Line array project

[VictorG]

Okay guys I am about too build two line array speakers to fit in a relativly small college dorm. Basically I'm just double checking with the talent that is this forum to make sure there are no show stopppers.

I plan to put 10 of these apexjr ribbon tweeters on each:
http://www.partsexpress.com/pe/pshow...9-025&scqty=10



and 10 of these mid ranges on each.
http://www.partsexpress.com/pe/pshow...9-025&scqty=10


I have already built two killer base systems, and one will accompany this system depending on the final dimensions of my room.

Anyway, let me know if you see any inherent problems. Also, i am a little unclear as to wiring in seris/parellel arrangments to keep a constant ohm load. When I hook all this up in sets of seris and parallel, while I keep the same ohm load, am i driving the amp any harder? I.E. would I need more current? A friend of mine thinks there will be an inherant problem in this design.

Also, what can I do to help the tweeter get better dispersion? would mounting it into a custom horn help?

Does anyone have expirience with this tweeter and if so what are it's limitations, and where hav you crossed it over?

Thanks guys,
Brian

[thylantyr]

You should ask Jim Griffin on the
madisound.com forum since he's
experience with these designs.

I line sourced eight cheap planar
tweeters all in parallel for 1 ohm load
and my power amplifier drove the tweeters without problems. This is not
the normal way to do it, but it just goes
to show you that tweeters don't draw
alot of power and you can load down
the amplifier more than normal. But,
if you do the same thing paralleling
woofers, your amplifier would hate life.

If you haven't done so, you can ask
on the forum for *his* Linus Array
document, it's a good reference on
how to build one.

[CharleyW]

Pardon me, but methinks that a 400HZ lower limit on those midranges is WAY too high.

You need something at least 80HZ (83 HZ is the lowest open string on a guitar when tuned to concert pitch - and the most frequent tuning is lower than that).

You need to get at least 60HZ out of the arrays (assuming these are for listening to music).

Just my opinion, feel free to slam away.

[roddyama]

Originally posted by CharleyW
Pardon me, but methinks that a 400HZ lower limit on those midranges is WAY too high.

Definately a show stopper. You're going to need 5" woofers (not mid-ranges) to get you down to 80Hz or so.
You also have the wrong link for the ribbons.

Here it is:
http://www.apexjr.com/speakerstuff.html

[planet10]

Originally posted by VictorG
why did you take the ribbon out of the provided chassis? what does this do for sound

Mostly to make them smaller... i never really listen to them unmodified.

Can I custom some horns for them?

I wouldn't do more than a waveguide built into the baffle and rear mount them... for a line array you really want to get them as close together as you can... it will be a pretty short array with only 10 tweeters.

Have you read Jim Griffin's white paper?

dave

[VictorG]

Okay, so the reason I thought i would be able to make it with 400 Hz mids is because I have two different bass systems that I plan to pair up with these which each make it to ~21Hz. I was told at lower freq. the ear cannot tell where the signal is coming from (white paper) and thus, i could use my other bass systems. This is okay right?

I have compleated a sonotube project with 4 peerless drivers (pictures soon), and I expect two sonotubes to flank each panel. This is the bass which will most likely be employed with this array.

On the tweeters, your right, is is pretty short. I may go up to twenty tweeters on each. I have a far out idea of mixing twetters (i.e. these ribbons with bullets) to help dispurse the sound. I'm pretty sure I read somewhere this was a bad idea though, and any lines I've ever seen have been similar tweeters.

I've read the paper, and would love to purchase those planar drivers and get a long array the easy way, but alas, the pathetic moneteary exisatanse of a student if becoming a reality..... sigh.

Thanks for you continued replies guys.
Brian

[nobody special]

Sound begins to get directional at around 200Hz, so you need to go lower. I would go much lower, if possible, which means that you need some midwoofers as others have said. Even if you are using a steep crossover, those mids will be reproducing some bass. To keep the crossover predictable, each driver needs to be able to extend somewhat into the other driver's range.
Steve

[DJNUBZ]

"Sound begins to get directional at around 200Hz"


From what I have experienced and have learned from other sources you can localize a sound source down to 80hz.

[roddyama]

The frequency at which sound starts to become directional will depend on a few factors. One is the size of the room. The larger the room, the lower will be the frequency for directionality. Another is the placement of the sub with relation to the main speakers. The frequency content and complexity of the music will also affect your ability to “find” the sub. The higher you x-over to the mid bass, the steeper your x-over slope (lo-pass) will need to be.

I cross to my stereo subs at about 90Hz with an 18db/oct xover in a 20’ X 18” room. When one of the sub channels when out, the stereo image began to shift around the sound stage, the sub became directional in the xover region.

[The Paulinator]

I must say that I feel that the directionality of bass MOSTLY depends on the quality of the bass. If there is a noticeable amount of distortion that is rhythmically in sync with the bass, that upper frequency distortion gives diirectionality to the bass the same way that your mains are supposed to give directionality to the bass. I know that bass becomes directional at a high enough frequency (dunno what it is), but so often the quality of the bass causes directionality before frequency does.