Pano, something else the autotransformer does is increase the damping factor to the driver. For a simplified explanation, see for example this white paper:
http://www.alkeng.com/dload/swamper.pdf
Frank,
Here is a set of plots from the 6 1/2" cone driver I am working on. This was done independently by a friend of mine and sorry for the poor quality of the scan. It shows how well the impedance and phase response with no correction is possible. The double trace is because this was a mass added test to determine Thiel Small values. This speaker has no impedance correction added to it, this is strictly the raw frame driver and the speaker was not broken in yet so the resonance frequency is actually lower than it appears here on the graph. Broken in it shifts down to about 35hz fs.
Here is a set of plots from the 6 1/2" cone driver I am working on. This was done independently by a friend of mine and sorry for the poor quality of the scan. It shows how well the impedance and phase response with no correction is possible. The double trace is because this was a mass added test to determine Thiel Small values. This speaker has no impedance correction added to it, this is strictly the raw frame driver and the speaker was not broken in yet so the resonance frequency is actually lower than it appears here on the graph. Broken in it shifts down to about 35hz fs.
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There are gradations to convincing sound - I have experienced moments, when all the stars are in alignment, when the sound steps up a number of notches again. My experience tells me there is almost no limit to how 'good it can get' - it comes down to how much effort and focus you want to put into optimising absolutely everything, eliminating every little defect which has an audible impact. I am 99.99% certain that it will never be achieved, at the moment, by simply purchasing the 'best of the best'. Having the equipment in your room for the first time, and hooking it up is merely the first step in a long process ...
Human voice is good assessment material - I have a Vanguard CD of Odetta at Carnegie Hall, would be a very poor recording by most people's estimation, the mastering level is very, very low - at full volume her voice is no louder than a normal TV, and often sounds like that's where it's coming from! This is a killer album for picking quality, her voice requires absolutely everything to be in place to sound 'live', to be a real human voice.
A system firing properly takes over not only the room, but the whole house - the latter becomes subservient to the sound of the recording, the music of the replay completely dominates the acoustic of wherever you are, within listening distance - in a positive, not negative sense.
I guess it depends on the response of the driver and how you want to shape it with the crossover. I'm also thinking that the autotransformer may lessen the need for the following zobel network, at least in some cases. I plan on running some simulations and listening tests (I just received some autoformers in the mail this week) to understand better what they do and how they sound.
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Indeed.
Also, different people are 'being convinced' differently, or by different aspects.
Yes, people 'tune' into different elements of the sound - impressive to one means nothing to the person next to him ...
Personally, it starts at 'invisible speakers': blindfold on, it's pin the tail on the donkey ... errr, the tweeter, time. If I can't locate where the high frequencies are coming from, even when my head is only inches away from the vibrating source then I'm in pretty good shape ...
Personally, it starts at 'invisible speakers': blindfold on, it's pin the tail on the donkey ... errr, the tweeter, time. If I can't locate where the high frequencies are coming from, even when my head is only inches away from the vibrating source then I'm in pretty good shape ...
I recall there was a system demoed somewhere that hid a person behind some curtains, they would sometime let the person play and sometimes let the audio system play. It was many years ago so I can't remember the details of the report. Technically, you cannot recreate the exact sound field as live performance, so when you challenge a listener to the test, there are always ways to detect a difference once you learn what to listen for. The closest we can get to realism is to record each instrument on a single tract individually, and then play back each track through it's own channel through careful placement of each speaker. Then you will feel that you are attending a live performance over the widest range of music possible.
Hello Boldname,
Many people use Le Cléac'h axisymetrical horns without tweeter, crossing the axis of the horns one or 2 feets ahead of the listener's head. (Even some of them said there is no problem with the width of the sweet spot...).
But if you don't cross the axis then you may perceive some lack in treble depending on the listening distance and interdistance between the left and right horns.
Few people that want to listen their loudspeakers from everywhere in the room complained of the increasing directivitythat lead to a reduced level of the treble out of the "sweet spot".
Then there is also many people that don't judge using their own audition but by their interpretation polar response and other graphs...
Best regards from Paris, France
Jean-Michel Le Cléac'h
Hello,
One main difference between a Le Cléac'h horn and waveguides is the smoothness of the pressure field it induced (perfectly shown in BEM simulation) and which is reflected, both in the smoothness of the response curves at any angle and by the smoothness of the polar curves at any frequency.
After Earl Geddes gave IR of both an OSWG without foam and an OSWG with the foam plug, it was clear (at least for me) that the interleaving of the responses curves from -30° to +30° were due to diffraction Inside the waveguide (and most probably at its throat which is the part at which the first and second derivative of the profile of the waveguide are maximum see : http://www.diyaudio.com/forums/attachment.php?postid=1789598&stamp=1238488590 ).
Best regards.
Jean-Michel Le Cléac'h
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I measured the polar response for the AH425 for this paper: Simulation of the acoustic field of a horn loudspeaker by the Boundary Element–Rayleigh Integral Method. Attached is the measured polar response and the simulation. The measurement data is exported from Arta so as to make the figures visually more similar for the paper, and since Arta only allows 1/3 octave data to be exported from the polar plot, it's somewhat coarse. But the AH425 has very smooth variations in polar response, so the differences would not be large in most of the frequency range.
What Lynn showed, is the near field pressure map. It is not a directivity map as such.
Regards,
Bjørn
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Just raise the Zobel roll off and limit with a higher res. I would keep it.
Jean-Michel. Thank you for this.
It could be that the Ariel with the latest i.e Be version of 745 could mearly be toed in sufficiently and thus perhaps avoid the ubiquitous RAAL Lazy ribbon without severe compromise. I do this with shallow wave guides with direct drivers to good effect. For professional constant directivity it may be different.
It is about time that someone pointed that out. But you should also point out that the polar plots for the OSWG and the AH425 do not use the same scale - one is in dB and one is linear. Why, if the AH425 is so great, is it necessary to cheat on the data when it is presented? I also assume that the OSWG has a sharp mouth edge, or some other feature that no one would actually do in practice because a good OSWG does not look like what you show.
1. If it was live vs. recorded and played back – and if it was previously recorded on the exact same location – such conditions are unavailable in commercial recordings (the very same acoustics in the recording facility and in the playback facility).
2. You didn't say if the recording was undistinguished from the live to all listeners.
Indeed.
This may be only one reason of why no reproduction system can possibly recreate the sound (and music) as in live concerts.
1. Possibly it is so, possibly not. I cannot know without hearing it.
2. AFAIK, not even the sound of single acoustic, unamplified, instrument can be recreated as to be undistinguished from live concert. Without having more details about the experiment you described above, we don't know if my statement was refuted. As long as even a single instrument cannot be reproduced with 100% fidelity, no number of microphones and no number of loudspeakers will change it.
3. Even with a microphone and a loudspeaker for each individual instrument, the acoustics of the recording facility cannot be reconstructed with 100% fidelity.
4. Even if such arrangement can recreate the sound with 100% fidelity, it's inapplicable for present day commercial recordings.
So, I come back to my statement, with a minor addition:
AFAIK, no reproduction system in the world, using available commercial recordings, can imitate 'the real thing' (live concert of unamplified acoustic instruments and human voices) in such a way that when all experienced listeners, when entering the room blindfolded, all of them would be sure that they attends an actual live concert. (All experienced listeners may refer to one at a time, or few at a time).
(I added to my statement 'all experienced listeners' because of possibly some experienced listeners will have the feeling of attending live concert, while others will not. As long as even one person can distinguish between a reproduction and live concert – the reproduction isn't a 100% reconstruction of the source).
Hello Earl
Thanks I was wondering what was up. I just didn't make any sense to me that those could be "right". I even posted David's 4430 measurements as an example of what a good CD device should look like as far as the polar response trying to get clarification. I didn't realize they were pressure maps.
I have a question as I am not familiar with that type of measurement. Looking at the pressure map on the AH425 can they be looked at as an inverse to the directivity?? Looks like they are related or is it just coincidental.
Rob
KEF with it's KM1 did this years ago (early 80's) with a low compromise 2 channel multi amped monitor and 30 IPS tape in front of 100 's of people in Chicago. I was there. Best direct radiator I've ever had the pleasure of "not" hearing.
