Compression driver sensitivity

[Sanon]

I have a compression driver which shows a sensitivity of 105dB 1W/1M in range of 500Hz to 7Khz. It has 53mm coil , I am interested in 2.5KHz to 4KHz region .

please advise me can I increase its sensitivity with a different coil? , what are the rules to do this .

Thanks

[AndrewT]

Hi,
you must keep the same coil dimensions. That is all that will fit in the magnetic gap.
If the existing wire is round then square wire or rectangular wire may allow a little more copper in the gap.
That gives some flexibility in how you proportion the copper volume between length and cross sectional area.
More turns in the gap at the same cross-sectional area will increase sensitivity, if the weight of the coil remains the same.
A lighter dome and coil assembly should also give a change in sensitivity.

[Sanon]

Hi , Thanks for the info , with square wire of triangle what is the guess estimage of increase in dB. Can the diaphragm material enhance the sensitivity 2.5KHz to 4KHz .

Thanks

[head_unit]

It is rather hard to answer your true question. Can you explain more what you are trying to do? WHY 2.5-4k? What is the application? What horn are you using?

A lighter compression driver may increase sensitivity, but at the expense of higher break-up distortion or possibly failure.

Changing the coil on an existing compression driver would be extremely difficult to say the least. And even if you can do it, there are always tradeoffs. If you used rectangular wire to squeeze more turns into the gap for the same resistance, the coil length becomes less and you have less excursion = lower output level. If you then lengthen the coil to regain the excursion, the resistance goes up so your voltage sensitivity goes down. The shape of the magnetic field modifies everything I just said.

--> sorry, there is no magic solution, only tradeoffs
...which is true of anything to do with speakers!

P.S. When you say your driver is 105 dB, how was that measured? On a plane wave tube? On a particular horn?

[AndrewT]

Originally Posted by head_unit

If you used rectangular wire to squeeze more turns into the gap for the same resistance, the coil length becomes less and you have less excursion = lower output level. If you then lengthen the coil to regain the excursion, the resistance goes up so your voltage sensitivity goes down.

this disagrees with what I posted.
Have I got it wrong?

[dirkwright]

Buy a different driver. That's the easiest thing to do.

[Sanon]

Originally Posted by head_unit

Can you explain more what you are trying to do? WHY 2.5-4k? What is the application? What horn are you using??

Its a siren .

Originally Posted by head_unit

-> sorry, there is no magic solution, only tradeoffs
...which is true of anything to do with speakers!
P.S. When you say your driver is 105 dB, how was that measured? On a plane wave tube? On a particular horn?

Its 105dB with 18 Inch horn flare. I was thinking that maybe if in my application as the frequencies below 2KHz and above 4KHz is never going come . Therefore I could go in with lighter diaphragm material , to sacrifice that frequency range .

Thanks

[Sanon]

Originally Posted by dirkwright

Buy a different driver. That's the easiest thing to do.

I was looking for 115dB sensitivity or more on CD 90/75 horn. But most of the mid range drivers are 105dB to 110dB at the most .

[dirkwright]

Originally Posted by Sanon

Its a siren .

Thanks

Here you go:
Niterider Modular 115db Siren

[wg_ski]

Higher sensitivity can be gained by using a tighter pattern horn, not by modifying the driver. Of course, this puts more sound on axis and less everywhere else. The highest I've ever seen are 114dB/m/W on a 20x40 for a 50mm exit with a 100mm coil.

If you really only need a narrow bandwidth, you could design a band pass filter (ie, crossover) with 3dB or so bandpass gain which will boost the output in exchange for a lower Zin.