Equalizer for the ULF - Page 2 - AVS Forum | Home Theater Discussions And Reviews
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Old 12-02-2013, 01:11 AM - Thread Starter
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I asked miniDSP team about the precision issue with the 2x8 board and they answered that it is already fixed. Maybe someone can post measurements with a PEQ under 20 Hz?
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Old 12-02-2013, 01:55 AM
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Quote:
Originally Posted by FoLLgoTT View Post

I asked miniDSP team about the precision issue with the 2x8 board and they answered that it is already fixed. Maybe someone can post measurements with a PEQ under 20 Hz?

I'll measure mine when I redo my system, might be a few weeks though. Hopefully someone else can do it before then. I'm just not sure I have my current filters saved anywhere.

What they considered fixed, I still considered ****. Though I'll try the 48khz plugin instead of the 96 and see. Them even admitting there was an issue took lots of fighting.

If anyone has one, run it through a loopback with various filters around 10hz and see if they're still wacky.
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Old 12-05-2013, 11:18 AM - Thread Starter
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I'm a lucky bastard! I don't need any equalizing under 20 Hz! smile.gif

Today I did a test measurement with 6 drivers in 1/4 and 3/4 placement of wall width. There was no absorber on the back wall and the microphone was standing in the middle of the room (no first order length mode). The measurement was SPL calibrated and corecction files for sound card and microphone were applied.



I knew that my room gain is pretty high. All boundaries are very solid. Without equalizer I reach 3,4 Hz. Amplifier was a Sanway FP14000. My copy is flat to under 3 Hz.

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Old 12-06-2013, 12:59 PM
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Nice extension!!
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Old 01-21-2014, 03:38 PM
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Quote:
Originally Posted by FoLLgoTT View Post

My Behringer Ultracurve DEQ2496 looks pretty good at the low end. But the controls can only be set to 20 Hz. This is the lowest shelve I can configure.


Quote:
Originally Posted by bossobass View Post

Ah, I hadn't thought of the loss in precision with high sampling rates. It's true, to get full BW you have to have 40k sampling which, after spreading out across DC-20k Hz leaves very low precision in the SW BW. Add that to the obviously low cost ADC/DAC and the power supply solutions offered and it isn't a good prospect on paper.

Here's various analog and digital solutions I've measured after dialing in the proper curves for my current system and 10 dB boost:

c6af3c00e4e21ca23f1ffeb222f6213d.jpg

When you add the AVR and the amplifier roll off, this completely explains why most people do not have strong <10 Hz response.

Currently, I'm using the Oppo 105 as a pre/player. Its loopback is almost as flat as the SEQSS, so no loss there. The amplifier is -3dB @ 3 Hz and I don't use smoothing EQ, so therein lies the answer to my results vs most others.

I want to make sure I'm understanding this correctly. The reason for the different graphs is because one is smoothed and one is not?
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Old 01-21-2014, 03:41 PM
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I'm going to be testing a 2x8 minidsp shortly with the 8x8 firmware loaded into it (48khz instead of 96khz). Should have some interesting results I hope.
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Old 01-21-2014, 03:49 PM
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Nice to see you're back.... I thought they banned your ass
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Old 01-21-2014, 03:49 PM
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Quote:
Originally Posted by notnyt View Post

I'm going to be testing a 2x8 minidsp shortly with the 8x8 firmware loaded into it (48khz instead of 96khz). Should have some interesting results I hope.

Heh. Welcome back. smile.gif Look forward to what you find.
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Old 01-21-2014, 03:51 PM
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Heh. Welcome back. smile.gif Look forward to what you find.

Thanks. I already flashed the new firmware, I just need to find a few minutes to test. My subs are currently not EQ'd at all. Not going to bother until I finish the rest. The 96khz was pretty brutal screwing up the curves under 20hz. Lets hope this isn't as bad.
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Old 01-21-2014, 10:15 PM
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Quote:
Originally Posted by FoLLgoTT View Post

My subwoofer wall will be built next weekend and I'm still looking for a suitable equalizer for the < 20 Hz region. At the moment I'm aware of the following possibilities:

- Marchand WM8 -> rather expensive
- MiniDSP -> reported to not work well in the ULF and may have clipping problems
- self-made circuit board with Linkwitz transform -> only one fixed preset
- Bossobass' SEQSS -> availability?

Are there any other linkwitz transforming equalizers? Or any digital equalizers which can be configured for under 20 Hz?
The FBQ2496 has filters wide enough [5 octaves] to effect an LT type curve. It can be simulated to a degree in WinISD Pro. MiniDSP and Winisd Pro work pretty well together, at least for me. Boosting 20Hz at Q=.182 will lift from 3 - 113 Hz. Then a filter higher up at about 130Hz set for the same width will attenuate down to 23Hz. So as you can see, the cut-correction would not effect what you have boosted below 20Hz. Of course you can experiment with the top center and cut level, but a 8 - 10 dB boost @ 20Hz would be corrected with 8 - 10 dB of attenuation at the 130Hz center...or thereabouts, depending on FR sweeps.

I would not go through the trouble of building circuits. Not worth it really. The aforementioned technique has been used by me, and the difference between an actual Linkwitz solution with MiniDSP and the 1124DSP was not that different, just more extension on the bottom because the 1124 only has 2 octave filter widths, making the above strategy impossible. If you want razor thin accuracy then I suppose you could subject yourself to the potential rigours and consternation omnipresent when building a circuit board but I personally would not bother.

As for the ULF, the MiniDSP comes in two options: .9 and 2Vrms input. Maybe the clipping has to do with the wrong version being used?
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Old 01-21-2014, 11:10 PM
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Quote:
Originally Posted by kramskoi View Post



As for the ULF, the MiniDSP comes in two options: .9 and 2Vrms input. Maybe the clipping has to do with the wrong version being used?

The 2x8, 4x10, and 10x10 (maybe the open drc-an too) are all minimum 4 volt input, possibly 8 volt. I was talking with Andy about this, specifically the 2x8 board, and even with his knowledge he was unable to determine what it was - 4 or 8 volts.

In any event those three models at the least double the input voltage of the 2x4 boards.
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Old 01-22-2014, 01:25 AM - Thread Starter
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Quote:
Originally Posted by kramskoi View Post

The FBQ2496 has filters wide enough [5 octaves] to effect an LT type curve. It can be simulated to a degree in WinISD Pro. MiniDSP and Winisd Pro work pretty well together, at least for me. Boosting 20Hz at Q=.182 will lift from 3 - 113 Hz. Then a filter higher up at about 130Hz set for the same width will attenuate down to 23Hz. So as you can see, the cut-correction would not effect what you have boosted below 20Hz. Of course you can experiment with the top center and cut level, but a 8 - 10 dB boost @ 20Hz would be corrected with 8 - 10 dB of attenuation at the 130Hz center...or thereabouts, depending on FR sweeps.

I don't need any equalizing < 20 Hz. The gain in my room gives a nice low end. A shelving filter at 20 Hz with +2dB is enough to get a flat response down to 3 Hz. smile.gif
Quote:
Originally Posted by pdxrealtor View Post

I want to make sure I'm understanding this correctly. The reason for the different graphs is because one is smoothed and one is not?

Bossobass measured a DCX2496 and I measured a DEQ2496. These are different devices. The first one is a digital crossover and the second one a digital equalizer only.
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Old 01-22-2014, 04:21 AM
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Quote:
Originally Posted by kramskoi View Post

The FBQ2496 has filters wide enough [5 octaves] to effect an LT type curve. It can be simulated to a degree in WinISD Pro. MiniDSP and Winisd Pro work pretty well together, at least for me. Boosting 20Hz at Q=.182 will lift from 3 - 113 Hz. Then a filter higher up at about 130Hz set for the same width will attenuate down to 23Hz. So as you can see, the cut-correction would not effect what you have boosted below 20Hz. Of course you can experiment with the top center and cut level, but a 8 - 10 dB boost @ 20Hz would be corrected with 8 - 10 dB of attenuation at the 130Hz center...or thereabouts, depending on FR sweeps.

I would not go through the trouble of building circuits. Not worth it really. The aforementioned technique has been used by me, and the difference between an actual Linkwitz solution with MiniDSP and the 1124DSP was not that different, just more extension on the bottom because the 1124 only has 2 octave filter widths, making the above strategy impossible. If you want razor thin accuracy then I suppose you could subject yourself to the potential rigours and consternation omnipresent when building a circuit board but I personally would not bother.

As for the ULF, the MiniDSP comes in two options: .9 and 2Vrms input. Maybe the clipping has to do with the wrong version being used?

What is the "Q" that you posted about in boosting the 20hz signal? I don't understand what this "Q" means? Also, how do you know where to set the "Q"? I have a MiniDsp 2 by 4 balanced with the advanced plugin, but, have yet to hook it up as I am waiting on my sub build to finish. I have always wondered what this "Q" means and how should it be set?
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Old 01-22-2014, 07:35 AM
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What do people use for a HPF with the various Behringer units?

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Old 01-22-2014, 08:11 AM
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Quote:
Originally Posted by Martycool007 View Post

What is the "Q" that you posted about in boosting the 20hz signal? I don't understand what this "Q" means? Also, how do you know where to set the "Q"? I have a MiniDsp 2 by 4 balanced with the advanced plugin, but, have yet to hook it up as I am waiting on my sub build to finish. I have always wondered what this "Q" means and how should it be set?
Q is the width of the filter. It won't apply to the Linkwitz Transform in MiniDSP because the coefficients do all the work once you plug them in. Higher numbers denote a narrower filter...ie. 1.414 = 1 octave, lowers numbers are wider...i.e. .182 = 5 octaves. You would use narrower (number values above 1) filters for small adjustments over very short frequency ranges.

When using something like REW, the software itself allows you to simulate the result of setting wide or narrow for a dip or peak in the measured FR. It can be pretty accurate. The wider Q settings are really only used for shelving and "surrogate" Linkwitz Transform type simulations.

"Frequency response is NOT efficiency response."

 

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Old 01-22-2014, 08:32 AM
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Quote:
Originally Posted by FoLLgoTT View Post

Bossobass measured a DCX2496 and I measured a DEQ2496. These are different devices. The first one is a digital crossover and the second one a digital equalizer only.

Gotcha....thx!
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Old 01-22-2014, 08:38 AM
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Quote:
Originally Posted by FoLLgoTT View Post

I don't need any equalizing < 20 Hz. The gain in my room gives a nice low end. A shelving filter at 20 Hz with +2dB is enough to get a flat response down to 3 Hz. smile.gif
Bossobass measured a DCX2496 and I measured a DEQ2496. These are different devices. The first one is a digital crossover and the second one a digital equalizer only.
Mea Culpa my friend...I missed the "wall" in your post!wink.gif

"Frequency response is NOT efficiency response."

 

Klipsch RB-35's main

Klipsch RB-35's surround

Acoustech HT-65 center

Cerwin-Vega CV-2800

 

Subwoofer

B&C 21SW152-4  [21" critical-Q]

 

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Old 01-24-2014, 12:09 AM
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Well, tried loading the 8x8 firmware into the 2x8, but it seems they use a unified firmware now. No idea how to get this to run in 48khz mode as they suggested, if it's even possible. Sending them an email now. This thing is horrible under 25hz frown.gif
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Old 01-24-2014, 12:52 AM
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Well, tried loading the 8x8 firmware into the 2x8, but it seems they use a unified firmware now. No idea how to get this to run in 48khz mode as they suggested, if it's even possible. Sending them an email now. This thing is horrible under 25hz frown.gif

Disappointing. frown.gif
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