speaker ohms

jimistone

jimistone

long standing member
Ok, I have a real old altec 4/12 cabinet...very well made out of a good grade plywood and 2×4 bracing. All the speakers ended up with tears in the baskets (they were like that when I aquired it) but I fixed them with fingernail polish and they sound really good. They are old and unlabeled. I'm assuming they are altecs and original to the cab but I dunno. I also assume the are 16 ohm but again I dunno.

How do you check a speakers ohms?

Also, what would you want the ohms to be for the total speaker load on a 4/12 cab...4 ohms or 8 ohms?

I'm thinking 4 ohms because I doubt I will ever hook two 4/12 cabs together but what do yall think?
 
jimistone said:
Ok, I have a real old altec 4/12 cabinet...very well made out of a good grade plywood and 2×4 bracing. All the speakers ended up with tears in the baskets (they were like that when I aquired it) but I fixed them with fingernail polish and they sound really good. They are old and unlabeled. I'm assuming they are altecs and original to the cab but I dunno. I also assume the are 16 ohm but again I dunno.
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What BSG said. Measure DC resistance with a meter. My experience is the same as BSGs, in that resistance always reads about 3/4 of what it should be.
If you have reference speaker of known impedance for comparison, that could help.

jimistone said:
Also, what would you want the ohms to be for the total speaker load on a 4/12 cab...4 ohms or 8 ohms?
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That just depends on your amps/additional cabs, and what you want, really.
 
Get a meter and read the resistance of the input of the cabinet. (You would have to unhook an individual speaker to measure it)

As BSG pointed out, the DC resistance will be a certain percentage below the impedance. So if you get 6 ohms, the impedance is 8. If you get 10 ohms, the cabinet is 16 ohms.
 
the cabinet doesn't have any speakers in it now. I have one speaker in a homemade cab and the other 3 are in storage. I'm also thinking about maybe getting new speakers for it.
 
Ultimately, the cabinet impedance really doesn't matter until you match it up with something. There is no advantage to having a 4 ohm cabinet instead of an 8 ohm cabinet, other than being able to hook two 8 ohm cabs to an amp.

Hell, all the old marshall cabs from the 70s and 80s were 16 ohms.
 
Make it 16 ohms. You say you don't want to run multiple cabs, but you might one day, and if your cab is 4 ohms you're shit out of luck unless your amp has 2 ohm tap.

Four 16 ohm speakers wired series/parallel makes a 16 ohm cab.
 
FWIW, all of my Marshall cabs are 16 ohm mono, and I've wired them with parallel jacks. I just link the cabs together. I can run four 16 ohm cabs which presents a 4 ohm load to the head. No problem.
 
I did some investigating on the net as to what kind of speakers I actually have. They are Rola-Celestian speakers from 1976. They are 8 ohm. It's marked on the magnet and plain as day after I took another closer look at one.
 
jimistone said:
I did some investigating on the net as to what kind of speakers I actually have. They are Rola-Celestian speakers from 1976. They are 8 ohm. It's marked on the magnet and plain as day after I took another closer look at one.
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Those could be very good. What model? Blackbacks?
 
Greg, as you know I'll be looking into building cab later in the year but I'm both skint (just bought a new surfboard) and tight fisted (welsh).

I currently have a 16 Ohm V30 which I'd like to carry on using, but would probably match this with a different speaker for a bit of a tone option.

Here's the rear pannel:
https://www.blackstaramps.com/img/products/ht-venue-series/ht-studio-20h-rear-panel-large.jpg

Would I be able to get another 16 Ohm speaker to pair up with my V30 and have it work with my amp? I will probably trade it in for the head version as I should be able to do this cheaply trading a combo for a head.

In the longer term I am looking at one of these:
http://www.themusiczoo.com/images/6-18-14/21555_V30_The_Countess_Head_a.jpg although I've not had the chance to fully test one yet.

Would this work with a 2x12 with a pair of 16 Ohm speakers in.
 
JDOD said:
Greg, as you know I'll be looking into building cab later in the year but I'm both skint (just bought a new surfboard) and tight fisted (welsh).

I currently have a 16 Ohm V30 which I'd like to carry on using, but would probably match this with a different speaker for a bit of a tone option.

Here's the rear pannel:
https://www.blackstaramps.com/img/products/ht-venue-series/ht-studio-20h-rear-panel-large.jpg

Would I be able to get another 16 Ohm speaker to pair up with my V30 and have it work with my amp? I will probably trade it in for the head version as I should be able to do this cheaply trading a combo for a head.

In the longer term I am looking at one of these:
http://www.themusiczoo.com/images/6-18-14/21555_V30_The_Countess_Head_a.jpg although I've not had the chance to fully test one yet.

Would this work with a 2x12 with a pair of 16 Ohm speakers in.
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Yes, you could use either amp with two 16 ohm speakers.

There are basically three ways you can use two 16 ohm speakers in a 2x12 cab. Keep in mind you need to match the cab's rating to the amp's output taps.

1) Wire them in series for a 32 ohm load. 16 + 16 = 32. This is not a practical option. You do not have a 32 ohm load tap on the amp, so forget this one.

2) Wire them parallel for an 8 ohm load. 16 / 2 = 8. This the most common setup and you'd plug it to one of the 8 ohm taps on the head. Both speakers will be on at all times. Make sure the speakers are wired in phase, meaning, positive to positive, negative to negative. You don't want one speaker jumping out and one jumping in at the same time.

3) Wire each speaker individually in the 2x12 using two separate mono jacks. This will give you two 1x12 16 ohm loads in the same box with independent jacks. You can pick and choose which speaker you'd wanna use by choosing the corresponding jack and plug it into the 16 ohm tap on the head. Then you can add a switchable third jack in parallel to combine the speakers together for an 8 ohm load. To use the speakers together you'd have to plug into the 8 ohm jack on the head. Again make sure they are in phase. This is trickier and goofier, and I see no real reason to do this option, but what the hell? It can be done.

So there are your options with two 16 ohm speakers. Option #2 is probably the best way to go.

Have a look and study this:
Jumbo Sunshade - Speaker Wiring Diagrams
 
Awesome. Cheers.

Jimi, apologies for the minor hijack but I thought it was relevant
 
Greg_L said:
I can't see the pics because I'm not a member there.

This site is pretty useful for vintage Celestion speakers. Magnet codes and cone codes explained.
Information Menu Page - Bygone Tones
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Thanks for the link.
After reading through the thread from the LPF again. I think my speaker is a Rola speaker....not a Rola Celestian. Rola bought celesion in the early 70s, but they still made their own speakers too.

Bottomline, I have one in my homemade 1/12 closed back cab and though it's not quite as loud as the fender 12s in my HRD cab, it sounds much better on crunchy rock and roll guitar sounds.
 
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