# Best Way to EQ 2 Subs?



## Guest (Jun 22, 2006)

I'm getting another PB12-Plus. 

Both subs will be co-located (withing 6ft) at the front of the room. Considering this, is it best to eq both as one sub? or Measure seperately and use the left side for sub 1 and right for sub 2?

Thanks


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## brucek (Apr 11, 2006)

> is it best to eq both as one sub?


Definitely as one when co-located using the same corner........

brucek


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

As brucek noted, EQ them as one sub. Identical subs in the same location will each have the same response. The only difference in adding the second is that maximum SPL will be higher.

Regards,
Wayne A. Pflughaupt


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## Otto (May 18, 2006)

Hi there,

Any suggestions on how to EQ three subs?

I have a sub each in my DefTech 2002s (mains) and an M&K behind the couch. I would not consider any of these as co-located, but definitely not the mains and the M&K. Till now, I've run REW while all are active, applying the same EQ to all three subs.

My latest plan is to get another BFD and EQ the mains separately, maintaining left and right signals through BFD #1. Then, I will EQ the mono LFE channel to the M&K using one channel of BFD #2. I believe this would take three passes with REW, one for each sub.

Till I get another BFD, should I EQ my mains using one channel of my BFD, and the M&K with the other channel?

Thanks and have a great day!


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## brucek (Apr 11, 2006)

> Till I get another BFD, should I EQ my mains using one channel of my BFD, and the M&K with the other channel?


No, check with REW and see which needs equalization the most and then make your decision.

brucek


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## Sonnie (Apr 11, 2006)

I'm thinkin' those Def Techs probably ain't gonna be that peaky in the low end because you don't have them corner loaded... you've got them out into the room more. Typically this creates low areas in the response (your peaks probably won't peak past your normal level of your equalized sub). Of course as brucek suggest, test them and be sure... and I think you'll find yourself equalizing the M&K.


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## khellandros66 (Jun 7, 2006)

The Deftechs are side firing sub, so corner loading isn't gonna help much, plus it will collapse the bipolar image. He can swap the towers to see if having the sub fire inwards or away from each other is best. For me it was inwards that has best results, almost astonishing at that. 

~Bob


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## Sonnie (Apr 11, 2006)

Oh no... I wasn't suggesting he corner load them... just explaining that they probably wouldn't be peaky like a corner loaded sub, therefore might not need eq'ing like a corner loaded sub might. He's trying to decide what to eq.


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## Guest (Jul 24, 2006)

Intriguing subject. I have a BFD and a pb12+/2 and will soon be adding a PB12+ to try to get some extra depth--and hey lets be honest, just more bass. I have a 4600 cubic foot room and run the twin driver monster in the 20hz mode. I am 90% satisfied with movies--I have huge hump at 40hz--I haven't really spent the time to to play with the BFD enough. I am waiting on the new 12.3 drivers to show up and then I will do the final set up on it. I am intrigued by adding a single driver unit because of the 12 and 16hz tuning points. Plus one of those giants is already eating up a huge chunk of real estate in my room. The 16hz on the /2 just didn't sound right and didn't seem to add anything to my usual test scenes (haunting--the cold/door knocking, BFD--F'in Irene, Nemo--Darla, FOF--crash scene, U-571--depth charges, M&C--cannon fire, etc.) For music, which is only about 10% of the time I prefer the 25hz setting--it has more impact. However, a bit of a pain to pull the port plug and flipt the switch and then have to put it back for movies. I am looking to get a bit more of the ultra low feel and perhaps gain some of the chest kick of the higher bass regions for music. I know that adding tactile transducers--which I will probably around christmas, will be a great help in the nether regions. My question is this--very similar to the original question--do I eq them together? the subs are rear placement. I really don't have any options as far as placement goes. They are both going to be behind me and to the outside in the corners. Should I run an "in-room frequency response curve" with both running and split the output from the BFD--essetially treating them as a single sub or a "sub system"? I was originally thinking this is how I was going to do it, but started to think that I might overdrive one in certain frequencies if I have to add a slight boost to a certain frequency. My thinking on this is I might encounter some nasty cancellation issues and the subs might acutually end up "fighting" each other in my listening position(s). As I am typing this I think that if I avoid boosting--which is always the most advisable approach as I understand, I should be fine. Headroom shouldn't be an issue as the single pb12+/2 can crank out some serious db's in my seating position (i have seen 120db on my digital rat shack meterat about 1/3rd on the gain with -6 sub setting on my Denon, master at 0). Does all this sound correct? Has anyone bfd'd (eq'd) multiple subs in one room before? I am sure there are guys in here who have. Does my "sub system" approach make sense? I think it does as it is ultimately the frequency response in the seating position that we are trying to get as flat as possible as low as possible while still sounding good for music. Also, if I do use this approach--shouldn't I have to have both subs set to the same tuning frequency? Is experimentation a good idea in that regard--ie running the single pb12+ at 12hz and running the +/2 at 16hz or 20hz? Then trying something different to see the response, perhaps both at 16hz or 20hz? Any negatives or problems to this?--perhpaps overdriving the single at a lower frequency to try to hang with the higher output level of the dual driver one at higher frequencies? I know that I will set the level of each independently before I start with the BFD so as to not over work one vs the other. Again does all of this make any sense?

I know that was about a dozen questions and/or thoughts, but any help will be greatly appreciated.


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## Sonnie (Apr 11, 2006)

I have two PB12-Plus/2's and I have using one channel of the BFD to equalize both at the same time... works fine for me. One unit is in the front corner and the other against the rear wall.

I had cancellation issues but was able to overcome this by setting the rear sub crossover to 60hz and the front to 80hz. The issues were around 70hz or so, thus this fixed the problem.

You may have to do some experimenting with locations and crossover points.


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## Guest (Jul 25, 2006)

bsheldon said:


> --I have huge hump at 40hz--I haven't really spent the time to to play with the BFD enough. .


I'm just now working to integrate two Hsu subs. My setup is limited by the multi-use room and WAF issues with the Boss. I have limited spots for placement. They are currently on opposing front and rear corners. My first try was with a newly acquired Yamaha RX-V2500, but its YPAO system I don't believe will EQ that frequency range. In fact, I think two subs confuses its phase setup. I also will be (ultimately) adding bass traps, which _must_ be good since everyone touts them. :huh: I'm also strongly considering the acquisition of a Behringer BFD Pro.

But as this post relates to the above......I have a ~10db hump at 60-50 Hz and a 12-15db rolloff from 35-22 Hz. But today I spoke with Dr. Hsu. Amongst some other great suggestions, he gave me an interesting immediate, simple (and temporary) fix. He suggested crossing over one of the subs at 45 Hz, and set my mains to bottom at 60 Hz. (The mains should have a smooth in-room response to 60 Hz.) The net effect should bring the 60-50 Hz peak down 6db. With an increase in gain, the second sub will boost the 20-45 Hz region. Voila....flatter LFE and bass response. I'll try this on Friday when my tech support guru with all the meters, mics, etc comes over.  

Comments?


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## Sonnie (Apr 11, 2006)

This could very well work. I found it took a lot of experimenting to finally get mine right.

I think you'll find bass traps are not going to help you much in that lower region... below about 80hz. A BFD will be your best route to tame any peaks you might have.


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## spearmint (Apr 24, 2006)

This is what I have done with my setup and the use of multiple subs.

My system goes via one channel of a Behringer MX882 where I boost the signal to pro levels, then via Behringer DEQ2496, then via digital to Behringer DCX2496 and then back via five channels of the MX882 to drop the levels back to consumer.

With the DCX2496 I adjust the delays and phase plus any shelving filters I may want for each sub and then do some basic EQ to get it reasonably flat, after each sub has been setup individually I then run them all and use the DEQ2496 to adjust overall in-room response at the listening position.

I know it’s rough and ready but hey it works…


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## reed.hannebaum (Apr 21, 2006)

Similar to Otto, I have 3 subs. My main bookshelf speakers are on stands, and behind each one I have a 15" sealed sub. Then in the rear corner of my room I have an SVS 25-31. The front subs and the mains are driven from the Yamaha receiver front pre-outs, and the SVS from the LFE.

Right or wrong, the way I EQ all this was first to get the front subs balanced with the mains using a Paradigm X-30 crossover & REW. I then used the BFD to flatten the FR. I ran this with the Yamaha set to Direct Stereo, which sends all the bass to the mains and no output to the SVS. 

Next I set the receiver to 2ch Stereo which divides the bass between the mains (including the front subs) and SVS. When I did this the only cancellation I saw was fairly narrow 6-7db dip around 63Hz. There was also a broad peak centered around 25Hz. I have an ART 31 band, 1/3 octave equalizer which I used to make these corrections to the SVS. (by some miracle, 63Hz and 25Hz happen to match 2 of the ISO center frequencies on a 1/3 octave equalizer). I also increased my subwoofer speaker distance setting in the receiver by 1/2' which helped to remove some minor dips and decreased the 63Hz dip.

The BFD and REW make an unbeatable combination. Before I had these tools I used my RS SPL meter and the Rives Audio CD with RS corrected test tones. I spend hours charting FR curves in Excel, but never getting enough resolution in my data to see what was really going on. I am extremely happy with the results I now get; strong, musical bass, not the boomy bass I had before.


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