2 x15 Big Cab

[sturoc]

I just picked up cause I couldn't pass up the price $ 20,
a fuzzy covered empty 2 x 15 cab. It is big more like a PA style cab.
24" w x 24"deep x 48" high
2 round ports, one on each side between the drivers .
Construction is super solid 3/4 ply or birch.

I was thinking about using it as a bass cab but wonder how something of this size would be for bass guitar?

Don't worry, it won't be a gigging unit -it's just too big for that so it will sit in the studio!

[Nalte]

If it's designed as a P.A. cab, it may have too many booming lows and not enough cutting mids.

[sturoc]

That did cross my mind .
If there are any cab designers or members versed in speaker theory out there,
I would love to hear your thoughts.
Would there be any mods I could do to improve the Cab for this application.
Perhaps cutting it in half to make 2- 1 x15 cabs with different porting scheme?

[Mr Antt]

Originally Posted by sturoc

That did cross my mind .
If there are any cab designers or members versed in speaker theory out there,
I would love to hear your thoughts.
Would there be any mods I could do to improve the Cab for this application.
Perhaps cutting it in half to make 2- 1 x15 cabs with different porting scheme?

Cutting it in half makes sense to me. I'm hardly experienced so my input is probably invalid. But to me it sounds like a good option. That way, I'd imagine you could gig it. In theory just take one 1x15 cab.

Anthony.

[Muziekschuur]

Show us the inside. Can it be opened from the back?
You just need correct speakers for the box.

If you calculate it's liters you can devide by 2 and find what driver would be happy in that enclosure.

[Rick Blanc]

Originally Posted by sturoc

That did cross my mind .
If there are any cab designers or members versed in speaker theory out there,
I would love to hear your thoughts.
Would there be any mods I could do to improve the Cab for this application.
Perhaps cutting it in half to make 2- 1 x15 cabs with different porting scheme?

Paging GreenBoy and BillFitzmaurice

[sturoc]

Would not be that interested in cutting in half as it would not be a gigging cab, but if it improves the sound I would.

[sturoc]

The back panel seemed to be removable at one point, but looks like is now sealed as the drivers holes are setup for front mounting.
I have a full wood shop set up here though.

[jumbodbassman]

not technical but that looks fine to be a bass cab. if my math is right it is over 13. cubic. lookslike it was a subwoofer cab. maybe boomy, but should work if you fill it up with insulation. some more tech guys will chime in shortly ....

[BogeyBass]

A single 15 works well in 3 to 5 cubic feet.

once you go past 6 cubic feet your starting to drift into a EBS alignment. Extended bass shelf.

24 x 24 x 48 is about 16 cubic feet, so roughly 8 cubic per driver
So this is for sure a sub cabinet and your looking at very high excursion drivers.
you can load it up with lower cost eminence speakers and get really deep bass. but the speakers will fart out really quickly.

measure the diameter and length of the ports, so we can get a idea of what the cabinet is tuned to.

It would be hard to run it as a full range cabinet since high excursion drivers wont have much highend. But it would make a very good sub cabinet with a good investment towards high cost speakers. your looking at 300 to 400 a speaker to load that thing with something that works.

(edit) also what is the diameter of those speaker cutouts, this almost looks like a 2 x18 sub cabinet

[sturoc]

thanks for the great info...
Driver holes are for 15" spkrs
Ports are 5 1/4" diameter x 5 " long
Cab is all Birch , a + for sure.
So by reducing the cab volume I could get to the proper efficiency ratio for close to full range ?

Sounds like the blade is coming out then. I could theoretically chop off a few inches from the back side and redo a new rear panel, glue clamp it, screw it tight.
What would the porting be then ??
Or slice and dice to make 2 cabs, the porting for that would be ?

or I should ask is that info here in talkbass somewhere ?

[BogeyBass]

Its got 2 round ports in the middle

I dont see cutting it in half being useful at all.

If you want to build 2 single 1x15 cabinets it seems easier to just start from the beginning, and build and tune a cabinet around a specific driver instead.

If you want to mod the cabinet to work for a lower cost speaker
maybe enlarging the cutouts to fit a 18inch speaker instead.

their is a few 18's in the 200 dollar range that might work. Some calculations would have to be made. minus the bracing, the ports, the speaker, and the stuffing. the real world volume would be around 7 cubic feet per driver.

[sturoc]

So Bogey, how bout cutting off a certain amount from the back side reducing the depth to a usable volume ?
It would then be like an old Sunn 215 series cab.
Which is what I've been searching for months for.

[BogeyBass]

without spending to much time on this, the cabinet seems to be tuned around 29 to 31 hz.

I see 3 options.

1) leave cabinet and ports as is, enlarge cutouts to 18". load with a pair of Eminence Sigma Pro 18A-2. max power of 270/330 watts

2) leave cabinet as is, shorten ports to 3" length. load with Eminence legend CB158. max power of 120/160 watts

3) lower cabinet volume by reducing depth of cabinet to 17"
keep port length the same at 5". load with Legend CB158 max power of 200/250 watts

keep in mind if you shorten those ports and the large volume is to farty, then its going to be a challenge to add the length back.

[sturoc]

Funny you should link to Prts Exp as i was looking at the exact same 15" driver last nite.
Will think about these options and yet one more surfaces, flip the cab (sell).
Put $ towards a nice Sunn if I can find one.
Thanks for the guidance Bogey.

[will33]

Bogey has you on the right path. I'd chop the back down so you end up with an internal volume of about 8 cu.ft. give or take a little. It'll end up 7.something loaded up, a good size for the legend or other good 15's. That'll be a good balance of lowend and power handling. Those cb15's are pretty forgiving to work with so if you're off by 1/2" or something, no big deal.

[will33]

Be sure to use INTERNAL measurements when sizing it, that's what matters, not external. It needs to be trimmed down some but it's not as big as it looks. There isn't too much real estate in the baffle that isn't being used and the back looks to be set in an inch or two as well. Likely used to be a subwoofer. When you're done chopping it, you can lose that insulation that's falling down and line the inside with mattress pad foam.

[lowfreq33]

That looks near identical to a Genz Benz 2x15 I used to have, right down to the gray baffle. The handles are different though, maybe it's a homemade version?

Anyway, the one I had was a fine cab, I used it for several years before it was ruined in a flood. You won't get modern hi-fi tones out of it, but with a pair of efficient 15's in it it should be good.

[billfitzmaurice]

Originally Posted by Nalte

If it's designed as a P.A. cab, it may have too many booming lows and not enough cutting mids.

Boom is caused by a cab that's too small, not one that's too big. I'd just load it with Beta 15s and seal the ports.

[sturoc]

That was another question on my mind Bill,
How do drivers in a cab like this react when it is sealed ?