Is DEQX a game changer?

Yes Al, you can be confident that your Ulysses will sound so much better with the HDP-4. Unmodified Shahinian Obelisks were my first foray with DEQX and I was amazed at the improvement in clarity and realism it brought to them

Bi & tri-amping is the ultimate but nevertheless this manages to transform literally every type of speaker & room I have tried

You have an enjoyable time ahead - just be prepare to lose the rest of your life to the music :)

Timlub, whilst you are correct and I have used DEQX in all the configurations you mention, even on a speaker containing a passive crossover, the sense of reality and coherence is very impressive. However Bi-amped with Subs or Tri-amped is at a whole new level and I will never go back

As a DEQX happy owner, I've been following this this discussion with great interest.

I have been in DIY speaker building for more than 40 years (not getting any younger...). I experimented many things over the years, and yes, I can strongly affirm that DEQX is a game changer for me.

Achieving the "perfect" passive crossover is a mission impossible, at least for DIYers, which are not necessarily equipped to conduct all the required tests and moreover, because of the numerous technical limitations (especially phasing) that good old capacitors and inductors introduces by their electrical nature.

I moved to analog active crossovers and tri-amping 15 years ago and at that time, it was clear I would never go back to passive crossovers and single amp. I moved to the 3rd generation of audio filtering: digital. I bought the DEQX ExpressII and more than one year later, I can say it's the greatest toy I ever bought to myself! I would have never thought that the improvement would reach that level. It is a great pleasure to listen to commercial speakers that sells more than 10 times the price I paid for my drivers and doesn't "beat" my homemade speakers (hum...I may not be fully objective...) Therefore, I can now say that I would never go back to analog active filtering (2nd generation)... Imagine how far I am from the first generation of filtering...

I see no merit in commenting my own experience with my DEQX since it would be a copy of the excellent description Drewan77 made and as you can see, I fully share his enthusiam.

As a speaker builder, I'm having so much fun calibrating the speakers using a mouse and a keybord ! You punch in the parameters, save it to the DEQX and there you go, you can immediately listen to your design! And you can do silly things such as 96db/octave filters that you can't even think of in the analog world; no more physical limitations, just numbers crunching !

One element I can add to this thread is how surprised I was to observe how crucial is the crossover frequencies selection and how it can change the voicing of the system. While the frequency measurement of two drivers may show that they can easily handle a given frequency range, the resulting "voice" may be quite different. So I played a lot with the P1-4 buttons (Drewan77 explained) to find out the best calibration so my ScanSpeak Revelator performs at their best. By the way, Drewan77, I got the same result: 100 Hz is my best option to integrate smoothly my big guys (15" subwoofers).

In closing, from a DIY speaker builder point of view, I'm a little sad because my speakers are now performing so well, I can't imagine what I could do to improve them, which means I have to retire from this hobby..!! Fortunately, I'm also a passionate music lover and I now have a full discography to re-discover !

Regards,
Denis

Good to read your comments Denis and you have reminded me of an important aspect that Almarg may want to consider

A full range speaker such as the Ulysses that he describes will benefit from DEQX (automated) phase and time alignment, however the larger drivers will still need to handle all lower frequencies up to the passive crossover point

If you can reduce the number of frequencies a driver has to cope with and use a steep crossover, each cone has less work to do to reproduce the remaining range cleanly

Adding a sub to such a speaker gives the facility to remove deep bass frequencies via DEQX (in 'our' case below 100hz) which means the larger drivers will only concentrate on mid-bass upwards and this makes a significant difference to transient attack and overall cleanness of the sound. It is exactly what I originally did with my old Obelisks ad still do with the OBs

Your points about voicing are very valid and yes crossover frequencies and slopes can be tested via the presets as part of the configuration process until you arrive at your optimal voicing. For all the uninitated reading this - it means your system can sound exactly how you want it, in my case clean fast, dynamic & punchy right down to a measured -2dB at 16hz

Tim, Andrew, Denis, thanks for the excellent inputs. Points taken.

11-19-14: Timlub
When building speakers, we time drivers [that] are not time aligned on the frontal plane by adding padding/baffle step compensation to change the delivery of the tweeter and mid hitting your ear at the same time. This is built into the crossover. An External device cannot change that as far as true timing speed is concerned.

Hi Tim,

You may already be aware of this, but just to be sure the DEQX processing divides the spectrum into thousands of segments, adjusting the delays of each of them such that time coherence is attained even in the presence of a passive crossover within the speaker that is higher than first order, which would normally make time coherence impossible. See the graph and the references in the text to group delay in this writeup at the DEQX site, as well as the HDP-4 brochure and their FAQ writeups.

Best regards,
-- Al