A Question on Speaker Driver Efficiency

@ toddalin

The industry standard for as long as I can remember relies on a fixed voltage to assess a loudspeaker's sensitivity - not power input. In this way, it doesn't matter what the loudspeaker's impedance is. All are judged on the same level playing field. No one has to adjust drive level to compensate for a "nominal" impedance rating. All drivers under test get the same voltage applied and no concern is paid to the current drawn - simply the acoustic output that is generated. If the driver or loudspeaker under test's efficiency is sought, then the unit of power  (watt) is a concern - not the unit of force applied (volt). If you had any electrical engineering experience, you'd know this and would stop quoting a JBL cut sheet as "your Bible".

As to the 16 ohm bit, I give up. I did my best to explain it to you and have obviously failed. Know one thing though. You aren't the only knowledgeable JBL "fanboy". I happen to be listening to a pair of 250ti Limiteds that I've had since new (1992). My first pair of speakers was the L19s I bought - probably before you were born...ugh....that hurts to say.... In any case, please take some heartfelt advice that is not meant to demean you or put you down - there is alot more to learn about electrical, acoustical, and mechanical engineering than what you will find in a JBL cut sheet. I know. Before engineering school, I studied the very same cut sheets you clearly obsess over.

The L19 made it’s debut in the 1979 catalog. Seeing as how I’ve been into JBLs since the 60’s, it sounds like you are the newcomer.

I've even developed and make products for use with classic JBLs.

https://youtu.be/pbbS0QYK2_o

http://www.audioheritage.org/photopost/data//500/medium/Resized1.jpg

http://www.audioheritage.org/photopost/data//500/medium/Tweeters1.jpg

I never said that the higher impedience meant that the speaker would have a higher Bl, but allowed for it, and showed several examples to that effect.

You’ve not shown one model that demonstrates otherwise.

As for sensitivity, you are using your definition,. and I am using mine, and both exist in many places on the internet.

How can you know that the manufacturer for the speakers from the OP isn’t using the same definition that I am using?

BTW, when someone types "You’re out of your league," this typically indicates that they are at the limits of their own understanding and just don’t want to show their ignorance by pushing it further or are too head strong to consider another point of view.

"Also, speakers with higher impedience tend to have a high Bl, and therefore follow the signal more accurately. " - toddalin

" And seeing as how JBLs are the only make of speaker that matter in my household, I stand behind the logic that a higher impedience typically leads to a higher Bl. " - toddalin

" I never said that the higher impedience meant that the speaker would have a higher Bl, but allowed for it, and showed several examples to that effect." - toddalin


Have you posted these revelations in any other forums? I'm curious what the response was. At this point, I'm starting to get embarrassed that I even responded to you in the first place - clearly, this must be your idea of a joke.  On the other hand, I suppose it is possible that you could just be utterly clueless or that you simply enjoy talking in circles.. Either way, it's a waste of my time to try to convince you of anything since you're so convinced of your special "expertise". Have a nice day!

I look at PV, Eminence, and others..., and yes, for the same models, the higer impedience version typically has the higher Bl.

So, contrary to what some would say, I guess that JBL is not the only one who does this and the OP is advised to check the specs for the selected speakers for himself.

Obviously, someone else around here hasn't even bothered to look at the various manufacture's similar offerings to confirm or deny their beliefs.

One last question for everyone...
- In parallel - each driver would move at EXACTLY the same time (pretty much)
- in series - would the second speaker in the "chain" be moving slightly behind the first speaker due to lag time through the voicecoil of the first speaker ?
- also, would one speaker be affected by the other?
- Would the human ear be able to discern this?

@williewonka , a previous answer was incorrect.

Both speakers will move at EXACTLY the same time regardless of the hookup.

Usually tube amps like higher impedances, so usually its to your advantage to put the speakers in series if you want cleaner sound. In the scenario you described though it will work fine either way if 8 ohms is your goal; two 4 ohm speakers in series or two 16 ohms speakers in parallel. You will not be able to hear any difference other than the differences that might be in the drivers themselves.

To clear up some obvious confusion on this thread, Sensitivity is a voltage measurement and efficiency is a Power measurement. Into 8 ohms both are the same, since sensitivity is 2.83 volts at one meter and that works out to 1 watt.

Into a 4 ohm load, 2.83 volts is 2 watts not 1. So the amp must make twice as much power and thus there is a 3 db increase in sensitivity (but note that the increase in volume is because the amp is making more power, not because the speaker is more efficient). The converse is true into 16 ohms- now the amp makes 1/2 watt to make 2.83 volts so the sensitivity is 3 db less.

So if you have a 97 db 1 watt/1 meter 8 ohm driver, two in series will have the same efficiency (since each is absorbing 1/2 watt) while the sensitivity is 94 db. If you put the two drivers in parallel for a 4 ohm load, the efficiency is the same as 1/2 is absorbed by each driver if 1 watt is applied. However the sensitivity is now 100db.

The trick is that you are using a tube amp and since they can't double power as impedance is cut in half, the efficiency spec is easier to use since it tells you how loud the speaker will play with your amp.