Speakers and cabinets

[Morten Stenbaek]

Anyone have any experiences with speakers and cabinets they want to shear ?
Speakers : 8” – 10” –12” different sizes in combination etc.

Cabinet:
I’m thinking about size (debt and with) is oversize a way to go for bigger sound ?
Bafflebord thickness ?
Closed / open back ?
How should speakers be placed if an oversized cabinet is used (placed evenly or close together ?) ?

Looking forward to the debate : )

[Earl Norton]

For Harp?????

[Morten Stenbaek]

Well this section of the forum is dealing with harp amps right ?

[Bruce / Mission Amps]

Well this section of the forum is dealing with harp amps right ?

HA ha ha ... yes.

Make the carcass deeper then the standard 9"-10" thing and the baffle thinner, like no more then 3/8" plywood or 5/16" MDO and use light weight lumber for the cabinet carcass.
IMHO, 3/4" Baltic birch is a little bit stiff for a harp amp.
I think I prefer a little thinner cabinet made out of 5/8" or softer 3/4" pine that has been finished down to around 11/16".

[MWJB]

8" - limited choices in 8" especially in 8ohm, typically lower efficiency than 10"s , often have to wire in series parallel (not good) to get impedances right.

10" - loads of choices (relatively), I'd recommend Eminence 102, Kendrick Blackframe & Fane AX10 (only use 2 in a 4x10"). Better efficiency than 8"s, better feedback rejection than 12"s.

12" - Not that many good choices for a harp amp, worse at rejecting feedback than 10"s (you will therefore struggle to get the same volume from the amp), cones are slower off the mark and can be dull sounding compared to 10"s, better sound dispersal than 8" or 10". That's not to say that they can never sound good (never say never) but this will not be the easiest route to take (I have a dozen 12"s just gathering dust).

[MWJB]

Also...

The final choice of which size of speaker and how many you intend to use will depend to some degree on the type of circuit you use (fixed/cathode bias, for instance).

I also think that there is an advantage in building multi speaker cabs tall & narrow, where possible) rather than low & wide, in respect to both feeback rejection and on stage monitoring. E.g. a 2x10" may be arranged with one speaker above the other vertically, rather than side by side on the horizontal plane (though obviously a 4x10" built like this would be impractical).

Speaker configuration plays a very important part in limiting feedback, which in turn, is the main limiting factor in getting good power from a harp amp.

[clyde1]

8's are the bomb, minimum 4, try 6 even. They just have that tight sound and with more, they're thicker.

[MWJB]

Which 8"s? A lot of 8"s are 4ohms, how do you wire them in parallel when using 4 or 6 of them (even at 8ohms)?

[dl5mhk]

Which 8"s? A lot of 8"s are 4ohms, how do you wire them in parallel when using 4 or 6 of them (even at 8ohms)?

4-4-4 parallel with
4-4-4 makes 6 Ohms.

8-8
8-8
8-8 makes 5,3 Ohms.

6 speakers with 16 Ohms makes 2,66 Ohms when wired parallel.

The 1st two choices work with 4 or 8 Ohm OT's, the last one with 4 Ohm,
don't you agree?

cu,
Ralf

[MWJB]

Agreed. The last 2 choices will "work" with 4 ohm OT. 6x8" at 16ohm,
in parallel (2.66ohms) will also work with a 2ohm OT.

My point is that connecting speakers in series sacrifices efficiency (all things being equal 8"s are not as efficient as 10"s) and lowers the ceiling of feedback with harp.

[dl5mhk]

My point is that connecting speakers in series sacrifices efficiency (all things being equal 8"s are not as efficient as 10"s) and lowers the ceiling of feedback with harp.

Oh...my Alligator amp makes people wonder about his feedback resistance, and it uses 6x8. Eventually 6x8" is not as efficient as 4x10", but what i like with them so much is that they are "faster" than those. For me, they sound more "crisp". But as always: Your mileage may vary.

Btw: Would you rather use a selfbalancing paraphase PI or would a fixed one work better for harp? I changed the longtail PI to paraphase selfbalancing style (as in the 5D4 Super Amp), it's not bad, but the most of the sound comes from the preamp in the moment, that means: soundwise is not so much difference.

cu,
Ralf

[clyde1]

The best harp amp I've heard extensively is the Gibson Maestro,
4 8's wired series parallel for 8 ohms. I've never heard the Sonny Jr.'s or the Gibson GA-90 with 6 8's, reportedly one of Kim Wilson's favourites.

[MWJB]

Sure it's "swings and roundabouts" and personal preference plays a big part.

I've not investigated parphase PI's to any great extent, only built & modded long tail PIs. The theory is that you always get some grind because the signal going to the 2nd half has already been amplified by the first. Harp amps have been built using both styles.

[MWJB]

Indeed, I've heard great things about the Maestro 4x8" and the GA40LP that it resembles (apart from speaker compliment). But would it sound better & be more efficient with a 2ohm OT and speakers in parallel? I am sure it would.

The amp's suitability for harp (I'm not suggesting that it doesn't sound great, but that doesn't mean it couldn't be improved) wouldn't have been the first thing on the designer's mind, how to utilise the 4 speakers with the same 8ohm OT as the GA40 would have been.

A friend of mine auditioned a GA90, cool sound, a monster for feedback but still only a recording/small venue amp. Kim was rumoured to have used one on Tiger Man...though he is supposed to have told an aquaintance that he "always uses the same thing in the studio...a champ". I take it all with a pinch of salt.

[Bruce / Mission Amps]

...
My point is that connecting speakers in series sacrifices efficiency (all things being equal 8"s are not as efficient as 10"s) and lowers the ceiling of feedback with harp.

Huh? I'm confused by this "series sacrifices efficiency" statement... do you mean you believe the speakers are not as efficient because they are wired one way or another with respect to series or parallel, in order to acheive a correct impedance match?
That doesn't make any sense to me so I must not understand what you are meaning here.
The efficiency of a speaker or speakers is totally independent of the signal phase so what am I missing?