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View Full Version : DSP/room eq and 4430's



ricesinice
12-28-2007, 12:54 PM
I built a pair of 4430 clones a few years ago with the help of this forum, now I am hoping you all can help again with what seems should be a problem a lot of us think about.
I play most of my music through a CD player, or a laptop so, the source is digital ,then it gets converted to analog, goes into my driverack where the signal gets converted back to digital to get EQed to compensate for the room acoustics then back to analog to go to the preamp. It seems like there should be a fairly easy, and good audio quality way to not have to go through the extra conversion to get the room eq. Does someone know of a way to do this with an external sound card that would have digital inputs, and the ability for mic input to get the room acoustics, and save the profile to call up at a later date, or all the time, like the driverack....... and not cost too much?
Thanks,
Rob

readswift
12-28-2007, 03:34 PM
Driverack should have, and if it has no digital io thats real strange. Maybe it works on some obscure sampling rate then.
Either you think out-of-the box and spend huge pile of bucks on DEQX then go for the monoblocks ( still need preamps) way or...
basically you can do everything inside the PC , Vista comes with room correction built-in ;) and anyway, audio engine rewritten from scratch .

You can apply the frequency correction EQ inside PC, but Im not sure how much is it worth , the JBL's should be flat as they are (thats the point hahaha) . If you overcorrect some peaks, it is going to fold back off axis, leaving you a 10 cm sweet spot , then equal or worse outside. My intention doing digital stuff is to use digital crossover , every driver has its own DtoA converter. This is no simple stuff. Im goin to document everything but there are months ahead :)

boputnam
12-28-2007, 09:35 PM
I...It seems like there should be a fairly easy, and good audio quality way to not have to go through the extra conversion to get the room eq. Does someone know of a way to do this with an external sound card that would have digital inputs, and the ability for mic input to get the room acoustics, and save the profile to call up at a later date, or all the time, like the driverack....... and not cost too much?You lost me. You talk of using a mic input, which would be analogue.

What "extra" conversion? :help:

How do you presently measure the room response to set your "compensation EQ" in the DR?

Regardless of that confusion on my part, some use SmaartLIVE (http://www.eaw.com/products/software/index.html), which is analogue. Using a Fast Fourier Transform algorithm (FFT) it allows the comparing of two signals - a reference signal (time delayed) to an acoustic measurement signal. You then manually adjust the outboard EQ to suit. There are maybe 16 screenshots you can save. It is not inexpensive, and incredibly powerful.

readswift
12-29-2007, 01:31 PM
I think I get it what he means, he wants to be self contained without the physical help of others right ? :) Thats quite daunting task to begin with. I personally want to avoid restricting myself to DRC cause I dont trust it. It is only recently our inventory and computers became powerful enough to do it. Also, measuring the room is crucial. Thats why I think about hiring a professional , rather than buying the DEQX while its hot . Then the guy tells me what I can do with the room, maybe even complete redo from scratch ( soffit mounting, hell yeah !!) , hehe. If I'am done with that, then the need for room correction might be as useless , given the JBL's ability & attributes.

ricesinice
12-31-2007, 07:46 AM
No, my driverack does not have digital input (wish it did).
I want the mic input to eq the room with the pink noise like I do with the driverack which eq's the speakers for the response I select automagicly.
I just want to have the ability to eq rooms to get a decently flat response, and do it all before the music goes analog. There is software I just found and have not tried it yet called Room EQ Wizard that looks promising.
I did look at the Smartlive but, it is way above my budget.

boputnam
12-31-2007, 10:55 AM
I just want to ... do it all before the music goes analog.

:blink:

-----

I gotta add - I don't see what the difference is, doing it in the digital or analogue domain. You are making EQ corrections supported by the room response. Why and/or how would it be different?

toddalin
12-31-2007, 01:30 PM
:blink:

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I gotta add - I don't see what the difference is, doing it in the digital or analogue domain. You are making EQ corrections supported by the room response. Why and/or how would it be different?

Possible phase shift as well as the introduction of extraneous noise associated with the analog circuitry. :blink:

boputnam
12-31-2007, 02:11 PM
Well, perhaps, but if that is what it "sounds" like, I'd rather correct into that, then into something not final.

readswift
12-31-2007, 04:45 PM
someone wrote he was inbetween + - 1 dB in the upper octaves when he fitted a TAD2002 onto the 2344 horn. Also look at 2234 or 2235h measurements, they are essentially perfect !! When I saw the 2235h response curve in simulator, that moment marks my entry into the JBL world
:beamup:


I want to open a soffit mounting topic :applaud:

readswift
12-31-2007, 05:01 PM
you cannot correct the sub 100hz region by means of linear phase FIR filtering, its ridiculusly inefficient, nothinh would do it. That region must be taken care by IIR filters , these are close to their analog counterparts in phase shifting behavior ( ringing after transients), analog might do even better here . I myself dont want *any* type of filtering to take place there. All I want is phase optimised crossovers az 1khz (again , no linear phase either ) .

boputnam
12-31-2007, 05:18 PM
...All I want is phase optimised crossovers ...AI would add is "coherant phase", too. :)

readswift
12-31-2007, 05:40 PM
best summation ever can be read here: http://hypex.nl/docs/Bruno%20Masterclass/slides.htm

have to scroll quite a lot

ricesinice
01-02-2008, 06:32 AM
The thing is, I am doing 2 Digital to Analog conversions to go through the Driverack,(I assume the driverack does the auto EQ wizard in the digital domain) when I use a digital source. I would like to have only one D to A conversion and hopefully do the room corrections before it goes analog.

readswift
01-02-2008, 06:44 AM
if my suggestion is right, and the driverack has obscure sampling rate ( please link online manual or copy the text here) it would need hardware hackery, doable, but if it worths, that depends solely on the quality of components inside the driverack. So you may want to open it and post pictures ;)

UreiCollector
01-03-2008, 06:47 PM
...the source is digital ,then it gets converted to analog, goes into my driverack where the signal gets converted back to digital to get EQed to compensate for the room acoustics then back to analog to go to the preamp.

I think I know what Rob is getting at. He wants to avoid the D to A to D to A, and go D, D, A. without the additional A to D and D to A steps in the middle......yada yada yada....he wants to stay digital, do all his processing, and then go analog once all else is finished......

The 'holy grail' in digital audio is to stay in the digital domain as long as possible, without conversion to analog, and subsequent re-sampling back to the digital domain (sometimes at inferior sample rates, especially if your a super-audio fan).

Unfortuantely from what Rob is saying, his driverack does not have digital inputs, so running his computer/cd straight to that box in the digital domain for EQ'ing is out of the question.

For most of us $ is a limiting factor, and we must make compromises. I personally chose to only use my digital crossover on the subwoofers (JBL 2242H's), where the possible negative effects are hopefully not audiable (thus avoiding an A to D, and D to A process on my "mains"). I'm high-passing my mains, and low-passing my subs in the analog domain ahead of my digital crossover/eq.....thus EQ is only applied to my subs (and some high pass at 20hz, but that's another story).

I really think your biggest benefit of EQ will be had below 150hz (ie, use your driverack on the subwoofers only). For any issues above that, I would look into room treatment to correct.

This way, no new equip to buy....and you'll probably end up with a better sounding system.

Best luck, and happy listening!

UreiCollector
01-03-2008, 06:50 PM
Another quick point. My understanding is that Auto-Eq really isn't worth much above 150hz anyways, it will most likely cause more issues than it fixes due to reflections/mic placement/etc. You will probalby just want to leave flat above this point and EQ manually if at all.

:)

readswift
01-03-2008, 08:35 PM
he can have his digital input implemented into the driverack if we bypass the ADC with a digital receiver. If the sampling rate is non uniform eg 50khz instead of 48 , then it needs an async sample rate converter too . IF the component quality is good inside the driverack it worths the effort as well . It's a job for a tech because of small footprint IC's. I woudl be interested about the DAC ic-sat the outputs, rest can be upgraded easily.
Btw you can upgrade most CDP-s this way too to acept spdif or AES ebu.

ricesinice
01-04-2008, 06:44 AM
Fredric has what I want to do correct. I have a hard time explaining what I want to do, just ask my wife!
Maybe that is what I should do, just apply EQ for the low frequencies. I was just hoping that there would be an all in one solution without the extra bi-amping, and D to A conversion.
I will continue to look at the program Room EQ Wizard....looks kind of promising.
Thanks,
Rob

readswift
01-07-2008, 08:26 PM
how old is the driverack? If you have multibit DAC inside instead of the 90's delta sigma it might worth the effort. Please post picture of the output region.

boputnam
01-08-2008, 05:49 PM
I really think your biggest benefit of EQ will be had below 150hz (ie, use your driverack on the subwoofers only). For any issues above that, I would look into room treatment to correct. This is not consistent with my experience. Apply EQ where needed, when needed.

Room anomalies can occur anywhere in the spectrum. These can be mitigated by notching the resonance, thereby lessening the excitation. Room treatments are good, but most often impractical (always impractical in SR...) and not of the desired decor (therefore, impractical - oh, I already said that... :p ).

I personally don't appreciate the results of autoEQ, nor understand why one would even desire this. Apply modest, careful EQ - learn what is happening and what your filtering does. Listen, and listen again. That is far more valuable.

As example, last weekend, in a crummy club in a far away land, I was introduced to the SR "Systeme a la Crap". I won't bother naming the ingredients, but they are far below most anything anyone here would consider. But, there it was, the house system, no possibility of using my board or racks or carefully tuned cabinets, and I was charged with the challenge of throwing out a good show for the band and fans. The GEQ's were ineffective and spent, the mains impossibly harsh and honky, so I spent all night long on the individual input strip EQ's, trialing various notching of room resonances, and then alternatively boosting of the peak area of the A-weighted SPL curve to improve intelligibility and clarity, and then cutting it back to reduce the bite. These results were transitory, impacted by the waxing and waning of the crowd. Your results will be far more static, unless you move the deck chairs.

But you'll understand what is happening... ;)

readswift
01-08-2008, 07:28 PM
yip i would say use it for crossover only, & maybe slight eq , after you r finished with room treatment .

JBL 4645
01-22-2008, 08:38 AM
Another quick point. My understanding is that Auto-Eq really isn't worth much above 150hz anyways, it will most likely cause more issues than it fixes due to reflections/mic placement/etc. You will probalby just want to leave flat above this point and EQ manually if at all.

:)


What of this Audyssey EQ device I think Tom Holman is behind this, but itís a costly EQ unless you win a modest lottery win? :D

http://www.audyssey.com/ (http://www.audyssey.com/)

Skywave-Rider
01-24-2008, 10:18 AM
I found this to be helpful , though it can be depressing to see just how many issues your particular room may have. If you haven't seen it:
http://www.harman.com/xls/Room%20Mode%20Calculator.xls
You use it to find not only the best listening position(s), but speaker location(s).

Rudy Kleimann
08-05-2008, 02:09 PM
I think he wants to take digital data straight out of the laptop (or whatever) and run straight into the Driverack without making it analog in between. Laptop sound cards aren't worth a flip anyway, unless you buy a high-quality outbard model.
but the problem is (as I read it) the Driverack he has won't accept a digital input, even if he can get the digital datastream out of the Laptop or whatever.