I've been messing with a strain of the recent surge in Chinese air motion transformers. If you search for AMTs in Google or on eBay and see the ones with the yellow rectangular mounting flange on them, that's the ones. 6.5 ohm, 12wRMS, 1" ribbon. I got 3 pair for $39 per pair. I'd replaced the tweeters in a pair of Wharfedale Valdus 500s and got $400 for them from a very satisfied buyer. So I decided to make myself a minimal 2 way bookshelf set to see what I could get out of them.
I started with a pair of 9"H x 5.5"W x 5"D Sony speakers. The drivers were junk but the box was thick and reinforced. I put in Pyramid 2 way xovers rated at 100wRMS. For woofers I picked up a pair of the Boston Acoustics built 5.5" originally installed in the Hosa Cue-5 recording monitors from Dalaudio. Original specs said 30 wRMS but Dalaudio and I both f elt they could handle a lot more. And of course the AMTs tacked in over the tweeter hole. All 18g wiring inside, all connections soldered. Double thick felt feet for isolation, and the box packed with my stuffing of choice, pillow/comforter polyester fill. Both drivers were mounted with gasket tape on back.
All put together they look a little awkward. The woofer is as wide as the box (thank goodness for 6 hole mounting) and the AMT had to stick up about half an inch so as not to overlap the woofer. First test revealed some leaks, so I filled the original cover screen mounting holes (the extraneous screws near the top) and packed some more speaker gasket tape around the AMT flange.
Second test was more successful. I used an Audiosource AMP100 (no tone controls, just volume and balance) with various FLAC audio files I keep around for such things, and used my laptop as the source. 1kHz/1w/1m test was 96dB. Everything else was tested with the amp running flat out, 65 wRMS. First music test was a piece that went over well with the Wharfedales, Mannhiem Steamroller's Toccata in G from Fresh Aire 4. In that test the clarity and stereo imaging were like nothing I've ever heard before from that recording. In these little 2 ways, the bass was not up to the Wharfedales', but was excellent none the less. But it was in the high end where these really shined. From 12 feet away, between the speakers 12 feet apart, I could tell the difference in direction between the snare drum and cymbals -- about 10 degrees (a fist at arm's length, an old star gazer's trick). The maracas sounded like the real thing.
I through all sorts of stuff at it and the speakers took it all well. Satriani, Hagar, Oldfield, Vangelis, it all sounded great and had a presence I've heard from only a few set ups. The only thing that seemed to overdrive the woofers was a DVD file of the sixth cut from Yanni At The Acropolis. The drums and bass were jamming, and the greater output of the DVD audio seemed to make them buzz a bit.
The only problem I have with these AMTs is the mounting flange. It's way too flimsy and cracks easily if you try to mount them any way except with a hole cut specifically for them. Wasn't an option with these boxes, but it will be with the next version of the test build.
I started with a pair of 9"H x 5.5"W x 5"D Sony speakers. The drivers were junk but the box was thick and reinforced. I put in Pyramid 2 way xovers rated at 100wRMS. For woofers I picked up a pair of the Boston Acoustics built 5.5" originally installed in the Hosa Cue-5 recording monitors from Dalaudio. Original specs said 30 wRMS but Dalaudio and I both f elt they could handle a lot more. And of course the AMTs tacked in over the tweeter hole. All 18g wiring inside, all connections soldered. Double thick felt feet for isolation, and the box packed with my stuffing of choice, pillow/comforter polyester fill. Both drivers were mounted with gasket tape on back.
All put together they look a little awkward. The woofer is as wide as the box (thank goodness for 6 hole mounting) and the AMT had to stick up about half an inch so as not to overlap the woofer. First test revealed some leaks, so I filled the original cover screen mounting holes (the extraneous screws near the top) and packed some more speaker gasket tape around the AMT flange.
Second test was more successful. I used an Audiosource AMP100 (no tone controls, just volume and balance) with various FLAC audio files I keep around for such things, and used my laptop as the source. 1kHz/1w/1m test was 96dB. Everything else was tested with the amp running flat out, 65 wRMS. First music test was a piece that went over well with the Wharfedales, Mannhiem Steamroller's Toccata in G from Fresh Aire 4. In that test the clarity and stereo imaging were like nothing I've ever heard before from that recording. In these little 2 ways, the bass was not up to the Wharfedales', but was excellent none the less. But it was in the high end where these really shined. From 12 feet away, between the speakers 12 feet apart, I could tell the difference in direction between the snare drum and cymbals -- about 10 degrees (a fist at arm's length, an old star gazer's trick). The maracas sounded like the real thing.
I through all sorts of stuff at it and the speakers took it all well. Satriani, Hagar, Oldfield, Vangelis, it all sounded great and had a presence I've heard from only a few set ups. The only thing that seemed to overdrive the woofers was a DVD file of the sixth cut from Yanni At The Acropolis. The drums and bass were jamming, and the greater output of the DVD audio seemed to make them buzz a bit.
The only problem I have with these AMTs is the mounting flange. It's way too flimsy and cracks easily if you try to mount them any way except with a hole cut specifically for them. Wasn't an option with these boxes, but it will be with the next version of the test build.
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Can you post a close up of the tweeter and post a link to ebay ... at firs look it does not seem to be an AMT unit ....
Looks like a planar (isodynamic), but can still sound super of course 🙂
39 usd per pair, also sounds way to little for a pair of AMTs.
Can you actually see that the diaphragm is pleated?
/Baldin
Looks like a planar (isodynamic), but can still sound super of course 🙂
39 usd per pair, also sounds way to little for a pair of AMTs.
Can you actually see that the diaphragm is pleated?
/Baldin
Looks to be a single-ended planar ribbon, right?
Air Motion Transformer Ribbon Neodymium Belt Tweeter 25W 6 5OHMS x 2pcs | eBay
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Looks pleated to me. Sorry, my camera can't do as good as the stock pictures posted. Hard to see and image with that aluminum grill work over it. If you search for "Plat Audio RT4-A" you'll find some references to German and French eBay postings, and can translate as needed. One offered a pair for 25 Euros (= USD 33.87 currently). You'll also find it on Aliexpress for $18 each. The Plat isodynamic ribbon tweeter is model RT4-DPI. They're listed at $81 a pair. I'd sacrifice one for the cause if they weren't all planned into projects. If I can get one apart and back together, I'll do it.
If it is the ones bolserst are refering to, which seems right, it is definitely not AMT!
These are planar no doubt.
Best regards Baldin
These are planar no doubt.
Best regards Baldin
Banana planar 😉
I enjoy my BG Neo3 planars and am also a huge AMT fan. Hopefully your tweeters will please!
I enjoy my BG Neo3 planars and am also a huge AMT fan. Hopefully your tweeters will please!
The ones he referred to are in fact the same ones, and the same seller. Should anyone else wish to try some, he accepts an offer of $40 for the first pair to someone. And they do in fact please. Regardless of accuracy of description, the test results remain. I've not heard high end come across so clearly unless it was also louder, such as with piezos. In fact I did compare them to piezos in a recent test. I tried them both in a set of stage monitors with a Kustom 12" and Fender 12". Both instrument speakers nearly over powered the t. weeters (sensitivity 98 dB and 104 dB respectively). The piezos had more output. They were the better choice for this because they needed to be heard well and fairly clearly, but not hifi quality clearly. Tests will continue. The intended end result is a compact, full range WTW center channel/bookshelf stereo speaker. If these do the job I'll stick with them, though I'm a little perturbed at the false advertising.
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