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Old 6th September 2006, 02:46 PM   #1
Klimon is offline Klimon  Belgium
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Default Tweeter line array

Hello;

Would a cone tweeter line array work or give terrible lobing problems? The tweeters are old alnico with 2,5" paper cones, I plan to mount four of them on each baffle, directly above-below one another. The woofers will be mounted above (4) and below the tweeter array (4), both woofer 'panels' will be tilted towards the listener as to simulate a concave baffle. I won't have a huge line array soundstage that way but my main aim is very high efficiency + acceptable imaging. Simple OB with asymmetrical U-wings.

Any thoughts?

Thanks!!

Simon
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Old 10th September 2006, 02:16 PM   #2
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The answer to your question isn't simple.

The lobing question depends on the xover frequency and almost entirely its relationship to the 1/4 wave distance between the acoustic center of each tweeter... which will matter more as you get vertically off axis, not so much horizontally.

Oh, the smoother/gentler the edges/transitions of the tweeter enclosures, and the wider (given the likelyhood of a fairly low xover freq for tweeters) the better the response will be.

No need at all to curve the woofers, most likely a waste of effort.

The key will be to keep the woofers (at least one end) close to the floor so there is no "floor bounce" cancellation to put a nasty notch in ur midbass response.

The advantages as you noted will be increased sensitivity and at the same time lower distortion for a given SPL level than one single driver alone.

IF this is a "quick and simple" project to get some sound, with the benefits you noted, then it makes good sense. Since you can buy inexpensive cone tweeters, well inexpensively you might want to consider buying a significant number of them and making a much taller line source...? Just my opinions.

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Old 12th September 2006, 06:50 PM   #3
Klimon is offline Klimon  Belgium
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Thanks for your advice bear; as you guessed: just a cheap project with vintage drivers. It's mainly about high eff. and trying something different.

Simon
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Old 19th September 2006, 01:02 AM   #4
v-bro is offline v-bro  Netherlands
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for high eff. building a horn 'round one may help...

But I like your line array idea, and maybe more tweeters help not only efficiency but also disperse the lobing effect better?
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Old 1st October 2006, 04:55 PM   #5
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v-bro:

The addition of more tweeters will improve the sensitivity and reduce the effective distortion at a given SPL level compared to one tweeter.

The lobing will be the same as it would be between any two (or three) tweeters mounted the same way, but the ability to get off axis vertically will be reduced as the number of drivers in the line source increases... there is also some benefit to be accrued by the lengthening of the line source, since the baffle size is increased in that dimension...

Ideally, if the acoustic centers of all the tweeters were made to be infinitely close you'd have a ribbon...

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Old 1st October 2006, 06:39 PM   #6
v-bro is offline v-bro  Netherlands
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Interesting Bear, my experience with multiple HF speaker interference is limited to my studies at school. My own interest is more dedicated to single HF designs.

After reading your post I thought "offcourse!" More drivers will have an easier job (handling power) producing the same spl and will give less distortion, and the more drivers the more the "bundling" will occur and make the sensitivity on-axis higher in comparison to off-axis response...

Maybe a curved baffle helps against bundeling?
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Old 2nd October 2006, 03:49 PM   #7
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curved?

which way?

there are problems no matter what... yin/yang

you get some sort of dipsydoodle in the freq response vs. vertical position(s) no matter what you do...

the problem of inherent polar response and distance between centers (sum + differencing) are sort of constants to cope with...

...in practice it still sounds pretty good to get a large line source.

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Old 2nd October 2006, 04:33 PM   #8
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a simple rule of thumb:
divide 13560 by the driver center-to-center spacing. This will be the highest frequency you can operate the drivers to without lobing becoming an issue.
So, with a 2.5" driver, you would be good up to about 5400 Hz. Some have said you can possibly go another octave higher, but any project I've seen where the limit is pushed degrades the response.
How about using them as a huge midrange array, and placing a dedicated tweeter right in the middle of it? (think super MTM)
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Old 2nd October 2006, 08:25 PM   #9
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Default What about a wave guide...

have a look at the Beyma line aray drivers. http://www.musicallife.de/ these are comp drivers that use a wave guide to permit line source configuration. Any reason you coud not use a wave guide like this on a cone unit? Regards Moray James.
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Old 2nd October 2006, 09:41 PM   #10
v-bro is offline v-bro  Netherlands
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Just read on a Dutch forum a post about that ribbon drivers and horns (put less than an inch apart) can be put in a line array with no real radiating problems. It also states that space should be virually zero between the drivers. This would help them "couple" better...

And somebody was building them in a half circular baffle...
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