Re: Double Loaded. - Paul Eizik - High Efficiency Speaker Asylum

Re: Double Loaded.

Posted by Paul Eizik (A) on May 13, 2003 at 16:38:56

In Reply to: Re: A front horn / back horn hybrid? posted by Bill Fitzmaurice on May 12, 2003 at 16:56:48:

Hi Bill

I beg to differ. This type of design dates back at least to 1936 when it was presented in the Journal of the Acoustic Soc. of America by Olson and Massa as a "Compound Horn Loudspeaker". It is also discusssed and pictured in Harry Olson's "Acoustical Engineering" as Steve mentions. I am unfamiliar with the 1958 patent you cite, but it would'nt be the first time some prior art by Harry messed up someone's patent. Harry's measurements show some moderate ripple of about 3 dB or so in the crossover region of the front and back horns, much less than seen in the high frequency response which dives around 4K and gets some 5 dB bumps before this. This type of design is also discussed by Dinsdale in his now famous (infamous to some) Wireless World articles of 1974, and the design type is also called the double loaded horn driver. Dinsdale addresses the design consideration that the two sides of the driver are out of phase with each other (like the ported box), and recommends that the combined lengths of the two horns be an odd number of half wave lengths of the frequency at the crossover point. I guess that guy in '58 had some fine tuning to do.

The double horn loaded driver has some advantages:

1. The mid bass horn and the mid range driver can be easily phase alligned with each other, a considerable advantage over designs like the Klipsch horn. Olsons's original design was a 1 way though.

2. It's an all horn design with no mismatch in output between the bass and mid bass like the V.O.T. has.

3. An easy to design compact cabinet is possible. Due to the fact that it is desireable to limit high frequencies coming from the back of the diaphram, 180 degree bends (with a subsequent "muffler effect") in the horn being driven by the rear of the driver are fine. The basic design can be a "W" manifold on top which exits into an "S" horn.

Some disadvantages:

1. Tricky to design by the numbers, as the two horns can be be computer modeled but their combined behavior is somewhat of a wild card as most programs assume reactance annulling with a closed box at one end, or free air termination.

2. Classic reactance annulling with a closed box at the back of the driver is impossible. This is offset to a certain degree by the fact that driver has the acoustic resistance of a horn (albeit different horns) on both sides, but the horns are less easy to adjust than a box.

3. Since Dinsdale, the design seems to have sunk into obscurity, and perhaps seems a relic of the "cut and try" days, and thus unattractive to those who want a + or - 1 dB computer sim even before they start the table saw. But to others this feature places it in the above group.

4. Time delay of about 1 millisecond for every ft. of length of the long horn. This is much more of a purist fault than the crossover overlap IMHO, and I'm surprised no one mentioned it in the other posts, but the many Lowther cabinets have this same delay and whatever else you can say about Lowthers, this is one complaint I have'nt heard yet.

To answer the original question, I have been using a design like this for over ten years (see pic in Members Rigs section of the C.H.C. link quickly before Tom Brennan gets the wanderlust and runs away with the gypsies). The double loader works for me!

Paul. BTW...

I enjoyed the Panel Cutter article in AudioXpress. I have employed panel cutters in the past and can attest to their usefullness, but I gotta confess that I don't have one handy right now (cut and curse method). Well, summers here...

http://www.chicagohornclub.org (Open in New Window)

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Follow Ups Full Thread

Topic - A front horn / back horn hybrid? - smallpond 12:21:16 05/12/03 (17)

Re: A front horn / back horn hybrid? - Tom Dawson 15:46:35 05/14/03 (0)

Re: A front horn / back horn hybrid? - Steve Schell 22:42:33 05/12/03 (0)

Re: A front horn / back horn hybrid? - Bill Fitzmaurice 16:56:48 05/12/03 (14)

Re: Double Loaded. - Paul Eizik 05/13/0316:38:56 05/13/03 (4)

Re: Double Loaded. - Paul Scearce 07:28:30 05/14/03 (1)

Re: Double Loaded. - Paul Eizik 19:22:06 05/14/03 (0)

I built one of Olson's double horns - Bill Fitzmaurice 04:56:17 05/14/03 (1)

Re: I built one of Olson's double horns - Paul Eizik 20:12:48 05/14/03 (0)

Re: Yes.. - Dave-A 18:33:59 05/12/03 (8)

Yep - smallpond 19:44:25 05/12/03 (7)

Re:Here's the thing... - Dave-A 07:22:20 05/14/03 (0)

Re: Nope. - Paul Eizik 17:49:59 05/13/03 (2)

Re: Nope. - Michaelz 05:18:21 05/14/03 (1)

Re: Yep. - Paul Eizik 20:42:30 05/14/03 (0)

Re: Yep - Chef Henry 12:45:35 05/13/03 (2)

Re: Yep! - Paul Eizik 19:15:03 05/13/03 (1)

Re: Yep! - smallpond 00:00:12 05/14/03 (0)

Follow Ups

Re: Double Loaded. - Paul Eizik 05/13/0316:38:56 05/13/03 (4)

Re: Double Loaded. - Paul Scearce 07:28:30 05/14/03 (1)

Re: Double Loaded. - Paul Eizik 19:22:06 05/14/03 (0)

I built one of Olson's double horns - Bill Fitzmaurice 04:56:17 05/14/03 (1)

Re: I built one of Olson's double horns - Paul Eizik 20:12:48 05/14/03 (0)

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