[Danny Richie]

I have been working with something a little different. I must admit the results are not what I expected. The results are beyond what I could have imagined.

I took my dual SW-12-16FR's in the W frame and mounted a P Audio, high sensitivity coaxial driver right above it. It is a BM12-CXA.

See info on the driver here: http://www.gr-research.com/pdf/BM-12CXA.pdf



This thing doesn't sound like the typical professional class driver. It is smooth, detailed, and very easy to listen to. Even the compression style tweeter is not harsh, not fatiguing, and has really good resolution. Dynamics are in a completely different league than anything else. It even rivals or maybe even exceeds the LS series line sources in the dynamics department.

The full open baffle application worked out really well for this driver. It sounds more electrostatic than anything else.

Oh yea, and it is flat to 20Hz with unbelievable control and accuracy due to the servo control of the woofers.

I tried three different types of networks (listening hard and long to each one) on it including an elliptical network (really steep slopes), but the one that really shined was a very low order design (first order actually). The problem with most first order networks (at least a limitation) is the vertical lobbing problem and cancellation that can occur above the crossover point due to the shallow slopes. With a coaxial design this is no issue as the drivers are always in the same alignment. 

I would have never guessed a first order slope with a 1kHz crossover point would work with these drivers, but it works great. The 1kHz crossover point seems to be no problem for the tweeter either. It has a really low Fs and the response falls like a rock below 1kHz.

I also added a rear ambient tweeter, then wound up crossing it low enough to reach the woofer. That worked out really well too. Now it is full on open baffle and full range.

With 97db sensitivity it will be really easy to drive with those top notch single digit, single ended amps.

How is this? Not bad for a first order crossover on a big driver.



How about this impedance?



This speaker is doing a bunch of things better than any other speaker I have ever heard.

I may just offer this as a fully assembled product from GR Research.

I am going to try the lower woofers in an H frame and add some side panels to support it and give it some shape. I drew up a few plans already. What do you guys think?

http://www.gr-research.com/pdf/p%20audio%201.pdf

Here is a wire frame one so you can see the structure beneath. You can see the structure for the rear firing tweeter too.

http://www.gr-research.com/pdf/p%20audio%202.pdf

Eargasm Eric is going to be cutting me out some nice enclosures in a few weeks.

Stay tuned on this one.

[opnly bafld]

Awesome Danny! 

Lin

[Hank]

How 'bout that!  Interesting.  Is this the one that wasn't ready in time for RMAF?
Regarding the drawing, it looks good.  I think I'd shave off that point at the rear sides - it might be chipped easily and looks like a knee hazard
I assume the rear-firing tweet adds "air" to the presentation?

[S Clark]

This is a different and exciting direction for GR-Research.  I am curious, why the rear firing tweeter?  What problems does it solve? What are the pitfalls? 
I can't wait to hear it.  The wife and I will be just down the road from you in Archer City tomorrow.  Are you going to be around in the afternoon?

Scott

[HT cOz]

I think it looks great!

[TRADERXFAN]

Very cool.

What kind of ballpark costs?

[Danny Richie]

Is this the one that wasn't ready in time for RMAF?

No, I have something else along these lines that I was going to debut. If I would have just had more time... It is going to be really good as well, but different than this.

I think I'd shave off that point at the rear sides

Eric, already mentioned that we'd need to do that as well.

I assume the rear-firing tweet adds "air" to the presentation?

Yes it does.

I am curious, why the rear firing tweeter?  What problems does it solve? What are the pitfalls? 

No real problems just an added sense of realism. Let's just say that I notice some of the same things that this guy noticed. Scroll down to the pic.

http://www.linkwitzlab.com/Wood%20Artistry%20LL-home.htm

The wife and I will be just down the road from you in Archer City tomorrow.  Are you going to be around in the afternoon?

I believe I will. Call me.

What kind of ballpark costs?

Well, parts cost for the drivers, servo amps, and crossover hits the $1,800 to $1,900 range pretty quick. Then add in some fancy veneered and all CNC cut cabinets and it does add up. There is going to be some assemble involved too. But considering everything else out there it could still be a real bargain. We'll just have to see how it all shakes out. 

[gitarretyp]

Really nice design. Did you try removing the back cup of the compression driver rather than adding a rear tweeter? Obviously this will change the loading on the CD, but my radian coaxes actually work rather well this way; i just preferred the sound without the rear tweeter.

I have a few technical questions concerning the coax, if you don't mind sharing. The technical specs don't list the CD's diaphragm material, do you have any idea what it is? Do you have horizontal polar responses or off-axis measurements with and/or without your crossover?

[Danny Richie]

Did you try removing the back cup of the compression driver rather than adding a rear tweeter?

Nope.

i just preferred the sound without the rear tweeter.

I can make this one work either way.

The technical specs don't list the CD's diaphragm material, do you have any idea what it is?

I have no idea. I really didn't look to much into it. I really wasn't expecting much more than high sensitivity and good dynamics. I was really caught a bit off guard by the performance and how good it really sounded.

Do you have horizontal polar responses or off-axis measurements with and/or without your crossover?

I measured it with the crossover on it. It was exceptionally smooth and had less drop off across the top end than I thought. It acted just like a tweeter in a wave guide.

[HAL]

The driver specs for the compression driver say that the diaphram is made from Titanium.

[sts9fan]

I would say the drawing looks way to much like the Orions but I guess it is pretty much a passive Orion with different drivers. 

[Danny Richie]

I would say the drawing looks way to much like the Orions but I guess it is pretty much a passive Orion with different drivers. 

Considering the fixed elements involved, the challenge was to NOT make it look like an Orion, which is a little bit tough considering how the drivers have to be arranged in the design.

Not having to use 6 or 8 channels or 6 or 8 separate mono-blocks but a single stereo amp or single pair of mono-blocks is a real plus.

The high sensitivity means less expensive but very good sounding single ended tube amps can be used as well. 

[ttan98]

Danny,

How do you match the high sensitivity BM-12CXA(100dB) with the dual SW-12-16FR's(84.5dB each, parallel 90dB) which are of lower sensitivity?

[Danny Richie]

How do you match the high sensitivity BM-12CXA(100dB) with the dual SW-12-16FR's(84.5dB each, parallel 90dB) which are of lower sensitivity?

That is pretty easy. The SW-12-16FR's are hooked up to the direct servo amp.

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

You just turn up the gain until the output levels match. 

Same goes with the phase control. I just turn the knob until the phase lines up.

I can even adjust for a peak or dip in the room response. 

The flexibility built into the amp is awesome.

[emac]

Danny, are these the speakers that you hinted at in a previous pic of the W frame OB servos?  Because I've been wondering for a little while what you had cooking up in that pic.  And while they don't look like much, they could be terrific. 

And I'm all for either fully assembled or limited assembly being available as options on these speakers.  I stink pretty badly at woodwork. 

[Danny Richie]

Danny, are these the speakers that you hinted at in a previous pic of the W frame OB servos?

No, that was something different and still coming (Super 7 model).

[Bill Baker]

Wow Danny, that speaker must really sing with Gary's big monos driving it.

 Any news on the Super 7?

[emac]

Any news on the Super 7?

Seconded!

[dyohn]

I've used P-audio drivers a few times and found that their quality varies *greatly* from one to another.  Their low price is excellent, but in this case you seem to get what you pay for.  Indeed, I've ordered a set of 12" coax speakers and mounted them both the same way only to find that one sounds acceptable while the other drives you out of the room.  I like the thought, however, and the design concept looks great.  But I just wouldn't recommend use those Thai drivers.  YRMV, of course. 

[konut]

Would it be too difficult to put all the voice coils in the same plane?