Aluminium alloy domes usually have an advantage in sonics. I regard a decent Alu tweeter as the best tradeoff between accuracy and smoothness. It usually sounds better than titanium, which has a disadvantage in the upper mids from down- modulated HD components produced by the upper breakup mode.
Be sounds smoother than titanium and is only just a little more accurate than Aluminium (depending on the alloy). Be is quite a bit lighter and raises upper breakup (apples to apples). All of these are reasons why I prefer the M74A with the T34B. Its a more cohesive combo with the bigger metal domes. The T34A is too laid back for my tastes, but its likely a little lower HD in the upper mids, where most of the sonic character resides on larger HF domes.
The big Peerless Corundom dome is an odd bird. Its mainly an Alu substrate diaphragm and behaves like a different substance altogether. This tweeter is excellent and goes very low, but also has a very accurate top end... actually a bit too accurate which can sound dry to those who prefer other metal alloy domes.
The differences are minimal between the Be and Alu T34s, but the main area where there is a perceptive difference is in the upper midrange. Much of the raised 3rd order HD is in that range. The profile of the Alu diaphragm is taller than the Be. This has an effect on the dispersion and 1/4 WL standing wave between back chamber and tip of the diaphragm.
Most dome tweeters have a little raised odd order HD in this upper mid (5-6k - ish) area. The ones that have lower levels usually employ a fancier back chamber geometry and shallow dome profile. If you employ too much dampening media to minimize the issue, it excessively lowers Qts, reducing output just above Fs - there's a tradeoff between output and HD.
Take a look at the newer Seas Titan tweeters. You'll see the approach they took with the more contemporary toroidal back chamber design. The avoidance of sharp corners common with traditional ferrite motor drivers reduces standing wave modes without the need for media based absorption. It retains more low level detail and usually improves Qms, which is generally low in heavily dampened soft domes.
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@profiguy , have you measured the Harwood AM 25 or AUrum Cantus 2560 sibbling, please ? filtered at 3k, should have low THD enough from there, a lot of resolution, even better than the Be domes, but w/o any break ups ? I see the vertical patern as an advantage in the lower and lower ceilling heigth in EC.
@diyiggy No I haven't measured them but the Harwood is very similar (if not identical) to the Aurum Cantus 2560, which is the superior "budget" AMT. The Dayton HR4 has similar top end and worse lower mids. Above 4k its better though.
Most AMTs don't do well under 3k or so. There's too much odd order HD in that range, especially compared to a larger HF dome. I definitely prefer even the Peerless DA32TX to any budget AMT. The only better model AMTs are the large Mundorfs. The narrow vertical pattern can be advantageous with low ceilings, but the sonics of a larger dome overshadow the overall performance of a cheaper AMT. Some would disagree, but if you haven't heard a really "good" AMT, you wouldn't really know the differences. The only thing sonically overall better than both a AMT and a higher end large dome is a larger ribbon ie. the larger Raal 140-15D, which is quite an astonishing tweeter.
Most AMTs don't do well under 3k or so. There's too much odd order HD in that range, especially compared to a larger HF dome. I definitely prefer even the Peerless DA32TX to any budget AMT. The only better model AMTs are the large Mundorfs. The narrow vertical pattern can be advantageous with low ceilings, but the sonics of a larger dome overshadow the overall performance of a cheaper AMT. Some would disagree, but if you haven't heard a really "good" AMT, you wouldn't really know the differences. The only thing sonically overall better than both a AMT and a higher end large dome is a larger ribbon ie. the larger Raal 140-15D, which is quite an astonishing tweeter.
Don't forget about the Satori AT60NC. Very positively reviewed by hificompass
https://hificompass.com/en/reviews/satori-at60nc-4-amt-tweeter-review
"I would characterize the overall harmonic distortion level as “very low”, one of the lowest I've seen in tweeters."
yes that is the plan. it will be when we are close to releasing it to our web shop. we are currently working through a long wait list.
Well, my one data point is my PTT6.5M-04-NFA. It has the lowest harmonic distortion of any driver I own in the range from 200 Hz to 3 kHz, and very flat response. My test equipment is not state of the art, and the distortion from this driver is below my test capability. So I have confidence in Purifi... j.
Intereting that ferrite magnets are good enough for Purifi.
No need for neodymium or alnico quadramag..
No need for neodymium or alnico quadramag..
Yes agree. This is where my my partner Carsten Tinggaard comes into the picture with nearly 30 years of experience in driver design from Peerless, Scanspeak and VIFA including 10+ years as independent driver designer working for famous brands. Then adding my 35+ years experience in system modelling and analysis plus Brunos brains.
yes very true. luckily the wait is over
All our drivers have Neodymium magnets. Why would anyone use AlNiCo nowadays?
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That is for the inner magnet? The outside looks like classic ferrite?
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