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Old 22nd October 2004, 07:49 AM   #1
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Join Date: Nov 2002
Location: Bangalore, India
Talking Is a line array possible with headphone drivers?

In my quest for affordable fullrange drivers (for line array for stereo use at home), I came up with an idea of using headphone drivers for the purpose. Since good quality drivers are not locally available in India, I have to resort to headphone drivers. I intend to use Philips drivers salvaged from headphones. The following are the specs which may help in checking the feasibility for the application. The factors I think supporting the idea are

1>The drivers are high in sensitivity.
2> The drivers cover the entire range of above 20 to 20Khz, although I intend to cross high around 300 Hz.
3> The individual driver SPL/power requirements in an array are less.

The factors against the idea are

1> The frequency response mentioned in the spec is in ear with ear gain (pls read room gain). That might not be the case when mounted in free (the drivers are already closed at the rear)

2> The line array sounds good partly because only a fraction of their SPL capability is used which is not the case here.

The following are the models and specs

Model: SBCHP200/00 and SBCHP250/00
Freq range: 15 - 22 000 Hz
Sensitivity: 100 db
Max power: 500 mW
Diaphram dia: 40 mm
Equivalent power as compared to a driver with 91 db sensitivity:
4 watts!

Model: SBCHP800/00
Freq range: 10 - 28 000 Hz
Sensitivity: 104
Max power: 1500 mW
Diaphram dia: 40 mm
Equivalent power as compared to driver with 91 db sensitivity:
Over 24 watts!!!!

Is it feasible?
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Old 22nd October 2004, 10:02 AM   #2
jdybnis is offline jdybnis  United States
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Sorry, that sensitivity rating is ear level not 1w/1m.

Normal speakers are rated at a distance of 1 meter. Headphones are rated for how loud they are when they are on your head.

Take a pair of these headphones, plug them in and run them at max volume. Hold them at arms distance. Are they 100dB?
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Old 22nd October 2004, 05:11 PM   #3
Few is offline Few  United States
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Location: Maine, USA
Default Grado did it

I recall seeing a photo of a vertical line array filled with Grado headphone drivers. It may have been in a Stereophile CES report several years ago. This doesn't address your question concerning the particular drivers you're proposing to use, but it does show the idea is workable with some headphone drivers.
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Old 23rd October 2004, 07:42 PM   #4
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This idea sounds really "out there"! But i like that. Can you get these drivers for CHEAP?

If they are small and cheap enough that you can use several hundred of them, I suppose there's some possibility there. As jdybnis said, this sensitivity rating is not likely to be a 1 watt at one meter.

If they're 2 cm drivers, and you can pack them really closely- 2 cm center to center- then take 300 per side, they could possibly be listenable. With Xmax and surface area we could figure out their max SPL and see if 300 per side is enough...even then they might not go very loud.

The bottom line- time is money. How long is it going to take you to drill, affix, and wire 600 drivers? Can you get them for free? If I had a free crate of headphone drivers and too much time on my hands, I'd consider giving it a try. (this very nearly happened to me during the summer after college!)
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Old 23rd October 2004, 11:45 PM   #5
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Location: Western Sydney
Default I might try it...

...one day, I've got access to free headphone drivers (made in china, z=~ 250 ohms. I'm building up a stock of them. 32 per array would give 8 ohms. I'm actually trying them as cheap microphones (and have too many other projects at the moment) but maybe they'd be ok for near field listening? I doubt if they'd have much x max though....hmmmm maybe I should just tape them to a piece of cardboard, wire them up & see what happens,
now you've got me going off on a tangent....
Pete McK
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Old 24th October 2004, 01:30 AM   #6
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Join Date: Feb 2002
Location: Western Sydney
Default you asked for it...

see attached gif of an array of 8
surprisingly, more lows than I thought I would get,
couldn't get much output into 32 ohms, but an array of 32 might be worthwhile, even if it needs some bass supplimentation....
(batteries were flat in my sig generator, so couldn't test further)

Pete McK
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File Type: gif array2.gif (41.6 KB, 300 views)
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Old 24th October 2004, 02:08 AM   #7
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Ha, that's great!

If it's free, and it sounds good enough to listen to- the bang/buck ratio approaches infinity (forget that I mentioned that your time is worth money)

Tape is good! It looks like you could do 32 like that in a reasonable period of time.

Now you've got me thinking about another NSB line array
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Old 25th October 2004, 02:05 PM   #8
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Cool My replies

jdybnis,
How do we get the sensitivity at 1 m considering that the mentioned sensitivity is at the point of the diaphram? How much do n drivers afect the SPL capability?

joe carrow,
I intend to use a maximum of 32 drivers per side or even less,
since the drivers are not cheap. I know the critical distance for
lower frequencies will be less with 32 drivers (or less)
but will be happy with that. As far as time is concerned
I am going slow and will experiment with some cheaper drivers
to check for SPL levels (assuming I can set the SPL on cheaper
drivers to what I will get from expensive ones). I want to be sure that
it is feasible on paper at least and then venture out by spending the bucks.
Don't really wanna end with lots of drivers and nothing to do with em.

Thanks ,
Goldy
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