Speaker shootout update; aggressive treble eliminating some (fairly?)
@hilde45, @jtcf Well, yes it does on the KT150s with a spread of 15ma, and not as noticeable a change with only at 5ma spread. You’d need a multi-meter to use with pin jacks for manual setting. I see pin jacks on the Mid Monos, not on the Mono 60s. For Mono 60s you could set LED to go out and compare that to when it’s super bright. Best to check with Mike Sanders on that. |
@helomec @helomec, did you audition the older "XT" or latest "XTi" version? Updates for the XTI version mention no tweeter or crossover changes, but I’m suspect. The woofer surrounds in the new XTi version are noted as upgraded and "stiffer". I’ve heard the older 60XT many times, and own the smaller ML40XT for another setup, and they are not overly bright, fairly neutral in fact. As noted before, found a spike on the response graph between 10k-15khz. Still kinda wondering if there was a change in material used in the AMT diaphragm or crossover with the new XTI version...no proof, just curious. |
@helomec, I auditioned the older XTs. I noticed the spike in the measurements of one online review, but a spike in that octave is most likely to result in a sense of "air" and atmosphere, not brightness. I do wonder if these AMT drivers might require a break-in period where the binding/matrix material has to undergo micro-cracking, thereby allowing the pleat to relax, not unlike a conventional spider material. Not all AMTs are created equal that's for sure. The ML AMTs are far superior to those used by Golden Ear. |
@helomech The original Dr. Von Heil AMTs did mellow out some over time, and it was the crossovers/caps settling too, not just the diaphragms. I worked on the assembly line at ESS early 1980s, where it was all invented. Seen some variations since the patent expired on the AMT. My own ML XT40s did settle some over time for my HT setup. Smoother now for sure. I agree all AMTs are not created equal. My own current custom speakers with great heil amt units sound smoother with larger presentation than all mentioned here so far. Over time, messing around, learned it really comes down to a very high quality crossover and corresponding drivers to get the right tone and staging one might be looking for. One thing for sure, when you get the right AMT speaker setup paired with really good tube amps, with really good tubes, its very enjoyable to listen to. :) |
One possible source of aggressive treble is poor amp/speaker matching, but this is not something which is obvious to most people. One would think good amp + good speaker = good results, but not necessarily. If I understand correctly, the amplifier is a transformer-coupled tube amp. This kind of amp tends to deliver approximately the same amount of power into a fairly wide range of impedances. On the other hand a solid state amp delivers increased wattage into an impedance dip, and decreased wattage into an impedance dip. Let’s walk through an example: So suppose we have an 8 ohm speaker with a 16-ohm impedance peak at 4 kHz. With a solid state amp, when the amp is delivering 1 watt into the 8 ohm nominal impedance, it is delivering 1/2 watt into that 16 ohm impedance peak. The designer probably assumed that a solid state amp would be used, so this speaker’s output is "flat" (or whatever the designer intended) with the amp delivering 1/2 watt into that 16 ohm peak. Now let’s use a tube amp. The tube amp delivers approximately the same amount of power into that 16 ohm peak as into the nominal 8 ohm impedance. So at 4 kHz, the speaker is getting 1 watt rather than the 1/2 watt the designer intended. So we have a 3 dB peak at 4 kHz. That’s enough to transform "smooth treble" into "aggressive treble". Rather than ditching your imo very nice Quicksilver amp(s), you might want to consider speaker compatibility with tubes. I can go into a bit more detail about it if you'd like. Here is a paper written by a tube amp designer which goes into this from his perspective, mine being the perspective of a speaker designer: http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html Best of luck in your quest, wherever it takes you. Duke |
