need speaker advice for small 15" cab

univox · #1 02-16-2011, 04:18 PM

Hi there-
As a guitar player who has picked up bass, I have been learning that amplifying electric bass is a lot different than guitar!

I have picked up a small 15" "Madison" cabinet loaded with an off-brand PA driver. I know that it's important to match the speaker to the cabinet so I'm primarily looking for advice on the correct driver.

Details:
- volume of the cabinet is 2.2 cubic feet
- (2) front-facing ports that are 3-3/4" dia.and are each 4-1/2" long

Questions:
- what is an appropriate 8ohm driver choice?
- is it necessary to have any kind of crossover/low-pass filter or just wire direct?
- empty cabinet or insulation?

Sorry for these seemingly basic questions, but I haven't found these answers elsewhere.
Thanks!
-steve

rptrsn2 · #2 02-16-2011, 05:34 PM

Think it may be too small but I love my eminence 3015. I know its fine ae small as 2.8cf but not sure bout 2.2. I do know if you call them they are always glad to help so ask them.

univox · #3 02-17-2011, 08:35 AM

thanks-

I was hoping to have someone work that "magic" that I have read about to calculate the box/port specifics... I guess I don't understand the relationship between the speaker and box; sometimes I read about the magic calculation and sometimes I read advice that says "stick a speaker in and see how it sounds"

Anyone else care to chime in?

jastacey · #4 02-17-2011, 10:11 AM

Here's my take .... the Eminence Kappa-Lite 3015 is a pretty forgiving 15" speaker, it's spec's say the smallest vented cab is 1.8 cubic feet, and the largest cab is 5.1 cubic feet/vented ..... I'd use it, and have used it in small cabinets, and have been happy with the sound .... no need to use any crossover, just wire it direct, line the wall inside the cabinet with some 3/4" this or thinner polyfirbefill, this will help control any standing waves in the cabinet, keep the ports clear of any cabinet lining ... plug the cab to your amp and play ..... and start saving for a bigger cabinet ...... If you have the time, you can play with the tuning of the vent lengths, but you'll need some software to come up with the diameters & lengths ... it may change the sound somewhat, but your better off building a cab from the ground up, if you go that route .... there are many different threads on TB that covers that ... all this is IMHO

4Mal · #5 02-17-2011, 10:31 AM

Is this for practice or gigging ? If it's gigging with electric guitars, dums, clasic rock sorta thing - IMO - get a better cab. If it's for practice and jamming in a typical house space then ... if you're going to be moving it a bunch the 3015 would be for the a good 'top end' choice. The other basslite's drivers might do just as well though is your volume requirements are 'realistic'.

If you don't have to move the cab, then a used peavey idow can generally be had darned cheap and they seem to do OK in smallish boxes. A little more weight though. Other choices in heavy magnet technology from Emenence (the Delta LF, Kappa or Omega LF models) or from EV will generally work as well... Craigslist is your friend for those as is a local recone shop. (I recently snagged a freshly reconed/rebasketed) Balck Widw for very reasonable from a reconer.)

If bass playing takes hold, you can get a good bass cab for not a lot of dough (look at Avatar ...) so if this is for you getting the hang of things, maybe shooting a little lower the first time would be wise... For less than double the dough of the 3015, you can land the Avatar SB112 for instance. I've done many gig's on one of those, the guy I sold it to gigs it on a regular basis...

When you compare that cab with ANY cab housing a bare 15 ... you aren't going to pick the bare 15 as your fav. Which makes me wonder if a $170 speaker is a good investment for you ...

Questions:
- what is an appropriate 8ohm driver choice?

all the above can be had in 8 ohms
- is it necessary to have any kind of crossover/low-pass filter or just wire direct?
A bare 15 doesn't require a crossover. If your cab has mid rane &/or tweeter, then you need a crossover.

- empty cabinet or insulation?

Wally world for polyester quilting/batting in sheet form. Stuff the thing to dampen the box. Keep the stuff away from the back of the ports. Line the box once using some 3m adhesive pray to hold it in place. Then add another layer and 'tack it down' in spots with the spray. load the driver, listen, repeat with another layer... repeat until that last layer doesn't sound so good, yank that layer and there ya go... Wear rubber / laytex gloves while working with the spray in a cab. Do it in a ventillated space.

rpsands · #6 02-17-2011, 10:35 AM

Is the volume you calculated internal volume less the ports, and have you subtracted the space of handles and the approximate displacement of the woofer?

If you're looking at gross internal, net internal will be closer to 1.9 or so cubic feet after everything is removed. If that is the case you are better off replacing the baffle or using a spacer to enable using a 12" woofer. There is no 15" woofer that will do very well in that space, unless you are willing to accept a lot of boom.

If you're OK with a boomy tone, throw an eminence beta 15 in there - they're cheap and get the job done, and are pretty loud for the money. It'll boom but that's life with a tiny box. It'll sound like most combo amps

univox · #7 02-24-2011, 08:59 PM

you've pointed out some things I didn't consider...

I took the measurements a while ago but yea, I think they're gross so actual volume might be a little less.

I do have an Avatar 210 that I've been using for gigs and the 15 has been at the rehearsal space. Fortunately the band I play with has been getting gigs with PA support so I'm primarily concerned about stage volume. I thought the 15 would be good to put under the 210 to A) add a little bit and B) to get the 210 closer to my ears. I also thought it would make a cool-looking tower of power since they stack nicely.

there is currently a slightly bigger cab (24x18x20?)locally on CL loaded with an Electrovoice EVG 15" for a total of $75. I think it's an older PA bass driver. ANy thoughts or experience with that one?

I guess I've been a little TOO focused on small and portable!

DukeLeJeune · #8 02-24-2011, 09:13 PM

Agree with the Kappalite 3015 suggestion.

Your tuning frequency is a bit on the high side, somewhere in the 59-60 Hz ballpark. May be okay with four-string; maybe not with five-string. Estimate 1 dB bump centered on about 120 Hz, and -3 dB in the high 60's.

Same diameter ports but 8" long would probably increase power handling, reduce the upper bass bumpage, and raise the -3 dB point to about 70 Hz.