stepped baffles and horns

[Paducah Home Theater]

http://www.troelsgravesen.dk/stepped-baffle.htm

So that's kind of interesting to me, been seeing several designs like that. But, even with a stepped baffle, you're only looking at like 0.5-0.75" difference.

What I don't understand is why the opposite isn't true with a horn in general. Some of these compression drivers are WAY behind the back of the cone of the woofer. Why don't you have to build the baffle out on the tweeter so that the phase is aligned? An 88 special stands out in my mind, you've got these shallow 8" woofers and this really deep horn. Why don't you have to physically align the compression drivers and woofers? Also when you use that same horn but with different woofers that are deeper, which happens such as with a 15" woofer, why doesn't the baffle change?

[pzannucci]

Looks like you need to go read all the discussion on time alignment and horns.  Why some of the forum members opt for electronic crossovers / speaker management with multi-amps.

 

The key thing is that the longer horns are so far out of alignment that they would require some very expensive enclosure alignment techniques to do proper alignment which also includes electrical phase changes introduced by the crossover.

 

Suffice it to say that the more inexpensive choice is a flat baffle with non-aligned drivers since it would not matter to 95% of the people especially when you introduce the additional cost of alignment.  Price point, complexity, and aesthetics wins most times for moderate volume sales.

[Chris A]

I agree with Peter--the major reason why time alignment is ignored in horn-loaded loudspeakers in the past has been due to cost, and before that, performance of the digital crossovers.  The performance issues went away at least a decade ago, while the cost issues are falling by the wayside right now. 

 

While there may be 95% that don't pay that much attention to the sound quality benefits of time alignment, it was PWK that said that 99% of consumers didn't buy his speakers due to cost and perhaps lack of a discerning ear for their advantages.  To an even greater degree nowadays, I believe that still holds true.  If you can hear the advantages of horn loading, then you can certainly hear the advantages of a well-done time alignment of those horns/drivers. 

 

As far as the article on "baffle step" (which I find to be a poor term since a baffle is really a flat plate, not a box.  Boxes can be closed or open (ported or transmission line):

 

I find that most folks that focus exclusively on direct radiator loudspeakers to the exclusion of horns simply do not have the knowledge they need to understand the effects of controlled directivity that horn designers typically know.  So the discussions are a bit odd, focusing on "flat frequency response" instead of directivity and low modulation distortion, i.e., high efficiency via their relative low acceleration moving mass of horns which act as acoustic transformers.  I've found that very few seem to really understand directivity and low moving mass as well as Klipsch's engineering staff as well as a few others. 

 

It seems that the age of direct radiators is just now run its course, starting in the early 1950s, along with its emphasis on certain kinds of measures of merit--flat on-axis frequency response, for instance, to the exclusion of measuring and minimizing modulation distortion.  Renewed interest in horns and horn loading has come into the spotlight as newer and more affordable analysis and test tools have become available, as well as advances in understanding of the physics involved.  Most DR loudspeaker DIYers and even real engineering designers haven't learned those basics yet.

 

YMMV.

 

Chris

Edited December 25, 2015 by Chris A