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Multi-Way Conventional loudspeakers with crossovers

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Old 27th June 2008, 11:00 AM   #4111
Rudolf is offline Rudolf  Germany
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Quote:
Originally posted by LineSource
...Playing with the EDGE baffle simulator see if floor effects are properly modeled by mirroring the design..does this look correct??
You are talking about floor effects (plural).
What you are simulating now is "floor gain" exclusively. The other important effect is "floor bounce". To simulate that properly you need to put the mic higher (as CJS already stated) and look for the applicable mic distance.
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Old 27th June 2008, 09:51 PM   #4112
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Try different distances, ranging from 2 to 5 to 100 meters, to get a feel for the power radiated into the room.

What makes estimation of bass difficult is the perceptual model for the ear shifts from dominance of the direct-arrival sound (above 300 Hz) to perception of the overall power in the room (below 300 Hz). This is why it is an industry convention to "splice" the frequency response at 300 Hz, using direct-arrival MLS/FFT measurements above 300 Hz, and near-field measurements below that.

Nearfield measurements are simple for a closed-box loudspeaker (put the microphone about 1" away from the cone). Nearfield measurements for vented, TQWP, and transmission-line systems require the additional step of ratioing the area of the vent to the area of the speaker-driver. As far as I know, nearfield measurements do not give valid results for dipoles and quasi-cardioids (dipoles with acoustic fill in the rear), since the interaction with the room is so complex and unpredictable - it's no longer a simple matter of total power radiated into the room, as it is with a monopole loudspeaker.

Given the challenges with measurements, that makes it difficult to accurately simulate what the in-room results at the listening position will be. The Edge simulator assumes free space - literally, a loudspeaker baffle and microphone hanging in mid-air, far above the ground. By mirror-imaging the virtual loudspeaker below the real loudspeaker, you are moving Edge to the ground - say, a flat expanse of concrete, extending hundreds of meters in all directions.

What remains unsimulated is the listening room, which most certainly will affect bass below 300 Hz. (There will be more bass than the free-field condition - the question is, how flat and how much.) Perceptually, the direct-arrival wave starts to merge with all of the many reflections arriving from the room boundaries - walls, ceiling, and floor. Since the wavelengths are long, the phases of the individual reflections has a direct result on how they will sum at the listening position - that is, you have add the power of each reflection vectorially, not just the power sum (which is more appropriate at higher frequencies, where the phases of the reflections are randomized).

Absorption by carpeting is well under 1 dB at low frequencies, so all surfaces can be assumed to be rigid - with the following restriction: in wood-framed houses in the USA, Canada, and other parts of the world, the flexure of the wood framing results in bass losses due to sound going right through the wall. This happens mainly below 50 Hz, and is the reason your neighbors may hear more deep bass than you do. Large glass surfaces also leak bass at low frequencies. Openings into other rooms - doorways, hallways, open-plan architecture - all make the model even more complex - in the limit case, you might have to model the entire house. Gary Pimm, for example, found (by measurement) that the LF limit of his cardioid-bass system was determined not by the size of his living room, but by the dimensions of his house.
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Old 29th June 2008, 12:50 AM   #4113
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Default Off Topic...but maybe not.

All,

I visited the West Coast Shindo dealer yesterday and was able to hear a full Shindo system including the Latour speaker. It uses a field coil version of a vintage Altec 288, a field coil version of a vintage Altec 515, and a modern interpretation of a Westrex 80/20.

I have heard a many hifi systems over the past decade or so and relatively few if any music reproduction systems. Yesterday I heard the finest music reproduction system I have ever heard. The qualifiers being the following:

After a few notes I stopped listening for the audiophile stuff like imaging, soundstaging, detail, extension, resolution, colorations, etc...and was simply drawn into the the performance in an engaged emotional experience. This is something that has never happened outside of live performance. That being said, all of the audiophile stuff was there and none of it drew attention to itself screaming "This is memorex."

Since this thread has run the gamut on material covered, I felt it was as good a place as any to pass along my thoughts,

Chris
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Old 29th June 2008, 01:04 AM   #4114
SunRa is offline SunRa  Romania
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Quote:
I visited the West Coast Shindo dealer yesterday and was able to hear a full Shindo system including the Latour speaker. It uses a field coil version of a vintage Altec 288, a field coil version of a vintage Altec 515, and a modern interpretation of a Westrex 80/20.

Where could one find a field coil version of the Altec 515?
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Old 29th June 2008, 01:07 AM   #4115
agent.5 is offline agent.5  United States
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Default Re: Off Topic...but maybe not.

Quote:
Originally posted by chrismercurio
I visited the West Coast Shindo dealer yesterday and was able to hear a full Shindo system including the Latour speaker.

Did you ask if that is a mltl or bass reflex enclosure? Come to think of it, the guy is here in San Francisco. Maybe I should drop by.
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Old 29th June 2008, 01:13 AM   #4116
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It is vented. There were several slot shaped ports on the bottom. I don't think it is traditional BR loading or even TL....more like the kind of alignments that were done before Theil and Small made things easier. At that time, people experimented, listened, and figured out what worked. I think it is probably something more like that.
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Old 29th June 2008, 01:15 AM   #4117
agent.5 is offline agent.5  United States
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Quote:
Originally posted by SunRa



Where could one find a field coil version of the Altec 515?
I kind of hoping that Nick is going to make one, a better one even.
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Old 29th June 2008, 05:22 AM   #4118
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Default you can't find one

Shindo takes vintage Altec's and converts them into field coils. I am not certain what is involved beyond requiring a power supply and removing the magnet. Perhaps someone else can chime in? Please keep in mind that the above is most likely a GROSS OVERSIMPLIFICATION.

Chris
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Old 29th June 2008, 06:39 AM   #4119
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Default Re: Off Topic...but maybe not.

Quote:
Originally posted by chrismercurio
All,

I visited the West Coast Shindo dealer yesterday and was able to hear a full Shindo system including the Latour speaker. It uses a field coil version of a vintage Altec 288, a field coil version of a vintage Altec 515, and a modern interpretation of a Westrex 80/20.

I have heard a many hifi systems over the past decade or so and relatively few if any music reproduction systems. Yesterday I heard the finest music reproduction system I have ever heard. The qualifiers being the following:

After a few notes I stopped listening for the audiophile stuff like imaging, soundstaging, detail, extension, resolution, colorations, etc...and was simply drawn into the the performance in an engaged emotional experience. This is something that has never happened outside of live performance. That being said, all of the audiophile stuff was there and none of it drew attention to itself screaming "This is memorex."

Since this thread has run the gamut on material covered, I felt it was as good a place as any to pass along my thoughts,

Chris
I am not so surprised. There have been times when large-format, Alnico-magnet Altec speakers have sounded - for lack of a better word - "magical". It's not really magic, of course, but subtle aspects of the Western Electric engineering approach that persisted in the Altec organization. Not all aspects of driver construction are written down in spec sheets.

I find it significant that Altec engineers resisted strong corporate and THX movie-industry pressure to change over to higher-power titanium diaphragm drivers, on the grounds that titanium just didn't sound as good. A decade later, with Altec no longer around, JBL quietly admits that aluminum sounds better - after the rest of the prosound industry has converted over to titanium. By then, of course, beryllium was the New New Thing, so everyone started chasing the latest wonder material. Hmm ...

Reminds me a bit of the huge PR campaign in the early Eighties to promote 44.1/16 PCM Compact Discs as "Perfect Sound Forever". A few people still buy into the propaganda that 44.1/16 sampling represent the limits of human hearing. But - when the Red Book patents for the Compact Disc expired (and not before), what was waiting in the wings?

You guessed it - higher-rate PCM with much greater bit depth (more resolution). That would make 96/24 and 192/24 "Better than Perfect Sound for Longer than Forever". The really interesting thing is that BtPSfLtF sounds like - analog mastertapes!!!
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Old 29th June 2008, 06:53 AM   #4120
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Default Re: Re: Off Topic...but maybe not.

Quote:
Originally posted by Lynn Olson

Reminds me a bit of the big PR campaign to promote 44.1/16 PCM Compact Discs as "Perfect Sound Forever". When the Red Book patents expired (and not before), what was waiting in the wings? You guessed it - higher-rate PCM with much greater bit depth (more resolution). So that would make 96/24 and 192/24 "More Perfect Sound for Longer than Forever".
I still like records. It doesn't matter if it is a Shindo'd 301 or a Technics 1200.

Chris
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