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ozziozzi 6th July 2006 06:41 AM

Fullrange plus helper bass-suitable amps?
I am about to embark on an open-baffle loudspeaker project with various 70s & 80s vintage 4" to 6 1/2 inch (SEAS, Vifa, Philips, Fostex) augmented by a 12" bass driver per channel--which may end up in a sealed enclosure if bass too light. First experiment on sheet of ply or MDF, later panels 38mm thick solid wood baffle with side panels. I plan on bi-amping using an active XO (adjustable between 80-120 Hz) and two stereo amps. I have the choice of several amps for bass and mid/treble use and seek advice on best combination. Drivers seem reasonably efficient so power of amps should not be a great concern. I am mainly after very clear midrange and treble followed by usable bass down to ~ 35Hz--40Hz measured Fs of woofers I have. I have choice of v large magnet, stiff surround woofer or foam roll surround smaller magnet woofers both 12" nominally 20W. I would appreciate recommendations for which would be most suitable OB?
I have no objection to super-tweeter over 10kHz if necessary. Ruler-flat response is second to openness, clarity in midrange and "punch" or attack in midbass that I have found typical of single-driver enclosures.

Amp choices
Amp1 Luxman L-230 duobeta (15W Class A -> 63W Class AB)
Amp 2 Luxman L-30 (30?W class AB?)
Amp 3 Various chip amps ranging from 5 - 20W/channel.
Amp 4 Old New Zealand made ~10W valve/tube amp-OK sound
Amp 5 Old Pioneer valve/tube receiver ~15W/channel

I was thinking L-30 up to 120Hz , L-230 or tube amp over120Hz, mainly because of the VERY nice class A sound of L-230, but open to recommendations/arguements.


Nuuk 7th July 2006 07:39 PM

I run an open baffle with TL woofers, all powered from GC's. So that's my vote! ;) (all details on my web site)

Rudolf 7th July 2006 08:37 PM

What a pity to confine yourself to just one 12" bass driver per channel on OB. You surely will NOT be satisfied.
I strongly recommend to try two 12" drivers per side - one at the very bottom of the OB and the other above. I understand that you have at least two stiff surround woofers and two foam roll surround woofers. I would not hesitate to put one of each on every panel. You could avoid impedance problems and compensate for different efficiencies of the woofers by triamping (two amps after the active XO).

Give it a try before resorting to a sealed bass enclosure. ;)

ozziozzi 9th July 2006 08:24 AM

Fullrange plus helper bass-suitable amps?
thanks Nuuk and Rudolf for your suggestions.

When I said chip amps, I have a mixture of LM1875s, and older stereo chip amp modules inside integrated amps from various well-known brands. I like the fact that most of them are almost indestructible ;-D I have used them with v efficient PA type boxes at YMCA disco for 3-4hrs at 90% output without incident. Occasionally they shutdown, but not often. Of course I have added fan-cooling to some of them.

Re: stiff surround vs roll surround woofers. My small experiments have shown that the foam-roll surround woofers produce more bass and significantly more mid-range than the ones with stiffer surround and heavier cone even tho latter have huge magnet and larger diam VC. This driver (AKAI 70s vintage) came originally from a BR box so is probably better suited to that.

Rudolf ,you could be right about dissapointing bass from single woofer and need tri-amping. I note that Linkwitz etc use a lot of bass boost for their OB designs. I may have to resort to a second driver or heavy EQ. Do you think a 2.5 way setup might work with W-W/M-T going up the baffle?

I will experiment with large inductors (4-8 mH) in series with bottom woofers. Maybe put lower woofer in BR or TL enclosure? Upper woofer/midrange OB. I will mock up boxes when I have more time.


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