# Balancing /Equalizing dual subs



## corock (Sep 7, 2009)

I just got my second SVS PB13-Ultra and I'm about to embark on the task of balancing and equalizing them in my room. I've read a lot of posts in here and tried to soak up as much information as I can. I have a plan in my head, but I'm a newbie and want to make sure I'm going about this the right way so I don't waste a lot of time going down the wrong road. You guys have so much more knowledge than me, so I want your opinion of my plan. 
First the layout. My main listening position is dead middle at the back of the room. The subs are in opposite back corners of the room facing the middle. They are equadistant to the main listening position (PS. this is the only location they fit and stacking is not in the WAF realm). 
The first thing I was going to do is use REW and my BFD 1124 and create a filter for each sub to get a flat response independantly. 
Next, with the BFD filters in place, set my AVR volume to 0.0 with sub trim at +1 and use a SPL meter to get the subs individually balanced with the mains at 75 dbs. At this point using the subs' gain control to acheive the desired SPL. 
Once that's done run both subs and adjust the trim level down so that combined they read 75 dbs. Now use REW and the BFD to equalize the combination of the two. 
I like to create a reference curve for movies and a house curve for music. I'm also told that the phase for the subs can be left at 0 since they are equadistant from the main listening position. Jack from SVS got me on track on how to balance the subs with each other. I just want to make sure the whole procedure makes sense. I would appreciate any opions on something I might be doing wrong or missing.


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## Moonfly (Aug 1, 2008)

Your AVR shouldnt be putting out 75db when its at 0. FYI, the avr test tones will put out at 75db no matter how the master volume is set, so I would use the test tones to get all your speakers, including the subs, to 75 db. Some people like to run the sub channels a little hotter, and setting them both at 75db, then living with the gain (+3db or so) may prove to be just what you like.

Out of interest, does your AVR have auto setup?

For me, I would manually eq each sub first using the port tuning, room eq (and PEQ if you wish). You can experiment with the phase while you do this, and if your speakers are up front and subs at the back, leaving them on zero may not be best, but experimenting is always the way forward. I would set up each sub one by one, then when your happy, measure them against each other for some final tweaking. After that I would double check the subs combined response with the speakers to see where I'm at and adjust as required, then finally, bring in the BFD to finish off the response curve of the subs to exactly were you want them.

You should only have to adjust your master volume once for each sub as you level check REW before measuring, and once (if necessary) each time you bring the speakers into the equation. Your going to have to use the amps sub trim level to adjust both subs together once you have them set were you want them, so you really need the sub channel on 0 to begin with, and use the subs level gain to get it to 75 db at the listening position with the amps test tone. Once both subs read 75db at the listening position individually, run the test tone again but with both subs on, and adjust the amps sub level trim to bring them down to 75db together if thats your target level, and having the amps sub level trim at -3 or so is common. Once balanced you can then do the manual EQ bit on each sub to get the flattest response, and that should be your target, with both as close to each other as possible. Once your happy, measure the combined response and use the bfd to augment the combined curve to your desired shape. Dont forget to keep an eye on any differences your speakers might make. There shouldnt be much after the initial setup and the phase is correct etc, but I always double check.

I may be a bit to particular for some with all the double checking, but I find it brings me ultimate peace of mind and helps when it comes to finally leaving the eq'ing alone, which can be difficult :R. I think Ive basically repeated what you said, but posted just to be clear :T

BTW, stacking subs basically makes them act as a single sub of twice the size, spreading them out across your room is the best way to get the smoothest response from them. Its also the best way to ensure there is no directional bass, especially if your want to try experimenting with higher crossovers than 80hz.


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## tonyvdb (Sep 5, 2007)

I agree with Moonfly, you will need to re run your receivers auto room correction again before you go any farther. Have both subs connected and do all other adjustments after the fact.
Is your seating directly against the back wall?


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## Moonfly (Aug 1, 2008)

tonyvdb said:


> I agree with Moonfly, you will need to re run your receivers auto room correction again before you go any farther. Have both subs connected and do all other adjustments after the fact.
> Is your seating directly against the back wall?


Just do the manual balance and eq (using the PBU's in built tune options) on your subs first, then run your amps auto setup. If youve done good, the auto setup shouldnt do a great deal to your subs, although it will do something. You can use that as a kind of confirmation your going the right way with your own eq and balancing attempts.


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## tonyvdb (Sep 5, 2007)

I guess we should know what receiver he is using, that will help us to know how accurate the auto room correction is going to be with the subs.
I agree that it should already be close if it was done properly the first time.


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## corock (Sep 7, 2009)

I'm using a Denon 4308ci with Audyssey Multieq XT. My sitting position is against the back wall and the subs are directly to my left and right 10' in the corner facing me. I assume you want me to run Audyssey first to flatten the subs response, instead of my plan to use BFD to flatten the responses before I set their individual levels.


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## tonyvdb (Sep 5, 2007)

corock said:


> I'm using a Denon 4308ci with Audyssey Multieq XT. My sitting position is against the back wall and the subs are directly to my left and right 10' in the corner facing me.


Can you move you seating forward? Having it directly against the wall is going to cause issues with reflection.


> I assume you want me to run Audyssey first to flatten the subs response, instead of my plan to use BFD to flatten the responses before I set their individual levels.


Yes that would be my suggestion. Use the BFD to flatten after Audyssey has done its job.


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## Moonfly (Aug 1, 2008)

Turn Audyssey off. Reset trim levels for all speakers to 0. Balance sub levels using the in amp test tone, set one sub at a time, then adjust together with the amps sub trim to bring combined response to 75db if desired (although Audyssey will actually take care of this anyway). Then use REW to manually improve sub response using the subs own manual eq features. Then re-run Audyssey for final system setup. To finish off, you can then use the BFD to tweak the combined response of the now eq'd subs to either make final improvements, save some curve preferences or both.

Hope that helps.

FYI, my seating is against my back wall, and I dont find it a major issue. You will get more room gain against the wall, bass will be quieter closer to the center of the room.


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## corock (Sep 7, 2009)

Thanks guys. One question. If i set the subs' level before I flatten the response, won't the level be set to any peaks I have in the unadjusted frequencies?


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## corock (Sep 7, 2009)

Oh, I forgot. I cannot move the seating position forward, so I have to live the reflection issue.


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## Moonfly (Aug 1, 2008)

corock said:


> Thanks guys. One question. If i set the subs' level before I flatten the response, won't the level be set to any peaks I have in the unadjusted frequencies?


You set the subs levels using the amps test tone, so that isnt an issue. Then when Audyssey runs, it will adjust trim levels and account for the peaks for you as best it can. You can then employ the BFD to finish off as you desire.


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## tonyvdb (Sep 5, 2007)

The pink noise that Audyssey uses is not affected by the EQ that it uses it will still send a flat pink noise signal.


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## corock (Sep 7, 2009)

Thanks Moonfly, you saved me all the work of flattening out the individual subs prior to running the test tones and setting the levels. I thought any frequency peaks in my room acoustics would be present when running the test tones resulting in a 75 db reading at the peak.


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## Moonfly (Aug 1, 2008)

corock said:


> Thanks Moonfly, you saved me all the work of flattening out the individual subs prior to running the test tones and setting the levels. I thought any frequency peaks in my room acoustics would be present when running the test tones resulting in a 75 db reading at the peak.


Thats what the forums are for. If you did the BFD first, there would be a chance Audyssey would undo a little bit of what your were trying to achieve, especially if your trying to dial in a curve based on a preference rather than a flat response. Audyssey aims for accuracy, which it does by aiming for as flat a response as possible, and correcting time domain issues.

Thats why your have to do the BFD bit last. That way, if you want, you can simply turn off the BFD and your back to flat as Audyssey sets it again. The reason for doing the manual bit before Audyssey, is your basically helping Audyssey out as best you can to maximise the end result.


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## corock (Sep 7, 2009)

Tony,
I wasn't concerned about peaks created by the Audyssey eq as much as peaks caused by my room.


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## corock (Sep 7, 2009)

I can't wait to get home and get to work. I never would have used the subs eq system to flatten the response before running Audyssey and BFD...nice tip. Tony...it was your original post on the PB13 that got me interested in them and I can't be happier with them. I was happy with just one, but two of them is incredible. I got the second because I had a terrible 30hz dip at my main listening position and several other "holes" in my room. I haven't done any work on the pair yet as far as using REW and BFD. The raw power of the pair is unbelievable I can't imagine what they'll be like properly adjusted.


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## brucek (Apr 11, 2006)

> I never would have used the subs eq system to flatten the response before running Audyssey and BFD


Most people (I believe) equalize their sub(s) first before running Audyssey. Audyssey doesn't do a great job if there are drastic peaks to resolve. It's far better to tame the large problems with EQ first and then run Audyssey. It then does a very nice overall smoothing job.

brucek


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## Moonfly (Aug 1, 2008)

corock said:


> I never would have used the subs eq system to flatten the response before running Audyssey and BFD...nice tip.


I always aim for flattest response first. Measure the different tune modes first and find the one that works best. When selecting the best, keep in mind that a low end boost can be tamed with the room comp, so the flattest responding tune mode might not be optimal when considering the room comp switch, although it usually will be. Once the tune mode is set, then look for the worst peak, and target it with the on board PEQ. Look for a good balanced equalization rather than trying too hard to totally iron out the peak (if there is one of course), and then let Audyssey do the finishing off.

Have fun, and post back here with your results for us. If you need help along the way then just shout :T


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## corock (Sep 7, 2009)

I got confused by "eq" in posts I've read in the past, assuming it refered to a BFD or some other outboard equalizer. I completely ignored the SVS eq system on the subs amp and flattened the response with my BFD first then ran Audyssey. Of course that created a huge issue when using a house curve for music, as Audyssey would try to flatten it back out. So I've just been leaving Audyssey off when listening to music. I think I've got it straight now. Balance levels, flatten with Subs' eq, run Audyssey, then use BFD to further tweak curves.


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## brucek (Apr 11, 2006)

> Audyssey would try to flatten it back out


In my experience Audyssey seems to add a house curve. My measurements with Audyssey dynamic EQ on and off show that it certainly adds a boost at moderate listening levels (just as loudness controls use to accomplish).

brucek


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## corock (Sep 7, 2009)

brucek said:


> In my experience Audyssey seems to add a house curve. My measurements with Audyssey dynamic EQ on and off show that it certainly adds a boost at moderate listening levels (just as loudness controls use to accomplish).
> 
> brucek


I listen to music at loud levels, so I turn off the deq and use a house curve. The one measurement I took with Audyssey applied ontop of my house curve showed the response boosted between 50-80hz and flattened below 50hz. I'm going off memory so the 50hz is an estimate.


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## Moonfly (Aug 1, 2008)

corock said:


> I got confused by "eq" in posts I've read in the past,


In truth, 'eq' refers to no device at all. Its simply the process of optimizing and equalizing your system to suit your room, with each room being unique.

How you go about the eq'ing is entirely upto you, and can consist of simply moving your speakers to a different position. Generally, we would determine first how a person is eq'ing their system before advice can be offered.

Be sure to let us know how you get on.



corock said:


> I listen to music at loud levels, so I turn off the deq and use a house curve. The one measurement I took with Audyssey applied ontop of my house curve showed the response boosted between 50-80hz and flattened below 50hz. I'm going off memory so the 50hz is an estimate.


The closer you get to 0 on your amp the less dynamic actually eq does anyway. What you do is probably best though, as what sounds best to you is what is best :T


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