JBL cabinet design

[Horsefeather]

I have a Fender Bassman 50 cabinet with 2 D130s in it and also an unmarked 1x15 cabinet with a K130. I just ran a back to back recording test using the same amp and a looper pedal playing the same thing through each cab. I was shocked by the difference in tone between these two cabinets.

I knew the Bassman 50 was kind of mid-heavy but I wasn't prepared for how utterly shitty it sounds compared to the K130 cab. Now I'm wondering if my reconed D130s are just old and have lost a bunch of treble and volume. In addition to sounding muddy compared to the K130, the D130 track had to be boosted about 6 dB to reach the same level as the K130 track.

My main question, though, is can cabinet design affect the sound this drastically? The K130 cabinet is very well proportioned, according to JBL's cabinet design PDF. It's 5.9 cubic feet with a 35 square inch port.

The Bassman 50, on the other hand, is only 4.6 cubic feet and has no port. And is housing TWO speakers. I know it can be replaced with something else and they'll sound better but I can't help but doubt they're going to end up sounding as good as the K130. Anyone have any thoughts?

[øøøøøøø]

My main question, though, is can cabinet design affect the sound this drastically? T

In short, "yes."

Enclosure design is one of the most important determinants of driver performance.

[Horsefeather]

I've discovered that both of my D130 recones used the Waldom kits that seem to be universally loathed so that's probably a significant part of this equation. I'm going to be redoing them and see how the sound changes.

When I disconnected one of the D130s in the Bassman 50 cabinet, thereby increasing the effective air volume for the other one, I didn't notice much of any change in tone, which further reinforces my thought that it's the speakers themselves more than the cabinet.

[øøøøøøø]

Those recone kits are bad and you’re making the right decision, BUT—cabinet volume is not a “more is better” proposition.

A good cabinet design is tuned using the Thiele-Small parameters of the specific driver (if you want to maximize performance). Or you build a box and hope you get lucky. Not all that different from room acoustics/design in that regard!

And FWIW, when you disconnected one driver, you didn't effectively increase the air volume for the other-- you converted an acoustic suspension cabinet into a bass reflex design by converting one of the drivers into a passive radiator!

[Horsefeather]

Ahh, that's what a passive radiator is. I read that term somewhere but didn't bother to search out its meaning. Thanks for the info.

I know bigger isn't necessarily better, regarding cabinet sizes, so I'm just trying to stick to JBL's PDF that prescribes internal volumes for their speakers along with port dimensions.

When using a chart like that, which seems based upon 1x configurations, how do you interpret for a 2x cabinet? Do you just double everything? What I plan to do is put the rebuilt D130Fs into a Fender 2-15 cabinet from the 80's--it's the one that went with the Bassman 135 I think. It has 6.6 CF of volume, as measured between inside walls with my laser, and a 28 sq in. port at the bottom. Does this seem reasonable for guitar duty? Should I line the thing with fiberglass insulation?

[øøøøøøø]

Don’t *think* it’s that simple, but enclosure design is something I’ve never researched nor attempted!

Honestly, in this case I’d do one of four things:

1) install them in that Bassman box and hope you get lucky

2) try and find an old/empty Showman 2x15 cab for cheap

3) get showman cab dimensions and try to build a copy

4) research T/S parameters for the D130F, then research a bit about how you’d use those to calculate ideal cabinet volume and port size, and see if the bassman cab is in the ballpark.

Honestly, if it was me I’d probably try either option 1 or 2 first!

And yeah, I would probably put fiberglass insulation inside the cab.