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Old 13th January 2010, 06:39 AM   #1
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Default Hi-Q speakers, small boxes, DSP-EQ & phase

Hi all,

Apologies if this has been discussed previously; I went looking but got lost in a myriad of info...

I'm looking at building a line array using 16 small full-range drivers; it's for a PA application, a la bose L1. The appeal is portability (relatively lightweight & wrangleable cabinets, no need to lug extra stands...). Will be augmented from about 200Hz down via a modest sub; will be used for small-med cafe/functions, so doesn't need to be a room shaker.

I'm looking to keep the drivers small (4 ") and will probably need to use some digital EQ (via a Behringer DEQ2496) to even the response out. The cabinets are some suitably shaped aluminium extrusions, but the volumes per driver may be on the low side (depends which drivers I plump for in the end, though).

I have a couple of questions that I'm hoping to get some good advice on from you very knowledgeable folk out there:

1) Small drivers tend to be on the low-side for power handling; accordingly I'm looking for hi sensitivity drivers to extract as much SPL (relatively speaking for their size, at any rate; 90dB/w/m is the best I've seen without spending big $$ per driver) out of low input power and then exploit the multiple serise/parallel driver factor to yield a 102dB/w/m figure for 8 drivers, then amp each set of 8 (2 sets for 16 in total) to get 105dB at the end.

However, hi-sensitivity seems to come with a hi-Q factor; I've seen in some cases up to 1.75 - 2 (I think they're ceiling speakers). In a small enclosure, they'll peak high as expected, but this can be flattened out using DSP-EQ. My first question is: the phase response would be less than ideal to begin with, but would flattening the repsonse improve the phase response any? Or would it stay the same (or even get worse?)

And on a vaguely related but slightly different note:
2) With a standard series/parallel drive set up of, say, 4 drivers to keep things simple, although the amp would see the equivalent impedance of a single driver, would the power handling (ie, before failure) be double that of a single driver, given that the 'weakest single link' in series is now a parallel pair?

Sorry for the long-windedness of this; any help would be much appreciated!

Thanks heaps!

Paul
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Old 23rd June 2010, 12:48 PM   #2
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Hi Paul,
I was wondering if you have got much further with this. I am working on something similar, also for a small pa. I have so far decided to go the route of using 9 full range drivers at quite low wattages on an open baffle line array and I'm trying to select the drivers whilst keeping the price down.
What did you go for in the end? - I'm just looking at visaton and tesla so far because they are easy to get hold of here in CZ.
I am not sure if the drivers require the usual robustness that pa drivers need because they won't be suffering from the same level of excursion - does anyone have an opinion on this?
Also, to deal with so many drivers and impedance, the wiring will have to be serial/parallel - does this further compound phase problems?

Anyway - I hope the project is going well for you and you are out there gigging with this thing already.
Cheers
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Old 23rd June 2010, 07:47 PM   #3
preiter is offline preiter  United States
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Quote:
Originally Posted by Horn_aficionado View Post

However, hi-sensitivity seems to come with a hi-Q factor; I've seen in some cases up to 1.75 - 2 (I think they're ceiling speakers).
There is no reason why high sensitivity speakers need to have high Qts. Ceiling speakers are designed for an infinite baffle application and are specifically designed to have high Qts.

Keep looking, you will find drivers more suited to your application.
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Old 23rd June 2010, 11:23 PM   #4
Tom V is offline Tom V  United States
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Here is a link to a project with line arrays of inexpensive speakers equalized with the DEQ2496. I used a similar Aurasound driver for computer speakers and it sounded quite nice without equalization.

The Murphy Corner-Line-Array Home Page
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Old 23rd August 2010, 11:01 AM   #5
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Well, I went ahead and made my open baffle array. I did it under my usual time constraint panic because I had a small gig coming up where I wanted to test it.
So firstly, the idea was to make a speaker that dealt with the following points:
1. Could be fairly easily transported in the small car that we use
2. Would handle nylon-acoustic guitar and vocal duties in smaller gigs where they have either no or a next to useless pa.
3. Very little bass would be needed but fairly good hi-fi production from 150hz upwards.
4. Good feedback resistance with a comfortable output to cover up to 40 (quiet) people in a cafe/gallery sized space.
5. Would cost very little in terms of money

So I cobbled this thing together with wood scraps and 8 Visaton FR10 8ohm drivers.
I did do a bit of planning for the open baffle using xbaffle and worked out the spl from having 8 drivers - after that it all became very unscientific! Still they work and for their application they do very well indeed. I felt much happier with my sound than I have in a long time, I could sit right next to it with two mics and driving it with about 50 watts rms; didn't blow mine or anyone elses ears off but could be adequately heard.
I only spent 1500kc (40.00) in total so for a cheapo like myself it's a good thing, especially when one considers the commercial alternatives.
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Old 24th August 2010, 06:02 AM   #6
Tom V is offline Tom V  United States
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This should be interesting reading for you.

The Murphy Corner-Line-Array Home Page
http://www.trueaudio.com/array/

-Tom-
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Old 24th August 2010, 06:02 AM   #7
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I too am interested in this (I can't believe some other manufacturer hasn't cloned the Bose yet). The Bose is fantastic.... but (I'm a ) 2-bit musician, and really can't afford to dump $2k in a speaker column (especially in this day of nickel & dime'n the help). Since you've had time to play with this awhile... how is the dispersion (Bose claims the sound at the back of the room is equal to the sound at the front of the room)...
Any other ideas for drivers out there?
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Old 24th August 2010, 07:14 AM   #8
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Well I probably can't compare my version to the Bose L1 but on first use the dispersion certainly seems better than a typical acoustic amp or PA speaker. I'll let you know more after my next gig with it - I'll be using a bigger amp/mixer this time too.
BTW - Fishman have done a small line array job called the Fishman Solo but even that retails at around 800 - 900. Definitely a good reason to build something yourself.
Tom V - I did read about your array the first time you put the link up - the whole study and the end product looks fantastic. Congrats.
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Old 24th August 2010, 08:59 PM   #9
Tom V is offline Tom V  United States
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Oops double posted while referencing my post in another thread.

>>Tom V - I did read about your array the first time you put the link up - the whole study and the end product looks fantastic. Congrats.

Not my work, Murphy's! But it did seem apropo of what you are trying to do.
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Old 25th August 2010, 07:26 AM   #10
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oops sorry - Murphy's array - don't know why I assumed you were the author.
Yeah - it looks great but a bigger project than I could do at the mo' and a little overspec for my needs (still, as he points out, it could be adapted). Have you tried anything similar?
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