DCX2496 EQ Tips... Does anyone had success with Equalization of bass is Small Rooms?

Hello!

I recently went for the Mr. Earl Geddes approach of applying 3 subs to stereo sound reproduction to have the best possible bass.
Initially, I was planning to buy Mr. Geddes subs, but the freight charge to Brasil is really expensive so I decided to go for DIY with a pair of Dayton 10 inch and a commercial SVS 12inch sub.
The final result is far away from the bass dream I'm searching for, but this is exclusively because of the lack of acoustic treatment that it's fundamental for this kind of system.
I'm using a behringer DCX2496 cross for the 3 subs, adjusting the phase, level and crossover for each one individually.
The problem is that I'm not getting good results with the EQ of the DCX... I'm using REW software and the EQ suggested for the software changes almost nothing in the curve measured before and after. What should I look for? Is there any tip for using the EQ? Is it best done by ear?

Murillo
 
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The problem is that I'm not getting good results with the EQ of the DCX... I'm using REW software and the EQ suggested for the software changes almost nothing in the curve measured before and after. What should I look for? Is there any tip for using the EQ? Is it best done by ear?

You have to do measurements. Lots of them.

Your goal should be to find a configuration that creates the lowst point-to-point differences within the listening area. The result doesn't need to be flat, just look for low spatial variance. Vary the subs' locations and level to get there.

The next step is to equalize the response for flatness. Treat the subs as one and run REW's Auto-EQ functionality.
 
Doing bass EQ can be very difficult. Have you been using the Auto-EQ function of the DCX?

I've helped a few people with the Geddes mutli-sub and DCX. Perhaps I can help you, a little.
THX Pano, how can I use DCX autoEq??? I thought tha autoEQ only exist on DEQ2496... Yes, would be great to have your help.

Markus, I will plot here my measurements for you see, please advise me for the best position, at least, the initial setup, as I noticed the approach is:
1st sub at the corner behind the mains, back wall.
2nd sub at the middle of the side wall, not in the corner
3rd sub at other position distant from the others but not at the corner
As for the measurements, I have to do a lot to find the best position or to do the EQ? how many measurements should I take?
thx again
 
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To answer your question - yes, I always have success, but there is always a little more to these things than meets the eye. You can see the results that I achieve in the talks on my website Geddes on Audio . But those took a lot of work and proprietary software. If you look carefully you can also see how complex the transfer functions have to be to get this kind of result. You are not going to get there with trial and error.
 
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Markus, I will plot here my measurements for you see, please advise me for the best position, at least, the initial setup, as I noticed the approach is:
1st sub at the corner behind the mains, back wall.
2nd sub at the middle of the side wall, not in the corner
3rd sub at other position distant from the others but not at the corner
As for the measurements, I have to do a lot to find the best position or to do the EQ? how many measurements should I take?
thx again

The only easy solution I know is to use a sub in the near field (closer than 2ft).

All other solutions are very complex. Ideally you would measure the transfer function of every possible subwoofer location to multiple locations within the listening area. Then a software would pick the best locations and settings (level, delay, EQ).

Other than that follow the approach I've outlined in my last post.
 
To answer your question - yes, I always have success, but there is always a little more to these things than meets the eye. You can see the results that I achieve in the talks on my website Geddes on Audio . But those took a lot of work and proprietary software. If you look carefully you can also see how complex the transfer functions have to be to get this kind of result. You are not going to get there with trial and error.

What does your software try to optimize? Lowest seat-to-seat differences, flattest frequency response, lowest modal decay, something else?
 
Subs have been my specialty for two decades. So I'll ask a couple of questions to see if I can help. How did you calculate the enclosure volumes and or tuning frequencies? Are they sealed, vented or bandpass? what are your room dimensions? Putting a subwoofer in the corner is going to cause gain by loading the walls on either side of the sub and the floor. try pulling it out from the corner and down one of the walls by about a foot. Having your sub in the center of a wall will certainly cause you to have cancellation problems, try shifting it one way or the other off center. Without knowing your enclosure information this is as much help as I can give. If you need help with and enclosure design I'll be happy to help you tune them better if you want the help.
 
You can look at both spatial and spectral data so you can optimize either or both as you see fit. It's not automated, but it is setup in such a way that you get real time feedback so convergence is pretty fast. No guarantee of "optimum", of course, but my clients and I are always happy with the results.

Since its not "perfect", you wouldn't like it, but since it "gets the job done" I am very pleased.;)
 
Subs have been my specialty for two decades. So I'll ask a couple of questions to see if I can help. How did you calculate the enclosure volumes and or tuning frequencies? Are they sealed, vented or bandpass? what are your room dimensions? Putting a subwoofer in the corner is going to cause gain by loading the walls on either side of the sub and the floor. try pulling it out from the corner and down one of the walls by about a foot. Having your sub in the center of a wall will certainly cause you to have cancellation problems, try shifting it one way or the other off center. Without knowing your enclosure information this is as much help as I can give. If you need help with and enclosure design I'll be happy to help you tune them better if you want the help.
Hi, the enclosure volumes were calculated using WinISD, ~ 28,5liters, 1 cubic feet. Both are sealed, my room dimensions are: 4,00M x 3,40M x 2,80M.
Tomorrow I will make precise measurements with REW and will post the graphics here to make it "study case". Hope to hear your suggestions as also Mr. Geddes, Markus and the other GURUS.
 
Hi,Dayton Audio RSS265HF-4 10" Reference Subwoofer.

specifications: • Power handling: 350 watts RMS/600 watts max • VCdia: 2-1/2" • Le: 1.05 mH • Impedance: 4 ohms • Re: 3.3 ohms • Frequency range: 22 - 1,000 Hz • Fs: 26 Hz • Magnet weight: 100 oz. • SPL: 87 dB 2.83 V/1m, 84 dB 1W/1m • Vas: 1.59 cu. ft. • Qms: 3.26 • Qes: 0.51 • Qts: 0.44 • Xmax: 12.3 mm • \

thx
 
If you are willing to vent your enclosures, tuning them to 35 Hz in that volume with a bit of damping material (I use dacron, the stuff pillows are usually stuffed with), then you will gain 6 dB from 50 Hz down to 20 Hz. The vent will need to be 3 inches in diameter and 11.02 inches long for that box volume. That new tuning frequency should give more bottom end thump and still be nice and smooth. This should also sustain power handling beyond 400 Watts.
 

StigErik

Member
2008-02-21 12:30 pm
I've done the Geddes approach with eight small 10" subs in a very small room. It helps somewhat between 100 and 200 Hz. Below 100 Hz, the results was equally awful no matter the number of subs. The solution to this is EQ. I found it quite easy to apply EQ, but it requires a measurement system with adequate resolution a low frequencies.