[Jeffrey Hedback]

I have a nearly indescribable appreciation of AudioKinesis and Duke as a person and crossover genius (and I don't state that praise lightly).  The story goes back to last fall and this is simply a chapter to which the conclusion has not been written.  Last fall I spoke with Duke about building a set of custom monitors to be flush-mounted in a studio facility I've been working with for a couple years. 

Short version- the studio had hired me to correct an existing control room.  The challenges were to my reports without easy fix...there were acoustical, architectural and electrical issues beyond reasonable repair.  That led to the commision of "Control Room B".  The crux of the story is that the beautiful PMC MB2's seen in the attached pdf (this studio FMG Studios Control Room B is in fact being honored in MixOnline.com honorable mention studio design excellence Class of 2011...to post in June).  These highly misapplied PMC's were down tilted ~15 deg and given the specific 3-way design of this speaker it was simply a phase mess.  My hope was to pull the PMC's out of the soffits in Control Room A to be the free-standing anchors of Control Room B.  This (sorry I did say the short version...) is were Duke comes in...

He jumped on board and built a custom version of his Rhythm Prisms to be flush-mounted in FMG Control Room A.  So, they are built and arrived to my residence for review/approval (more on that below).  Part of that review is to bring the speakers to spaces to hear them in action. 

Chris Haughn is a client of mine near Evansville, Indiana.  I designed a fully blueprinted dedicated listening room to retro into his existing basement.  Construction was completed in Feb of this year and the equipment has been coming together step by step (special thank you to AC's own Ted Brady who's helped Chris by graciously offering his hard earned knowledge on synergistic gear!).

Recently, I visited Chris's room and brought the custom AK Rhythm Prisms...these are my cell phone pics of that visit.  Note that the AK's are voiced for flush-mounting and are lower in height than Duke's typical floorstanders.

The visit was exceptionally fun...sharing some of the approaches of speaker set, reference listening and some room tests.  I attached a spectrogram showing the LF control of the room.

As you may gleam, Chris is on the start of his audiophile journey's and is out of the gate is great stride.  One thing about the experience is that I had a tug in my mind wondering why the speaker's seemed touchy to set and very program dependent...turns out that Chris's Modwright LS100 pre requires the speaker cables one one side (amp or speaker) to be inverted as the pre inverts phase.  I know something was "off" but didn't think of this...ted figured it out in conversations after the fact.  That said, I have never heard "While My Guitar Gently Weeps" in a more impactful emotional way!!!

OK...enough of the diary entry.  Coming events however will include the installation of the AK's at FMG Studios Control Room A.  Also, Chris is in the process of speaker decisions and there will be updates in that room as well.

On these speakers, I have never heard a speaker more accurately reproduce the true waveform/envelope of instruments:









 synth patches, horns, kick drum, vocal captures.  In fact, I'm personally selecting the new Prisma's for my use and couldn't be more excited!!!!

Thank you Duke!

[Clio09]

That's quite a story and happy to hear more great things about Duke and his speakers. I've been a happy owner of Duke's speakers for 3 years now and use the flush mounted Jazz Modules with the TAD drivers. Never heard any speaker sound better in my system and I've had some good ones come in for comparison.

I'm curious as to the room treatments I see in the photos. Can you tell me more about them? Currently I use a combination of Realtraps Mini Traps and Eighth Nerve (long out of business) products. The panels I see in the photos look quite interesting.

[Duke]

Thank you very much, Jeff.  I'm very excited to be working with you on this and other projects, and glad that my approach to speaker design turns out to make sense from the perspective of a world-class room acoustics expert. 

Jeff's Prismas in black will be the first dedicated "prosound" pair, with higher power handling crossover components and a handle on the back to make it easier to move them around.

There's a thread on a Gearslutz forum that documents Jeff's role in "rescuing" a fledgling studio design concept and turning it into what Mix Magazine is recognizing as one of the top studio designs of 2011:

http://www.gearslutz.com/board/photo-diaries-recording-studio-construction-projects/460533-birth-my-studio-so-speak.html

http://www.gearslutz.com/board/good-news-channel/607007-stonewall-studio-honored-mix-class-2011-a.html

Jeff, pardon me for asking a rookie question, but could you explain what we're seeing in the spectrogram? 

It looks like neither listening chair is really in the central "sweet spot" - did that still work out okay?

And finally, is your foot really so big that you have to use two sets of shoe laces??

Clio09, Jeff is doing some very interesting things in that room, way way beyond what I'm used to as a room acoustics amateur.   If I might draw an analogy with Jeff's approach, it would be to crossover design.  Rather than just throwing a bunch of capacitance and inductance and maybe a little resistance at the speakers, a crossover designer tries to use the right combinations of each in the ways that give the best synergistic result.  And, sometimes those combinations are things most people wouldn't have thought of.  Likewise, Jeff uses the tools in his acoustics toolbox in ways the rest of us wouldn't have thought of, to deliver results far beyond we could hope to stumble into.  And his basic remote-room-analysis service starts at less than the price of a pair of interconnects.  Well, it depends on the interconnects, but you get the idea.

[Jeffrey Hedback]

wow, thanks Duke for the support.  As you and I have discussed earlier, I really do like the analogy between room acoustics design and crossover design.  Both deal with the recombining of energies to (hopefully) result in a true representation of the intended source.

Clio99, the wall panels are my HAR panels: Helmholtz Angled Reflector.  They are one of my designed solutions (custom milled and designed per each situation).  Above ~4K it scatters, due to the route through design and absorption behind it offers a Helmholtz benefit ~1-2K depending...what does it sound like...if one had a button to make sound "open", it might give this benefit.

On the spectrogram: it's similar to a birds-eye view of a waterfall.  What I'm really showing is the modal control.  You can also see how the AK's are extending down to 25Hz.  The primary room axial mode is less than 400ms @ 40dB down...BTW- that room is 15.5'x12'x8.5'.

On this room...it is still in final integration and set-up in some ways.  I mentioned how the speakers were in inverted phase due to cabling/pre conflict.  Chris had been listening this way for a couple weeks as he made his seating layout.  The room does sound best slightly off-center.  So funny are the powers of perception...Chris made a great choice based on the sound he heard.  I fully suspect that as this issue is resolved and whatever his final speaker choice is made, his seating location will shift to true center. 

Also, there are more touches to complete in the room and I'm sure I'll have real photos down the road (again, excuse the cell pics).

[brj]

I've only talked to Duke a few times, but have been impressed by both his grace and knowledge, which has only been reinforced by my limited exposure to his speakers.  I've never talked to Jeff, but have first hand witnessed the improvements his work can provide with before-and-after exposure to arthurs's and kj's rooms, both of which I've been lucky enough to spend many, many hours in over the years.  Any teaming between the two of them on a project seems destined to create impressive results - congrats to you both!

Jeff, I understand from looking at the plot that the bass in that room is impressively even in the bass region, but please let me poke at what small "unevenness" remains for the sake of understanding...

If I'm reading the plot correctly, you have the worst bass peaks at roughly 36 and 150 Hz, as exhibited by the red colored contours, followed by a lesser peak at maybe 110 Hz in orange.  (The worst null occurs at ~86 Hz, as exhibited by the blue "valley".)  What appears odd to me, however, is that the the worst peaks don't appear to be exactly where you have the most "ringing" of the room.  Yes, the 36 Hz mode takes the longest to die at almost 400 ms, but the next 2 longest decays at just over 300 ms occur at roughly 69 and 92 Hz - which is not exactly where we have the red or orange peaks.

Perhaps I'm only splitting hairs, especially as I don't know what level of smoothing you've applied.  (My understanding is that 1/3 octave smoothing approximates what people interpret from the mid-bass and higher, with 1/6 octave smoothing approximating what people perceive below the mid-bass region.)

Have I interpreted the plot correctly, and if so, can you comment on why the worst ringing doesn't always align with the highest initial peaks in the frequency response?  (I'm wondering about the power spectrum a bit, but it is too late at night for me to put those thoughts together in a fully coherent manner.)

Thanks!

[Jeffrey Hedback]

Hey brj,

great post because in fact there are things not good at all (which is why I showed the spectrogram).  Curious about this inverted polarity cause/effect, I've taken some measurements of the same speakers (Dukes custom RPs) in my open plan living room.  It just so happens that my space is pretty darn good with no treatments at all (although the t60 is ~.4 sec at 500Hz...yielding poor room dynamics compared to Chris's room).

Although we don't fully have apples to apples, I'm certain the answer to your question of the "odd" ringing vs freq response is the inv polarity.

These measurements are all both speakers with no smoothing.

I'll show a spectrogram in my room with proper wiring and one (exact same mic location and volume) with the cables inverted at the speakers.  If you see the additional ringing at ~50Hz...that is the invert polarity.  Audibly, the invert polarity sounds much worse than that small change.

Making a parallel to Chris's room, his is 15.5'x12'x8.5' (at least 40% smaller in volume than my living area)...the 36Hz is the primary room mode (X-axial), but those other ringing points are this invert polarity.

I'm also attaching an overlayed LF response of my room proper & invert polarity as well as Chris's (which is invert polarity).  You can see the dip@60Hz in my room from the inverted polarity (audible).  This is similar to what I heard in Chris's.

So Chris's LF response curve is nowhere near what it will be with final set of his speaker choice (end of day).  But at the same time, I have all the confidence in the world that it will end up in and great response range.  Would Chris's wiring have been proper that day, I fully suspect that I would have set Duke's speakers as well as adjusted the listening position toward that result. Unfortunately, there is not "Haughn with proper polarity" data with Dukes speakers.  I will however continue this story as those speakers load into the studio in Chicago and Chris's final speakers are placed and tested.

This really has struck my curiosity and I've found these studies very exciting.

[Jeffrey Hedback]

If anyone is patient (and curious) and wants to upload a stereo recording of me playing bass through the very same AK's shown in the Hedback graphs above, there is a YouSendIt link good until 6/11.  This is just a basic rootsy progression vamp with an outro that takes a quick turn in a different key.  Recorded using the same omni test mic (which was close to same location).  No compression or EQ on bass signal channel or recording.  The bass is one of my Fender P-Bass's (with a passive pick-up).

https://www.yousendit.com/dl?phi_action=app/orchestrateDownload&rurl=http%253A%252F%252Fwww.yousendit.com%252Ftransfer.php%253Faction%253Dbatch_download%2526batch_id%253DdkJwanZoSU9laFN4dnc9PQ&s=19072&cid=tr-cv-web-stnd-dl-litesend-null-c-19072