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Full range line array in a tube
Full range line array in a tube
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Old 22nd July 2010, 04:55 PM   #21
bear is offline bear
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Afaik, this is a Bessel Array - "gradual release" I think is something else found in certain books on personal matters??

Yes, you can use an inductor in series, however you can not use a parallel element on other drivers without creating a crossover that takes into account all the other drivers - that would be in effect a series crossover.

You can use a series capacitor to roll off the lows on the top ones (or any driver you choose), but why would you want to roll off the lows?? The array needs the surface area to keep the xmax low and/or keep the max SPL at LF high at low frequencies...

You can try all sorts of variants on the theme with a line array - the main thing is that you learn something in the process and that you like the results... when I am going to do lots of experimenting, I try to bring out the connections to the speakers (in this case groups of speakers?) to the rear of the cabinet so I can change things pretty quickly without having to disassemble the box to do it.

If you go to my website (which has not been updated in a long time now) and look at the Archives section you can find a box called the CVSR... from 1976. It worked great with EQ on the bottom octave or so and a tweeter (not shown).

CVSR image

After that I made some speakers that were in Speaker Builder mag, that used a similar concrete form tube that I sliced in the front and glued a 1/4" masonite baffle on that, cast some concrete tops and used a PR for the bottom... made a two way that way using a pair of Goodman's Maximus drivers and a Panasonic leaf ribbon, and another version with a single Audax 5.25" driver & the same tweeters... later added the Focal T60 tweeter... still have a few of them around the lab... but the idea was to build out into a line array when I started those... I went quick, cheap and dirty with the construction: hot glue and flat black paint with open cell foam wrap!

the foam is long gone...

_-_-bear/
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Last edited by bear; 22nd July 2010 at 05:01 PM.
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Old 22nd July 2010, 06:23 PM   #22
carpenter is offline carpenter  United States
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Full range line array in a tube
Very pretty, bear. How does it sound?
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File Type: jpg CVSR3.jpg (56.6 KB, 357 views)
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Old 22nd July 2010, 06:37 PM   #23
no gas is offline no gas  United States
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Originally Posted by jrenkin View Post
Awesome! I have though of, but never done, a speaker using these tubes. I too thought there would be vibration, so my imaginings were with two sono tubes, 8" and 10", concentric with sand or concrete between them. Just a thought.
I've built many a dual sonotube with sand in between the two tubes. They are DEAD. Knock on them and you get a dull thud. Make sure you use 'sterilized play sand' or you might find weeds sprouting out of the tubes! Sand is better than concrete as the particles absorb energy. You can make a base cap by routing out a wooden disc with grooves to slide the sonotube into. This keeps them spaced right.
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Old 22nd July 2010, 06:42 PM   #24
carpenter is offline carpenter  United States
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Full range line array in a tube
Great suggestions, no-gas.
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Old 22nd July 2010, 06:52 PM   #25
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I've built many a dual sonotube with sand in between the two tubes. They are DEAD. Knock on them and you get a dull thud. Make sure you use 'sterilized play sand' or you might find weeds sprouting out of the tubes! Sand is better than concrete as the particles absorb energy. You can make a base cap by routing out a wooden disc with grooves to slide the sonotube into. This keeps them spaced right.
Sigh, all the good ideas are taken....

Do you leave the top open, or make a sealed enclosure?
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Old 22nd July 2010, 07:05 PM   #26
no gas is offline no gas  United States
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Sigh, all the good ideas are taken....

Do you leave the top open, or make a sealed enclosure?
Actually, I beveled the top at 45 degrees and mounted a 6.5" woofer in the top with a tweeter pole mounted on the high end. take a look at the Oskar Heils speakers to get an idea of the mounting. I wish I had some pictures of them but they were about 6 speakers ago (read 10+ years) and storage space ment their demise. The woofer was a Vifa M18WO09, a great driver no longer made.
I also did a periscope variant that looked funky but was too top heavy for its own good. I looked at it wrong and it fell over releasing 120 lbs of 'sterile play sand' into the carpeting. My girlfriend explained the meaning of life to me and the self-presevationist in myself concluded that sand was no longer my friend.
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Old 22nd July 2010, 07:58 PM   #27
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carpenter - it was a very impressive speaker - that was without any finish on the particle board (pressed wood chips)... it had the uncanny effect of sounding very very "un-loud". As you cranked the volume it seemed like your seat was moving closer to the stage, the sound got "bigger"... nothing more. At that time we were using a Phase Linear 700 to power it, and with the EQ, the meters would jump when it was cranked... that set used early Peerless 5.25" drivers - in those days TS parameters were very new and exotic, and difficult to use... quite frankly I guessed and got it pretty close as far as the box volume.

The concrete was for a TOP of the little cylindrical speakers - not elsewhere. It was necessary to add mass to keep them from literally dancing around a shelf or table! I suppose if they were double walled and sand filled that they would stayed put!

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Old 22nd July 2010, 07:58 PM   #28
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Sigh, all the good ideas are taken....

Do you leave the top open, or make a sealed enclosure?
I seal the top, but create a port on the bottom. A high Qts driver in this enclosure generates better bass with a port than when it's sealed. There's the associated box resonance that a port introduces, but I think it's a fair trade-off the the bass extension.
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Old 22nd July 2010, 08:00 PM   #29
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Full range line array in a tube
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carpenter - it was a very impressive speaker...
_-_-bear
I can only imagine! Do you remember the driver Fs?
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Old 22nd July 2010, 08:18 PM   #30
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sort of... probably around 45Hz... it was quite a difficult thing, and still is to get small drivers with a low Fs... (still looking). The problem is that with a low Fs the cone mass goes up, the suspension gets woobly, and so you make the suspension stiffer to handle it, so the Fs goes up, etc... Also if you make it work then the efficiency drops like a stone, and with a small driver it tends to be low to begin with... the line array "rescues" this, but there are limits to it.

See if you can search for a picture of the Goodman's Maximus driver... it had some really spectacular features, even today it would be a contender. The guy who designed it, you may have heard of? Ted Jordan.

At the time we didn't know that.

But I think you can get similar results with modern drivers, maybe even better results - one needs to take into account the things that are now known about building speakers though.

_-_-bear

PS mating a line array with a tweeter is not so simple...
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