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norman bates 16th November 2012 09:24 AM

betsy plus 15's idea..........

The quasar open baffle.

melon head got this response but I'm not sure how he crossed in the 15's using an10 with dual an15's (qts=.5, probably more). The an10 is listed qts=.286 but a german review had them at .411

The 300hz hump was said to be crossover issues, and the climbing response past 1khz is the an10's natural response.

The easiest woofer would be the inexpensive eminence alpha15, but some want a less floppy sound (requiring more eq due to lower qts).


fastbike1 16th November 2012 09:17 PM

FWIW, my AN10s give measured qts of .343, my BetsyK's give .479

fringy75 26th March 2013 01:05 AM

Now there is an idea for a new project. Norman, I have seen Berts BD Design website but details are lacking (or very hard to find) around how to construct something like this. Do you have any suggestions/thoughts? Thanks

norman bates 27th March 2013 10:49 AM


I'd use an active crossover, and probably a lot of boosting.

200hz crossover point (24db) is yuck.
So maybe 100hz, but need at least 6db of boost to get down there with a 18" wide baffle, maybe more.

So with the mini-dsp, it should be possible. But the 15's used in similar b200 plus alphas, usually have a 12db low pas filter at 40hz to counteract the roll-off.

See the visaton NoBox.
The VISATON NoBox BB Loudspeaker Kit Review By Dick Olsher

There is a youtube video, it has some thump with headphone listening, but missing midbass to my ears.
The room is way too live, speakers firing towards parallel walls = bad.


zimmer64 30th March 2013 09:02 PM

Hello Norman,

Coincidently, yesterday I put together a test setup similar to what you are suggesting. I tried another OB project with Betsy and the hinged baffles earlier this year, but was unimpressed with the bass department.

I am now trying another attempt with her. This time with helper woofers, a DSP acting as a crossover and equalizer and two stereo amps.

I have used the MDF from my previous OB project. Baffle size is 120 x 46 cm. The woofers are Eminence Alpha 15 A. The DSP is a 2x 4 miniDSP in a box. The Betsy's are driven by a LM3875 gainclone, the woofers by a Rowen Absolute Two.

As an initial setting I crossed over at 200 Hz with 12db Linkwitz Riley. The bass channels are boosted by +10db. I have also applied a high shelve filter of -3 db from 2 kHz.

An initial soundcheck in the garage was promising. I currently run them 24/7 to break them in. I will then measure and further equalize them as required.

Pictures (large size....) are in my blog: Open Baffle Project | Michael's Project Page

Biggest problem currently is WAF. My SO was not impressed with the looks of them...... (Quote: "They are not going into the living room!")...

I will post the final DSP settings once I am done.



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