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Old 30th September 2008, 09:44 PM   #21
GM is offline GM  United States
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I use SnagIt 5.0 to capture the active window and save it as a gif in a folder, then use the forum's upload feature to post it, but this requires a separate post for each 'capture', so some folks make a collage of the various captures:

GM
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Old 30th September 2008, 09:46 PM   #22
Elbert is offline Elbert  Norway
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Ah, snagit.. sounds like a screen-capturing coftware that would be handy...

Anyway.. just printed the curve.. and scanning it as I write, hehe!!

Should get something any minute now..
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Old 30th September 2008, 09:57 PM   #23
Elbert is offline Elbert  Norway
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Default JBL simulation

OK, here's the simulation with the JBL 2202..

The original measurement is soon to follow!
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Old 30th September 2008, 10:03 PM   #24
Elbert is offline Elbert  Norway
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Default And finally

Here's the measurements as taken at the horn mouth on the prototype back in 1978..

Would be very interesting to get some comments on how you think the modeled response and the measured response compare!


If this validates the model to the point where it can actually prove useful for evaluating modern day driver candidates, that would be just great!
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Old 30th September 2008, 10:32 PM   #25
Elbert is offline Elbert  Norway
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Shouldn't I go to bed so I can get up and go to work tomorrow??

All geared up now...

Just did some quick simulations with both the Eminence kappa 12 and the Pioneer woofer (mentioned earlier). Efficiency seems pretty similar, but the pioneer woofer actually seems to give a smoother response!

The only drawback I can find with the pioneer is that at 20V input, its on the limit of its 2,5mm Xmax, but heck.. thats at allmost 130 dB output!!!

Yes, that's what the SPL plot tells me, 130 db... DOWN TO 40 Hz!! can this really be true??

I have to build one of these babys.. and if the landlord complains, I can just turn up the volume.. until he melts, AHAHAH!!
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Old 1st October 2008, 06:25 PM   #26
GM is offline GM  United States
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Default Re: And finally

Quote:
Originally posted by Elbert

If this validates the model.......
It doesn't for me. Since HR sometimes seems to over emphasize 'ripple' I loaded it into MJK's old FLH designer which tends to show a better damped response, but it simmed 'close enough' to convince me we're missing a major 'something' based on the actual measurement:

GM
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Old 1st October 2008, 07:34 PM   #27
Elbert is offline Elbert  Norway
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Hi GM!

Hmm... yes.. this looks a bit different again... hard to say if its just a measurement technicality or some fundamental discrepancy with the model..

Volume-wise, the model also seems quite close to the original design..

Problem is that I've got no more data left to extract from the original design for further model input...

But, if we take the "worst case" and assume that the model is at best an approximation of the actual horn.. could it still be used as a "test-bench" for evaluating drivers?

In other words, would a driver showing good response in the model also be likely to work well in the real horn?
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Old 1st October 2008, 08:28 PM   #28
GM is offline GM  United States
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Greets!

If you're satisfied that you've calculated throat/mouth area and path-length ~accurately, then yes, a good 1pi sim in HR will in theory perform OK backed up against a wall and ~equidistant from two corners. You'll probably need the other pieces shown on either side to extend the mouth to get the smoothest response down low though.

GM
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Old 1st October 2008, 08:51 PM   #29
Elbert is offline Elbert  Norway
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Well GM, I guess my dimensions are off by some cm here and there, but measuring on the assembly drawings and scaling up, its the best i can do for now!

But then again, if I change the horn lenght, say +/-5 cm, I don't expect that to have any radical impact on the outcome.

The horn is designed to stand against a wall, so that's where it will eventually go if it gets buildt.

Been doing some simulations with various drivers now, and I'm seeing some very interresting things.. (possibly) When simulating with some hi-fi drivers with low Fs lower BL and Higher moving mass than typical pro drivers like the Kappa 12, the response smoothens out significantly. The drawback seems to be larger cone excursion at low frequency, just like the lower BL force and higher Mms reduces membrane controll..

Then I found that by reducing the closed chamber from 80L down to 30L, the frequency plot became virtually flat from 45-to 120 Hz! This allso, served to limit maximum cone excursion to within acceptable limits.

(I intend to use the horn up to no more than 150 Hz)

I got very nice results simulating with a Peerless SLS 315 12" woofer:

http://www.mamut.net/dynabel/subdet329.htm

But this sort of goes against the grain where High BL/ Low Qts pro-like drivers are supposedly the ideal choice for horn applications ... ?

I have read that the driver Fs should be lower than the cut-off of the horn. Could this explain something as the HI-fi drivers had Fs in the 20 Hz range?

The Kappa 12 driver has an Fs of 37 (which is stil quite low for a 12" pro driver i believe) which is of course above the Horn Frequency of 30 Hz..

Could this explain something?
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Old 3rd October 2008, 08:05 PM   #30
Elbert is offline Elbert  Norway
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Ok,

Time to get some images up here, this is all getting a bit to abstract without something to look at!

Have scanned the construction drawings from the original magazines.
Resolution is a bit poor due to file size restriction, but if anybody would like the the full quality scans, just let me know and I'll @-mail them!
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