Now that the Dayton Air Motion Transformer (AMT) tweeters have been out for a while, has anyone listened to the various sub-$100 USD models and chosen a favorite?
Mini-8 $30 USD - crossed at 5K
AMT2-4 $70 USD - crossed at 3500
AMT3-4 $100 USD - crossed at 3K
Obviously the mini-8 is much lower priced than the others. Are the others worth the premium..... especially given they would all be padded down to around 87 dB in the crossover to a typical midwoofer.
Anyway, the good reviews on the treble of the B652-AIR have me wanting to go AMT for my next design.
Mini-8 $30 USD - crossed at 5K
AMT2-4 $70 USD - crossed at 3500
AMT3-4 $100 USD - crossed at 3K
Obviously the mini-8 is much lower priced than the others. Are the others worth the premium..... especially given they would all be padded down to around 87 dB in the crossover to a typical midwoofer.
Anyway, the good reviews on the treble of the B652-AIR have me wanting to go AMT for my next design.
Possible Alternative
I might suggest the Airborne RT-5002 ($72.40). I went through the same process that it appears that you are facing. I have it in an active system crossed at just under 4k and I am quite pleased with it. Here is the tweeter page link:
DIY Speaker Components | Replacement Speakers | and Speaker kits from Meniscus Audio Group
I might suggest the Airborne RT-5002 ($72.40). I went through the same process that it appears that you are facing. I have it in an active system crossed at just under 4k and I am quite pleased with it. Here is the tweeter page link:
DIY Speaker Components | Replacement Speakers | and Speaker kits from Meniscus Audio Group
Thanks Pallas. I found the thread over at Techtalk ( Linearity with level issues with AMT tweeters: just Goldenear or all of 'em ).
It was not clear if these issues affect the Dayton AMT's or not.
Also, no one mentioned any subjective sound quality impressions. Maybe no one has really bought and listened to these tweeters?
On the other hand, there are some very inexpensive drivers out there that measure perfectly or nearly perfectly but don't sound very musical....
I did find a few subjective comments that seem to be positive written by Arvind Kohli at tnt audio ( [Review] DIY supertweeters for Electrostat speakers ) He says that the mini-8 sounds pretty good if one can't do a dipole.
He is only using them as supertweeters though, I'd want them to go a bit lower possibly even though I'm using with a good full range driver so I can cross anywhere really.
I didn't think that was enough info so I came here and asked.
He is only using them as supertweeters though, I'd want them to go a bit lower possibly even though I'm using with a good full range driver so I can cross anywhere really.
I didn't think that was enough info so I came here and asked.
Actually that's a pretty good result with a grill cloth in place.
The real problem with AMT's is that most of the smaller ones have a very "fast"/"steep" acoustic high-pass behavior - which asks a lot from the mid. driver right below the AMT's passband. (..and at least objectively the Triton's do have problems with their mid.s.)
Also, as long as the production quality is good, they usually have low harmonic distortion. (..and I have no idea about the Dayton's, but I do believe that Parts Express has a replacement or refund process if the driver's are crap.)
Here is the Triton loudspeaker:
https://www.youtube.com/watch?v=5srJ3lVvvTA
-decent sound IMO, which is surprising considering that most of the upper freq. range isn't the AMT driver, but rather the 5 1/4" midranges (..and in a vertically compromised MTM configuration as well). The bass range is the problem with these speakers: suffering a typical (space/position compromised) emphasis.
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AMT3 (and 4):
AMT tweeters - explored by Critofur
-note the conditions for the tests.. they aren't standard (so take that into consideration).
IMO the 4 is worth the half again increase in price over the 3, its just got a LOT more lower freq. extension. (..and potentially an easier driver to crossover to.)
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Thanks Scott, yes I looked at the 4 but it has an open back which means a separate enclosure in a simple speaker cabinet (Yes I know about dipoles and how to build that but it is a lot more work).
Thus the 3 looked most interesteing I juust wonder if it is worth the price.
I'm using a Markaudio full range driver for midbass and it has great highs already on its own so it can be crossed anywhere to a tweeter or supertweeter as the case may be. Probably an unusual situation I suppose.
Also looking at Fountek NeoX 2.0 ribbons. No idea which (AMT or ribbon) is the better choice especially in a multi-listener situation off axis.
Thus the 3 looked most interesteing I juust wonder if it is worth the price.
I'm using a Markaudio full range driver for midbass and it has great highs already on its own so it can be crossed anywhere to a tweeter or supertweeter as the case may be. Probably an unusual situation I suppose.
Also looking at Fountek NeoX 2.0 ribbons. No idea which (AMT or ribbon) is the better choice especially in a multi-listener situation off axis.
It depends then on where and how you want to crossover the drivers.
Notably it depends on the polar behavior (dispersion) of you full range driver.
My guess is that without the extended lower freq. bandwidth of the large AMT that you should be using it more like a "blended" super tweeter - with a crossover above 10 kHz, but with a "shallow" (1st order) slope. (..to get a more uniform polar response.)
The Fountek is likely going to be easier because of it's extended lower freq. response. Its problem however is the distortion level as it nears its self resonance. (..with distortion levels that will be much higher as you start going below 3 kHz or so.) Basically it means a steeper higher pass filter the lower you want to go. Perhaps 4th order around 2.3 kHz and 2nd order around 3.5 kHz (as guesstimates). (..and it depends greatly on the off-axis behavior of your fullrange driver.)
Hint: For the Fountek I'd look to the design principals of the Elsinore loudspeaker with a 2nd order crossover (..though it will require some physical setback relative to the fullrange driver).
The Renegade Tweeter Theory
I have a spare pair of Markaudio Alpair 10.2 already, might as well use those. See attached datasheet. I thought they would be a pretty good match for most any tweeter/supertweeter and thought the AMT would be fun to try. Obviously I don't want them to sound "bad" however due to poor tweeter selection thus my solicitation of opinions. What is your opinion now that my specific midbass driver is known?
I'm "eyeballing" it, but maybe a .33 mH foil inductor in series with the Alpair? ..and perhaps a 2.7 uF cap in series with the AMT2-4??? (..this is factoring in the impedance of each driver and their response on-axis.) Assuming a vertically "flat" baffle, tweeter should be below the Alpair (and below the listener's vertical 0 degree axis). The Alpair should be centered on the listener's 0 degree vertical axis. This placement should get you closer to the physical offset required by the crossover (and fortunately the Alpair has a shallow depth cone).
It really needs to be properly modeled.
Done like this it should "fill-out" the off-axis response of the Alpair driver considerably and give you a more spacious and detailed sound. But it will also be a bit "brighter" as well. (..though freq. balance can be adjusted with a "sub" woofer that extends into the lower midrange - say 120 Hz.)
As for specifics on the Alpair - you've got it and you like it, no need to change that (no matter what I or others think).
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Thanks for all of your time Scott, that was a surprise that the tweeter would go under the fullranger, I've seen that arrangement before but these will probably be pretty low to the ground maybe on 12" stands so the tweeter would end up only 18" off of the floor so I did not think of that arrangement.
If anyone else has heard Dayton AMT2-4 or Airborne RT-4001 please pipe in with any subjective impressions or problems you may have had. Or, compare to Fountek NeoX 2.0 if you've heard both.
If anyone else has heard Dayton AMT2-4 or Airborne RT-4001 please pipe in with any subjective impressions or problems you may have had. Or, compare to Fountek NeoX 2.0 if you've heard both.
Yup, with this crossover and configuration (ie. MT or TM), there is polar tilt that shifts the tweeter's vertical axis upward by almost 15 degrees (..I think).
It's an elegant way to not only align the drivers, but also to have better integration at the crossover ABOVE the vertical listening axis - ie. being better at the standup/sitdown situation.
Rabbitz describes this here:
http://www.diyaudio.com/forums/multi-way/82428-time-allignment-serial-crossover.html
BTW, 18 inchs off of the floor seems low. Std. ear height sitting down is usually between 29 and 34 inches - which is where you would want the center of the dustcap of the Alpair. The driver's diameter is about 6 inches so you move down about 3 inches from that height. Even at only 29 inches then you'll have 26 inches for the bottom of the Alpair. The AMT2 is only about 3 inches with a center about 1.5 inches - so the AMT2's center should under this example be about 24-24.5" above the floor.
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Actually that's a pretty good result with a grill cloth in place.
What does the sock have to do with dynamic compression?
The real problem with that AMT is severe dynamic compression right where the ear is most sensitive.
The grill cloth will have a reaction with the driver's motion given the extremely low mass and the near lack of mechanical resistance.
The much more plausible explanation for the extreme dynamic compression is that the tweeter is simply a POS.
I think it's highly unlikely. It's not thermal compression, not enough power input for such a limited bandwidth (..see John K's research into this).
It's also highly unlikely to be mechanical compression given the multi-pleated design and the nearly non-existent excursion.
(..also in both cases you would expect a "jump" in harmonic distortion, that isn't present.. at least for the tweeter. Note: if the tweeter was a POS you'd see it in the non-linear effects at almost any intensity level.)
Rather the probable reason is a diffraction/reflection/diffusion effect.
(..I should note that I've seen this sort of thing from diffraction without a grill and normal tweeters as well.)
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I have a pair of RT-4001 and other than the rise above 10k they are nice. System is active (minidsp) which gives me plenty of room to tweak and are crossed at 2.2k. The rise in the top octave is not an issue. Distortion could be lower, but for the $80/ea price I couldn't be happier with the results.
Should also say the bezels have been removed and mounted them into a custom waveguide.
Also note the published specs are off a bit, for the good. Rated effeciency is 89dB, realworld effeciency (stock, w/bezel , flush mounted on appropriate baffle) is 94dB. This increase allowed me to redesign the system and go from a typical effeciency rating of 87 to 93 as it is today.
Should also say the bezels have been removed and mounted them into a custom waveguide.
Also note the published specs are off a bit, for the good. Rated effeciency is 89dB, realworld effeciency (stock, w/bezel , flush mounted on appropriate baffle) is 94dB. This increase allowed me to redesign the system and go from a typical effeciency rating of 87 to 93 as it is today.
I think it's highly unlikely. It's not thermal compression, not enough power input for such a limited bandwidth (..see John K's research into this).
It's also highly unlikely to be mechanical compression given the multi-pleated design and the nearly non-existent excursion.
(..also in both cases you would expect a "jump" in harmonic distortion, that isn't present.. at least for the tweeter. Note: if the tweeter was a POS you'd see it in the non-linear effects at almost any intensity level.)
Rather the probable reason is a diffraction/reflection/diffusion effect.
(..I should note that I've seen this sort of thing from diffraction without a grill and normal tweeters as well.)
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