Telstar, with pleasure.
When the circumpherence of a piston is equal in size to one wavelength of sound, it enters the piston band, and for frequencies above, the radiation pattern begins to narrow or beam. The mechanisme behind this is that sound waves emanating from opposite sides of the driver start to interfere at a certain angle off axis.
With a d'Appolito setup, this beaming is assymetrical. Beaming will start on the vertical axis well before it starts in the horizontal plane. When you do the calculations for two 5" midwoofers, you will find that you need to cross over unrealistically low in order to prevent excessive beaming on the vertical axis.
This is the first reason why in my experience only small d'Appolito's work.
The second has to do with lobing as a result of the xover between mid and tweeter. The larger the acoustic distance between the two drivers, the narrower the central lobe becomes. This compounds the problem of beaming as mentioned before. Again a reason to keep it small.
The advantages can be twofold. The first one is that two coincident sound sources add up to +6dB, whereas the electrical energy put into it only doubles. 3dB of efficiency gain for the cost of one extra driver. This directly translates into less distortion. The second is that the vertical beaming can be put to some use, if controlled.
The speaker I am developing now has a d'Appolito mid/high consisting of one 3/4" and two 2.5" drivers. Best one yet.
When the circumpherence of a piston is equal in size to one wavelength of sound, it enters the piston band, and for frequencies above, the radiation pattern begins to narrow or beam. The mechanisme behind this is that sound waves emanating from opposite sides of the driver start to interfere at a certain angle off axis.
With a d'Appolito setup, this beaming is assymetrical. Beaming will start on the vertical axis well before it starts in the horizontal plane. When you do the calculations for two 5" midwoofers, you will find that you need to cross over unrealistically low in order to prevent excessive beaming on the vertical axis.
This is the first reason why in my experience only small d'Appolito's work.
The second has to do with lobing as a result of the xover between mid and tweeter. The larger the acoustic distance between the two drivers, the narrower the central lobe becomes. This compounds the problem of beaming as mentioned before. Again a reason to keep it small.
The advantages can be twofold. The first one is that two coincident sound sources add up to +6dB, whereas the electrical energy put into it only doubles. 3dB of efficiency gain for the cost of one extra driver. This directly translates into less distortion. The second is that the vertical beaming can be put to some use, if controlled.
The speaker I am developing now has a d'Appolito mid/high consisting of one 3/4" and two 2.5" drivers. Best one yet.
I heard the Cabasse Sphere last year. It was loud and generally annoying the several times I heard over 2 days. It imaged in a rather interesting coherent manner, but it lacked finesse and detail.
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What's left out there is how the noise floor is changing dynamically with output signal level. This needs to be tested with a high crest factor signal like music (a multitone [N > 100] signal would do it) - the measurement can't be carried out with averaging. Noise floor modulation affects, inter alia, perception of dynamics of an amp.
)I too can name many stuff that are not present in the datasheet - that does not make the included measurements irrelevant for audio performance and surely does not give any basis to call this amp "horrible" and whatnot.
Not only there is no solid technical merit to do such a thing (excluding "opinions" of designers or hobbyists like "more distortion sounds better") but also, if anything, the very positive subjective evaluations reported for the amp (yes, including "perception of dynamics"), indicate otherwise.
Btw the included measurements are way more - and better - than those you get with the vast majority of audiophile product (if you are lucky enough to get any).
It's funny how preconceptions about what sounds "good" (or doesn't sound good in this case - i.e. Class D amps) can make objectivists ignore measurements they would otherwise adore and subjectivists expose the full extend of their narrow-mindedness when keeping an open mind is what they preach.
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My response was by no means intended to endorse the comment that its 'horrible' - far from it.
Not denying many very happy (even delighted) customers. But I've read reports that it doesn't blow away the better analog (ooops, sorry terminological error - 'non-switching') amps, contrary to what's being suggested on the first page of the datasheet you linked 😀
Yes, agree.
People have been blowing their own horn for *really* horrible products, so I'd let this one pass. 😀
A designer can be proud of his work and I believe Putzeys has a lot to be proud of. I wouldn't go as far as to declare NCores will "blow away the best of non-switching amps" simply because I didn't have the chance to compare the former to all the members of the (vague) group of the latter, objectively or even subjectively.
Anyway, the datasheet is a good opportunity as any for the designer to demonstrate his perspective/frame of thought as an engineer - which is not uncommon, e.g. Nelson Pass typically does the same thing in his articles - and is probably welcomed by the fans. 😉
From an engineering perspective, seconded without any doubt. From a marketing perspective the jury's still out - let's see how Mola Mola gets on... 😛
Good post Shaman syntekne
I trust Pavel will present us his chip amps dragons and class D demons , mostly these that are relevant to audio performance.
If not, I would say he drifts toward the “all you amateurs out there” mode.
George
PS. Shaman, who is this Andrew Jones at your signature? Did he provide adequate evidence for the quote? 😀
George - its this one - andrew jones
As for Mola-Mola - here : http://www.audiophilejournal.com/mola-mola-hypex-class-d-amplifier/
As for Mola-Mola - here : http://www.audiophilejournal.com/mola-mola-hypex-class-d-amplifier/
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Marketing perspective eh? You are asking for trouble!
Who might Mola Mola be?
George
Never hear them. But i'm surprised by your comments, i remember Cabasse produced *very good* Hifi enclosures in the 80s.
As they are equalized by an active filter, something was tuned in a bad way ?
What was the problem, lack of dynamic ?
Anyway, i was not referring to them for their sound, but the innovation's attempts. At least several things are perfect on an acoustical point of view: Spherical enclosure, coaxial drivers.
This is an other way to explain what i said, i agree on all. With a detail, acoustic level at xover will not add 6db at high frequencies, but only ~3db.
I insisted several time, here, about the importance for the two speakers of the two ways, at the Xover, to have the same radiating diameter. Reason why i prefer horns.
The try of a more WAF enclosure for Aeria sytems:
MHP (la Maison du Haut-Parleur) : concepteur français de kits d'enceintes pour la HI-FI et le Home Cinéma...
finished in my home that way despite all the expected advantage of smaller diameter bass drivers (Upper cutoff frequency)
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Hi George,
This is the 2-part interview of Andrew Jones (Director and Chief Engineer of TAD Laboratories) I got the quote from:
Andrew Jones of Technical Audio Devices - Part one
Andrew Jones of Technical Audio Devices - Part two
Very interesting read IMHO. Has a lot of info about his life/career as well.
He's not a mathematician. 😉
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Interesting interview, this guy is clever, not pedant and sympathetic. 🙂
At the end, i wonder why designing for audio is so painful, with traps on every way you walk in.
Where each new track you can imagine to get rid of an inconvenience brings this own lot of negative effects.
At the end, i wonder why designing for audio is so painful, with traps on every way you walk in.
Where each new track you can imagine to get rid of an inconvenience brings this own lot of negative effects.
There is hope in this life.
Engineers (these lowest level creatures) can have humour!
Shaman, thank you for the links. He is very good.
Excellent read.
Quite many points in there, have been addressed by Esperado and kgrlee here.
George
>Edit. Can anyone link to these papers of the "multi-source Uni-Q experiment" at KEF?
Engineers (these lowest level creatures) can have humour!
Shaman, thank you for the links. He is very good.
Excellent read.
Quite many points in there, have been addressed by Esperado and kgrlee here.
George
>Edit. Can anyone link to these papers of the "multi-source Uni-Q experiment" at KEF?
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