[Alan P]

I discovered something very interesting today.....the lower I can get Audyssey to set my sub level, the more headroom I have.


I was getting it close to -6db with Audyssey so I could boost it by 6db ending up at 0db and I was getting a little distortion at "0" MV. Completely by accident I had Audyssey set the subs to -9db and (after my standard 6db boost) the distortion at "0" MV disappearred....hmmm, I said.


So, I turned the subs' gain up a bit more and got Audyssey to calibrate them at -11.5db. I was then able to boost the subs by 9db with no distortion at reference! I don't plan on keeping it there since I'm kinda scared I may damage my house.

Anyone else experience this phenomena? I'm guessing having the gain on the subs as high as possible somehow allows for more headroom, but I'm not sure.


Denon 2113ci (Audyssey XT)

4 PSA XS15 subs

 

[basshead81]

Yes I have...more then likely the AVR is clipping the input signal to the subs. My AVR will do the exact same thing if I try to turn it up past 0 with a standard 75db calibration and the AVR sub trim set @ 0. What you are doing is using less input voltage from the AVR and compensating by using more input gain on the sub amp.


I believe there are several PSA sub owners out there that have not come close to unleashing the full potential of thier subs because of this. It could be with different subs too, but I first noticed it with my XV15's. They like the amp gain set around 2-3:00 and the AVR sub trim around -3. That seems to be the sweet spot.

 

[braveheart123]



Quote:
They like the amp gain set around 2-3:00 and the AVR sub trim around -3.

It's all relative to listening space, trims on the rest of the speakers, speakers' sensitivity, room acoustics. It's all in the trim levels and ironically it's all relative. So, discussing this topic will yield nothing to anybody's good as everybody has different rooms, layout, gear, and most importantly listening preferences.

 

[Gov]

As an example, I am running my dual XV15's 3dB over what Audyssey has calibrated them to. One of the sub's gain is at 1 o'clock the other about 12:30. The trims on my AVR at both at +2.0 dB.

Now if I wanted to, I could turn up the gains on the XV's and after calibration my AVR trims would be somewhere under +2 dB even with bumping the trims up.

IMHO...why bother, I would essential gain nothing it is all relative

 

[DreamWarrior]



Quote:
Originally Posted by Gov  /t/1521522/gain-trim-headroom#post_24459229


As an example, I am running my dual XV15's 3dB over what Audyssey has calibrated them to. One of the sub's gain is at 1 o'clock the other about 12:30. The trims on my AVR at both at +2.0 dB.

Now if I wanted to, I could turn up the gains on the XV's and after calibration my AVR trims would be somewhere under +2 dB even with bumping the trims up.

IMHO...why bother, I would essential gain nothing it is all relative

That's where you're wrong. You will gain something, because right now it's likely that your subs are cutting the input voltage from your receiver down. Which means you're basically putting a resistor in-line with the receiver's pre-outs and wasting power into the resistor. So, if your receiver is capable of 1v of output without clipping and your sub amplifier needs, say, 1 volt to reach maximum power, and you've dialed down the gain, well, now it may need 1.5v to reach maximum power, because the resistor saps some of it up. Of course, this means you'll have to clip your receiver (or just never reach the full potential of your sub amplifier).


Therefore, you'd be much better off turning up the sub gains as much as you can so you can make the most use of your pre-out voltage (which is probably fairly limited as it is). Turning gains up is not usually a problem unless the input sensitivity on your amplifier is so high that it becomes an impediment to your noise floor (i.e. starts to hiss) which is not so likely out of a sub. Of course, if your pre-out is capable of overdriving the amplifier's input (which is probably unlikely and easily controlled by you not turning up the volume so much, lol) then you also may elect to adjust your gain structure such that the sub amplifier gains are dialed down.


edit: here is a Audioholics article discussing voltage gain. They don't discuss variable gain, because many consumer amplifiers don't have gain knobs, but these knobs control the sensitivity. As you turn the knob down the input sensitivity goes down. As you turn it towards 0, you reach the maximum input sensitivity.


edit: also, I'm not sure if the amplifier gains are really implemented with a resistor, I don't design amplifiers. So my explanation may be wrong, but ultimately, as you lower your gains on the sub amplifier, it takes more input voltage to reach a given output voltage (and thusly wattage). Turn it too low and you'll never reach maximum wattage without clipping your receiver's pre-outs, which means you'll never use the full potential of the amplifier with a clean signal. It's pretty much that simple....

 

[Alan P]

basshead & DreamWarrior - that makes perfect sense now! Wish someone would have told me this years ago....I've been on AVS for over a decade and it's the first I'm seeing of this little trick to get more from your subs. This should be in a sticky!

 

[Bill Fitzmaurice]



Quote:
Originally Posted by Alan P  /t/1521522/gain-trim-headroom#post_24454486


Anyone else experience this phenomena? I'm guessing having the gain on the subs as high as possible somehow allows for more headroom, but I'm not sure.

The higher the sub volume is set the lower will be the output level of the AVR line driver. That gives more headroom in the AVR line driver and more headroom in the input stage of the sub amp. The downside is that this also lowers the signal to noise ratio, but there tends to be very little noise with a sub anyway. By and large you're best off to have the sub amp volume relatively high and the AVR sub out volume relatively low.

 

[DreamWarrior]

Now I have to go and take my own advice, lol. My SubM gains are very low and I am pretty sure when I rack the gains up to run the subs "hot" (putting the sub channel trims around +6.5 and +5.5) I probably wind up clipping the pres for some material. "Bass I Love You" seems to dislike this configuration thoroughly; heck I can see the difference. Just watching my table as I turn down the channel trims it'll vibrate harder as the trims go down, which is counter to what it probably should do. I assume it must be because I'm just clipping like mad and loosing all that "room vibrating" content to clipping. Of course, I don't know for sure...it's just a theory.


So, I should probably crank up the SubM gains and lower my channel trims closer to -12. Easy enough, I assume I can just pink noise with all other channels but the one sub turned off -- take reading, trim channel down as low as it'll go, crank gain until original reading is reached. I suppose that should be good enough, no? Makes sense...but...sometimes I think things make sense and they don't. Then, rinse-wash-repeat with the other sub (being the only driver turned on). Moreover, since I'm only looking for relative change, it shouldn't even matter the level the pink noise is at or anything else.... I don't even know if it'd matter even whether the DEQ is on or not.... In theory, I suppose it shouldn't supposing that the only thing contributing to the DEQ curve is the MV setting.... Humm...anyone know?


Succinctly, this post asks -- Is there a "proper procedure" to "re-gain" the channels (in this case, specifically the sub channels) after Audyssey has been run?


Of course, what I really need is better (stronger) pre-outs (and preferably balanced). On that note -- hey, Emotiva, you *ever* going to release that XMC-1?

 

[craig john]



Quote:
Originally Posted by DreamWarrior  /t/1521522/gain-trim-headroom#post_24465461


Now I have to go and take my own advice, lol. My SubM gains are very low and I am pretty sure when I rack the gains up to run the subs "hot" (putting the sub channel trims around +6.5 and +5.5) I probably wind up clipping the pres for some material. "Bass I Love You" seems to dislike this configuration thoroughly; heck I can see the difference. Just watching my table as I turn down the channel trims it'll vibrate harder as the trims go down, which is counter to what it probably should do. I assume it must be because I'm just clipping like mad and loosing all that "room vibrating" content to clipping. Of course, I don't know for sure...it's just a theory.


So, I should probably crank up the SubM gains and lower my channel trims closer to -12. Easy enough, I assume I can just pink noise with all other channels but the one sub turned off -- take reading, trim channel down as low as it'll go, crank gain until original reading is reached. I suppose that should be good enough, no? Makes sense...but...sometimes I think things make sense and they don't. Then, rinse-wash-repeat with the other sub (being the only driver turned on). Moreover, since I'm only looking for relative change, it shouldn't even matter the level the pink noise is at or anything else.... I don't even know if it'd matter even whether the DEQ is on or not.... In theory, I suppose it shouldn't supposing that the only thing contributing to the DEQ curve is the MV setting.... Humm...anyone know?


Succinctly, this post asks -- Is there a "proper procedure" to "re-gain" the channels (in this case, specifically the sub channels) after Audyssey has been run?


Of course, what I really need is better (stronger) pre-outs (and preferably balanced). On that note -- hey, Emotiva, you *ever* going to release that XMC-1?

When Audyssey runs, the first step is to set the subs to 75 dB. Forget that. Set them to 83 to 85 dB. This will yield a -10 or so subwoofer trim setting after Audyssey. This provides 10 db of headroom before you even get to 0, and completely eliminates the possibility of overdriving the sub amp inputs. This was another one of Mark Seaton's "little tricks" I learned years ago.


Craig


Edit: If you're "out of range" after running Audyssey with this technique, just turn the subs down a dB or 2 and run it again.

 

[Gov]

So should I shoot for my receiver trim levels to be somewhere between -10 and -5dB?


Also, I don't want to have to rerun Audyssey again, so can I make the adjustment with the pink noise generator with my Denon 4311?


I know I would have to set each subwoofer to 72 to 73dB with the Rat Shack analog SPL meter. Then I would bump the trims up 3dB to run it a little hot.


If I recall correctly, I used the pink noise and SPL meter to check what Audyssey set my subs at and both registered around 72 or 73dB


Thanks

 

[DreamWarrior]



Quote:
Originally Posted by craig john  /t/1521522/gain-trim-headroom#post_24465527


When Audyssey runs, the first step is to set the subs to 75 dB. Forget that. Set them to 83 to 85 dB. This will yield a -10 or so subwoofer trim setting after Audyssey. This provides 10 db of headroom before you even get to 0, and completely eliminates the possibility of overdriving the sub amp inputs. This was another one of Mark Seaton's "little tricks" I learned years ago.


Craig


Edit: If you're "out of range" after running Audyssey with this technique, just turn the subs down a dB or 2 and run it again.

I tried that last time and I thought I remember it refusing to let me proceed until I set them where it wanted them. If I recall correctly, it did a quick level test, whined, and then greyed out the continue button until it was around 75 db. I'll have to try again, next time I run a calibration -- which won't be until I start pushing my Cats around the room and get them toed where I think I want them.


Either way, assume at this moment I don't want to run again -- does my method work?

Quote:
Originally Posted by Gov  /t/1521522/gain-trim-headroom#post_24465715


So should I shoot for my receiver trim levels to be somewhere between -10 and -5dB?


Also, I don't want to have to rerun Audyssey again, so can I make the adjustment with the pink noise generator with my Denon 4311?


I know I would have to set each subwoofer to 72 to 73dB with the Rat Shack analog SPL meter. Then I would bump the trims up 3dB to run it a little hot.


If I recall correctly, I used the pink noise and SPL meter to check what Audyssey set my subs at and both registered around 72 or 73dB


Thanks

Craig has said this before, and I agree, that once you run Audyssey you should not use the pink noise generator because it is not running through the calibration. I believe what you should do is get an external source of pink noise (a calibration DVD/BD or even CD) and use that instead. Here is a site I found via Google search that also has some online wav files if you can play those (or burn to CD). Not sure how good they are...but probably good enough.


P.S. I also have a 4311ci, and I'm shooting for mine to be at -12 if I can get it there, lol. I like my bass hot, and until I can get a mini-dsp to properly implement a slowly descending house-curve, I need all the headroom I can get on my pre-outs to get my 12 db of heat that I like for my club music and some rock music. I have a feeling, though, once I get a proper house curve, my need to constantly tweak the sub trims for different content will be drastically reduced -- but that's another topic for another thread.

 

[Gov]

Since I know the reading I get with the AV receiver generated "pink noise" 72dB to 73dB, if I made adjustments with the gain on the sub and receiver trims, why not just use the same "pink noise" and set it to the same? I understand what you said and appreciate your input, but I am just trying to understand.

 

[DreamWarrior]



Quote:
Originally Posted by Gov  /t/1521522/gain-trim-headroom#post_24465882


Since I know the reading I get with the AV receiver generated "pink noise" 72dB to 73dB, if I made adjustments with the gain on the sub and receiver trims, why not just use the same "pink noise" and set it to the same? I understand what you said and appreciate your input, but I am just trying to understand.

I suppose since we're just trying to modify things a set amount, it could work with the receiver tones.... I suppose all you're trying to find out is "how many clicks on the sub gain does it take to get +5 dB more output". I suppose the question is, "does that number of clicks change whether room EQ is in effect?" I would err on the side of, "yes." But, I could make an argument for "no". Honestly, I just have to claim ignorance here, I don't know enough about the extent of what room EQ is really doing and how it'll interact with the SPL level in the room at the MLP. So...I'd rather have it in the loop than out, since ultimately it'll be in the loop when you playback. Maybe someone like Craig can better inform us both....

 

[craig john]



Quote:
Originally Posted by Gov  /t/1521522/gain-trim-headroom#post_24465882


Since I know the reading I get with the AV receiver generated "pink noise" 72dB to 73dB, if I made adjustments with the gain on the sub and receiver trims, why not just use the same "pink noise" and set it to the same? I understand what you said and appreciate your input, but I am just trying to understand.

Here you go...

http://www.avsforum.com/t/1165099/official-jtr-speaker-thread/15870#post_24320284


In that post, I explained why it's important to use external test tones after running Audyssey, along with measurements of the internal test tones and 2 different external test tones.


Craig

 

[Gov]

This is what I downloaded http://www.audiocheck.net/testtones_pinknoise.php will that work?

 

[DreamWarrior]



Quote:
Originally Posted by Gov  /t/1521522/gain-trim-headroom#post_24466128


This is what I downloaded http://www.audiocheck.net/testtones_pinknoise.php will that work?

It should, I just pointed to the lossless version because I'd be leery of using an MP3 for a signal that is supposed to have an exact set of power rules. If MP3 does something that mucks with the acoustic energy content (which, I'm not sure it does, but I believe it does to some extent to compress it) then it may not be spectrally accurate. I'd download the WAV and burn it to a disc, myself if I couldn't directly play the WAV. But, I'm anal, lol...I'm sure it'll be good enough for this purpose....

 

[Gov]

Actually, I just found an old DVD I have "Sound and Vision Home Theater Tune up" I bet I can use that. If I recall correctly, the tones on that disc are output at 85dB (not 75dB) with the MV on the receiver at 0??


Also, should I just have XT32 engaged and dynamic EQ turned off when checking?

 

[DreamWarrior]



Quote:
Originally Posted by Gov  /t/1521522/gain-trim-headroom#post_24466308


Actually, I just found an old DVD I have "Sound and Vision Home Theater Tune up" I bet I can use that. If I recall correctly, the tones on that disc are output at 85dB (not 75dB) with the MV on the receiver at 0??


Also, should I just have XT32 engaged and dynamic EQ turned off when checking?

That will work, I'd bet it has a pink noise track and the level of the track doesn't matter for this exercise, nor should the level of the MV position.


Having said that, yes, I'd have XT32 engaged and I'm not sure about DEQ, but I suppose I'd turn it off just for safety sake. Do you have omnimic or REW? If so, I'd do a before and after sweep. If all went well, you should have the exact same (or close enough) sweep before and after....


Also, like I mentioned, I'd certainly play *only* the subwoofers for this. Easiest if you can play a sub-only pink noise track, or just disconnect all other speakers. If you have multiple subs, I'd guess you only want to do one at a time as well.... Let me know how it goes, you can be my guinea pig

. I'd do it now, too, but the wife is sleeping and she'd be unhappy if I started running obnoxious sweeps and pink noise when she needs to be up early tomorrow -- rightfully so, I suppose.

 

[kbarnes701]



Quote:
Originally Posted by craig john  /t/1521522/gain-trim-headroom#post_24465527

 

When Audyssey runs, the first step is to set the subs to 75 dB. Forget that. Set them to 83 to 85 dB. This will yield a -10 or so subwoofer trim setting after Audyssey. This provides 10 db of headroom before you even get to 0, and completely eliminates the possibility of overdriving the sub amp inputs. This was another one of Mark Seaton's "little tricks" I learned years ago.


Craig


Edit: If you're "out of range" after running Audyssey with this technique, just turn the subs down a dB or 2 and run it again.

 

I've been doing it this way for years too, Craig. I work from 85dB at the initial Audyssey stage, just as you have suggested and the reason is so that I can, if I wish (which sometimes I do) run my dual Submersives a few dB 'hot' while still staying within the broad Audyssey guideline of -3.5dB to +3.5dB for the sub trim. In fact, having destroyed a lesser sub many years ago by using a sub trim of +8dB (how naive I was!) I always like to stay at or below 0dB on the sub trim.

 

I covered this in the Audyssey FAQ, here:

 

f)4.    If I want to run my subs a little 'hot' where should I make the changes?

 

I wonder if this Answer needs updating to bring in some of the concepts discussed in this thread, and especially the endorsement by Mark, which I was unaware of until just now?

 

[kbarnes701]



Quote:
Originally Posted by DreamWarrior  /t/1521522/gain-trim-headroom#post_24465810

 

I tried that last time and I thought I remember it refusing to let me proceed until I set them where it wanted them. If I recall correctly, it did a quick level test, whined, and then greyed out the continue button until it was around 75 db. I'll have to try again, next time I run a calibration -- which won't be until I start pushing my Cats around the room and get them toed where I think I want them.

 

 

Audyssey Pro definitely lets you proceed after giving you a warning. It is so long since I used regular XT32 that I can't remember how it does it.

 

I'd be grateful if someone with XT32 could let me know if you can ignore the 75dB recommendation so that I can include it in the Audyssey FAQ (if it refuses to play ball). Thanks.