There's lots of smart guys on this forum and some dudes that are educated in electronics, engineering, etc. So while there are text book answers, much of what we also rely on this forum is anecdotal information on what works and what doesn't. It's great to see the conversation expanding here recently so lets talk speaker sensitivity and speaker impedance. A typical question I've seen is what's better a 2ohm speaker of 4ohm speaker? For the smart guys out there, I'd love to read a good breakdown (in "biker" language) the correlation between sensitivity and impedance. For those not having a clue what does what that would be a good start and here's the discussion question:

What would play louder:

Speaker A - 4 ohm, 92db @ 100w
Speaker B - 8 ohm, 95db @ 50w

 

OK Professor Haze, I'll give it a try...umm.. speaker A being 4 ohm has less resistance than speaker B. Speaker B having a higher sensitivity rating is more efficient (gets louder easier). When your measuring SPL every 3 db doubles in sound volume. I'm not sure about db when relating to sensitivity, I doubt a speakers volume would double with a 3 db higher sensitivity rating, but I could be wrong there. Since speaker A has lower resistance and more wattage I would think speaker A would be louder, but I'm not sure if 3 db in sensitivity would make up for the lower resistance and higher power. In school I always liked multiple choice because even if you did not read your assignment (homework sucks) you still could guess at the answer. I always took speaker sensitivity ratings with a grain of salt because you never knew how the sensitivity rating was achieved, what frequency or voltage did the manufacturer measure the sensitivity at ect. Anyway my choice (guess) would be speaker A. The dude from Arkansas with the red Boar in his avitar (sorry I don't remember his forum name) (Wevsspot) just had a post where he said CDT speakers were rated correctly. whew! I also want to ad that it could be a "trick" question and they could be the same!

 

Mike, that's the discussion I'm hoping for! 3db difference and twice (or half) the power to achieve the "same" volume.

I honestly don't know in practical application, but figure it's a good topic to discuss instead of sticking to speaker brands!!

 

Bottom line for audio is it takes a high current amp to make clear bass. A 4 ohm speaker requires more amperage to get the same volume as an 8 ohm but if the amp has the guts it will not distort as much. My 2 cents.

 

Actually a 4 ohm speaker takes less watt's (rms) to obtain the same volume than an 8 ohm speaker. to put it another way if you put 100 watt rms amp to a 4 and 8 ohm speaker the 4 ohm speaker will play louder, less resistance = more volume. I also did a little research and see that ...3 db = twice the power...6db=twice the amplitude...10 db = twice the perceived volume (loudness to the human ear) ok!

 

I found this by doing a search. I read it and I now feel as if I stayed at a Holiday Inn Express last night.

http://www.audioholics.com/loudspeak...er-sensitivity

 

That's a pretty easy to follow read. Now we need it in biker translation!

I'm under the understanding that two speakers one with - 3d sensitivity will require twice the power to reach the same volume as the other. So if you want to increase volume you either need to double the power, change speakers to ones that 3db higher or even better........add another speaker!

So theoretically the two speakers above would play at the same volume? I can tell you that my PA speakers in my fairing at 97db are easily 3x louder with less power than my coaxial 6.5 or 6X9's at 92db. But this is also apples and oranges as one set is a pa driver and the other a coaxial.

 

There is a trade off between sensitivity and frequency response. Typically the louder a speaker will play the more limited it's low frequency performance will be. PA speakers will usually only be good to 100hz or so, that's why they can do 97db. A 2 ohm speaker will play louder per amplifier watt than a 4 ohm speaker, but the trade off is often the stability of the low frequency cone response. When watts were expensive lower impedance speakers made sense, but today amplifiers of even modest cost can provide enough to power to achieve ear bleeding levels with most any 4 ohm speaker. If your amp can do 150 (or so) watts into 4 ohms you really don't need to go with a lower impedance speaker, that is more than enough!