2x12 cab with heterogeneous speakers

[tinisuta]

hi all, I'm willing to build a 2x12 cab using a G12H-30 and a G12M. I know these two don't mix well since their impedances are quite different (100dB and 98dB respectively), but my wiring scheme will allow to use either the G12H-30 OR the G12M OR both in parallel.
In view of this, and knowing I'm more a blues player with a taste for thick, juicy tones, should I go for an open or closed cab ?
Is there any drawback connecting only one speaker in a closed-back ?
Finally, any suggestions about dimensions ? I heard many good reviews about Avatar's 212 and 212 vintage, but I didn't find the dimensions.

cheers

[CurtissRobin]

You're confused. The 100dB and 98 dB figures are for sensitivity (ratio of sound output to power input) and are unrelated to impedence which would be in units of ohms, typically 8 or 16 ohms in the Celestion G12 speakers. The small difference in sensitivity won't be noticeable. I can't speak to the combination of speakers you named but my open back 65 Amps London 2x12 has a G12H30 and an Alnico Blue and the sound is mouthwatering. Whether to use open or closed cabs is purely a taste/preference question since I've seen nearly all the professionals (since you're talking about blues, Albert King, BB King, SRV, Lonnie Mack, Buddy Guy, Robert Cray, Clapton, et al.) use both in different performances and venues. If you're unsure, use a head and build both open and closed cabs or install an easily removeable back on one cab. As for dimensions, I'd go the the name brand manufacturer's websites. Nearly all provide dimensions for their products on the product spec pages. Marshall's 2x12 extension cab is 745mm x 530mm x 310mm (29 3/8" x 20 7/8" x 12 1/4").

HTH
KennyO