Going Backless

[SlunkBoy]

My question technically pertains to a multi-way system, but it seems that most of the open baffle discussion takes place in the Full Range forum. Please feel free to relocate the post, if necessary.

I recently purchased a small piece of furniture at a resale shop that I plan to repurpose as a mono console system. It began life as some sort of shelving unit with sliding doors, but has been stripped to the frame. It is now essentially a shelf-less bookcase with a 3/8" wooden back panel. It is 12" deep and the front opening is roughly 28" square.

My plan is to flush mount a cloth covered plywood baffle containing a 12" coaxial driver and a 15" woofer. The drivers were salvaged from two different Magnavox consoles and are of similar vintage and construction. The coaxial will be run full range with its original tube amplifier while I will be driving the woofer with an electronic crossover and a solid state amplifier.

My questions are with regard to the treatment of the back panel on the donor bookcase. Does a "leaky" closed box have any advantages over an open baffle, or is it the worst of both worlds?

Additionally, whether I go backless or not, I will be "upholstering" the baffle for cosmetic purposes. I plan to build an internal frame upon which to mount the baffle, but I worry the fabric wrapping around the back will prevent proper coupling to the rest of the box. Am I overthinking this?

Thanks in advance for any advice,
Nick

[Nelson Pass]

I would try it with and without the back and see what works
for you.

[SlunkBoy]

Thanks for your reply, Nelson. I like your pragmatic approach. I was just trying to wrap my head around the concept of a "leaky" enclosure. I suppose it's analagous to having a large baffle with a bunch of slits in it.

-Nick

[Nelson Pass]

Yes, an open baffle is just extra leaky.

[thansaffel]

I am in the process of building a 48" tall MLTL for my Eminence Beta LTAs. Before I cut the port, braced or stuffed the box, I wanted to hear them, so I put a cut-to-fit panel of OC703 fiberglass acoustic insulation (2" thick) on the backs. It is very snug, with just enough give for the Cat5 cable to squeeze in.

It is a not very leaky box. They sound remarkably good, with authoritative bass that's not very boomy despite no bracing. I'm not recommending this as a valid enclosure "design," but if you like the pragmatic approach this is a step worth exploring.

I will finish the MLTLs WinISD told me to make (with the help of Scottmoose, GM and others here) but I am now not in such a rush (bad).

Than

[pjanda1]

Originally Posted by thansaffel

I will finish the MLTLs WinISD told me to make (with the help of Scottmoose, GM and others here) but I am now not in such a rush (bad).

Than

Thats always the danger of testing something out. I've sworn I'll never again setup a pair of unfinished speakers. I bet I break that rule before the end of this week!

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
great sounding, affordable, US-made fullrange loudspeaker drivers

[badman]

Originally Posted by pjanda1

Thats always the danger of testing something out. I've sworn I'll never again setup a pair of unfinished speakers. I bet I break that rule before the end of this week!

Then there's the flipside- putting a finish on a pair of speakers just to realize that you need to make some structural changes (or that they're simply not very good and you should have not wasted $200 on bubinga)

[pjanda1]

Absolutely. I was thinking of editing my post to differentiate between times when one puts them in the living room out of a combination of excitement and laziness, and those times when one needs a proof of concept. I'm certainly guilty of blind optimism too. It is awfully aggravating to spend an hour cleaning crap of a thrift store component before plugging it in to discover it is irrevocably busted.

Its also worth noting that much of the time, simply trying something takes much less time and worry then debating it online. I'm generally in the "try-it-and-see" camp, like Nelson's encouragement to Nick.

The next raw ply in my living room will be a proof of concept. I'll try not to let them get comfortable. Though my wife doesn't mind unfinished plywood. . .

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[thansaffel]

My motivation level just got a massive bump from the realization that Lowe's will cut raw pieces from a sheet of MDF (much cheaper than ply so better for testing enclosure dimensions) and then I can rip them to size at home. This is common knowledge but I had kind of forgotten.

I have the BetaLTA MLTL half done, and an MLTL for the FE168 Sigma ready to put together in the barn. Not having to crosscut and rip a full sheet makes it just that much closer to finished from the start. Also the big panel saw does a much better job than I usually do with a skillsaw and clamped fence for the crosscuts.

I find that removing just one step from a project can provide that bump to getting you toward completion.

So pjanda1, you gonna try the OC703 "back"? I was really surprised.

[pjanda1]

I can't leave the back of these guys, it's got crucial parts attached to it. Maybe a side . . . First I've got to find some OC703.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers