A speaker physics question.

[VolvoHeretic]

Last Saturday, I was all fired up and with the help of a little rum, I dreamt up this, but then Old Guy burst my bubble and I gave up, but since this topic won't die, here is what I came up with. I have no idea how I would draw this in AutoCAD, I can only draw arcs and ellipises and I don't have a clue how to integrate them together. I could free hand them close enough, but that wouldn't be perfect. I like sketch D's sideview with sketch C's frontview. This is assuming plywood sideboards and built-up rubber conveyer belting curved horn sections. I think it should be stiff enough. (Ignore the pencil scratches above the D and below the speaker.)

[cradeldorf]

Wow, I'm glad I quit drinking. How would you keep the rubber belt from expanding every time a note came out? and the horn has to be a certain length. you could cut and stack plywood but that would be a shitload of plywood. and without having the correctly calculated horn it would be all for naught.

[VolvoHeretic]

I would cut out two pieces of .75" plywood on either side of the .75" built-up belting, and fasten that to another 3/4" plywood side board so that you wind up with a total thickness of 1.5" with a .75" wide by .75" deap dado. I am praying that 3/4" curved and glued built-up belting is rigid enough for a horn mouth, I mean, how rigid is the .375" bass horn curve in my A7?. I guess the top, back, and bottom of the speaker and dowels inside the loops will have to hold everything together? Maybe it will just have that Dean Martin sloppy drunk sound to it. I never said I thought this out that far.

[417 - Alnico]

Blizzard of oz was My first Ozzy concert. Draw in Illustrator / modify in Photoshop / post here.

Cool!
I saw Randy at the La Crosse Center on January 19, 1982.
He ripped everyone's head off.
417's Forever.

[cradeldorf]

I would cut out two pieces of .75" plywood on either side of the .75" built-up belting, and fasten that to another 3/4" plywood side board so that you wind up with a total thickness of 1.5" with a .75" wide by .75" deap dado. I am praying that 3/4" curved and glued built-up belting is rigid enough for a horn mouth, I mean, how rigid is the .375" bass horn curve in my A7?. I guess the top, back, and bottom of the speaker and dowels inside the loops will have to hold everything together? Maybe it will just have that Dean Martin sloppy drunk sound to it. I never said I thought this out that far.

Sounds like a nightmare to try to piece together unless you have a trick up your sleeve to weave the belt through. and where are you going to get all the belt from??? it wouldn't be cheap either.

[cradeldorf]

Refresh my memory, why is it when I use the vented box volume calculator (DIY Audio) it says I need a box that is 1.88 cu Ft? with a port that is 6 inches in dia. and about 9 inches long? I don't even think I could build a box with that small of a volume that would be capable of fitting a 604 plus a vent that size in it???

[GM]

...........here is what I came up with.

FWIW, all those swoopy curves do is let too much of the driver's mids/HF make their way to the mouth where they comb filter with the driver's direct output, 'muddying up' some portion of the mids [and depending on the driver, HF] BW, so such layouts are best left to wide BW folded FLHs. As a general rule, the more initial bends you can fit into the desired net bulk, the better to filter out the shorter WLs. Olson's 2,224,919 patent is the first I'm aware of to address this issue.

GM

[GM]

Refresh my memory..........

Of course you can! You add the volume lost to the driver?s and vent?s intrusion and add it to whatever the desired net Vb is. Until the cab?s desired net Vb is < the air ?trapped? between the rear of the diaphragm and frame [think sealed back mids construction], the driver will always fit the cab, though of course it may have to be [internally] contoured to do it as it gets near the minimum.

Regardless, for such ?troublesome? layouts this is what inversely tapered TLs are for since a vented cab is acoustically just a ?stepped? TL.

The lumped variables vented box formula is: Vb = 20*Vas*Qts^3.3. Since Qts dominates by far, a low Qt even with a high Vas = small cab, so for a frame of reference, add enough series resistance to double Qts and all else equal, you?ll get a ~9.85x larger cab! This is why old cab designs were so big and drivers had such powerful motors, they had to account for the amp?s high output impedance impact on the speaker system?s total Q [sysQ].

Consequently, if we want to power them with a very low output impedance, some form of EQ is required to ?fill up? these large cabs. That, or weaken the motors by design to a higher Qts, which of course is what all the mainstream manufacturers did since it improved the ?bottom line? initially, ergo essential to help maintain market share.

GM

[VolvoHeretic]

FWIW, all those swoopy curves do is let too much of the driver's mids/HF make their way to the mouth where they comb filter with the driver's direct output, 'muddying up' some portion of the mids [and depending on the driver, HF] BW, so such layouts are best left to wide BW folded FLHs. As a general rule, the more initial bends you can fit into the desired net bulk, the better to filter out the shorter WLs. Olson's 2,224,919 patent is the first I'm aware of to address this issue.

GM

Thanks, GM. So, a Tuba’s inspiration is out.

[Old Guy]

Conveyer belt stuff is like 1/4" thick, could be dadoed in? a worn one that had been taken out of service would suffice...

All this assumes a proper design.