My open baffle dipole with Beyma TPL-150

[cuibono]

You might try using MJK's mathcad worksheets - they take a lot of the guess work out of things. MathCad Computer Models : Upgraded Versions For instance, with H-frames, a wider frame is more efficient than a deeper frame. I think you should have no problem reaching your goals with a little simulation beforehand.

I might add that I use baffles in the bass region - my goal is to have each driver working below its baffle peak - and in the bass, this can mean a good sized baffle. Otherwise, you find what you did at 30Hz.

[StigErik]

Yes, that's "that crazy W-baffle with oodles of 15" drivers" I was thinking of. Very cool, very inspiring. A truckload of drivers!

[mige0]

Originally Posted by StigErik

Here's the design ideas ..

Use single point mount at the ceiling and give it a side ways push - would make for a hypnotic Leslie effect - both optically and sound wise


Looking forward to the things to come - this thread is great joy!

Michael

[StigErik]

Right!!

(A funny thing is that I just recently was involved in the design of a Leslie replica loudspeaker. Not a true rotary speaker like the Leslie though, but the whole concept sounded a lot like a Leslie 112 cabinet.)

[Rudolf]

Originally Posted by StigErik

Here's the design ideas I'm thinking of right now.
Four 18" in H-baffle

I VERY much question this approach.
Below the lowest room mode room pressurisation will be the only means to transport sound to your ear. Those dipoles will lead to nothing IMHO.
Another thought: Is it really a good decision to thin out room modes as much as possible? The remaining ones will stand out all the more. If you really are prepared to got to extremes, I believe that Geddes has a better point with his distributed sub setup.

[cport]

Originally Posted by StigErik

Here's the design ideas I'm thinking of right now.
Four 18" in H-baffle
The rest hung from the ceiling, or a very tall frame.

Fantastic! You have replicated a design that I have held in my "mind's eye" for over two years. Love it!

You might want to check out this site:

10mm Stainless Display Rods

Each 10mm rod can support up to 440lbs -- I would attach the rods to the floor and ceiling, or secure to the floor (decoupled) using a 250 lbs pull neodymium magnet -- to damping resonances.

-- Charles (a Linkwitz Orion devotee)
Resonance Frequency

[skorpion]

What a disaster ! Cuibono is quite right when he directs you to MJK's worksheet. I had early in the thread a simulation that was based on a deeper U-frame than you probably built, and that simu pointed to massive EQ to reach high in low bass. So when you dumped the baffle altogether I was really surprised.

There are however good hints in what you have been doing here. Yours and others efforts points to that more investigation into 'optimal' baffle size is necessary. So far I don't think that 'No Baffle' is a proven answer.

I was also surprised that you when HP-ing the Excel unit so high as 350 Hz and steep enough (24 dB/octave ?) even without a baffle should have so big problems with EQ and that class unit. I can't really see the reason for this.

Before giving way to megalomania, I think the Beyma should be given a chance in an H-frame or as IB. In an H-frame with inner measures 22 x 22 x 22 inches including a resonable baffle thickness, the unit should produce 100 dB SPL at 25 Hz with about 7 mm cone movement with some 6 dB/octave EQ-ing from say 80-90 Hz downwards.

/Erling

[mige0]

Originally Posted by Rudolf

I VERY much question this approach.
Below the lowest room mode room pressurisation will be the only means to transport sound to your ear. Those dipoles will lead to nothing IMHO.
Another thought: Is it really a good decision to thin out room modes as much as possible? The remaining ones will stand out all the more. If you really are prepared to got to extremes, I believe that Geddes has a better point with his distributed sub setup.

Yeah, John has provided "in depth" theory and measurements on his page

roomgain
roomgain2A
Dipole_modesA


but on the other hand the measurements on Monte Kay's page seem trustworthy to me too.
Kind of brute force approach

Theatre woofer

Pay attention to the exceptional good distribution for all seats as well !

Michael

[Rudolf]

Originally Posted by mige0

but on the other hand the measurements on Monte Kay's page seem trustworthy to me too.
Kind of brute force approach

Michael,
brute force for sure.
I see that Monte Kay does not get rid of the longitudinal 20 and 40 Hz modes. And at low frequencies those W-frame towers next to the wall don't work as real dipoles any longer IMHO. The back wave has a 1,5 m wide opening into the room, which is 1/7 of the wavelength of 40 Hz. I would consider this as a really big mass of trapped air behind the W-frames.

What Markus has achieved with the multisubs looks more impressive to me.

Rudolf

[catapult]

Originally Posted by Rudolf

I VERY much question this approach.
Below the lowest room mode room pressurisation will be the only means to transport sound to your ear. Those dipoles will lead to nothing IMHO.

John's studies show that's clearly not true. You don't get any 'room gain' -- the 0 mode -- with a dipole but you still get plenty of direct sound at low frequencies.

That said, with 8 drivers, I like the idea of a double bass array (DBA) for dipole-like bass. Arrays on the front and rear walls at the 1/4, 3/4 points between surfaces. The rear array is inverted, slightly lower in level, and delayed by the time of flight from front to rear. The rear array acts like an active bass trap or an open rear wall.

Double Bass Array (DBA) - The modern bass concept! - AVS Forum