Detuned 1x15 Bass Cabinet (first build)

[GregS]

I just finished building a detuned 1x15 cabinet for the Ampeg Portaflex B15N clone that I recently built. I thought it might be of some use to post my experiences with this as I didn't find much information on detuned cabinets here - especially for bass.

I built the cabinet large enough for two 15" speakers even though I only use one. It's as big as it can be and still be manageable to get in and out of my car.

I used a Weber 15" California ceramic magnet speaker.

The cabinet was built entirely from materials at Lowe's home improvement store with the exception of the handles and feet. The panels are 3/4" Douglas Fir plywood including the baffle (not sure if this is a good type of wood for tone or not). I used butt joints re-enforced from the inside by 2x2 strips both glued and screwed in place. The cabinet is extremely strong. The covering is indoor-outdoor carpet. I made a wooden frame for the grill with fiberglass screen door mesh. The jack plate I cut from a thick piece of sheet metal.

How it sounds:

It sounds much better than the commercial 1x15 cabinet I was renting from the music store while I was building it - not my bias, anyone would think the same. The commercial cabinet had a hollow muddy tone on the lowest notes and had some other places in the range that weren't great sounding. The detuned cabinet sounds very nice throughout the range. The bottom end has good definition on the notes although it doesn't seem as loud as the commercial in this range. Playing with it at band practice, it doesn't sound as loud as the commercial to me where I'm standing in the room but the other band members say they're hearing the bass better. I don't know. Perhaps the sound is dispersed around the room more and is less directional with the detuned design. Overall, I'm happy with the results and feel the amp is now a great sounding amp.

I have a few pictures.

Greg

[GregS]

Another picture.

[GregS]

Another.

[GregS]

Final picture.

[Steve Conner]

Hi GregS

The reason you don't read much about detuned cabinets for bass is that they're generally considered to be somewhat of a bad idea.

This is because a sealed cabinet, or a properly tuned ported cabinet, provides some loading to the speaker cone, limiting the excursion (distance that the cone moves) to a safe value. A detuned cabinet doesn't load it at all, and also rolls off the low frequencies prematurely, which encourages you to boost the bass on the amp, making matters even worse. With a high powered amp, you'd end up blowing your cone to shreds.

The good news is:

A Portaflex clone probably doesn't have enough power to wreck your speaker, irrespective of the loading.

Commercial ported cabinets are tuned to work with the high damping factor of solid-state amps, so can sound muddy with tube amps. The detuned cabinet isn't tuned at all, so damping from the amp matters less.

Bass is all about the midrange anyway, unless you're playing in a Bob Marley covers band and need to shake some booty.

If you do need to shake booty, you can just put another 15 in the other hole.

[GregS]

Yeah, the amp only puts out about 25W and the speaker is rated for 80W so I should be safe there.

Interesting info about detuned cabinets and commercial ported ones.

Do you think detuned cabinets will work well with guitar amps?

Greg

[mooreamps]

Do you think detuned cabinets will work well with guitar amps?

Greg

Supposedly. But when I built my prototype 2x12, it was 2 speakers isolated inside the cab. The lower speaker ported, and vented out the front, and the upper speaker internally sealed and closed. We play through on stage, and it seems to project really well. Also, with the upper speaker internally tilted back , it really lets the player "hear" what's coming out of it. Now, of course, this layout is down-rev, and I mount the speakers differently.



-g

[GregS]

That's an interesting design.

Greg

[mooreamps]

That's an interesting design.

Greg

The lower speaker borrows from the old klipsch horn layout. It makes the effective size of the cabinet of the lower speaker much larger than the inside dimensions of the cabinet.



-g