Ohms FAQ

[A9ismine]

thanks guys.so you think it will be o.k im dreading doing it and getting my facts wrong

[B-string]

Originally Posted by A9ismine

thanks guys.so you think it will be o.k im dreading doing it and getting my facts wrong

You should be fine as long as you don't crank the GenzBenz up real high or use to much low end boost at moderate levels!

[IvanMike]

Do they teach Mathematics any more?!?!?!?!?

[TJBass]

Originally Posted by IvanMike

actually i'm kinda against that. Most of the time you end up with an 8 ohm cabinet someone mods into a 2 ohm cab (and even if it is marked well that causes the risk of someone using it with an amp that can't deliver into a 2 ohm load and frying their amp), or a 4 ohm cabinet modified into a 16 ohm cab (which is just freakin quiet).

Not sure if someone asked this or not, but what would be the advantage to wiring an 8 ohm cab to 2 ohms, even if you had a head that would safely go down to 2 ohms?

Sorry, I'm at work and the search didn't produce the answer and I have run out of time trying to find it in all the posts here.

[IvanMike]

Originally Posted by TJBass

Not sure if someone asked this or not, but what would be the advantage to wiring an 8 ohm cab to 2 ohms, even if you had a head that would safely go down to 2 ohms?

Sorry, I'm at work and the search didn't produce the answer and I have run out of time trying to find it in all the posts here.

the advantage is you use more watts and can get a bit louder. so if you have an 8 ohm 4x10 that handles 600 watts and is 8 ohms, but your amp puts out 200 into 8, 350 into 4 or 550 into 2 then by re-wiring the cab to 2 ohms you'll use 550 watts rather than 200, and get about a 4dB increase in volume, which isn't a hell of a lot. Better off getting another cab if you have volume issues.

[TJBass]

Originally Posted by IvanMike

the advantage is you use more watts and can get a bit louder. so if you have an 8 ohm 4x10 that handles 600 watts and is 8 ohms, but your amp puts out 200 into 8, 350 into 4 or 550 into 2 then by re-wiring the cab to 2 ohms you'll use 550 watts rather than 200, and get about a 4dB increase in volume, which isn't a hell of a lot. Better off getting another cab if you have volume issues.

Not knowing exactly what 4db sounds like, I'll just stick with what I gots!

[IvanMike]

Originally Posted by TJBass

Not knowing exactly what 4db sounds like, I'll just stick with what I gots!

3 dB is generally considered the minimum increase most people can hear. 4 dB isnt much different. some folks can hear a 1 dB increase, but it's tiny.

[Gimme5]

I've read through everything in this excellent thread, but still found a way to ask a few questions specific to my situation.

At long last, I'm considering updating my rig and need advice. I currently have an SWR SM-400, an SWR Triad I, and an ancient Eden David D-210T. I generally run the SM-400 in stereo, with one channel to the Triad and one to the Eden, or I run the SM-400 bridged to the Eden. The Eden is conveniently labeled for 250 W/4 Ohm, which I've been ignoring, since the SWR delivers 400 W to 4 Ohm in bridge mode. I haven't managed to kill my little Eden yet, as I'm pretty careful.

So now I have a couple of questions. First, I'm thinking of going to a Genz-Benz ShuttleMAX 1200, which basically has two 600 W channels @ 4 Ohm. First question: can I continue to use my 250W/4 Ohm Eden with one 600 W channel of the GB, or will I kill the poor thing? Second question: the current Eden 210XST is rated at 500W/4 or 8 Ohm. Anybody know what's different about the new cab that doubles it's power handling capacity? Third question: with the G-B at 600W/4 Ohm per side, would I be better off with the 4 or 8 Ohm Eden, that is if, say, I had no alternative but to go with the new cab?

The thing is, I love my little Eden, plus I would prefer not to have to move into the garage, which might be necessary if I spring for a nice new little Eden. Hep me!

[Thornton Davis]

Originally Posted by Gimme5

I've read through everything in this excellent thread, but still found a way to ask a few questions specific to my situation.

At long last, I'm considering updating my rig and need advice. I currently have an SWR SM-400, an SWR Triad I, and an ancient Eden David D-210T. I generally run the SM-400 in stereo, with one channel to the Triad and one to the Eden, or I run the SM-400 bridged to the Eden. The Eden is conveniently labeled for 250 W/4 Ohm, which I've been ignoring, since the SWR delivers 400 W to 4 Ohm in bridge mode. I haven't managed to kill my little Eden yet, as I'm pretty careful.

So now I have a couple of questions. First, I'm thinking of going to a Genz-Benz ShuttleMAX 1200, which basically has two 600 W channels @ 4 Ohm. First question: can I continue to use my 250W/4 Ohm Eden with one 600 W channel of the GB, or will I kill the poor thing? Second question: the current Eden 210XST is rated at 500W/4 or 8 Ohm. Anybody know what's different about the new cab that doubles it's power handling capacity? Third question: with the G-B at 600W/4 Ohm per side, would I be better off with the 4 or 8 Ohm Eden, that is if, say, I had no alternative but to go with the new cab?

The thing is, I love my little Eden, plus I would prefer not to have to move into the garage, which might be necessary if I spring for a nice new little Eden. Hep me!

Not to nit pic but I believe you mean you're considering a ShuttleMAX 12 which has 2 x 600 watt power amps in it (along with two preamp channels). Each power amp outputs 600 watts at 4 ohms as you've noted above. Be aware that with an 8 ohm cabinet, each power module output drops to 375 watts. The nice thing with the SM12 is that you can run multiple combinations of ohm's to each separate power module in the amp. For example, 1x8 = 375 watts, 1x4 = 600 watts, 8+8 = 750 watts, 4+8 = 975 watts, or 4+4 = 1200 watts.

If I was going to have a ShuttleMax 12 driving a 410 cabinet, i'd want that cabinet to be rated at 4 ohms, to maximize the output power of one of the SM12's power modules.

Personally, I do own a ShuttleMAX 12 and I use it to drive my two (4 ohm each) 410 cabinets. This way both power amps in the SM12 are outputting their maximum capacity 600 watts each x 2.

I'm sure someone will come along and answer your other questions. If not, contact Jeff Genzler at GB through their website and ask him. He'll respond back very quickly.

Good luck.

TD

[lowfreqfreak]

I would first off just like to thank IvanMike for all of his info on this. I am building a bi-amp system and would appreciate it if someone could help me tie up the loose ends.. (specific questions at the end of my post).

I landed here because I use a 5 string bass and have been running it through an Eden Navigator and a QSC Plx 1602 (bridged to yield 1100w @ 8ohms) through an SWR 6x10 Goliath Sr. (1200w RMS @ 8ohms - from SWR website) for a couple years. Well, the low end (B string) is kinda distorted, not really clean, low thumping bass... "not really kicking ass" in my book. I learned in another thread thanks to Greenboy that my cab simply is not made for faithful reproduction of the low B and when I looked up my cab's specs, sure enough the low frequency range is about 25hz above what I'm looking for.

So I've come to the conclusion that I want to build a bi-amp system with a sub that is rated for 30hz and below. The cabs I'm interested in are the SWR Goliath 4x10 (800w - not sure if I should get 4ohm or 8ohm if they are both rated for 800w), and the SWR Big Ben 1x18 (400w 8ohm).

Ok finally, my questions!
1.) In short, I think I'm gonna need a more powerful power amp! I used to run a Hartke3500 350w head through my 6x10 cab and was experiencing horrible clipping when I hit low notes.. I was told because I was not pushing enough power through my cab, which led me to pick up my QSC plx1602... On QSC's site, the plx1602 can provide "Continuos average power per channel" of 300w @ 8ohms, and 500w at 4oms. Following the logic of what made me get the plx1602 in the first place, I assume I want MORE than enough power per channel to provide headroom for each cab. Right? Specifically, I'd need at least 800w for the 4x10 and at least 400w for the 18"?

2.) What are the disadvantages or advantages to choosing a 4ohm 4x10 Goliath cab over the 8ohm in a bi-amping scenario? Since my future 4x10 and 1x18 will be getting independant power, I should not need to worry about either of the cabs getting too much or too little as long as I have a power amp with enough headroom. Correct?

I do not get to a computer that often and I'm usually reading this site on mobile, but I am bookmarking this on my iphone right now so and will be checking back frequently. Eager to hear what you all have to say!

Thank you in advance!

[Gubna]

Originally Posted by IvanMike

Do they teach Mathematics any more?!?!?!?!?

check my math:

I can't use two 4 ohm cabinets powered by a GK Backline 600 because that would make them, combined, have 2ohms, and you can't put 4 ohms output into 2 ohms.

correct?

But I could use two 8 ohm cabinets, because that would make, combined, 4 ohms.

I think this is correct, but writing it out helps.

[IvanMike]

Originally Posted by Gubna

check my math:

I can't use two 4 ohm cabinets powered by a GK Backline 600 because that would make them, combined, have 2ohms, and you can't put 4 ohms output into 2 ohms.

correct?

But I could use two 8 ohm cabinets, because that would make, combined, 4 ohms.

I think this is correct, but writing it out helps.

yes this is correct.

[RickenBoogie]

Originally Posted by lowfreqfreak

I would first off just like to thank IvanMike for all of his info on this. I am building a bi-amp system and would appreciate it if someone could help me tie up the loose ends.. (specific questions at the end of my post).

I landed here because I use a 5 string bass and have been running it through an Eden Navigator and a QSC Plx 1602 (bridged to yield 1100w @ 8ohms) through an SWR 6x10 Goliath Sr. (1200w RMS @ 8ohms - from SWR website) for a couple years. Well, the low end (B string) is kinda distorted, not really clean, low thumping bass... "not really kicking ass" in my book. I learned in another thread thanks to Greenboy that my cab simply is not made for faithful reproduction of the low B and when I looked up my cab's specs, sure enough the low frequency range is about 25hz above what I'm looking for.

So I've come to the conclusion that I want to build a bi-amp system with a sub that is rated for 30hz and below. The cabs I'm interested in are the SWR Goliath 4x10 (800w - not sure if I should get 4ohm or 8ohm if they are both rated for 800w), and the SWR Big Ben 1x18 (400w 8ohm).

Ok finally, my questions!
1.) In short, I think I'm gonna need a more powerful power amp! I used to run a Hartke3500 350w head through my 6x10 cab and was experiencing horrible clipping when I hit low notes.. I was told because I was not pushing enough power through my cab, which led me to pick up my QSC plx1602... On QSC's site, the plx1602 can provide "Continuos average power per channel" of 300w @ 8ohms, and 500w at 4oms. Following the logic of what made me get the plx1602 in the first place, I assume I want MORE than enough power per channel to provide headroom for each cab. Right? Specifically, I'd need at least 800w for the 4x10 and at least 400w for the 18"?

2.) What are the disadvantages or advantages to choosing a 4ohm 4x10 Goliath cab over the 8ohm in a bi-amping scenario? Since my future 4x10 and 1x18 will be getting independant power, I should not need to worry about either of the cabs getting too much or too little as long as I have a power amp with enough headroom. Correct?

I do not get to a computer that often and I'm usually reading this site on mobile, but I am bookmarking this on my iphone right now so and will be checking back frequently. Eager to hear what you all have to say!

Thank you in advance!

I think you may want to do further research into bi-amping. Essentially, the 2 cabs you're considering are both "full range" cabs, and hence, not suited for a true biamp set up. What you'll want, is one, very large sub woofer, which will require massive amounts of power, coupled with a crossover, and then a small midrange/tweeter box, maybe a 1x10 or even a 1x8 with tweet, that will require substantially less power. Running 2 full range cabs in a biamp set up is useless. There is lots of info on this site, and google is your freind too. good luck.

[ElectraPhoenix]

add me to the list of people whom this thread prevented from posting a question on the forum.... it should be a club!
seriously, though, great thread. it all makes sense to me now.

[Scotte_4U]

Hi Mike I read your post and I thank you for the information. It makes for good reference because I am easly confused LOL but I did print it out to go into my folder with my amp.

[A Strohman]

I just want to thank everyone who has contributed to this thread. I spent a lot of time carefully reading the various discussions (even the heated arguments) and for the first time I feel like I've got an understanding of the basic concepts which will allow me not only to make good purchasing decisions but also will keep me from destroying equipment. Up until this point I can only attribute the fact that I *haven't* blown up an amp to pure luck.

In my playing career I've had several lightbulb moments where all of a sudden something just locks in and makes sense. Most of those moments have centered around my technical playing ability. But I now have had a lightbulb moment when it comes to the electronics behind my sound and that can do nothing but help me. So thank you.

[rickkilcher]

i read all through here and some other sites.

I have a 575+575W head, so i wanted to be able to use the max of the power given, so i would work with 2 8ohms cabs.

But, can i, for exemplo, plug both head´s outpup in one 8ohm cab?
and get the same as 2 in paralel

[slyjoe]

Originally Posted by rickkilcher

i read all through here and some other sites.

I have a 575+575W head, so i wanted to be able to use the max of the power given, so i would work with 2 8ohms cabs.

But, can i, for exemplo, plug both head´s outpup in one 8ohm cab?
and get the same as 2 in paralel

Absolutely NOT. Never plug two amp outputs into the same cabinet. You'll fry one or both of the power amps.

[youngnicholas]

this may or may not be the right thread for this question, but i'm running a musicman hd-150 (150w hybrid head) into an old ampeg svt 8x10 (one input jack, no parallel outputs)and i'm looking to add some more bottom end. basically, i wanna know if i can also run my head through a 1x15 without my head exploding. is that even possible??

thanks guys,
- nick

[RickenBoogie]

Originally Posted by youngnicholas

this may or may not be the right thread for this question, but i'm running a musicman hd-150 (150w hybrid head) into an old ampeg svt 8x10 (one input jack, no parallel outputs)and i'm looking to add some more bottom end. basically, i wanna know if i can also run my head through a 1x15 without my head exploding. is that even possible??

thanks guys,
- nick

Not if the MusicMan head is 4 ohms minimum, which I assume it is. Besides, it's a fallacy that a larger speaker will produce more low end.