Cab For Kappa 3015's

[MostLow]

Hello, new user here. I have 2 Eminence Kappa 3015's that I put in custom 1x15 LDS cabs that were built for JBL K140's, tuned to 40hz. Each cab is about 4.7 cu/ft with 2 ports originally 4" x 6". I extended the ports by 2", so now 4" x  8", but the speakers are farting out on the lower notes (4 string). Seems like these aren't ideal cabs for the Kappa's, but I thought I'd give it a try with my limited knowledge.

My other options are a narrow Acoustic 2x15 406 cab, and a JBL 4648 2x15, originally designed for subs in movie theatres (yes, it's heavy). I realize the latter seems like an obvious no-go but it's about 8 cu/ft with 2 ports 5.5" x 8".

 

So, are any of these cabs viable, or should I start from scratch? Is there an ideal cab dimension for these? Thanks.

[Dan Dare]

Have a look at the data sheet for the drivers on the Eminence website. That'll give you cab' capacity, port sizes, etc.

 

Dave Green's Fearful 15 was designed for the Kappalite 3015 if you fancy building your own:

 

[Bill Fitzmaurice]

That diagram shows the 3015LF, not the 3015. The 3015 works best in 70 liters/2.5 cu ft (net) with  200 cm2 port area 35cm long for 45Hz tuning. 

[MostLow]

Thanks. The cab specs seem similar but now I know.

Edited Tuesday at 11:43 by MostLow

[Dan Dare]

38 minutes ago, Bill Fitzmaurice said:

That diagram shows the 3015LF, not the 3015. The 3015 works best in 70 liters/2.5 cu ft (net) with  200 cm2 port area 35cm long for 45Hz tuning. 

 

My bad, Bill. A thought occurs. Could @MostLow replace the baffle on one of his 4.7 cu. ft. cabs and add correctly sized port(s) and mount both drivers in it?

 

I've done that before by cutting out the old baffle with a jigsaw, leaving and couple of inches of the edges of it in place to mount a new one onto. It would slightly increase the internal volume and get it closer to the ideal of 5 cu. ft.

 

It assumes the cab is tall enough to accommodate two 15" drivers, rather than being deep, but with a small frontal area. Might that be relatively inexpensive and simple solution?

[MostLow]

No, the baffle board is 28" x 20.5". Too small for 2 x 15.

 

So a good 3015 cab would be something akin to the one in the pic here:

 

 

[Dan Dare]

Depends on the dimensions. If the driver in the photo is a 15, the cab looks to be about 19" wide by 12" deep by 24" high. That gives a cubic capacity of around 3.1 cu. ft, although the volume of the ports (which look a little large for the size Bill suggests above) will reduce that. It probably won't be that far off and certainly better than 4.7 cu. ft.

Edited Tuesday at 14:32 by Dan Dare

[Downunderwonder]

You could possibly make use of your LDS cabs as they sit by adding a high pass filter into your amplifier.

 

And / or, stuff one of the ports to raise the tuning.

[Phil Starr]

Welcome to BassChat

 

This is the link to Eminence's own designs for your Kappalite, basically they offer three different designs small medium and large. Congratulations your Kappalite's are great drivers for bass. As used in the original Barefaced Compact cabs.

 

https://cdn.shopify.com/s/files/1/0270/8665/1462/files/Kappalite_3015_cab.pdf

 

I'm a little surprised by your cab farting out. I'm not sure if you are hearing wind noise from the ports or over excursion of the speaker. I've done no calculations as yet but your cab is not far off the large cab in Eminence's own design, so this is unexpected. I also don't know what amp you are using or what your tone settings are but at full power the excusion shouldn't be excessive down to 40Hz which is basically bottom E, You'll notice in the Eminence spec they specify a 35Hz filter to protect the speaker. It might be the solution to use an HPF like the Thumpinator to remove the harmful but almost inaudible subsonics from reaching your cab. That will cure wind noise and over excursion. I also note that Eminence themselves only use 300W through the large cab not 450W. Incidentally in their 5cu ft cab they use two 3.5" ports 4"dia so you may be tuning too low. 

[MostLow]

Well, this is a bit embarrassing, but when I went to remove the Kappa's from the cabs I noticed one of them was wired backwards from the other (by me, doh), so between that and the cabs, I'm not surprised it didn't sound so great. I did use a Tech 21 Q-Strip pedal with a set 45Hz HPF, or an Alembic SF-2 Superfilter, but with the speakers being out of phase, was probably a bit moot.

 

I may have customs cabs made to specs mentioned by Bill here, or maybe go another speaker/cab route entirely.

I tend to play hollow body basses like the Epiphone Jack Casady, Gibson EB-2, and Guild Starfire, fairly aggressively (and loudly) and go for the ' big-and-heavy-but-transparent' 60s/70s classic rock sound  - that's why I like the JBL K140s, but hauling 4 of them (150w rms each for 600w rms total) gets a bit tiring and takes up a lot of space, so I'm looking at more modern lightweight high-powered, but still having something of an 'old school' sound, alternatives.

There's an Accugroove 'El Whappo' 15/12/6 cab for sale near me that caught my attention. I hear they handle lows very well and are plenty loud. Bergantino also sounds good but are way pricey brand new. I tried an Orange OBC115 and was totally underwhelmed with it. People have mentioned the 3015 is a good replacement for the stock speaker in those cabs, but they ain't cheap, either.

[Downunderwonder]

Cabs wired backwards will indeed fart out trying to get any bass out of them.

[Bill Fitzmaurice]

7 hours ago, Downunderwonder said:

You could possibly make use of your LDS cabs as they sit by adding a high pass filter into your amplifier.

 

And / or, stuff one of the ports to raise the tuning.

 The cabinet is simply far too large, so it doesn't provide the necessary restorative force to prevent over-excursion. That mainly relates to the driver Vas. For the K140 that's 297 L. For the 3015 it's 153 L. 

[David Morison]

On 08/10/2025 at 04:30, Downunderwonder said:

 

And / or, stuff one of the ports to raise the tuning.

 

Unfortunately, that would lower the tuning, which would make the drivers more likely to fart out, rather than less.

[Bill Fitzmaurice]

It would also result in chuffing, as the port area would be too small. 

[MostLow]

So a 2.5 cu ft internal volume cab would be about 16"L x 14"D x 20"H with a port total (?) of 31 sq in, so 13.77"L x 2.25"W.

 

I guess this guy's 3015 cab wasn't deep enough for straight ports so he used curved pipe. Interesting.

 

 

 

 

[Bill Fitzmaurice]

Port shape (duct actually, the name 'port' is incorrectly applied to ducts, but it's part of the lexicon now) doesn't matter, though narrow slots should be avoided. The area of those ports looks to be far too small.