Thanks Scott, you know, "pain & relief"......
Now sounds much easier, and I've found some sealing stripes (similar to those suggested by GM) used by plumbers that looks like blue tack.
Still have problem to find suitable plywood, long enough....uff! Around here only poplar plywood and mdf...
Ciao. Fab.
Now sounds much easier, and I've found some sealing stripes (similar to those suggested by GM) used by plumbers that looks like blue tack.
Still have problem to find suitable plywood, long enough....uff! Around here only poplar plywood and mdf...
Ciao. Fab.
Scottmoose, try here
Peter Benson Plywood
seems like lots of types including Baltic Birch (which by definition here in Canada is void-free). Not sure of British nomenclature for such things.
Peter Benson Plywood
seems like lots of types including Baltic Birch (which by definition here in Canada is void-free). Not sure of British nomenclature for such things.
Aha! Cheers for that -will have to contact them, especially as I'm regularly over in that area.
Just been doing some rooting around: the 3800 isn't as large as I remembered, so you can probably get away with reducing the VP cabinet a bit over the one I mentioned before -take the base as a 25cm square, and keep the length, driver position and vent height as-is (the reduction in width will reduce the vent by roughly the 'correct' amount). Wince.
Keeping the size in mind, Greg's Altec based BIB would therefore have a terminus area of about 250 in^2 which is getting more reasonable in CSA terms. Sorry for any confusion caused. The brain clearly wan;t working as well as it should have been!
Best
Scott
Just been doing some rooting around: the 3800 isn't as large as I remembered, so you can probably get away with reducing the VP cabinet a bit over the one I mentioned before -take the base as a 25cm square, and keep the length, driver position and vent height as-is (the reduction in width will reduce the vent by roughly the 'correct' amount). Wince.
Keeping the size in mind, Greg's Altec based BIB would therefore have a terminus area of about 250 in^2 which is getting more reasonable in CSA terms. Sorry for any confusion caused. The brain clearly wan;t working as well as it should have been!
Best
Scott
He! poplar plywood here is not a good quality, except for very thick one (more than 1").
Birch, both Russia or Finland are good but expensive and too short. (so unuseful)
Okumè at the moment looks very good, but a piece 122"x60"x1"thk costs 170 euros!
That's why I'm considering a sandwich, thinner okumè inside and a blockboard wood outside, but this has again poplar inside, light and soft, so maybe not so good....(even if Omega Spk's Lou Chochos said to line back and front outside baffles with a layer of poplar 'cause sounds better...boh!)
Some hard woods are cheaper than plywood, but talking with a lutist nearby, he did not recommend me hard wood (even spruce or tone maple) 'cause It would be very difficult to tune right the own natural wood resonance and musicality with cab dimensions.... A speaker, he says, is NOT a violin.....(HA!)
Next monday I'll go to see a carpentry and than decide...I'll let you know.
Ciao. Fab.
Birch, both Russia or Finland are good but expensive and too short. (so unuseful)
Okumè at the moment looks very good, but a piece 122"x60"x1"thk costs 170 euros!
That's why I'm considering a sandwich, thinner okumè inside and a blockboard wood outside, but this has again poplar inside, light and soft, so maybe not so good....(even if Omega Spk's Lou Chochos said to line back and front outside baffles with a layer of poplar 'cause sounds better...boh!)
Some hard woods are cheaper than plywood, but talking with a lutist nearby, he did not recommend me hard wood (even spruce or tone maple) 'cause It would be very difficult to tune right the own natural wood resonance and musicality with cab dimensions.... A speaker, he says, is NOT a violin.....(HA!)
Next monday I'll go to see a carpentry and than decide...I'll let you know.
Ciao. Fab.
Hey there!
Inside dimensions, eh?
I drew it in Autocad, and if I make the inside 2443.84mm the backplate
will be 2451.18mm
Now a sheet of MDF is 2440mm long, and to make the backplate
out of 2440 + a piece of 11.18mm.....
So if I make the back plate 2440mm, the inner dimension will be 2427.16mm tall.
Can't imagine a difference of 16.68mm (that's 0.68% of 2443.84) will matter?
Speakerbuilding isn't THAT scientific, is it ??
St will differ accordingly ? (1062.5mm from the top?)
And stuffing is just a matter of trial and error ?
More to come in about two weeks,
When I got a few days off, I'm gonna build it!!
Wooohooo
Scottmoose said:
Inside dimensions, eh?
I drew it in Autocad, and if I make the inside 2443.84mm the backplate
will be 2451.18mm
Now a sheet of MDF is 2440mm long, and to make the backplate
out of 2440 + a piece of 11.18mm.....
So if I make the back plate 2440mm, the inner dimension will be 2427.16mm tall.
Can't imagine a difference of 16.68mm (that's 0.68% of 2443.84) will matter?
Speakerbuilding isn't THAT scientific, is it ??
St will differ accordingly ? (1062.5mm from the top?)
And stuffing is just a matter of trial and error ?
More to come in about two weeks,
When I got a few days off, I'm gonna build it!!
Wooohooo
Please note the contents of my further post -it (probably) doesn't need to be quite as large as this. You can likely reduce the CS of the bottom to 25cm x 25cm.
To answer your question, 1.6cm won't make any difference, given the scale of the enclosure, and the fact that we're shooting blind anyway. Stuffing will also be a suck-it-and-see approach.
Remember -I do not vouch for this cabinet, other than pointing out it's unlikely to be much worse than anything else, given our lack of driver parameters, so please don't blame me if you don't like the results! Bet they'll look good though! The large one (36cm x 36cm base) apparantly worked with the 12in Philips 800 ohm drivers, and people liked it, so this reduced version (25cm x 25cm base) should (theoretically) work in a similar fashion with these smaller 8in units. Greg's Altec formula based BIB might be a slightly safer bet; but in both cases, stuffing will be a suck-it-and-see approach. Make sure you have plenty to hand! As we're shooting blind, and with no alignment to speak of, the fractional height reduction won't make any difference.
Regards
Scott
To answer your question, 1.6cm won't make any difference, given the scale of the enclosure, and the fact that we're shooting blind anyway. Stuffing will also be a suck-it-and-see approach.
Remember -I do not vouch for this cabinet, other than pointing out it's unlikely to be much worse than anything else, given our lack of driver parameters, so please don't blame me if you don't like the results!
Bet they'll look good though! The large one (36cm x 36cm base) apparantly worked with the 12in Philips 800 ohm drivers, and people liked it, so this reduced version (25cm x 25cm base) should (theoretically) work in a similar fashion with these smaller 8in units. Greg's Altec formula based BIB might be a slightly safer bet; but in both cases, stuffing will be a suck-it-and-see approach. Make sure you have plenty to hand! As we're shooting blind, and with no alignment to speak of, the fractional height reduction won't make any difference. Regards
Scott
Scottmoose said:
Greets!
Hmm, I calc'd ~265.14"^2 for 8*Sd, not exactly small, but a far cry from 700"^2. WRT a suitable cab other than OB for ultra high Q drivers, a max flat impedance Alpha TL will work well to damp it, but you need either fairly accurate specs or make it too long and shorten it as required to get the proper damping of the high Q peaking. MLTLs are better choice IMO since you can design it so that the driver will damp it when it's positioned at the pipe's 3rd harmonic, ergo both alignments will allow a more realistic Vb.
GM
Scottmoose said:
Greets!
You're welcome!
The nomogaphs are in Altec Alumni Alexis Badmaieff/Don Davis's "How To Build Speaker Enclosures". If they're on the 'net, I'm not aware of it, though Altec's basic BR nomographs are, but even the bug riddled WINISD or BoxPlot demo is a better tool than them since it will at least allow you to do ducted ports. If vintage BR alignments are your 'thing' though, these work fine: http://www.lansingheritage.org/images/altec/plans/1960's-lf-design/page03.jpg or a later, slightly different one here: http://www.lansingheritage.org/images/altec/plans/1968-enclosure/page04.jpg
GM
Scottmoose said:
Greets!
I assume you're referring to this alignment: http://www.bonavolta.ch/hobby/en/audio/tqwt.htm
GM
Aha. 12cubic foot enclosures. Just the ticket
My apologies Greg -I revised the CSA to a much closer ~250in^2 in a second post at the top of this page, along with a revised Voigt volume -my fault, I'd accidentally used a 12in driver Sd not an 8in. Not quite sure how I suceeded in doing that as it's a pretty big diference! Perhaps a nice big sealed or aperiodic box could do the trick too.
My apologies Greg -I revised the CSA to a much closer ~250in^2 in a second post at the top of this page, along with a revised Voigt volume -my fault, I'd accidentally used a 12in driver Sd not an 8in. Not quite sure how I suceeded in doing that as it's a pretty big diference! Perhaps a nice big sealed or aperiodic box could do the trick too.
FWIW, I've found a better picture of Herb's traditional style 8ft tall VPs, with vintage 12in diameter 800ohm Philips FR drivers. Here they appear to be sans wings. I gather they won the 'Most Absurd' prize at NYNoise 2002. See attached. This is my last offering on the subject however, as we really should bring the thread back to the BIB cabinet. My fault!
At the moment, I'm playing around with Martin King's software, trying to ascertain how much of an impact different flare-rates (i.e departing from the ideal conical expansion rate) will make to the BIB's response. Will let you know what results I get. Sadly, the ML TQWT sheet is of no use for this sort of modelling, so it has to be done in the BLH sheets and TL Sections, which takes longer, so it might be a few days before I have anything worth reporting.
Regards
Scott
At the moment, I'm playing around with Martin King's software, trying to ascertain how much of an impact different flare-rates (i.e departing from the ideal conical expansion rate) will make to the BIB's response. Will let you know what results I get. Sadly, the ML TQWT sheet is of no use for this sort of modelling, so it has to be done in the BLH sheets and TL Sections, which takes longer, so it might be a few days before I have anything worth reporting.
Regards
Scott
Attachments
I know the feeling... which probably also explains why I look back at several of my posts and wince at the array of spelling mistakes and typos. Not good. Plan A was to donate money to charity for every spelling mistake or typo I make from now on, but that's hardly a worthy incentive given the less mistakes I make, the less said charity would recieve.
Plan B will be put into operation once I decide what it will be... Probably to take more time and check everything before pressing the 'Submit Reply' button.
Not good. Plan A was to donate money to charity for every spelling mistake or typo I make from now on, but that's hardly a worthy incentive given the less mistakes I make, the less said charity would recieve. Plan B will be put into operation once I decide what it will be...
Probably to take more time and check everything before pressing the 'Submit Reply' button.
copperhead said:
Greets!
You're welcome!
I meant use low density fiberboard or particle board since it's more lossy than felt or similar while not attenuating the LF like fiberglass or polyfil insulation.
Yes, but obviously I don't know how much material to remove, so it would be a cut n' try situation. You could try a K-slot too.
GM
Greets!
You're welcome!
One facing a wall would be best, but whether it would be superior to scalloping I can't say, though in theory it would be. How's that for a definite maybe?
WRT what size/profile to make it, your guess is as good as mine other than to use the original as a guideline for experimentation if need be: http://home.planet.nl/~ulfman/ "A New Approach in Loudspeaker Enclosures In Audio Engineering, september 1952"
GM
You're welcome!
One facing a wall would be best, but whether it would be superior to scalloping I can't say, though in theory it would be. How's that for a definite maybe?
WRT what size/profile to make it, your guess is as good as mine other than to use the original as a guideline for experimentation if need be: http://home.planet.nl/~ulfman/ "A New Approach in Loudspeaker Enclosures In Audio Engineering, september 1952"
GM
GM, thanks again, for help and the link.
If I need to head down this path, I suppose I could try Fab's idea of temporarily sealing on the
back. If I go to far, only a piece of particle board wasted.
With regards to the extra round baffle the driver is mounted to.... is it better to just round over
the edges, or should the shape be more bowl like, approaching a sphere?
Is it possible to go to far by making it too thick?
Thanks, John.
If I need to head down this path, I suppose I could try Fab's idea of temporarily sealing on the
back. If I go to far, only a piece of particle board wasted.
With regards to the extra round baffle the driver is mounted to.... is it better to just round over
the edges, or should the shape be more bowl like, approaching a sphere?
Is it possible to go to far by making it too thick?
Thanks, John.