Useful graph, since 20% RH is pretty common here. It's not quite a desert, but the altitude wrings a lot of moisture out of the air. Swamp coolers actually work here, although I prefer air conditioning (which runs 3 to 4 months out of the year).
Listening distance is 11 feet in my home, so correcting for VHF air attenuation is pretty modest ... a dB at most.
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I think that we talked about altitude, years ago. From Stereophile magazine.
"As We See It"
Under Pressure: Loudspeakers at Altitude
By John Atkinson • Posted: Nov 13, 2005 • Published: May 13, 1990
"The large peak at 16kHz reported by Stereophile...was nowhere in evidence...The most probable explanation of this discrepancy is that the [Waveform supertweeter's] very light ribbon depends on the air load for damping, and that load is much smaller in the thin air up there at 7000' in Santa Fe than at altitudes where less lightheaded and scientifically more accountable reviewers dwell." Thus spake Peter Aczel (footnote 1), erstwhile loudspeaker designer and Editor/Publisher of the reincarnated The Audio Critic, a publication that advertises itself as having "unusual credibility among the top professionals in audio." more at...
Under Pressure: Loudspeakers at Altitude | Stereophile.com
"As We See It"
Under Pressure: Loudspeakers at Altitude
By John Atkinson • Posted: Nov 13, 2005 • Published: May 13, 1990
"The large peak at 16kHz reported by Stereophile...was nowhere in evidence...The most probable explanation of this discrepancy is that the [Waveform supertweeter's] very light ribbon depends on the air load for damping, and that load is much smaller in the thin air up there at 7000' in Santa Fe than at altitudes where less lightheaded and scientifically more accountable reviewers dwell." Thus spake Peter Aczel (footnote 1), erstwhile loudspeaker designer and Editor/Publisher of the reincarnated The Audio Critic, a publication that advertises itself as having "unusual credibility among the top professionals in audio." more at...
Under Pressure: Loudspeakers at Altitude | Stereophile.com
Okay, finally got some good weather here, and the time to take advantage of it.
I should have known...as soon as everything was in place -- at last! -- the neighbor started mowing his lawn. He finished, I took some measurements, then of course the weed whacker started up.
Eventually I got a chance to do some work. As I suspected, there was an issue in the crossover region. I was able to improve it, but there is further to go. Unfortunately, that means I'll need to drag all this stuff outside yet again...sigh.
Gary Dahl
I should have known...as soon as everything was in place -- at last! -- the neighbor started mowing his lawn. He finished, I took some measurements, then of course the weed whacker started up.
Eventually I got a chance to do some work. As I suspected, there was an issue in the crossover region. I was able to improve it, but there is further to go. Unfortunately, that means I'll need to drag all this stuff outside yet again...sigh.
Gary Dahl
Okay, finally got some good weather here, and the time to take advantage of it.
I should have known...as soon as everything was in place -- at last! -- the neighbor started mowing his lawn. He finished, I took some measurements, then of course the weed whacker started up.
Eventually I got a chance to do some work. As I suspected, there was an issue in the crossover region. I was able to improve it, but there is further to go. Unfortunately, that means I'll need to drag all this stuff outside yet again...sigh.
Gary Dahl
Hi Gary,
I can think of far worse ways to spend a rare, precious Pacific Northwest Sunny Day than working on your speakers...You know, like mowing your lawn or weed-whacking around the edges!
Best Regards,
Terry
Thanks Henry! My wife gets credit for the garden.
I had the mic lined up in various ways during the session. Some measurements were taken on axis with each driver separately, but the picture above was taken with the mic midway between the horn and the 416, which represents ear level in my listening room.
Gary Dahl
I had the mic lined up in various ways during the session. Some measurements were taken on axis with each driver separately, but the picture above was taken with the mic midway between the horn and the 416, which represents ear level in my listening room.
Gary Dahl
Hi Gary,Okay, finally got some good weather here, and the time to take advantage of it.
I should have known...as soon as everything was in place -- at last! -- the neighbor started mowing his lawn. He finished, I took some measurements, then of course the weed whacker started up.
Eventually I got a chance to do some work. As I suspected, there was an issue in the crossover region. I was able to improve it, but there is further to go. Unfortunately, that means I'll need to drag all this stuff outside yet again...sigh.
Gary Dahl
That is the time to use TDS.
It is fairly immune to other sounds.
Oh yes, have some side/rear firing Ciare tweeters i can switch in and out in my system. It's a love hate thing.
I sometimes run Circle Surround encoding with 2 channel where the front side/rear firing tweeters are driven by a separate amp out of the decoder's front channels along with my omni horns above and behind me. It can be remarkable with big hall/live recordings. The rear near field sub is delayed too so the size of the hall is felt too.
Personally I find Spotify bland. If the sytem cannot distinguish between Spotify and a better source then whatAll the music on Spotify is listening to opamps
I did consider using an aperiodic vent, but my interest waned when I heard the combination of the sealed 416's and the Amity amplifiers. Perhaps it would be a different matter if I were using SET amps. The PP 300B's don't have any trouble controlling the woofers.
It is probably worth trying anyway, but I must admit that it's hard to get motivated to cut holes in these cabinets.
Gary Dahl
It is probably worth trying anyway, but I must admit that it's hard to get motivated to cut holes in these cabinets.
Gary Dahl
I disagree, although it wouldn't take very much to convince me to your way of thinking.
The hardest part is "Un-Cutting" the holes later on if you find it to be unsatisfactory!
OK seriously.......how about a removable panel on the back that could be changed out if you deside to go back to sealed.
BTW: Make your own vents with Hardware Cloth (Screendoor screen) folded over like a PeeChee folder and a few layers of Mr. Coffee filters in between (adding or subtracting filters to suite) then using duct tape to hold your "sandwich" in place. Actually, it could be "spruced up" later to look nice.
Best Regards,
Terry
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A sliding type vent could be made that is totally sealed off when fully closed, and when opened provides various room tuning's depending on how wide the vent is opened etc. It could also be loaded to work as aperiodic or BR etc..
On a different note I wonder how this would work with the 416 instead of the compression driver proposed here?
Hawthorne Audio - 700 Hz. AMT drivers
On a different note I wonder how this would work with the 416 instead of the compression driver proposed here?
Hawthorne Audio - 700 Hz. AMT drivers
Hmm, I wonder how well the AMT's work down to 700 Hz. The AH425 Azurahorns are 420mm/16.5" in diameter, and maintain diaphragm loading down to 500 Hz or so. Based on the pictures, the Hawthorn Audio AMT's seem quite a bit smaller than that.
But ... AMT's would probably make excellent supertweeters to supplement the horn above 7 kHz, with much better headroom, and more extended response, than most supertweeters.
Gary Dahl brings up a good point. Although the nominal efficiency is set by the 97 dB/meter woofer, the speaker is probably not a good match for really low-powered amplifiers in the 71A, 45 or 2A3 SET class (although PP 2A3 or EL84 would probably be fine). These are 15" woofers with 70-gram cones, after all, and the back-EMF currents could probably capsize the modest power supplies of amplifiers in this class.
My version of this speaker will either use a 515 combined with a 416 or a pair of 416's (already ordered from Great Plains Audio). Efficiency and headroom will be higher, but back-EMF currents will still be substantial compared to the usual horn-loaded Lowther or AER.
The obvious setup is bi-amplification with PP 300B, EL34, or KT88 for the bass section, and 71A, 45, or PX4 SET for the HF section. That way IM distortion from the bass amplifiers never gets to the compression driver and horn, and the SET amplifiers operate at a very low level, with DC polarization of the output transformers linearizing them in the milliwatt region.
But ... AMT's would probably make excellent supertweeters to supplement the horn above 7 kHz, with much better headroom, and more extended response, than most supertweeters.
Gary Dahl brings up a good point. Although the nominal efficiency is set by the 97 dB/meter woofer, the speaker is probably not a good match for really low-powered amplifiers in the 71A, 45 or 2A3 SET class (although PP 2A3 or EL84 would probably be fine). These are 15" woofers with 70-gram cones, after all, and the back-EMF currents could probably capsize the modest power supplies of amplifiers in this class.
My version of this speaker will either use a 515 combined with a 416 or a pair of 416's (already ordered from Great Plains Audio). Efficiency and headroom will be higher, but back-EMF currents will still be substantial compared to the usual horn-loaded Lowther or AER.
The obvious setup is bi-amplification with PP 300B, EL34, or KT88 for the bass section, and 71A, 45, or PX4 SET for the HF section. That way IM distortion from the bass amplifiers never gets to the compression driver and horn, and the SET amplifiers operate at a very low level, with DC polarization of the output transformers linearizing them in the milliwatt region.
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