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Old 18th September 2015, 02:57 PM   #1
vokus is offline vokus  United States
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Default Line Array with Bookshelf Speakers Possible?

I have a set of Bic America FH-65B bookshelf speakers.
Click the image to open in full size.
[SPEC LINK]

I have been listening to them for a long time, and I really love them!

Can some one explain what would happen if I stack 8 speakers, floor to ceiling, using series/parallel wiring, per channel?

I want to have 8 speakers for the left channel, and 8 speakers for the right channel.

1. Is this a good idea?
2. How do I do it properly?
3. What type amp power would this require?

Last edited by vokus; 18th September 2015 at 02:59 PM.
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Old 18th September 2015, 04:05 PM   #2
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Quote:
Originally Posted by vokus View Post
I have a set of Bic America FH-65B bookshelf speakers.
Click the image to open in full size.
[SPEC LINK]

I have been listening to them for a long time, and I really love them!

Can some one explain what would happen if I stack 8 speakers, floor to ceiling, using series/parallel wiring, per channel?

I want to have 8 speakers for the left channel, and 8 speakers for the right channel.

1. Is this a good idea?
2. How do I do it properly?
3. What type amp power would this require?
1) No.
2) Use tweeters that are small enough to be only a wavelength (or less) distance apart at their crossover point.
3) An amplifier of sufficient power to drive the speakers to the desired SPL (sound pressure level). Using more speakers increases sensitivity, so less power is needed for a given SPL. That said, using more speakers not designed to array vertically will cause severe peaks and dips (comb filtering) in the upper response.
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Old 18th September 2015, 08:18 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

1. Not really.
Though you'd stack them on their sides,
which won't give floor to ceiling height.

2. Something like :
Audio Artistry CBT36K Line Array Speaker Pair Kit
Not cheap, but neither are 16 bookshelves.

3. A lot of power if being used as a a PA system.
At home your normal amplifier would fine, even
if you wired the 8 spekers for double impedance.

rgds, sreten.
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Old 18th September 2015, 11:29 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

The tweeters look assymetric. You'd rotate them 45 degrees for side stacking.

rgds, sreten.
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Old 19th September 2015, 02:14 AM   #5
system7 is offline system7  United Kingdom
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I can never hear combing, myself. Or at least it never bugs me. I must be deaf.

Since these speakers are cheap as chips at $100 a pair, I see no reason why you can't buy a second pair and wire them in series for 16 ohms. But 4 or 8 might be getting silly.

Makes a cheapie MTTM. You gain loudness and authority on axis. Multiple driver's power falls off more slowly with distance, which is why they are used in PA systems.

You can try mono right now.
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File Type: jpg Poor_Man's_MTTM.jpg (112.8 KB, 210 views)
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Old 19th September 2015, 03:00 AM   #6
vokus is offline vokus  United States
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Thank you very much every one!
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Old 19th September 2015, 05:21 PM   #7
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Quote:
Originally Posted by system7 View Post
I
Makes a cheapie MTTM. You gain loudness and authority on axis. Multiple driver's power falls off more slowly with distance, which is why they are used in PA systems.
Multiple drivers SPL (sound pressure level) falls with the usual inverse distance rule, 6 dB per doubling of distance in free space if the acoustic centers of the drivers are within 1/4 wavelength of each other in their pass band.

"Line array" SPL also falls at 6 dB per doubling of distance, but the interference pattern in the near field causes the SPL to be relatively lower there, giving the appearance of falling at 3 dB per doubling of distance due to the comb filtering (that you can't hear ;^) ).

To actually make a speaker fall off at 3 dB per doubling of distance requires a parabolic or hyperbolic reflector to concentrate the beam into a coherent wave front.

If you are interested, this thread gives some details into those developments:
HyperboLine Projector
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Old 19th September 2015, 09:52 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

Nonsense. All long and thin drivers exhibit the 3dB dispersion at
frequencies above the lines wavelength, and similarly so do line
arrays that are also in the phase coherent region.

rgds, sreten.

And of course long throw horns can also do it easily.

Last edited by sreten; 19th September 2015 at 10:00 PM.
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Old 20th September 2015, 02:08 AM   #9
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by weltersys View Post
"Line array" SPL also falls at 6 dB per doubling of distance, but the interference pattern in the near field causes the SPL to be relatively lower there, giving the appearance of falling at 3 dB per doubling of distance due to the comb filtering (that you can't hear ;^) ).
I went into this looking for a sign of widening directivity at some point but it appears to be persistent with distance (plane source a few wavelengths across). Directivity appears to be related to the interference pattern with some of the power being lost in the 'crossfire'.
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File Type: png ripple.png (231.4 KB, 146 views)

Last edited by AllenB; 20th September 2015 at 02:12 AM.
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Old 20th September 2015, 03:28 AM   #10
system7 is offline system7  United Kingdom
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I always like the mathematics in these sort of situations.

Something about line arrays which I quote in the pictures:
INTRODUZIONE AI SISTEMI "LINE-ARRAY" - Palcoplus - professional array system

Whatever you think of combing, on the horizontal axis there is none. When you double up drivers in an MTTM you are only using half the amplifier power for the same sound level. This must help distortion for one thing, since each driver is only outputting a quarter of the power.

MT has a problem in delivering sound across a room. You've experienced this. Get close to a spherical falloff MT type two way up on the nightclub ceiling and it blasts your ears most unpleasantly.

MTM has a problem too. The tweeter falls off at inverse square, but the twin woofers or mids at inverse distance. I like the MTTM idea, but a certain subtlety in using wider dispersion BW3 filters which is for the real enthusiasts.

How about MTTTM? This is interesting. The Tekton Pendragon uses it. Philips came up with the idea that three stacked drivers should be connected in a 1:2:1 binomial voltage level to lessen vertical combing. Or 1:3:3:1 with 4 drivers. I don't know what Tekton actually do here.

Anyway, lots to think about. It's fun.
Attached Images
File Type: png Line Array.PNG (59.0 KB, 139 views)
File Type: jpg Spherical Waves.JPG (40.7 KB, 22 views)
File Type: jpg Wharfedale E70.JPG (47.3 KB, 30 views)
File Type: png Wharfedale E70 Crossover (2).PNG (8.8 KB, 36 views)
File Type: jpg Tekton Pendragon.JPG (16.3 KB, 489 views)
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