Dead cabinet, or fixable?

[Basstovsky]

Not sure if this is the right place to post about repairing gear but anyways here goes.

So I recently (around 3 weeks to a month ago) got an old Sunn 1x15. I don't mean a few years old, I mean OLD, I'd say late 60s to early 70s, the seller claimed 1967. I love it, it sounds huge and is a thing of beauty.

At rehearsal the other night I'm playing at my normal volume, same as always. No sign of trouble, everything sounded perfect all night, I was plugged bass straight to the amp and the amp plugged right into the one cabinet. One second normal bass tone, next nothing. No bad noise, no pop, nothing. Halfway through the song it is as if I simply stopped playing. I honestly thought a component in the amp had melted or something, until we tested and found it was the cabinet, totally silent.

I've blown a speaker or two in my time, and they all made AWFUL noises when it happened, and in one case, before it happened (before I learned the warning signs). Is there anything else that could possibly go wrong? By this I mean, am I totally screwed and have to somehow try and find another speaker that sounds this good that wont cost me an arm and a leg? Or is this repairable?

I'm decent with electronics, so I pulled out the multimeter. The wires from jack to speaker seemed to be a small gauge, so I figured they might have melted or otherwise been destroyed, as they seemed too small for speaker cable, but the meter says there's continuity from jack to speaker. I'm clueless, the only problem I have ever had is a speaker going from sounding great to making awful noises, never going completely dead silent. Help?

[s_mcsleazy]

what i would do would be change the jack on the cab and the wiring. if it still doesnt do a think then your speeker is doomed.

[xed]

Make yourself a pair of aligator clips and patch directly from quarter inch speaker cable to the speaker. Be careful. This way you will be bypassing the jack and the wiring so you will know if you have speaker or jack/wiring issues.

[lbwdog]

A driver can fail without a big announcement. Could be a number of reasons. The amp head might even be the culprit, causing the voice coil to burn up.

BTW, you didn't mention whether you:
A; tried another speaker cable.
B; tried a different head. (maybe you did imply that)

[Basstovsky]

Tried all 3. Installed new wiring from the jack to the terminals on the outside of the speaker, used a different speaker cable, and a different head. Still totally silent.

Can't tell how the terminals on the speaker actually run the signal to the speaker itself though, maybe there are other wires that could have come apart in there?

[lbwdog]

Sounds like a fried voice coil.
There is one other self test you can try. With both thumbs at either side of the cone, gently push in and let out a few times while listening with your ear very close. If you hear or feel any type of rubbing, that is a sure sign of vc failure.
Even if you hear nothing though, it could still be shot....good luck

[lbwdog]

BTW, Is it a JBL? It'll have a silver colored dome as a dust cap. If so, it might be worth it to recone just to preserve originality.

If not, I'd check the interior dimensions and port size, and replace with a proper Eminence Neo such as a Kappalite 3015 or Deltalite II 2515.

[edbass]

What does your multimeter read for DC resistance of the speaker itself?
Those old Sunn 115's came with a few different drivers depending on how old it actually is; JBL D140, Cerwin Vega, Sunn "Transducer", or Sunn "Magna". I think the Transducers were made by CTS and the Magna's were made by Sunn in their own facility.
It's probably either a Sonic I40 cab or a 115S. Does the grill come off or is the back removeable? If it's the older Sonic I40, the driver is rear loaded, it came with a D140 and the back comes off, if it's a 115S the grill comes off and the driver is front loaded. The I40 is restricted by the port ducting and will limit your options for new drivers.
If you post a pic of the cab and driver, I can probably ID it for you.
Those 115S's are pretty driver friendly, IMO JBL K140's sound the best, but I've had good luck with EV EVM's as well.

[Basstovsky]

Ok so I opened the back, pushed the cone forward and back a couple times, and I do hear it scraping against something when I push it forward.
I guess that means its toast?

The speaker has the silver dome in front, but the magnet says CTS on it, so it would be a "Transducer"?



Hard as heck to read those reflective labels, but after close examination (this was the clearest pic I could get, and this is easier to read than looking at it in person!) it appears to say
Model: 15G54L Imp: 8 Ohms Code: 74010

Also after further examination it appears that this was part of a combo with a tube amp, and the amp has been removed, a Sunn Sonaro.
It's possible this means the speaker might not be original, or came from a newer model Sunn, as the previous owner said he frequently ran it at 240 watts for long periods.

[Bill Whitehurst]

OK, it sounds like you have the dreaded voice coil drag.
I'd guess it wwent past it's Xmax and slammed the VC into the
back of the magnet, causing it to mushroom.
I killed a wonderfull Altec that way.

The CTS was a fair speaker in it's day.
Speaker technology has passd it by now, though.
I'd look into the Eminence Deltalites or Kappalites
or JBL, maybe a K140,
prehaps an M series EV.
Sucess depends on the tuning of the cabinet.

Decide if you want sensitivity, light weight, deepness or what,
then decide wich will get you where you want to go.

[Basstovsky]

Ideally I'd like to go with something similar or identical, the best would be something used in another Sunn cabinet rated for some high wattage.
Suggestions anyone?
I'd like to stay as true to the cabinet as possible, but with something that can handle up around 250-300 watts, as im looking to upgrade my amp. I have a 70s eminence in another cabinet, and it has good tone, but its just too quiet, this cabinet was at least twice as loud, seemingly with room to spare.
Maybe something I can score used from ebay?

[KramerBassFan]

Those CTS's weren't exactly the nicest thing back in the day.

I'm betting that a Beta would do just fine in there.

240w for long periods? theres your problem.

[nysbob]

Those CTS drivers were pedestrian back then, and subjecting the old guy to more power than it was ever intended to see just killed it. Just put something a little beefier in there.

[edbass]

My last post was referring to the single 15 cabs from the era, not the combo amps. Those are another thing altogether, They are much shallower (11.5" vs. 15" deep) and lack the big ducted ports of the models I mentioned earlier. I don't have any experience with that cab specifically; I’m not sure what the magic driver would be for that shallow box.

Of course you could always download WinISD and join the ranks of “instant expert” speaker designing guru’s that regularly post here…

That speaker you pictured is the correct brand, but the "Sunn Transducers" (which indeed was OEM for that amp) were labeled as such, and didn't have the CTS logo.
The Sonaro was only a 40 watt amp, not to infer any sonic comparison but sort of a “Sunn portaflex”, and didn't really need a real burly driver.
As nysbob mentions CTS were “pedestrian” not great, not crap, not in the same league as the premium drivers of the day but serviceable for a lot of applications and reasonably priced.
You pretty much got what you paid for, kind of the Eminence of their era, which is not too surprising since Eminence was founded by Bob Gault and Paul Lovegren, who were CTS employees.

[Basstovsky]

40 watts? eesh thats not much. Well guess I'll just go full bore and get something ridiculously beefy rather than original.
Found a guy selling some Gauss 15"ers on ebay that are rated for 400 watts, and it just so happens that my amp gets 400 watts if im putting it into 4 ohms rather than 8....