need to " For pre-out LCR I measured and adjust to >1,4 V to match CT4150 sensitivity 1,4V so I will get full power." In fact, you should not do it, the level trims are for balancing the levels between channels, again, you should not adjust them all to output 1.4V with MV=0 and if you do, then your channels output will no not be balanced. Instead, you need to adjust the level trims so that every channel will output the same SPL (75 dB would be a good number for this exercise) at the main mic/or spl meter position, but not necessarily (in fact not likely) the same output voltage. After adjusting the trims for each channel to achieve 75 dB SPL, you can go back and measure the pre out voltage. Don't be surprise to find that none of the channel will have pre out voltage greater than 0.1 to 0.2 V.

So to sum things up:

a) If you only want to balance the levels, there is no need to wear ear plugs and risk damaging something, -20 dBFS or even -30 dBFS should be all you need.

b) If you want to find out how close your AVR's output is to their rated output and/or whether is would exceed the minidsp's rated input, you can follow that minidsp instructions and use the very high -3 dBFS tone. Or you can use a -20 dBFS tone, measure the voltage and you can then project the voltage at 0 dBFS by calculations.

I sit about 3 meters from sub, 3 M from centre and 3,5 m from LR. I have not played with SPL requirements, only trying to get even level speaker to speaker running the AVR channel levels setting noise.
When you are ready to do that, you can do it by calculations, or use an online calculator.

To do calculations yourself, you can use the following website that has all the formula you need:
http://www.sengpielaudio.com/calculator-gainloss.htm
http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm

To do it the quick way by using a decent online peak spl calculator:
https://myhometheater.homestead.com/splcalculator.html

Yes, my minidsp2x4 bal is an older version with 0.9/2V in and fixed 2 V out.
In my opinion, if you are only using it to EQ the subs, you may be better off just let Audyssey do its job. I tried using the 2X4 HD with Audyssey but I found too little gain for all the trouble. If you use only the minidsp, and it is not even the HD version, I highly doubt you can get better result than Audyssey.

Again, sorry. The Jamo D500 are 89 dB/1 watt and 4 ohm. My sub driver are 89 dB and 4 ohm, not sure what the driver+ box are.
I commented on the D500 above, they are very nice speakers and you don't have to worry about clipping as long as you don't listen to near reference level. They can't play too loud anyway for your 3.5 meter distance. It would help a little if you set the crossover higher than the typically recommended 80 Hz.

The minidsp can be runned as unbalanced with the wiring on page 24 in manual:
H t t p : / / w w w.minidsp.com/images/documents/miniDSP%20Balanced%202x4%20and%20Kit%20-%20User%20Manual%20v2.2.pdf
As mentioned before, I read the manual so I know it can be do unbalanced. You have no choice anyway as your SR7009 doesn't have balanced outputs.

And as I understand by doing it this complex I´m not able to run Audyssey for peq since it might change all channel level setting. So just following some rule of thumb sound quite good.
That is correct, but in my opinion you can do better using Audyssey. Your AVR has the XT32 Sub EQHT version that can set the distance and levels very accurately. If you don't like the REQ effects, after running auto setup, you have the option to select L/R bypass, so that the EQ will not affect your stereo music enjoyment. Audyssey's Dynamic EQ feature is quite good for low level listening.

This is the rule of thumb I guess for you experiences. So you set the power amp gain on ~70%. Are you also setting ~70 % in MiniDSP software for sensitivity and output?
PENG do you have any input?
Mr. M Code has a lot of experience in all sorts of audio gear, but I think he might not have read all the related into for your setup. 70% of the maximum adjustment is a good starting point for reasons he mentioned, but your 125 W rated CT4150 is only marginally adequate for your speakers and seating distance Its sensitivity of 1.4 V is not that high to begin with, so I think you are going to end up setting those knobs very close to maximum. You can of course start from 70%.
 
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N

Niklasmagnus

Audiophyte
Not sure what you are asking, is it still about clipping concern? The Jamo D500 LCR's sensitivity is 89 dB/2.83V/1M, and impedance is 4 ohms. If so, yes you need to be careful if you want to stay clear of the clipping point of the pre out and the power amp for the following reasons.

If you sit 3.5 M from the LCR, you will need about 500 W to hit reference level 105 dB peak, with 1 speaker. The D500 is rated 150 W long term, 200 W short term, so yes you can forget about 105 dB (reference) spl.

The Crown CT4150 is rated 125 W/4 ohm. It should be fine if you are happy with not more than 100 dB peak, 80 dB average. The 100 dB peak/80 dB average estimated spl are based on my assumption that your speakers are placed near a wall, so they should be getting about 3 dB of room gain. For 2 speakers playing at the same time you can expect about 3 dB louder on average. Even 80 dB average is quite loud for most people.

As to clipping or not, assuming Crown audio's website is accurate about the gain of the CT4150, with voltage gain of 27 dB, to output 125 W/4 ohm, the input voltage (that is output from the AVR) would need to be about 1 V, so no worry about clipping at all!!

Caution: I would add that the voltage needed could be anywhere between about 1 V to 1.25 V. I am giving you a range because Crown audio is not consistent about the CT4150's gain/sensitivity specs. On the website they say it is 27 dB (that would obviously be the best case scenario),but on the cut sheet it shows 25 dB, yet in the manual it says 26 dB, what a mess!!.
.
So by running the LCR on the CT4150 I might get clipping due to the fact I´m under powered to meet THX ref?
But in paragraph 4 you write I should not worry about clipping. Sorry Im not following.


Would it be a better choice to run LCR on SR7009 and run the surrounds on CT4150.
I use JMLAB/ Focal SIB as surround: 2 pcs in parallel on each channel. 7.1 system.

SIB Spec: Sensibilité (2,83 V/1 m) 90 dB. Impédance nominale 8 ohms
SR7009 spec:
number of poweramps9
Power Output (6 ohm, 1 kHz, 1% 1ch Drive)200 W
Utgångseffekt (6 ohm, 1 kHz, 0.7% 2-kanalsdrift)165 W
Utgångseffekt (8 ohm, 20 Hz - 20 kHz, 0.08% 2-kanalsdrift)125 W
70% garanti


If running LCR on CT4150 I might need to increase the trim gain on amp to or close to max.

I read that linked applications note. They suggested -3 dBFS because a) that is the maximum REW can do, and more importantly b) they want to make sure even at that high SPL, the AVR's pre out voltage does not exceed the minidsp's rated input voltage. There is no need to " For pre-out LCR I measured and adjust to >1,4 V to match CT4150 sensitivity 1,4V so I will get full power." In fact, you should not do it, the level trims are for balancing the levels between channels, again, you should not adjust them all to output 1.4V with MV=0 and if you do, then your channels output will no not be balanced. Instead, you need to adjust the level trims so that every channel will output the same SPL (75 dB would be a good number for this exercise) at the main mic/or spl meter position, but not necessarily (in fact not likely) the same output voltage. After adjusting the trims for each channel to achieve 75 dB SPL, you can go back and measure the pre out voltage. Don't be surprise to find that none of the channel will have pre out voltage greater than 0.1 to 0.2 V.

So to sum things up:

a) If you only want to balance the levels, there is no need to wear ear plugs and risk damaging something, -20 dBFS or even -30 dBFS should be all you need.

b) If you want to find out how close your AVR's output is to their rated output and/or whether is would exceed the minidsp's rated input, you can follow that minidsp instructions and use the very high -3 dBFS tone. Or you can use a -20 dBFS tone, measure the voltage and you can then project the voltage at 0 dBFS by calculations.
- Okey so for the CT4150 I don´t need to do any measurements on the pre-out. Great.

- But for the connection to MiniDSP I´m still a bit confused. MiniDSP are claiming that the input signal can never be higher then 2 V (in my case since I have an older version), since the device will then clip the signal. If I understand the application note and step by step gudie, one should measure at -3 dBFS since it is absolute max level (not stated in gudie but as I understand it) that the AVR will ever send out on pre-outs? So in the extreme explosion hitting the THX ref roof AVR will still only send max 2V. (But it might be totally wrong on my end.) Please if you could tell me how to set up the connection AVR-Minidsp-CTs600 and how to configure.


When you are ready to do that, you can do it by calculations, or use an online calculator.

To do calculations yourself, you can use the following website that has all the formula you need:
To do it the quick way by using a decent online peak spl calculator:
Thanks for the links. The last one I already played with =)

In my opinion, if you are only using it to EQ the subs, you may be better off just let Audyssey do its job. I tried using the 2X4 HD with Audyssey but I found too little gain for all the trouble. If you use only the minidsp, and it is not even the HD version, I highly doubt you can get better result than Audyssey.
In the future I plan to run them on separate channels. Been looking at the Behringer nx4-6000 to replace the CTs600. And then I will need the delay feature in Minidsp.
I also have an active HP-filter at 18 Hz to protect the drivers at the moments. They have limited liner movement.


I commented on the D500 above, they are very nice speakers and you don't have to worry about clipping as long as you don't listen to near reference level. They can't play too loud anyway for your 3.5 meter distance. It would help a little if you set the crossover higher than the typically recommended 80 Hz.

That is correct, but in my opinion you can do better using Audyssey. Your AVR has the XT32 Sub EQHT version that can set the distance and levels very accurately. If you don't like the REQ effects, after running auto setup, you have the option to select L/R bypass, so that the EQ will not affect your stereo music enjoyment. Audyssey's Dynamic EQ feature is quite good for low level listening.

Mr. M Code has a lot of experience in all sorts of audio gear, but I think he might not have read all the related into for your setup. 70% of the maximum adjustment is a good starting point for reasons he mentioned, but your 125 W rated CT4150 is only marginally adequate for your speakers and seating distance Its sensitivity of 1.4 V is not that high to begin with, so I think you are going to end up setting those knobs very close to maximum. You can of course start from 70%.
I crossover at 100Hz today. It sound and measure the best. And will help getting it louder.

Dont have any experience with the Audyssey XT32 only the lover end version and it did not sound good. But will play with this one.

Thanks again.
 
P

PENG

Audioholic Overlord
So by running the LCR on the CT4150 I might get clipping due to the fact I´m under powered to meet THX ref?
But in paragraph 4 you write I should not worry about clipping. Sorry Im not following.
That is correct, the CT4150 does not have enough to power your speakers because you are sitting 3.5 meters from them and the specified impedance for those speakers is 4 ohms with sensitivity of 89 dB/2.83V/1m.

Note that the peak spl calculator I linked is based on sensitivity stated in dB SPL (1 W/1 M),so if you use that calculator to figure out the SPL, you need to either enter 125 W/2 = 62.5 W(CT4150),or enter 125 W but de-rate the D500"s specified sensitivity of 89 dB to 86 dB. So if you enter 125 W, 86 dB, 11.5 ft (3.5 meters),1 speaker near a wall, you get 99.1 dB. That's below THX standard of 85 dB average and 105 dB peak.

That is technically speaking, later on I did say "you don't have to worry about clipping as long as you don't listen to near reference level. They can't play too loud anyway for your 3.5 meter distance. It would help a little if you set the crossover higher than the typically recommended 80 Hz."

So that was conditional (noted highlighted part). I hope that is clear now.

Regarding you other questions, below are just my opinions:

1) Yes I would say the SR7009 is a better fit for the LCR because it is a little more powerful than the CT4150, especially for 4 ohm speakers. Below is a link to the SR7010 (SR7009 should do the same)'s bench test results:
https://www.soundandvision.com/content/marantz-sr7010-av-receiver-review-test-bench

2) The focal SIB has nominal impedance 8 ohms and they are not designed to take too much power anyway so again, yes I think the CT4150 can power them easily.

3) Actually the SIB has higher sensitivity too (90 dB/2.83V/1M),assuming the specs are accurate, if the distances are the same, you may have to lower the trim slightly to match the other LCR.

As I mention before, the LCR's 89 dB/2.83V/1M is equivalent to 86 dB/1W/1M because of the 4 ohm impedance. 2.83 V into 8 ohm is 1 W, but 2.83 V into 4 ohm is 2 W.

Not a good idea to run two of the SIBs in parallel because the impedance will be 4 ohms again. The CT4150 has 4 channels right, why not just use 1 channel for each of the 4 speakers?

4) If you want to measure the pre out voltage of the SR7009 for fun and satisfy your curiosity, then do it. I just don't see the purpose if you are not using it with the minidsp.

5) You misunderstood the minidsp's application notes as follow:
a) The -3 dBFS is the maximum level REW (no the AVR) tone generator can provide.
b) The AVR, in this case the SR7009 preout is not limited to "max 2V", it is rated 1.2 V, without stating the conditions so we have no idea exactly what Marantz meant, but we could guess. The maximum pre out voltage would likely be limited by the rail voltage of the power supply for the preamp section, and the preamp/volume control IC. Based on a few past bench test results on the pre outs by Audioholics.com on some older Marantz and Denon units, my best guess is that it could be anywhere between 2.5 to 4 V at clipping.

6) Your minidsp's input is rated 2V, it does not mean it will get damaged as soon as the SR7009 preout exceeds 2V. It most likely means either it (the minidsp) will only sustain damage if over driven continuously but not if for short term such as the extreme explosion you referred to, or its output will start to clip/distort, or both. So I think 2 V is fine for normal use, but not if the user abuse the system, such as pushing the AVR, amps and speakers to or pass their limits, but again that's just my educated guess. You should email minidsp your questions if you want to know for sure.

7) To set up the connection/configure, you should just follow the steps given in that application note. In my opinion (sorry for repeating),given what you have in your setup, it is better to simply use Audyssey to setup your subs, and sell the minidsp to others who may have good use for it.
 
Last edited:
N

Niklasmagnus

Audiophyte
That is correct, the CT4150 does not have enough to power your speakers because you are sitting 3.5 meters from them and the specified impedance for those speakers is 4 ohms with sensitivity of 89 dB/2.83V/1m.

Note that the peak spl calculator I linked is based on sensitivity stated in dB SPL (1 W/1 M),so if you use that calculator to figure out the SPL, you need to either enter 125 W/2 = 62.5 W(CT4150),or enter 125 W but de-rate the D500"s specified sensitivity of 89 dB to 86 dB. So if you enter 125 W, 86 dB, 11.5 ft (3.5 meters),1 speaker near a wall, you get 99.1 dB. That's below THX standard of 85 dB average and 105 dB peak.

That is technically speaking, later on I did say "you don't have to worry about clipping as long as you don't listen to near reference level. They can't play too loud anyway for your 3.5 meter distance. It would help a little if you set the crossover higher than the typically recommended 80 Hz."

So that was conditional (noted highlighted part). I hope that is clear now.

Regarding you other questions, below are just my opinions:
Thanks now that is clear. Good explanation.

1) Yes I would say the SR7009 is a better fit for the LCR because it is a little more powerful than the CT4150, especially for 4 ohm speakers. Below is a link to the SR7010 (SR7009 should do the same)'s bench test results:
https://www.soundandvision.com/content/marantz-sr7010-av-receiver-review-test-bench
Then I will run LCR on SR7009 since it have a bit more power.

2) The focal SIB has nominal impedance 8 ohms and they are not designed to take too much power anyway so again, yes I think the CT4150 can power them easily.

3) Actually the SIB has higher sensitivity too (90 dB/2.83V/1M),assuming the specs are accurate, if the distances are the same, you may have to lower the trim slightly to match the other LCR.

As I mention before, the LCR's 89 dB/2.83V/1M is equivalent to 86 dB/1W/1M because of the 4 ohm impedance. 2.83 V into 8 ohm is 1 W, but 2.83 V into 4 ohm is 2 W.

Not a good idea to run two of the SIBs in parallel because the impedance will be 4 ohms again. The CT4150 has 4 channels right, why not just use 1 channel for each of the 4 speakers?
Sorry, I mean that I use 8 pcs SIB for surround, and they are in parallel connected tor the 7.1 setup. But might it be better to do series connection to get 16 ohm?

I checked the SPL Calculator and they should do fine running on the CT4150 since they are much closer to listening position, about 5-6 feet. They will do 110 dB SPL so I must reduce the trim/gain a bit. Actuality I have reduced max in AVR now for them to play a equal level as LCR.


4) If you want to measure the pre out voltage of the SR7009 for fun and satisfy your curiosity, then do it. I just don't see the purpose if you are not using it with the minidsp.

5) You misunderstood the minidsp's application notes as follow:
a) The -3 dBFS is the maximum level REW (no the AVR) tone generator can provide.
b) The AVR, in this case the SR7009 preout is not limited to "max 2V", it is rated 1.2 V, without stating the conditions so we have no idea exactly what Marantz meant, but we could guess. The maximum pre out voltage would likely be limited by the rail voltage of the power supply for the preamp section, and the preamp/volume control IC. Based on a few past bench test results on the pre outs by Audioholics.com on some older Marantz and Denon units, my best guess is that it could be anywhere between 2.5 to 4 V at clipping.

6) Your minidsp's input is rated 2V, it does not mean it will get damaged as soon as the SR7009 preout exceeds 2V. It most likely means either it (the minidsp) will only sustain damage if over driven continuously but not if for short term such as the extreme explosion you referred to, or its output will start to clip/distort, or both. So I think 2 V is fine for normal use, but not if the user abuse the system, such as pushing the AVR, amps and speakers to or pass their limits, but again that's just my educated guess. You should email minidsp your questions if you want to know for sure.
Now it starts to clear for me. To bad Minidsp has written the note in such definitive way, but I guess they are protection there back. I will just forget about this measuring pre-out SUB and use my time on watching movies instead =).


7) To set up the connection/configure, you should just follow the steps given in that application note. In my opinion (sorry for repeating),given what you have in your setup, it is better to simply use Audyssey to setup your subs, and sell the minidsp to others who may have good use for it.
As long as I dont have the two missing power channels for run all subs individually I might try to skip the minidsp. But it fills good to have the HP filter at 18 Hz. Will check if Audyssey can do something similar.
 
P

PENG

Audioholic Overlord
As long as I dont have the two missing power channels for run all subs individually I might try to skip the minidsp. But it fills good to have the HP filter at 18 Hz. Will check if Audyssey can do something similar.
If I remember right, the SR7009 has two subwoofer outputs. To feed 4 subs, you can use a Y splitter so each sub out can feed two. There is no need to use any filtering on the sub, in fact Audyssey suggests you disable such filters.

Audyssey uses IIR filters. minidsp, if use with REW, you would basically use PEQ (parametric) filters that are IIR type, though you can use it with Dirac Live, that uses mixed-phase filtering that basically uses a combination of IIR and FIR filters.

You can get better results if you use REW/minidsp with Audyssey, but as I mentioned before, I tried that and gave up after realizing the very little improvement was not worth the extra wiring, and I doubt I could hear any difference anyway. Besides, I had the minidsp 2X4 HD, with your non HD version I really don't believe it worth doing it at all. Since you have everything you need, you should just try it and see if you can hear a difference. It is your money, time and only you can decide.

Some interesting reads for you, if you haven't already:

https://www.minidsp.com/applications/dsp-basics/fir-vs-iir-filtering
https://www.minidsp.com/applications/digital-room-correction/dirac-live-vs-rew
https://audyssey.zendesk.com/hc/en-us/articles/212347763-MultEQ-vs-other-equalization-methods-

"Audyssey LabsJuly 15, 2010 16:53
There are two fundamental differences from every other method available in AV receivers today. The first is that MultEQ is not based on parametric equalization. Parametric equalization relies on a few bands that are centered at certain frequencies. These bands do not provide sufficient resolution to address many room acoustical problems. Also, parametric bands tend to interact so that changes at one frequency have undesirable results at nearby frequencies. Moreover, parametric equalization methods use a particular type of digital filter called Infinite Impulse Response (IIR) that only attempts to correct the magnitude response in the frequency domain. These filters can cause unwanted effects, such as ringing or smearing, in the time domain particularly as the bands get narrower. MultEQ uses Finite Impulse Response (FIR) filters for equalization that use several hundred coefficients to achieve much higher resolution in the frequency domain than parametric bands. Furthermore, by their nature, FIR filters simultaneously provide correction in the frequency and time domains. FIR filters had been considered to require too many computational resources. But Audyssey solved this problem by using a special frequency scale that allocates more power to the lower frequencies where it is needed the most."
 
B

Bpadilla96

Audiophyte
Hello Gene, I recently purchased an axiom ADA 1500 amplifier. When connected the amplifier my speaker level went down in sound level tremendously. I used to run Barringer‘s receivers but distorted. I have a Denon 4200 W receiver. My question is does the receiver would support The amplifier in terms of sensitivity voltage. The amplifier voltage sensitivity is 2 V my Denon is 1.2 bolts read it. My current home theater is axiom. The reason I bought the amplifier is because I run four ohms speakers front stage so the amp is three it is three channels However I feel I am not getting the full power out of it. My speakers are the M100 towers and center the vp180. My main question is whether I have the correct receiver. I’m a little lost, I was expecting a gain performance and I got the total opposite. Please if you give me some advice on sensitivity values and what are you suggestions I hate to spend money not buying the correctEquipment. The denon allows me to assign two pre channels in this case land right. The center channel isn’t an option. I have been having to bump up the decibel on the c channel to compensate. Not really sure. Thanks so much.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Hello Gene, I recently purchased an axiom ADA 1500 amplifier. When connected the amplifier my speaker level went down in sound level tremendously. I used to run Barringer‘s receivers but distorted. I have a Denon 4200 W receiver. My question is does the receiver would support The amplifier in terms of sensitivity voltage. The amplifier voltage sensitivity is 2 V my Denon is 1.2 bolts read it. My current home theater is axiom. The reason I bought the amplifier is because I run four ohms speakers front stage so the amp is three it is three channels However I feel I am not getting the full power out of it. My speakers are the M100 towers and center the vp180. My main question is whether I have the correct receiver. I’m a little lost, I was expecting a gain performance and I got the total opposite. Please if you give me some advice on sensitivity values and what are you suggestions I hate to spend money not buying the correctEquipment. The denon allows me to assign two pre channels in this case land right. The center channel isn’t an option. I have been having to bump up the decibel on the c channel to compensate. Not really sure. Thanks so much.
Your problem is that you have a receiver with domestic line level out and an amp with professional line level in. There may also be an impedance miss match but these are not specified.

I'm pretty sure that Axiom amp just floated the RCA inputs to the balanced inputs with no added gain. That was a mistake, but it's cheap.

So what you need is a domestic to professional line level converter.

This one will do the trick for you.
 
B

Bpadilla96

Audiophyte
Thanks something to try never seen the gadget before. One thing I read on the amp manual was not to use and rca cable that has one end rca and the other xlr. That is what I have. Says to use both with same ends. In my case both rca. Thanks for the link. It is a three channel amp. Would the box work for all three or how does it work. I am not too familiar with it. I really appreciate your help!!!!
 
B

Bpadilla96

Audiophyte
I forgot to mention that the amp came with rca connection option. something I have not tried. I would let you know. Thanks again. .
 
everettT

everettT

Audioholic Ninja
I forgot to mention that the amp came with rca connection option. something I have not tried. I would let you know. Thanks again. .
As TLS mentioned, the xlr inputs are probably a different sensitivity. You should use the RCA. Also did you re-run Audyessey? Also you should switch back to the 8ohm setting.
 
TLS Guy

TLS Guy

Audioholic Slumlord
I forgot to mention that the amp came with rca connection option. something I have not tried. I would let you know. Thanks again. .
I would try going RCA to RCA. However the amp does not specify a different sensitivity for the RCA and XLR. If you have the same problem going RCA to RCA then you will need two of the devices I linked you to. From the spec sheet I suspect you will need two domestic to professional line level converters.
 

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