Adding a cab to a combo

Tonkacall · #1 08-17-2011, 04:47 AM

I have a hartke ha3500 410 combo and i want to add another 410 cab to it, but there is only one speaker output.

The current cab is 4ohms at 350watts.
The amp can also run 240 watts at 8ohm.

How if at all, can i add another cab?
And i would to keep the impedance at 4ohms i possible.

VisualShock · #2 08-17-2011, 04:56 AM

Mixing impedances with similar cabs isn't advisable, as they will receive unequal amounts of power from the amplifier.

That said, what you're trying to do isn't that feesable. To do this you would need to re-wire the internal cab to 16 ohms (not possible to wire it as 8ohms), and then add your 8ohm cab. Leaving you running at around 5 ohms.

In my personal opinion what you're aiming to do isn't really worth doing. Certain combos run at 8 ohms, and can have another 8 ohm cab added to them. Yours isn't one of them. If you're short on volume, I would suggest using a different setup. You could try and trade your combo for it's equivalent in head and cab, but making sure you have an 8ohm cab. Then you would be able to add another 8 ohm cab.

Oh, and finally: I've been on talkbass for about 3 years now, and I must say that threads similar to your question come up on an almost daily basis. Questions such as "How if at all, can i add another cab? " are Frequently Asked, and such come under "FAQ"!

fingerbun · #3 08-17-2011, 05:25 AM

There is a risk you will damage your gear while attempting this. Don't experiment unless you know what you are doing.

Tonkacall · #4 08-17-2011, 05:52 AM

I dont want to mix impedances, i want to know how to connect another cab with only one output on the amp?

And yes, i dont know what i am doing, thats why i am asking for advice before i experiment.

Matthijs · #5 08-17-2011, 05:54 AM

Another solution might be adding a 6*10 cab wired as if it was 3 4 ohm 2*10's. You can then wire the whole deal together with the 4 ohm internal cab in series/parallel and you are left with a 4 ohm resistance and balanced impedances between the cabs.

You'll end up with a lot of ten inch speakers and a lot of wiring, so you'd better know what you're doing and be sure the benefits weigh up to the cost.

The sound pressure of this rig would be impressive, the tone would be impossible to predict as you'll get all kinds of complicated interactions between the two cabs, unless you're able to build this with exactly the same speakers as the Hartke combo.

fingerbun · #6 08-17-2011, 06:01 AM

Quote:

Originally Posted by Tonkacall

I dont want to mix impedances, i want to know how to connect another cab with only one output on the amp?

And yes, i dont know what i am doing, thats why i am asking for advice before i experiment.

Sorry, no intention of telling you how to suck eggs.

You probably already know what I'm about to say, but just in case...

Mixing impedances isn't the issue. You have a head rated at 4 ohms driving a cab rated at 4 ohms. If you modify wiring or use some sort of splitter to plug in another 4 ohm cab as well, the risk is you'll give the amp a 2 ohm load which could damage it.

Matthijs · #7 08-17-2011, 06:02 AM

You maybe could do the above by buying two hartke vx410 cabs and using the speakers of one cab in a 4 ohm 2*10 cab.

You wire the internal cab and the 2*10 in series and together wire them in paralel to the vx410.

oldcatfish · #8 08-17-2011, 06:08 AM

If you really like your combo, but need more volume on occasion, there is a way to do it. Use a clean power amp with as many additional cabs as you need...going from the line out on your combo.

That being said, it would make more sense to just replace the combo with a head/cab that is more expandable.

Tonkacall · #9 08-17-2011, 06:14 AM

d at 4 ohms driving a cab rated at 4 ohms. If you modify wiring or use some sort of splitter to plug in another 4 ohm cab as well, the risk is you'll give the amp a 2 ohm load which could damage it.[/quote]

Tonkacall · #10 08-17-2011, 06:18 AM

That is what i need to know basically.
So this is no way of piggybacking another cab without rewiring anything

fingerbun · #11 08-17-2011, 06:44 AM

Quote:

Originally Posted by Tonkacall

That is what i need to know basically.
So this is no way of piggybacking another cab without rewiring anything

It is doable with minimal rewiring, exactly how much depends on the specifics of your amp. But any time you combine two speaker cabs of the same impedance they combination is going to have either double the impedance (so less volume) or half the impedance (risk of damage to amp) than the original. It depends on whether you wire them in series or parallel.

Additionally if they are mismatched speakers there are risks. If one box is less powerful it becomes a weak link and can blow if you run everything harder. And if the boxes have different characteristics the sound might be inconsistent.

If what you are after is more volume then more speaker area is the way to get that. So you could get a bigger set of speaker boxes and just use the combo as a head.

Or if it has a preamp out you can split the signal there and feed it to a second power amp and cab.

I can't see an ha3500 combo on Hartke's web site, so I can't be more specific.

Good luck.

username1 · #12 08-17-2011, 07:17 AM

GK is supposed to be coming out with powered cabs. This might be the way to go that wont affect your ohm load on your hartke.

oldcatfish · #13 08-17-2011, 11:26 AM

Quote "GK is supposed to be coming out with powered cabs. This might be the way to go that wont affect your ohm load on your hartke."

Or do what I suggested.

billfitzmaurice · #14 08-17-2011, 11:32 AM

Quote:

Originally Posted by Tonkacall

How if at all, can i add another cab?
And... keep the impedance at 4ohms

You can't. If it's not loud enough it's time for a new rig, and make sure you can drive two 4x10s with it.

Matthijs · #15 08-19-2011, 03:52 AM

Quote:

Originally Posted by billfitzmaurice

You can't. If it's not loud enough it's time for a new rig, and make sure you can drive two 4x10s with it.

I agree that's the best answer, but: won't my solution, although far fetched and highly impractical, at least work in theory? (and leave him with an extremely cool one of a kind 350 watt 10*10 rig and the need to buy a van?).

plankspanker13 · #16 08-19-2011, 04:27 AM

So many considerations, when deciding what amp to buy; what style and size of band will I play in; what will the frequency be in terms of the need to schlep stuff around, and what sort of vehicular capabilities might be limiting factors? Is there PA support involved?

The best advice is to plan for expansion, at the outset. Buy an amp that will power an 8-ohm speaker to start you with, and be able to work in a second 8-ohm speaker, when the need for loudness increases. Whether this means 1x12 to 2x12, 2x10 plus 1x15, or 4x10 to 8x10, depends on the above, and your own tastes.

rodl2005 · #17 08-19-2011, 05:29 AM

Quote:

Originally Posted by billfitzmaurice

You can't. If it's not loud enough it's time for a new rig, and make sure you can drive two 4x10s with it.

This. You can't. Not without rewiring & even then, there are far easier & no doubt cheaper options, once you sell your current rig.
If you like the sound of what you have now, there are usually plenty of inexpensive Hartke amps about 2nd hand & then u can get 2 8 ohm 4x10 cabs, for a4 ohm load

fingerbun · #18 08-19-2011, 05:31 AM

Quote:

Originally Posted by Matthijs

I agree that's the best answer, but: won't my solution, although far fetched and highly impractical, at least work in theory? (and leave him with an extremely cool one of a kind 350 watt 10*10 rig and the need to buy a van?).

I suspect not but don't have enough info to say for sure. I'm assuming a Hartke 2 by 10 will be 8 ohms cos mine is, but it's an xl.

Think you will end up with a weird impedance from 10 speakers.

bassmeknik · #19 08-19-2011, 05:51 AM

In general this idea just doesn't work price wise OR impedance wise. Get a different rig...

There are two ways you could add to your combo and maintain correct impedance, add 3 more 4-10 cabs (all must be 4 ohm) wire up a splitter box that wires the now 4 4-10 cabs in series parallel this will give you a 4 ohm load and more volume but it's now very big (16-10" speakers) and more costly than replacing your existing rig.....

Another way is to replace the speakers in your combo with ones that will allow you to have 8 ohms and then get another 8 ohm cab, these in parallel will give you your 4 ohm load but isn't much cheaper than the earlier suggestion.

For these concepts to work well you need all of the speakers in your rig to be the same type, adding to the cost.

Get a different rig.

Matthijs · #20 08-19-2011, 06:16 AM

Quote:

Originally Posted by bassmeknik

There are two ways you could add to your combo and maintain correct impedance, add 3 more 4-10 cabs (all must be 4 ohm) wire up a splitter box that wires the now 4 4-10 cabs in series parallel this will give you a 4 ohm load and more volume but it's now very big (16-10" speakers) and more costly than replacing your existing rig.....
.

What my suggestion comes down to is: you don't have to ad 3 4ohm 4*10 cabs. You can also ad one 4 ohm 2*10 in series to the combo and one 8 ohm 4*10 in parallel. Assuming the 8 ohm speakers from the hartke vx cabs are fairly similar in sound to the 16 ohm speakers in the combo, you could do that by buying two vx 410 cabs and using the speakers from one of those for a 2*10. Still a lot of speakers, but 6 less.

The easy way of wiring that would be by installing an extra extention jack in series with the speakers in the combo. You plug in the 4ohm 2*10 in that jack and the 8 ohm cab in the extention connection on the amp.