I know someone here has tried this. OB + BR.

[gurley123]

I have 4 Pioneer Bofu's sitting around and just waiting for some projects. I was poking through the internet and came across the idea of pairing an open baffle with a ported box using identical drivers.

Here's what I was thinking for my Bofu's. A large OB approx 2' wide x 4' tall with a 3 cu. ft. ported box attached to the rear with a second driver firing up. See the pic if my description confuses you as much as did me when I wrote it.

Who here has he done it? What are the draw backs? Expense of the second driver? (I already have two pair so that's taken care of.) Will the output of the two be matched well enough? If it really works then why haven't I seen more of these?

I'm interested in hearing what the more experienced members have to say.

[Godzilla]

I think they look like neat boxes!

[gurley123]

Thanks 'Zilla. I might just take the plunge on these.

I forgot to mention that both drivers are to be wired in parallel with no passive components between. A helper tweeter may be used with a simple cap but that's it.

[tinitus]

Interesting

You could be cross omni driver for a 1.5way to compensate for dipole rolloff and BSC

Another thing is that driver Qts=0.5 pionts more in the direction of a closed design, rather than BR

To maintain your general design with omni bass, maybe make a cut below the OB baffle, so that OB baffle is positioned in the middle of the omni driver, so that it works more like real omni

[gurley123]

Just going by WinISD (for whatever that is worth) puts a sealed bofu at a F3 of approx 60hz and a F10 of 32hz. A ported box of 3 cu. ft. tuned to 35hz has an F3 of 32hz and a F10 of 26hz. I know extension isn't everything but the ported curve looks better to me and I've always liked the sound of ported boxes over sealed for the music I listen too. I believe Zilla has had the Bofu in both boxes so maybe he could comment on this.

Moving the baffle back to where it straddles the boxed woofer is an interesting idea. Would there be any weirdness having the two drivers firing into the listing area at 90 degrees out of phase with each other? I don't know that much about how these things behave really.

As you guessed the goal was to have the merits of the "Open Baffle Sound" coupled with real bass output without resorting to bi-amping or eq'ing. I already have the Pio's sitting around so I might as well give it a shot.

[tinitus]

Originally posted by gurley123

Would there be any weirdness having the two drivers firing into the listing area at 90 degrees out of phase with each other?

Good point I didnt see in the hurry

The omni driver can only be in phase with either front or back of OB driver, which could be an issue

[mr ed]

I am using something vaguely similar ie ob + br

I have Saba 8"mid and 3" tweeter on open baffle with an 18" bass driver in a ported box.

It took a little while to arrive at this combo, as at first I trying ob for the bass in a u frame. I got frustrated and bought some ports and slapped a back on it and was shocked.It really sounds pretty damned good at this point, so I have been just enjoying it.

Ed

[2litre]

Gurley123

Maybe it's dependant on room size, but I have a pair of B20's in 1.94cu ft sealed boxes and I don't feel the need for a sub woofer with them. I don't know if I'm a bass head or not but I know I like confident extension into the high 30's low 40's and these are giving me that. My projected Fb was 59Hz and IINM my projected F3 was 57Hz.

B20's, sealed, wide vs narrow baffle?

Another thing I'd like to point out is that I'm in no rush to add tweeters to them. I have some PE Neo's for 'em. Unfortunately I didn't listen to them OB prior to doing this sealed thing so I can't comment on their sound in that regard, but I bet they will sound better than the sum of the parts would suggest.

As a point of reference I own a pair of Hawthorne SI's matched up with a pair of Augies.

R/

Jim

[Fast1one]

This reminded me of another thread not too long ago, which is very similar. Refer to this thread: new idea? to eliminate need for BSC

If you go with that enclosure type, I am not sure how it would sound with a bass reflex enclosure. That thread is to eliminate the need for BSC, since when the OB driver moves outward, the BSC woofer also moves outward, thereby making the net displacement essentially zero in the rear. If you want to avoid something like this, I would just mount the BR speaker in the front. You can also invert the phase of one of the woofers, or just mount it inverted with the magnet sticking out.

Also, I would definitely recommend rolling off the BR driver somewhere in the upper midbass or lower midrange. There will be some cancellation due to the phase shift if you dont add a highpass to the OB speaker, but it won't be as bad as you think in the upper midbass

[jamikl]

This seems to be a thread to ask this question in. Could a passive radiator in an appropriate box be used to absorb at least some of the rear radiation of an open baffle low frequency speaker. Maybe I am too tired to think properly. It couldn't be that simple in concept.
jamikl