Modified a bass cabinet.

[isaac42]

The old driver was loud, but didn't go particularly low. I switched out drivers, ported the cabinet, and added casters and a handle. Results were very pleasing.

 

Details here: http://www.harmonycentral.com/forum/forum/Bass/acapella-17/31375043-new-old-bass-cabinet

[isaac42]

The old driver, the JBL 2032H, is a high efficiency driver. Gets loud, but doesn't go particularly low. Useful in certain situations. A JBL 2205A is a much better choice if one wants that bottom octave. OTOH, whether or not the driver I used actually qualifies as a 2205A is dubious, at best.

 

Some technical details I didn't bother with on the bass board. A 4 ft³ cabinet can be tuned to 41.2 Hz (low E fundamental) with a 3" id tube 0.55" long. The baffle board is ⅝" thick, or 0.625", so a 3" hole would tune it a bit lower, around 40.7 Hz. That wouldn't be a problem, but the port velocity is quite high when the port is that small. That can cause chuffing sounds at high volumes. As it happens, I have a couple of heavy duty cardboard tubes that are 3" id, 3⅝" od, so I decided to cut the hole 3⅝", allowing for installing a tube later.

 

All of these tunings yield a pretty nice -3dB shelf response with an actual 2205A. Same with a 2205H or K140 (which I also have laying around). -6dB is at 40 Hz. If one has a 9 or 10 band EQ (standard graphic EQ), 3dB boost at 62 Hz would make it almost flat in the 40-80 Hz octave.

 

I could also tune it down to 30.8 Hz (low B fundamental) for fun, but the bass response isn't nearly as flat. It rolls off at 3dB/octave starting above 100Hz. And I don't think the driver is built to move enough air to go that low. X_max just isn't big enough. So if I did, that would be a temporary thing, just as an experiment.

 

Another possible change would be adding a second 3" port. That would significantly lower the port air velocity. But I didn't hear any chuffing at the gig Saturday night, so maybe there's no need in this application.