500W@4Ohms + 400W@8ohms = ?

ChTBoner

ChTBoner

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Hey there W buddies!

I currently have two cabs : an EBS Neoline 210 (500W@4ohms) and TC RS210 (400W@8ohms).

If I link them, powered by my TC RH450, what will the output power?
My RH450 can support a minimum impedance of 4ohms, is the minimum impededance respected?

Thx!
 
With a 4ohm and an 8ohm, you should still be safely above the 4ohm rating of your head
 
Hi Thibault :-)
If you use them together, the impedance will be 2,6666666666666666666666666666666 which is below 4 ohms... Let's say it is not a very dangerous situation. Still, you will have more volume in the 4 ohms one, while the 8 ohms one will be quieter.

It is not a recommended setting...
 
Thanks Flo, your answer complete another good one I had on a french forum! I wont add them then.

Just a silly question, what if I had two RS210 + 1 EBS?
 
Gah, I was thinking series connection not parallel :-(
 
ChTBoner said:
Thanks Flo, your answer complete another good one I had on a french forum! I wont add them then.

Just a silly question, what if I had two RS210 + 1 EBS?
Click to expand...

Then it would be 1/8 + 1/8 + 1/4 = 1/2
Thus the answer is 2 ohms. The RH450 will not like this.

I'd skip the EBS and just stick with two 8 ohms cabs which give you a total load of 4 ohms.
 
Hi Graham, no worries, it happens to me a lot :-)
Thibault, Marco is right... If you use 2X 4ohms in series linked with the 8 ohms one in parallel, then the ohms will be OK, still I am not sure how will be the balance. I guess the best advice is to use 2X 8 ohms ...
 
Ok, I think I start to get it! (At last...)

Thanks!
 
Florin said:
Hi Thibault :-)
If you use them together, the impedance will be 2,6666666666666666666666666666666 which is below 4 ohms... Let's say it is not a very dangerous situation. Still, you will have more volume in the 4 ohms one, while the 8 ohms one will be quieter.

It is not a recommended setting...
Click to expand...
This is all correct, but it's worth noting TC say the RH450 will work fine with three of their 8ohm cabs. So that says it will actually handle a 2.666 ohm load. So your amp will be ok with the EBS 2x10 and the TC 2x10. As Florin says, the TC cab will produce less volume because it is impeding the signal more, so the EBS is taking more of the power, but both cabs will still be comfortably within their limits. And overall you will actually be milking more power from the amp then you would be by giving it a 4ohm load. Theoretically, if the RH450 were delivering 450W through a 4ohm load, then through a 2.66ohm load you'd be getting 675W. But this is a very naive theoretical calculation. In practice, the RH450 actually only delivers about 240W (Board Message), and because of the clever way it manages power, that figure might not actually change much with lower impedance load.

Okay, that's the theory. But the practical answer is:
1) it's safe - you're within the safe spec of both amp and cabs, and
2) it'll be as loud as it sounds. The numbers are irrelevant - it's how it sounds that matters!
 
Florin said:
Hi Graham, no worries, it happens to me a lot :-)
Thibault, Marco is right... If you use 2X 4ohms in series linked with the 8 ohms one in parallel, then the ohms will be OK, still I am not sure how will be the balance. I guess the best advice is to use 2X 8 ohms ...
Click to expand...
Theoretically if you use 2 x 4ohm cabs and 1 x 8ohm cab, then a 450W amp would deliver 225W to the 8ohm cab, and 112.5 to each of the 4ohm cabs.

But that is the theory, and as I said in my other post, the RH450 does not work so simply.
 
Most class D amps do not like 2 ohms. Better be careful with anything less then 4 ohms
 
Yes, I don't think the RH450 will cope with 2ohms. The manual for it says:
You can connect up to three RS cabinets or any other two 8
Ohm cabinets of another brand to the amplifier. (minimum
load: 4 Ohm).
Click to expand...
This seems to contradict itself: three RS cabs, being 8 ohms each, give a load of 2.66ohms. So if the head can cope with that, then the minimum load is not 4 ohms. The other possible conclusion is that there is something special about the RS cabs, so they have a higher impedance, at least when combined together.

There has been a lot of discussion about this on basschat.co.uk (the RH450 is quite popular there) and the conclusion most people reached was that there was nothing special about the RS cabs, so if the RH450 could cope with three RS cabs, then it could cope with three of any 8ohm cabs. If that is right, then that means it will cope with a 2.66ohm load. But of course, that does not mean it will cope with a 2ohm load. And, if you are at all paranoid, then you should probably play safe and keep to a minimum load of 4ohms.
 
the RS cabinet stuff is rather odd I will admit as well, but in doubt I would go by the 4 ohm min load that was stated on the amp
 
The 8 ohms stated on a cab is its nominal impedance. If you however chart its impedance over the frequency spectrum you will find out it widely ranges.

My guess is the RS cabs will have a gentle impedance graph while with other cabs you can't be certain. TC can't risk you blowing up their amp using random other cabs so they advice you to no take any risks wit unknown cabs.
 
mart said:
Theoretically if you use 2 x 4ohm cabs and 1 x 8ohm cab, then a 450W amp would deliver 225W to the 8ohm cab, and 112.5 to each of the 4ohm cabs.

But that is the theory, and as I said in my other post, the RH450 does not work so simply.
Click to expand...

How do you calculate the distribution of watts in mismatched cabs?

on a side note how awesome would it be if someone whipped up a little online calculator where you put in the nominal impedance of the cabs, the amp's power outputs and how you want to wire it and it spits out total and side chain impedance, power output and power distribution? it couldn't be that hard to do surely?
 
I say keep it simple and use either two 8 ohm cabs or one 4 ohm cab. Stay away from mixing different impedance cabinets alltogether.
Also, try to stick to cabs from the same brand and series to make sure your amp's EQ can do its thing properly. Mixing high output cabs with low output ones will make things harder then they ought to be.

Trust me I have gone down that path but since I changed to the SWR 1x15 + 4x10 stack getting a good tone has been a breeze with any amp.
 
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