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[DSP loudspeaker crossovers done right]

Don't be fooled by the blurb on the DEQX website regarding group-delay correction or compensation of loudspeakers. It's a way oversimplification of reality and they have been pushing the same barrow for decades which is probably why they have never commercialized their own speaker systems using it, instead pushing the gimmicks onto other naive loudspeaker designers. Trying to fix up a loudspeaker on a single axis was never going to work. Loudspeakers are far more complex than this and radiate into free space in all directions and not just on one axis alone ! What would fix up a signal chain on an electrical connection simply won't work with a distributed device such as a loudspeaker. This is why no serious hi-end audio manufacturer would ever use a DEQX as well ! Yes, sure our own  UPP can do long-length high sample rate, ultra deep convolution and FIR filtering and do a much higher resolution correction than a DEQX could ever do but do you really want to go down this path ?  When it comes to loudspeakers there simply is no free lunch here and no easy fix and throwing lots of DSP at the problem can often make the problems a lot worse. It certainly is not a panacea for a bad speaker design to begin with !

Anyway don't take our word for it but we suggest you read these three important documents before outlaying your hard earned money on such a device or anything that is just a fancy inverse convolution filter ! These are documents written by other well established audio engineers and echo the same sentiment as us. This is what DEQX will never tell you and why they never sell loudspeaker systems themselves using their own DSP hardware and even if they did it was always going to be a band-aid solution to a complex problem !

https://www.grimmaudio.com/wordpress/wp-content/uploads/speakers.pdf

And the take-home message from this document is:-

DSP loudspeaker crossovers done right

From the above we've learned that:-

• Heavy-handed correction exacerbates acoustical problems
• Sharp, linear-phase filters cause pre-ringing
• Targeting an exact linear-phase sum can cause pre-echos.

In short, brute-force correction sounds grainy and smudgy. When you hear cymbals go "splash" instead of
"crash", it's naive DSP at work. So:-

• Do not shave off the hair, a nasty stubble will grow back.
• Do not correct beyond the very beginning of the impulse response.
• The gentler you correct, the wider the angle over which the correction still improves things.
• Target a minimum phase sum.

For the time being I would strongly recommend designing the correction manually. This rules out FIR as the
main workhorse. For each bump or dip one corrects, one should know exactly where it comes from, and make
sure that it isn't better corrected for acoustically. Unfortunately, designing DSP filters does not relieve one from having to know one's acoustics.

Also:-

https://linea-research.co.uk/wp-content/uploads/LR%20Download%20Assets/Tech%20Docs/CrossoverFilters%20White%20Paper%20-C.pdf

Also shown in Figure 8 is the impulse responses for a complementary high-pass brick-wall FIR. If we construct a crossover filter bank with such a complementary pair of filters, the Gibbs ripples are also complementary (since we will expect the filters to sum to a flat response with linear phase, producing a perfect impulse). The summed result will thus be free of any Gibbs ripple, so what's the problem? The problem is off-axis. The complementary ripples will only cancel if the delay suffered by the signal from each driver is identical. Off-axis, where the path lengths differ, the ripples will not cancel, leading to the possibility that Gibbs ripple might become audible (just like a high-Q ringing filter).

Such summing errors will be more pronounced at higher crossover frequencies because the ripples are more closely spaced. Lower frequency
crossovers will have wider ripples which will more easily cancel in the presence of off-axis induced delays.

It is evident that steeper cut-off slopes give rise to Gibbs ripples of greater duration. It makes sense therefore to restrict the cut-off slope to be no more than is necessary for the application.

And from the Linkwitz Lab website pretty much the same cautionary tale

https://www.linkwitzlab.com/frontiers.htm

I - Digital crossovers

Some people think that digital crossovers will replace analog ones, because digital filters can be designed with desirable characteristics that are impossible to realize with analog circuitry. In particular, lowpass and highpass filters with extremely steep slopes and linear phase shift are possible. Steep slopes reduce the overlap region between drivers. Linear phase shift eliminates waveform distortion and merely causes a delay of the signal.  Such characteristics can be obtained from the digital equivalent of tapped delay line filters, which have a finite impulse response (FIR) duration that depends upon the number of taps used. Digital FIR filters can have almost any desired frequency response, if the number of weighted taps is made sufficiently high. [1]

The linear phase shift comes at a price. The impulse response rings. The more so, the steeper the filter slopes. Both lowpass and highpass sections of the crossover ring, but when the outputs are combined, as for a crossover, then the two impulse responses add to a non-ringing, delayed pulse.

All would be fine, if we listened only in anechoic spaces or to speakers with coincident drivers. In reality we use speakers in rooms with reflections and reverberation and the the drivers are separated from each other due to their sizes. As a consequence the off-axis response of the speaker matters and contributes to what we hear. With the drivers non-coincident, the lowpass and highpass outputs are delayed different amounts at points off-axis, and the ringing is no longer canceled in the addition. In the best case the drivers might be coaxial, but this has another set of problems. Very steep crossovers can also cause a very abrupt change in the polar pattern of the speaker, when transitioning from a large diameter driver to a small one. Under reverberant conditions and/or listening off-axis this may have audible consequences.

Please feel free to add any technical material you may have on these speakers.

https://www.audioasylum.com/messages/speakers/48322/review-dunlavy-audio-labs-millennium-speakers-review-by-brian-a-at-audio-asylum

After many months of research I went with these speakers for the following reasons.
Extreme tonal accuracy, +/- 1dB from 20Hz to 20KHz.
Non-ported enclosure for clean bass.
Fabric dome tweeter for smooth treble.
Phase/time aligned for accurate transient reproduction.
Non-parallel cabinet walls to minimize internal standing waves.
Quick signal drop off in waterfall plots.
Clean pulse and step response.
Auditioned them and enjoyed the best sound I have ever heard!

It is hard to describe these speakers for I believe they are pretty much fully accurate and transparent. They totally disappear when playing despite their 76 inch height and 300 lbs. each weight. When you slip in a SACD/CD the wall dissapears and becomes a music stage for the musicians. Others have noticed this too and are quite dissapointed when they get home only to find their speakers don't do the disappering act, you can hear where each speaker is. Dunlavy's are matched to withen 0.5dB of each other to ensure this.

These speakers have a certain cleanness and accuracy that is very hard to describe. When I was at the factory in Colorado springs and did A/B comparisons with other Dunalvy speakers these just sounded more open. It was like the band was in the open, on a hill outside or something. With the other speakers, though they sounded great, the music was slightly veiled. I believe this is born out by the waterfall plots of the Millenniums, very clean and quick decay.

The soundstage of these is excellent. With some source material you can hear sounds coming from beyond the left and right of the speakers. Instruments are accurately placed across the area between, and beyond, the speakers. The speakers totally disappear, when the singer and drums are between the speakers, that is where the sound is, you don't hear any sound from the speakers themselves. The sweet spot is only wide enough for one though. However, anywhere in the room the sound is tonally balanced and enjoyable, you just don't get that nice balanced imaging you do in the middle. This is what totally turned me off of planer speakers, their horrible off axis tonal balance, and their laughable bass for that matter.

Perhaps the most noteable aspect of the Millenniums is there stupendous bass. It is so clean you sometimes think its lacking. There is absolutely no boom, overhang, thump, or distortion, even at high levels. I must admit I am used to hearing the 100Hz hump on most cheaper speakers that simulate a good bass response. I notice songs sound different. The bass is very clean and deep too. You can feel deep bass that you couldn't with lesser speakers. Lest you think these speakers are lacking in bass, if you play a song that truely has bass, these will reproduce it in spades. It is just amazing to listen to songs and for the first time hear and feel the bass/drum line of the song very cleanly. There is lots more detail and nuances to be found in the deeper few octives of music than I was aware of before.

The mids are flawless too. Voices are clean and undistorted. Dianna Krall sounds fabulous. Here music with the bass and piano sounds simply stunning. Celine Dion sounds excellent too. The harshness and forwardness of her voice is subdued to some extent, more enjoyable. Though with some of her songs, let's face it, she's really hollering. Men's voices also are nice, never nasally or boomy, always clean.

The treble is so clean and accurate, it captures the metalic sheen of cymbols and other metalic instruments but you need SACD to really enjoy this. There is no brightness, exageration, or harshness to be found, unless it is in the recording. When I compare the treble of these to that of my Paradigm Studio 100's in the home theater room, there is no comparison. Fabric dome tweeters are some much cleaner than metal domes, more natural and enjoyable.

The speakers themselves are a joy to look at. Their looks really grow on you. You start to appreciate their unique hourglass shape. It is so gracefull. My wife, who about flipped when she first say them, way too big and ugly as sin. Now she likes their looks. When we have visitors the women are usually amazed my wife allows me to have them. All the guys drool. You can tell there is some prime sound able to be produced by these massive transducers. The speakers are actually larger than I am, I'm 6-3 and 250 lbs. The speakers have an inch and 50 lbs on me. My son calls them the speaker gods.

About the only thing I can say bad about them is how they reveal poor recordings. Imagine my dismay when two of favorite groups as a teenager have some bad recordings, Fleetwood Mac and Abba. I love listening to SACD music with these. Horns and violins are richer and not strident as they can be with normal CD's. Cymbols are more metalic. The soundstage is enhanced.

Is this the perfect speaker? Probably not, but I am very happy with it. To me it sounded even better than Dunlavy's top of the line SC-V and SC-VI's. For someone with some money to burn, fly out to Colorado and listen to them for yourself. I don't think any dealer carries these for demos.

Read up on the manufacturer's website for the theory behind these speakers. The time alignment of the drivers, the hourglass shape etc. It is www.dunlavyaudio.com. Good reading.

This forum was created in remembrance of the late John Dunlavy and his contribution to both the art and science of audio reproduction which has lived on in many of the loudspeaker systems that he created over the decades and are still being used today. Not only that many of the original concepts developed by John Dunlavy such as baffle felt have been used by many other speaker designers with little or no credit given back to John.

Click here to view the all new Dunlavy/Duntech Archive Forum

We have moved to much larger new premises in the last month which has been a mammoth task. Now need to unpack everything and set up the lab again. Now we have twice as much area as before and no more distractions which has put us out of action for quite a while now

See here

https://analog-precision.com/forum/news-updates/we-are-moving-to-new-premises-!/

From Retearl of OzHifi.net

I have a pair of Cantatas & they are magnificent in my 25x40 ft room. They were a gift to me from John Dunlavy's daughter here in Colorado Springs. They were the ones he took home when he sold the company & retired. They will always be special to me since I have been a John Dunlavy admirer since he started the company here. He was likely the most talented scientist & engineer who has ever designed speakers! Truly! 30 years later, they can hold their own against ANY other speaker for accuracy & realism. I'm a blessed man!

audax_hm170c0_spec.pdf

264-1022--tymphany-d27tg35-06-spec-sheet.pdf

Did anyone bother to look behind this new DEQX Pre-8 at the recent stereonet audio show ? Perhaps you would have seen something similar to this where the 8-channel outputs were not in use and the box was just a glorified streamer. Wonder what the stereonet show guide said BTW has anyone taken the lid off ?

From the latest stereonet show report !! Looks like a rehash of last years show with still nothing finished

Attendees to this room were shown a range of new and old products. DEQX products are designed and developed in Australia as the cutting edge in digital signal processing. All were fixated on Kim Ryrie's explanation of what the DEQX system was designed to do (interview coming soon to our YouTube channel), who captivated his audience with a simple explanation of complex electrical engineering. The new Pre-8 series of processing hardware was on display in its elegant metal casework, and with the streamer section working, but DEQX was using the currently available Gen3 software and hardware platform for the DSP work. We are told that the final production units are almost ready to begin shipping, pending some final bug fixes.

A slim vertical 3-way loudspeaker without a passive crossover speaker system sat on stands with a subwoofer on either side of them. This was being transformed into a fully active time-aligned 4-way system driven by DEQX amplification. The Pre8 is a totally unique product as it features a full preamp with streamer, DAC and a NAS and phono amplifier, as well as the 4th generation DEQX brains. Sonically, the DEQX system had an effortless sound to it. Bass was taut and substantial, and provided a detailed midband with subtle treble without glare, and all this from within a hotel room. We look forward to the finished product based on what has been heard and seen from pre-production samples.

Gen-3 hardware  = 1st gen SHARC DSP aka ADSP-21065L LOL

And this from a facebook feed that I subscribe to. Note the comment below it. You just can't make this stuff up LOL

True to form, stereonet censorship. Don't want the punters engaging in free speech LOL

They should have focused on the turntable instead of being distracted by all of this so called exotic over-priced high-end imported bling ! They could have even developed other products. I mean seriously, $40k for an imported power cable and $50k for imported speaker cables !! You mean to tell me they couldn't develop their own cables instead of sending $$$$$ out of the country ? Just these two products alone are the price of the turntable but which has way more engineering involved ??

I saw those replies on ASR. The plot thickens May explain why they were still using the old DEQX product at the recent stereonet show otherwise the owner of the facebook page for which the following photo came from and for which is an OEM for DEQX products should have one of these beta DEQX units and should be spruiking it left-right and center on his face book page - right ?? Perhaps they can show us some pictures of the internals and tell us what CPU/DSP they are using otherwise it is starting to look like vapourware and the demo was nothing more than a glorified streamer And for those playing along at home I recall not so long ago when I was minding my own business on my own diyaudio thread trying to promote the 2nd gen Ultimate Preamps, I had to contend with a flood of DEQX fanboys desperately trying hard to detract people away from my products The same fanboys are again present on this thread but this time talking up a product that doesn't yet appear to exist. Go figure ! Like I have said before it is all part of being part of the club and has nothing to do with merit or achievement