audio-talk

Romy had a method of using normal electrolytics in this context, I may be able to find the link. He had an aversion to using big film caps beyond 100uF.
Be interesting to hear where you get to, bit surprised after the work you put in with these horns - but it's hard to get integration to a midrange cone in these situations.
I have not given up on horns. I have a new investigation for lower mids and upper bass. I gave a big clue but nobody commented on it !

I have been after a pair of these drivers for about 6 years. So when the opportunity arose I could not say no. My midrange horns are sounding so good currently integrating well. The whole setup is sounding great with my new anaview amps. So these new AMT’s they 200hz to 10k hz. How well they work I will see when I measure them. If I get to 3k I will be happy. I do have some plans to put them in some dipole horns as they are meant for OB. I won’t be bringing them to Owston this year. Would need warning signs as the magnets are dangerous on them, I would be collecting loose change from peoples pockets as they walked by.
Will look on Romys site. I was looking at rodenstein gold bullets... back in the 90’s they were raved about at the chesterfield HIFI shows. (so were wondercaps and how ify they turned out to be)

If you needed a big cap just to try out I think I have some 200u metallised film things in the the shed you could borrow to try out. They wouldn't be your final choice as they're not that great but can't remember what they are.

Cheers,
Stephen

I'm looking forwards to hearing about these new AMTs Steve..? I've used large motor run caps with some success a few years ago, but not as big as you need..
You could always try crossing an octive higher if your bass drivers will cope of course ?

Tested one driver today, with about half the capacitance so crossing a 400hz. It’s interesting quite a flat phase response until it fades away at 10k. I will post some measurements tomorrow.

Did a quick frequency sweep and FFT for the driver in a simple open baffle. My measurements aren’t that dissimilar to the manufacturers measurements, except I don’t seem to get all the phase looping above 3k. The dip (wobble around 1.5k) I think is room interactions, or baffle wrap around ( I know I should have offset it). Interestedly at 30 degs off axis it’s response is flatter. Next steps are to build a CD wave guide, inspired by the giant ones done for the Heils. ( sound practices. 90’s). Only going to build some simple Yuchi style ones (flat sides) with polystyrene and cardboard Hope I can route then in quickly, was going to use oasis, but it’s expensive for a 600mm wide block.

After some designing I came up with a SEOS horn for the AMT driver, it’s a small horn compared to my previous ones Only 70cm wide. I had to resurrect my maths knowledge which I haven’t used for 25 + years, understanding clothoids as well as super-ellipses. Measured the response today.... to be honest doesn’t sound that different to the driver mounted in an OB. It does however have quite a good off axis measurements having no drop off at 45 degs upto 8k. The wave guide is doing what it should. The trace shows the horn v OB version, in both cases it needs a bit of levelling in the DSP. I don’t know what to do next, do I make another and try them in place of the JBL 2482’s and TPL’s.... I have some little Mundorf AMT’s I can cross at 7K to give a little top end sparkle ( I won’t be able to appreciate the response upto 35K )

Blue trace is OB, red in SEOS. 3db intervals.

Another beautiful example of your fabrication skills.

You know when form follows function and a thing of beauty is created. That's it there. Wow!

Nice work. How deep is it though ?
Can you explain the curves a bit ?
What's the target operating band of the AMT ?

They are 300mm deep.
The curves are a comparison of the OB with the wave guided version, the red one is the wave guided, getting some dB gain upto 1000 hz or so. The real benefit is in directionality.
It’s a pain to share traces as the pc with the measurements software hasn’t a WiFi card that works so photos on the ipad.

The drivers have a resonance <100 hz, so cannot go lower currently... think it’s something to do with how the membrane is supported, to not in this case. If someone had some 150mm kapton pcb tape. I reckon I could replicate these membranes as it strangely has the same profile as some heat sink profiles I have.

Target freq range would be 350hz upto 8K or so. Would have liked to get down to 250hz, as that’s around the room directionality frequency.

Some critical listening this weekend with Dave - my critical listener. The AMT drivers in his opinion show promise, especially in the female voice and brass trumpet when compared with the resident horns, Dave calls them my MJL’s (Mick Jaggers Lips). We came to the conclusion I need to build another one before we can truly say if their better or not. After Dave had left I added the Mundorf tweeter AMT’s into the equation crossing around 8K, surprisingly it seemed to improve the bottom end as well as adding a bit of top end air - a definite improvement.

So more machining of another wave guide/ horn is planned now..... Do I integrate the tweeter in of have separate is the next question.

wow!!
awesome

A couple of things popped into my head.

On the steampunk train of thought I thought the tweeter would look good in the middle of the mouth on a spider. Not sure how that would affect the arrival timing though.

Also you mentioned the magnets in the amt being fierce. Would they likely influence the tweeter?

what are the amt drivers? I have to say I was intrigued because I love amts but my experience has been disappointing because they've never covered the range I am neurotic about. These seem to cover that very range

Not sure a dipole tweeter will work in the middle of the horn, as the back wave would mix with the front wave from the midrange AMT.
The drivers currently are far enough part not to influence each other’s magnetic field.

The drivers are BEL AMT E500 mid range drivers, made by Berndt Lohan. They were around about 7- 10 years back but he’s obviously moved onto other things, I have tried contacting him for spare diaphragms, with no joy.