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 Post subject: Re: First tube amp
PostPosted: February 9th, 2015, 9:43 am 
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Joined: July 3rd, 2014, 7:47 am
Posts: 89
Is there a reason that very efficient speakers most often employ the use of horns? Is it just not possible to do it another way with more conventional style drivers?


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 Post subject: Re: First tube amp
PostPosted: February 9th, 2015, 10:00 am 
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Joined: January 14th, 2015, 11:15 pm
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Line arrays are a possibility. Here is a link to an example.

http://www.diyaudio.com/forums/full-range/242171-making-two-towers-25-driver-full-range-line-array.html

Like most speakers they have a weakness, in this case, lobing issues.

ray


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 Post subject: Re: First tube amp
PostPosted: February 9th, 2015, 10:24 am 
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Posts: 1780
ratbagp wrote:
Line arrays are a possibility. Here is a link to an example.

http://www.diyaudio.com/forums/full-range/242171-making-two-towers-25-driver-full-range-line-array.html

Like most speakers they have a weakness, in this case, lobing issues.

ray

Lobing issues are only a problem where the physical size of the drivers used are large in relation to the wavelength being reproduced. That is why line arrays using conventional round tweeters have problems because the very high frequencies have wavelengths shorter than the size of the tweeter. Cancellations and reinforcements then occur at specific points. True line arrays such as the 75" tall BG RD75s are continuous so that lobing does not occur. I use a mid bass array of 6 - 10" dipole mounted drivers in a line array and run it from 90 to 300 Hz. At those frequencies, the wavelengths are long enough that no lobing occurs with the driver geometry used. The CBT array used by Don Keele is another example of a line array using separate dynamic drivers that does not have lobing problems. BTW, the photo on the site at the link below is a very old photo of Don. He is on very smart cookie and in addition to a lot of patents he has a technical Oscar for his work in movie sound.

Tom

http://www.xlrtechs.com/dbkeele.com/CBT.php


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 Post subject: Re: First tube amp
PostPosted: February 11th, 2015, 8:39 am 
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Joined: July 3rd, 2014, 7:47 am
Posts: 89
I had seen the CBT kit on PE. Looks amazing, but there is no way I could get away with speakers like that in our tiny house. Would be amazing to hear them in person.

I don't recall the brand, it may have been McIntosh, but there was a set of speakers at Grammaphone, they had to be 7 feet tall, maybe 24 inches wide, and it had to be a line array of some kind. The thing that amazed me, was whether you were standing one foot in front of them, or 30 feet back, the volume of sound was exactly the same. Don't know how it was done, but I remember being blown away by it.


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 Post subject: Re: First tube amp
PostPosted: February 11th, 2015, 9:51 am 
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JDCrae wrote:
I had seen the CBT kit on PE. Looks amazing, but there is no way I could get away with speakers like that in our tiny house. Would be amazing to hear them in person.

I don't recall the brand, it may have been McIntosh, but there was a set of speakers at Grammaphone, they had to be 7 feet tall, maybe 24 inches wide, and it had to be a line array of some kind. The thing that amazed me, was whether you were standing one foot in front of them, or 30 feet back, the volume of sound was exactly the same. Don't know how it was done, but I remember being blown away by it.


One of the reasons for what you heard with the McIntosh are with a tall line array you are in the near field for a greater distance from the speakers. The drop off with distance in the near field is half what occurs in the far field. Therefore the amplitude stays more constant with distance. Secondly the cylindrical wave launch of the sound in a line array minimizes the ceiling and wall reflections (assuming a vertical array) therefore minimizing reflections off those surfaces. As a result you get less contribution from reflections and more emphasis on the direct sound. Those are all good things. The tradeoff is that imaging is not as precise as with a point source. As the old saying goes, "youse pays your money and youse takes your choice".

Tom


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