Critical Q Sub Rythmik Audio Servo Sub

[Andrewbee]

Has anyone here built / heard the Critical Q Sub?
Same question for the Rythmik Audio Servo Subs.
I am between a pair of these and a pair of Rythmik Audio Servo Subs.

Not much posted about either, the usual technical dissection but ....

Andrew

[Mobster]

I've built DirectServo. Nice sub. Really nice Made it for music but use also with movies. Wrote something about it some time ago:
Rythmik Audio
directservo sub

No problems. Tight and accurate with good extension. Some might describe it as being a bit too 'dry'.

[Andrewbee]

Thanks Mobster,
I called Brian Ding who is Rythmik Audio and spoke with him for a little while. Seems like a nice enough guy, told him what I was after and asked for opinions / suggestions. I am actually leaning towards the Servo Subs. I plan on building a pair, one each in an OB with a Visaton B200 as the fullrange driver.

Andrew

[Mobster]

Brians service was first rate! I was also thinkig dual subs some time ago. But after some consideration decided against it - at least for now Maby some day I'll have an urge to build to two enclosures - speaker stands - for my small 2-way Dynaudios...

Currently my X-over is at 40hz and that one sub integrates with my mains quite nicely. After my next purchase I'll have some flexibility and will be able to keep X-over with music at 40hz PLUS set it with movies to 80hz.

[Andrewbee]

Those small 2 way Dynaudio's must go down pretty low if you cross over at 40hz. I am thinking of doing the crossover somewhere around 80 hz (24db) for my application.
I am strictly music, no movies for my application. I am envisioning OB's like the Visaton no box or diy systems Quasar only with the sealed sub for the bottom instead of ob bass.

Andrew

[morbo]

I built the rythmik servo kit, in a ~2 cu ft sealed box. If music is your only concern, this sub sounds better than anything I've heard to this point on music, and damn good at HT as well. I can't see any advantages for the 'critical q' sub over the servo, its just a sealed box with q=.5. The talk of equalling 'servo performance' in the documentation is unfounded, IMHO, and the various damping and extension settings on the servosub make it much more flexible to boot.

I keep it set at 14hz, high damping (q=.5) for music and 'light' movies. For action flicks I switch to low or medium damping and 20hz or 28hz extension to avoid bottoming (its still a single 12" driver!). I have crossed it at 50hz, 80hz, and 120 hz, and the sound gets better as I go up (in part because my satellites use 4.5" woofers). At 120hz the sub is more easily localized, so currently I'm crossing at 80hz but I will soon be running a stereo pair as speaker stands, and then I will go with 120hz - my satellites sound much better relieved of the low bass duty, and the servosub handles the 60-120hz range as well or better than they do anyway.

In short, if these are you 2 options, I see no advantage for the 'critical q' for movies or music. If movies were your main concern, you could build a more powerful sub for the same money (though the rythmik is no slouch in this department), but for music I don't beleive you could better it near its cost.

[Andrewbee]

Thanks guys,

I called Brian again this afternoon and I will be ordering them (servo subs) next week. I may be in the U.S next week so shipping will be cheaper if I get them there and carry back with me on the ironbird, otherwise its the P.O. I guess, those things are heavy!
I was reading his site some more earlier today, makes some interesting reading to me, explaining different approaches and the choices he made and why.

Andrew

[tkc]

morbo,

Have you measured the frequency response of your servo sub?

[morbo]

tkc, I have, but only to get the best integration with the satellites, I wasnt paying attention to how low it was going, just the behaviour through the crossover region. I'll try to get some more measurements done sometime soon.

It should be noted though that through the use of the extension and damping settings on the plate amp, you sort of tailor your own frequency response. This comes in very handy IMO. At my 'normal' setting, (14hz, high damping), it subjectively goes quite a bit deeper than my Adire Rava, but also bottoms sooner. If I set it to 28hz, med damping, it behaves almost identically to my Rava in response and excursion.

Again, this is not a monster output sub (though keeping up with a MkIV shiva is pretty damn good output for a 12" driver!), it is all about finesse and articulation, and in that area it handily outshines the Rava, which is no slouch in that department at all.

[Mobster]

Those Dynaudios are normal 2-ways with usable bass to 40hz region (in room). That 40hz X-over is used to filter out bass below tuning frequency. With this kind of adjustements speakers work almost as 'large' speakers and subwoofer extends bass to the 15-20hz area. The audible difference between 'large' setting and 40hz setting is extremely minimal (without subwoofer). As a result of this speaker cone movement and distortion is reduced when trying to output low bass signals. I know this is a bit unorthodox but it works great with music.