i recently saw a D130f that says 8-16 ohms on the label. What is this and how does it change?
thanks
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i recently saw a D130f that says 8-16 ohms on the label. What is this and how does it change?
thanks
It doesn't really mean much... it was put on them during the transition between tube amps to solid state. Tube amps were primarily designed to work best with 16 ohm loads and the newer solid state gear was designed to work best with 8 ohm loads.
JBL put the 8-16 ohm graphic on some of their speakers to let people know that they would work well with both types of amps. There were several other drivers where they simply changed the graphic from 16 ohm to 8 ohm... the driver's impedances hadn't changed, but the demands of the market place had. There has been a hell of a lot of confusion ever since.
Widget
So it is really an 8 ohm speaker?
There really is no such thing as an 8 ohm speaker... a driver's impedance changes with frequency and with the type of box it is in.
If you are designing a crossover and need specific impedance info buy a woofer tester from Parts Express... otherwise don't sweat it.
Calling a particular driver an 8 ohm unit is like calling a speaker 94dB efficient. It will likely be both of these things at some frequencies and have a much higher (like 40 ohms or more) impedance at resonance and a much lower sensitivity at lower frequencies.
Widget
Widget's right, but there's a fair span of frequency above resonance where a "nominal"
impedance can be reasonably provided so that a comparison of speaker drivers can
be made... if this span mostly doesn't fall much below 8 ohms, then I'd personally
consider it an "8 ohm" driver (as opposed to dipping to 3-4 ohms) in terms of matching
it with an amplifier that had issues supplying enough current for a "4 ohm" system.
If the driver impedance mostly was north of 12 ohms (or so) I'd probably consider it to
be a "16 ohm" driver. Attached is a plot of three 2226 drivers, specified as nominally
4, 8, and 16 ohms (0-100 ohms vertical scale, 10-1000Hz horizontal scale). The resonance
(~40Hz in this case) is shown for a -very- large box (100ft3) and will be modified by any
normal-sized box (sealed, ported, or open back), as Widget also mentioned.
Without a measurement, I'd be guessing about the driver in question...
although some folks here with more experience with dating and marking may be
able to get you what you're looking for... a -nominal- impedance.
-grumpy
We always considered the "nominal impedance" as the trough between 200 and 400 Hz. Of course, we lied back then, calling our 8 Ohm speakers "16 Ohms".
When amplifiers came out with 8 Ohm taps, the easiest course was to simply relabel the speakers "8-16 Ohms".
Hi
As an FYI, Smith & Larson Audio (makers of the original WT and WT2) stopped using PE as our distributor last year and moved over to MCM where the WT2 is known as the "Speaker Measurement Interface". We still retain the WT2 moniker for our own direct sales as well as moving forward with our newer test products.
Best regards,
Keith Larson (WtPro)
Smith & Larson Audio
www.woofertester.com
[quote=Harvey Gerst;. Of course, we lied back then, calling our 8 Ohm speakers "16 Ohms"
[SIZE=3]Does this in fact mean that most of the older alnico pro drivers marked at 16ohms actually had a nominal imp. of 8 ohms?(!) I always wondered why an LE85 was rated 8 ohms while its pro counterpart was rated 16. [/SIZE]
[quote=rich carnese;161893]I don't know about the "pro drivers", but that's the values we used in the 60's.Quote:
Originally Posted by Harvey Gerst;. Of course, we lied back then, calling our 8 Ohm speakers "16 Ohms"
[SIZE=3