Re: Why Do TEF Systems read 3-5 dB high ?
Ivan,
I have assumed the old standards I grew up with, JBL and Electro-Voice to have “proper” half space measurements, as their charts agree well to real world testing.
I applaud DSL for giving phase and impedance charts in addition to frequency response charts. I had also assumed, until recent close inspection and comparison, that DSL would also be among the “old standards” where what you see is what you get (if you can see beyond marketing hype).
That said, the fact that a DSL cabinet when measured against an EV cabinet using TEF shows the DSL relative reading 3 dB lower than the published chart spec makes me wonder why that should be so.
The fact that B&C publishes an Ap graph showing a sensitivity of around 95 dB for their BC18SW115, which agrees with their cabinet simulation, then posts a TEF reading that is about 3 dB higher also makes me wonder why.
The fact they rate the same speaker as 97 dB sensitivity when it only reaches that level at about 1200 Hz simply annoys me, but such is the world of marketing.
Everyone knows if you are worried about 3 dB, you don’t have enough “rig for the gig”, but a 3 dB rated difference in sensitivity turning out to be the same is the same as if you looked at a car’s specifications and one is rated for 15 MPG (miles per gallon, your milage may vary..), another 30 MPG, then you find they actually get the same MPG.
The fact my Mustang gets about 25 MPG instead of it's 28 MPG rating can easily be explained by my lead foot and local mountainous conditions.
If it only got 14 MPG, I would wonder why .
Still hoping you (or anyone else reading this) will do a side by side half space comparison of a DSL sub to some other “old standard” to double check my observations.
Art Welter
