Baseline graph 15-200Hz sweep - do I need bass traps?

[pclausen]

Here's my initial sweep with the main speakers turned off (only the subs active):



Is my next step to let REW suggest filters for me and send them to my 1124, or do I need to do something else first?

I appear to have a huge peak at my 17Hz tuning frequency. I know that BFD can't do anything below 20Hz, and given that very little content exists (as far as I know) in neither music nor movies below 20Hz, perhaps I don't need to worry about that peak?

I also appear to have quite a dip around 32Hz and I understand that boosting is a no no, so should I ignore it?

That aside, my subs appear to extend well below 20Hz to say the least when taking room gain into consideration!

[brucek]

I appear to have a huge peak at my 17Hz tuning frequency. I know that BFD can't do anything below 20Hz

Perhaps move it out of a corner to reduce some room gain.

I also appear to have quite a dip around 32Hz and I understand that boosting is a no no, so should I ignore it?

It's not very wide really - ignore it.

You should concentrate on bringing the rest of the curve down to the target.

Great response....

brucek

[pclausen]

Thanks Bruce. I'll see what REW comes up with as far as filters to apply to the above response curve. The subs are permanently mounted in the corner of the room firing at a 45 degree angle across the room. You can just make them out in the front left corner in this shot. You can also see from where I took my measurement.



And a close up showing the 18" drivers (each in their own 336 liters net enclosure):

[Wayne A. Pflughaupt]

Nice looking room, Peter.

Regards,
Wayne

[pclausen]

Thanks Wayne! You can probably guess where I spent most of my free time.

I had REW calculate my filters and they look good in that they should result in a response that looks something like this:



But when I tried saving the filter settings out to the BFD, all 24 filters (the red LEDs) began flashing. Power cycling the unit didn't cure it, nor did doing a hard reset (holding down FILTER SELECT and STORE while powering up). I retried it several times, but I just can't get the 1124 to stop flashing all the LEDs. From reading the manual, this typically indicates that all the filters are searching for feedback frequencies?

[Wayne A. Pflughaupt]

Almost forgot, you mentioned bass traps in your thread title. They absorb bass reflection the same way that heavy fabric absorbs high frequency reflections. They can also address deep nulls and peaks to some extent, but the EQ IMO is the best bet for taking care of response. If the bass still sounds “loose” and undefined after equalizing, then you might look into traps.

Regards,
Wayne

[Ilkka]

You might want to adjust the filters manually. That's is a really good looking response and with a little work it can be really flat. Could you show us the response all the way down to 10 Hz?

It is also recommended to run a measurement with your mains on. That way you can see if there are some problems in the crossover range.

BTW, do you have the correction file loaded? I see you're using the older analog version. Its response can be a bit off below 20 Hz...even with Sonnie's correction file.

[Blaser]

The initial FR is IMO excellent... You're very lucky, the dip is quite narrow, you will not note it with your ears.

Can you talk about your subs, they are certaily DIY, can you give us details about enclosure fabrication, dimensions, woofer brands.... cost maybe...

[brucek]

but I just can't get the 1124 to stop flashing all the LEDs.

The easiest method to get past that is to simply choose a program (1-10) that is already enabled for parametric mode (PA). Program 5 would be fine.

Otherwise, simply go through each filter and set its mode to off (OF) or parametric (PA). If you have a new 1124 you'll have to set the filters by hand as the midi has problems with REW.

brucek

[pclausen]

Ilkka wrote:

You might want to adjust the filters manually. That's is a really good looking response and with a little work it can be really flat. Could you show us the response all the way down to 10 Hz?

It is also recommended to run a measurement with your mains on. That way you can see if there are some problems in the crossover range.

BTW, do you have the correction file loaded? I see you're using the older analog version. Its response can be a bit off below 20 Hz...even with Sonnie's correction file.

When I get home after work I'll go ahead and extend the graph down to 10Hz and re-meassure with the mains on and off.

I do have the correctiong file loaded for the older analog version. REW confirms this as I get a reminder that the correction file has been loaded each time I start the program.

Would the Behringer ECM8000 be a better choice for more accurate readings (with the appropiate correction file of course)?

[pclausen]

blaser wrote:

Can you talk about your subs, they are certaily DIY, can you give us details about enclosure fabrication, dimensions, woofer brands.... cost maybe...

Sure. I'm running 2 identical cabinets stacked on top of each other.

Each cabinet has an internal volume of 378 liters and is constructed of 1" MDF that is double lap jointed and screwed and glued. Internal bracing consists of 2 1" x 3" oak H-braces. Dual 6" ports, each 42" long providing for a 17Hz tune. The net volume is 336 liters. Drivers are TC Sounds PA-5000 with the following specs:

Size 18"
Vc: Underhung 4" wide, 4 ohm nom. dcr

Bl: 24 Tm
Vas 334L
Mms: 260
Fs: 22.8
Qts. 0.336
Spl: 93dB

These drivers are not official yet, so I belive mine are the first pair in actual use. I got a good deal on them, but they still set me back about $1000 each.

Here's a picture of one of the drivers:



And here's a shot of the lower enclosure prior to installing the driver showing how I had to use elbows to get my 42" port lenght:



Finally, here's how a single driver models when feed 1950W from a bridged Crown CE-2000. I'm within the excursion limit (about 75mm pp) down to the 17Hz tuning frequency. I plan to add a 36dB/Oct active HP filter to prevent damage to the drivers. This should also help with the huge room gain I have below 20Hz. Add 6dB for the 2nd sub for the potential to reach 126dB+ accoustical output from ~18Hz to ~72Hz

[pclausen]

brucek wrote:

The easiest method to get past that is to simply choose a program (1-10) that is already enabled for parametric mode (PA). Program 5 would be fine.

Otherwise, simply go through each filter and set its mode to off (OF) or parametric (PA). If you have a new 1124 you'll have to set the filters by hand as the midi has problems with REW.

I do have a new 1124 from PartsExpress (it has a 2002 built date). So you're saying the newer 1124's won't work with REW and I will always have to set the filters by hand and that midi doesn't work?!?!? If true, that really sucks as my whole reason for getting the 1124 was that it was supposed to work with REW.

[brucek]

If true, that really sucks as my whole reason for getting the 1124 was that it was supposed to work with REW.

It works fine with REW, except you must load the filters by hand. This is a quick menial task. I have had a BFD for many, many years and have never even bothered with loading by midi. I can load my filters by hand in seconds. It would take me longer to hook the **** cable up..

see this thread

brucek

[pclausen]

Ok, I guess its not that big a deal. It's just that I went to all the trouble (I guess it wasn't that much trouble really) of ordering a gameport to midi breakout cable and have a computer in my rack by the BFD and have the cable permanently connected. I control that computer (and hence REW) via a wireless airpanel and it would have been slick to have been able to in essence remote control the BFD this way. I guess it's not worth getting in a hissyfit over it. Once I get it dialed in, I'll likely just have a couple of different programs in there that will be easy enough to call up.

[pclausen]

I was able to remote desktop into my machine at home running REW and replot down to 10Hz (the initial un-corrected measurement):