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AcouPlex - Perplexed

sonddek said:
Audioworks also demonstrated the effect of adding supertweeters which kick in at 15kHz, well above what I hear in an ear test.
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Worth listening to the supertweeters alone without the speakers. Chances are you will hear them easily. I borrowed a very expensive pair of Tannoy supertweeters ages ago and they were easily audible even on their highest crossover frequency as the HPF crossover slope is so gradual. They have to be as the only people who could afford them are unlikely to be able to hear anything over about 10-12kHz!

I’m really not a fan; the effects are very audible, but can be fully explained by altered treble dispersion, adding time/phase error, comb-effects etc, or simply turning up the treble! This especially the case with Tannoys where the physical distance between the main DC driver centre and the supertweeter is anything up to a foot! Just moving your head up and down a cm or two totally alters the phase alignment. I really hated them, they ruined everything that is so right about a good point-source driver, though they do improve off-axis listening if that’s important to you. Definitely an effect IMHO.

PS I later played around at length with a pair of Decca Kelly ribbons and crossovers of my own and whilst I got results I felt were far better (a lot more subtle) than Tannoys’ own supertweeters the basic time/phase issues remained. Physics is gonna physics. It is what it is. The only place they can work IMO is in a design like a BC1 where the two tweeters are really close to one another and the crossover is specifically designed for that alignment. That said if folk like an effect then buy an effect.
 
Tony L said:
Worth listening to the supertweeters alone without the speakers. Chances are you will hear them easily. I borrowed a very expensive pair of Tannoy supertweeters ages ago and they were easily audible even on their highest crossover frequency as the HPF crossover slope is so gradual. They have to be as the only people who could afford them are unlikely to be able to hear anything over about 10-12kHz!

I’m really not a fan; the effects are very audible, but can be fully explained by altered treble dispersion, adding time/phase error, comb-effects etc, or simply turning up the treble! This especially the case with Tannoys where the physical distance between the main DC driver centre and the supertweeter is anything up to a foot! Just moving your head up and down a cm or two totally alters the phase alignment. I really hated them, they ruined everything that is so right about a good point-source driver, though they do improve off-axis listening if that’s important to you. Definitely an effect IMHO.
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The really clever thing about the Fyne Audio supertweeters (which is what were on dem at the show) is that these are omnidirectional, so there's much less of that beaming, or comb-effect that conventional supertweeters exhibit. Fyne has also produced a white paper explaining what's going on, and it's much more about reducing phase errors in the audible range (and improving transient response) than about extending the frequency envelope upwards.
 
Sue Pertwee-Tyr said:
The really clever thing about the Fyne Audio supertweeters (which is what were on dem at the show) is that these are omnidirectional, so there's much less of that beaming, or comb-effect that conventional supertweeters exhibit. Fyne has also produced a white paper explaining what's going on, and it's much more about reducing phase errors in the audible range (and improving transient response) than about extending the frequency envelope upwards.
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That will help hugely with dispersion, but it isn’t going to impact time/phase or comb effects as that is 100% down to the physical distance between drivers. The larger that distance the more phase/time-error and therefore comb effect in overlapping frequencies. It is just physics. The distance between two points. That isn’t to say folk won’t enjoy the effect.

Visualise lines from where the tweeter is in the speaker and where the supertweeter is to your ear, now move your head up or down an inch and picture what happens to that waveform. That is time/phase error. The way these (out of time) waves interact with each other causes cancellations and reinforcement, this is the comb effect.

I’m really not attempting to be judgemental; some folk just like this effect, which is absolutely fine, but I’m really sensitive to it. I hear it clearly and do not like it at all, which I’m sure is why I am drawn to point-source speakers such as Tannoys, ESL63s, tiny mini-monitors, or very large horn systems where the mid horn covers most of the frequency range. I really do not like drivers spaced out, let alone ones duplicating the same critical frequencies a distance apart.
 
Tony L said:
The only place they can work IMO is in a design like a BC1 where the two tweeters are really close to one another and the crossover is specifically designed for that alignment. That said if folk like an effect then buy an effect.
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Even with acoustic centre spacing as close as in the BC1, DM4, etc, there is still audible phase shift as you move your head up/or down. I understand why it was necessary in the 70s given the frequency response and power handling limitations of drive units of that era, but in a modern context crossing drivers over at such a high frequency is just a bad idea!

I'm curious, did you ever try your supertweeters firing upwards at the ceiling or backwards at the wall behind the speakers? This apparently delays the time arrival of the supertweeter's output enough to avoid phase cancellation with the main speakers output whilst still contributing spaciousness/ambience. I've never tried it myself but PS Audio use this configuration in their Aspen FR30 and Danny Richie views it as a far more effective implementation than aiming supertweeters directly at the listening position.

PS - Apologies for pulling the discussion even more off-topic!
 
ToTo Man said:
Even with acoustic centre spacing as close as in the BC1, DM4, etc, there is still audible phase shift as you move your head up/or down. I understand why it was necessary in the 70s given the frequency response and power handling limitations of drive units of that era, but in a modern context crossing drivers over at such a high frequency is just a bad idea!
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The advantage the original BC1 had was the natural roll-off of the main Celestion tweeter, IIRC that was out of the game around 14kHz. I very much doubt the many modern clones duplicate that. The BC1 is a lovely speaker IMO.

ToTo Man said:
I'm curious, did you ever try your supertweeters firing upwards at the ceiling or backwards at the wall behind the speakers?
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I did with my Decca Kelly ribbons, not with the Tannoy supertweeters. In may ways I preferred them firing backwards into the record shelving, they added a slight omni-directional illusion.

One thing to point out here is I am very much a hot-seat listener. I like that ‘studio control room’ perspective so the absurd phase and time-error of the supertweeters just ruined that. They lost that amazing coherence of the Tannoy drivers. My Tannoys are huge; 15” Monitor Golds in very large Lockwood studio cabs. As such the centres between the MG compression horn and the supertweeter centre was about 35cm, maybe more with the Deccas. I listen at a distance of around 2.1m, so somewhere between midfield and nearfield. The phase/time/comb effects were obvious and changed hugely with listening position. That said it sounded noticeably better off axis from the chair in the bay window well to the right of the right cab, so if off-axis listening in a large room is a factor I can see people liking them. Maybe switch them on for guests, off for serious listening. Absolutely not for me, though interesting and I learned some stuff! Having such an extreme example of phase/timing error to play with and explore helped me understand what I was hearing and what I instinctively don’t like about so many tall multi-driver speakers.
 
narabdela said:
Well respected?

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£1600?

Pull the other one.
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I bought all of mine second hand from people up grading .
Well respected , well yes . Certainly well thought of , often recommended and highly regarded. I attended a Naim open day last year , someone asked for a mains block recommendation . Jason Gould said he liked the Musicworks acrylic block .
 
ToTo Man said:
I'm curious, did you ever try your supertweeters firing upwards at the ceiling or backwards at the wall behind the speakers? This apparently delays the time arrival of the supertweeter's output enough to avoid phase cancellation with the main speakers output whilst still contributing spaciousness/ambience. I've never tried it myself but PS Audio use this configuration in their Aspen FR30 and Danny Richie views it as a far more effective implementation than aiming supertweeters directly at the listening position.
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Yes this is absolutely what I felt I found (note the carefully chosen words there) when I tried supertweeters with ESL63s. I had them firing away from the back wall.
 
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