Physics freaks: Multicell vs. Sectoral?

[Alien_Shore]

There is considerable hearsay and amateur opinion about sound quality differences in horns that are multicell vs. sectoral. For example, the original little horn on the Altec 604 and 604B (multicell) vs. later incarnations. Since it is subjective, there are opinions on both sides as to which sound better. I would like to find out more - to understand a bit more objectively as to the "why"...

I've done some digging around for some scientific papers on this topic, but it is sparse and either crap or reads more like a doctoral thesis. Here are few I've found that are fairly understandable:

Wide Angle Dispersion of High Frequency Sound - Abraham Cohen

The Quadratic Throat Waveguide - Charles Hughes

FOH - Understanding Horns - Phil Graham

Anyone have any better links?

[fpitas]

Good luck, and I'm interested in the literature too, but you'll find it comes down to personal preference in most cases. People have been arguing about (for example) the pros and cons of wide vs. narrow dispersion as long as I can remember, and many other horn parameters. About the only thing I've seen people agree on is the desire for reasonably flat on-axis response. Of course, these sorts of discussions aren't restricted to horn speakers. Some love (once again for example) the Bose 901, and other speakers featuring wide dispersion and lots of reflections, some don't.

I think the listening room, and its reverberation time, frequency modes etc. factor into the equation too, which may start to explain the differences people hear. Also, horns can be challenging to really get right. I suspect the reason a lot of people think horns sound honky or whatever comes down to improper phasing at crossover etc.

Also, the driver has a lot to do with it. I've seen people say the 511E sounds much better than the 511B, yet they use very different drivers. The basic horn is the same, simply cut off a bit at the throat for the 1.4" driver. Most of the multicells also use the 1.4" drivers, so it's tough for me to compare them directly to horns using the 1" drivers.

[GM]

Greets!

This is as technically & subjectively an involved subject as it gets AFAIK and one that Bell Labs and others has been studying for over a century now, but for me it boils down to human hearing perception, particularly WRT euphonic distortion, which is the same, yet not so much for each individual.

WRT sectoral Vs multi-cells, this boils down to how each generates & distributes euphonic distortion, so one has to look at throat/horn compression & 'slap echo' within the horn [AKA Dr. Geddes's HOMs] and how the Eigenmodes across the mouth and individual cells comb filter with the horn's output.

WRT comparisons of similar horns with different drivers, it?s normally about each being optimized to a different BW, so an apples n? oranges? comparison at best.

The only way I know how to compare them is to notch out each other?s advantage. I imagine it would be hard to tell the difference between a 511/511E if they were ~ ?brick wall? BW limited to ~1.25-5 kHz.

GM

[Old Guy]

The Duplex horns aren't true multicells. They really should be classed as sectoral IMHO. YMMV. The dividers don't go all the way back. Even in the really old ones. But the old ones are closer.



I just kinda feel we're stretching the definition.

[Panomaniac]

Agreed. Really sectoral with added vertical fins. I have 2 pair of Pioneer tweeters like that.

[gearfreak]

...example, the original little horn on the Altec 604 and 604B (multicell) vs. later incarnations.Anyone have any better links?

Not to contaminate the original post question, but of course eventually many (UREI, JBL/PAS, latter Altec) went to non-vaned / non-sectoral HF for duplexes.
Point being, I believe there is some discussion here on the board already about the newer GPA coaxials, and whether they are exponential or tractrix (?) or hybrid of some sort.
It might shed some light, working backwards.

[VolvoHeretic]

Almost looks like you could bolt a 811b on to the 604 and mounted in an A7 box would be interesting.

[Old Guy]

Almost looks like you could bolt a 811b on to the 604 and mounted in an A7 box would be interesting.

I think the throat is closer to the 1.4. been a while.

[gearfreak]

Almost looks like you could bolt a 811b on to the 604 and mounted in an A7 box would be interesting.

Neat idea. If you supported the 811 with something. But you just might end up with a broken 604. :-(

I did stick one of my 604-8 (K, L, ?) in the top stacked 828 at one point. That was many XO's and other experiements ago. Perhaps I will repeat it this winter and have another listen.