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Dayton Esoteric AMT ES104AMT-4
A friend bought a pair and lent to me for testing.
TL;DR:
The bad - it's a mile away from the datasheet provided.
The good - it's a decent AMT that is very useful.
Mounted on a large scrap board, measured near enough to avoid diffraction effects, but far enough to capture high frequency response accurately.
The response is actually very similar to my AMT3-4, right down to the wiggle at 1.8-2kHz. The Esoteric does have a more extended response on both ends however versus the AM3-4, and is a bit smaller as well which will provide wider dispersion. While it is obviously not a "flat" response, the slope is fairly consistent which will make this driver still rather easy to work with.
For S&Gs, rigged up a rear chamber, however this provided a very minor response change.
(green trace is with the chamber)
Impedance plot shows the 1.8-2kHz resonances. Note the Y axis scale is super duper zoomed in to show the detail.
I ran a quick and dirty Step response as well for distortion, willy nilly at a reasonable volume about the level where I usually listen. Mostly 2nd order dominant which is great, not sure how much trust I would put into this as I rarely do distortion measurements and am still new to Steps.
As it is, I think this is a good AMT at a decent price. As of right now PE is still showing 220 in stock. If you were looking at the AMT3-4, this AMT is cheaper, will offer slightly improved dispersion and top end response, the ability to operate fully dipole if you remove the felt, and has a round face plate which is easily flush mounted with a circle jig.
Comments
Thanks for the measurements. I've been tempted by this. So far, I've resisted. We shall see.
Now I'm wondering how the older AMT1-4 measures in comparison. I too was considering a pair.
InDIYana Event Website
This is a measurement that Dennis Murphy sent me of the older one, AMT1-4:
My impedance measurements:
InDIYana Event Website
Not very similar, AMT1-4 drops like a stone below 2.5kHz.
AMT1-4 was a weird beast looking back. How did the same driver on two different data sheets got from this:
To this:
Somehow the frequency response took a big turn, lost a few dB of sensitivity and it gained a half ohm of impedance. I swear modern Dayton datasheets are useless, overly smoothed response doesn't show the true driver response and accuracy is very questionable. I guess that can be said for a lot of manufacturers though.
IMO the Dayton drivers have poor configuration control. While the data sheets have been reasonably accurate they change the manufacturer or build location then update the driver sheets without changing the model number. I have at least 2 versions of the ND90 drivers.
Seems like it's getting a bit better as we're seeing different model numbers more frequently on the RS paper series drivers.
I've determined that Dayton EMM-6 is not very good for distortion measurements. It measures abnormally high 2nd order harmonics, and slightly elevated 4th order too.
I've upgraded my mic to a Line Audio OM1 which is a real nice mic. If anyone is actually interested in this AMT, let me know and I'll redo a distortion measurement with the new OM1.