Thoughts on MCACC Pro.

[Jay aLBERS]

A couple of questions for the audio gurus here.
I recently bit the bullet and upgraded to a surround processor that has room correction. The system it uses is the MCACC Pro. After doing the calibration I was shocked when I looked at the resulting settings.
The front three channels were all set at -12db. The rears were set at -3db
and the rear surrounds were set at -3.5db.The sub channels were both set to-4db.This after it kept telling me to turn the sub down. I ended up at 1/2 gain on the sub amp. The EQ looked really random, but fairly flat. It is my understanding that this set up should put the "reference" level of 0 on the system main volume to be the same as what the soundtrack would sound like in the theater? What would you change for listening to music? Would you bump the levels back up. Or just leave it alone. I have contemplated copying the MCACC settings and setting the gains all back to 0 and leaving the EQ,Standing Wave and all the other settings alone. The room is wrapped in sound absorbing material and it sounds fantastic. It just bugs me that I have all this unused power with the levels all set so low. Thanks for any input you might have.

 

[PENG]

There could be several reasons such as:

- The NAD 7600 and 2600 bridged will result in 6 dB higher gain.
- The Klipsch speakers you have are very sensitive.
- You may not have follow Pioneer instruction exactly, to the letter when you ran MCACC.

I suggest you try running MCACC again after carefully reading the instruction and follow it exactly. How you position your Mic could have a major impact.

After that, I think you should just trust the software. To get the front 3 channel levels closer to 0, I strongly suggest you "unbridge" the NAD amps. With your highly sensitive speakers, bridging offers no advantages, it is probably doing more harm than good.

 

[Jay aLBERS]

I did the calibration when I was home alone. Turned off the hvac had the microphone on a very nice tripod. The house was quiet, and I did the calibration twice and compared the numbers. They were almost identical. You mention unbridging the front three amps. I have always wondered if I should bi-amp the front three speakers. How do you feel about putting a splitter on the interconnects to get both channels active and then bi-amping? Also please explain" doing more harm than good".
And thanks for your reply.

 

[lsiberian]

It might be that for one source and a different volume for another source.

 

[PENG]

I did the calibration when I was home alone. Turned off the hvac had the microphone on a very nice tripod. The house was quiet, and I did the calibration twice and compared the numbers. They were almost identical. You mention unbridging the front three amps. I have always wondered if I should bi-amp the front three speakers. How do you feel about putting a splitter on the interconnects to get both channels active and then bi-amping? Also please explain" doing more harm than good".
And thanks for your reply.

Okay, assuming your calibration is good then the main reasons are:

- the amp bridging that resulted in 6dB higher gain so MCACC has to lower the level to compensate for it and to match the surround channels. It is just doing it's job.

- The Klipsch speakers have very high gains, especially the Cornwalls. Again MCACC is doing it's job to try and strike a balance, hence lowering the levels especially the subwoofer's.

If you insist on using both amps, and if the speakers are designed for biamping, then you can do it and it should in theory offer some improvements.

"Doing more harm than good", I meant in terms of signal to noise ratio. The higher gain will in theory result in a higher noise floor. In terms of distortions, it is hard to say because it would also depend on the speaker's impedance characteristics.

If you give us bridging, whether you biamp the front L/R or not, run MCACC again, I am quite sure the level settings will be more in line to what you expected.

 

[Jay aLBERS]

Let me ask this question in a more intelligent way.
If I copy the MCACC setting to a different profile and change the channel gain settings does this negate the adjustments for phase correction, and standing wave correction?

 

[lsiberian]

Let me ask this question in a more intelligent way.
If I copy the MCACC setting to a different profile and change the channel gain settings does this negate the adjustments for phase correction, and standing wave correction?

It shouldn't have any impact on phase correction. Gain is the amplitude of the waves not the timing.

 

[gene]

the reason the sub level is set so low is b/c you have the gain set too high on the sub. Lower the gain on the sub, rerun the calibration and you will see the levels will go up. This will also increase sensitivity on the sub auto on/off circuit so you don't have to blast the levels to get it to activate for night viewing.

Either way you aren't losing power as you likely have plenty of gain left in the master volume to reach full scale even if its not at the 0dB reference setting.

 

[Jay aLBERS]

the reason the sub level is set so low is b/c you have the gain set too high on the sub. Lower the gain on the sub, rerun the calibration and you will see the levels will go up. This will also increase sensitivity on the sub auto on/off circuit so you don't have to blast the levels to get it to activate for night viewing.

Either way you aren't losing power as you likely have plenty of gain left in the master volume to reach full scale even if its not at the 0dB reference setting.

During the calibration process the system would ping the subs and a prompt would come up that the sub was too loud. so I turned it down several times, until I didn't get the prompt to turn it down. I ended up at 1/2 gain on the sub amp. I have come to the realization that I just have too much power. Or More than enough power pushing my system.The front 3 amps are each rated at 500 RMS with 4.5db of headroom. The sub amp is 600x2 .The 0db setting is pretty loud with all the gains turned down. I was going to check it a little bit ago but the battery in my meter was dead. I'm on my way home with a fresh battery. I will post db's at reference here in a little bit.

 

[WaynePflughaupt]

Yes, you are drastically over-powered. You could probably drive those speakers to ear-bleeding levels with a mere 50 watts, if that much. Your Pioneer receiver could drive them all without breaking a sweat.

Regards,
Wayne A. Pflughaupt

 

[PENG]

During the calibration process the system would ping the subs and a prompt would come up that the sub was too loud. so I turned it down several times, until I didn't get the prompt to turn it down. I ended up at 1/2 gain on the sub amp. I have come to the realization that I just have too much power. Or More than enough power pushing my system.The front 3 amps are each rated at 500 RMS with 4.5db of headroom. The sub amp is 600x2 .The 0db setting is pretty loud with all the gains turned down. I was going to check it a little bit ago but the battery in my meter was dead. I'm on my way home with a fresh battery. I will post db's at reference here in a little bit.

Have you "unbridged" your NAD 7600 and 2600 yet? As I mentioned, by having them bridged for the front and centre, those 3 channels will have 6 dB gain higher than the surround channel. Also the front Cornwalls are several dB more sensitive than your surround speakers. Those two reasons can easily explain why your AVR set levels of the front 3 almost 9 dB lower than that for the surrounds channels.

There is no getting around, either you live with the -12 dB setting for the front 3, or do not use the bridge mode on the NAD 7600 and NAD 2600 amp. With those super sensitive/efficient Klipsch speaker, why do you bridge the amp? I have to ask again because I am a curious person.

 

[Jay aLBERS]

Have you "unbridle" your NAD 7600 and 2600 yet? As I mentioned, by having them bridged for the front and centre, those 3 channels will have 6 dB gain higher than the surround channel. Also the front Cornwalls are several dB more sensitive than your surround speakers. Those two reasons can easily explain why your AVR set levels of the front 3 almost 9 dB lower than that for the surrounds channels.

There is no getting around, either you live with the -12 dB setting for the front 3, or do not use the bridge mode on the NAD 7600 and NAD 2600 amp. With those super sensitive/efficient Klipsch speaker, why do you bridge the amp? I have to ask again because I am a curious person.

No not yet. I did put a sound meter on the system tonight. I listened to Dark Side of the Moon on SACD and a bunch of other multichannel material. The system at the calibration point averaged 105db at 0DB on the main volume. Peaks were in the 116 to 118 range with the meter pointed to the front of the room. With the meter pointed to the rear it was down about 2db. With the peaks about 3 db less.With the meter pointed to either side it was about the same as the rears.
Why bridge? You ask? I have always been of the mindset that if the amps NEVER struggle they will sound better. I have over the years let the smoke out of a couple of the drivers, but it was always my fault.
That and I like it loud, I guess....Plus I like the way the equipment looks.

 

[gene]

During the calibration process the system would ping the subs and a prompt would come up that the sub was too loud. so I turned it down several times, until I didn't get the prompt to turn it down. I ended up at 1/2 gain on the sub amp. I have come to the realization that I just have too much power. Or More than enough power pushing my system.The front 3 amps are each rated at 500 RMS with 4.5db of headroom. The sub amp is 600x2 .The 0db setting is pretty loud with all the gains turned down. I was going to check it a little bit ago but the battery in my meter was dead. I'm on my way home with a fresh battery. I will post db's at reference here in a little bit.

Don't worry about volume level position. Your sub preamp likely has a lot of voltage gain. Turn it down below 1/2 and recalibrate.

 

[PENG]

No not yet. I did put a sound meter on the system tonight. I listened to Dark Side of the Moon on SACD and a bunch of other multichannel material. The system at the calibration point averaged 105db at 0DB on the main volume. Peaks were in the 116 to 118 range with the meter pointed to the front of the room. With the meter pointed to the rear it was down about 2db. With the peaks about 3 db less.With the meter pointed to either side it was about the same as the rears.
Why bridge? You ask? I have always been of the mindset that if the amps NEVER struggle they will sound better. I have over the years let the smoke out of a couple of the drivers, but it was always my fault.
That and I like it loud, I guess....Plus I like the way the equipment looks.

Without bridging, if you sit 4 meters from the speakers you can still hit 116 db peak without stressing the 7600. 100 db average is really too loud and could cause hearing loss. Bridging is also not a good idea if your speaker has low impedance dips. Do you have the impedance curves for the Cornwall's?

 

[Jay aLBERS]

Without bridging, if you sit 4 meters from the speakers you can still hit 116 db peak without stressing the 7600. 100 db average is really too loud and could cause hearing loss. Bridging is also not a good idea if your speaker has low impedance dips. Do you have the impedance curves for the Cornwall's?

I don't have the curves but if remember correctly they don't dip much below 3.8. Also the NAD's have a low impedance switch for the bridged mode. Keep in mind that I have been running this set up for years. I just recently added the Pioneer in place of an NAD T-163 that offered no room correction. As far as the 100 db goes, it doesn't seam overly loud to me, but on the other hand my boat stereo does 135's....

 

[PENG]

I don't have the curves but if remember correctly they don't dip much below 3.8. Also the NAD's have a low impedance switch for the bridged mode. Keep in mind that I have been running this set up for years. I just recently added the Pioneer in place of an NAD T-163 that offered no room correction. As far as the 100 db goes, it doesn't seam overly loud to me, but on the other hand my boat stereo does 135's....

I was thinking that too, that you have it for so long so the risk of damaging anything is very low indeed. Just keep in mind though, at least in theory the potentially much high voltage capability of the bridged amps represent a high risk when driving low impedance. The newer NAD gear likely have advanced protective circuits built in but the older one probably just rely on the sort of low impedance switch that would simply lower the maximum rail voltage and that would effectively negate the effect of bridging. Anyway, sound like you have nothing to worry about and can just enjoy your nice set up. I still think you should not listen anywhere near 100 dB SPL for long duration, a few minutes won't do much harm but not hours. It is possible that you were not using the right meter and/or the right weighting. I am hoping that you are not actually listening to that kind of SPL.

 

[Jay aLBERS]

I was thinking that too, that you have it for so long so the risk of damaging anything is very low indeed. Just keep in mind though, at least in theory the potentially much high voltage capability of the bridged amps represent a high risk when driving low impedance. The newer NAD gear likely have advanced protective circuits built in but the older one probably just rely on the sort of low impedance switch that would simply lower the maximum rail voltage and that would effectively negate the effect of bridging. Anyway, sound like you have nothing to worry about and can just enjoy your nice set up. I still think you should not listen anywhere near 100 dB SPL for long duration, a few minutes won't do much harm but not hours. It is possible that you were not using the right meter and/or the right weighting. I am hoping that you are not actually listening to that kind of SPL.

Hours on end, no way. It's uncomfortable. Showing off a few song when my friends are over. OH YA...