Speaker sensitivity ratings

[Wayne Firefly]

Hi, just got a cheap Peavey 1x15 cab and it works ok at the mo with a Gallien MB200 but eventually Im after changing the driver when the one in it inevitably pops its clogs.
I was having a chat with a guitarist friend who dabbles in amp building / repairs and while discussing speakers I asked about ratings etc. I understand ohmage and power handling etc but he seemed to go on about decibel ratings as being one of the most important ratings for a speaker as efficiency is paramount. Ive been looking at the usual suspects like Eminence, Fane and Celestion and checking out everything at Lean Business too.
Whats really the difference between a 96db speaker rating and a 99db ?? Is it that much different ? Tone isnt the issue here.
If so, who does 99db or higher, 15'' speakers ??
Id ideally be looking at a 15 inch, ferrite magnet, 300 watt, 8 ohm speaker, but with the most efficiency possible....
Not too assed about neo lightweight stuff, the cab is a cheapo old thing anyway, just want POWER !!!!!!!! (sorry...bit Clarkson there... ahem)

[dincz]

A difference of 3dB sounds like this:

http://www.talkbass.com/forum/attachment.php?attachmentid=315441&d=1359883572

[Wayne Firefly]

That sounds like hardly anything !!!!! I was expecting a big jump !!!!!

[Michael J]

Loudness and power etc. are compared using a logarithmic scale, +3dB = x2, +10dB = x10.

Using 96dB from 1 Watt as an example:
[b]96dB@1W[/b], 99dB@2W, 102dB@4W, 105dB@8W,
[b]106dB@10W[/b], 108dB@16W, 111dB@32W, 114dB@64W,
[b]116dB@100W[/b], 117dB@128W, 120dB@256W, 123dB@512W,
[b]126dB@1KW, ...[/b]

It makes the maths easier as you can add numbers to perform multiplications. The less efficient speaker will require twice as much power from the amplifier in order to produce the same amount of loudness as measured by a microphone. The ear is logarithmic again on top of this, +10dB only sounds about twice or maybe three times as loud...

Efficient speakers are a better bet than high-powered amplifiers. I plugged my 15W practice amp into a 4x12 cab in the local music shop - it was well loud at halfway on the volume control, from just one or two watts output through its external speaker jack socket.

[LawrenceH]

Sensitivity is important...BUT... the single number quoted by manufacturers is next to meaningless without context. What matters is the sensitivity at a given frequency, no good buying a '99dB' speaker where the spec refers to the 500-2000Hz region and it drops like a stone below this, just where you need the most power anyway. Modelling programs will tell you more about the lower range sensitivity. Worth getting into if you're going to replace a cab driver.

The other side is that higher sensitivity drivers tend to have shorter voice coils (and lower power handing), so have a lower maximum output level with respect to bass frequencies, despite an initial higher sensitivity. They run out of headroom with less watts. It's all a trade-off. Having said that, there should be plenty of 15" drivers that would meet your criteria. To choose one, you need to model them based on T/S parameters to see if they're suitable in your box, and it helps if you have an idea of your preferred tonal profile and how this relates to a plot of frequency response. There are other factors too, but these are the best places to start.

[Wayne Firefly]

Oh gawd, total can of worms thing, thrown open..........if anything, Im even more confused now about it all !!! Had to laugh fair do's !!

[Roland Rock]

Barefaced have recently changed the way the calculate their sensitivity ratings:

"With our old specs we gave low frequency (100Hz) and broadband (weighted average from 200Hz to the quoted treble roll-off point) sensitivity specs. We've decided to make things easier now and give you just the pistonic sensitivity specs (basically the 80-640Hz region) in half-space as, based on further research, testing and experience we've found they're most representative of real world use."