12 Ω speaker?

Jerry Overstreet · Post by **Jerry Overstreet** » 27 Mar 2023 11:18 am

I just picked up a spare speaker for the old Silvertone. The seller quoted it as 12 ohms. Must be odd duck. It measures about 7.5 DC resistance, maybe a little bit less.

Most of the speakers I've seen are 4,8 or 16Ω or the rare occasional 2Ω.

I've not heard about 12Ω guitar speakers although I suppose it's possible from the olden days.

I've read that most 8 ohm speakers will measure less than 8 somewhere around 5 something to 6.5 etc.
What do you think?

Also it's an old Quincy brand alnico speaker... appears to be from the late 50s. Not familiar with the brand. Anyone got anything on them?

While I'm here, the 1482 amp has a second tap on the OT. The online info is confusing. Some say it's a 2.6Ω tap while others say it's 8Ω.

The original factory issue is a 4Ω Fisher speaker which I had reconed.

However, I've been using an 8Ω speaker in this amp for years with no apparent issues, but I've read others to say one should use the unsued tap for 8Ω speakers. I'd like to be able to use either one so is the 4 ohm tap safe for both values of speaker resistance?

Appreciate any input on any of this stuff. Thx.

Mike Marsh · Post by **Mike Marsh** » 27 Mar 2023 12:53 pm

6.5DRC is Common for an 8 Ohm Impedance. IMHE
Mike

Dave Grafe · Post by **Dave Grafe** » 27 Mar 2023 1:18 pm

The seller was mistaken, you have an 8 ohm speaker

Here is the schematic, showing the main speaker connected to the center tap of the OT. One would have to identify which terminal of the main speaker connection is the center tap before determining the impedance of the full secondary, i.e. between the OTHER main speaker connection and the extra, full secondary output.

Bill A. Moore · Post by **Bill A. Moore** » 27 Mar 2023 1:26 pm

I seen this issue discussed on other forums, here is a pic of the OT.
http://www.regiscoyne.com/silvertone148 ... 482_06.jpg

Jerry Overstreet · Post by **Jerry Overstreet** » 27 Mar 2023 1:56 pm

Thanks. That was my thought too. The seller has sold a lot of vintage speakers on the bay and seems knowledgeable concerning the specs of such. Could be he wrote 12Ω when he meant to write 12 in.

I'm sure the taps can be measured, but I just didn't want to go poking around in there with probes just yet. It might be fine as is anyway as it's been good so far.

Still interested in any input on the Quincy brand.

Thanks for the link to the definitive photo Bill.

Bill A. Moore · Post by **Bill A. Moore** » 27 Mar 2023 2:03 pm

I found this:

"DuKane was originally Operadio Mfg. Co. In 1949, they sold off the speaker division to a group of former employees, who named it Quincy Speaker mfg. Corp, which re-located to Quincy, IL. Operadio became DuKane in 1951.This timeline of events used to be posted on the DuKane website, but has since been taken down.
As far as I can determine, Quincy disappeared no later than 1968."

Jerry Overstreet · Post by **Jerry Overstreet** » 27 Mar 2023 2:10 pm

OK Thanks everybody. The RegisCoyne site also has a lot of interesting and informative information on the electronics of amps. Was not aware of the site. I am sure I will find it useful.

Jerry Overstreet · Post by **Jerry Overstreet** » 29 Mar 2023 7:29 am

However, I've been using an 8Ω speaker in this amp for years with no apparent issues, but I've read others to say one should use the unsued tap for 8Ω speakers. I'd like to be able to use either one so is the 4 ohm tap safe for either value of speaker resistance?

I've been mixing heavier loads into SS amps for a while, but this is a tube amp so I don't want to do anything to burn it up. Just not sure if it's harmful to mismatch an 8 ohm speaker in a tube amp where the factory install is 4.

Bill A. Moore · Post by **Bill A. Moore** » 29 Mar 2023 8:01 am

Jerry, we know Leo wasn't worried, as he installed a parallel aux jack. Consensus seems to be the OT in the Fenders can handle a 50% mismatch up or down. SS amps do need to stay above their minimum ohms rating, and are undamaged by an open circuit, (a killer for tube amps!)
I have a similar Airline guitar amp of that era that I have paralleled another 8 ohm speaker, and had no ill effects. (It only has an 8 ohm winding for the OT.)

Jerry Overstreet · Post by **Jerry Overstreet** » 29 Mar 2023 9:17 am

Thanks much Bill. I appreciate your knowledge and input here.

Jerry Overstreet · Post by **Jerry Overstreet** » 3 Apr 2023 8:04 pm

Let me run this by you. I was playing the old 1482 when it just shut down. I could hear the speaker, barely, if I dimed the amp and guitar. I swapped out the speaker with the same results.

After a few minutes, it was OK. In the meantime, I had pulled the back, examined the tubes for power and generally poked around, made sure the speaker wires were tight etc. The amp's original speaker is 4 ohm, but the ole Quincy currently installed is 8, but I would think that would be better.

I'm questioning using this old driver although it sounds just fine. Odd that it measures almost 8 ohms, just under say 7.5 to 7.8. Seems unusual when my other 8 ohm speaker measure between 5 something to 6.5?

I was running a distortion program on the six string from my Boss fx unit but was not leaning on it severly. Say less than half volume.

I wouldn't think this old amp would have a thermal or other protection circuit. Anyway, I wasn't driving it that hard.

I've never had this happen before with either the original speaker or the 8 ohm Boogie speaker I use sometimes.

Ken Fox serviced it in 2009 so I would think it's good.

Any thoughts?

Bill Sinclair · Post by **Bill Sinclair** » 4 Apr 2023 9:51 am

I had a similar problem caused by an intermittent connection in a 6X4 rectifier tube, like your amp uses. Might start there if you have one laying around. I don't think it has anything to do with your speaker impedance.

Stephen Cowell · Post by **Stephen Cowell** » 4 Apr 2023 9:51 am

Jerry Overstreet wrote:Let me run this by you. I was playing the old 1482 when it just shut down. I could hear the speaker, barely, if I dimed the amp and guitar. I swapped out the speaker with the same results.

Look at the final tubes while it's in failure mode... are the plates cherry-red? Danger! She's fixin' to blow. This is easier to see in a darkened room. The final bias may be off (shorting cathode cap?), or the tubes may be worn, or both. Tell for this is that it goes away after the amp cools down... transformer problems are not like this so much.

Also, speakers that read very close to nominal (e.g. 7.8 for an 8ohm) probably have toasted voice coils... you can smell this, up close.

Jerry Overstreet · Post by **Jerry Overstreet** » 4 Apr 2023 10:23 am

Thanks guys. I did a wiggle test on all the tubes even though they all were lit.

I have the original output and preamp tubes but I don't have a spare 6X4...Far as I know that one and the 6AU6 are original to the amp. I'm not even sure what a rectifier tube does. I can probably buy one somewhere though.

This old amp has a distinctive odor when powered up but I did not see or smell anything different than usual. Can't really see the plates, just the top of the base where the tubes plug in.

I was concerned about the speaker because I know a shorted one will kill the amp. If the voice coil is failing, would this be dangerous for the amp?

I guess I'll just keep an eye on it to see if it does it again. Thanks.