[sfdoddsy]

I hjave the chance to nab a DEQX HDP-Express for a good price. I would be using it with my Linkwitz-inspired dipoles. They don't need as much EQ in the bass as regular Orions due to the use of AE IB12s.

Currently I'm using a Behringer DCX2496 and DEQ 2496 combo for crossover/EQ and Room EQ respectively. I also have an Anthem receiver with ARC for Room Correction.

Would I find the DEQX notably superior, and are there any pitfalls?

The plan would initially be to use the DEQX to do speaker and room correction, and then have it do the crossovers as well when I am comfortable with it.

Thanks

[JohnR]

Some friends of mine compared a DEQX using its FIR filters and its IIR filters, and reported the former to be noticeably better. However I wasn't there and don't know exactly what was compared, so this is just hearsay...

Tyson has experience with both, although I'm not sure that he has used the DEQX on OB.

Are you still in Sydney?

[sfdoddsy]

Yep, still in Sydney. DEQX (especially used) is one of the few things cheaper over here.

[Angaria]

along these lines - does the DEQX internal DACs fall far behind what you might get with an decent ($1K) external unit?

[JohnR]

Your reasoning behind the question being that if it didn't, then when you add the FIR crossover and EQ, you will come out ahead?

Steve - we should catch up sometime, been a while.

[versus rider]

I have the older PDC version and have used it with open baffles, these have now evolved into OB bass, 200Hz tractrix horns and Raal ribbons. I tried a cheap Behringer not the all singing all dancing version and it was rubbish, but I cannot make a comparison with the DCX. I can only say the DEQX is a brilliant piece of kit that doesn't add or take anything from the sound quality.

[Nyal Mellor]

It works great, as long as you do not need more than 10db or so dipole eq, there aren't any shelving filters so you have to have a design that works within the fir correction limits and the parametric eq you can apply

[Rudolf]

Can the DEQX cascade two low pass filters? At least for the two lower stages of a three-way OB I would prefer to  compensate the dipole roll-off with a 6 dB low pass instead of a shelving filter. With a DCX you can't follow that with another low pass which is needed for the crossover. Would be most elegant if the DEQX would have this feature.

Rudolf

[doug s.]

how does one measure a dipole speaker for processing, w/a single microphone?

thanks,

doug s.

[D OB G]

Hi sfdoddsy.

I’m running a DEQX.
The mid/tweeter FIR crossover needs to be done before the equalization, because the phase is linearized after the frequency response is corrected.
Nyal is right about the maximum boost.
If the dipole peak is high enough, the low end output can’t be brought up high enough if the bass has been calibrated (which uses up some digital headroom).
Either the bass has to have sufficient low output for a cut to also be done higher in its range, or a “saddle” shaped response can be equalized (I use two sealed subs below 40Hz).
You might be fine with your AE IB12s.
It’s also possible to cross from bass to mid without a digitally generated filter, e.g a LR, and the response then equalized with the IIR capability, giving greater headroom.
With either technique you wouldn’t need the Behringers, or the Anthem for room correction.
Whichever way, remember to use the appropriate delay to the bass to compensate for the time it takes to generate the FIR mid to tweeter filter.
Remember of course, FIR filters only work as well as the evenness of the polar response, and a somewhat symmetrical front to back impulse is only achieved with the acoustic centers physically aligned, and to the extent that the radiation is even from front to back.
 
Regards,
David

[kip_]

Rick Craig of Selah knows quite a bit about the DEQX. He designed a open baffle line array which measured flat from 30hz-20khz +- 1db. I don't known if he's designed a dipole with the DEQX but he's built several dipoles with passive crossovers

http://www.selahaudio.com/id195.html

It's triamped using room correction, driver correction, and higher order crossovers.

[sfdoddsy]

It works great, as long as you do not need more than 10db or so dipole eq, there aren't any shelving filters so you have to have a design that works within the fir correction limits and the parametric eq you can apply

Ah, there's the rub. I don't use as much dipole EQ as true Orions, but I still use a lot more than 10db.

I've attached pics of the DCX EQ screens showing just how much is needed in the bass, the mids and overall on the inputs.



That's around 30db on the bass.



That's 22db on the mids.



This is the response as measured by ARC at the listening position




I could reduce the bass EQ requirements by using a DSP based amp like a Crown CDi or Behringer iNuke to power the bass and add the shelving filters there, but that would add complications.

So if I understand correctly, then I could only really use the DEQX for overall speaker correction and Room EQ, not to replace my DCX?

[Gothover]

I also considered the DEQX, Currently using Behringer DCX. I assume the DEQX will be superior.

I also ordered the Mini DSP to see how it compares.

Dave

[Davey]

Steve,

Are you clipping any of the DCX outputs with that configuration?
What you might consider is to create a portion of the EQ using negative gain, high-shelving filters vice positive gain, low-shelving filters.  You have to recompute the 3db frequencies as well since the DCX doesn't use center frequencies in its setup.

Cheers,

Dave.

[sfdoddsy]

Those screen shots aren't quite what I use now as I reworked out everything when I started fiddling with the MiniDSP. I just had them on the computer I used to post the message. I'll post the real file when I can find it.

The actual ones are not that far off from those you sent me many years ago, with alterations for the different bass drivers.



There is no indication of clipping, but I have considered going negative just to be careful. I have the output gains lowered to reduce noise too, even though I know it is naughty.

What did you mean by 3dB frequencies?

[Davey]

Sorry, I meant the DCX2496 uses corner frequencies vice center frequencies for the shelving filters.

As an example, it looks you have two shelving filters cascaded in your first plot at 20Hz.  20Hz being the corner frequency of a single shelving filter and not the center frequency.  (The center frequency would be 66Hz.)

If you were to select a High Shelving filter with negative gain the corner frequency would be at the high end of the range (220Hz) vice the low.

Cheers,

Dave.