Need expert advice if an external Amp will improve my system?

[Bin]

I have been researching for a while now regarding speaker sensitivity particularly on 1 watt/1 meter calculation.
Based on all my calculation, i think the current AVR is able to produce the LOUDNESS based on my listening level and distance.

Here's the content used :

• AVR Yamaha TSR7810 (95wcp on 2 channels)
• 3.2 HT System
  • a pair of Polk LSIM 707 (88db @ 1 watt/1 meter, can take up to 300 watts)
  • center Polk LSIM 706c (88db @ 1 watt/1 meter, can take up to 250 watts)
  • a pair of SVS PB1000
• Sitting Distance : 3.1 meters from HT System
• Listening volume : -40db to -20db on AVR volume

As you can see, my AVR isn't anything top tier specs.
However based on my sitting distance and listening level, I think i am only using no more than 30watts from the AVR based on my calculation.

I have seen many people adding external power amp to their system, and their sitting distance and listening level is very similar to mine.
I don't think i need LOUDNESS anymore since my AVR is handling that, but my question is......will adding external amp to my system help to improve the SOUND QUALITY such as dynamics?
If the answer is NO, then i will save up my money .

 

[NINaudio]

I don't think i need LOUDNESS anymore since my AVR is handling that, but my question is......will adding external amp to my system help to improve the SOUND QUALITY such as dynamics?
If the answer is NO, then i will save up my money .

No, it will not. Save your money for a different upgrade

 

[AcuDefTechGuy]

Save your money.

 

[PENG]

• Listening volume : -40db to -20db on AVR volume

I don't think i need LOUDNESS anymore since my AVR is handling that, but my question is......will adding external amp to my system help to improve the SOUND QUALITY such as dynamics?
If the answer is NO, then i will save up my money .

Agreed with what's been said. To play it safe, you should invest $20 to on a couple of those Infinity fans. Put them on top of the unit, set both the lowest speed so you don't hear the fan noise from you seat, and your AVR will thank you and live longer.

Those speakers likely have impedance dips to about 3 to 4 ohms and not too friendly phase angles in the 80 to 130 Hz range so setting XO to 100 Hz should help too. Listening volume is -40 to -20 is great, as song that's for things like BR movies. If you have the vol at -20 and watch something on YouTube then you have to be careful because some contents were recorded at very high level. The sad truth a lot of people don't realize is that a 200 W external amp would only increase sound pressure level by about 3 dB. Two fans are much cheaper than a 200 WPC amp.

 

[Bin]

Thanks to everyone's who provided your feedback, I am saving my money then .

I just played around with different XO on my speakers and finally after wife approval, my towers are set up 60Hz and center is set to 80Hz.

I don't think there's anything that I need invest now in the system I am playing, except maybe to upgrade my AVR and bigger subs maybe

 

[PENG]

Thanks to everyone's who provided your feedback, I am saving my money then .

I just played around with different XO on my speakers and finally after wife approval, my towers are set up 60Hz and center is set to 80Hz.

I don't think there's anything that I need invest now in the system I am playing, except maybe to upgrade my AVR and bigger subs maybe

Good for you, but as I alluded to earlier, your little receiver may thank you if you set the crossover to at least 90 Hz, 100 Hz much preferred. It think it is reasonable to assume the LSiM707 has impedance/phase angle vs frequency worse than the 703's show below, measured by Stereophile.

You have two PB1000, they can do a better job producing everything below 120 Hz than those 6X9" elliptical woofers in the 707s. You won't lose any base, in fact you will most likely end up with better looking bass response. At last try it..

Polk LSiM703 loudspeaker Measurements

Sidebar 3: Measurements I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Polk LSiM703's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield and spatially averaged room responses. With its ¼" capsule, the Earthworks mike is small enough...

www.stereophile.com

You can see, there are bad combinations of low impedance and high phase angles in the area between about 75 to 130 Hz, and again, the 707's are likely worse.

 

[Out-Of-Phase]

Bin, my signature is screaming at you.

 

[Bin]

Thanks @PENG , I did a re-calibration today after getting your feedback and also consulted SVS tech.
Apparently, my subs gain was set to about 4oclock position, and AVR volume was set to -6db, which cause some boominess (if that's a word) in some of song tracks i played.

Adjustment made :

• Change subs gain to 2 oclock and rerun YPAO
• Now subs AVR volume auto calibrated to -1.5db (I left it be)
• XO towers to 90hz
• XO center to 80hz

So far, i think i got more clarity on higher frequency sound from the speakers and better bass separation to the subs. I will need to continue to tweak around to 100hz and see if i like it (or my wife likes it ).

By the way Peng, you mentioned that my AVR will love it if i set the XO to higher freq. Why is that so? Is it because the towers won't require as much power at XO than lower?

 

[lovinthehd]

I can't understand why the gain difference would cause boominess. Change in crossover, perhaps.

 

[Bin]

Maybe u r right @lovinthehd , but after I made those changes, at least that's what I notice immediately .

 

[lovinthehd]

Maybe u r right @lovinthehd , but after I made those changes, at least that's what I notice immediately .

Could simply be the different YPAO run and resultant settings as a whole, as they do differ at least a bit from run to run. Sonic memory with a YPAO run in between isn't all that exact either....

 

[ryanosaur]

Those Polks are definitely not friendly speakers for an average AVR. I concur with a good active cooling solution.

Indeed, think of the higher XO as taking the energy draw away from the worst of the speakers behavior (simplistic, but mostly accurate).

As far as the Sub Gain... the higher the gain, the more likely you are introducing distortion in the sub... so boominess (perhaps), or other distortion phenomena are more likely.
You didn't discuss your room size which makes me question the efficacy of the PB1000s. At SVS's smallest sub, those are best suited to Closed Rooms less than 3000'3... preferably probably less than 2000'3 for best performance. On the other hand, the AVR Trim is still in the negative, if only slightly.

 

[lovinthehd]

Those Polks are definitely not friendly speakers for an average AVR. I concur with a good active cooling solution.

Indeed, think of the higher XO as taking the energy draw away from the worst of the speakers behavior (simplistic, but mostly accurate).

As far as the Sub Gain... the higher the gain, the more likely you are introducing distortion in the sub... so boominess (perhaps), or other distortion phenomena are more likely.
You didn't discuss your room size which makes me question the efficacy of the PB1000s. At SVS's smallest sub, those are best suited to Closed Rooms less than 3000'3... preferably probably less than 2000'3 for best performance. On the other hand, the AVR Trim is still in the negative, if only slightly.

If the pre-out level is clean and matched to the gain level on the sub it shouldn't stress out the amp any more, whether that particular matching gain setting is relatively high or low in its range. With a low enough signal full gain on the sub amp shouldn't be an issue. I'd assume since YPAO is balancing that point, the pre-out level to the sub's gain setting, it should be relatively equal in this case.

 

[PENG]

By the way Peng, you mentioned that my AVR will love it if i set the XO to higher freq. Why is that so? Is it because the towers won't require as much power at XO than lower?

You got it, but it wouldn't make much difference if you listen loud like it is in a movie cinema. If you look at the graph I posted earlier, it is for the LSiM703 but the 707 should be similar if not worse. The solid line is the impedance and the dotted line is the phase angle between the voltage and current, both varies with frequency. You can see that in the range from about 75 to 130 Hz the impedance is quite low.

Obviously you don't want to set XO as higher as 130 Hz, but if you set it to 90 Hz, it would still be able to avoid some of the impedance dips an the relatively large phase angles. So basically XO of 90 or 100 Hz are good numbers for you situation, given that you do have a pair of subwoofers.

Your AVR is rated for 8 ohms, the lower the speaker's impedance mean the more current the AVR has to deliver. For example, at 4 ohms, the AVR would have to deliver twice as much current at the same volume position, so if you set the crossover higher, by avoiding some of those low impedance points, the AVR will not have to work as hard.

Phase angle can also be an issue for the entry level AVRs, the higher the phase angle, the more power will have to be dissipated in the output transistors and that could cause them to overheat and may shutdown if the protection system works well, or the transistors may be damaged.

The reason I bring this up is that those LSIM speakers are not easy loads because of their design that resulted in relatively low impedance and high phase angles in the low to lower mid bass range (fortunately the phase angle is high for a very narrow range). They were advertised as 8 ohm nominal speakers, but they are more like 4 ohm, or 6 ohm nominal at best.

I bet if you ask @TLS Guy , I am sure he will also tell you don't believe Polk's impedance specs for those speakers. Again, if you can in fact keep the volume at or below -20, you should be fine but don't forget to put a couple of fans on top anyway for longevity.

 

[ryanosaur]

Not a pretty picture. Anything Low-Frequency near a 45º Phase is creating heat. Lot's of heat, which then must be dissipated. This is it, here:

The LSiM707’s listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +1.05/–1.73 decibels from 200 hertz to 10 kilohertz. The –3dB point is at 34 Hz, and the –6dB point is at 30 Hz. Impedance reaches a minimum of 3.75 ohms at 66 Hz and a phase angle of –47.96 degrees at 83 Hz.

Polk LSiM707 Surround Speaker System HT Labs Measures

HT Labs Measures L/R Sensitivity: 88.5 dB from 500 Hz to 2 kHz Center Sensitivity: 90 dB from 500 Hz to 2 kHz Surround Sensitivity: 88.5 dB from 500 Hz to 2 kHz This graph shows the quasi-anechoic (employing close-miking of all woofers) frequency response of the LSiM707 L/R (purple trace)...

www.soundandvision.com

 

[Bin]

Thanks guys, looks like it's my low end AVR is the bottleneck .

Anyway, thanks to you guys advices, i have bought this fan to help with cooling.
Infinity Fan

 

[Bin]

@ryanosaur , my living room size is approx 22ft L X 11ft W (with high ceiling) .

And living room isn't a close room, it has an L shape to the left side.

 

[Pogre]

You got it, but it wouldn't make much difference if you listen loud like it is in a movie cinema. If you look at the graph I posted earlier, it is for the LSiM703 but the 707 should be similar if not worse. The solid line is the impedance and the dotted line is the phase angle between the voltage and current, both varies with frequency. You can see that in the range from about 75 to 130 Hz the impedance is quite low.

Obviously you don't want to set XO as higher as 130 Hz, but if you set it to 90 Hz, it would still be able to avoid some of the impedance dips an the relatively large phase angles. So basically XO of 90 or 100 Hz are good numbers for you situation, given that you do have a pair of subwoofers.

Your AVR is rated for 8 ohms, the lower the speaker's impedance mean the more current the AVR has to deliver. For example, at 4 ohms, the AVR would have to deliver twice as much current at the same volume position, so if you set the crossover higher, by avoiding some of those low impedance points, the AVR will not have to work as hard.

Phase angle can also be an issue for the entry level AVRs, the higher the phase angle, the more power will have to be dissipated in the output transistors and that could cause them to overheat and may shutdown if the protection system works well, or the transistors may be damaged.

The reason I bring this up is that those LSIM speakers are not easy loads because of their design that resulted in relatively low impedance and high phase angles in the low to lower mid bass range (fortunately the phase angle is high for a very narrow range). They were advertised as 8 ohm nominal speakers, but they are more like 4 ohm, or 6 ohm nominal at best.

I bet if you ask @TLS Guy , I am sure he will also tell you don't believe Polk's impedance specs for those speakers. Again, if you can in fact keep the volume at or below -20, you should be fine but don't forget to put a couple of fans on top anyway for longevity.

Uh oh... you summoned TLS Guy in a LSiM thread...

 

[ryanosaur]

@ryanosaur , my living room size is approx 22ft L X 11ft W (with high ceiling) .

And living room isn't a close room, it has an L shape to the left side.

Ok... so closed room volume assuming an 8' ceiling is already ~2000'3.

I would task you with estimating your total open room volume, if you were game for such a venture.
Break it into smaller spaces if it makes things easier, then add them all together.

Cross reference your final open room volume against the Bassaholic Room Size ratings.

Bassaholic Subwoofer Room Size Rating Protocol

This article outlines our test procedure in determining a subwoofers room size recommendation based on its max CEA SPL output while making room size and subwoofer distance assumptions.

www.audioholics.com

Mind... you do not have to pressurize the whole space, however, proper woofage can be a boon to your entire system performance.

 

[ryanosaur]

Uh oh... you summoned TLS Guy in a LSiM thread...

This!

It's like candyman-ing in one mirror, then turning around and bloodymary-ing in another mirror!


If the AVR doesn't get you, the Speaker will!

Boo!