[rick57]

Hi

has anyone in this circle tried the Rythmik GR-Research combination?

Servo amps
http://www.gr-research.com/index.asp?PageAction=VIEWPROD&ProdID=142

Drivers (16 ohm version):
http://www.gr-research.com/index.asp?PageAction=VIEWPROD&ProdID=141

I say "sub"woofers as they can deliver flat output up to c 200 Hz

Cheers

[panomaniac]

There is quite a lot about them in the GR circle

http://www.audiocircle.com/index.php?board=16.0

[rick57]

Thanks pano

That might have been where I learnt of therm, about the time they came out.
With servo etc, they seem like they are the best, I was just seeing if in of us dedicated OBers had used them.

I was condsidering the high Vd Mach 5's, but have just ordered a set of these from GR. It'll be a few months before I get to set them up, with the P.Audio coaxes above them.

rick

[WerTicus]

I put this in the HT circle since its for a HT setup, but you'll probably find it interesting,   12 woofer open baffle stereo subs

http://www.audiocircle.com/index.php?topic=53699.msg552891;topicseen#new

Its my current project.

[kyrill]

hi
I am busy with a true OB setup ( takes much more time than i anticipated)
2 servo GR 16 ohms parallel,   the Focal 6WM mid and Peerless HDS  810921 tweeter ( not yet assembled) in a 16,5" width baffle
no filters but the digital DEQX filters
i use laminated wood   1 inch thick and MDF ( 6 inches deep and 7 inches for the other panel)) for the U-frame
the "design" is a, ehhh  a "crystalization" from reading this very OB Circle, thank you guys ( no galls i suppose,,)

[richidoo]

As I understand, the 16ohm drivers are specifically intended for open baffle use. High impedance allows 3 in parallel to overcome baffle losses down to very low freqs, high Qts, paper cones, active amp, it's a OB builder's dream driver. I'm gonna build some too for my Feastrex full range.

[panomaniac]

Nice choice of drivers Kyrill!   Those should sound very good when you get them up and running.

FWIW, I passed a store yesterday that had a pair of the big yellow Jamo OBs on display.  Need to go back and listen to them.
Your rig should be as good or better.

[dweekie]

Very nice build Kyrill.  One of these days, there needs to be a OB bass showdown.  My main experience has been with the Hawthorne Augies, and they so much better than any box sub that I could hardly believe it, especially considering the cost.  Based on that experience, I fiind it hard to take the financial risk to try something like the smaller GR research servos, which require a larger inital purchase to get the 2 driver/amp servo system going.  The AE IB15 looks interesting to compare as well......

[rick57]

I found it hard to believe, but people have compared the earlier Rythmik servos in boxes, to the quality of OB bass. 

Others have said (apart from OB) the Velodyne servo bass is outstanding.

Rythmik have been doing servos for iirc 4- 5 years, so I believe servos with OB specific drivers could take OB bass to a new level  . .

[dewar]

Second that, would very much like to see a GR Servo OB setup compared to some Augies (which I have, driven by a big power amp and XO'd by a DEQ2496). The extra 10hz extension of the servo setup might let me forgo my box sub which I still use for movies.

[Danny Richie]

Thanks for the discussion guys. I think many will find this to be a major advancement in low bass reproduction. I really don't see anything matching this performance level at any price point.

kyrill, that's a really interesting new project. A tip or two for you though...

Those woofers are going to push a lot of air each way, and the way you have them mounted will allow them to rock back and forth fairly easily. It will counter act some of its output. You might want to consider a W frame or H frame to help stabilize it. Floor spikes will help too. This will clean up and tighten up the bass response quite a bit.

You might also consider keeping the baffle width and size to a minimum around the upper drivers. This will minimize surface reflections and edge diffraction and improve imaging considerably.

[kyrill]

hi Danny

thx for yr tips

It is a prototype to begin with and i picked up yr concern earlier about "fixing" the drivers in the sense the more the baffle cannot move the better the bass will be. The U frame is heavy and glued to the bottom and to the baffle
the baffle is also strengthened  by two side beams 2"x2"  screwed and glued to the bottom
The bottom plate will be made more heavy with a second 1 inch bottom plate screwed to it.
I will make the construction as rigid as possible. I was indeed thinking about tiny spikes to freeze the bottom plate to the floor. As an extra weight the servo amps will be screwed to the bottom plate as well
The baffle for the mid range is still "big" as i want the mid driver to go as close as possible to 100 hz without OB cancellation
if i make the dimensions smaller i have to compensate the midrange for its OB loss and its Xmas is only 2.1 mm. (o.08 inch) It is not actually an OB driver..So i dont want to use a boost for the 100hz. I can play a bit with the servo's to go to 200hz so mid range takes over from that frequency
The tweeter will be helped by a second tweeter firing backwards and i will put a big felt pad from Jimdgoulding an AC member around the tweeter to dampen diffraction effects

I avoid the W and H fame as i find them so ugly but in the end my ears will decide