Speaker sensitivity vs SQ

@phusis wrote:

"What’s particularly interesting with high eff. larger speakers, to me, is that simplicity can be maintained when incorporating horns or waveguides fitted to compression drivers, and thus avoid some of the complexity issues that face low(er) eff. larger speaker designs. A 2-way high eff. design can be had with fairly large woofer/mids crossed to a horn/waveguide with very nice power response in the XO-region, though needing subs augmentation. I use such a configuration myself, now awaiting new horns from ~700Hz on up with a mouth area of some 2 x 3 feet for controlled directivity if needed, down to 500Hz for a smoother transition to the dual 15" drivers below."

This is almost exactly what I’m working on, and had hoped to introduce in 2020 but... stuff happened that year...

Anyway I designed a large-format Oblate Spheroid waveguide using Earl Geddes’ equations, like you targeting a 700 Hz crossover to twin 15" midwoofers. That 700 Hz figure is consistent with the findings of David Griesinger which Geddes subscribes to, and is very close to the 800 Hz crossover that Greg Timbers uses in the JBL M2. Imo the ability to cover the spectrum from there on up with a single driver is a major advantage over more "conventional" approaches, in addition to the other advantages of large drivers and high efficiency.

And of course the way around the bass extension/box size/efficiency tradeoff relationship is to hand off the bottom couple of octaves or so to subwoofers.

I’m rather surprised by how similar our approaches are. I knew we were barking up trees in the same forest, but didn’t realize it was the same tree!

Duke

Speaker sensitivity has little or nothing to do with sound quality. High or low sensitivity speakers are merely two different paths to same destination. Matched with the proper amplifier, either have the capability to produce satisfying sound quality. Of course, some will do this better than others but there are many variables much more important than a speaker's sensitivity.

Duke - IF you can say, are you 3D printing the waveguide ?

best to you in 2021

Jim

bdp24,

I agree with you about the relative merits of Soundlab electrostatic speakers vs. the Altec Voice of the Theater speaker.  The Altec tonal coloration is way too unnatural for my taste as well.  At one time I considered buying Soundlab speakers.  But, while most of the commercially available compression driver systems suffer from too much tonal issues for my taste, I've heard many custom systems that sound very good; I ended up with such a system.

I feel the same way about many other high efficiency speaker types, such as full range single driver systems.  I ultimately don't like their tonal balance and rough frequency response (notable exceptions are Charney Audio and certain Voxativ models).

I like some systems that use "fullrange" drivers as wide range drivers in multi-way systems.  In some, a woofer supplements the fullrange driver, in others, a tweeter is added on top.  An example is the Soundkaos Model 42 (fullrange driver plus a Raal ribbon tweeer on top).  My favorite system utilizes an old Jensen M10 fieldcoil driver (13" fullrange driver) in an open back cabinet (open baffle) operating full range, but with a first order high pass crossover to a tweeter supplementing the single driver (the system I heard had a Jensen RP 302 tweeter, but, I am told that a Western Electric fieldcoil 597 driver is better).

Pa speakers are much more sensitive than hifi speakers, but produce more ditstortion and do not have the same frequency range. To compensate they require active filtering and subwoofers. Making a sensitive speaker isn't that complicated: a woofer with a stiffer suspension (= less lower frequency) and a compression horn tweeter (= more distortion). A pa speaker with the sensitivity of an average  hifi speaker would require a truck full of amplifiers to achieve the same decibels. That's why in sound reinforcement only the max db level of a speaker is most  important. for each 3 db more, the amplifier power has to be doubled!