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Other Stuff => Archived Manufacturer Circles => AudioKinesis Loudspeakers => Topic started by: Duke on 4 Mar 2010, 04:28 am

Title: The Rhythm Prisms
Post by: Duke on 4 Mar 2010, 04:28 am
The small-room-friendly project I've mentioned elsewhere is now ready to be unveiled.  But my marketing department wants me to be sure and preface the unveiling by pointing out that the new AudioKinesis Rhythm Prisms actually DEFY THE LAWS OF PHYSICS!   (<- note impressive use of the caps-lock key)  That's right folks, they do the physically impossible:  They cram a 12" wide woofer onto the front baffle of a speaker that's only 11 inches wide!

(http://gallery.AudioAsylum.com/cgi/gi.mpl?u=2112&f=angled1.jpg)

(http://gallery.AudioAsylum.com/cgi/gi.mpl?u=2112&f=angled2.jpg)

The left channel speaker is the mirror-image of this one.

Their secret, of course, is that the angled front baffle is actually 13.5 inches across, so the 12" woofer (frame size = 12.3") fits easily as long as I don't try to flush-mount it.

The reason for the unorthodox geometry is this:  It allows the use of a large prosound woofer along with my recommended 45 degrees of toe-in without imposing an unduly wide footprint.  In constast, when toed in 45 degrees the Jazz Modules have a footprint a little over twice as wide.

The Rhythm Prisms have the following unusual features:

a)  Very good radiation pattern control (90 degrees in the horizontal plane from about 1.4 kHz on up), especially for a speaker only 11 inches wide.  The built-in toe-in avoids a strong early sidewall reflection and gives an unusually wide sweet spot (which I can explain if you'd like), and the relatively narrow vertical pattern of the waveguide horn (50 degrees) reduces the amount of early floor and ceiling bounce energy.   All of this works in favor of minimizing the undesirable very early reflections in a small room.

b)  Placement close to a wall, and even in a corner, is feasible.  A key factor here is the adjustability of the bass tuning system.  On the back of the enclosure are two ports, one at the top and one at the bottom.  These ports are offset to the inside, as the woofer cone is offset slightly to the outside.  When the speaker is placed close to room boundaries you seal off one of the ports because both of them would tune the enclosure too high.  This lowered tuning avoids bass boom and instead turns that boundary reinforcement into bass extension.  Embracing the principle of spreading out the low frequency sources in the room as much as is practical for the sake of smoothness, you can seal the lower port on one speaker and the upper port on the other.  Now there's significant staggering of your bass sources from the two speakers in all three dimensions.

c)  On the rear of the speaker is a single external resistor in a terminal cup, and this resistor acts as a tilt control for the compression driver.  It is bypassing a certain resistor in the crossover.  By changing the value of this resistor, the compression driver's output can be tilted up or down, which does a better job of adjusting for room acoustic conditions than an L-pad's shelving characteristic, and this single external resistor is much higher quality than all but very expensive custom L-pads.

d)  The drivers are high quality prosound units that have negligible thermal or mechanical compression in normal home use.  This preserves dynamic contrast, and thus preserves the emotion in the music because musicians often use dynamic contrast to convey emotion.

The Rhythm Prisms can easily be used in a medium or large room, and/or out away from the walls, in which case we'd leave both of the ports open.  The port lengths are also somewhat user-adjustable, allowing for further tailoring to a specific acoustic environment.  In a very large room, they would probably need subwoofer augmentation.

These are the speakers that, in prototype form, were judged in an informal blind listening test to be competitive with the more expensive Jazz Modules.  These are the speakers that killed my bipolar fullrange driver project, as for a few hundred dollars more the Rhythm Prisms offered a very significant improvement. 

One of the main goals of this project was to keep costs down, which meant that I didn't have the luxury of using bigbuck drivers that are easy to work with.  Instead I chose drivers that do what I want in the areas of dynamics and radiation pattern, and then designed a crossover that gets them to do what I want in the frequency response domain.  This required me to develop some new techniques (new to me anyway) in order to get satisfactory correlation between my measurements and what I was hearing.   I think I have preserved the dynamic capability of the drivers while achieving very competitive clarity and smoothness.  My marketing department still thinks I've defied the laws of physics (and I hate to burst their bubble).

Specifications:

Type:  Two-way controlled-pattern floor standing bass reflex system

Radiation pattern:  90 degrees in the horizontal plane from about 1.4 kHz on up

Impedance:  8 ohms nominal, tube-friendly

Efficiency:  93 dB/1 watt

Recommended amplifier power:  5 to 400 watts

Thermal compression:  Less than 1 dB at 50 watts (110 dB SPL)

Typical bandwidth, medium room:  45 Hz to 18 kHz

Typical bandwidth, small room:  35 Hz to 18 kHz

Dimensions:  44" tall by 11" wide; depth along long side = 20"

Estimated weight:  90 pounds

Pricing:  $2800.00 a pair, plus shipping

*  *  *  *

June 9, 2010 edit:  I wanted to post this photo on the front page of this thread.  This photo was taken by Albert Porter at the 2010 Lone Star Audio Fest in Dallas, and is used with his permission:

(http://gallery.AudioAsylum.com/cgi/gi.mpl?u=2112&f=LoneStar2010.jpg)

Thank you, Albert!

Title: Re: The Rhythm Prisms
Post by: Russell Dawkins on 4 Mar 2010, 04:57 am
Congratulations, Duke!  :thumb:

This is a logical and attractive design. I like floorstanders for their efficient use of space (and the buyers' money!). The 45ยบ angled baffle is the perfect solution for those who would rather have the backs of the speaker parallel to the wall.

High power handling coupled with high efficiency and an affordable price - what's not to like?

Oh, maybe the baffle being too narrow to flush mount the woofer. I think it would be the final touch for it to be grill cloth friendly for those difficult WAF situations.
Title: Re: The Rhythm Prisms
Post by: Duke on 4 Mar 2010, 05:29 am
Thanks, Russell!

I think I could build grilles if someone really wanted 'em, but if WAF is a top priority I'm probably not going to be competitive anyway. 

A round metal "waffle" grille could also be installed to cover and protect the woofer.

Now in theory there's a sonic improvement to be had from flush-mounting the drivers.  I A/B'd flush-mounted and non-flush-mounted drivers in the design stage and couldn't hear a difference, so went with the configuration that allowed me to keep the price down and the footprint narrow.  I'm not saying that no one could detect a difference (no claim of golden ears on my part), but I don't believe it's a significant factor in this case. 

Let me say a bit about the drivers I'm using.  They are fairly new, and have good but not "boutique" quality motors.  The compression driver uses a polymer diaphragm and has very good articulation in my opinion.  The woofer has unusually long excursion for a driver that has the articulation and top-end extension this one does, which means that it will stay linear at higher sound pressure levels than most people will ever approach at home. 

I am using the same drivers in my MRL (http://www.audiocircle.com/index.php?topic=70559.0) system, showcased in another thread.  The Rhythm Prisms have a better crossover than the original version of the MRL, so the MRL will get a crossover upgrade.

Duke
Title: Re: The Rhythm Prisms
Post by: poseidonsvoice on 4 Mar 2010, 06:03 am
Wow! Talk about, "Set it and Forget it."

Great work. There is definitely a market for controlled directivity loudspeakers that don't require multiple subs, when on a low budget, of course.

Anand.
Title: Re: The Rhythm Prisms
Post by: Duke on 4 Mar 2010, 08:35 am
Hi Anand,

Thank you very much.

Yeah, while I believe wholeheartedly in the multisub concept, in practice it's a very tough sell.  That being said, at some point I'll try the Rhythm Prisms with a Swarm and see how the integration goes.  I suspect that placing the RPs out in the room but using only the top port will give the best integration.

One application I want to explore is home theater without a center channel.  I think the RPs would work quite well in phantom center mode, which might be quite attractive if one isn't using a screen that the center channel can be hidden behind. 

Duke




Title: Re: The Rhythm Prisms
Post by: Duke on 4 Mar 2010, 11:09 pm
It occurred to me that I should probably include in this thread an explanation of why my speakers give such a wide sweet spot with that wierd 45 degree toe-in angle.

The ear determines the direction of a sound source using two mechanisms:  Arrival time and intensity.  With a normal setup (slight toe-in), when you move off to one side a bit the center image moves to that same side, but it moves farther than you did.  This is because the near speaker wins both arrival time and intensity.

With the Rhythm Prisms and their 45-degree crossfire configuration, for the off-centerline listener the near speaker naturally wins arrival time but the far speaker wins intensity.  This is because as you move off to one side, you're moving off-axis of the near speaker but on-axis of the far speaker, so it's actually louder.  Thus the two mechanisms tend to offset one another, and the central image remains near its original location.  This works better in some locations than in others (in other words it's not perfect), but it is a significant improvement over conventional speakers & setups.  At audio shows I often have listeners quite content to remain in a less-than-ideal off-centerline seat even when the coveted center seat becomes available because it sounds fine from over there (my other models have similar radiation patterns to the RP's in the horizontal plane).

Now there are two design elements that are crucial to this working out.  The first is, the off-axis output of the near speaker must fall off fairly rapidly in order for the farther speaker to be louder.  Second, the speaker's frequency response should fall off uniformly as we move off-axis so that the timbre doesn't change for off-centerline listeners, and indeed my speakers are very good at this.  The tonal balance will hold up well anywhere in the room, and even holds up through an open doorway into the next room.

This latter characteristic - the tonal balance holding up well even outside the room - is an indication that the spectral balance of the reverberant field is correct.  This is something unamplified voices and acoustic instruments do well, but relatively few speakers emulate.  I believe that when there's a significant discrepancy between the first-arrival sound and the reverberant energy the eventual result is listening fatigue.  This is because the ear/brain system is constantly analyzing incoming sounds to see whether or not they are reflections, and it does so by comparing them to "sound files" recently stored in short-term memory.  If it's a reflection, the ear ignores its directional cues.  If it's a new sound, the ear figures out where it's coming from.  The way the ear can tell whether or not a sound is new or old is by its spectral content, and it literally takes more CPU power to correctly classify a reverberant sound whose spectral match to the corresponding first-arrival sound is poor.  Over time, this extra CPU usage shows up as listening fatigue.

Since I'm in the habit of doing armchair analyses of loudspeakers by estimating their radiation patterns, I see a lot of correlation between radiation patten discontinuities and listening fatigue.  In particular, many speakers have a flare in the off-axis energy at the bottom end of the tweeter's range, ballpark 2.5 to 5 kHz, which happens to be right where the ear is most sensitive.  If the designer doesn't account for this (and make a compromise between on-axis smoothness and off-axis smoothness), such a speaker is likely to be fatiguing particulary in a small and/or highly reverberant room.

An additional (and more obvious) benefit to minimizing the spectral discrepancy between the direct and reverberant energy is more natural-sounding timbre.  The ear derives timbre from not only the first-arrival sound but also the reverberant energy.  In fact, in most listening situations the reverberant field conveys considerably more sound power to the ears than the first-arrival sound does.   

These are the types of things I try to take into account in my designs, because I believe they are audibly significant. 

Duke

Title: Re: The Rhythm Prisms
Post by: JoshK on 4 Mar 2010, 11:23 pm
Fantastic idea!  Very clever indeed.  Reminds me of some of the old NHT towers.

I'd imagine they'd make awesome surrounds in a HT too!
Title: Re: The Rhythm Prisms
Post by: Duke on 5 Mar 2010, 12:18 am
Thank you very much, Josh!

Good call on the NHT's.  Here's one of the models with the inward-angled front baffle:

http://www.blogcdn.com/hd.engadget.com/media/2009/02/20090224-nht_33.jpg

It looks to me like the NHT is using a much shallower angle, maybe 15 degrees or so, which probably had the effect of putting the listener on-axis.  So in that respect anyway, what I'm doing is different.  BUT as far as achieving the recommended toe-in without the speaker imposing a wide footprint, I'm obviously borrowing a page out of the NHT playbook, adapted to a Geddes-inspired radiation pattern setup.

Duke
Title: Re: The Rhythm Prisms
Post by: timjthomas on 5 Mar 2010, 12:38 am
Hi Duke,

If this question is not appropriate, let me know.  Based on your explanation, it seems to me that a 45 degree toe in would make sense for just about any speaker.

Is that correct?

-Tim
Title: Re: The Rhythm Prisms
Post by: gedlee on 5 Mar 2010, 01:50 am
Hi Duke

A little too much "fluff" for my taste.  Different speakers for left and right don't seem like a good idea to me when the same speaker pointed in two different directions does the same thing.  They look fine, but I don't like the sharp edges of course.

Good luck however, and I hope you can bring the verbage back down to earth sometime.
Title: Re: The Rhythm Prisms
Post by: zybar on 5 Mar 2010, 02:04 am
Hi Duke

A little too much "fluff" for my taste.  Different speakers for left and right don't seem like a good idea to me when the same speaker pointed in two different directions does the same thing.  They look fine, but I don't like the sharp edges of course.

Good luck however, and I hope you can bring the verbage back down to earth sometime.

Earl,

I know you are friends with Duke, but is your post really appropriate in Duke's thread where he is launching a new speaker?

If you think there is fluff or don't agree with something, send Duke and e-mail or PM.  Don't muck up his product thread.


Duke,

Best of luck with the new speaker.

George
Title: Re: The Rhythm Prisms
Post by: dnewma04 on 5 Mar 2010, 02:22 am
I would say that the 45 degree toe in would make the most sense with a speaker with constant directivity.  Depending on the seating position, it could also make sense for a non CD system like a cone/dome speaker configuration or a ribbon.  What could become a problem is if you are listening to a speaker system without CD, you can get significantly different sound than on axis. 

Title: Re: The Rhythm Prisms
Post by: drphoto on 5 Mar 2010, 03:13 am
 I like it. But I like offbeat looks. (I had a pair of norhs once) What's wrong the the idea of chirality?

 Seems like what I'm after, soundwise for a real world price. Count me as interested. I'm just glad to see designers addressing this issue of dynamics along w/ room interaction.
Title: Re: The Rhythm Prisms
Post by: Duke on 5 Mar 2010, 03:18 am
Based on your explanation, it seems to me that a 45 degree toe in would make sense for just about any speaker.

Is that correct?

Hi Tim,

Well, not really.   In order for the off-centerline soundstaging and tonal balance to hold up well, you need for the off-axis response of the near speaker to fall off rather quickly and uniformly.  You can try it with other speakers, but I can't promise good results.

*  *  *  *
Hi Duke

A little too much "fluff" for my taste.  Different speakers for left and right don't seem like a good idea to me when the same speaker pointed in two different directions does the same thing.  They look fine, but I don't like the sharp edges of course.

Good luck however, and I hope you can bring the verbage back down to earth sometime.

Hi Earl,

Welcome, and thanks for stopping in. 

The purpose of using mirror-imaged speakers is to reduce the footprint width required to get that 45 degree toe-in.  As I've cruised the internet boards it seems to me that a lot of people with very small rooms (like 10' by 12') are looking for something that works well in their limited space, and most of them can't devote a lot of floor space to the speakers.  And at the same time, what a small room really needs is good radiation pattern control along with proper aiming of those patterns (which are things you taught me).   Hence I perceive an opportunity to bring good pattern control to the rooms that arguably need it the most.

So much for cutting back on the verbage!

*  *  *  *

Zybar, I appreciate your intentions.  Earl speaks his mind and if he bothered to wish me good luck, he meant that too.

*  *  *  *

dnewma04, in my opinion your analysis is correct, but to be precise it's a fairly narrow constant directivity that works best.  An omni system has constant directivity, and better than normal off-axis soundstaging, but I think the configuration I use (the essentials of which I learned from Earl) does a better job in this regard than an omni.
Title: Re: The Rhythm Prisms
Post by: Brett on 5 Mar 2010, 05:17 am
I've just seen this linked from another forum. Flippin awesome.

You just keep coming up with interesting designs. All the best with success for these.
Title: Re: The Rhythm Prisms
Post by: Duke on 5 Mar 2010, 07:03 am
I like it. But I like offbeat looks. (I had a pair of norhs once) What's wrong the the idea of chirality?

 Seems like what I'm after, soundwise for a real world price. Count me as interested. I'm just glad to see designers addressing this issue of dynamics along w/ room interaction.

Thanks, drphoto!

I think that, subjectively, the RPs are especially competitive in the area of dynamics and liveliness (the kind that makes it hard for you to sit still).  Take this with a grain of salt of course considering who it's coming from, but I think that's what will stand out about them in comparison to other speakers in their price range.

*  *  *  * 

I've just seen this linked from another forum. Flippin awesome.

You just keep coming up with interesting designs. All the best with success for these.

Thank you, Brett.  I don't see much point in doing a "me too" design, as then I have to rely on marketing.  If nothing else I hope to make the marketplace a bit more interesting by putting some unorthodox alternatives out there.  In that sense, the Rhythm Prisms are probably as radical as I'm likely to get for a while.

*  *  *  *

My intention is to have "expensive, relatively few compromise" speakers at the upper end of my product line, and "more affordable, but inevitably more compromised" speakers at the lower end.  Instead of scaling by size, I'm scaling by parts and enclosure cost, so that my less expensive models (headed by the Rhythm Prisms) don't compromise on dynamics or radiation pattern control in the horizontal plane.  The Jazz Modules and Dream Makers and Planetariums are going to be a bit more refined, but then they should be considering their higher prices.

It's a juggling of tradeoffs, and if I was making the exact same tradeoff choices as someone else, what would be the point? 
Title: Re: The Rhythm Prisms
Post by: Paul W on 5 Mar 2010, 02:57 pm
Hey Duke,

You've scored another innovative design!  Keep up the good work!

(I like the fluff :)

Paul
Title: Re: The Rhythm Prisms
Post by: EthanH on 5 Mar 2010, 03:23 pm
Very cool concept.  I would imagine that with the 12" driver the speakers would go down to 45hz with some authority (a two-way with a 12" woofer that extends to 50hz sounds very different from a 5" driver that extends to 50hz, in my experience), but would you say that the speakers sound full range in-room without a sub?  Just curious.
Title: Re: The Rhythm Prisms
Post by: launche on 5 Mar 2010, 05:24 pm
I've always liked your thought process and designs Duke.  I think your new direction will be welcomed.  In the past I felt many of your designs were a little too large and expensive (less accessible) for the average hobbyist.  But you as a designer appeared very down to earth, helpful and humble (more accessible).  Now to me it appears your philosophy, designs and character are coming together to reach an accessible point for more people to enjoy what you offer to the audio community. 

Hope that makes sense and good luck.
Title: Re: The Rhythm Prisms
Post by: Abby356 on 5 Mar 2010, 05:54 pm
Having had the pleasure of meeting Duke before I feel compelled to second what member "launche" just said. These seem like a very accessible speaker from a very accessible guy. All can say is that I sure hope these will make the trip to LSAF this year...pleeease...

Regards, Daniel.
Title: Re: The Rhythm Prisms
Post by: Duke on 5 Mar 2010, 07:33 pm
Paul W, thank you very much!  I wasn't sure if they'd come across as "innovative" or "just wierd", and it sure is nice to see a positive initial reaction from you and others.

*  *  *  *

EthanH, while room size & acoustics play a role, the Rhythm Prisms do sound "full range" in my 15-by-18 foot open floorplan living room.  Now they don't make the room shudder on low synthesizer notes like the Swarm does, but they definitely have that "hits like a big woofer" thing going on. 

And I must confess that I do not understand why a big woofer has more subjective impact than a small woofer even if the latter looks better on paper.  It might have to do with thermal and mechanical compression in the small woofer, but that's just a guess. 

*  *  *  *

Hi launche, and thanks for your comments and support.   

Yeah I have long wanted to offer something in a lower price range that did most of the things I believe in.  The roots of the RP's go back to a bass guitar project I worked on last year.  In the bass guitar cabinet market, bang-for-the-buck is everything because a musician wants to put money into his instrument, not the cabinets he plays through.  Anyway I sent a prototype two-way bass cab to a bass player for beta-testing, and he liked what he heard.  He could tell the cab was fairly smooth and extended, so his band (which I guess would be called a rock-and-roll oldies cover band) tried it out on vocals.  Well they liked it so much in that role that they wanted a pair to use as portable vocal PA speakers in small venues that didn't have a decent house PA system.  So I started working on refining the crossover with the idea that this speaker needed to sound very smooth and clear on vocals, and from that effort the MRL (pronounced "Merle", stands for Multi-Role Loudspeaker) arose.  Thus the groundwork was in place for the Rhythm Prisms, which went through yet another generation of crossover refinement along the way.   

So that's how I ended up being able to do a more "down to earth" speaker. 

*  *  *  *

Hi Abby356,

Thanks for your kind words.

I don't yet know whether this will be the model that shows up at Lone Star; there are two more models of the same generation in the pipeline.  Interest on the part of people like you (and space limitations in my car) will determine what I bring.

*  *  *  *

On another forum someone asked if the Audio Kharma "Econowave" project inspired the Rhythm Prisms.  They both use the same waveguide-style horn, but the prosound projects described above were well underway before I knew about the Econowave project.  When researching options for the two-way bass guitar cab I found that horn on the Parts Express website and ordered one to measure, and it measured significantly better than anything else I'd tried in that size/price range.  I'm not using the same compression driver as the Econowave project, and don't know what its crossover looks like but there are probably some differences there as well.

That being said, Audio Kharma member Zilch initiated the Econowave project over a year before I'd even contemplated a prosound speaker, much less adapting such to a home audio application.  I tip my hat to him on recognizing the potential of that horn and initiating the Econowave design(s).  Unfortunately I've only skimmed a few pages of the Econowave mega-thread.
Title: Re: The Rhythm Prisms
Post by: jsaliga on 6 Mar 2010, 04:24 pm
These look awesome Duke.  Congrats on bringing a high quality and affordable speaker to market.  I know you mentioned these speakers to me when I was trying to choose between the Jazz Modules and the custom Planetarium Alphas.  I ended up picking the Alphas and still believe they were the best choice for my particular needs.  But man these Rhythm Prisms look to be yet another compelling offering in your product lineup.

--Jerome
Title: Re: The Rhythm Prisms
Post by: Zilch on 6 Mar 2010, 06:58 pm
Thank you, Duke, for acknowledging the efforts of the AudioKarma collaborative.

We are all working toward the same objectives, and I wish you great success with your new products....   :thumb:
Title: Re: The Rhythm Prisms
Post by: Duke on 6 Mar 2010, 08:03 pm
Hi Jerome, thanks for the thumbs-up!

The speakers you have on order are probably better to significantly better in just about every way... except maybe maximum SPL capability and of course price. 

*  *  *  *

Zilch, I really am impressed that you saw the potential of that JBL waveguide (I use the Pyle version with the metal threads).   I had probably seen it a dozen times on the Parts Express website but simply didn't pay any attention to it, until the time I was looking specifically for a 12" wide 90-degree-horizontal constant-directivity rectangular horn for a prosound project.  What was it that initially caught your attention about it? 

Title: Re: The Rhythm Prisms
Post by: Zilch on 6 Mar 2010, 10:56 pm
Zilch, I really am impressed that you saw the potential of that JBL waveguide (I use the Pyle version with the metal threads).   I had probably seen it a dozen times on the Parts Express website but simply didn't pay any attention to it, until the time I was looking specifically for a 12" wide 90-degree-horizontal constant-directivity rectangular horn for a prosound project.  What was it that initially caught your attention about it?

I began attempting to DIY JBL 4430s in late 2004 with Progressive Transition waveguides.  By May, 2005, I had acquired some of them, and first had access to measurement capabilities.  The "discovery" is documented here, at Post #7:

http://www.audioheritage.org/vbulletin/showthread.php?t=6050

I completed several projects using them in '06 and '07, first mating them with inexpensive Selenium drivers in early '08, and AK's EconoWave collaborative was born in late February.  Earl measured them for us in May '08, and despite his scathing critique, it was clear we had a winning combo for entry-level DIY constant-directivity builds.

The AudioKarma mega-thread chronicles the fun we all have had (and are having) learning about and hands-on exploring the techology, with the help of many contributors, including your friend Wayne Parham, among others....  :D
Title: Re: The Rhythm Prisms
Post by: cryoparts on 6 Mar 2010, 11:05 pm
I want a pair!   :drool:

Bring a pair down, we'll do some listening!

Lee

Edit--have Lori bring a "smoke lamp"!
Title: Re: The Rhythm Prisms
Post by: cryoparts on 6 Mar 2010, 11:07 pm
If you think there is fluff or don't agree with something, send Duke and e-mail or PM.  Don't muck up his product thread.

Indeed.   C'mon...can we keep this place friendly and have members of the trade (including myself) not talk s**t  about each other?  Duke is one of the "good guys", he and Lori are true gems of this industry, and they make a fine product.

Lee
Title: Re: The Rhythm Prisms
Post by: Duke on 6 Mar 2010, 11:24 pm
Thanks for that link, Zilch.  Very interesting.  You know, Earl's speakers were 4430s before he started working on the Summas, and conceptually the Summas were an update of the 4430 concept.

In 2001, ignorant of the 4430s but with my little wheels a-turning, I first contacted Earl with a request for a 90-degree constant-directivity waveguide to be used with a 2" throat compression driver and crossed to a 15" woofer at about 1 kHz - conceptually pretty close to the 4430 (at the time I didn't think a 1" throat driver could go that low).

Anyway I find it interesting how the 4430 keeps coming up among people who value constant (or at least intelligently controlled) directivity.  Wayne Parham has a link to the AES paper describing the 4430 on his website.   I wouldn't be surprised if Bob Smith (SP Tech/Aether Audio) has a 4430 connection as well.

Here's the link to the paper on the 4430 hosted on Wayne's site, for anyone interested in what this "4430" is that I've been carrying on about:

http://www.pispeakers.com/AES_v31_n6_p408.pdf

*  *  *  *

Hi Lee, great to hear from you!  I sure appreciate the write-ups on my stuff from LSAF that you have on your website. 

Don't jump on this one just yet; there's two more related systems that are about to go public.  I'll try to get one of them posted this evening.

If you're serious about me bringing a pair down, shoot me an e-mail.  duke at audiokinesis dot com. 

Duke


Title: Re: The Rhythm Prisms
Post by: cryoparts on 7 Mar 2010, 02:28 am

*  *  *  *

Hi Lee, great to hear from you!  I sure appreciate the write-ups on my stuff from LSAF that you have on your website. 

Don't jump on this one just yet; there's two more related systems that are about to go public.  I'll try to get one of them posted this evening.

If you're serious about me bringing a pair down, shoot me an e-mail.  duke at audiokinesis dot com. 

Duke

I'll be in touch, after you announce the other products in the pipeline.

My pleasure, your speakers were the highlight of LSAF for me all three times I attended.

Peace,

Lee
Title: Re: The Rhythm Prisms
Post by: Duke on 7 Mar 2010, 02:58 am
Thanks, Lee.

Here's (http://www.audiocircle.com/index.php?topic=78669.0) one of them.

And here's (http://www.audiocircle.com/index.php?topic=79325.0) the other.
Title: Re: The Rhythm Prisms
Post by: James Romeyn on 7 Mar 2010, 06:00 am
All I can add is....GO DUKE!  Love the design!  Congratulations!  Can't wait to hear it.   

Title: Re: The Rhythm Prisms
Post by: Duke on 9 Apr 2010, 05:51 pm
Someone sent me an e-mail asking specifically about "horn honk", and I thought it would be a good idea to post part of my reply here.

Horn honk is probably the great unspoken reservation people have upon first seeing the Rhythm Prisms, and I don't blame them a bit.  Most prosound horns have honk and/or harshness that makes them unpleasant to listen to, and many horn systems for home audio have the same problem to some extent.
 
Unfortunately my new generation of speakers hasn't yet been outside my living room at this point (early April 2010), so there are no independent assessments of their sound.  But there is a great deal of commentary on the sound of a well-respected DIY project that uses the same horn, and that provides relevant information.
 
On the AudioKarma website is a massive megathread and several related threads about a DIY project called the "econowave" (it uses an inexpensive waveguide-style horn with an inexpensive compression driver - hence the name).  The horn I use is the same one, though I didn't realize it was already quite popular in DIY circles when I first "discovered" it, while researching horns for a high-end bass guitar cabinet.  Here is a thread that gives a brief introduction; see in particular posts 3, 5, and 22:
 
http://audiokarma.org/forums/showthread.php?t=197859&highlight=econowave
 
Here is the AudioKarma megathread if you're so inclined.  Over ten thousand posts; I have not and do not intend to read it, though I have skimmed parts of it:
 
http://audiokarma.org/forums/showthread.php?t=150939
 
Now what is interesting about the econowave project is its massive popularity among DIYers who started out with a healthy anti-horn prejudice.  Here is a clickable list of econowave projects, click on the names and you can read comments by some of the builders:
 
http://audiokarma.org/forums/showpost.php?p=2260584&postcount=2409
 
Now let's get into why I think my speakers are significantly better that the best of the econowaves:  First, my crossover kung fu is mas macho; and second, I'm using a better compression driver.
 
In the curves that I've seen on the econowave thread, I can see evidence that the builders are either overlooking or not adequately dealing with a couple of issues.  Now in all fairness it took me several solid weeks with some pretty good test equipment to appreciate the consequence of these issues and figure out how to deal with them.  The econowave project is an excellent design, but I believe that my speakers using the same horn incorporate two refinements that are worthwhile. 
 
The compression driver I'm using is a fairly expensive unit that I had to import from Europe, though US distribution should be in place by now.  I believe it to be the finest driver of its type for this application, and I have tried all of the likely contenders or their equivalents.  My driver uses a polymer diaphragm and is smoother-sounding than the metal diaphragm drivers, and its internal geometry allows a better transition to the horn's relatively wide flare in the horizontal plane.  I will reveal its identity to my customers so that if I hit a moose one night they can get replacements if they ever blow a driver (unlikely).

I have not encountered any online commentary saying  "I heard the econowaves and they have horn honk" or words to that effect, and I looked hard to find anything like that before writing what you see above.  I'm not saying no such comment exists, but the trend is in the opposite direction:  The econowave continues winning over people who hate horns.  My claim is that my speakers that use the same horn are even further removed from having audible horn coloration.
Title: Re: The Rhythm Prisms
Post by: Russell Dawkins on 9 Apr 2010, 06:34 pm
All I can add is....GO DUKE!  Love the design!  Congratulations!  Can't wait to hear it.   
+1! I really think you are on the right track, Duke, in concept and pricing.
Title: Re: The Rhythm Prisms
Post by: bluemike on 9 Apr 2010, 06:36 pm
I've always been impressed with Duke's designs ..nothing has changed here

Good work
Title: Re: The Rhythm Prisms
Post by: James Romeyn on 10 Apr 2010, 02:49 am
DUKE!!!  I'm ten minutes south of you! (We'll, about "tree" minutes in an F-15 minus afterburner, longer by Mazda).  Call me and let me hear them!

PS: I'll bring the flat top you heard Valentine's Day, and a guitar preamp, whose output will go into your amp to drive the new Rhythm Prism.  How will that be for a test to detect horn honk?     

Sleepless in Providence Utah... 
Title: Re: The Rhythm Prisms
Post by: pardales on 24 May 2010, 05:35 pm
Could you say a little more about what is a proper set-up for these speakers? Can they be placed near wall?
Title: Re: The Rhythm Prisms
Post by: jimdgoulding on 24 May 2010, 07:57 pm
This is a pretty old thread, huh.  They made it to LSAF but I don't think they made it back.  Think Duke sold em to a local.  Bet he is a happy cat, too.  The customer, I mean.  Sounded awesome to me and I'm not fond of any speaker that calls attention to itself. 
Title: Re: The Rhythm Prisms
Post by: Duke on 24 May 2010, 08:48 pm
Could you say a little more about what is a proper set-up for these speakers? Can they be placed near wall?

Near-wall placement works fine, either near the sidewalls or up against the wall behind the speakers.  At Lone Star, I had the Rhythm Prisms about five or six inches out from the wall behind them, and the left-hand speaker was about eighteen inches in from the side wall as I recall.   Here's a picture:

http://www.audiocircle.com/index.php?topic=80966.msg781316#msg781316

We were getting a lot of bass reinforcement, as is typical of hotel rooms, so I plugged the top port on one speaker and the bottom port on the other.  This lowered the tuning frequency to about 26 Hz, and introduced some vertical staggering of the low bass sources (desirable from the standpoint of bass smoothness).   

Comments were quite positive; here are a few that ended up online (inserted 6-10-10):
 
"I was most impressed with the [AudioKinesis Rhythm Prism] speakers I heard today.  They had an open and airy sound and really great range that seemed to flow effortlessly.  I'm not the most critical listener but first impressions are usually correct and you really hit it out of the park.  Fantastic stuff and good luck to you and your team."
 
"Audio Kinesis in house made speakers... were for me making some of the very best sound at the show. Human voices were so amazingly real, and the whole set up just had a really musical vibe if you will to the whole thing. Was happy to have been lucky enough to have experienced that room."
 
"Duke's speakers - he'll need to tell about this new model - were sweet and delicate and lithe on Simon and Garfunkle Live in Central Park and as dynamic, clean and hugely emotional on Hugh Masekela's Stimela [the Train Song] as anytime I've heard that tune with the little Lighter Note preamp and, get this, powered by the amplifier in a small NAD integrated.  Seriously, they played both these live recordings like they were made for them with generous sized imagery and space."
 
See also OzarkTom's post on page 3 of this thread.
Title: Re: The Rhythm Prisms
Post by: ttan98 on 24 May 2010, 11:49 pm
Duke,

Nice looking(color is a little old fashion) and is very well priced speakers. I have no doubt it will sound good as well esp. one designed from you.

I have a similar horn that you use in this model, can you give me a hint(brand and model) what 12" driver you use?
Title: Re: The Rhythm Prisms
Post by: Duke on 25 May 2010, 02:22 am
can you give me a hint (brand and model) what 12" driver you use?

That's the Eminence Kappalite 3012LF.  Not the easiest to work with as you'll see from the factory curve, but its dynamic capability is pretty awesome, both thermally and mechanically.  It can move more air than most 15" woofers.  And at the other end of the scale - that is, at low volume levels - it is still articulate.  In fact one of the first people to visit my room at Lone Star commented specifically on how the system sounded good at the relatively low level it was playing.  He had an SPL meter, and clocked it at upper 70's as I recall. 

On another note, believe it or not I actually got positive comments on how they look from women who came into the room at Lone Star.   Now presumably these were the wives of audiophiles and therefore had seen much worse, but still that was a nice surprise.
Title: Re: The Rhythm Prisms
Post by: panomaniac on 25 May 2010, 03:12 am
A system that can retain its character and resolution while you turn down the volume  - is a very good system indeed.  It's a hard test.   You're on the right road, for sure.
Title: Re: The Rhythm Prisms
Post by: OzarkTom on 25 May 2010, 01:08 pm
It was a huge pleasure tp meet Duke and his fine Prisms at LSAF. As am audiophile for 40 years, a high-end dealer for 15, I have my preferences of what works and what don't. When I first stuck my head in the room and saw the horns, I immediately judged the speaker and walked by the room. Every horn speaker I have ever heard always screamed at me one way or the other, I hate horns.

But since I was there for a couple of days, I found myself back into his room. Duke sure made me eat those thoughts. Smooooooth, musical, and detail.....it was awesome. I went back more than a few listens, I knew they were going to start screaming at me eventually, I was wrong. And what a value. You can buy these with that little Virtue One.2 amp for less than 3K. If you are just starting out or have Hi-Fi burn-out, just get this package and you will have that musical magic that many systems costing several times more fails to give.

Thanks Duke!

Title: Re: The Rhythm Prisms
Post by: pbrstreetgang on 4 Oct 2010, 02:27 am
Any more thoughts on these that are out in the field?
Title: Re: The Rhythm Prisms
Post by: jimdgoulding on 4 Oct 2010, 03:04 am
I went.  I doubted.  I was undoubted.  Very nice, dynamic and detailed sound.  Something I think a person could live with for a long time.
Title: Re: The Rhythm Prisms
Post by: James Romeyn on 4 Oct 2010, 03:09 am
I appreciate, believe in, and recommend one of Duke's speakers tests: notice the aural effects in a room next to the speakers.  It's funny, but when you think about it, you don't need to enter a room to know whether it's live or reproduced.  As John Atkinson wrote several months ago, you can tell walking down the street, a few buildings away, through an open window whether it's recorded or live, even if "live" is an amplified electric guitar.  It's a good test.  Duke knows his stuff. 

RMAF is pretty centrally located.  You could do worse than buying a plane ticket to Denver, esp, (cough, cough) because it appears Duke's launching new technology (I think it's an appropriate word) at the show.

The Jazz Module and Dream Maker are among my favorite audio bargains, especially considering its moderate power requirements. 
Title: Re: The Rhythm Prisms
Post by: pbrstreetgang on 4 Oct 2010, 03:53 am
For sure going to RMAF would be nice but I cannot as I am on weekend shifts.
Title: Re: The Rhythm Prisms
Post by: James Romeyn on 4 Oct 2010, 04:14 am
I went.  I doubted.  I was undoubted...

That's a hoot, Jim! :lol:
Title: Re: The Rhythm Prisms
Post by: Parkfly on 3 Nov 2010, 02:38 am
Quote
Any more thoughts on these that are out in the field?

Here are mine:

http://www.audiocircle.com/index.php?topic=87553.0

Parkfly.
Title: Re: The Rhythm Prisms
Post by: gonzoyoyo on 15 Nov 2010, 11:23 am
I am interested by these speakers, and I am wondering if they are suitable for any kind of music.... Thank you for your input.
Title: Re: The Rhythm Prisms
Post by: panomaniac on 15 Nov 2010, 11:39 pm
I did not hear them play big orchestral works, but the other styles I heard on them were quite good.  Solid bass but never boomy.
Title: Re: The Rhythm Prisms
Post by: gonzoyoyo on 16 Nov 2010, 03:30 am
Thank you. Do they perform well with rock, jazz, etc????
Regards.
Title: Re: The Rhythm Prisms
Post by: Duke on 16 Nov 2010, 08:44 am
Hi Gonzo,

Well my opinion is probably (cough cough) a bit biased, but aside from pipe organ or heavy synth the Rhythm Prisms aren't really limited by music genre.  Rock, jazz, etc. is a piece of cake.   They can of course be positioned to maximize boundary reinforcement and the bass tuning adjusted accordingly, if you do want to explore pipe organ and/or heavy synth. 
Title: Re: The Rhythm Prisms
Post by: panomaniac on 18 Nov 2010, 02:59 pm
Rock, jazz, etc. is a piece of cake. 

I would say yes, for sure.  Big, full sound.  Plenty of satisfying weight and power.  High resolution, but not "lightweight" at all. Great dynamics, too.
Title: Re: The Rhythm Prisms
Post by: gonzoyoyo on 21 Dec 2010, 09:03 am
They remind me of some Tannoy speakers... Would the sound be comparable?
Title: Re: The Rhythm Prisms
Post by: Duke on 22 Dec 2010, 05:11 am
They remind me of some Tannoy speakers... Would the sound be comparable?

Which Tannoy speakers?  I'm under the impression that most, if not all, Tannoys use a concentric tweeter, which is a significantly different approach in my opinion.

In theory the concentric format inherently does some things better, and having a separate waveguide or horn inherently does some things better.  I've worked with concentrics a bit, and at one time showed a pair at an audio show but never went into production with that model because another company came out with a kit that was very similar.   

I can only recall hearing one Tannoy speaker, which was a large high-efficiency 12" or 15" two-way concentric in a vintage-style cabinet. 
Title: Re: The Rhythm Prisms
Post by: pslate on 19 Jan 2011, 07:26 pm
How might the Rhythm Prisms compare to a stand mount monitor? I am thinking something with relatively low sensitivity and big sound from a small container without waveguides (as is popular these days). I know this is a pretty subjective question, but I wondered if anyone had some thoughts on the topic. Just wondered how this might compare to a traditional Scanspeak revelator or illuminator set up, what the advantages are with each approach. 
Title: Re: The Rhythm Prisms
Post by: Duke on 20 Jan 2011, 07:25 am
How might the Rhythm Prisms compare to a stand mount monitor? I am thinking something with relatively low sensitivity and big sound from a small container without waveguides (as is popular these days). I know this is a pretty subjective question, but I wondered if anyone had some thoughts on the topic. Just wondered how this might compare to a traditional Scanspeak revelator or illuminator set up, what the advantages are with each approach.

That would be a most interesting clash of philosophies! 

The high-end conventional (Scanspeak) approach has the theoretical advantage in best imaging for one, as well as inner detail.

The Rhythm Prism approach has the theoretical advantage in sweet spot width, macrodynamics, and compatibility with a wider range of amplifiers.

That leaves a whole lot of potentially disputed territory:  Naturalness of timbre, freedom from listening fatigue, freedom from coloration, bass extension and quality, impact, midrange clarity, coherence, suitability to a wide variety of music, sounds the most like live music, sounds good at a wide range of loudness levels, lets you hear the most variation from one recording to another, and probably a lot of other stuff I can't think of right now. 

Now, why would naturalness of timbre be in dispute?  Conventional wisdom no doubt holds that a small high-quality woofer and tweeter will sound more natural than a big prosound woofer and horn.  Well, my theory is that the reverberant field matters a lot more than is generally appreciated, and my design pays a lot of attention to getting it right.  Whether that will tip the scales, I can't say for sure without an actual comparison. 

Likewise with freedom from coloration.  A horn is inherently a higher-coloration device than a dome or ribbon tweeter, if we look only at the on-axis response.  But once we factor in the off-axis contribution, a good waveguide-style constant-directivity horn may end up being highly competitive.

There are some very good conventional-style stand-mount speakers on the market, and it's rather presumptuous of me to expect a prosound-type speaker to compete with them on their home turf.  More than likely each speaker would have its relative areas of superiority, leaving the final choice a matter of personal preference and prioritiy to a certain extent.  But in my opinion at least (which cannot possibly be biased!!), there's enough uncertainty about the relative merits of the two opposing philosophies in a small-room domestic setting to make a direct comparison potentially quite interesting. 

I'd like to hear the thoughts of others who are, theoretically at least, less biased than myself.
Title: Re: The Rhythm Prisms
Post by: pslate on 20 Jan 2011, 02:04 pm
Thanks Duke for the kind reply to a not so easy question  :D Well said too. In a perfect world I would have an excellent electrostat, standmount, and constant directivity speaker. Let me know if you hit up AK Fest!
Title: Re: The Rhythm Prisms
Post by: Russell Dawkins on 20 Jan 2011, 07:52 pm
I would jump at the opportunity to compare a good example of the high efficiency, controlled dispersion approach to a top end conventional 2 way with lower efficiency and the changing dispersion through the crossover region.

I gather that the latter would offer slightly lower distortion through the range covered by the bass/mid, but only at low levels. Once the levels pick up to "approaching live"  I would imagine the distortion advantage would go to the pro-sound-type driver.

I would imagine basically the same for the naked vs waveguide-loaded HF driver - lower distortion at low levels but higher at high levels for the unaided dome/ribbon, although it would appear that the Raal ribbon might be an exception, both in efficiency and high power handling.
Title: Re: The Rhythm Prisms
Post by: Richard in Idaho on 31 Jan 2011, 04:53 am
Couple of questions.

Where are your speakers made?

Can someone listen to you speakers there in Preston. If it ever warms up a bit I would like to drive over to your area.

Thanks
Title: Re: The Rhythm Prisms
Post by: Duke on 31 Jan 2011, 11:36 am
Hi Richard,

My cabinets are manufactured by Swainston Mill & Cabinet, here in Preston.  I do the crossovers and final assembly.  Depending on the model, the drivers come from the US, Italy, Spain, Taiwan, and/or China.

Call or e-mail me to see what I have on hand before you make a road trip; I usually have one or two sets of speakers but seldom more than that.  My e-mail is audiokinesis at yahoo dot com, and my landline is 208-852-2610.

Duke
Title: Re: The Rhythm Prisms
Post by: pslate on 10 Feb 2011, 08:51 pm
What might a good rule of thumb for current lead-times? I'm saving diligently for a new rig, and the Prisms sure do look good.  :thumb:

Paul

Title: Re: The Rhythm Prisms
Post by: gonzoyoyo on 10 Feb 2011, 08:56 pm
I would love to audition them.....
Title: Re: The Rhythm Prisms
Post by: Charles Xavier on 10 Feb 2011, 09:12 pm
I would love to audition them.....


X2
Title: Re: The Rhythm Prisms
Post by: pslate on 10 Feb 2011, 11:08 pm
I'm in the Chicago region if I purchase :D BTW the windy city needs a local chapter on AC or at least a GTG. I'm sure there would be a bunch of folks who would be game.
Paul
Title: Re: The Rhythm Prisms
Post by: Duke on 12 Feb 2011, 04:13 am
Pslate, lead time is ballpark 8 weeks or so, depending on how many jobs my woodworker has in line ahead of me.