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15" bass box - with a difference ...

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slaz View Drop Down
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Joined: 27 November 2009
Location: London E2
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2021 at 1:46am
Well - had the idea for this for quite a while now ...

Needs a bit of pre-amble - but I'm guessing quite a few in here are not short of time to read/muse/laugh etc. in these lockdown times:-)

So - I'm 65 years old - bit of back trouble - and I live on the 3rd floor of a tenement block with no lift.
Heh. Thing is - I also live very close to Victoria Park (nice) - where I've been playing out for quite a while with various sizes of battery power speakers/setups.
So right now my "senior" battery setup consists of a single passive FBT Maxx 4 (4 ohm version  - which is rare-ish) powered with a  Bassface 4ch class D car amp. This works very nicely - the 12" FBT only gets about 150W or so (2ch of the amp running 4R bridge) - but gives a very good account of itself. Sounds very hi-fi - except of course for the fact that bottom octave is pretty much missing. Now in the context of playing outdoors from battery power - it actually sounds OK - most folks just take it and enjoy as is .... but not me of course.
Now the logistic involved with playing over the park is - got a bodged up trolley thang that carries the FBT + about 20Kg of 12V lead batteries. I can _just about_ get the whole shabang down the narrow stairs - 3 or 4 journeys on my tod  - but I do sometimes get help from a younger/fitter neighbour.

I've actually been offered (FOC) an oldish Tannoy 15" bass box of some sort - haven't seen it yet. Suspect it might be a bandpass box from the description. But of course its made from ply or MDF (might be from an install) - and I stand feck-all chance of safely getting that up/down the stairs. The driver might well be decent though ....

Aaaanyway .... here's the idea.

I happen to have a 8' x 4' sheet of this stuff (or very similar).

http://www.cxdinternational.com/boards/support-backing-board/aluminium-honeycomb-centered-panel-glass-fibre-bdhexg7195?returnurl=%2fboards%2fsupport-backing-board%2f

(sorry dunno why that doesn't seem to hyperlink so here's a pic)



Came from  a former flatmate who worked for a well-known museum - it got used as backing for displaying pictures/artworks. The piece I have has some very hard-to-remove gunk on it, not a problem methinks. So - well it should be obvious where I'm going with this.

If this could be successully cut into a 15" bass box it would feckin _awesome_ - absolutely the difference between having a bass box of sorts - and just not having one at all, as all the normal boxes are impossible for me re stairs/logistics.

So the idea I  have is :-

Just a conventional bass reflex box - as compact as possible. I'm not trying to play really low ... 45Hz with a bit still there at 40 would be fab. Also, I'm obviously not trying to flap trousers, the box ain't gonna get more than about 150-200W or so. I'm really just aiming for a "taste of bass". Nothing radical here then.

But the material _is_ a bit on the radical side. As per the web link, you can see the price :-)

I have in mind to make a five-sided box from the honeycomb stuff - and make a normal baffle - from 15mm ply I guess.
The problem with the honeycomb stuff (HC) is its just about imposible to get a clean cut with any kind of saw I think ... but a mate over the road had a go with a small test piece - to butt 2 bits together perpendicular style (butt-joint) - seemed to work OK - so I'm hoping a 15" box is possible/viable.

I've yet to work it out, but I think it should be possible get the weight down to around 14-15Kg using this HC stuff - I can definitely manage that on the stairs - the FBT 12" box is 13Kg. Might even be less if I can scrape up enough down the back of a sofa for a neo driver.

I'm currently to trying figure out - with the constraint of not making any cut-outs/holes in the HC:-

1) What to use for some kind of edging strip to cover the exposed edges of the HC.
2) How to achieve some kind of corner protection.
3) How to accomodate a removable plwood baffle.
4) How to achieve some kind of internal bracing.

I'd be very interested to hear from anyone who knows this HC stuff, has worked with it in any way, or has any informed opinions on how to construct. I figure on mounting the speakon panel on the front baffle - a bit strange I know.

Also interested in what folk think is a suitable driver for this. The P-Audio E15-300S looks like a candidate - small power handling, but plenty for this box. Nice price too from Blue Aran, but not especially light weight. Bear in mind I won't have fancy EQ or anything available (well I might consider getting one of those Thomann mini-DSP things. ).
Whats the simplest, smallest 15" reflex design I could use in this context ?

OK - ramble over - for now :-)

TIA.








REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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