One 4ohm cab or two 8ohm cabs?

[stingraysvt]

Oops, yes, you are no doubt correct about that amp. I guess my starting point in a rig is an amp that can handle 2, 4, and 8 ohms. Needless to say, I don't use an SVT 7 pro.

I was very happy with an SWR 350 silver face, a Crest CA6 power amp, and now I really dig my Mesa Boogie carbine M9. They seem to have no problems with 2 ohm loads.

So maybe the SVT 7 pro is part of the "problem," LOL?

I had to check for myself as well, you would think an amp like that would do 2 ohms... :/

 

[Grant_MM]

If you have a 410 the only thing other than another identical cab I would try might be an evenly power matched 212. 115 and a 210 might work together as well. MIGHT. It might also cause phase issues in the audience.

The 212 sounds interesting. I will have to do some research!

 

[Jim Carr]

I think I would be tempted to find the best possible 4 ohm 410 I could afford (used of course!). There are some great sounding very loud cabs out there.

Then (when the recession ends and the $un comes out), I would get a new head and another cab, either an 8 ohm 210 or another 4 ohm 410, depending on how many hair cells my audience needs permanently flattened.

 

[JHAz]

Technically there's not enough information in the question to answer it. All things being equal, a 4 ohm cab will draw twice the power of the 8 ohm cab, and doubling power givesa3 dB increase. BUT that assumes both cabs have the same sensitivity. Diffferent cabs will have different loudnesses at one watt )and the difference continues as you add power, at least until the speakers start to compress). If the 8 ohm cab is more sensitive by 3 dB, the power advantage of the 4 ohm cab disappears.

As I understand the OP, the question is what happens when you get to the speakers' limit, assuming your amp can push either to the limit. It's often suggested on these boards that the typical speaker will start distorting around one half of its rated power, so if you want to be clean, that's a reasonable ballpark expectation. More imiportantly, perhaps. AFAIK, all merely mortal speakers will start to experience power compression before they start distorting.

That means that at some point, when you double power (say from 100 to 200 watts, instead of 3 dB increase you get 1 or 2 dB increase . . . and at some point more power yields no further volume because the speaker can't move any farther.

Bottom line is you can't really tell from specs, especially if you are comparing ratings between different manufacturers because they may use different methods to define sensitivity and power handling, and nobody publishes compression data . . .

 

[BlackRussian]

... I'm going back to read the AMPs FAQ.

 

[JTE]

Hi, just wondering if a single 4ohm 4x10 cab would sound better/louder than an 8ohm 4x10 cab if they're both being pushed to the limit.

Assuming identical cabinets... Won't sound better, nor worse. And might be slightly louder, but it's not really going to be noticeable.

I currently run two 8ohm 4x10 cabs together during larger gigs, but I'd like to only bring one to small venues. Is it worth dropping the cash for another cab, or am I better off just running both of my cabs together to make the 4ohm load?
Thanks

The difference between the 1000 WRMS @ 4Ω and the 850 @ 8Ω is going to be negligible and trivial. IMO it's not worth buying another cabinet just to get a four ohm load on the amp for smaller gigs. And as already pointed out, you already have two cabinets for bigger gigs, and more speakers will always trump more power.

John

 

[Bass_Pounder]

But if you had an 8ohm 210 and an 8ohm 410 wouldn't the 210 be then overpowered because the watts would be shared evenly?

It just loads the amp to 4 ohms, there wouldn't be a power struggle so to speak

Yes there would...............

The speakers in the 2X10 would be getting twice the power of the speakers in the 4X10 and would hit their mechanical limits long before the 4X10 starts breaking a sweat.

The proper way to run a 4X10 with a 2X10 is to have the 4X10 be a 4 ohm cab, and the 2X10 an 8 ohm cab. That will ensure even power distribution between the 6 speakers.

 

[billfitzmaurice]

What the OP is basically asking and it's a question I'm interested in too, is a 410 thats rated at 4ohms any louder than a 410 rated at 8ohms if they are both pushed the same at the same watts.

No. And every reply in this thread that deals only with watts and/or cone area is incorrect, because neither watts nor cone area determine maximum output. That's the product of frequency response, sensitivity and total driver excursion capability. So to answer the OP:

Hi, just wondering if a single 4ohm 4x10 cab would sound better/louder than an 8ohm 4x10 cab if they're both being pushed to the limit.

No. If the only difference in the cabs is the impedance, leaving frequency response, sensitivity and excursion the same, then when both are driven to their limit, which is determined not by watts but by excursion, they will sound the same. The only difference between them is the voltage swing required to push them to full excursion.

 

[Jim Carr]

Yes there would...............

The speakers in the 2X10 would be getting twice the power of the speakers in the 4X10 and would hit their mechanical limits long before the 4X10 starts breaking a sweat.

The proper way to run a 4X10 with a 2X10 is to have the 4X10 be a 4 ohm cab, and the 2X10 an 8 ohm cab. That will ensure even power distribution between the 6 speakers.

+1

Yes, as noted above. Just to (LOL) belabor it, the amp FAQ says:

"a 4 ohm cabinet and an 8 ohm cabinet run in parallel the formula is 1/(¼+1/8). You can’t add ¼ to 1/8 without having the same denominator (I told you this was gonna sound like school), so you have to reduce ¼ to 2/8 so they match. Then adding 2/8 to 1/8 gives you 3/8, dividing 8 by 3 gives you 2.67. So, hooking up an 8 ohm cabinet and a 4 ohm cabinet in parallel to your amp gives the amp a load of 2.67 ohms to power. "

So the OP's SVT 7 Pro, which is apparently not 2 ohm capable, rules out the 2.67 ohm (210 8 ohm + 410 4 ohm) option.

 

[JTE]

I would think the formula for parallel impedance is much more clearly expressed as:

RT​=(R1​*R2​)/(R1​+R2​).

So for a matched pair of 8Ω loads it's (8*8)/(8+8) = 64/16 = 4.

Same for a mis-matched combination of 8Ω and 4Ω, that's (8*4)/(8+4) = 32/12 = 2.67. No need for converting denominators, just add, multiply, and divide.

John

 

[Jim Carr]

I would think the formula for parallel impedance is much more clearly expressed as:

RT​=(R1​*R2​)/(R1​+R2​).

So for a matched pair of 8Ω loads it's (8*8)/(8+8) = 64/16 = 4.

Same for a mis-matched combination of 8Ω and 4Ω, that's (8*4)/(8+4) = 32/12 = 2.67. No need for converting denominators, just add, multiply, and divide.

John

What he say!

I was quoting the venerable stickie, which clearly needs improvement.

 

[Bjess002]

Are there any risks of running a 4 ohm 410 with a 8 ohm 115?

 

[billfitzmaurice]

Are there any risks of running a 4 ohm 410 with a 8 ohm 115?

No, and as a 115 typically will fart out long before a 410 you're better off with the 115 being 8 ohm, so that most of the power goes to the 410. Of course if maximum output is what you want don't mate a 115 and 410, use two identical 410s.

 

[Bass_Pounder]

Are there any risks of running a 4 ohm 410 with a 8 ohm 115?

As long as your head can handle a 2 ohm load, technically no problem.

However, in your case - what would be gained by running them together ?

A 1X15 is a poor match with a 4X10 as it is because speakers make sound by moving air (displacement). The average 1X15 only has the displacement to keep up with a 2X10, so against a 4X10, it is already outgunned.

Now, add to that the fact that you want to mix a 4 ohm 4X10 with an 8 ohm 1X15. This means that the 4X10 will get 2/3 the power, and the 1x15 will only get 1/3.

While you may not be in danger of blowing up the 1X15, I don't think your really going to get alot of sound out of it.

 

[Bjess002]

Right now I'm running a 410 and 115, 8 ohms each. Problem is I think my amp (GK 1001RBii) is overpowering the 410. It struggles at high volume and I have just blown my second speaker. So I want to get a 4 ohm 410 to increase the wattage push from the amp as well as up the cab wattage to about 100-300 over the amp. Don't want to rid of the 115, though.

 

[David Jayne]

Right now I'm running a 410 and 115, 8 ohms each. Problem is I think my amp (GK 1001RBii) is overpowering the 410. It struggles at high volume and I have just blown my second speaker. So I want to get a 4 ohm 410 to increase the wattage push from the amp as well as up the cab wattage to about 100-300 over the amp. Don't want to rid of the 115, though.

You are far, far better off replacing the 1x15 with another 8 Ohm 4x10. This will present a 4 Ohm load, maximizing amp power, with the speakers to handle it.

 

[Blah114]

just asking.. when you use two cabs.. are you going two connections from the SVT7, one into each cabinet? or are you presenting both cabs connected to one another as 1 overall 4 ohms connection? are you using both outputs from the SVT or just one?

 

[Bjess002]

What if I replaced the 15 with a 212, 8 ohm, to add to the low-end a bit?

 

[Bjess002]

just asking.. when you use two cabs.. are you going two connections from the SVT7, one into each cabinet? or are you presenting both cabs connected to one another as 1 overall 4 ohms connection? are you using both outputs from the SVT or just one?

I'm running from GK 1001RB-II, not SVT7. And I run two connections, on into each cab. the 410 and 115 are GK BLX-II, one 1/4" input in each, can't connect them.

 

[CL400Peavey]

What if I replaced the 15 with a 212, 8 ohm, to add to the low-end a bit?

Speaker size doesn't correlate to low end presence by itself. I have an 810 cab, and it has more low end that any other cab I have played through, regardless of cone size be it 15's or 12's. What is really important is the specs on the speakers themselves, and the cabinet they are put into.