Two 4 ohm cabs, One 4 ohm head. What are my options?

Kwesi · #1 12-02-2011, 12:59 AM

I did a search and saw a few mentions of a serial splitter cable/box which would run two 4 ohm cabs at 8 (instead of 2) so that I could run them safely on a 4 ohm head. Firstly, where can I get one and secondly, would there be much difference in perceived loudness coming from a single 4 ohm cab? The two cabs I'm trying to run are identical 210s and my current cab is a 410. I just want to know how much volume I should expect to lose if any.

To those who will inevitably suggest it, I'm not getting a 2 ohm stable head... well I would if it comes in at a size similar to a Markbass F500 and sounds about the same.

tom once dead · #2 12-02-2011, 01:19 AM

I know you can get (I forget what the brand is) Hot boxes, which were designed so that you could run tube amps at full master getting the tube dist. but you can set the volume that comes out of the cab on the box. It went in between your head and cab. From memory the one we had at my old job was around $500 (So in a US store it would be around 250 roughly).

It had switchable input and output ohm settings, so one of those might work.

**Rune Bivrin** · #3 12-02-2011, 01:27 AM

You'll get half the power and twice the surface area which should about even out things. The benefit would be more headroom before the speakers fart out.

Avezzano · #4 12-02-2011, 01:36 AM

1) from the output socket of the head, connect the center wire (or +1, wathever is indicated on the speakon) to the "+" of first cab (center lead or +1)

2) connect the "-" in output from the first cab (or -1) to the "+" of the second cab

3) connect the "-" of the second cab to the "-" of the head. You'll have so wired in series two cabs with a few dollars without spending lots of money.

Easier done than said!!!

1n3 · #5 12-02-2011, 01:37 AM

The "hot box" sounds like a power soak; useful if you want to produce more heat and less sound. Doubt that's what you had in mind.

I don't think you don't have any external options (cable or box). Working on the assumption that both your 210s have two 8 ohm speakers wired in parallel, your option is to install a switch on each cabinet. The switch will change the wiring inside the cabinet from parallel to serial, making the cab 16 ohms. Two 16 ohm cabs in parallel is an 8 ohm load.

If you're lucky, your speakers have a jackplate with enough room to mount a switch.

As for volume loss, not enough info to say. You should lose about 3dB for the lower power, but if the new speakers are more sensitive than the old, you'd get some or all of that back. And if you stack them vertically, it might be louder to you, with one cab closer to your ear.

Quote:

Originally Posted by Rune Bivrin

You'll get half the power and twice the surface area...

No, he's going from a 410 to (2) 210s.

Edit: Avezzano's solution (just rewire the cabinets) is easier and cheaper, and so obvious, I'm embarrassed. The advantage of a switch is that you can toggle between 16 and 4 ohms. If you want the option to gig with a single 210 at 4 ohms, you could wire one with a switch, and the other permanently. But if you don't need that, just rewire them.

gumtownbassman · #6 12-02-2011, 01:40 AM

If you have a tube amp with switchable output impedance, the two cabs in series will work out OK (no gain for solidstate) to maintain maximum amp output.

Another option is to slave a second amp for the extra bin.

Last option - only plug in the top cabinet, and use the bottom one to gain speaker output more towards ear level (use as a stand).

**Rune Bivrin** · #7 12-02-2011, 01:43 AM

Quote:

Originally Posted by 1n3

No, he's going from a 410 to (2) 210s.

You mean I should actually read the entire post before replying?

BigDaddyMick · #8 12-02-2011, 01:49 AM

Quote:

Originally Posted by Avezzano

1) from the output socket of the head, connect the center wire (or +1, wathever is indicated on the speakon) to the "+" of first cab (center lead or +1)

2) connect the "-" in output from the first cab (or -1) to the "+" of the second cab

3) connect the "-" of the second cab to the "-" of the head. You'll have so wired in series two cabs with a few dollars without spending lots of money.

Easier done than said!!!

+1. Easy and cheap. That's how I like it.

gumtownbassman · #9 12-02-2011, 01:55 AM

Are you wanting to run the 4x10 with the two 2x10??
If so parallel the two 2x10 at 2 ohm and run that combined in series with the 4 ohm 4x10 will give you an 8x10 at 6 ohms.

billfitzmaurice · #10 12-02-2011, 07:06 AM

Quote:

Originally Posted by Kwesi

I did a search and saw a few mentions of a serial splitter cable/box which would run two 4 ohm cabs at 8 (instead of 2) so that I could run them safely on a 4 ohm head.

Rewire them internally in series, making each 16 ohms, then when run together you have an 8 ohm load with no messing around with external devices that offer just one more thing that can go wrong.

cchorney · #11 12-02-2011, 09:02 AM

Buy a second head of about the same power and an ab switch and run leads from the ab box to both heads, and from each head to one cab.

Or get a 2 ohm stable head.

Or run two 8 ohm cabs.

If there was an easy workaround we'd all be doing it! :-/

Crockettnj · #12 12-02-2011, 09:05 AM

Quote:

Originally Posted by billfitzmaurice

Rewire them internally in series, making each 16 ohms, then when run together you have an 8 ohm load with no messing around with external devices that offer just one more thing that can go wrong.

+1

This fellow Billfitzmaurice really knows his stuff.... I bet he'll make a name for himself one day!

dmusic148 · #13 12-02-2011, 09:15 AM

Quote:

Originally Posted by billfitzmaurice

Rewire them internally in series, making each 16 ohms, then when run together you have an 8 ohm load with no messing around with external devices that offer just one more thing that can go wrong.

Quote:

Originally Posted by Crockettnj

+1

This fellow Billfitzmaurice really knows his stuff.... I bet he'll make a name for himself one day!

+2, was going to suggest the same thing. But if you REALLY think you need to do 4 Ohms(some micro heads do benefit significantly here) it's easy to series the cabs if you have spade lug connectors on each cab. But you can still screw it up if you don't pay close attention to how you connect them.

Kwesi · #14 12-02-2011, 09:22 AM

Haha, didn't get exactly what I was looking for so let me try to explain a bit more. I have a Berg AE410 and love it but I need a smaller cab that I can just run around as opposed to lugging a 410 to even the smallest of jam sessions. I got a decent deal on two Carvin V210Ts and I'd like to have the option to run both at the same time. Ideally, I wouldn't mess around with the insides because I still want them to be 4 ohms so I can get the most from the rig/mini-rig if I decide to use one at a time. So let me change what I'm asking just a bit:

1) Where can I get a serial splitter cable/box and how much can I expect to pay?

2) In comparison to a single 4 ohm 410, how much volume loss can I expect with two 210s (8 ohm total load), if any? I think 1n3 already answered my question but it'd be nice to hear some other thoughts. I gots no amp smarts.

billfitzmaurice · #15 12-02-2011, 10:02 AM

Quote:

Originally Posted by Kwesi

I still want them to be 4 ohms so I can get the most from the rig/mini-rig if I decide to use one at a time.

Illogical. If you only need one cab then you don't 'need to get all the watts out of my amp'. If one 210 isn't enough it's not about watts, it's about excursion; you fix that by using two 210s.

Quote:

In comparison to a single 4 ohm 410, how much volume loss can I expect with two 210s (8 ohm total load), if any?

Impossible to say. Far more often than not output is restricted by driver excursion, not watts. The only way to know the answer to this question is to know the excursion capability of the drivers, along with all the rest of their T/S specs, and then software model them in the cabs they're loaded in. Or to measure it in use. Any other method is a pure guess.

Woofer · #16 12-02-2011, 10:14 AM

I don't really understand why you're making it hard on yourself, which is what it seems to me. Why not just use the Berg when you need a 410, use one of the Carvins when you only need a 210, and sell the other 210?

oldcatfish · #17 12-02-2011, 10:28 AM

Quote "I don't really understand why you're making it hard on yourself, which is what it seems to me. Why not just use the Berg when you need a 410, use one of the Carvins when you only need a 210, and sell the other 210?"

This. Or, get a power amp with to 4 ohm channels and use the line out/DI out of your bass head to drive it.

anderbass · #18 12-02-2011, 11:52 AM

Quote:

Originally Posted by Kwesi

1) Where can I get a serial splitter cable/box and how much can I expect to pay?

You can buy one here: Pro Cables N Sound Power Y cables, high quality Y cables for speaker cabs and combo amps

RickenBoogie · #19 12-02-2011, 12:09 PM

Quote:

Originally Posted by Woofer

I don't really understand why you're making it hard on yourself, which is what it seems to me. Why not just use the Berg when you need a 410, use one of the Carvins when you only need a 210, and sell the other 210?

This is the most logical answer.. Using both the 210's together is no different than using the 410 alone, AND, "getting all the watts" from your amp is moot,, as Bill already explained.

Kwesi · #20 12-02-2011, 12:32 PM

Quote:

Originally Posted by Woofer

I don't really understand why you're making it hard on yourself, which is what it seems to me. Why not just use the Berg when you need a 410, use one of the Carvins when you only need a 210, and sell the other 210?

Despite how much sense this makes I was blinded by having a two cab setup that I actually dig.