Am I totally wrong, or could this be a viable OB + active woofer? - diyAudio
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Old 24th April 2017, 10:02 PM   #1
diyAudio Member
Join Date: Feb 2016
Default Am I totally wrong, or could this be a viable OB + active woofer?

Hi forumites with A LOT more experience than me!

First things first - I'd just like to say that it's an absolute pleasure to follow the goings-on in this forum. A lot of very knowledgeable people, who aren't afraid to share. Love that!

Now to the actual issue at hand: I've got an idea for an OB + sealed/BR woofer-project that i can't seem to shake. I've got two Sonab OA5 Type 2 speakers ( the enclosures are tidy enough, but the woofers and tweeters were shot. These have been standing in my garage for nearly five years, and I've never really gotten around to them. But now's the time. Yay!

These are nice 60's omnidirectional speakers, with the grille on top (image in the link). Mine have a really deep veneer (jacaranda, I think) and would be a shame to waste. Not interested in restoring or upgrading them as I already have a pair in good nick. So...I thought I'd go down the OB route, a completely untrodden path for me.

My idea is as follows: Use the enclosures to house one eight inch woofer and a plate amp each and build an open baffle with a single broadband unit on top of that. The baffle would be somewhere in the 20x50 cm range (9x20 inches, approximately).

I've got an idea for a design which I think would look good - but question is, can something like this SOUND good? It's perhaps a small-ish baffle, but how much does that matter?

My preferences are tight bass, rather than earth-shattering home cinema-style. And I've had hours upon hours of music enjoyment on a friend's OB setup (TB W8-1808, dual 15-inch Eminence??? woofers), so on the outset I'm pretty set on the Tangband. (AND YES, I do realise that my boxes won't give me that kind of performance in the lower octaves.)

Would the 1808 work on this small a baffle, or should I look at smaller drivers (5-inch)?
Could that then be nicely integrated with an 8 inch woofer? What should I look for when choosing a woofer? Any suggestions (it's a 47 litre box)? Don't want it to sound like a small home cinema satelite with a cheapish subwoofer standing in the corner...

How low could the broadband driver go and how high should I aim to cut off the bass?

Am I looking at a MiniDSP-type of setup or would the plate amp-route suffice?

Realise that my levels of knowledge leave a lot to be desired here, but I'm eager to learn and would greatly appreciate any feedback!

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Old 25th April 2017, 12:07 AM   #2
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Join Date: Nov 2005
Location: New York
You can put a 10" subwoofer in the 47L cabinet and add the TB on OB for a great sounding speaker.
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Old 25th April 2017, 12:11 AM   #3
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scottjoplin's Avatar
Join Date: Dec 2015
Location: Penrhyndeudraeth
When I hear 10" subwoofer I fantasize about this Seas L26ROY D1001 SubWoofer
What came first, the music or the misery? Nick Hornby
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Old 26th April 2017, 09:16 AM   #4
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Location: South Australia
Sonab OA5's were designed for use against a wall if memory serves me correctly.Woofer to the wall & tweeters "facing" (loose term as there were 4 of em the listener) Why not try something like the Direct Acoustics Silent Speaker II. This is still being manufactured & uses the wall boundary location to extend the bass. Utilizing that same concept you could have these in 8 or even 10 inch sub duties in the corners to enhance the bass from your other Sonabs. IF space allows
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Old 26th April 2017, 10:03 PM   #5
diyAudio Member
Join Date: Feb 2016
A tempting suggestion that. The only thing holding me back is the fact that I've already tried it - or at least something similar with upgrading another pair of OA5's. Would like to try something new at this point...
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Old 26th April 2017, 10:09 PM   #6
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Join Date: Feb 2016
Nice! Only problem is the narrow baffle. Don't want to open up the nice sides of the speakers, so I'm looking at three options:
* Driver in the bottom, facing the floor
* Driver in the top baffle, facing the ceiling
* Driver "hidden" in an internal baffle. Not really sure how that would work though...

And the third one makes things too complicated for me...and that's the only way to fit a 10" subwoofer in there. So I'm looking at 8" drivers instead. But all recommendations I can find online for enclosures that size is 10".

But final volume might be a bit less, need to enforce the thinish walls and build a new bottom as well as adding some internal bracing. Perhaps around 35-40 litres.

I realize I need to get real on these plans and stop doing them in my head. Time to learn sketch-up or something it seems...
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Old 30th April 2017, 04:34 AM   #7
DieterK is offline DieterK  Germany
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Join Date: May 2014
Location: Wuppertal
Driver in the top-baffle and the fullrange on top of it seems to be a good starting point. When you look for 8" Woofers, had you taken a look at the Visaton W200S? In 30 liters sealed f3 round 50Hz and vented f3 round 40Hz with small group delay.
Best Regards
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