12" Drivers for custom enclosure..

[VTypeV4]

I've got a half built enclosure that was originally going to be a very compact 4x12 for guitar. It belonged to a friend but he lost interest in the project and I've had it ever since. My plan is to slightly re-engineer it as a 2x12 + HF and have it as a 'vintage looking but modern sounding' bass cab.

It measures 27 x 27 x 14 internal inches which gives around 180 litres (ish) box volume. I'm happy to make it vented or sealed - which ever suits the chosen drivers best plus it doesn't need to flat down to 38Hz, a usable response down to about 65Hz is more than adequate for my requirements. I'm trying to voice the cab similar to my existing SWR cabs by having a slightly 'dull' sounding 12" that rolls off at about 2kHz (or lower) causing a slight dip before the HF component picks up at 3.5kHz. I already have a passive HPF from a Hartke cab that is 12dB / oct at 3.5kHz.

Normally I'd crack out my copy of Eminence designer but I've recently changed computer and it doesn't like it. Real shame as I've lost all the updated T/S specs from Eminence too.

My preferred speaker is usually Celestion as they seem to have the performance / price point just about right plus my experience with them has been very positive through the years. I'm happy to consider models from all companies if they're suitable and not horribly expensive.

Can anyone offer any driver suggestions / sealed / vented / tuning frequency as a starting point? Power handling is not a massive concern either - The biggest amp it will be driven with is a 200w valve amplifier plus I'm not trying to kill anyone at 50 feet!

Many thanks, Matt.

[stevie]

That's quite big. A 2x12 cab is normally half that size. I agree that the Celestion bass drivers are good though. The new Pulse 12 would probably work, or you could get a pair of the BL12-200X, which appears to be the same driver and is available for £45 from Lean.

Assuming the baffle is 18mm thick, cut two holes 127mm in the baffle for your ports.

[VTypeV4]

Thanks Stevie.

The box is a kind of 'inbetween' size - originally I'd considered a 2x15 but the drivers were such a tight fit even diagonally positioned, I decided against it..

[Balcro]

Hi there,

As Stevie says, either Celestion speaker will work OK in that box. By the way, my calculations are that it's
167 litres gross volume.

Just one other observation. It's a square box 27 x 27". Having an exact square dimension might well cause some unwanted resonances, so it's best to pad out one side of the box with hard polystyrene blocks if you can get hold of some. They take up volume without adding any real weight. Two to three inches should be enough. For every inch in depth of poly blocks you'll lose about 5.9 litres in internal volume, but in this case it's all to the good. No significant difference to the frequency response.

Edited November 15, 2017 by Balcro
Formatting on the page

[VTypeV4]

1 hour ago, Balcro said:

Hi there,

As Stevie says, either Celestion speaker will work OK in that box. By the way, my calculations are that it's
167 litres gross volume.

Just one other observation. It's a square box 27 x 27". Having an exact square dimension might well cause some unwanted resonances, so it's best to pad out one side of the box with hard polystyrene blocks if you can get hold of some. They take up volume without adding any real weight. Two to three inches should be enough. For every inch in depth of poly blocks you'll lose about 5.9 litres in internal volume, but in this case it's all to the good. No significant difference to the frequency response.

Thanks for that, I did some calculations in my head hence the VB discrepancy. 

I'd considered the standing wave / resonance potential but the solution suggested here seems the perfect fix.

Thanks again chaps.