Design factors impacting sensativity

[robertbartsch]

Ok, so I'm a fan of effeciency and dynamic range.

After pulling an blown Altec fram and comparing it to a modern JBL I got to thinking about the various design factors that might impact sensativity.

Here is my list, so far:

1. Motor strength
2. Voice coil gap
3. Diaphragm construction/weight
4. Amount of VC wire in gap
5. Surround construction (aluminum, Ti, mylar, etc)
6. VC wire (flat vs round, aluminum, vs. copper)
7. VC diameter
8. Throat and horn design

Are there other factors I missed or are these correct?

I can also observe that the factory sensativity ratings are not always indicative of what you might expect in listening tests.

[Beowulf57]

Just a small note: sensitivity and efficiency are not the same thing:http://www.sengpielaudio.com/calculator-efficiency.htm (http://www.sengpielaudio.com/calculator-efficiency.htm)

For example 100% efficiency equals 132dB/w/m whereas 12.6% efficiency equals 103dB/w/m.

I don't know if this is relevant to your question, but it may be.

[ratitifb]

I can also observe that the factory sensativity ratings are not always indicative of what you might expect in listening tests.measurement conditions vs Room acoustics :blah:

[toddalin]

Internal dampening due to the type and placement (and condition) of the foam padding?

[Hoerninger]

Collecting parameters alone is not helpful, they should be independent from each other.
Two examples for efficiency:

no := power(2*pi,2)/power(c,3)*power(fres,3)/Qe*Vas;
no := rho*power(Sd*Bxl,2)/(power(Mms,2)*2*pi*c*Re)
____________
Peter

[Ian Mackenzie]

Ok, so I'm a fan of effeciency and dynamic range.

After pulling an blown Altec fram and comparing it to a modern JBL I got to thinking about the various design factors that might impact sensativity.

Here is my list, so far:

1. Motor strength
2. Voice coil gap
3. Diaphragm construction/weight
4. Amount of VC wire in gap
5. Surround construction (aluminum, Ti, mylar, etc)
6. VC wire (flat vs round, aluminum, vs. copper)
7. VC diameter
8. Throat and horn design

Are there other factors I missed or are these correct?

I can also observe that the factory sensativity ratings are not always indicative of what you might expect in listening tests.

Agreed,

There is where Altec part ways.

Typically the sensitivity is measured over a defined range and JBL are at pains to advise in their literature that there drivers are not just measured over a mid range bandwidth if you look at the product data sheets.

I will probably get flamed for this but Altex loved to market very high sensitivity up around 100 - 103 db for some of their drivers and systems. But on paper (years later) this is only the peak response of a the driver which might be at 2 kertz as if often the case with very low Q drivers with light weight cones.

Therefore you have to ask what is the mean or useable sensitivity?

It might only be in the mid 90's and with relatively limited power handling you can see why JBL are still around.