ESS AMT-1 vs Dayton AMTPRO-4 vs GRS PT6816 - any thoughts?

Joined 2008
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After building a large Synergy horn prototype with a 1.4" driver, the next one will be AMT/Planar based. I have a pair of the ESS AMTs, also a pair of GRS planars - but I wonder if it was worth trying the Dayton AMTPRO-4, too.

I really like the ESS AMT, but it is really a pain to mount a horn to it. The GRS planar is not bad at all, but lacks a bit sensitivity compared to the ESS. The AMTPRO-4 could most probably be easily fitted to the same horn as the GRS with a different adapter, since the dimensions are quite similar.

Have you ever compared/tested the AMTPRO-4 to any of the other two units?
I've built some Unity horns with ribbons and planars, but getting them to work is a bit nightmarish:

It's too bad you're halfway around the world, I still have the 3D prints in my garage and it would be nice to send them to someone who'd use them.

Here's the issues I ran into:

1) Even 15cm long planars struggle to play down to 2khz. Their lack of output from 500Hz to 2khz makes them really difficult to crossover in a Unity horn, since most midranges in a Unity horn run out of output at about 900hz - 1500hz.

2) If you use EQ to bring up the low end on the planar, you wind up with very low sensitivity and low power handling

3) Due to the large size of the diaphragm, it's hard to get the midranges close enough to the tweeter.

It's a bummer that they have these issues, because the sensitivity of planars is very high above 2khz. On Monday I ran a quick distortion test of my Airborne planars versus a SB26ADC dome tweeter, and the planar was nearly ten dB more sensitive!

One solution that I haven't tried, but might be worth a look, is a vertical array of at least three planars. This would bring up the low end of the planars quite a bit. For instance, with a 15cm tall planar, you're not going to see any "gain" above 2267Hz, because they produce a flat wavefront and one planar basically doesn't "see" the other planar above 2267Hz. But BELOW 2267Hz, the radiation becomes spherical (because the wavefronts are bigger than the planar) and that means you'd get constructive interference below 2267Hz. Which would negate a lot of the low frequency rolloff that's an issue with planars.

The end result would look a lot like a Danley Jericho Horn.
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Joined 2008
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The GRS works pretty fine even as single (, the ESS works fine, too (, it would be my first option if it was easier to mount to a horn.

The first post was more about if it would be worth to get the AMTPRO-4 as well to try - it would be super easy to mount.

I found out that the GRS PT2522 would fit my test horn with some minor adjustment, so I ordered a pair.

To use two or three 20 cm planars (GRS PT6816) sounds interesting - definitely worth building some cheap test horn.

But I definitely must take the built stuff out, measure, fine-tune DSP and listen if using the ESS AMT is worth the trouble with mounting or if I keep it for another project.

look forward to see what you come up with.

Was just looking at PT6816.
using maybe a basic rectangle tractrix.

they all have available faceplates which should make life easy.

depends on how low you want to go.
2522 holds 95 dB very well 4K and up.

anything lower would go down to the 6816.
Joined 2008
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The winged AMTs are definitely nice. But my goal here is to integrate it with mids and bass in a MEH. I am addicted to the effortless midbass of a large front horn, and I really liked my smaller 2 way MEHs for coherence. The ultimate goal for me is both in one box. The plan is to test the smaller planar when it arrives. If it gets me closer to what I want, I will have to figure out a way to make a build with the large AMT.


Joined 2003
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I got myself a pair of Dayton AMT4 pro a couple of years ago - cant say I tried every possible way with it but I did never like it. Used it open back and with EQ.... It sounded "closed in" and a bit harsh over the whole band.... as I recall it.

I have also AMT4PRO, open back, heavily EQ-ed with DSP and playing up from 1 kHz. I had not compared it to ESS AMT-1 or GRS PT6816 but compared it to Fontek NeoCD3.5H. CD3.5H have more easy, open sound and with better FR, but somehow AMT4PRO can be integrated better with mids, probably because lower HP filter, for sound it is beneficial when ears most sensitive range is reproduced by only one speaker element. AMT4PRO allow to use more power and give higher SPL level.
From internet can be find very good AMT4PRO measurements, but mine are not so good. AMT4PRO had different modifications, with different FR and THD, also different production lots can have different FR and THD, it is some kind of gambling.