The AH-425's are done
Just got this e-mail from Martin Seddon - the AH-425's are done. Approximate dimensions are 262mm long, 418mm overall diameter, and 135mm diameter for the flange. The portion of the horn that rests on the carpet (where the walls are 90 degrees to the axis) is about 350mm across.
The LeCleac'h T ratio is 0.707 (this value of T came out of on-going research being done by Bjorn Kolbrek - results so far show that results for 0.707 and 0.8 are pretty similar).
The similarity to the effective horn inside a 15" Tannoy is not entirely an accident, since this design adheres to the Newell and Holland design criteria of minimum coloration for horns.
The three larger holes in the flange are drilled for the GPA & Altec 288, 290, 299, and 399 mounting studs (which are supplied with the driver).
Just got this e-mail from Martin Seddon - the AH-425's are done. Approximate dimensions are 262mm long, 418mm overall diameter, and 135mm diameter for the flange. The portion of the horn that rests on the carpet (where the walls are 90 degrees to the axis) is about 350mm across.
The LeCleac'h T ratio is 0.707 (this value of T came out of on-going research being done by Bjorn Kolbrek - results so far show that results for 0.707 and 0.8 are pretty similar).
The similarity to the effective horn inside a 15" Tannoy is not entirely an accident, since this design adheres to the Newell and Holland design criteria of minimum coloration for horns.
The three larger holes in the flange are drilled for the GPA & Altec 288, 290, 299, and 399 mounting studs (which are supplied with the driver).
Attachments
The price is extremely modest considering what you're getting - about AU$600 a pair, and postage about AU$90 a pair (two of them pack into one box, and they are not fragile). Wood horns are many more times expensive, and the Music Concrete horns about double - and shipping a pair of concrete horns from France to the USA isn't that cheap.
The dimensions of the AH-425 are bounded by the maximum length quoted by Newell and Holland, as well as the largest allowable box that AusPost will ship. Shipping from Oz to the USA using UPS or FedEx is much more, starting at $600 on up. Other dimensions are set by the 8-degree throat of the GPA/Altec drivers, along with the results of Bjorn Kolbrek's simulations and measurements.
In short, it is tightly optimized for a 1.4" large-format compression driver and a 700 Hz ~ 1 kHz crossover. The intended complement on the LF end is a 12~15" direct radiator or an AH-160 or AH-204 Azurahorn with 5~7" high-efficiency driver - Lowther, AER, Feastrex, or a professional midrange driver.
Three different audio-enthusiasts in the Denver area are using the larger Azurahorns with Lowthers and AERs, and they're getting very very good results with them. If I get results midway between Azurahorn/AERs and Altec 288's with 1505 multicells, I will be very pleased.
The dimensions of the AH-425 are bounded by the maximum length quoted by Newell and Holland, as well as the largest allowable box that AusPost will ship. Shipping from Oz to the USA using UPS or FedEx is much more, starting at $600 on up. Other dimensions are set by the 8-degree throat of the GPA/Altec drivers, along with the results of Bjorn Kolbrek's simulations and measurements.
In short, it is tightly optimized for a 1.4" large-format compression driver and a 700 Hz ~ 1 kHz crossover. The intended complement on the LF end is a 12~15" direct radiator or an AH-160 or AH-204 Azurahorn with 5~7" high-efficiency driver - Lowther, AER, Feastrex, or a professional midrange driver.
Three different audio-enthusiasts in the Denver area are using the larger Azurahorns with Lowthers and AERs, and they're getting very very good results with them. If I get results midway between Azurahorn/AERs and Altec 288's with 1505 multicells, I will be very pleased.
Lynn Olson said:
Hi Lynn,
The info on the Dipole15's can be found on the archive page here:
http://web.archive.org/web/20030214153145/lambdacoustics.com/drivers/DIPOLE15.html
Fs: 21.7hz
Qms: 15.2
Qes: 1.0
Qts: .94
Vas: 623L
Cms: /7mm/N
Mms: 90g
sd: 855cm2
Rms: .81Kg/S
Bl: 12.2Tm
Re: 12.3ohm
Z: 16ohm
Le: .15mH
Pe: 200w
no: .61%
1wSPL: 90.1dB
Xmax: 12mm
This drivers uses a 14mm long coil in a 38mm tall underhung gap. If you look at a BL curve, you have very good linearity all the way out to 12mm each direction and about 2mm more before you hit 70% of the rest BL value.
I'll be doing some experimenting soon with a pair of Dipole15 per side and our new 6.5" midrange. I'll be adding in the B&G Neo3 planar as the top end as it can also be used as a dipole when removing the cup.
We had a small price increase of $30 to all Lambda drivers in mid august. The 15's are now all $309. There is still a $50 per pair discount as caninus80 mentions.
John
Results of Bjorn Kolbreks' BEM simulations
Here are Bjorn Kolbrek's first BEM simulations for the AH-160 (T=0.8) Azurahorn, which took 14 hours of run time. Bjorn is currently working on more simulations of the other models, and has given me permission to re-post his data here at DIYAudio.
The first graph is the polar response of the AH-160 from 100 Hz to 3 kHz.
Here are Bjorn Kolbrek's first BEM simulations for the AH-160 (T=0.8) Azurahorn, which took 14 hours of run time. Bjorn is currently working on more simulations of the other models, and has given me permission to re-post his data here at DIYAudio.
The first graph is the polar response of the AH-160 from 100 Hz to 3 kHz.
Attachments
No, I don't. Bjorn Kolbrek is now working on the AH-425 with and without a model for the 288 throat profile, so I would guess the graphs AH-160 shown thus far are probably showing the response of the horn by itself.
Here's the model for the AH-160 throat impedance, showing the resistive and reactive terms.
Here's the model for the AH-160 throat impedance, showing the resistive and reactive terms.
