Hey guys, I’m sure some of you have seen some older speakers that show an impedance of “8-16 ohms”. Some older JBLs were labeled this way, as well as some Rola and CTS speakers. The last few I’ve seen read from about 10.5 to 11-ish ohms. I haven’t seen any speakers made in the last 45 years or so that we’re both 8 and 16 ohms, and I can’t find anything about these older speakers online. What can you tell me about them?
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Speakers that are BOTH 8 and 16 ohm
- Thread starter DoctorDistorto
- Start date
I've never seen a JBL driver labeled as being '8-16Ω', but I guess I haven't seen them all in my 50+ years handling them. DC resistance, as measured with an ohmmeter, is only a portion of a driver's overall impedance, which is AC, and is a nominal rating in any case. IME, your DC resistance measurements are consistent with drivers having a 16Ω nominal impedance.
Generally speaking, dual impedance drivers, such as found in car stereo catalogs, have voice coils with dual windings that can be wired externally as parallel or series, yielding two different impedances. However, given Ohm's Law, I'm not sure how a driver could be either 8 or 16Ω; the choices should be 4Ω (for 2 x 8Ω voice coils in parallel) or 16Ω (2 x 8Ω coils in series).
Generally speaking, dual impedance drivers, such as found in car stereo catalogs, have voice coils with dual windings that can be wired externally as parallel or series, yielding two different impedances. However, given Ohm's Law, I'm not sure how a driver could be either 8 or 16Ω; the choices should be 4Ω (for 2 x 8Ω voice coils in parallel) or 16Ω (2 x 8Ω coils in series).
- Feb 12, 2006
- 61,047
- 5
- 221,002
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
The driver is either 8 or 16 ohms, not both.
To be clear, I don’t own any speakers labeled “8-16 ohms”, I’ve just seen them. I wouldn’t think they could actually be both, especially since the ones I’ve seen online are said to read between 10.5-11 ohms. I would guess that, since amplifiers are tolerant (to a point) of a slight impedance mismatch that some companies tried to simplify supply by producing some drivers that were close enough to 8 and 16 ohms to be “OK” in most amps. That’s just my guess.
I just read this from an Audioheritage.org thread from a guy asking about a JBL D-130F labeled 8-16 ohms. Posted by hapy._.face:
“JBL put 8 ohm on the foilcal and it would test for an 8 ohm speaker. JBL would put 16 ohm on the foilcal and they still test out as an 8 ohm speaker! So JBL just cut the crap and started putting 8-16 ohm on them. In short- they are all 8 OHM speakers.
With regard to D123/D130's:
While we did maintain pretty tight tolerances, our 16 ohm speakers were really about 8 ohms and our 32 ohm speakers were closer to 16 ohm. Why? To make them a little louder. Remember, these were tube amps we were feeding. If you have a big hunk of iron for a transformer, tube amps are a little less fussy about lower impedance loads. Later, JBL just added "8 - 16 Ohms" on the label.”
“JBL put 8 ohm on the foilcal and it would test for an 8 ohm speaker. JBL would put 16 ohm on the foilcal and they still test out as an 8 ohm speaker! So JBL just cut the crap and started putting 8-16 ohm on them. In short- they are all 8 OHM speakers.
With regard to D123/D130's:
While we did maintain pretty tight tolerances, our 16 ohm speakers were really about 8 ohms and our 32 ohm speakers were closer to 16 ohm. Why? To make them a little louder. Remember, these were tube amps we were feeding. If you have a big hunk of iron for a transformer, tube amps are a little less fussy about lower impedance loads. Later, JBL just added "8 - 16 Ohms" on the label.”
- Feb 12, 2006
- 61,047
- 5
- 221,002
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
That would have been when amps were more forgiving and used for playback applications
