Design suggestions with PA drivers-For PA use (small terrace parties):)

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prasi

prasi

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#1
Hello All,
I am looking to design a stereo set of PA speakers utilizing PA drivers as per attached spec sheet. Its all I have. There is also a cross over available from the manufacturer specifically designed for the combination of these two drivers.
Since I have limited / no experience, could some one suggest a speaker design (closed/vented, port dimensions, cab size (volume), etc.

regards
Prasi
 

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#2
What do you have in the way of amplification and signal processing?

The 12"s will want a large ported box to put out any bass, and the crossover from the 12" to the HF horn is going to be difficult. The HF horn wants to run from 3kHz (preferably 4kHz) upwards, while the woofer is already getting pretty rough up there.

Do you have access to any other drivers?

Chris
 
#5
The full-range driver looks better, but definitely isn't optimised for low-frequency output.
Do you want it to be very loud and/or have lots of bass?

I'm thinking you could do 2x full-range 12"s in one box, and put a big inductor in series with the bottom one.
Quality would be reasonable, and there'd be a useful amount of "thump" in the 70-100Hz region, even if it won't get particularly low.

Chris
 
#6
Its an open terrace and audience will be about 60-80 nos.

Indians (general public) do like it loud and lots of thumping bass for bollywood songs.
They wouldn't care for "Hi-Fi" as long as its loud and with lots of bass. Amplifier has tone controls, so it will probably be turned all the way up for bass and treble😉

I dont know if the full range will produce enough bass because of its small Xmax.
 
#8
Indians (general public) do like it loud and lots of thumping bass for bollywood songs.
They wouldn't care for "Hi-Fi" as long as its loud and with lots of bass.
Click to expand...
Then use the most powerful, largest magnet, largest voice coil, most overhang of them, it being the L12MB200.

All suggest some kind of enclosure except that one, do you have size/weight limitations?
Do you need to carry it everywhere in a car or station wagon?
If not, as suggested above build a large cabinet, somebody around will certainly simulate and suggest dimensions and tuning for that woofer based on datasheet TS parameters.
Or ask Ahuja for a suggested cabinet for that speaker.

I am more worried about the tweeter, you will blow it to pieces the moment your amp reaches clipping which will happen 15 minutes into the the Party.

I suggest you use a typical auxiliary car lamp in series with tweeter, *after* the crossover output, 12V 15W is a popular value.

Amplifier has tone controls, so it will probably be turned all the way up for bass and treble
Click to expand...
Oh PLEASE DON´T .

Don´t push into speakers frequencies thy clearly can not handle.
You-can´t-beat-Physics.

As soon as you can, build an extra pair of cabinets and drive them with another 200W power amp.
 
#9
Oh, sorry, I should have been more clear. I plan to build these speakers for the housing society where I live. So I will never have any controls on how its used/abused.

I have written to the Ahuja, but no reply🙁.

size shouldn't matter I think(width or height wise), but weight would better be limited to about ~30 kg.
I will try simulate the L12 MB 300, in a 70 to 80 liter ported cabinet.

What function the 12V car lamp do, I mean how does it help in protecting the tweeter?

Regards
Prasi
 
#10
Here is a quick check of the ported box alignment in Unibox and box dimensions in Boxycad.
The woofer is http://www.ahujaradios.co.in/Document/0-L12-MB300_OM.pdf

The volume of box is 70 liters tuned to 45Hz. Weight becomes 20kg with 3/4" material and some bracing.
Adding driver weights (~10kg for woofer +horn), the total weight becomes nearly 30kg per box. Two people would be needed to move!
 

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#13
prasi said:
What function the 12V car lamp do, I mean how does it help in protecting the tweeter?
Click to expand...
A resistor in series with the tweeter will protect it by attenuating power, but there´s a choice dilemma:
* a small value resistor (say a couple o0hms) will not be noticeable, but will offer little protection.
* an higher value one , say 12/15 ohm will attenuate much more ...but sound will be dull.

We need an "intelligent" resistor which does little at normal power but which detects abuse and attenuates a lot ... yet goes back to normal when abuse stops.

It does exist 😱 :

image_9680.jpg


this is the crossover from an AMPEG Bass Guitar cabinet; as you know Musical Instrument and DJ speakers are the most abused on the Planet, being overdriven by clipping amplifiers every day, that is the "normal" wayn to use them:

imageuploadedbytalkbass1409408917-505415-jpg.470976


This is a JBL crossover:

s-l1600.jpg


you connect crossover as usual but one of the wires going to tweeter is cut and a lamp bulb is connected in series.

Absolute worst case, with a terrible overload, lamp blows as if it were a fuse.

In any case way cheaper and easier to replace than original tweeter or driver.
 
#15
Yes, basically same effect.

In both cases it is a current limiting PTC resistor, with the added advantage that it´s cheap, widely available, well packaged and has free built-in visual indicator 😉

Oh, and given the minuscule thermal mass, very fast acting 🙂
 
#16

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  • port air speed-L15-MB300.png
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