Mixing 55hz and 75hz greenbacks

musteatbrain

Ok, I have a 1x12 and 2x12 to fill.
Thanks to Countrydave (lots of them) I have recently acquired the following

3 greenbacks
1971 T1281 G12H 55hz
1971 T1217 G12H 75hz
No date stamp but 71-73 from the format on the cone code T1281 G12H with a 102/3 cone which I think makes it 75hz, even though I thought T1281s were always 55hz
I’m happy either way

Before I get the soldering iron out, is the most logical approach to start with the 55hz in the 1x12 and the two 75hz speakers in the 2x12?

ICBM

musteatbrain said:

Before I get the soldering iron out, is the most logical approach to start with the 55hz in the 1x12 and the two 75hz speakers in the 2x12?

That's what I would do, yes.

Whether it's 'right' or not I can't say... but my logic would be that a 2x12" tends to enhance bass compared to a 1x12" with the same speakers, so you want the more 'bassy' speaker in the 1x12".

Bygone_Tones

musteatbrain said:

Ok, I have a 1x12 and 2x12 to fill.
Thanks to Countrydave (lots of them) I have recently acquired the following

3 greenbacks
1971 T1281 G12H 55hz
1971 T1217 G12H 75hz
No date stamp but 71-73 from the format on the cone code T1281 G12H with a 102/3 cone which I think makes it 75hz, even though I thought T1281s were always 55hz
I’m happy either way

Before I get the soldering iron out, is the most logical approach to start with the 55hz in the 1x12 and the two 75hz speakers in the 2x12?

Got any photos of the 102/3 stamped T1281? They did make factory mistakes like that ocassionally but it is pretty rare. I should be able to date it accuarately for you too.

musteatbrain

Here you go @Bygone_Tones ;
https://imgur.com/gallery/xwLJCZT
no other codes on it. It says made in England on the dust cap and frame just in the same place as the others with 71 date codes

musteatbrain

Unfortunately that one also appears dead. There’s no movement when I apply current to the speaker. Hmmm I’ve reached the end of my limited knowledge.
any ideas? 

ICBM

musteatbrain said:

Unfortunately that one also appears dead. There’s no movement when I apply current to the speaker. Hmmm I’ve reached the end of my limited knowledge.
any ideas? 

Check the solder connections between the terminals and the cone braids - sometimes a bit of corrosion gets in there. Meter directly onto the cone braids with a multimeter to check, but be careful not to tug on them. If you get a resistance there, resolder the terminal which is causing the trouble.

If there's no measurable resistance there, then unfortunately the voice coil is dead and the speaker will need to be re-coned.

sweepy

I’d still,like to try a cab with 10” and 12” mixed, Bognor and Matchless make cabs with mixed 12” drivers so it would be intriguing 

musteatbrain

ICBM said:

musteatbrain said:

Unfortunately that one also appears dead. There’s no movement when I apply current to the speaker. Hmmm I’ve reached the end of my limited knowledge.
any ideas? 

Check the solder connections between the terminals and the cone braids - sometimes a bit of corrosion gets in there. Meter directly onto the cone braids with a multimeter to check, but be careful not to tug on them. If you get a resistance there, resolder the terminal which is causing the trouble.

If there's no measurable resistance there, then unfortunately the voice coil is dead and the speaker will need to be re-coned.

Yep. Dead voice coil I think.
tested like this
https://imgur.com/gallery/VXB5HJo
Is it worth anything in this state?

ICBM

musteatbrain said:

Yep. Dead voice coil I think.

tested like this
https://imgur.com/gallery/VXB5HJo
Is it worth anything in this state?

Not a lot, no. The value of a reconed speaker less the cost of the recone, less a bit more for hassle factor...

Bygone_Tones

musteatbrain said:

Here you go @Bygone_Tones ;
https://imgur.com/gallery/xwLJCZT
no other codes on it. It says made in England on the dust cap and frame just in the same place as the others with 71 date codes

Looks like a recone to me. It is a pulsonic cone circa 1972, but does not look original.

Why? It looks as though the date code has been cleaned off on purpose (easily done with some acetone) . The doping is not right for a G12H (should be a wide band of welvic all around the outer edge), and the dust cap and lead wire glue on the front face of the cone do not look correct to me either. Plus the obvious 75Hz cone on a 55Hz spec speaker.

If your other two speakers are definitely original, compare with those. Visually the cone fronts should look the same.

As for being dead, check for any visible breaks first. If you can't see anything then it needs professional repair. It can be done without reconing, but is a very tedious job best left to professionals. 

Bygone_Tones

Also compare the spider supports (the brown corrugated part underneath the cone). Looks a bit different judging by the last photo you just uploaded. Another sign it is not the original cone.

musteatbrain

Thanks the other two do look a bit different and fortunately sound excellent
https://imgur.com/gallery/MdjVUHt
Worth repairing do you think?

Bygone_Tones

Financially, probably not. Personally I would just sell it as spares/repairs. Someone will buy it and repair it, but you might only get about £30 to £50 for it.

musteatbrain

Thanks
think I’ll do that then and cut my losses on this one
got 2 good ones at least

Bygone_Tones

Have you tried getting a meter reading from the front of the cone? Where the two blobs of black glue are? If you can get a reading there it might be a simple repair. You will have to scrape a bit of the glue away to access the wire of course. Be careful as the wire is very thin and fragile there, easily broken.

musteatbrain

I didn’t try that, but my friend just headed off and took the meter. I’ll give it a go in the week

musteatbrain

Still no luck with this.
Is there anyone in the uk that does this sort of repair?
Would be great if the cone could survive
http://www.merrenaudio.com/speaker_repair

Bygone_Tones

Re-wiring a voice coil is a very 'specialist' job. Most speaker repair places will just rip the cone out and fit a replacement. You could try these guys:

https://www.amp-repairs-leicester.com/contact-us/

Someone else on here recommended them, and with an email address like that he better be good

musteatbrain

Thanks. I’ll let you know how it works out