Wiring a 410 cab in stereo as 2: 210 cabs

[Barefoot greg]

Hey folks,
I've got an old 410 cab, each speaker is 200 watts 8 ohm, wired series parallel, making the total 800 watts 8 ohm.

I'm thinking about wiring it as 2 210 cabs sides Left and Right, wired in Series would make 400 watts 4 ohms per side.

WHY: I've got an old Marshall 3540 head, 2: 200 watt amps inside and only one cab, if I'm only running one cab I'm only using one of the amps.
If I wire the cab in stereo I can run both of the amps and use the full power of the amp/ -and have a load hooked up to both amps to protect the amps.

My main concern is if I do this, and then later acquire another cab and wire it in stereo, when I go to run both (essentially 4:210s) will my overall impedance be too low?
The Marshall 3540 has 2 outputs on ch A and 2 on ch B so I can hook up 4 cabs with out daisy chaining, but idk what that will do to the overall ohms.

Thanks in advance

 

[Bass_Pounder]

First big question - does the cab have dividers inside it ?

If all 4 speakers share the same airspace inside the cab, then you CANNOT make it two separate 2X10's.

 

[Old Garage-Bander]

First big question - does the cab have dividers inside it ?

If all 4 speakers share the same airspace inside the cab, then you CANNOT make it two separate 2X10's.

"Cannot"? or should not?
Of course he can. It is physically and technically possible to do what is proposed.
Perhaps rather than tell someone what they "cannot" do something would it not be better to tell them why they should not do it?

Each of the four speakers in the cab are 8 Ohms. You want to dedicate 2 of the speakers to channel A and the other two to channel B. With two 8 Ohm speakers, your options are to wire them in parallel which gives you 4 Ohms, or wire in series and then you have 16 Ohms.

The amp is rated for 200 watts per channel with a 4 Ohm load.
Wiring two speakers in parallel gives you 4 Ohms so you'll be loading each channel to give you the full output already with the one cab as you described.
You will not be able to add another two channel (not stereo) cab to this set up.

The difference between stereo and two channel operation is that "stereo" or stereophonic sound implies that the audio is different in each side. Two channel, which is what you are doing can be stereo or it can simply carry two mono signals that are the same.

I assume the the concern raised about electrically splitting a cab that has all drivers in the same air space was about sending a stereo (two different audio signals) into the same air space which could cause some funny interactions between drivers.
However, assuming that you intend to send the same signal to all of the speakers, this would be less of a concern as the speakers are all doing the same thing at the same time.

I don't see the harm in trying what you propose. Just be CAREFULL that when you re-wire the cabinet, all four speakers are in phase.

If it comes down to needing to be louder, you'll have to revisit what you've done to the cab wiring.
With four 8 Ohm speakers, you cannot get the cab down to 4 Ohms. Your impedance options are 32, 8 and 2 ohms.
But running two cabs like you have at 8 Ohms on each channel will be louder than running your split cab at 4 Ohms per channel. And if you needed crazy loud you can still add another 4x, 8 Ohm cab to each channel.

 

[BassmanPaul]

Sorry OGB but I do see problems. if the cabinet has one airspace, driving a pair with a signal will have the other pair acting as passive radiators. That will blow any hope of tuning the cabinet. Driver damage is almost certain to occur.

If the air space is divided into two then driving the two drivers in each airspace is possible. If the divider is vertical then the OP’s wish for a left and right is doable. If it is horizontal then the OP is limited to top and bottom.

Electrically what you say is right. The OP gets either 16Ω or 4Ω per section. Should the need arise where one amp has to drive both sections then the cabinet will be seen as 8Ω, series connected, or 2Ω for parallel.

 

[Old Garage-Bander]

Sorry OGB but I do see problems. if the cabinet has one airspace, driving a pair with a signal will have the other pair acting as passive radiators. That will blow any hope of tuning the cabinet. Driver damage is almost certain to occur.

If the air space is divided into two then driving the two drivers in each airspace is possible. If the divider is vertical then the OP’s wish for a left and right is doable. If it is horizontal then the OP is limited to top and bottom.

Electrically what you say is right. The OP gets either 16Ω or 4Ω per section. Should the need arise where one amp has to drive both sections then the cabinet will be seen as 8Ω, series connected, or 2Ω for parallel.

Yes, you are correct that if he only drives two of the four speakers that could be problematic.
Everything I said was based on the assumption that all four speakers would be in use.
Perhaps I misread the OP's intent? But I think he did say he was running both sides, one from ch A and one from B.
Running only half a cab makes no sense to me. Thus my assumptions, that was not his intent.

You also raise a good point about keeping the two sides configured so each speaker pair is physically oriented vertically rather than having one channel feeding the bottom speakers and the other feeding the top.

OP, what we are talking about is vertical dispersion of speakers. Think of your two halves as seperate cabinets.
If you were running two 2x10s, you want them standing upright, rather than laying on their sides. If they were on their sides and stacked on top of each other, one set of speakers is acoustically coupling to its environment differently than the top pair. Vertical orientation has both cabs, or both sides of your split cab coupling in the same way.

 

[BassmanPaul]

You don’t have to use both sides of your amp unless it’s tube. I often run my stereo power amps with just one cab connected. Having no load on the other will cause no harm unless, again, we are talking tubes.

 

[agedhorse]

Driving the 2 x 210's within a common airspace with signals that are not exactly t he same (ie, phase response is different because of different processing within each signal path) can seriously damage the drivers because the acoustic loading of the drivers is no longer just the airspace, but instead is the airspace modified by the actions of the other pair of drivers. At guitar frequencies, and with low compliance (stiff) speakers, it's not much of a problem, but most certainly can be for bass applicatiosn.

 

[will33]

Easy enough to do. Wouldn't require any cutting on the cab if it already has 2 input jacks.

Normally I'd say you're not going to gain anything from the extra power but I can see wanting to get 400 watts into a 410.

Yes, if they all share the same airspace you want them to receive identical signals. Meaning one preamp feeding the rig and gain (actually output voltage) matching on the 2 power amp channels.

Anything beyond that requires an internal divider, essentially making it two 210's that just happen to be transported in a single large case.

 

[Barefoot greg]

Thanks for the input so far guys.
Yeah what I wanna do is run two mono signals through each side, so it'd would be the same signal running through a vertical 210on the left and a vertical 210 on the right, no internal baffling/ or separation from one side to the other.
I could certainly see how running different signals i.e. Stereo as in a slight delay from one side to the other could could cause damage to the drivers, that's not rly what I wanna do.
My main goal is to be able to tap into all that my amp can put out, which I can't do with one cab as it's set up currently. Adding another 410 seems to be the answer, but these old Marshall cabs are hard to come by, not entirely, but few and far between.
I was able to locate one on music go round in Boston, MA but I live in Morristown, NY which is way up on the Canadian border so I'd be looking at shipping it which would be costly I imagine.
I eventually wanted to have a dual 410 set up but I was hoping that I could wire this cab up as ch a and B until the day came when I got another cab, but if I do, and I get another cab it sounds like I'd be rewiring it back to the original set up, so I better just leave it alone.

I have other amps and cabs, this is kind of a side project, so I guess I'll just have to back burner it until I can get another matching cab.

 

[Old Garage-Bander]

Thanks for the input so far guys.
Yeah what I wanna do is run two mono signals through each side, so it'd would be the same signal running through a vertical 210on the left and a vertical 210 on the right, no internal baffling/ or separation from one side to the other.
I could certainly see how running different signals i.e. Stereo as in a slight delay from one side to the other could could cause damage to the drivers, that's not rly what I wanna do.
My main goal is to be able to tap into all that my amp can put out, which I can't do with one cab as it's set up currently. Adding another 410 seems to be the answer, but these old Marshall cabs are hard to come by, not entirely, but few and far between.
I was able to locate one on music go round in Boston, MA but I live in Morristown, NY which is way up on the Canadian border so I'd be looking at shipping it which would be costly I imagine.
I eventually wanted to have a dual 410 set up but I was hoping that I could wire this cab up as ch a and B until the day came when I got another cab, but if I do, and I get another cab it sounds like I'd be rewiring it back to the original set up, so I better just leave it alone.

I have other amps and cabs, this is kind of a side project, so I guess I'll just have to back burner it until I can get another matching cab.

The nice thing about a 2 ch amp is that it increases the potential combinations of cabs by a significant amount.
Have fun.

 

[Gizmot]

First big question - does the cab have dividers inside it ?

If all 4 speakers share the same airspace inside the cab, then you CANNOT make it two separate 2X10's.

Why not run two amp channels into an enclosure ? As long as you don't run a stereo signal - which usually involves some time delays and /or phasing problems - it should work out okay acoustically.

Of course, using two amp channels will only get another 3 dB of output which isn't all that much

 

[Barefoot greg]

What about bridging this amp to get 400 watts into 4 ohms? Is that possible with this old beast? It's a Marshall 3540.
I realize I'm going into an 8ohm cab so I'm going to only see about 200 watts but that's better than 200 at 4 ohms into an 8 ohm cab and only seeing about 100. Since I'm just running the one cab currently.
Maybe getting a 115 cab to pair and bi-amping is the way to go, I know I'll catch some flack for that set up what with different size drivers and sound dispersion, speaker recovery time/ evil bass gremlin hoo-doo, but then I could dedicate one of the amps to LOWS and one to HIGHS. Bi-amping is kinda yesterday's thing but so is this amp.

Or perhaps just getting a second 410 and run full range.

 

[chadds]

That cab might not give you what you want sound wise by adding more watts. When cranked it could distort more easily and/or lose the tonal balance you're used to. That's an unknown. Two cabs would duplicate your present sound only louder. That's a known.