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Array for midrange: good idea?
Array for midrange: good idea?
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Old 3rd September 2017, 07:09 PM   #1
LewinskiH01 is offline LewinskiH01  Argentina
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Default Array for midrange: good idea?

I came across a post talking about midrange arrays that picked my interest and would like to learn more.


I'd like to consider them in the context of a multiway system, with TPL-150H as tweeter above 2kHz and large woofers taking care below 350Hz.


I like the ability to use multiple smallish midranges (4 to 6") to achieve a large total radiating surface, high sensitivity that can be achieved, and the evening out of reflections. I'm sure there are drawbacks as it would otherwise be more widely used, and I'd like to learn pros/cons of this approach.


Thank you!
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Old 3rd September 2017, 07:51 PM   #2
boswald is offline boswald  United States
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Array for midrange: good idea?
It's actually used quite often. The first doubling gives the most benefit, with lesser returns until the line is long enough to really change the dropoff-with-distance. My Pentas have four mids with one tweeter nestled in next to the middle. They still fall off at 6db/2x distance, so there is no mismatch with the tweeter's loudness at a given distance.
So go ahead and play with it. The longer your line the more you will restrict the vertical dispersion, this may help in your room; if you are tall and your couch low, you might want a shorter line. If your line is really long you may want a line of tweeters.
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Old 3rd September 2017, 09:22 PM   #3
LewinskiH01 is offline LewinskiH01  Argentina
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Quote:
Originally Posted by boswald View Post
The longer your line the more you will restrict the vertical dispersion, this may help in your room; if you are tall and your couch low, you might want a shorter line. If your line is really long you may want a line of tweeters.
Thank you.

Can you explain why the longer the line the more the vertical dispersion is restricted?

I'm not tall, but my AMT tweeter has an 80x30 degree horn so vertical dispersion mismatch is one of my concerns.
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Old 3rd September 2017, 09:33 PM   #4
Wavebourn is offline Wavebourn  United States
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Array for midrange: good idea?
Gorgeous idea!

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Old 4th September 2017, 12:46 AM   #5
boswald is offline boswald  United States
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Array for midrange: good idea?
Okay. Look at it this way. You have heard that smaller mids have wider dispersion than larger ones. If we make a column of 4 inchers it's still 4 inches side to side, but four of them are a 16 incher vertically. This is the same effect that is a problem when you lay an mtm on its side as a center channel and you have a very wide seating area close to the screen&speaker. In your case with that tweeter I would say that a line of four little mids or at least two bigger ones(mtm) is not only okay, but probably necessary to match the dispersion of your tweeter. Seems like the analog part of your brain had the right idea- the other part said "wait...what?"
If you had told us of your tweeter, this is what I would have suggested without knowing you were interested in a line of mids. To put it another way, if you had said you wanted a single tweeter for a line, something like what you have is what I would suggest. So have a little more confidence in your instincts, they're pretty good.
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Old 4th September 2017, 12:53 AM   #6
eriksquires is offline eriksquires  United States
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I can recommend the Peerless 830xxx series, and the FaitalPRO 5FE120's also have a very good rep.

The Faital has significantly better high frequency extension, but I have not heard it. The Peerless are really awesome sounding performers in their limited power envelope.
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Old 4th September 2017, 01:06 AM   #7
eriksquires is offline eriksquires  United States
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As far as matching goes, the issue is really level related. If you put 4 x 5" drivers vertically, that's about 2' worth of vertical coverage, assuming the tightest possible dispersion. That's pretty comfortable for sitting or standing in front of the speakers in most homes.

In my humble and inexperienced opinion, a larger problem is the drop off over distance.

At 9' , 12', 16', etc. the tweeter and mid levels may no longer match. So long as you can adjust for this, you should be good. I often see line arrays with L-Pads for just this reason.

With different dispersion patterns the rate at which the level drops off is quite different. This is not unique to line arrays though. Horn loaded systems with direct radiating woofers have the same kinds of issues.

Do consider an AMT without a horn though, as the dispersion characteristics may be much closer.

Best,

E
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Last edited by eriksquires; 4th September 2017 at 01:14 AM.
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Old 4th September 2017, 02:01 AM   #8
ScottG is offline ScottG  United States
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Quote:
Originally Posted by LewinskiH01 View Post
I came across a post talking about midrange arrays that picked my interest and would like to learn more.


I'd like to consider them in the context of a multiway system, with TPL-150H as tweeter above 2kHz and large woofers taking care below 350Hz.


I like the ability to use multiple smallish midranges (4 to 6") to achieve a large total radiating surface, high sensitivity that can be achieved, and the evening out of reflections. I'm sure there are drawbacks as it would otherwise be more widely used, and I'd like to learn pros/cons of this approach.


Thank you!


It's a particularly good idea for the mid-bass transition for baffle-step (up to about 450 Hz - depending on baffle size). (..say 4-6 drivers from floor, up to tweeter with mid array above that.) The midbass array becomes a "lumped" grouping of reflections that minimize suck-out from floor-bounce while also allowing for an easier crossover that doesn't need baffle-step compensation. It also "loads" or is bounded to the floor to improve loudness (which is particularly useful for a very narrow baffle).



For the mid.s, when you have 4 or more drivers you'll get added gain between about 400 Hz and 1.3 kHz (..ex. with 4 drivers, maybe an added +1 db in addition to other sources of gain). The more drivers, the more added gain.

As far as difficulty with line-source behavior (..lack of pressure loss vs. point source), you can look at the line-source transition for listening distance on page 8 fig. 5 here:

http://www.audioroundtable.com/misc/nflawp.pdf

-basically, a half-meter (about 20"s) array of mid.s at a 2 meter distance will display point-source pressure loss behavior (up to almost 5 kHz) - so that should be sufficient for most low-pass crossovers around 2 kHz. Note: the further the listening distance the higher the freq. where it starts becoming a line source.

The mid. array allows for enough height off of the floor to lower the freq.s where any floor-bounce suck-out would occur.

Floor/Ceiling Reflection Calculator



The one thing you should plan-on with a design like this is a stepped baffle, with the tweeter being inset the most, then the mid.s, and no inset for the woofer array. (..and typically with a bit of felt placed above and below the tweeter to avoid reflections.)


Overall, a design like this can provide good eff. for a narrow baffle while simplifying the crossover design and providing a fair bit of rejection from floor and ceiling bounce suck-out.

Frankly I'm surprised I don't see more commercial designs based on this format.
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Last edited by ScottG; 4th September 2017 at 02:09 AM.
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Old 4th September 2017, 03:44 AM   #9
Wavebourn is offline Wavebourn  United States
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Array for midrange: good idea?
Here are some examples:

Vaughn Loudspeakers high-end high-value no compromise
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Old 4th September 2017, 09:14 PM   #10
rb132333 is offline rb132333  United States
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Have you ever looked at Nola Speakers - specifically the Baby Grandes?

Nola by Accent Speaker Technology Ltd.

I forgot to mention - open baffle too.

Last edited by rb132333; 4th September 2017 at 09:23 PM.
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