A government big enough to give you everything you want is big enought to take away everything from you
... but sometimes you can really get into it.
"Make it sound like dinosaurs eating cars"
- Nick Lowe, while producing Elvis Costello
I couldn't resist posting some pictures of my current favourite horns (well, technically waveguides actually).
I just finished building these last week, and on the whole, I'm really pleased with the results of these Oblate Spheroid waveguides, which were designed according to Earl Geddes papers.
I set the angular coverage to be +/- 40degrees., and my initial frequency response measurement of spl response vs. polar angle for the waveguide on the JBL2441 (2" exit compression driver), track 0-40 degrees from 1khz to 10khz, within +/- 1.5db (diverging above 10khz, where the diaphragm break-up starts). Beyond 40degrees (40-75deg) the amplitude drops off like a rock.
The frequency response measurement of spl response vs. angle of the waveguide on the TAD2002 (1" exit compression driver) track 0-40degrees from 1khz to 20khz, within +/- 2db (no evidence of any diaphragm break-up). Beyond 40degrees (40-75deg) the response also drops rapidly.
The waveguides have decent impulse and the waterfall plots also look respectable. The waveguide mouth termination (acoustic impedance matching) is also not too bad, with only a modest amount of ripple (+/- 2db on the 2", and +/- 1db on the 1") visible on the linear scale cumulative spectral decay plots.
The 1" exit waveguide expansion curve is a stock Oblate spheroid shape, with a 1/2 round radius at the 8" diameter mouth.
The 2" exit waveguide is a compound shape, starting with oblate spheroid from mouth continuing to 3/4 of horn length, where it merges (seamlessly) into a tractrix taper for the last 1/4 of the waveguide, to the mouth, finishing in a 1/4 round radius curve to the outside edge.
The sound is very natural, and well recorded live instruments sound convincingly very real.
Well, they sure look gorgeous - great work, Jack!
2ch - Oppo981, JoLida502, AA DDE3 DAC, VonS VR4, Vandy 3A, 2Ce
HT7- XDA-2, BDP93, B&K amps, 2pr UREI 809A, TF600 & JBL 4641
Are you going to post your graphs? I'd sure love to see them.
I knew the guy who owned those big blue rear horns, they sounded kind'a bad, WAY too much midrange and weak bass. I heard them with various Fostex drivers and perhaps Lowthers, I'm not sure about the Lowthers.
What can I say??? (... my maid died???)
4530 Scoops/J-bins on the bottom with 2215A's in 'em. They go down OK with a bit of coaxing from a Phase Linear 700.
The 4301BE's are mint and self powered and sound a treat for late night easy listening.
L40's powered with a B&O 7700 which also run a pair of B&O S802's. (Amazing how similar to JBL's they sound.)
There's also a 2345 Horn with a 2420 added on top now, powered by a Crown D75 via a Crown VFX2A but this is an old photo, and last but not least, a pair of 077 Slots on top.
Mix'n'match at will.
You're lucky you can't see the other side of the room!!!
Listening distance, 3 metres.
Ya, you never know when something will come in handy.
And when you do, you won't be able to find it!Originally Posted by speakerdave
... too true.Originally Posted by norealtalent
I've spent the last week looking for a set of 3 x 2308 lenses that are hidden underneath it all somewhere!!!
My set of 846u speakers. 811B horns with 416 woofers.
Originally Posted by Woofer
I have a feeling your maid is in that room somewhere but she can't find her way out!
You have done some really fine work! I am impressed both by your logical approach to the design and the excellent execution of the many fine details; DIY at its best; you are a true craftsman.
You might consider posting some pictures of your project over on the Audio Asylum High Efficiency Speakers Forum. There have been several threads on the oblate spheroid waveguide there in the past, and Dr. Geddes has participated in these. You might want to do a search there for Dr. Geddes' past posts, as he has gone into considerable detail in explaining these waveguides.
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