You appear unfamiliar with much of my work. If you had a look around you'd realise I've used well controlled high directivity loudspeakers in my home system for more than 20 years. It's a feature of almost every system I design. I've been doing significant design work for an up and coming boutique manufacturer for the last few years and every model is a high directivity design to minimise room interaction in real rooms. I do understand the principles.
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The distortion measurements are not usually at 1 watt. Depending on the driver impedance, it usually ends up being closer to 10watts since the baseline is around 95 dB, and it ends up being approx 105 dB/1m equivalent. I say equivalent because I do very close microphone placement to pick up driver response more so than room reflections in the distortion measurements. To me, close microphone placement is about 3" from the diaphragm itself. At that distance it is already max'ing out the Dayton Omnimic with around 125 dB of SPL. That's kinda how I prefer taking HD measurements.
The black FR measurement is a 30cm measurement, as noted.
Well that only makes less sense that you'd try and argue that a highly directional driver system won't work in a studio setting. Everyone knows that you can learn to work on just about any system, and all systems have advantages and disadvantages, choose your poison.
Yes. Terrible. Distortion and polars are both rubbish.
William; don't waste your time any further.
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We are looking at the Aurum Cantus selection currently. Have you experienced this driver in its lower register?
Yes William, walk away.
It's all about control of that off axis power. A speaker that is perfectly omni at all frequencies will sound very good in a decent room. Same for a speaker with perfect hemispherical radiation. A speaker that is radiating all frequencies evenly into a 60 degree cylinder or cone will also sound good in a decent room. It's the speaker that abruptly transitions into different radiating angles that will sound poor in a room and only sound good on axis in a very acoustically absorbent space. You must look at the total radiated power as well as the on axis frequency response. If both those are on target the loudspeaker has the potential to sound good in a decent room. Many loudspeakers are flat on axis but very lumpy off axis because of poorly managed off axis pattern control.
Understanding of the total power response from a loudspeaker is key.
I agree with everything you just said. Not really sure why the discord. Like I said in my first post on the topic "good designs don't have coloration added to the off axis response" which you reiterated here "Many loudspeakers are flat on axis but very lumpy off axis". Maybe I misunderstood Josephs post but I took it as him saying that a AMT would not work as a studio monitor based on it not having wide dispersion. From what I've seen, AMT's don't generally have "lumpy" off axis responses. so what was he actually implying since no where did anyone even bring up off axis character until he posted?
ps - Brett is trolling me from another post where he completely derailed my thread and I called him out on it. Just a little back story before he gets his momentum built.
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How did you go about attaching the driver?
As other's have said, don't do it. THD is near 12% @ 700Hz.
If you really need good sub-1kHz performance, I honestly think your best bet is Aurum Cantus AST25120's or AST30130's loaded into a large horn with a tight throat aperture matching. It's on my to-do list for Summer '19.
A horn that I have been testing/modifying is the Dayton H110 horn. Even though it is for 1" compression drivers, if you slice of the rear of the horn it leaves a rectangular throat that has very similar dimensions to rectangular AMT's. You can see it (on the floor) attached (rudimentary fit) to the H110 horn.
Gain over stock Hygeia RT-5002.
Interestingly, the Aurum Cantus units perform better that the larger Dayton AMTPRO-4, even with smaller diaphragms. Equally as interesting, I've noticed that the shape of the FR curve changes as you increase drive level. Here is one comparison for the AST30130, low & high level (not 1m though, I think this was more like 30cm or so)
Different test ( I don't remember what changed in this before-and-after test)
While the HD of the Aurum Cantus isn't as low as the Beyma, it is actually very well "controlled", if that makes any sense.
Are you asking about the Hygeia RT-5002 AMT with the large Dayton horn/waveguide?
Did you see his results with the Aurum Cantus custom fitted to a horn!? The distortion was fine all the way down to 700hz. Decay is another story but it looked promising for a 2 way crossed at 700ish 48db octave.
In fact, the graph I have looks like someone from Beyma snuck into my lab, and put the plot from their datasheet into my measurement system! The flatness in the passband is incredible, then the response falls off the face of the earth...
700Hz is going to create excursion, power handling and issues around correction for the rolloff unless you do something very sneaky!
700Hz is going to create excursion, power handling and issues around correction for the rolloff unless you do something very sneaky!
Oh, I haven't done that. The picture I showed is the Hygeia unit. The Aurum Cantus units are too tall to modify a single horn, IMO. You'd have to splice two horns together to get the necessary height.
When you start being picky you just have to step out of regular everything and start trying things yourself. I like the immersive live sound I get from horns, and that is why I got something like the Radian 950 (Yamaha Ja6681B) in a big *** JMLC-IWATA-220Hz horn and a Raal, in a rather large horn, trying to catch up already at 2kHz, instead of the recommended 3kHz. I will not recommend this to anyone else, but to me it sounds pretty okay. My next experiment will be to put another Yamaha midrange driver in a smaller horn from 1-3kHz and relax the Raal from its burdens.
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