New DEQX HDP-3 Express

Nyal Mellor

Industry Expert
Jul 14, 2010
590
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DEQX have release a slimmed down version of their HDP-3. It is selling for just under $2k USD. I have written about it in my blog and also got the 'skinny' from Alan Langford at DEQX on the differences between it and the HDP-3.

Looks like an interesting unit and the new, lower price point is appealing. Note that the digital room correction in the DEQX units only operates below a user defined frequency (a very good thing, personally I don't want no 'blind' algorithm messing with my mid and high frequency speaker voicing that the designer spent painstaking hours getting right) and is based on digital parametric EQs. The end user is able to manually adjust and set the EQs or there is auto EQ functionality.

What is the general interest in DEQX amongst the community?
 

RUR

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Apr 20, 2010
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Nyal, will it only operate below (nominal) Schroeder or can the user choose any cutoff including full range (a la TacT)? No 24/192 input, but what is max res input?
 

Nyal Mellor

Industry Expert
Jul 14, 2010
590
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330
SF Bay Area, CA, USA
User can specify what frequency they want it to work below when the auto equalize room correction feature works. This could then be set by the user to a nominal schroeder frequency such as 250Hz. The general philosophy of the DEQX is to apply parametric EQ to correct room related issues below the schroeder frequency and FIR based filters to correct on axis drive unit frequency response above this.

Maximum resolution is 24/96. My understanding from talking to the DEQX guys is that no sample rate conversion occurs inside the box, which is different to TACT which AFAIK asynchronously resamples everything to 100k or something.
 

RUR

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Apr 20, 2010
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User can specify what frequency they want it to work below when the auto equalize room correction feature works. This could then be set by the user to a nominal schroeder frequency such as 250Hz. The general philosophy of the DEQX is to apply parametric EQ to correct room related issues below the schroeder frequency and FIR based filters to correct on axis drive unit frequency response above this.
So, the unit will apply FIR filters above Schroeder or does DEQX expect the user to use another solution for this?

Maximum resolution is 24/96. My understanding from talking to the DEQX guys is that no sample rate conversion occurs inside the box, which is different to TACT which AFAIK asynchronously resamples everything to 100k or something.
24/96 max is a problem if the unit won't resample a higher-res input e.g. 24/192. The DSP will process at multiple resolutions (44.1, 48, 88.2, 96)? That would be unusual. Most, like TacT, process at 24/96 IIRC - for now.

FYI, Amir is working on a review of the HDP-3 non-express.
 

Nyal Mellor

Industry Expert
Jul 14, 2010
590
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330
SF Bay Area, CA, USA
Yes the unit applies FIR filters above schroeder. The way it is designed is that the DEQX measures each drive unit individually and then calculates a FIR based correction filter for each one. Hence it is not really room correction so much as speaker correction. IMO above the schroeder frequency the use of 'room correction' is the wrong anyway - the issues created by the room are either that reflections from boundaries are too strong relative to the direct sound or that the time it takes for sound to decay is too long. Neither of which can be fixed through DSP room correction or parametric EQ. DEQX have it right in that above the schroeder frequency what you are fixing electrically is the speaker and its deficiencies.

I don't believe either unit has a digital input that does 24/196. And my understanding from talking to DEQX is that the unit operates at the native input sample rate. I agree this is odd in a hardware unit, but this is typical in software.
 

RUR

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Apr 20, 2010
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Still confused, Nyal...

The way it is designed is that the DEQX measures each drive unit individually and then calculates a FIR based correction filter for each one.
I'm curious as to how this is done. Most DRC places a mic at the listening position (and some at multiple positions surrounding) to measure the entire speakers FR - either using tone sweeps or, with TacT, an impulse. How does DEQX measure each driver individually?

Hence it is not really room correction so much as speaker correction.
But isn't this simply semantics? All DSP is causing the speaker to produce a "corrected" FR, no? What is DEQX doing that TacT or Audyssey or Trinnov etc. doesn't do?

IMO above the schroeder frequency the use of 'room correction' is the wrong anyway - the issues created by the room are either that reflections from boundaries are too strong relative to the direct sound or that the time it takes for sound to decay is too long. Neither of which can be fixed through DSP room correction or parametric EQ. DEQX have it right in that above the schroeder frequency what you are fixing electrically is the speaker and its deficiencies.
Fully understand the compromise inherent in DSP correction as regards direct vs. reflected sound, but in the absence of micing anechoically, what choice do we have? Having said this, whatever it's doing and however it's doing it, the result, both subjectively and by measurement, is pretty spectacular. Next time you're in LA, you'll have to come by. It's trivial to do an instantaneous A/B comparison, including correction only below Schroeder.
 

Nyal Mellor

Industry Expert
Jul 14, 2010
590
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330
SF Bay Area, CA, USA
DEQX is a complex unit, but at its fullest you can use it to digitally correct all of the individual drivers within your system (up to a 3 way), perform a digital crossover between each driver AND perform room correction.

For driver correction you put the mic close to each drive unit and measure it, DEQX then calculates a FIR correction filter for that driver. Keep on doing this until all drivers have been measured.

DEQX is closer to the loudspeaker management systems used in professional audio than a TacT, Audyssey or Trinnov.

I prefer the term speaker correction since the deficiencies the DSP is correcting are related to the speaker. If you design the speaker and it measures flat in an anechoic chamber it is going to measure basically the same in your room above schroeder. Not so in terms of below schroeder, where the measured response will be strongly influenced by the room it is placed in. Although as you say the end result - "corrected FR" at the listening position is the same.
 

amirm

Banned
Apr 2, 2010
15,813
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Seattle, WA
I'm curious as to how this is done. Most DRC places a mic at the listening position (and some at multiple positions surrounding) to measure the entire speakers FR - either using tone sweeps or, with TacT, an impulse. How does DEQX measure each driver individually?
As their description mentions, you need to be able to drive each driver separately for this to work. This is possible with some speakers (e.g. Wisdom) but obviously not many others.

But isn't this simply semantics? All DSP is causing the speaker to produce a "corrected" FR, no? What is DEQX doing that TacT or Audyssey or Trinnov etc. doesn't do?
They do two things that TacT doesn't do:

1. Driver correction per above.

2. Providing active cross over for each element in the speaker. I suppose this could be simulated with TacT but I am not 100% sure.
 

RUR

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Apr 20, 2010
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Thanks Nyal and Amir, now I understand the differences. It's possible this could be approximated with the Tact, but only by using multiple S2150XDM amps - one for each driver set/frequency band. Individual drivers can be measured near-field and the files concatenated. Crossover provided by each amplifier. An absurdly expensive solution when compared to the DEQX.

I'm quite interested in the full-featured version, and look forward to Amir's review.
 

Nyal Mellor

Industry Expert
Jul 14, 2010
590
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330
SF Bay Area, CA, USA
Hey Ron

There are a couple of reasonably full featured reviews on for example - 6 moons. I have a good understanding of the units functionality as well if you want to speak about it over the phone. Have you chosen a nice fabric for the ceiling yet?

Nyal
 

terryj

New Member
Jul 4, 2010
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bathurst NSW
it's good to start to get to the 'bottom' of the differences between the deqx and tact, I too am sorta as confused as RUR but from the other direction!

Deqx is mainly a speaker correction device, rather than a room correction device like audessy...not that I have any experience with that either! About the only time they seem to cross paths in their use (and maybe is something that contributes to confusion) is the 'final stage' with deqx, when you measure from the LP to do bass room correction with parametrics. I am assuming most of these other products do measure from the LP????

With deqx, that is only done after the speaker has been made fully deqx active, ie as mentioned each individual driver within the array has been measured and corrected, and crossovers used.

Dunno if you are aware of this amir?..you can try it both ways and compare I guess....there is a neat trick when calibrating the bass driver (if going fully active)..the mid an tweeter (due to the frequencies covered) are best measured and corrected anechoically (I'm too bloody lazy to take em outside and do this so I do them in room..lazy bugger that I am) or if in room, with as long a window as possible before first reflections, BUT with the bass you can (and I definitely do) measure and correct the woofer from the LP. Most definitely I do that with subs too.

The difference/improvement can be startling, because within the correction filter for the woofer is all the phase stuff done by the room. (most people look simplistically at the correction filters as correcting amplitude, but the real magic is that they correct phase and group delay as well). As most woofers operate below the critical frequency you can do it from the LP, and to get the phase fixed to boot can be amazing.

[of course, you then have to ensure that all the drivers are time aligned, so it quickly becomes more complex and the learning curve is not quick nor easy. Hence, probably, the attraction of these 'one button let the device do all the work' solutions]

I run two deqx units as a four way plus subs.

EDIT just saw nyals comment about 'over the phone'..a really useful thing is over the phone via/plus skype. skype can allow the other person to look at the computer screen of the other computer on their own computer, and SEE what is being done in the software as if they were there.

alan has helped with that trick, and it works a treat!
 

amirm

Banned
Apr 2, 2010
15,813
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0
Seattle, WA
Ditto. Amir, gazing into your crystal ball, when can we expect you to go to print?
Unfortunately not very soon :(. After a warm welcome, we could not get our phone calls returned from them. I have asked my guys to try again, including the offer to buy HD-express sight unseen. Let's see if they are interested in sales or just science projects :).
 

RUR

WBF Founding Member
Apr 20, 2010
647
3
0
SoCal
Have you chosen a nice fabric for the ceiling yet?

Nyal
Fabric? Ceiling? Nyal, I did verify that the TacT accepts 176.4 input.

Unfortunately not very soon :(. After a warm welcome, we could not get our phone calls returned from them. I have asked my guys to try again, including the offer to buy HD-express sight unseen. Let's see if they are interested in sales or just science projects :).
Ah, so your intent is to compare TacT to the "express" version vs. the full-featured? I had thought it was the latter.
 

terryj

New Member
Jul 4, 2010
512
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bathurst NSW
Unfortunately not very soon . After a warm welcome, we could not get our phone calls returned from them.


Amir, who did you speak to there?
 

amirm

Banned
Apr 2, 2010
15,813
37
0
Seattle, WA
I am not talking to them but rather, someone in my company has spoken to them. So don't know who it was.
 

alanl

New Member
Sep 3, 2010
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I am not talking to them but rather, someone in my company has spoken to them. So don't know who it was.

Dear Amir,

My name is Alan Langford from DEQX and have been direct to your forum by one of our users. I'm very concerned that you have been unable to contact us at DEQX by phone or have left messages that have not been passed on. Please accept our apologizes if you have left messages as we try to reply to all emails within 24 hours (weekends excepted) and phone calls as soon as someone is available.

if you could email either our general email address "sales(at)deqx.com" or my direct email "alangford(at)deqx.com" we would be more than happy to answer any questions you have.

Best regards,

Alan
 

jphaggar

New Member
Nov 27, 2010
2
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0
Amir
I'm a new commer to this forum , I have been searching around for a full review in the DEQX Express but in vain . From what I guess is that the DEQX Express is here to replace the older 2.6 unit that was their flagship unit befor the HDP 3 appears , presumably the Express will sound as good or better than the 2.6 , or else I dont understand why the Express ? can anyone comment ?
When it comes to line array speakers , where exactly should the mic be placed for the measurements ? I actually use the Behringer DCX 2494 and I presume using The DEQX Express should be a real upgrade ?
I am planing to purchase the DEQX Express soon but only when I'll be reading a full test . Is there any test on the web ?
Thanks for your help
JP
 

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