# Matching a consumer AVR with a professional subwoofer amp



## Lee Batchelor (Jul 6, 2014)

Hi everyone,

I’ve been away for a while but have a question about gain matching between a consumer AVR and professional subwoofer power amp. I need to understand how this works. I read a great article about this by Wayne A. Pflughaupt back in 2010. (Thanks Wayne!) He explains it very well but I need some specific advice.

*My setup*
I’m using a Denon AVR2308CI AVR (Denon), which is about 15 years old but still in mint shape. It has HDMI in and outputs. Its subwoofer out jack is connected to a professional Yamaha PX3 power amp (PX3), which is connected to my home made Eminence Lab 12 sub.

My sub has no crossover so I use the high and low pass filters in the PX3 power amp to limit the frequency response. The PX3 is in summed mode and puts out 600 watts RMS, which closely matches what the Lab 12 driver can handle. The PX3 has a Protection and Clip light on the front. In the Denon, I set the signal sent to the PX3 to +15dB. According to the Denon manual, this is the recommended – at least from what I can gather. Their documentation is SO bad. Thanks to Wayne’s 2010 article, the main issue is making sure the Denon sends a strong enough signal to the PX3 amp, correct?

I know a +15dB boost sounds like a lot but without that, I need to bump the PX3 volume knob up very high to drive the Lab12. It has worked perfectly for the past 8 months. I tried dropping the signal from the Denon to +10 dB and now the clip light activates on occasion on the PX3. I assume at +10db there’s insufficient signal going to the PX3? On the PX3, there is a setting in the menu for the output level. In the manual, it says “LEVEL (output level). Sets the output level to balance the output levels of channels.” I assume that means I only change this if I’m running two input sources separately to the two amps in PX3 and I need to compensate so the volume knobs are roughly the same for a given dB output?

So the question becomes, is my Denon output set up correctly? It seems to work fine with no clip lights coming on with the PX3. When I drop to +10dB output, the PX3 clips. Thoughts?

Many thanks.

*Edit*
The cabling between the Denon and the PX3 is an RCA to 1/4 inch plug. The actual cable has two RCA ends, so I have to use an RCA to 1/4 inch adapter. Perhaps this cabling is yet another weak link in the signal chain?


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## david yurik (Feb 17, 2013)

I had almost the exact same issue from a 4400 to a Berhinger EP-4000. I believe the PA / professional gear is looking for a bigger input signal than what our receivers put out on the RCA jack pre out. I installed a Henry 3100 converter.







This boosted the signal into the Behringer and thus the speaker output. I no longer needed the large volume adjustments at the receiver and the Behringer clipping lights stopped. Hopefully that helps.

Dave


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## Lee Batchelor (Jul 6, 2014)

Hi Dave,

Many thanks for chiming in. I've done some research since posting this question and I think you're spot on. I recalibrated my Denon using the Audyssey software, and then added some minor tweaks. The clipping has stopped so there must have been a setting out of whack somewhere. Until now, I never knew there was such a disparity between consumer and pro audio!

I must look into that Matchbox. Thanks for the lead. Merry Christmas and thanks again.

- Lee 🎄


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## Lee Batchelor (Jul 6, 2014)

Just curious, Dave. Can I use a mini mixer between the Denon and Yamaha power amp instead of the Matchbox? Wouldn't the mini mixer act as a preamp if it had RCA inputs?


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## david yurik (Feb 17, 2013)

Lee Batchelor said:


> Just curious, Dave. Can I use a mini mixer between the Denon and Yamaha power amp instead of the Matchbox? Wouldn't the mini mixer act as a preamp if it had RCA inputs?


Lee I can't answer that question as I have zero experience with Pro Audio equipment. If you already have something I would at least try it. Could save yourself some $$.

The Matchbox is just one option. There are others. I think the ARTcessories CleanBox Pro was also another popular converter but I don't have personal experience with those products.









Dave


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## Lee Batchelor (Jul 6, 2014)

Thanks David. Where I buy my pro audio gear has an ART dealership. I'll check that out.


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## BandY (Oct 26, 2021)

Hi Lee,

you wrote: 

"I need to bump the PX3 volume knob up very high to drive the Lab12."

There is nothing wrong in running the Yamaha with "volume knob up very high".
The "volume knob" on PA amps is not the same as on AVRs. Most AVRs pre-amp section reduces the signal level until it reaches 0 dB. At 0 dB the pre amp in AVR passes the signal as is. If tuned higher (in the +dB range it amplifies the signal. (until it reaches its limits and start clipping).
On most PA power amps the "volume" knob is actually input attenuator that can only reduce the input signal. I run my PA sub amp (Crest CA-4) with input volume controls fully open (0dB, all he way to the right) with no ill effect.
Most PA power amps have input sensitivity switches that allows to set the input voltage to match your pre-amp. In HiFi world the voltage is usually lower (0.5-2V) while PRO PA systems use higher input voltage, typically 2 to 4V or more.
Your Yamaha PX3 (based on a quick look at the manual) does not have sensitivity switch, but it seems to auto-adjust the gain based on input voltage. I am not sure how does this affect dynamics of the amp, but let's assume they know what they are doing.

You mentioned that the PX3 was fine with +15 dB from the AVR, but was clipping with lower level signal of +10dB. That is highly unlikely, perhaps some other setting were changed?

Since you are using the x-over in PX3, did you set the AVR to pass full range signal to the sub output? It would be beneficial to run only ONE x-over in the signal path, not 2.

Hope this helps.


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## Lee Batchelor (Jul 6, 2014)

Hi BandY. Great information. Many thanks!

I'm also a musician and I understand your comment about running the power amp full. I've never understood the vast differences between consumer and pro audio until now. I recently learned that the +15dB or +10dB setting on the Denon doesn't affect the HDMI connected devices. So, you are correct. The settings make no sense in my context. It's only there to bump up the analog devices, which I no longer use. You're right about Yamaha. They seem to adjust things internally. 

As for the x-over points, I didn't know that setting two devices up to handle the x-over frequencies was not a good idea. On the Yamaha, I have it set for subwoofer only, not full range where various x-over presets are offered. Hence, I set the high pass filter to 25 Hz, as recommended by Eminence Loudspeakers, and the low pass filter is set at 160 Hz. So, there is no x-over being used in the Yamaha. On the Denon, I have the x-over set to 80 Hz for all channels. The LFE is set to 100 Hz. So, I guess the Denon is doing the x-over functions and the Yamaha only has filters applied.

After recalibrating the Denon, the sound is excellent. Wish you could hear it . Thanks again for your help.

- Lee


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## BandY (Oct 26, 2021)

Hi Lee,
glad I could help & happy you are enjoying your system.
Feel free to contact by PM if you need more info. By the way, Ont here.


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## Da Wiz (May 8, 2019)

What you NEVER want to do under ANY circumstances is to have TWO devices doing crossovers or level control or whatever. I would suggest disabling EVERYTHING on the amplifier... leave the amplifier setup with NO crossovers and no bass management. Connect the LFE output of the AVR to the amplifier and use the distance, level, and crossover settings in the AVR.


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## Lee Batchelor (Jul 6, 2014)

Thanks, Da Wiz. I'm essentially doing that - I think . I have to use a high pass filter on the Yamaha to prevent over-excursion of the Lab 12 driver, as per the recommendations from Eminence. As for parametric EQ, I have made a few small corrections in the Yamaha to account for notches in the room response. Everything else is controlled by the Denon. The Yamaha is running in summed mode. Both amps are driving the sub, so there is no crossover.

Sound right?


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## Da Wiz (May 8, 2019)

As long as the amp is passing the input signal to the output without changing anything except amplifying the signal... that's the right way to do it. There's unlikely to ever be anything within commercial video that would damage a subwoofer driver. The Edge of Tomorrow goes down to 10 Hz at the beginning of the movie, starting the downward frequency slide around 40 Hz and ending at 10 Hz... I have 2 subs here that make the room feel like you turned on a big fan starting around 15 Hz, but there is nothing to be heard at 10 Hz, just moving air can be felt. That is not bothersome to the drivers at all, even though it is actually sub-sonic. I find there's usually enough damping in the cabinet and mechanical action of subwoofer drivers that using a subsonic filter/crossover is probably not necessary. Those who play vinyl have to be concerned with possibly dropping a stylus onto a record too soon, so the distance the stylus falls creates a rather outsized audio signal spike to the system... they would be safer with a sub-sonic filter. But filters are not without their sonic effects. I like to NOT use them whenever possible as what they claim to "fix" often doesn't need fixing. One of the reasons you don't need to worry much about filtering higher frequencies out of a subwoofer is because the big heavy woofer voice coil and cone aren't very good physically for reproducing frequencies higher than 150 Hz or so. They get increasingly reluctant to reproduce frequencies above 150 Hz as the size and mass of the moving parts of the driver increase. So most of the time, no low pass filter is really needed on the LFE signal since the audio in the LFE channel is generally limited to 150 Hz and lower most of the time. And even if there are higher frequencies present in the LFE channel, they aren't intended to be reproduced by the subwoofers anyway. That information will already be in surround and/or height speakers where it belongs. Another thing... hopefully you know this already... but when you measure the response in your room to bass frequencies and you find a response dip at, let's say 51 Hz, that is 20 dB deep. Dip[s like these arise from room modes. Room modes change when the position of the listener OR when the position of the source (subwoofer) changes. You CANNOT use any type of EQ to eliminate one of these "suckouts" caused by room modes. If you boost 51 Hz to put more of that energy into the room, the cancellation of the 51 Hz just gets more powerful. So when you are using EQ, your STARTING POINT should be the location of subwoofer and main listener where there are no significant bass suckouts. If you use a point in the room with 1 or more suckouts due to room dimensions (height, width, and length each have a primary suckout frequency or frequencies, when 2 of those dimensions of the room are the same, the suckout becomes twice as powerful, If all 3 room dimensions are the same, there will be at least 1 bass suckout that will be very strong with no ability to remove it with EQ. You can improve ONLY response PEAKS with EQ, never "dips" or "suckouts". Hopefull you will have found this elsewhere, but if not, it is important to remember when dealing with this stuff.


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## Lee Batchelor (Jul 6, 2014)

> As long as the amp is passing the input signal to the output without changing anything except amplifying the signal, that's the right way to do it. There's unlikely to ever be anything within commercial video that would damage a subwoofer driver.


I never thought of it in that way. Eminence probably recommends high-passing the driver at 25 Hz because they need to cover instances where the driver will be put under its full power scenario. Bell Fibe and even quality DVDs played at normal levels will probably not damage the driver. It has a large x-max of 13 mm or about 0.5 inches.



> One of the reasons you don't need to worry much about filtering higher frequencies out of a subwoofer is because the big heavy woofer voice coil and cone aren't very good physically for reproducing frequencies higher than 150 Hz or so.


Interesting. I just checked the usable frequency range of my sub driver. it's 25 Hz to 100 Hz. You're right! A low pass filter is not even needed.



> Another thing... hopefully you know this already... but when you measure the response in your room to bass frequencies and you find a response dip at, let's say 51 Hz, that is 20 dB deep. Dips like these arise from room modes. Room modes change when the position of the listener OR when the position of the source (subwoofer) changes.


Yep, I know this. I measured my bass response at the one listening position. I even tried moving the sub around to 5 different places and got the same reading, a -8dB notch at 38 Hz. I applied a PEQ to correct this. It made a huge difference.



> You CANNOT use any type of EQ to eliminate one of these "suckouts" caused by room modes. If you boost 51 Hz to put more of that energy into the room, the cancellation of the 51 Hz just gets more powerful.


Agreed to a point. Fortunately, there appears to be only one notch, measured from where I sit all the time. The room has parallel walls but it's large and odd shaped. The room is 34 feet long by 22 feet wide. The system shoots across the width of the room (22 feet). My listening position is 14 feet away. The room has a few extensions where other furniture is placed. The floor is carpeted and the ceiling is acoustic tile, suspended ceiling, 7’ 4” in height. The walls are somewhat broken up by art work and taller objects. I could probably stand to do some treatments.

A long time ago, I remember reading a line out of an Altec Lansing manual. Their philosophy at the time was, “Opposite walls, opposite materials.” By the way, I’m using two Altec A7-800 speakers in their domestic enclosures for my front L/R. In their day, they were known as the Valencia. I did watch a YouTube video about room nodes or suckouts as you call them. He said the same thing as you. The only way to get rid of them is to add another sub aimed in the opposite direction. He also said to never set the listening position at the half way point in the room. You're just asking for trouble. I guess I partially solved the problem with the filter, which will work as long as I don’t alter my setup. For other listeners, it's a different story.

Lots of great info. Thanks again!


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