90's Ampeg 810e issues (wiring and ohms) Help needed!

[askrls]

Hello everyone!

This is my first post on talkbass, so I hope I am doing this correctly.

Here's my issue:
I bought an early 90's Ampeg 810e (version with one input jack). All the speakers are the stock 32ohm 10" drivers, so I'm assuming all 8 speakers are wired in one big parallel loop. The weird thing is it's reading at 7 ohms when I test it. I've also found that only the 4 speakers on the right side are working. The speakers on the left side move (and maybe produce some sound, it's hard to tell) but they are nowhere near as loud as the speakers on the right side.

I took all the speakers out to check the wiring and all speakers are wired in parallel. All the + are wired together down each side, and all the - are wired together down each side, but there are two extra wires:

- one jumper wire on the top 2 speakers (connecting + to - between the left and right side)
- one jumper wire on the bottom 2 speakers (connecting + to - between the left and right side)

What could be causing the cab to read at 7ohms?
Is there something going on with the way the speakers are wired?
Is it possible one of the speakers is blown and is causing these issues?
Does anyone have a proper wiring diagram for a vintage 810e (one input jack version)?

Thanks everyone! I appreciate any help you can give.

 

[Wasnex]

Hello everyone!

This is my first post on talkbass, so I hope I am doing this correctly.

Here's my issue:
I bought an early 90's Ampeg 810e (version with one input jack). All the speakers are the stock 32ohm 10" drivers, so I'm assuming all 8 speakers are wired in one big parallel loop. The weird thing is it's reading at 7 ohms when I test it. I've also found that only the 4 speakers on the right side are working. The speakers on the left side move (and maybe produce some sound, it's hard to tell) but they are nowhere near as loud as the speakers on the right side.

I took all the speakers out to check the wiring and all speakers are wired in parallel. All the + are wired together down each side, and all the - are wired together down each side, but there are two extra wires:

- one jumper wire on the top 2 speakers (connecting + to - between the left and right side)
- one jumper wire on the bottom 2 speakers (connecting + to - between the left and right side)

What could be causing the cab to read at 7ohms?
Is there something going on with the way the speakers are wired?
Is it possible one of the speakers is blown and is causing these issues?
Does anyone have a proper wiring diagram for a vintage 810e (one input jack version)?

Thanks everyone! I appreciate any help you can give.

If the cab does not have the jack panel shown below, the stock wiring is all 8 drivers in parallel.

I thought by the 90s Ampeg was using something like this for the jack panel.

Jack 1 is switching. When you insert a plug, the switch breaks the cab down into an upper 410 and a lower 410. Both 410 should be 8 ohms but the DC resistance will be lower

The cab should function as an 810 when nothing is plugged into jack 1. Jacks 2 and 3 are always in parallel.

Since only four of the 10s are working, 7 ohms DC resistance is probably in the ballpark. Weird that the cab is split left to right rather than top to bottom. This suggests it has been rewired, so maybe something was done incorrectly.

Another possibility: A few years back, it was popular to due a .5 alignment mod. The idea is to run the drivers on one side of the cab full range, and to apply a passive LPF to the other side. The intent is to reduce destructive interference across the horizontal axis. The mod involves inserting an inductor in line with half of the drivers. This serves as an LPF with 6dB/octave slope.

It's possible someone did a .5 alignment on your cab, and the inductor has now burned out. Or maybe they are still working and you can't hear the clearly because the high are missing.

IMHO pull the drivers and check them with an ohmmeter. If they all check good, check the wiring.

 

[Bassamatic]

4 x 32 OHM speakers in parallel will give you around 8 Ohms, so the 8 speakers should be about 4 Ohms. 7 Ohms is OK since impedance refers to a complex signal such as audio and not to a DC voltage from a meter and the DC resistance will usually be different than the rated impedance.

I THINK that there is a blown speaker on the "bad" that is partially open or shorted, killing most of the signal there.

To find the bad speaker I think you will need to disconnect one wire from each speaker on the "bad" side and meter them one at a time. And check all solder connections!

 

[coreyfyfe]

If the cab does not have the jack panel shown below, the stock wiring is all 8 drivers in parallel.

I thought by the 90s Ampeg was using something like this for the jack panel.

View attachment 4606690

Jack 1 is switching. When you insert a plug, the switch breaks the cab down into an upper 410 and a lower 410. Both 410 should be 8 ohms but the DC resistance will be lower

The cab should function as an 810 when nothing is plugged into jack 1. Jacks 2 and 3 are always in parallel.

Since only four of the 10s are working, 7 ohms DC resistance is probably in the ballpark. Weird that the cab is split left to right rather than top to bottom. This suggests it has been rewired, so maybe something was done incorrectly.

Another possibility: A few years back, it was popular to due a .5 alignment mod. The idea is to run the drivers on one side of the cab full range, and to apply a passive LPF to the other side. The intent is to reduce destructive interference across the horizontal axis. The mod involves inserting an inductor in line with half of the drivers. This serves as an LPF with 6dB/octave slope.

View attachment 4606699

It's possible someone did a .5 alignment on your cab, and the inductor has now burned out. Or maybe they are still working and you can't hear the clearly because the high are missing.

IMHO pull the drivers and check them with an ohmmeter. If they all check good, check the wiring.

The 2001 catalog lists the dual 810E/AV cabinets as “new” so I believe that is when they starting with the switching plates. The SLM era manual for the cab likewise has what appears to be an issue date of 2001 at the bottom.

Sales Literature and Advertisements | TalkBass.com

https://ampeg.com/pdf/SVT810EAV.pdf

The .5 alignment is an interesting suggestion. It could explain the added wiring and trouble OP is having, and certainly wouldn’t have been stock. As mentioned, stock wiring for this cab the speakers should all be in parallel.

 

[beans-on-toast]

An Ampeg 810E with eight 32 ohm speakers should be wired as below. Older cabs are connected all [+] together and connected to the jack tip, all [-] together and connected to the jack sleeve.


I would first find out what you have in the cabinet. Do this by disconnecting the wiring from each speaker and check the resistance. You should have eight 32 ohm speakers. They will read less than 32 ohms, that’s normal. The 32 ohms is what is called the nominal dc impedance. If you don’t have all 32 ohms, then there could be a serial parallel wiring in place.