[Christof]

After reading the comments relating to Rythmik products, in Drakes post about sub amps, I am left wondering how good this Servo kit(s) is.  I am tossing around the idea of building this http://www.zaphaudio.com/BAMTM.html  design done by Zaph for a HT system and I'm wondering how this http://www.rythmikaudio.com/servo_product.htm Rythmik Servo #1 kit might do mounted in one of these 2ft.^3 enclosures?  My other option is a 12"XLS I have left over from another project with a PE plate amp.  Any comments on how you feel the Rythmik Servo will integrate with the Zaph design vs the peerless would be greatly appreciated.

[DSK]

I built my sub using the Rythmik DirectServo kit in a sealed 2.0cu.ft. box with 1.5" MDF walls (box in box), full shelf braces supporting all panels, etc. It weighs 93lbs (42kg) so I won't be moving it anytime soon. Very flexible settings and is flat to below 20hz in my room, selectable Q of 0.5, 0.7 or 0.9. Very quick, tight, articulate, clean & musical and easily outperformed my M&K MX-125, father's Velodyne, friend's Klipsch, and other models (Klipsch, B&W, REL, M&K, Yamaha etc) that I've heard in shops. Even if I had a spare $5k in my pocket I wouldn't be looking to replace the Rythmik. Adding a second Rythmik would be interesting but is unnecessary in my 19' x 24' x 9' room.

[audioferret]

I built my sub using the Rythmik DirectServo kit in a sealed 2.0cu.ft. box with 1.5" MDF walls (box in box), full shelf braces supporting all panels, etc. It weighs 93lbs (42kg) so I won't be moving it anytime soon.

1.  On the Box-In-box design, did you build the interior box completely first before adding the second layer?  or, did you work them both at once?  How did you work the cutouts through the layers?

2.  For your shelf braces, did you orient on all three axis?  How did you lay them out?

3.  Any advice for a new builder?  I have built speakers, just not a sub.  What would you do differently if you did it again?

-AF

[Christof]

I built my sub using the Rythmik DirectServo kit in a sealed 2.0cu.ft. box with 1.5" MDF walls (box in box), full shelf braces supporting all panels, etc. It weighs 93lbs (42kg) so I won't be moving it anytime soon.

1.  On the Box-In-box design, did you build the interior box completely first before adding the second layer?  or, did you work them both at once?  How did you work the cutouts through the layers?

2.  For your shelf braces, did you orient on all three axis?  How did you lay them out?

3.  Any advice for a new builder?  I have built speakers, just not a sub.  What would you do differently if you did it again?

-AF

DSK,
What material did you choose to isolate the layers of your CLD sub cabinets?  I'd like to find a lossy layer that will bind both layer together which would allow me to press two full sheets of mdf together with the lossy layer between them in a vacuum bag and then break the sandwiched sheets down with a table saw.

[drake]

After doing extensive research I think the Rythmik servo sub is OVERATED Marketing Hype.
Looks like it has the speed and the roll off benefits with the the extension of the Linkwitz Transform that boasts the bottom
end. But you can do that with any sub!

If you want to see technology in action check out the DSP controlled Axiom subs. Now that is technology!

Matt

[DSK]

After doing extensive research I think the Rythmik servo sub is OVERATED Marketing Hype.

Wow! Must save a lot of time being able to generate such STRONG opinions without even listening to it.

I'm not saying it is the best sub in the world, cost no object. But, after extensive auditioning, I can say that it equals or surpasses all subs I've heard up to around $4k. In my room, it measures flat to 16hz at the listening position (unsmoothed data), is very quick and articulate and blends seamlessly with my main speakers.

[ctviggen]

When you say "flat" what do you mean?  I have ETF data of my room, and my room's response is nowhere near "flat" even with 6 "bass" traps and 5 additional traps.  Do mean that there is significant output at frequencies between 16-X Hertz or do you really mean that the output has no room-related frequency anomalies?  If so, does this bass driver also use DSP techniques? 

[audioferret]

After doing extensive research I think the Rythmik servo sub is OVERATED Marketing Hype. Matt

1.  What extensive research have you done?  Please explain your comparison methods.

2.  Can you build a better sub for less than about $500.00?

3.  Can you build an axiom sub?  

Please Advise.

[drake]

Sounds like a came off a Little strong. SORRY
By reading the Rythmik audio website it would seem that they use technology that know one has ever heard of but servo controlled subs have been
around for many, many years as has Linkwitz Transform boast circuits!

I am not saying that the Rythmik subs don't sound good "I have never heard one" but that there are other good designs out there and some for less money.
Adire Audio subs
Dayton Subs
GR Research Sub
Even TC Sounds Subs - they have nice subs on sale every now and again. 
just to name a few..........

Then you have the IB subs!!

Sorry if I came off to strong.  If you ask me DSP controlled subs are the future.

Matt

[DSK]

When you say "flat" what do you mean?  I have ETF data of my room, and my room's response is nowhere near "flat" even with 6 "bass" traps and 5 additional traps.  Do mean that there is significant output at frequencies between 16-X Hertz or do you really mean that the output has no room-related frequency anomalies?  If so, does this bass driver also use DSP techniques? 

Hi Bob,
ETF showed that response at the listening position, with my previous speakers, was within +/-6db from 16Hz-160Hz. A recent shoulder reconstruction has prevented me from dragging the ETF PC downstairs to measure response with my new speakers yet, but just using an RS meter (with correction chart) and test tones shows the response to be within +3.5/-2.5db (raw data, unsmoothed) from 16Hz-160Hz. Yes, I realise that peaks/dips are possible at frequencies between the test tones, but given the lack of them when using ETF in this room previously, I doubt it. Also, our hearing is supposedly akin to 3rd octave smoothing so any very narrow peaks/dips would likely be inaudible anyway.

I do have bass traps and wall panels etc, but I have always suspected that the lack of bass problems in this room is due to its size and the fact that one corner (behind listener) is completely open to a long hallway and to an open staircase (ie. it is a large super-effective bass trap). One wall is predominantly floor to ceiling windows (covered by thick curtains) and probably acts as a bass trap as well.

[DSK]

I built my sub using the Rythmik DirectServo kit in a sealed 2.0cu.ft. box with 1.5" MDF walls (box in box), full shelf braces supporting all panels, etc. It weighs 93lbs (42kg) so I won't be moving it anytime soon.

1.  On the Box-In-box design, did you build the interior box completely first before adding the second layer?  or, did you work them both at once?  How did you work the cutouts through the layers?

2.  For your shelf braces, did you orient on all three axis?  How did you lay them out?

3.  Any advice for a new builder?  I have built speakers, just not a sub.  What would you do differently if you did it again?

-AF

I built the first box, then added the second around it. Yes, shelf braces on all axis.... full-width full-height main shelf brace at approx half-depth between baffle and back panel, another from baffle to main shelf brace (scalloped to allow for driver), a third from main brace to back panel (scalloped to allow for plate amp). I used a router for driver and brace cutouts and rounded over the edges of the brace cutouts and inside edge of driver cutout for smoother airflow ....again, just in case it makes a difference.

Some people argue that a bax this thick does not require additional bracing, but I have always preferred to over-engineer things ...just in case.
I can't think of anything I would do differently next time.

[audioferret]

Thanks DSK,

  I am getting ready to order this kit.  I have researched many different kits and I think this provides the most flexibility and performance for the price.  I don't think that the Rythmik site is in any way deceptive - In fact I think he provides good information about the technology and It sounds quite promising.

  Have you considered using an EQ like AV123's RDES?  I am using it with my current 150W 10" sub and the results are incredible.  There was a really noticeable improvement in Bass quality.  With the ability to quickly bypass your settings, the difference is easy to demonstrate.

  Does anyone have a better kit to recommend for less than $500?

[DSK]

Thanks DSK,

  I am getting ready to order this kit.  I have researched many different kits and I think this provides the most flexibility and performance for the price.  I don't think that the Rythmik site is in any way deceptive - In fact I think he provides good information about the technology and It sounds quite promising.

  Have you considered using an EQ like AV123's RDES?  I am using it with my current 150W 10" sub and the results are incredible.  There was a really noticeable improvement in Bass quality.  With the ability to quickly bypass your settings, the difference is easy to demonstrate.

  Does anyone have a better kit to recommend for less than $500?

If I wasn't so lucky with the response in my room I would consider EQ. However, in this room I am lucky enough to get flat response without it and thus to avoid adding extra components/cables etc.

[drake]

achieve lower extension and flatter response in a small enclosure - from the Rythmik website

How in the world would a servo sub help achieve lower extension and flatter response in a small enclosure?

The only way I could possibly imagine it would be through the use of the Linkwitz Transform to boost the bottom end and then the servo to keep the woofer in check. How does this help the flatter response??

I can buy this but how would this be better than using a high quality driver in ported box or PR box with a low F3 point?

Being that Rythmik combo needs a 2.1 cubic foot box. This is not a smaller enclosure!! There are many subs that work with PR in the same sized box??

I must really be missing something here.

And how is the Rythmic patented? High Gain Servo™ Technology Patent by Velodyne in 1984???

Matt

[DSK]

achieve lower extension and flatter response in a small enclosure - from the Rythmik website

How in the world would a servo sub help achieve lower extension and flatter response in a small enclosure?

The only way I could possibly imagine it would be through the use of the Linkwitz Transform to boost the bottom end and then the servo to keep the woofer in check. How does this help the flatter response??

I can buy this but how would this be better than using a high quality driver in ported box or PR box with a low F3 point?

Being that Rythmik combo needs a 2.1 cubic foot box. This is not a smaller enclosure!! There are many subs that work with PR in the same sized box??

I must really be missing something here.

And how is the Rythmic patented? High Gain Servo™ Technology Patent by Velodyne in 1984???

Matt

Hi Matt, if you genuinely want to understand how the Rythmik DirectServo setup works I suggest you talk/e-mail with Brian Ding at Rythmik. He can answer all your questions and you can then decide for yourself whether you think it is credible or not.

From memory, it requires a 1.6-2 cu.ft box (the 2 cu.ft. box provides greater sensitivity). There is a 3-position toggle on the plate amp to select extension (14/20/28hz) and the lower the chosen extension, the lower the maximum SPL's possible.

[audioferret]

How in the world would a servo sub help achieve lower extension and flatter response in a small enclosure?... How does this help the flatter response??....how would this be better than using a high quality driver in ported box or PR box with a low F3 point?

Have you read the Rythmik Audio site's explanations?

http://www.rythmikaudio.com/servo_tech.htm

The explanation appears very thorough and I can't find any fault in it.  He even provides explanations of the differences between DSP technology, linkwitz-transform, and servo.  What don't you understand?

Also, have you seen Mr. Linkwitz's website?  He provides a very thorough explanation of his technology, including why he uses a sealed, rather than ported subwoofer in his designs.

http://www.linkwitzlab.com/filters.htm#9

Being that Rythmik combo needs a 2.1 cubic foot box. This is not a smaller enclosure!! There are many subs that work with PR in the same sized box??

I don't see any subs that reach 10 Hz extension in that size box.  Which are you referring to?

And how is the Rythmic patented? High Gain Servo™ Technology Patent by Velodyne in 1984???

I have not seen a patent number posted by Brian, but he claims that he filed nine years ago.  The fact that he has not been sued by Velodyne indicates strongly that their two technoligies are different and non-competitive.


Matt

[drake]

You guys crack me up!!  aa

What sub will go down to 10hz in a 2 cubic foot box you ask? When using an LT there are MANY that will do it. With the current breed of super woofers exceeding 2.5 inches of travel the need for a servo controlled woofer becomes questionable at best.

Check out the audio control epicenter! How low do you want to go??

Matt

[audioferret]

With the current breed of super woofers exceeding 2.5 inches of travel the need for a servo controlled woofer becomes questionable at best.

Which one would you recommend?  Which subwoofers have you built?  What worked best for you?

Check out the audio control epicenter! How low do you want to go??

I'm confused.  You've just recommended a near $300.00 digital equalization system designed for Car Audio.  I am asking for a subwoofer.  Do you have any recommendations?

[drake]

I posted the epi because you asked if I knew of a sub that would go low. If you use a LT, an epi or an EQ like the DEQ2496 going low becomes a real possibility with many different drivers. It gives you more options to play with.

There are a lot of good woofers on the market. The subs from TC Sounds are awesome
as are the Dayton RS series, the Aura NS, the Adire subs, the GR sub.

My point was that you have a lot of options not just one or two because the servo makes all other woofers archaic.  In fact I feel it is the other way around.

As you know there are so many variables in audio and the woofer is only one part of the equation.

Matt

[audioferret]

You are not being clear, have you built a subwoofer or not? 

The GR Research subwoofer is at best -1 dB at 20Hz (nothing to sneeze at, I know).  The Aura NS is a 700.00 Driver!  The TC sounds drivers seem more reasonable, but start at $200 for a twelve inch driver (isn't the rythmik a TC-Sounds sourced driver? It has a similar price, too).  I am not very impressed with the reviews I have seen of the Adire subs when placed in a sealed configuration (which I will be using)  I have found sealed to be the sound I prefer with my monitors and I want to match my speakers with my sub.

Also, doesn't the use of a LT circuit with out an adequate amplifier introduce distortion as the amp and cabinet are pushed beyond their design limitations?  If I just throw in a large eq boost, how is that making the bass better without distortion?  I am not looking for more bass, I am looking for better bass...

I guess I will just have to build it and see.