Home Theater Forum and Systems banner

41 - 60 of 86 Posts

·
Registered
Joined
·
2 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Thanks Wayne. Yes, when I change the speaker "trims" I would expect the voltage output to change, but it does not. One theory a friend (that is an engineer) told me is that perhaps it needs to be loaded - so maybe a Y cable with one into the Crown (volume turned down) and measure off the Y. While I'd like to figure this out, I've moved on to other gear so it's a bit moot. I appreciate your response though. Thanks.
 

·
Registered
Joined
·
164 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Does dialing in your speakers to 75db with pink noise make 0db on your receiver represent 75db at mlp? Then setting the sub gain to zero on the receiver and using the gain to get it up to 75db (with eq running and receiver on) makes it match your mains? As long as you don't clip it doing this aren't you safe? Ie using pink noise from your receiver.

Pete
 

·
Super Moderator
Joined
·
9,203 Posts
Discussion Starter #43
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System


Hi Pete,

The article is about proper gain setting in a system using outboard pro audio gear. It’s not about adjusting speaker levels with a standard AVR and powered subwoofer. I suggest opening a thread with your question in one of the main forums.

Regards,
Wayne
 

·
Registered
Joined
·
45 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Hi Wayne,

I have read many of your articles on REW and just recently started playing around with implementing a hard knee house curve as a result of your suggestions on the topic. Thank you for another great article!

I am using my AVR to power my speakers but am using a pro amp on my subwoofer. My setup is as follows;
-Denon 4311ci AVR: spec'd at 1.2Vrms output (I have not measured)
-MiniDSP balanced with selectable .7V or 2V input sensitivity and 2Vrms output
-Peavey Ipr2 5000 amplifier on my subwoofers- 1.95V input sensitivity.

The Peavey owner’s manual recommends keeping the gain dial turned all the way clockwise for “maximum headroom” and this is how I have always ran it. I have noticed that at lower volumes the subwoofer doesn’t seem to do much, I have felt the volume the speakers turned down and the volume the subwoofer turned down wasn’t parallel to each other and there was a certain point the subwoofer finally would kick in or drop off. For example at -35db on the Denon the subwoofer had very little output in comparison to the speakers. But with the volume at -25 or -20db then the subwoofer would be at an appropriate level to match the speakers.

I am under the impression, and hope, that the MiniDSP outputs a signal equal to what it is receiving so is there a need for me to optimize the gain structure on the MiniDSP? And if so how would I perform this? One idea I had was to adjust the gain from the receiver to the amplifier just to the point of the clip light flickering. Then adding the minidsp in between the two and getting it to the same point where the clip light on the amp starts to flicker. Would this work well enough?

One more question. If, for example, I end up finding that having the subwoofer gain in the AVR at +6 and the gain on the amplifier at say -12 is the optimal level to have their gain matched what should I do when I run audessey and it turns the subwoofer down to -3 or -1 or whatever it may be. Should I turn the gain on the amplifier up the level that the receiver was turned down?
Thanks again for all your knowledge and sharing it with all of us!
 

·
Super Moderator
Joined
·
9,203 Posts
Discussion Starter #45
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System


Thanks for the kind words, Devon. :T


The Peavey owner’s manual recommends keeping the gain dial turned all the way clockwise for “maximum headroom” and this is how I have always ran it. I have noticed that at lower volumes the subwoofer doesn’t seem to do much, I have felt the volume the speakers turned down and the volume the subwoofer turned down wasn’t parallel to each other and there was a certain point the subwoofer finally would kick in or drop off.
The information from the Peavey manual doesn’t make much sense. Any amp naturally gets its highest noise floor with the gains all the way up, so you actually get more dynamic range (defined as the “distance” between the noise floor and highest clean input signal) with the gain reduced. Of course, this assumes that the incoming signal is hot enough to begin with to accomodate lower gain settings.

As far as the inconsistent levels with various volume controls, I have no explanation for that. It sounds like some kind of signal gate is in play. If you don’t know what that is, it’s an effect commonly used in pro audio to shut the output signal down when the input signal falls below a certain threshold. For things like drum mics, for instance, to keep cymbals from bleeding into the snare drum mic when it’s not being hit. Check the miniDSP to see if has some kind of feature like this, and if so disable it.

In case you haven’t already, I’d set the Peavey’s back-panel filters for full range and let the AVR or miniDSP provide the low pass filtering.


I am under the impression, and hope, that the MiniDSP outputs a signal equal to what it is receiving so is there a need for me to optimize the gain structure on the MiniDSP? And if so how would I perform this? One idea I had was to adjust the gain from the receiver to the amplifier just to the point of the clip light flickering. Then adding the minidsp in between the two and getting it to the same point where the clip light on the amp starts to flicker. Would this work well enough?
Like any other outboard equalizer, the miniDSP should not need any level settings to optimize gain structure. It should pass the signal straight through (along with whatever is added with any equalization, of course). So what you’d want to do is re-adjust the Peavey’s gain settings after the miniDSP is added to the signal chain, to accommodate any changes to gain the equalization brings.

My only concern is that the miniDSP, with only 2 Vrms capability, it might not have enough headroom to pass the signal level the Denon as actually capable of generating, and will clip. As noted in Part 7, the receiver I used while researching the article put out way more voltage than the manufacture claimed, so I wouldn’t put much stock in Denon’s spec.


One more question. If, for example, I end up finding that having the subwoofer gain in the AVR at +6 and the gain on the amplifier at say -12 is the optimal level to have their gain matched what should I do when I run audessey and it turns the subwoofer down to -3 or -1 or whatever it may be. Should I turn the gain on the amplifier up the level that the receiver was turned down?
If you’re not happy with the sub level Audyssey generates, then I’d over-ride it and set it where you think it should be. If Audyssey won’t let you do that from the receiver specifically for the sub output, then it’s easy enough to change it on the back end – i.e., the amplifier gain controls.

Hope this helps!

Regards,
Wayne

 

·
Registered
Joined
·
164 Posts
http://www.avsforum.com/forum/155-diy-speakers-subs/1443652-minidsp-require-signal-boost-pro-amps.html

It sounds like if you have the balanced or unbalanced minidsp you should be fine. Do you have the audyssey dynamic volume on? It might help with the sub going quiet.

What worked for me is setting the avr to 0db gain for the sub and then using an SPL meter with the avr pink noise on (still set to 0db) and turning the amp up/down until you hit 75db at the MLP. Then you can tune how "hot" your sub is based on the 75db reading (you should also do this with all your speakers btw, set the gains to 75db). I think audyssey does fine with distances, and corrections but it tends to set the gains terribly. My onkyo 609 varies 1 or 2 db per speaker in my media area, ymmv. A good mic or SPL meter is really helpful here. My 2cents.

Pete
 

·
Registered
Joined
·
45 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Thanks Wayne and Pete for your feedback.

Wayne, after reading the article my understanding was that the goal was to have the pre-out or subwoofer out gain within the AVR set just high enough that it is almost to the point of clipping at reference level. Is this correct? And with that level set in the AVR, then set the gain on the amplifier to the same point just before clipping so that like you said, they will start clipping at the same time. But if I were to then run audessey and it turned the gain down on one or more of my channels and to compensate I turned the gain up on the amplifier wouldn’t that throw out all of the gain structuring I just did? Or would it still be in acceptable range?

I hope what I'm asking makes sense. Also, would REW with the tone generator be an acceptable substitute to the test disk with tones? Thanks again!
 

·
Super Moderator
Joined
·
9,203 Posts
Discussion Starter #48 (Edited)
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System


But if I were to then run audessey and it turned the gain down on one or more of my channels and to compensate I turned the gain up on the amplifier wouldn’t that throw out all of the gain structuring I just did? Or would it still be in acceptable range?
As long as you’ve done the gain structuring exercise prior to running Audyssey, you’re good.

The idea of the gain structure exercise is merely to make sure that clipping sets in on the pre amp and outboard amplifier at the same time. At that point (as I noted in Part 9) you adjust all the speaker and sub levels as is normally done. It doesn’t matter if it’s done manually or via an auto-calibration system like Audyssey.

In other words, gain reduction at the various stages in the system post gain-structuring doesn’t ruin the gain structure, as no one runs their system at max anyway. Make sense?

Regards,
Wayne

 

·
Registered
Joined
·
45 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Yes I think it is starting to make sense. The purpose of having the gain all the way up in the AVR during the setup is just so that it will output its maximum signal before clipping and that signal is used to match the amplifier. After the initial setup the AVR doesn’t need to use its max signal anymore and can be set pretty much anywhere it needs to be correct? If the amplifier gain stays the same as what it was set to during the setup then no matter what gain the AVR is using (as long as it is below what the discovered clipping point is) both will still clip at the same time?

Possibly very over simplified, but is that the general idea?
 

·
Super Moderator
Joined
·
9,203 Posts
Discussion Starter #50 (Edited)
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Yes, that’s about it. And it's not "over simplified," it really is as simple as that. :D

However, if you don’t like what Audyssey did to the sub level – say, cut it 3-4 dB from the AVR’s sub output - and if the receiver won’t let you re-adjust the sub level manually, you can just make it at the amp itself. It’s all the same in the end. It would be the same as if you’d gain-structured with a 3-4 dB lower signal from the sub output to begin with, so the amp’s gain settings would have been changed accordingly. Make sense?

Regards,
Wayne
 

·
Registered
Joined
·
45 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Great! That makes perfect sense. Thanks for explaining it. I have a lot of new things to try out and keep me busy this weekend. A Linkwitz transform, hard knee house curve and now optimizing the gain structure.

Thanks again, Wayne!
 

·
Premium Member
Joined
·
7 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Thanks for these articles. For years I had used a Behringer DCX2496 to drive my power amplifiers. The 0dbfs corresponds to about 10V RMS, way too much for any power amplifiers I have (though one requires 5v RMS for actual clipping). Over at DIYAudio there is a thread on the DCX2496 and there are endless variations of modifications to get 0dbfs more "appropriate" to consumer hifi. One thing to do, for example, might be to attenuate the existing outputs by 6 or 10dB. I long ago determined this was not a good idea. The rated distortion of 0.002% only applies at 2V output. Before you get to 10V output, distortion has risen to 0.3% (not spec'd, this is my measurement). So you really want to keep output level from existing circuitry below 5v if not 2V anyway. Since I only use digital input to the DCX, I've never thought much about input levels. I didn't worry much about the S/N in digital domain given that I still have >16bits at -30dB, which seems to be like your argument.

But now I do something different in my main system, where I don't cut corners. Instead of using DCX as crossover for the midrange, I use a Behringer DEQ 2496. I create the required high pass filter using a pair of PEQ's that produce a perfect LR24. The DEQ gives me digital output which I run to a repurposed Onkyo RDV-1 as DAC. I like RDV-1 because it's well made piece with true PCM 1704 ladder DAC's.

This has completely changed the gain structure. Now, at 0dBfs I get barely above 2V output. That means I can't drive that amplifier to full voltage output…but it's still plenty loud enough. I had to dial down the remaining sub and super tweeter outputs from the DCX to match (subwoofer is dialed to maximum -15dB cut).

Incoming digital now plays at -10dB attenuation or less, often as little as -2dB (before it was -20dB). I watch the midrange and it never runs out of headroom, but much closer than before.

I like this a lot better, and I think it sounds a lot better. I play a lot of 24bit digital recordings, and I think this gain structure preserves the information much better than before.
 

·
Registered
Joined
·
24 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Hi Mr. Pflughaupt and all,

Let me start off by telling you that French is my first language so if i am unclear just let me know :)


I was reading your post on using an avr with pro power amps and I have a few questions regarding how to do it with my setup.

Fisrt of all, I am using a Integra DTC 9.8 connected via XLR outputs to 3 Crown CTS600 amps. My speakers are 5 Martin Audio Effect 5 speakers that have an sensitivity of 95dB 1 Watt/1 metre. All that stuff in a 13x22 room.

If I am right, the way to calibrate a THX certified pre-pro to reference level is to get -30dB relative to full scale (0dB) that creates 75dB as measured with a C weighted SPL meter at the listening position.

So, I set my front left speaker SP Level to 0dB, I start the internal pink noise signal and play with the gain of the Crown Amplifier until reading on the SPL meter is 75dB. After that, I set all the Crown amps inputs on the same page and calibrate the other channels using the SP Levels until each channel read 75dB. To acheive that, I am reducing the input level on the Crowns to +- 3/4.

But I guess, I am missing something as the reading on the amps are not near to lit the clipping light. I mearly got the -20dB light flashing...


As for the Crowns, the sensivity is 1.4V, the Voltage Gain is 31dB and it puts out 300W in 8 ohm.

The amp is putting out 48.99 volts of output at full power (300=Voltage^2/8).

I Used "Voltage Gain (Av) = 20 * Log (Vout/Vin)" to found the voltage gain.

So to deliver full power, the pre-amp needs to put out 11.4V right?

Do my Integra is putting enough voltage to drive the Crowns?

If so, should I put up the gain on the amps and listen with the pre-amp to -XXdb?

Thanks.
 

·
Super Moderator
Joined
·
9,203 Posts
Discussion Starter #54
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Do my Integra is putting enough voltage to drive the Crowns?

As for the Crowns, the sensivity is 1.4V, the Voltage Gain is 31dB and it puts out 300W in 8 ohm.

So to deliver full power, the pre-amp needs to put out 11.4V right?
No, the pre-amp only needs to put out 1.4V to drive the amp to maximum. I’m confident that the Onkyo can deliver that much.


But I guess, I am missing something as the reading on the amps are not near to lit the clipping light. I mearly got the -20dB light flashing...
No, you aren’t missing anything. The situation is that your speakers are extremely efficient, and could be driven to ear-bleeding levels with less than 100 watts, yet your amp puts out 300 watts per channel. So you will never see high meter readings on the amp. If you drive that amp to maximum output with those speakers, you’ll probably be breaking windows and getting visits from the police.

Bottom line, you don’t have a problem with your amps or pre-amp. Everything is working fine. :T

Regards,
Wayne
 

·
Registered
Joined
·
24 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

By the way, thank you Wayne for that quick and straight to the point answer :)
 

·
Registered
Joined
·
3 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Great Guide, Thanks!!

Results Report

AVR Denon X4000

Max Preamp Output 7.14
Max Clean Output 4.2 (41% lower)

Right channel measured only
 

·
Registered
Joined
·
10 Posts
Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Hi, Wayne:

Thanks for the guide. My test results with EMOTIVA UMC-200:
https://drive.google.com/open?id=0B7-tKLkKnSm0VmpXdEEycDVtTnc

When measuring AVR subwoofer output voltage, you use 0 dBFS signal. Do we need to +10db for concerning about playing DOLBY/DTS LFE channel? Just like REW channel 4 add 10db output?
 
41 - 60 of 86 Posts
Top