Beyond the Ariel

[cuibono]

Thanks for the explanation Augerpro! I look forward to more measurements.

[CLS]

Hi ScottG,

Thanks for the insight. And yes! NSD1095N looks excellent on paper!

[D OB G]

As reported in another thread, I compared NSD1095N to DE250.
Each was individually optimised using DEQX.
Results might be different with passive EQ.
Both were on 18sound XT1086 waveguides.
The NSD1095 is "made to match" the waveguide. Flare rate e.t.c.
The DE250 is not.
I don't have impulse response results.
I gave them a long, long, long listening test.
The NSD1095N seemed subjectively more detailed at first listening.
The NSD1095N WAS more detailed after extended listening.
I couldn't find any area in which the DE250 was better.

David

[CLS]

Hi David,

Yes, I found it here:
18sound NSD1095N v's B&C DE250
(also lots of valuable comments from Scott, and others.... )

There were lots of debates in that thread, I'm not surprised about that for the subjective stuff, it's usually more so if your opinions happened to point against others. Oops!

Anyway, I do appreciate your efforts, reviews, and sharing about the comparisons of those compression drivers. I think I can understand what you wanted to describe and also tend to agree despite the fact that I've never heard them myself. I'd guess the differences might be similar to other hard and soft diaphragms. Talking about details and dynamics, hard ones usually win.

CLS

[SunRa]

This thread has been like a good novel until now, I hope it won't end any different..

Any news on the build, Mr. Olson? Did you managed to assess the acquired midrange drivers?

[Lynn Olson]

Originally Posted by Speedskater

Where is Lynn Olson? Is he well? I don't think that he has visited the forum in over a month.

Hi there, yes, I'm still here. I just haven't had any brilliant (or otherwise) ideas to report. I have been corresponding with the local Denver guy who does the Drivervault measurements, but that's been off-line. I'll be at the RMAF with my friends Gary Dahl, John Atwood, and Alexander of RAAL, so if any of you are there, I'll probably be seeing you!

I have been looking carefully at some of the basshorns at the Bill Fitzmaurice site, specifically the OmniTop 12 and 15, which look like good complements to the AH-425 Azurahorn and Altec/GPA 288 compression driver.

[Lynn Olson]

Augerpro was kind enough to measure the second GPA 288 on the AH425 horn - and as you can see, it measures differently. (All measurements at 2 meters with no equalization.) This measurement is much closer to Bjorn Kolbrek's measurement of his Altec 288C on his AH425 horn, so the previous measurements of the GPA 288 may indicate a problem with that particular driver.

I'm no horn expert - but I'd guess the phase plug might be misaligned with respect to the diaphragm, producing the broad rise centered around 1.5 kHz and the two sharp nulls at 2.8 and 3.6 kHz. The first driver has a smoother characteristic in the 1~10 kHz region, with the diaphragm breakup region above 10 kHz looking very similar.

[Lynn Olson]

Here's the reason I've been poking around the Bill Fitzmaurice site - the OmniTop 15 and 12 look like interesting complements to the AH425. The upper graph is the dual-15 OmniTop 15, and the lower graph is the dual-12 OmniTop 12 (these are fullrange speakers, but the part I'm interested in is the basshorn).

Note the efficiencies of an OmniTop15 and an AH425 with an appropriate large-format compression driver are in the Klipschorn range, with much flatter response. True, the F3 is around 70~80 Hz, but everything below that is direct-radiator subwoofer territory anyway.

The reason you don't see FR response measurements of Klipschorns and Avante-Gardes published is that they aren't very flattering - rough would be the kindest word that applies. By contrast, with a good large-format compression driver (GPA, Altec, and possibly the Radians), the AH425 horn, a 700~900 Hz crossover, and 12+15 or 15+15 BFM OmniTop, a speaker with efficiencies in the 105~109 dB range and reasonably flat response looks eminently possible.

[Lynn Olson]

A speaker like the combo described above isn't as weird as it seems - historically, it's a descendant of the late-Forties Altec A4 and A5 theater systems, with a basshorn with a vented rear chamber, and a large-format compression driver handling the mids and highs.

The difference is modern modeling techniques - courtesy of BFM, Bjorn Kolbrek, and JMLC - which allows much flatter response than the old-school theater speakers. Not surprisingly, the frequency limits and choice of crossover is similar; 70~80 Hz in the bass, 10 kHz at the top, and a crossover set by the horn size, which was 500 Hz for the big Altec multicells, and 700+ Hz for the AH425.

(1975 Altec catalog photo from the Lansing Heritage site, with minor Photoshop color-correction. The A5 is on the far left, and the A4 is on the far right side of the picture.) I like the sense of scale in this picture; anyone that's seen an A7 in a living room knows they aren't exactly petite, yet they look small here, compared to the mighty A2, intended for 70mm widescreen theaters.

[agent.5]

I read that omnitop 12 is a ported horn.

http://forum.speakerplans.com/bill-f...096_page6.html