[ebag4]

Hey Guys,
 I would like to publicly acknowledge and thank Danny for his work on this crossover as well as this nice compliment on the new Model 700 AMT drivers.  Danny did an outstanding job stitching our two drivers together.  We have several new and exciting projects in the works and very much look forward to working with Danny.

Thanks,
Darrel 

Welcome to AC Darrel!

Best,
Ed

[Architect7]

Whoa, did we lose a bunch of posts in this thread?

edit, nevermind, looks like a new thread was created.

[HAL]

Danny moved them here:

http://www.audiocircle.com/index.php?topic=125799.msg1327009#new

[bdp24]

For anyone thinking about integrating GR OB W or H-Frame subs with speakers as-of-yet-undetermined, there is a criminally overlooked loudspeaker that couldn't be better for the application: The Eminent Technology LFT-8b. It is a Planar Magnetic panel design inspired by Magneplanars, but improved upon with 1- a push-pull magnetic structure---magnets on both sides of the Mylar drivers (midrange and tweeter) for lower distortion, and 2- etched on conductors rather than wires for lower mass and more even motor distribution. It is a hybrid loudspeaker with, get this.....an 8" sealed woofer. The one criticism of the speaker is it's limited low-frequency output. The answer is obvious---replace the ET 8" in the sealed enclosure with an 8" Servo driver and the Rythmik Servo amp. Or, for those wanting OB subs, employing multiple 8" or 12" OB Servo drivers in a W or H-Frame in place of the ET 8". And get this---the LFT-8b crosses over from the midrange panels to the woofer at 180Hz---the x/o frequency of the Super-V! GR OB woofers easily play up to 180Hz (as was proven in the Super-V), and are well behaved enough out-of-band to be used with the 1st-order x/o of the LFT-8. The result? A world-class Magnetic Planar/Servo Woofer full-range loudspeaker at a bargain price. This is just too great to keep to myself! Now, if only there were someone making reasonably-priced flat pack H-Frames.....

[Jonathon Janusz]

I had a pair of those for a while and had the same thoughts regarding upgrading the woofer section.  My condensed thoughts on the speakers as a whole:

The designer/builder was very helpful in answering questions - even on my second hand speaker purchase.

There is some big potential in upgrading the stock crossovers in these (Sean listening maybe?).

These are very power hungry.  If you've only heard them with a lower powered amp, a big amp really makes them a whole new speaker in my opinion - and much to the better for it.

I don't remember/think they would fit on the woofer cabinets as built, but the front baffle width was just about big enough to get a 12" driver in there, if the box was rebuilt to accommodate the volume if one were so inclined.  I'm not sure a single 8" would be enough to get enough drive in that range to completely solve the output problem; quality would improve, but if you're looking for displacement, I think a sealed 12" if you were going that way would maybe be better.

The upper baffles are easily able to separate from the woofer cabinet, for modding purposes.  Also (at least the ones I had) were set up for biamping split between the woofer and the mid/tweeter section, so just running the uppers was also easy to experiment with (not sure of the impedance with just that section playing, though?).

My one real gripe was that the vertical off axis response of the tweeter was really not so great.  The tweeter panel is only about half the height of the mid panel.  If you listen seated at tweeter height, things are great; If you stand up, the top end falls off fast.  In my "perfect world", there would be a version of this speaker with a full-height tweeter.

Regardless of nits to pick, I have to agree that with these you get a lot of speaker for not a lot of money. 

[bdp24]

I agree with you 100% Jonathon. I can't help but wish that there were two tweeters---one above the other, running side-by-side the midrange panels. As you said, replacing the ET 8" with a GR 8" Servo would be better, but not better enough (for me, anyway). I mentioned that for those who want a simpler set-up. Since the speaker is an OB panel, the ultimate woofers for it IMO are two or three 12" (or four or six 8") Servo woofers in an H-Frame (sorry Ric, I'm with Danny on this!) placed side by side with the panels. The jumper cable for the ET 8" can just be disconnected (and shorted, to "freeze" the cone), and the LFT becomes a two way non-hybrid. The midrange panel's bandpass is 180Hz-10K, with symmetrical 1st order cross-overs on both ends. That's right campers, a single panel driver covering 180 to 10,000, cross-over free. Wow. I'm astounded so few people know about the speaker. The LFT-8b is an easy 8 ohm load; the panels themselves are an even easier 12 ohm load. Great for tube amps, except that the speaker's sensitivity is really, REALLY low. Like 83dB. 200 watts minimum for a medium sized, carpeted room. But if you don't mind transistors, watts are cheap. So are the speakers. And for their level of performance, the Servo subs, OB or sealed, we already know are the best buy subwoofer in the world! All of this applies to other panel speakers as well. All the Maggie and ESL owners in the world should have OB Servo subs!

[Hank]

All the Maggie and ESL owners in the world should have OB Servo subs!

  That's why I plan to replace my 15" sonosub with an _-frame 12" servo sub to accompany my "new" Acoustat Model 3's 

[bdp24]

  That's why I plan to replace my 15" sonosub with an _-frame 12" servo sub to accompany my "new" Acoustat Model 3's 

A sub Hank, or a pair? The OB sub can be used up to about 300Hz, but if you run them that high (to relieve the Acoustats of as much excursion as possible) you'll need one for each speaker. You probably already know that!

[staylor]

Here is my recent build similar to your plan:
RAAL 140-15D
AE Dipole 12
2 SW-12-16FR
Behringer DCX2496
IcePower 1000ASP on the mid
Lepai  LP-2020A+ on tweets <-- yes, $1000 in tweeters being driven by $20 in amp 



Previous speakers were Tannoy D700.  I like this new speaker better.  Though, it wasn't a slam dunk preference until I stuffed the back of the Dipole 12s with open cell foam.  Plan is to go to the new miniDSP IcePower plate amps with DSP built in.  That will replace my kludge of mid, tweet amps and behringer.
This original build was many years in the making as I collected parts, made and remade plans, so I'm pretty happy to finally have it "done".  Other versions may happen or not, time will tell.   A few potential iterations:  Would like to try adding 3 or 4" midrange between Dipole12 and 140-15D to better match polar response.  Would like to try large format CD crossing to Dipole12 around 700Hz.  Would like to put SW-12-16FRs in opposed configuration to better protect against little hands, feet, and toys.  Would like to try Neo10s in place of Dipole 12.  Would like to try Neo 3 as dipole in place of 140-15D.  Would like to try something coaxial for the top end.  Could probably go on and on.

Though I am an extremely happy owner of a Rythmik FV15HP in my home theater, I had no idea GR Research made an OB servo sub until today.  As you can imagine, I am absolutely enthralled with the idea of servo OB subs.  I am planning a new OB build and have everything but subs and processor/preamp.  It will be:

RAAL 140-15D dipole ribbons
Acoustic Elegance Dipole6 mids (x2 per side)
Hypex 6-channel custom built amp
2-3 SW-12-16FR per side
2x370 GR Research amps
Something like an RME Fireface 800 for preamp/DSP

My old OB setup used 6x AE OB15's, 3 per side with ~350watts each.  This setup was my first love for OB bass, absolutely intoxicating.  Now that I have heard the FV15HP, I want the best of both worlds; OB bass with servo accuracy.  In the meantime, please show me your OB GR Research sub builds so that I may be inspired (and a little jealous).  Thank you!

[mlundy57]

what do you mean by "stuffing the back of the Dipole 12s with open cell foam?

[staylor]

Cut trapezoids (mostly triangular with a small 4th side) from a 2" thick sheet of 20 ppi foam and stuff in between the basket spokes.  Not an idea I've seen anywhere else, just a rapid prototyping way to cut down the backwave.  I've got the speakers about 2 feet from the wall as is, but I think they need more and that isn't going to happen physically.  So, go sealed?  That would be somewhat counter to the whole point of this design.  Was going to do some kind of more traditional resistive enclosure, then hit on this idea and I'm happy with the result.
I would imagine that I've got cardioid-ish response, but without a complete null in back since I'm just attenuating but not fully blocking the rear of the driver (at least not more than is done by the magnet).  I was a little concerned that I might get a noticeable smearing from reflections between cone and foam but I don't notice any issue.  The foam surface is probably not much of a reflector (that could change with frequency, but at least in the midrange I sound to be okay).

what do you mean by "stuffing the back of the Dipole 12s with open cell foam?

[Hank]

You probably already know that!

Oh yeah.   I don't think I'll run 'em all the way to 300 Hz - these Acoustat's go a bit lower fairly effortlessly.  I'm thinking 200 Hz, but will experiment.

[bdp24]

Were the Super-V's crossed to the OB subs at 180Hz, or 280Hz?

[Danny Richie]

Were the Super-V's crossed to the OB subs at 180Hz, or 280Hz?

Around 180Hz.

And I say "around" because changing the output level and crossover point on the dial all has an effect on the actual crossing point.

[Architect7]

Here is my recent build similar to your plan:
RAAL 140-15D
AE Dipole 12
2 SW-12-16FR
Behringer DCX2496
IcePower 1000ASP on the mid
Lepai  LP-2020A+ on tweets <-- yes, $1000 in tweeters being driven by $20 in amp 



Previous speakers were Tannoy D700.  I like this new speaker better.  Though, it wasn't a slam dunk preference until I stuffed the back of the Dipole 12s with open cell foam.  Plan is to go to the new miniDSP IcePower plate amps with DSP built in.  That will replace my kludge of mid, tweet amps and behringer.
This original build was many years in the making as I collected parts, made and remade plans, so I'm pretty happy to finally have it "done".  Other versions may happen or not, time will tell.   A few potential iterations:  Would like to try adding 3 or 4" midrange between Dipole12 and 140-15D to better match polar response.  Would like to try large format CD crossing to Dipole12 around 700Hz.  Would like to put SW-12-16FRs in opposed configuration to better protect against little hands, feet, and toys.  Would like to try Neo10s in place of Dipole 12.  Would like to try Neo 3 as dipole in place of 140-15D.  Would like to try something coaxial for the top end.  Could probably go on and on.

Wow those look amazing and probably sound even better.  I will be selling my pair of 140-15D Dipoles at some point if you think you'd be interested.  No hurry to sell, probably a couple months from now?  Priorities have shifted and I'm buying a house instead of investing in my 2-channel setup.

I have heard from a couple people that the AE and Accuton mids are more accurate/detailed than the B&G Neos.  Not to throw a wrench in your plans or anything 

[Danny Richie]

I have heard from a couple people that the AE and Accuton mids are more accurate/detailed than the B&G Neos. 

No, not hardly. The Neo's have much less moving mass and a much faster spectral decay.

[Architect7]

Yeah I was definitely skeptical of the claims.  Will have to test for myself someday

[bladesmith]

Danny,
Ive read some issues with Neo 8/10's stacked vertically in OB designs.. Issues with frequency cancellations.

But, I see manufacturers doing it frequently.

Any testing done yet on this design..?

thanks..

[Danny Richie]

Danny,
Ive read some issues with Neo 8/10's stacked vertically in OB designs.. Issues with frequency cancellations.

But, I see manufacturers doing it frequently.

Any testing done yet on this design..?

thanks..

If not designed properly or crossed over properly then there can be some cancellation patterns.

Yes, I have gone through lots of testing with these driver and this design.

[bladesmith]

Danny,

At what point would you cut off or cross over the Neo8 (or Neo10) on the low end ?

thanks