15 Inch JBL

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15 Inch JBL

Postby GaryL » Wed May 21, 2014 6:04 pm

I have a reconed 15 inch JBL that is registering about 25 ohms on a meter. I wonder if I should try it on an amp that is looking for 8 ohms? My amp repair man got the same reading I did on the speaker. Any comments would be appreciated.
GaryL
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Re: 15 Inch JBL

Postby alexjones » Wed May 21, 2014 10:17 pm

Gary,
That seems rather strange. An 8 ohm impedance speaker should have a DC resistance of around 6 ohms. I would double check your measurement. Unless you put a 32 ohm impedance speaker in there. What recone kit did you use? I am assuming the speaker is a D130 right? When you making measurements, make sure it is DC resistance and your battery in your ohmmeter is good.
Alex
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Re: 15 Inch JBL

Postby tewhite » Mon May 26, 2014 12:56 pm

Weird - I`d sure check something .. The most I`ve heard of was 16 ohms and it was usually still around
8 ohms !

.Terry
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Re: 15 Inch JBL

Postby GaryL » Tue May 27, 2014 5:55 pm

Alex and Terry,
Thanks for your posts. I did not recone this speaker and purchased it already reconed. It says 16 ohms on the speaker itself. I remember 1 measurement said around 12.3 ohms. Anyway, I'll give it another try testing with new battery.
GaryL
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Re: 15 Inch JBL

Postby alexjones » Tue May 27, 2014 7:36 pm

Gary,
12.3 ohms would make sense for a 16 ohm speaker.
Alex
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Re: 15 Inch JBL

Postby senojnad » Mon Jun 09, 2014 12:14 pm

12.3 sounds right for a 16 ohm speaker.
Just to add to the confusion -- many of the JBL D130's were marked as 16 ohms but were actually 8 ohms. Danny McKinney (Standel) told me that MOST of those marked as 16 were actually 8. The D130 in my Standel is marked as 16, but actually measures between 6 and 7, making it an 8 ohm speaker..
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Re: 15 Inch JBL

Postby GaryL » Tue Jun 10, 2014 6:25 am

My JBL is OEM marked D130F 16 ohm and was re-measured and verified as 6.8 ohms. I've been using it for several weeks with my Fender Super Champ XD head and the combination sounds great.
Thanks,
GaryL
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Re: 15 Inch JBL

Postby chanavin » Tue Jun 10, 2014 5:38 pm

Hi Guys,
Not sure how you are measuring impedance of your speakers? But if you are using a
mulitimeter, most multimeters measure resistance, not impedance.. Resistance is a, DC, 0hz frequency, measurement.
Impedance is measurement at a certain frequency, say 1 khz.. The impedance will always be higher than
the dc resistance, on speakers, as its a sum of dc resistance and AC reactance..
so its common for JBL 16 ohm (impedance) speaker to measure lower resistance
on multimeter, i think mine is about 9 ohms

I think older speakers like the JBL's were marked using Impedance, but seems like a lot of modern speakers
these day,s are using DC resistance...


Hope this doesn't muddy things up :D

Chuck H...
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Re: 15 Inch JBL

Postby lovechet » Sun Dec 31, 2017 5:16 pm

I can add to the confusion. Years ago I was looking for a 15 in 8 ohm JBL D130F on internet. When I got it the label did say D130F 8 ohm, however when I measure the DC resistance is measures 30 ohm and I know my meter is accurate, new batteries etc. I would have expected DC resistence to be something less then 8 ohm. Even if its mislabeled and is actually a 16 ohm spkr it still should measure someting less then 16 ohm. I have no idea where it came from and don't know if it ever was reconed. To me the measurement of 30 ohms resistance makes it not look like either a good 16 ohm spkr (shoud measure something less then 16), or l good 8 ohm spkr (shoud measure something less then 8). In any case I plan to try it out, however I don't dare use it as a standalone onboard spkr of my fender deluxe since the deluxe wants 8 ohms and more than 8 ohms isn't a good thing, maybe not fatal but not good. I plan to use it as an external spkr along side (parallel with) the onboard 8 ohm. In this case the resulting total load will be something less than 8 ohm and that's ok. The deluxe will stand a 2 to 1 mismatch or a 4 ohm load. I should have contacted the seller years ago but didnt. As I remember back then just after I purchased it that when I used it as a standalone spkr in an english cab I made it sounded terrible, probably due to the load on amp being greater then 8 ohm. Will report any news I find out.
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Re: 15 Inch JBL

Postby PaulBennett » Mon Jan 15, 2018 5:31 am

JBL D130 15" speakers were designed and manufactured to 16 ohms nominal impedance back in the mid 1950s when I spent $1400 paper route money for a special stereo. That was my first experience and I still have that pair in Acousticraft enclosures. I also use a D130F in my Peavy Delta Blues 115.

Voice coils used a flat ribbon wire and those speakers were state of the art. For Williamson amplifiers, they still are. Magnetics have improved since then which is about the only change in state of the art and some will ague the paper cone material is better now.

Some reconed D130 speakers don't use the flat ribbon wire and differ a bit from 16 ohms but are still revered and quite usable when used solo.

Anyone who can use a meter knows the difference between AC and DC. However impedance measurements is a mystery to many as measurements are made at different frequencies and have wild numbers near resonance and impedance is more of a chart than a number. Bottom line...making DC resistance measurements MIGHT be valuable when attempting to pair or match 2 speakers but for guitar work DC resistance of the speaker has no valid meaning.

If you want more info I took part in a technical forum sponsored by JBL in the 1980's. I don't know if that forum is still sponsored, it's back in my Windows 98 computer.
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