18" CAB Design Problem

[B.Flat]

Hi.
I have an elderly (nay, VERY elderly) CERWIN VEGA V35 cab. With my Stingray it has always come up with the sound I like (I only use the 18" woofer, not the HF horn or piezos). The cab is now too big for me to manage easily and I have moved to 4 X 10 Deltalite 2510 + 2 X 8 LA8-CNMB which is OK and manageable.
However the old CVega has a quality of its own. Though the original cabinet is a folded horn design,
I remember the same driver ( in a CV vented cab) being used by a lot of bass players who liked deep fundamental bass.
Instead of throwing the driver away I would like to put it in a vented cab, but Thiele-Small parameters are impossible to find for this driver.
Can anyone suggest how I could go about designing a cab (not neccessarily ported, sealed would do)
which would allow me to use it again without endangering the driver & hopefully getting somewhere near its potential performance.
On the very off-chance that someone out there DOES have the parameters for this driver, I do have the Winsd design prog. Or maybe some old duffer like me has the CV ported bass cab & could send me some details and dimensions.

I will be grateful for any help offered.

Brian Flat


Rock n'roll Mama, On A Saturday Night

[Phil Starr]

Don't worry too much, it's very likely that you will end up building a cab that is smaller than that needed to get the very best out of this speaker. Building a small cab is going to have two effects, it will raise the lower cutoff for the speaker and may create a bass 'hump' in output around the 100Hz mark. On the plus side too small a cab improves power handling.

Before we had T/S we just used to tune the cab to the speakers resonant frequency. You can find this if you have a signal generator (they have these on-line) and a multimeter as the impedance of the speaker rises to a maximum at resonance. Alternatively you can just tune the cab to 40-50Hz and it will probably work, albeit at less than optimum.

If you can get the data or find an original cab then all well and good, if not try finding a cab as near as possible in size to the one you remember copy the dimensions and tune it to 40Hz. WinISD will cough up the port dimensions for this. I wouldn't advise this for a new driver but you don't have a lot to lose. Be careful about how much power you put through it and use a bass filter like the thumpinator if you have one and the speaker should be fine.

[B.Flat]

[b][quote name='Phil Starr' timestamp='1402519516' post='2474442']
Don't worry too much, it's very likely that you will end up building a cab that is smaller than that needed to get the very best out of this speaker. Building a small cab is going to have two effects, it will raise the lower cutoff for the speaker and may create a bass 'hump' in output around the 100Hz mark. On the plus side too small a cab improves power handling.

Before we had T/S we just used to tune the cab to the speakers resonant frequency. You can find this if you have a signal generator (they have these on-line) and a multimeter as the impedance of the speaker rises to a maximum at resonance. Alternatively you can just tune the cab to 40-50Hz and it will probably work, albeit at less than optimum.

If you can get the data or find an original cab then all well and good, if not try finding a cab as near as possible in size to the one you remember copy the dimensions and tune it to 40Hz. WinISD will cough up the port dimensions for this. I wouldn't advise this for a new driver but you don't have a lot to lose. Be careful about how much power you put through it and use a bass filter like the thumpinator if you have one and the speaker should be fine.
[/quote][/b]

[b]Thanks for that Phil, I will take your advice and see what happens.[/b]

[SubsonicSimpleton]

Is your cab is like the one pictured here

http://www.wikizic.org/Cerwin-Vega-V-35/gallery-2.htm

Bit hard to tell from a photo, but that looks to me like the cab is a bass reflex enclosure with horn coupling for the woofer rather than a folded horn arrangement - have you confirmed the cabs internal construction details by removing the drivers and access panels so you can get a good look inside?

If I'm right, then you should have the correct port dimensions and cab volume right there, and providing you can work out the capacity of the awkward shaped voids around the horn it should shrink down to a nice neat ported box.

[B.Flat]

[quote name='SubsonicSimpleton' timestamp='1402591440' post='2475135']
Is your cab is like the one pictured here

[url="http://www.wikizic.org/Cerwin-Vega-V-35/gallery-2.htm"]http://www.wikizic.o...5/gallery-2.htm[/url]

Bit hard to tell from a photo, but that looks to me like the cab is a bass reflex enclosure with horn coupling for the woofer rather than a folded horn arrangement - have you confirmed the cabs internal construction details by removing the drivers and access panels so you can get a good look inside?

If I'm right, then you should have the correct port dimensions and cab volume right there, and providing you can work out the capacity of the awkward shaped voids around the horn it should shrink down to a nice neat ported box.
[/quote]

Hi SubSonSimp,
yes that is the one (with the red horn) and you are absolutely right about the configuration, my mistake to call it a folded horn.
I had started to do exactly what you suggest but took the chance that someone might have access to the T.S. parameters or have a CV bass cab..
I shall now have corage in someone elses convictions (yours) and carry on with what I should have done in the first place !

By the way is the photo you linked to your cab? Probably not but though I live in sunny France I notice you are in sunny Yorkshire and I originally had two V35's and sold the other in Yorkshire !

Rock n'Roll Mamma On A Saturday Night

[SubsonicSimpleton]

I don't own one of the cabs, so I was just making an educated guess - once you have measured and calculated it might be a good idea to revisit the thread with the numbers and discuss further with the guys who really know about cab design.

Before you commit to a build it might be worth considering the loss in efficiency without the horn loading and whether you will still have enough SPL, but that is going to depend a lot on your individual band circumstances. I'm sure one of the more knowledgeable speaker builders would be able to make a pretty good guess about the decrease in efficiency if you also measured up the dimensions of the woofer horn.