Do I need to lower speaker impedance when changing from 6v6 to 6L6's?

[kleuck]

I own the CR little brother, the Lil'Buddy, so i'm sure the CR would be great for Jazz (not only, but one of th best and cost-effective choice, the Lil'Buddy already sounds HUGE)

[Chuck H]

The lil' buddy does have a hemp cone (with a ? nexy to the designation) but an efficiency of 99.1dB. That's almost 3dB less efficient than the CR. 3dB more efficiency is like doubling your watts. Other than JoeM I don't feel like the point is hitting home here.

[kleuck]

I understood that the point was to find an efficient speaker, suitable to play Jazz.
I know the LB efficiency, as i Know the CR efficiency, but i only speak of my own experience, and i own a LB not a CR, but they are similar except the size, so i just say -as the sound is perfect for jazz, not really my taste but some Jazz players tried my amp- "If i find the LB HUGE, the CR must be MORE POWERFUL !!!"
Get the point ?

By the way, the official efficiency is not really useful, as i own also a Ramrod, with an efficiency of 100 dB which is way louder than the LB, wich is WAY louder than an Legend 105 which is supposed to be a 98,7 db loudspeaker.... differences between the LB & the Legend 105 should be impossible to hear theoretically....

[Steve Conner]

The efficiency rating of the speaker is just the height of the highest peak on the frequency response chart. But perceived loudness has more to do with the area under the curve, multiplied by the transfer functions of the cabinet, the bar you happen to be playing in, and the Fletcher-Munson contour for whatever volume you are playing at.

Implications: No speaker has say 100dB efficiency across its whole frequency range. To get this kind of SPL the maker must engineer a big peak. If this is at 4kHz the speaker will seem louder than another with 100dB efficiency at 400Hz, because the ear's sensitivity is highest in the upper midrange.

And conversely, jazz guitarists often prefer speakers with a flatter frequency response, so they have to settle for lower efficiency. The flat frequency response is achieved by damping the peaks. I guess this is what klueck means when he says the Lil Buddy is better even though it's less efficient. The Eminence Beta series are the logical conclusion of that line of argument.

So you can see that efficiency and tonal balance are hopelessly tied together.

[kg]

Implications: No speaker has say 100dB efficiency across its whole frequency range.

well, of course it depends on what you define as "whole frequency range," but some horn loaded designs can do it.

nobody uses them for guitars afaik.

[Chuck H]

It's funny that guitar speaker response charts tend to look VERY similar. So much so that any difference between them could never qualify for Steve's "3dB" criteria. But then there's the impedance curves... These seem to very a bit more. So it seems to me that the impedance at a given frequency must also be effecting amplifier efficiency at that frequency. Maybe a more important efficiency measurement than the response chart. I have yet to figure out how to predict how a speaker will actually sound looking at the response chart alone. Still, in my own experience and probably due in part to the similarity of most guitar speaker response curves, a "more efficient" speaker WILL be louder than a less efficient one since guitar speakers almost never have a broad peak or even a greatly dissimilar peak frequency.

[kleuck]

It's funny that guitar speaker response charts tend to look VERY similar.

Not always, but for example, the Legend105 and the Ramrod have very very similar curves, though they do not sound similar at all :