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Old 13th July 2005, 12:10 PM   #1
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Default Nearfield Stargate

I found the post here recently about the headphones vs speakers interesting -

My current speaker project/idea is to build a near/mid field speaker system to compete with Signet Electret headphones in detail and smoothness yet still have the 'live' illusion with all the power, dynamics, and 'feel' of a large fullrange horn system. Most important here is using very 'fast' and linear drivers and configuring them for the LEAST 'negative' room interaction -

The goal is to allow 3 people to be able to share this illusion (wide sweet spot) from under 8' away. This rules horns out for use below 600 cycles (too wide of driver spacing for close listening)- so I am steering towards a near full range cardioid with 100 db+ sensitivity. Problem is getting it to appear as a point source at close distances and still be 'full range' and with low dynamic compression.

Has anyone here had success at this?

How did you achieve it?

Binauraul cardioid??? Can't do it - have a projection screen between the speakers.
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Old 13th July 2005, 01:04 PM   #2
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Default How about a line source?

In nearfield - maybe this is where I need to look???
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Old 13th July 2005, 04:57 PM   #3
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Default mission (almost) impossible

(sorry for my english)
Hi Magnetar,
IMHO you can do a choice: power vs accuracy. If you take the second
think at a 6 feet triangle with one pair of minimoitors and a very massive absorbant treatment of early reflections ( ideally a LEDE).
Now you can start to experimentate all the x-overs and drive units
you want. When the speakers "disappear" and the timbre is very close to your ref headphones you are OK.
IMHO very high levels are not indispensable with this setup.
A lot of passion and time is necessary because "standard-sound" is very far from this IMHO.
regards
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Old 13th July 2005, 06:56 PM   #4
DeonC is offline DeonC  South Africa
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Hi Mag

I suggest you look at co-axial speakers. Maybe a pair of Tannoy 15" drivers (Red, Gold or HPD) with suitable subwoofers in an tower with the subwoofer drivers flanking the Tannoy driver. It'll be big, but might suit your needs. The are other drivers that might also work (one suggestion might be the B&C co-axials). Just an idea.

Enjoy,
Deon
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Old 14th July 2005, 06:11 AM   #5
Bill F. is offline Bill F.  United States
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Default If you're not afraid of digital...

I'll second the coaxial suggestion.

Were I doing it, I might divide off the sub-bass (where the wavelengths are long enough that everything's nearfield) and send it to a nice big sealed sub or array of subs that are out of the way. That will let you use higher-efficiency midbass drivers and have less massive nearfield units. Nearfields would be delayed to time align them.

For the midbass, I might try a 2nd-order gradient (twice the directivity of a cardioid for least poss. room interaction). They're complicated to set up in the analog domain, but relatively simple to do digitally.

A second-order gradient is simply two dipoles separated by x meters. The rear dipole is wired out of phase with the front and delayed x/1100 seconds. Since a 2OG rolls off at 12dB/octave, they don't go very low and EQ is required.

I plan to experiment with making one with a DEQ2496 and a soon-to-arrive Panasonic XR25.
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Old 15th July 2005, 04:52 PM   #6
Bill F. is offline Bill F.  United States
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Ahem, oops. x meters should be x feet, of course...
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Old 15th July 2005, 04:55 PM   #7
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Default Re: Nearfield Stargate

Quote:
Originally posted by Magnetar
I found the post here recently about the headphones vs speakers interesting -

My current speaker project/idea is to build a near/mid field speaker system to compete with Signet Electret headphones in detail and smoothness yet still have the 'live' illusion with all the power, dynamics, and 'feel' of a large fullrange horn system. Most important here is using very 'fast' and linear drivers and configuring them for the LEAST 'negative' room interaction -

The goal is to allow 3 people to be able to share this illusion (wide sweet spot) from under 8' away. This rules horns out for use below 600 cycles (too wide of driver spacing for close listening)- so I am steering towards a near full range cardioid with 100 db+ sensitivity. Problem is getting it to appear as a point source at close distances and still be 'full range' and with low dynamic compression.

Has anyone here had success at this?

How did you achieve it?

Binauraul cardioid??? Can't do it - have a projection screen between the speakers.
Please email thylantar@hotmail.com he has the design you're looking for....
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Old 15th July 2005, 05:00 PM   #8
morbo is offline morbo  Canada
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I think 3 people may be a bit ambitious, that means you want a sweet spot as big as a couch, with speakers less than 8' away? I listen from 7' away and no speaker I've tried (even fullrange) gives a sweet spot that size. The image always pulls to one side or the other for the 2 outside listeners on the couch. In general the closer you get the smaller the sweetspot.
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Old 15th July 2005, 05:36 PM   #9
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Quote:
Originally posted by morbo
I think 3 people may be a bit ambitious, that means you want a sweet spot as big as a couch, with speakers less than 8' away? I listen from 7' away and no speaker I've tried (even fullrange) gives a sweet spot that size. The image always pulls to one side or the other for the 2 outside listeners on the couch. In general the closer you get the smaller the sweetspot.
I've heard several ESLs that did not do that from around 10 feet away
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Old 15th July 2005, 05:37 PM   #10
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Default central position

(sorry for my english)
Morbo, you are right. Only one listener for nearfield "triangle". I had not exactly understood what Magnetar asked. My poor english....
regards,
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