Stereo subwoofers with RoomEQ & a FBQ2496

**Teejoo** · **02-22-07, 02:37 PM**

Hi, I've always used John's Room EQ wizard with my Tag set with great results. Now I've sold the Tag and bought a Lexicon MC12 V5 EQ.
I'm not that impressed with the EQ function of the Lexicon, mainly for the sub. I think it's caused by the fact that you can't tweak it yourself, but I'm not sure.
That's the reason I decided to order a FBQ2496 for the subwoofers wich I can configure with the RoomEQ tool again

. I want to drive 2 subwoofers with it, L & R channel.

If I use the MIDI connection to download the filters etc. Is it possible to do this seperately for each channel if I select on the Behringer the correct channel? I'm planning to make a measurement for each subwoofer. Or is it wiser to make one measurement for both subs together and use the same filters for both?

**Hakka** · **02-22-07, 06:47 PM**

I have 2 indentical subs in a symetrical room layout, I used the Behringer in couple mode (same filters to each channel). How do you have your subs positioned? If they are symetrical or placed together you should be able to EQ them together.

REW will let you set each sub independantly if you want.

What subs are you using?

**Sonnie** · **02-22-07, 08:22 PM**

What you may want to do is experiment with this a little. I've had excellent results using a pair of subs. I only use one input/output of the BFD, splitting from the BFD out to each sub, but as Hakka suggest, you can use both inputs/outputs and couple the channels.

Initially my subs were symmetrically placed, but in order to eliminate a nasty dip I moved one to the rear. I hardly need the BFD now, but when I have used it to tame the small anomalies I have, it has worked fine using one set of filters for both subs, which is what you are trying to accomplish. My point being, I'm not even sure if the subs being non-symmetrical matters in determining whether you use one channel for both subs or each channel independently. To me, it seems like it would be difficult to adjust each one independently and get a smooth response when they are re-combined. It makes sense to me that combining them (or using the couple mode) would work better in any situation with two or more subs. For instance, if you have a peak at 50Hz measured from the combination of subs, then filtering it out of both subs should accomplish the end result, whether they are symmetrical or one is in the corner and one in your lap...

**Hakka** · **02-22-07, 09:43 PM**

Quote:

Sonnie wrote:

I only use one input/output of the BFD, splitting from the BFD out to each sub, but as Hakka suggest, you can use both inputs/outputs and couple the channels.

Just to clarify, my sub out is split into both channels of the BFD, and I have the same filters in both channels (left and right). Before I used REW I used couple mode so I only had to manually enter the filters once, the end result is the same - both channels have identical filters. If you have the BFD in couple mode and you send filters via MIDI, it will drop out of couple mode when you select the right/left filter bank.

As Sonnie suggested, even if your subs are not symetrically placed your probably still better off using the same filters for each channel. A while back I EQ'd each sub independantly, the response curves were ruler flat, once I combined the two there were humps and dips everywhere.

Harry.

**Teejoo** · **02-23-07, 06:24 AM**

@ Hakka: At the moment I only have 1 sub, an older B&W. I am planning 2 SVS SB12-Plus subwoofers in the near future

It indeed makes sense to measure the subs together and set the same filters for both channels.

About using midi: So if I'm correct the downloaded filters are applied according to the setting on the Behringer? (L, R or coupled mode)

**JohnM** · **02-23-07, 11:02 AM**

Hi Teejoo,

Long time no speak

When you download via Midi you are prompted to choose whether to load the filters into the left or right banks.

**Teejoo** · **02-23-07, 12:40 PM**

Hi John,

Indeed it's been a while! (new house in the past year, so very busy). But as you can see I'm very happy that you made the roomEq software available for other stuff than TAG!

Thanks for answering the midi question. I'll have a play with it as soon as I have all the kabels.

**Teejoo** · **02-24-07, 04:52 AM**

Quote:

Sonnie wrote:

My point being, I'm not even sure if the subs being non-symmetrical matters in determining whether you use one channel for both subs or each channel independently. To me, it seems like it would be difficult to adjust each one independently and get a smooth response when they are re-combined. It makes sense to me that combining them (or using the couple mode) would work better in any situation with two or more subs. For instance, if you have a peak at 50Hz measured from the combination of subs, then filtering it out of both subs should accomplish the end result, whether they are symmetrical or one is in the corner and one in your lap...

The thing is that I really use a stereo sub output from the Lexicon. I set my fronts at 70 or 60 Hz. The question is how much stereo info is in the sounds below 60 Hz? Using the same filters for both channels sounds ok when a mono signal is presented to both subs. What would happen if the signals for L & R are not the same?

Perhaps it is still better to filter each channel seperately and take a combined measurement afterwards. This measurement I can use to check if the combined results create a new problem. What's your idea on this John?

**brucek** · **02-24-07, 09:23 AM**

Quote:

What would happen if the signals for L & R are not the same?

It's not the source material that determines the equalization required, its the rooms interaction with the sub itself.

But aside, I think you'd be lucky to have two subs that were not co-located exhibiting the same response in a room. Two subs should be cabled to be able to enjoy individual BFD channels so the filters can be unique to each sub. If you get lucky and they're the same, fine, but at least you leave the option open to tweak each sub differently...

brucek

**Wayne A. Pflughaupt** · **02-24-07, 10:35 AM**

Quote:

The question is how much stereo info is in the sounds below 60 Hz?

Not much, really. Back in the early days of stereo you’d sometimes find they dumped the bass guitar in one channel only, but they caught on pretty quick that that wasn’t a good way to do things. I’ve only seen a couple of songs since then that actually did something “stereo” with the bass – not that I’ve heard everything there is to hear or anything...

Regards,
Wayne

**Sonnie** · **02-24-07, 05:54 PM**

Quote:

brucek wrote:

But aside, I think you'd be lucky to have two subs that were not co-located exhibiting the same response in a room. Two subs should be cabled to be able to enjoy individual BFD channels so the filters can be unique to each sub. If you get lucky and they're the same, fine, but at least you leave the option open to tweak each sub differently...

I'm gonna say you would be challenged to ever get a flat response trying to filter each sub individually. How would you know which sub is causing a peak? You can measure them individually but when you measure them together you are gonna get a completely different response and it would be impossible to determine which one is causing what, would it not?

Anyway, my two subs right now are not co-located, one in front and one in rear. They are on one channel of the BFD. The small peak I have in my response I can filter out easily with the one filter, but I have no idea which sub is causing it because when I measure each sub individually, that peak is nowhere to be found.

Maybe I'm not doing something right, but I can totally flatten my response with the one set of filters.

**brucek** · **02-24-07, 05:59 PM**

So, what will you do when you install the Big Boy and you will be battling subs without identical response? Surely you can't think one set of filters will do?

What's your plan?

brucek

**Sonnie** · **02-24-07, 06:11 PM**

I'm battling subs without identical response now and one set of filters is fine. The two subs I have may have identical anechoic response, but sitting where they are at now they are completely different. When I place them both in the front corners, they are exactly the same, but separated front to back, not even close... not to mention one is crossed over at 80Hz and the other at 60Hz.

Of course I really don't even have to have the BFD as it is now and I hope I won't when the behemoth is in place either. If the BFD is needed, I firmly believe I can use one set of filters and smooth the response.

**brucek** · **02-24-07, 06:20 PM**

Quote:

I firmly believe I can use one set of filters and smooth the response.

Yeah, interesting for sure.

I wonder if using one set of filters to produce a flat response for two subs (that were exhibiting different responses) would make the response more seating position sensitive?

brucek

**Sonnie** · **02-24-07, 06:40 PM**

That, I'm not sure about. I never measured anything other than from my listening position for the setup I have now, but I do remember I had a serious 15db or so peak at 30Hz measuring on my back row when I had both subs up in the front corners. I probably should measure that back row now, but I'll probably just wait until I get the behemoth in there.

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