Subwoofer Volume (1 Viewer)

[ChrisGlass]

Here's another Newbie question. When setting up a subwoofer, how does one get the correct volume. There are two level controls, one on the receiver and one on the subwoofer. Where should the receiver level be when calibrating the subwoofer.

Thanks for your help.

Chris

 

[Rob Dawn]

That's a very interesting question, because recently I have read 2 different people in 2 different threads say the exact oppositeon this subject.
In the following thread, Vince Maskeeper says: "If possible, run the amplifier unit all the way open and use the sub control in the receiver to adjust the sub level. However, if you cannot calibrate with the amp level all the way up, go ahead and turn it down to where you need it to be to calibrate."
http://www.hometheaterforum.com/htfo...threadid=58241
But, in the next thread, Harold_C says: "You want the hottest possible signal coming from the receiver to the sub and the least amount of gain in the subwoofer amplifier to reduce your noise."
http://www.hometheaterforum.com/htfo...threadid=62446
Now Harold was talking about reducing a hum in a powered sub, so maybe he would agree with Vince that the ideal setting is with the sub's volume all the way up and set the reciever's sub setting as low as you then need.
Maybe Vince and/or Harold will pop in here and enlighten us more!
Rob

 

[Mark Hobbs]

I was unable to calibrate with the sub volume all the way open, as Vince suggests. I set it to exactly half way (so I could easily remember right where it is supposed to be) and then calibrated using the fine-tuning on the receiver just the same as you do with all the other speakers.

 

[Bob McElfresh]

A few months ago, someone circulated a report that showed the LFE output on many high-end receivers produced 5-7% distortion, while advertising something like 0.07% distortion for the speaker outputs. They tested units no longer being produced and apparently, this has gone on for years.
Does it matter? No. While you CAN tell as little as 1% distortion on your main speakers, us humans are very insensitive at sub frequencies. So this is why they have done this for years and nobody noticed.
But under the heading of "getting the most accurate output possible", they suggested you leave the receiver level down and use the intensity knob to adjust the levels.
The article noted that the Yamaha A1 (my receiver) started distorting with the sub level going above -6 (it's a scale from -10 to 0). So this is where I pegged my LFE output.
(Either way, you probably wont notice the difference )

 

[Johnny Mac]

Along the same lines, Sound and Vision said the Yamaha RX-V1000 worked well at any setting below -8. scale is 0 to -20. I have mine set at -10.

SV recommends setting a reciever at 25% of its total. I have tried all different settings and couldn't tell a difference at my listening levels to be honest. If the gain on your sub amp is at about halfway, you should be fine.

 

[steve nn]

I have tried the works.I think I like the 1/3to4/10 on the sub and -4to+4 on the receiver.It has a range of -10to+10.

 

[Harold_C]

Johnny Mac:

What Sound and Vision is doing with their subwoofer test is not particularly realistic.

I'm not sure that I can explain it fully, but the issue of clipping or distortion at the receiver subwoofer's output should not be an issue in normal operation.

Their reference levels are set with a -20dBFS digital signal input and a 1 watt into 8 ohms output. This is the Avia calibration test tone level and, at full Dolby reference playback levels, should produce 85 dB from each speaker at the listening position. Assuming 8 ohm speakers with an efficiency of 91 dB/1w/1 meter, this will produce the required Dolby reference level at a distance of 2 meters. So I don't have any problem with their reference levels.

Now, for their subwoofer test, they hit the subwoofer with a sustained continuous tone at the absolute maximum possible digital signal (0 dBFS) simultaneously redirected from all five channels at 31 Hz. That is an absolutely BRUTAL test. I doubt very much than any recording engineer (who wasn't unconscious from Jack Daniels) would ever record full-scale 31 Hz bass in all five channels simultaneously. And, even if he did, it wouldn't be a sustained sine wave. If you played that back with any of your speakers set to large, it would blow the cones across the room.

Even under these conditions, the subwoofer output of the receiver produced a whopping 6 volts of output with only 0.004% distortion. Amazing, really. Unless you had the sensitivity knob on the back of the sub turned way down, that 6 volts would be driving the subwoofer into such hard clipping, the subwoofer would be belching smoke and making ungodly clanking sounds as the voice coil slammed into the motor structure.

Now, let's look at what would be happening to your other five channels. To reproduce a full-scale 0 dBFS digital signal at 1khz at their reference levels, would require somewhere right around 200 watts continuous RMS per channel. Since, according to their test report, the receiver started clipping at 78 watts, you would be hearing extreme distortion (for a few seconds until the speakers blew up) at the point where the subwoofer output starts to clip with 6 volts output.

In short, playing continuous tone sine wave full-scale 0 dBFS full-scale digital signals at Dolby reference levels is an unrealistic test. At best, you would hope that your system would play instantaneous peaks at those levels (neither the Yamaha nor any other "100 watt per channel" receiver can do even that). No way in heck any part of the system could handle sustained sine waves at those levels. Distortion from the subwoofer outputs would be the LEAST of your worries since you would be looking at five blown loudspeakers and trying to clear the smell of burned voice coils out of the room.

Those of us who have done speaker testing with a B&K chart recorder and swept sine wave tones know that you NEVER, EVER dump more than a watt or so into a speaker with sine waves. I'll never forget the time I was doing a speaker clinic where we tested speakers people brought in and gave them a graph from the chart recorder to take home. I screwed up and set the volume too high and watched the pained expression on some poor guy's face as the tweeter on his pride and joy emitted a little curling stream of blue smoke. Do that with 200 watts and you better have some fire extinguishers at the ready.

Not to mention your ear drums. If the amplifiers and speakers could actually do what Sound and Vision was testing, you would be delivering a continuous sine wave of 105 dB from each of five speakers at your listening position. With five speakers playing simultaneously, that is in excess of 110 dB with a continuous sine wave. That would be like blasting a continuous tone from a compressed air horn (from a truck or a boaters emergency kit) in your living room. Your ears would be ringing for a week.

 

[Harold_C]

Now Harold was talking about reducing a hum in a powered sub, so maybe he would agree with Vince that the ideal setting is with the sub's volume all the way up and set the reciever's sub setting as low as you then need.

No. I probably wouldn't agree with that under any circumstances. All the way up on most powered subwoofers would probably mean that a signal considerably less than 1 volt would drive the subwoofer amp into hard clipping. Considering that most of the A/V receivers put out 5 to 9 volts before clipping at the sub output, you would not be able to balance the system with the sub wide open and, even if you could, it wouldn't be a proper gain structure.

People in pro sound (and elsewhere) have done a lot of work on proper gain structures over the years and come to pretty firm conclusions.

Ideally, you would like every part of the playback chain to clip at the same time. When we are talking about a regular preamp and a regular amp, you generally want something like a 3 to 1 gain structure. If the preamp puts out 3 volts RMS on a steady signal at the onset of clipping, you would set the amp to start clipping with a 1 volt input -- for reasons that have to do with volume control tapers and the relationship of peak to average levels. If your pre-amp puts out 6 volts unclipped, you would generally set your amp sensitivity for full power with a 2 volt input.

Some consessions have to made to account for the fact that you are trying to balance the subwoofer to the rest of the system in a surround system, but you certainly don't want to crank the sub volume knob so that the sub clips with half a volt when the receiver is putting out six volts. This would result in gross clipping and distortion from the subwoofer.

Likewise, you don't want to turn the receiver's sub level way down, because that is going to make any noise picked up on that long RCA cable louder than it needs to be relative to the signal level -- the subwoofer is just fat, dumb, and happy -- it will amplify the noise just like it amplifies the signal.

As a practical matter, you don't have a whole lot of choice. You've got to turn the sensitivity knob on the subwoofer down to a point where you can calibrate the system so that the subwoofer level on the receiver is somewhere in a fairly narrow range between say 0 dB and -10 dB. You'd prefer not to have it at the -10 dB extreme, because then you wouldn't have any adjustment range left on the receiver and it would be a pain to calibrate the system if you move the subwoofer. As a practical matter, whether you set the knob on the sub so the system calibrates at 0 dB or - 8dB on the receiver sub setting probably isn't going to make much difference.

Given a choice, I would tend to go for the hotter signal from the receiver and the lower sensitivity on the sub. I don't have a choice, because my subwoofer amp doesn't have sensitivity adjustments. So I use the receiver's sub level settings exclusively to balance the system. When matched with the receiver's amplifiers, I had the sub set at -6 dB. Dolby reference levels were at -15 dB on the volume knob. With the a/d/s/ PH6 multi-channel amp I'm currently using, my sub is set at -1 dB to balance the system. Dolby Reference levels are 5 db higher (-20 dB) on the volume knob. In both cases, the output of the main speakers and the subwoofer ends up being exactly the same.

 

[ChrisGlass]

Thanks guys!! You've obviously done this once or twice I tried the full volume on my subwoofer, and levels down on the receiver (ONK 575x -12+12) to about -10 and everytime I switched sources, I heard a rather large THUMP out of the sub (Paradigm PS-1000). Needless top say that idea went out the window. I lowered the sub volume to about have and adjusted accordingly with the rec. levels. Now sounds much better. I still need to calibrated the levels, but trying to find a decent SPL meter in Canada is like pulling teeth. Last one I saw was about $110 Can.
Thanks again for all for insightfull info.
Chris

 

[Bill Kane]

Chris, that CAN. price likely is for the more expensive Radio Shack DIGITAL meter; most use the ANALOG model at US$39.

bill

 

[steve nn]

Harold,

Thanks for taking the time.I have thought running the receiver a little hot and sub gain on sub down had best results for me.

 

[Jeff Bamberger]

I am so glad I found this thread. I calibrated a long time ago using a friends SPL and VE. Now I have my own SPL and waiting on delivery of Avia.

I know that my knobs have gotten moved around since they were set and I "think" I may have gotten them back to where they were, but I can't be sure. I am going to go with the "set the gain to half" route and calibrate from there!

Thanks again to this wonderful forum for helping not stress out about this obsession!

 

[DougO]

Harold: How do you like the a/d/s/ PH6 amp?

 

[Harold_C]

How do you like the a/d/s/ PH6 amp?

It's a seriously overdesigned multichannel amplifier. Rated at 6 x 70 watts, but it does a good bit more than that. It has a huge power transformer, 132k mF of storage capacitance, all discrete outputs, no current limiting, very low negative feedback. It's an interesting package -- 100% fan cooled with no external heat sinks at all.

I very much doubt that a/d/s/ ever sold many of them at $2500 each and I would bet they lost money on every one they did sell. The components and the packaging of the amp made it hideously expensive to build.

I'm using 5 of the 6 channels to drive four B&W DM303's and the matching center channel. It is really a fantastic surround sound amplifier. Very strong dynamics and headroom. It's clean as a whistle and images very nicely.