OB bass driver arrangement ??

[Andy G]

Has anyone seen a pair of OB bass drivers, 15", arranged thus ? (viewed from above)



Anyone have any idea of the bass patterning ?

The mid/top are envisaged as a 6" Beyma, and a Selenium compression driver on the MCM 6'" waveguide, and this could be positioned above the V-frame at the required position to achieve good time alignment.. maybe ??

I have the above + 4 x Etone 15" drivers which have a low Fs, but unfortunately also have a low qts. (they probably aren't all that suitable.... but that's what I have, so that's what getting used)

This is only at the rough idea stage, and may not even be viable, so any 'constructive' input is welcomed.

[CLS]

Instead of 90 degree and 15", mine is 120 degree and 18" :

Multiple Dipole Subs
(That was in my previous place ... )

The baffle itself looks like a little boat when lain down.

It looks OK, but actually the construction is not rigid enough due to the shallow front to rear shape. The moving forces of 2 18" woofers plus the air make the baffle vibrate quite obviously. Fortunately it's used as a standalone sub, so it doesn't 'pollute' mid to high frequencies...

If I made it again, I'd consider deeper angle and/or with some more front to rear bracing for better supports.

[D OB G]

I'm using something very much like that Andy.

135 degrees and two 15" (one mounted back to front and out of phase a la Linkwitz).

10 mm steel with heavy triangulated steel bracing bolted to a baseboard.

The steel is covered on each side with 12 mm of cork, and the drivers bolted through it.

As the bracing rests on the baseboard there is some vibration, very little.

As it is bolted down, only very heavy bass causes the slightest vibration.

David

[Andy G]

Originally Posted by D OB G

I'm using something very much like that Andy.

135 degrees and two 15" (one mounted back to front and out of phase a la Linkwitz).

10 mm steel with heavy triangulated steel bracing bolted to a baseboard.

The steel is covered on each side with 12 mm of cork, and the drivers bolted through it.

As the bracing rests on the baseboard there is some vibration, very little.

As it is bolted down, only very heavy bass causes the slightest vibration.

David

pics ??
.
..
please

[D OB G]

Please excuse the state of the environment (work space), but I think you'll get the idea.

There is a separate baffle for mid/tweeter to isolate any vibrations that might "sneak through"!

Crossover at 150 Hz (48 dB per octave- DEQX), down to 40 Hz, where two monopole subs, in parallel with OB, take me down to a measured 18 Hz at -0 dB (with DEQX EQ- for room as well. Measurements taken at a number of positions, averaged, and then EQ'd).

(Incidentally, if the DSP measurements are made VERY close to each driver- mid and tweeter, the polar response stands up to CD (I'm using a waveguide) over a very wide arc- much more so than measuring some distance back, say the listening position).

Anyway:Audiosyncrasy.jpg

openbaffle 001.jpg

openbaffle 002.jpg

(The PHY-HP mid has been changed to an 18sound 6ND430, hard up against the waveguide).

David

[D OB G]

P.S.

I help the DSP EQ by running the 15"ers in parallel through a 22 mH air-cored inductor. Insertion loss is only 2 ohms, and it doesn't hurt to raise the Qt.

This only works if the impedance peak is very high Q i.e. the impedance stays low for as low a freq as possible, and with a very low Fs, and the drivers have a high efficiency, with an adequate Xmax, all of which the EMI 1550 has (Fs of 23-25 Hz).