tiny fullrange driver array idea

[Ignite]

I was sitting listening to a pair of $20 headphones, listening to thier suprising sound quality. I got this idea:
What if I were to purchase a large amount of headphone-type drivers and make array speakers out of them? I would get reasonably good volume levels with large amounts of the drivers, and they tend to be very accurate. I would probably make dipoles and just cut the high frequencies 6db to yield fairly linear response down to the point where I'd xo to a monopole subwoofer.

This could be an inexpensive design, and although rather odd, might yield suprisingly good results.

Thoughts? Problems?

 

[Bill Fitzpatrick]

My best advise is to save your money. What you think might happen, won't.

 

[Ignite]

Why is that?
All I expect is the same sound quality but at higher volume level.

This is enticing to me because the sort of drivers found in headphones can be found as surplus at ridiculously low prices. The small drivers tend to be very accurate but incapable of any decent volume level. If i have many, volume stops being an issue.

This sort of drivers uses a very thin polypropelene film, which seems to me capable of producing a similar effect as using mylar in electrostatic speakers.

 

[cocolino]

Thoughts? Problems?

I fear those tiny drivers just won`t have enough (linear) excursion for use as ordinary speakers.
The power rating and efficiency is supposed to be veeery low too.
You would need huuuuge amounts of them to get reasonable sound presssure level.....and then it is not so cheap anymore.
Better to make an array of minimum of 3-5 inch diameter fullrange units IMHO.

 

[Ignite]

I agree, there isn't much excursion.. I'd have to cross over to bass drivers at a fairly high frequency. Many headphone manufacturers boast 115dB SPL @ 1v rms though.

I suppose finding out the actual excursion for one of these drivers would help greatly in determining the actual SPL achievable from a single driver. This appears to be somewhat difficult

 

[cocolino]

Many headphone manufacturers boast 115dB SPL @ 1v rms though.

Ignite,

Yes, but probably at 20mm ear/driver distance and only a couple of cubic cm`s of "room"-volume.
How about at 1m distance and in a normal living room?
Determing excursion first sounds like a good idea
If they are so cheap, the easiest way might be to slaughter one and to throw a look at the voice coil and the magnetic gap height. After You have seen that miniature coil, likely You`ll reject Your idea anyway, I guess

This sort of drivers uses a very thin polypropelene film, which seems to me capable of producing a similar effect as using mylar in electrostatic speakers.

And You know how big diaphragm area on electrostatics usually is. Just calculate how many of Your drivers You would need to keep up with average electrostatics diaphragm area. You`ll need
dozens of them

 

[Bill Fitzpatrick]

The 115db at 1v is measured in the ear cavity. So is the frequency response. Move is 6-10 feet away and it's a different ballgame.

Take a pair of headphones, put them on and adjust the level to your preference. Now take the headphones off and walk 8 feet away. Notice that there is no bass and practically no lower midrange. Notice too, how quiet they are. I'll bet you've already tried this. Imagine the equalization you would need to do to get them to sound flat.

So let's say you crossed to bass drivers and have equalized the headphone driver array. You still have limited SPL even with a large array. And the high end will pretty much suck unless you add a properly crossed tweeter.

You would be much better off making a two way system with an inexpensive 6" woofer and one or two small Tangband drivers. And a couple of small Tangbands would be cheap too.

Nobody is trying to keep you from experimenting but many of us know where this is going to lead. But, if you try it, let us know of the outcome.

 

[woody]

I saw a picture of a line array somewhere on the Bottlehead
web page made by Grado from there headphones. I don't
remember any comments about how it sounded.

Regards'

bob12345678

 

[cowanrg]

there have been similar designs (well, along the same philisophy anyway....) by genesis, nearfield acoustics, etc. basically, you make each driver do a little bit of work, and have a TON of drivers, so each one isnt being driven hard, and it really only has to do a tiny bit. this supposedly creates a great sound. however, i dont think it would be a good idea to use headphone drivers, they are just too small. ive seen it done with like 30 midranges. so you would almost need 300+ headphone drivers. even if each was $0.50, that's $300 for stereo in drivers. and you have NO bass interesting idea though.

 

[planet10]

John at Stryke did a similar project for PA kinda use with reasonable results and he has a little oval he sells for such beasts.

If you are interested in fidelity, you are likely to find it easier and a more sure thing to spend the money on a pair (or 4) more better drivers.

Not to say that a good line array can't be built, but an array of cheap drivers is still going to sound like the cheap driver.

dave

 

[thylantyr]

--but an array of cheap drivers is still going to sound like the
--cheap driver.

I feel vindicated. lmao

I was trying to tell someone on the other forum
that if you plan to use "cheap" drivers for the line
array make sure the individual driver has good sonics
otherwise you get a "cheap driver x 10" sound,
fuzzy math.. lol

Some argued that a cheap driver will sound just as good
as an exotic driver if you play them at low volume and
having the array will increase the SPL so the cheap driver
will yield the same results as the exotic. hehe

I had to test this out myself. The simple test was;

Stage Accompany $600 isodynamic.

vs.

Eight HiVi RT2 isodynamic ($30 each, total cost $240).

Individually, the RT2 is ok, nothing special, but
having 8 did create a big sound stage and it sounded
good and it played loud. This is a good setup considering
the cost.

But, the SA tweeter still sounded better and I thought
it gave me more impact on the high end, ie, the crash
of the cymbals, etc. Even my old lady preferred the sonics
of the SA over the RT2 array. I asked why? She said, the array
sounded like a bunch of cheap speakers playing loud - lmao...
Seriously, she said if she had never heard the SA driver,
then the RT2 array would be very acceptable because she
had no reference.

So we are comparing $240 vs. $600 solution.

Now, the million dollar question, what will an array
of $600 (each) SA drivers sound like ?

I will let you know next summer.

 

[Rarkov]

Have you heard of beaming, out of interest? It is a new technology (Patent Pending as usual). It is a panel (about the same dimensions as a plasma display, as it's designed to go below one), that uses about 200 tweeters to produce a fullrange spectrum. The panel contains a complex DSP circuit that beams the sound to each and every position in the room, as though everyone is sat in the perfect position!

Sounds fantastic...but will retail at about £9000!

Gaz

 

[planet10]

Have you heard of beaming, out of interest?.... that uses about 200 tweeters to produce a fullrange spectrum. The panel contains a complex DSP circuit that beams the sound to each and every position in the room, as though everyone is sat in the perfect position!

Isn't that the one that uses Harmon Kardon Odessy 25mm full range speakers? These are the units HK developed for Apple's use in the iMac. Apple iBall. In the picture i saw the cones were adonized a goldish color.

dave

 

[pinkmouse]

Humm, steerable arrays...

It has been used for years for military radar systems, but they only work on two or three frequencies at once. I'm not sure how it would scale up to full bandwidth audio applications, the processing power required would be immense

 

[Rarkov]

I believe it is...I can't remember if it was What HiFi or HiFi News it was in...But they wrote up a Very positive review!!!

 

[planet10]

I can't remember if it was What HiFi or HiFi News it was in...

It would be HiFi News -- i don't read What HiFi (don't see it around here often)

dave

 

[djdan]

I think that idea is not so bad, teoretichaly speaking. Think of that:
A speaker (no matter what kind ) for entire audio band (20Hz-20Khz) in hundred of pieces. No more pasive crossover . If the speaker cost is no more than 0.5$ / piece it is worth to make a test with 10 pieces to watch is happen. If it can be used coupled with an subbwoofer, maybe it is something.

 

[earwig]

for beaming speaker arrays see here
http://www.1limited.com/

 

[planet10]

Here is what those 25 mm drivers look like after someone let the smoke out and i disassembled them to see how they were constructed. JBL has a patent on them.

dave

 

[Rarkov]

earwig:
That's the one...I couldn't remember the name until I saw it in a mag yesterday (Looking back over for inspiration!).


Hope you all find it interesting...If you could manage to make something similar (maybe without so much DSP horsepower) it'd be very interesting...I looked into it at one time, but as it has been pointed out, these drivers are patented and normal tweeters take up far too much room with very little Xmax values (non existant!)

Gaz