# how to balance Sub volume with speakers?



## trcns (Sep 15, 2015)

I have two different branded subwoofers, one from REL and other from PSB. My front speakers are B&W 802D's.

I am trying to balance the volume of Sub's with speakers using REW SPL Meter with REW's signal generator using sign wave.

Keeping the volume constant on AVP, I balanced my sub and speakers at 40 Hz, so signal from subs and speakers have same SPL. Now if I use 30 Hz sign wave, Sub sounds louder than speakers, at 50Hz and 60Hz Speaker's SPL is higher that both subs. Where should I balance them, any rule of thumb or best practices?

Second Problem is with the sub's themselves, if I change the frequency the SPL is not even from subs.

Any suggestions? Please help.


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## DqMcClain (Sep 16, 2015)

trcns said:


> Keeping the volume constant on AVP, I balanced my sub and speakers at 40 Hz, so signal from subs and speakers have same SPL. Now if I use 30 Hz sign wave, Sub sounds louder than speakers, at 50Hz and 60Hz Speaker's SPL is higher that both subs. Where should I balance them, any rule of thumb or best practices?


*TL/DR - Try 60Hz to 80Hz... ish. Somewhere in there will probably sound decent. Painful details to follow.
*
That's normal. What you're hearing/measuring is the effect of the crossover point between the L/R speakers and the subs. You do not, in fact, want even SPL from L/R and subs in all of their usable ranges. 

Lowering the crossover point (dropping the frequency) will reduce the amount of bandwidth being delivered to the subs, and consequently increase the bandwidth being delivered to L/R. 

As frequency is reduced (and wavelength is increased), sound becomes proportionally _less_ directional. Somewhere in the neighborhood of 60Hz to 80Hz, you will notice that the low end of the signal seems to originate from the L/R speakers. This will give you a better sense of "imaging", or ability to locate the source of a sound. If your subs are near your L/R speakers, this may not be an issue... but often the optimal placement of subs in your room puts them someplace odd in terms of a stereo (or multi-point suround) image. If your crossover point is too high in this case, (above, say, 100Hz) it will seem that low frequency things (bass lines/kick drum in music, LFE channel in movies) are coming from the wrong place. It can be very distracting. 

If you allow the subs to cross over at a point _higher_ than the bottom end of the L/R speakers (i.e. your crossover points don't match and are overlapping), you are very likely to cause destructive interference which will have an adverse effect on the low-end response of your system as a whole. No amount of EQ will fix this problem, as it is a side effect of wave propagation in elastic media (i.e. air). 

Also, if there is a gap between your crossover points (top end of subs is well below the bottom end of L/R) you may have a dip in your system's response. Smoothing this dip out with EQ is counter-productive, and may introduce phase response issues... also impossible to fix with EQ, as this is a time-correction issue and not a frequency response issue. 


As for the mismatch in subwoofer make/model... no amount of tinkering with crossover points and EQ curves is going to make them behave the same. Repositioning them in the room might even things out a bit, but that's a game of trial and error mostly.


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## willis7469 (Jan 31, 2014)

I would use the pink noise generator, or the one in your avr. Sine waves usually aren't for level matching. Turn on the one closest to your mains(if they're the same I don't think it will matter). After you've set all channels to 75, set the first sub to about 72. Then turn off the first sub and set the second one to 72. Now turn on the first sub, so both are now on. They should read about 75. If they're too high, repeat the first steps at a lower level until the combined is 75.(I set my subs at 80 compared to the mains at 75) I would have the sub trim in the avr at -5.(first)Then do the levels manually on the subs. That way you can trim them in avr. Too far in the minus, and the subs might not turn on until the volume is high. Too far into the plus can introduce distortion into the signal.


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## willis7469 (Jan 31, 2014)

After you do that. Play a sine wave at the crossover frequency and move the phase knobs(or the 180/0 switch). Look for the position that shows the highest output. That should reflect a smooth(ish) transition in the crossover region. Then measure with REW and see whatchagot.


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## Lumen (May 17, 2014)

^ +1
Willis' tips helped me smooth out a misbehaving crossover region, except I used REW to play/measure limited-bandwidth sinewave sweeps. For example, set REW's signal generator for a 75dB sine wave from 25Hz to 100Hz; start with phase at 0deg. Activate the signal generator sweep/measurement. Increase phase by 15deg. Repeat until best curve is found.


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## Lumen (May 17, 2014)

trcns said:


> I have two different branded subwoofers, one from REL....
> Keeping the volume constant on AVP, I balanced my sub and speakers at 40 Hz, so signal from subs and speakers have same SPL.


Just guessing here, but that sounds like REL's starting point for sub integration using a high-level speaker connection (as recommended in their user manuals). How are you connecting your REL? I ask because this "secondary" connection changes the way the sub interacts with the mains. Also, the REL's crossover control only works for its high-level input, not for its LFE input. The high-level connection, along with its crossover and volume controls, allow the sub to take on the same bass "character" as the mains (according to REL).

In a traditional HT system, the sub and mains are crossed-over (usually at 80Hz) to relieve the mains and their amps of heavy bass duties. In such a system there is little overlap between the two. In a REL system where both high-level and LFE inputs are active, the sub and mains are still crossed over; but now bass intended only for the mains is "leaked" to the sub with potential overlap. This may not matter if mains are set to SMALL, but if set to LARGE per REL's instructions then a lower crossover point is in order. Here again I'm just guessing that's why you're concerned with 40Hz (close to the lower limit of the smaller REL subs). And I'm also guessing that blending your subs is complicated by the mismatch (one sub fed full-range, while the other is fed only LFE).

So to wrap up... Consider disconnecting the REL's high-level input if you're using it. That way both subs will be getting the correct signal and crossover from the processor. If you'd still like to use it, then I can only suggest to set the REL's crossover by ear (maybe someone else has experience using REW instead).


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## trcns (Sep 15, 2015)

When I use a pink noise signal, the SPL reading is very confusing and I cannot find a definite value, that's why I used sine wave.

What should be my crossover set to? when 

SUB 1 (Rel G1)has Lower Frequency Response in Room: -6dB at 15Hz, using a high-level speaker connection CrossOver at 35Hz and using .1 LFE crossover at 80Hz for surround

SUB 2 (PSB) Frequency Response: 28-150Hz connected via LFE.
Sensitivity: 91dB - 93dB 

Speakers (B&W 802D)
Frequency response: 34Hz–28kHz, ±3dB

The AVP is configured at 80Hz

Both Sub's are in the front, Left and right corners behind the speakers.


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## Lumen (May 17, 2014)

trcns said:


> What should be my crossover set to?
> 
> SUB 1 (Rel G1)has Lower Frequency Response in Room: -6dB at 15Hz, using a high-level speaker connection CrossOver at 35Hz and using .1 LFE crossover at 80Hz for surround
> 
> ...





DqMcClain said:


> *TL/DR - Try 60Hz to 80Hz... ish. Somewhere in there will probably sound decent.
> *


^ +1
If you can, first experiment with sub locations (do a sub-crawl)
Disconnect the REL high-level input.
Set PSB sub crossover to maximum.
Experiment with processor crossover between 60 and 80Hz.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Like Willis noted, sine waves are not good for level setting, because they do strange things in a room, acoustically. For instance, have you noticed the way the perceived volume of the signal varies drastically as you move about the room?

That’s the reason broadband pink noise is used for level setting. It’s a random signal that varies somewhat in level, which means you don’t get a steady reading from a sound level meter, which I’m sure accounts for the “confusion” you mentioned. It’s easy to overcome – just note either the highest or lowest figure that registers (your choice, makes no difference) and use that as your reference. Switching the meter to “slow” response will help.

BTW, judging from the graphs in this review you speakers have significant bass output. This means that you’ll get more lows “bleeding through” the receiver’s high pass crossover than would normally be expected. The effect will be as if the crossover was set to a lower frequency than it actually is.

Regards, 
Wayne


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## tonyvdb (Sep 5, 2007)

I agree with the above comments about not using a sign wave to set levels, on that topic you need to be carefull about playing sign waves as that can cause permanent damage to the subs motor due to heat. 


Wayne A. Pflughaupt said:


> BTW, judging from the graphs in this review you speakers have significant bass output. This means that you’ll get more lows “bleeding through” the receiver’s high pass crossover than would normally be expected. The effect will be as if the crossover was set to a lower frequency than it actually is.
> 
> Regards,
> Wayne


Interesting Wayne, Thats a great point and something many forget. The crossover is not a brick wall cutoff but rather a slope that gradually drops off. Generally an 80Hz crossover will still play down to about 60Hz before its completely inaudible.


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## subterFUSE (May 10, 2014)

Just so I am clear, when you guys are talking about a "sine wave" is that different than an impulse response "sine sweep?"


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## trcns (Sep 15, 2015)

Okay just to be clear

1) I will disconnect all my speakers except one sub-woofer.
2) For REL Sub, disconnect REL's High level input.
3) Using REW SPL meter and Signal Generator, play Pink Noise, frequency range 20Hz to 80Hz from each sub-woofers and document it.
4) Than play Pink noise from both subs at the same time and make sure SPL should not increase more than 5 to 7 db.
5) Next Power off the Sub's, connect one speaker at a time and play Pink Noise from speakers, Frequency range 37Hz to 20,000kz and make sure speakers sound level is equal to sub's SPL.

Please correct me if I am wrong.


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## subterFUSE (May 10, 2014)

I have been using REW's standard IR Sweep Measurements to tune my system, taking multiple sweeps and averaging them together. My question above about "sine waves" vs. "sine sweeps" was basically me just asking if my process for tuning is correct or not, since it was stated earlier that "sine waves" were not the correct way to match levels between speakers.


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## Wayne A. Pflughaupt (Apr 13, 2006)

trcns said:


> Okay just to be clear
> 
> 1) I will disconnect all my speakers except one sub-woofer.
> 2) For REL Sub, disconnect REL's High level input.
> ...


Seems to me that you’re making this much more difficult than it should be. Does your receiver not have an auto-leveling function? I’d just match the two subs’ SPL level with their on-board gain knobs using your Step #3, and then let the receiver do the rest. If you aren’t happy with the results, simply raise or lower the receiver’s sub trim accordingly.

Regards, 
Wayne


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## Wayne A. Pflughaupt (Apr 13, 2006)

subterFUSE said:


> I have been using REW's standard IR Sweep Measurements to tune my system, taking multiple sweeps and averaging them together. My question above about "sine waves" vs. "sine sweeps" was basically me just asking if my process for tuning is correct or not, since it was stated earlier that "sine waves" were not the correct way to match levels between speakers.


Sine waves or sweeps, doesn’t matter. Pink noise is the signal that should be used for making speaker level adjustments (assuming that’s what you mean by “tuning my system,” as level adjustments are the main focus of this thread). Ever see a receiver that uses sine waves as a calibration tone?

Again, not sure I get the reason to go through so much effort for this simple process. Even if you want to adjust levels manually and not simply let the receiver do it, you can adjust levels using a SPL meter and the receiver’s circulating test signal in less time than it’ll take to boot up the computer, set up the mic etc. for using REW. :huh:

(If speaker level adjustment are not what you were referring to when you said "tuning my system" then please ignore my rant.  )

Regards, 
Wayne


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## trcns (Sep 15, 2015)

I got into all this because I did not want to use AVP's auto level function.

I have McIntosh MX121 processor, an year back I tried internal function of balancing the system and in result, I had raise the volume of my system three times play the music at same loudness as it played without balancing. So I am trying to stay away for this feature.


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## jtalden (Mar 12, 2009)

I just sweep each channel and adjust the trims as needed to so they overlay each other well.


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## trcns (Sep 15, 2015)

I am sorry but what is this "Trims" means?


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## jtalden (Mar 12, 2009)

It is basically a volume control on each channel. It can be in any piece of equipment. All AV receivers have ±10dB or so on each channel. In a simple stereo system then the balance control on a receiver or integrated amp can do the job.


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## trcns (Sep 15, 2015)

Thanks every one, Finally I balance my speakers with the subwoofer, I adjusted the SPL level to same for both speakers and Sub's.

Wayne, you were right about using the pink noise from AVP it's much simpler than any other solution.

Not only that it made a difference in sound stage, more than that is a confidence while listening the music that your system is set right without a guess work.


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