not exactly a Heil or AMT but here are photos of the BG RD75 hornloaded which might be an inspiration for some:
Linearrayentwicklung - Fotos
Linearrayentwicklung - Fotos
A properly designed waveguide (not horn) changes the directivity and thus how the speaker reacts in a real room. It can limit early reflections but if improperly designed, cause them. Low reflections can improve imaging and the frequency linearity of the soundwaves that do reach your ears.
Hello Hum,
Your speakers look very, nice! However I have a couple questions for you;
- Why didn't you place the waveguide on the front completely or is it your intention to eventually do so?
- Why didn't you also place a waveguide or some other type of acoustical device so the ribbons feel the same acoustical impedance on their front & back, or this is a non-issue.
Thanks,
Thetubeguy1954
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Attn: Moderators, for my own knowledge was it the fact that I left out this message below the photos in my orginal post ( Uploaded with ImageShack.us ) from image shack the reason my two photo were later marked as 403 Forbidden?
I want to thank everyone here who has responded to my questions from the bottom of my heart ---{especially in these last 2-3 years}--- because it was the diyaudio.com forum that was and is, the reason I've learned so much about fullrange/wide-range drivers & front/back-loaded horns. This forum is the reason my audio system turned from being excellent to being wold-class! Thank you all very, very much...
Thetubeguy1954
thanks but i cannot take credit for anything , those are not mine.
i just saw them and thought the construction looks interesting and might be an inspiration on how to build a horn around a AMT.
Hello Badman,
What exactly are those 4 white pieces you've displayed? To me they look like they're parts of a back-loaded cornerhorns. Am I correct?
Thetubeguy1954
Tubeguy
Heya Tom:
They're just the rough-sanded and primer coated version of these (the profile has been flattened somewhat too)
Heya Tom:
They're just the rough-sanded and primer coated version of these (the profile has been flattened somewhat too)
http://www.diyaudio.com/forums/planars-exotics/2651-ess-amt-1-air-motion-transformers-12.html
I've posted this on the Geddes Waveguide thread and the thread linked above, but this subject probably deserves its own thread. The design started out with the MDF edgeround projecting into the throat, but the projection worked out to be greater than anticipated so was ground down. The gap between the assembly and the heil will be coupled with foam window gasketing to make the transition smooth but removable, and the triangular piece in contact with the AMT frame has bondo filling the gap to the rest of the horn flare. The expansion is straightwalled with a roundover to a short flat section then a round-back. According to the behavior of horns with compression drivers, and the simulations run by our own Mige0 here: Dipole Horn, Dipole Directivity Control Device
this should maintain CD exceedingly well. I'm undecided about whether to include the top section or not, it seems like it's unnecessary as there's already dipole cancellation and the directionality imposed by the 4" vertical dimension taking place. Perhaps just a soft absorber to dampen any reflections off the top edges of the MDF?
Let me know what you think!
Hello again Badman.
Let me know how they sound when you're done, ok? I have 3 pairs of the large Heils just sitting here...
Thetubeguy1954 (Tom Scata)
Aye-Aye chief. Now that I'm working on them again I'll probably get them tested sooner than later. It sure makes a large horn, the total assembly is something like 22" wide.
I can easily live with 22" wide my friend, so keep me informed as I'm very interested in your outcome...
Thetubeguy1954 (Tom Scata)
Hey Guys,
Thanks!
Here is the official thread highlighting our work on these Silver Iris Reference Ribbon drivers:
Hawthorne Audio • View topic - Silver Iris Reference Ribbon official thread
If you have any additional questions please feel free to contact me directly.
Thank you very much for your interest in our work.
Cheers,
Darrel 🙂
So, we have success, I plugged 'er in. It's loading cleanly to about 500Hz it seems, with a 24dB/Oct rolloff after that and has very good constant directivity behavior, in the horizontal. Vertical is a little rougher and the lows fall off faster- which is fine, it's acting as expected. I measured a very clean 120dB @ 500Hz (THD was 80dB down).
My wife called it "orgasmotasmotic". So I guess she likes it too.
My wife called it "orgasmotasmotic". So I guess she likes it too.
C'mon Badman, we all know how gullible audiophiles are as a group. IMHO we're all sort of like Fox Muller, in that even if it sounds too good to be true... We WANT to believe it's possible!
Thetubeguy1954 (Tom Scata)
Heil horn in test environment
picture's worth a thousand eh?
Just mocked up with a blocking cap... they're great tweeters but the XO needs work (duh)
picture's worth a thousand eh?
Just mocked up with a blocking cap... they're great tweeters but the XO needs work (duh)
An externally hosted image should be here but it was not working when we last tested it.
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I ran some pink noise through today. As predicted, it appears the hornloading is boosting the 1-3kHz range, which I'm knocking back down with a 10uF series cap. The crossover, naturally, could use some more refinement but it's measuring very flat with about an f3 of 1400, and consistent in terms of off-axis response. Really impressive but I should pin down the filters a little tighter.
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