Just wondering if anyone could help me out with a little problem, I will attempt to explain in the best way I can as I am in no way an expert in this field.
I am currently looking to buy a bass cab from a friend. It is an SWR Big Berther that comes loaded with a pair of Eminence long throw 15 inch speakers. The cab is rated at 4ohms but each speaker has a nominal impendence of 8ohms.
I have been told that the cab is rated at 4ohms because of the way the speakers are wired (I don't know if this is true) If this is correct my question is....could I rewire the speakers so that the cab runs at 8ohms so I can use it in conjunction with another 8ohms cab as my amp supports 16, 8 and 4 ohms total.
I read the manual that came with my amp and it says that if I use 2 speaker cabs they should both be rated at the same impedance and should not be any less then 8ohms each, as this would give a total of 4ohms.
Thanks guys. I hope this made sense :)
a cauliflower is just a cabbage with a college education
The speakers that you have are 2 8 Ohm speakers, connected in parallel - a wire goes from the power amp output to each speaker (+ to + and - to -).
If you were to connect them in series (wire from + of amp output to + of speaker A, - of speaker A to + of speaker B and - of speaker B to - of amp output) you would have a load of 16 Ohms.
To get 8 Ohms, you would need another cab with 4Ohm impedance and wire the cabs (NOT the speakers) in series.
I started with nothing - and I've still got most of it left.
Did you know that the word "gullible" is not in any dictionary?
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As each speaker inside the cab is 8 ohms, they can be wired in parallel for 4 ohms, or wired in series for 16 ohms. There is a possibility that the other cab might be able to be wired for 16 ohms, which together with the cab in question being rewired for 16 ohms, would give a total of 8 ohms to the amp.
That said, is your amp solid-state? If it is like many solid-state bass rigs I'm familiar with, the output is "transformerless", which effectively means that there are no specific 4-8-16 ohm taps of an output transformer to match against, only a minimum and maximum ohm value for which the amp is designed. In that case, whatever combination of cabs you plug into it will work, as long as the value of the cabs in parallel falls inside the minimum/maximum ohm rating for the amp, even for odd values other than 4/8/16.
Note that without more specific info about the amp in question this could be incorrect. One big clue that what I've suggested/assumed is correct/will work, is if the amp has no impedance switch, and the speaker jacks are marked something like "speakers 4 to 16 ohms" or "load 4 ohms minimum, 16 ohms max". If your amp has specifically-marked jacks for 4, 8, and 16 ohms, or if it has a speaker impedance switch, this may not apply and I would caution against using any combination of cabs that result in other than the marked values.
Cheers!
Strat
Thanks for the info so far guys.
Just thought I would give a bit more info about my set up. I will be using the cabs with a guitar amp...I know what you are gonna say "Why do you want a 2x15 cab and a 4x12 for a guitar?" :) I won't go in to that right now. The amp I will be using is an all tube Peavey Valveking and it has a switch on the back to select 4,8 or 16ohms. The speaker outs also have a label above them that says "4ohm minimum, speaker jacks paralelled" don't know if this makes a difference.
So do you think the best option would be to wire both cabinets so that they run at 16ohm?
If so, a few things. Does this make a difference in sound? Volume level? Or anything that would change what is coming out of the speakers? How does the impedance effect the signal?
Thank you again.
a cauliflower is just a cabbage with a college education
Well, in that case, you could wire both cabs for 16 ohms, plug them both into the amp, and set the switch for 8 ohms and be good to go. Same applies to wiring both cabs for 8 ohms each, and setting the switch to 4 ohms for other cabs and configurations.
As to impedance affecting the tone, a matched impedance is a matched impedance, tone will be affected only if there is an impedance mismatch. You *don't* want to mismatch the impedance, as this can cause serious damage both to the tubes and the amp, possibly destroying the output transformer and even possibly the power transformer.
Of course, with more speakers, you'll move more air, and therefore be louder. Impedance has no effect on loudness, as long as, like mentioned above, the impedances are matched. An impedance mismatch will only reduce the efficiency of the transfer of power between the power tubes and the speaker(s), and the lost power is dissipated in the power tubes and power transformer and power supply as excess heat and current.
And no, I'm not going to ask why you'd want to use 2-15's and a 4-12 for guitar. I actually like some 15's for guitar, depending on the style/tone I'm going for. I'm actually looking to pick up an alnico 15 or two down the road for use with my Stromberg-Carlson Signet 22 for certain blues tones.
Cheers!
Strat
Well, in that case, you could wire both cabs for 16 ohms,
But how's he gonna get the 8ohm 4x12 cab to 16ohms?
"Everybody got to elevate from the norm."
Well, in that case, you could wire both cabs for 16 ohms,
But how's he gonna get the 8ohm 4x12 cab to 16ohms?
Not a problem. Actually, reading back on his first post, the 4-12 cab is already at 8 ohms, so he could simply wire the 2-15 cab in series for 8 ohms, plug them both in to the parallel-connected speaker jacks on the amp, and set the impedance selector to 4 ohms. Bliss.
Cheers!
Strat
Not a problem. Actually, reading back on his first post, the 4-12 cab is already at 8 ohms, so he could simply wire the 2-15 cab in series for 8 ohms, plug them both in to the parallel-connected speaker jacks on the amp, and set the impedance selector to 4 ohms. Bliss.
Cheers!
Strat
The 4x12 is presumably at 8 Ohms, but the 2x15 is currently at 4 Ohms (with 2 8 Ohm speakers, they would have to be wired in parallel). There's no way he's going to get the 2x15 to 8 Ohms - changing to series would give him 16 Ohms.
I would guess that the 4x12 consists of 2 parallel-wired pairs of speakers, each wired in series. Each pair, wired in series, will give 16 Ohms. Wire the two pairs in parallel to give 8 Ohms.
I can't see a way to get them matched.
By rhe way, here's a good link http://www.teamrocs.com/technical/pages/connectingspeakers.htm
I started with nothing - and I've still got most of it left.
Did you know that the word "gullible" is not in any dictionary?
Greybeard's Pages
My Articles & Reviews on GN
I can't see a way to get them matched.
Neither can I.
"Everybody got to elevate from the norm."
D'OHH!!! Sorry!
That'll teach me to post a tech answer on no sleep! :oops:
Unless you change out the speakers in the 4-12 to 4-ohm speakers so that they can be wired such that the cab is 16 ohms, OR you change out the speakers in the 2-15 to 2 4-ohm speakers to achieve 8 ohms, slejhammer and greybeard are correct...no matching bliss.
Sorry again. I hadn't slept in like 36 hours...the furnace here had quit and I had to fix that, plus I got called to do an emergency re-install and configuration on a FreeBSD server (not mine), so I was pretty much toast. :lol:
Thanks slejhammer and greybeard for the wake-up call and correction! :)
Cheers!
Strat
LOL; no worries. I was actually hoping you'd have some creative solution, Stratman. ;) But, I guess we all agree these cabs shouldn't be mated unless the speakers are changed.
"Everybody got to elevate from the norm."
Oh well, it seems that a cheaper solution is not on the cards. I was looking forward to getting the soldering iron out and messing with some wires while saving a bit of cash. Oh well, its off to eBay I go!
Hey wait a minute. I have been looking for an excuse to swap out the speakers in my 4x12 for a while now. I have a set of Celestion Super 65's in there at the moment and they are ok I suppose. Any suggestions for some speakers that would match the impedance I need?
Thanks to all for answering my question so thoroughly.
a cauliflower is just a cabbage with a college education
Well, I'm not sure what to suggest, as I have no clue what kind of sound you're aiming for. Myself, I might load it up with some vintage style Webers say maybe some alnico 12A150S's since I love blues. They would be sweet coupled with a pair of alnico 15A125's, and driven with my old Stromberg-Carlson Signet 22!
Cheers!
Strat
I tend to go for a bass heavy ultra overdriven sound - I play in a lot of alternative metal styles, more of a Sludge sound. Its a little hard for me to explain but they would need to be able to handle a bit of a battering as well as holding out well under a lot of "Bass Stress" without sounding muddy. On the other hand I switch to a very full clean sound as well for the lighter and more prog moments. So it would have to be a pretty versatile speaker.
Don't know if any of that helps with suggestions as I know less about speakers then I do about quantum physics.
a cauliflower is just a cabbage with a college education
Interesting. From what you are trying to get tone-wise, the 15's you'd probably want would be something that has a fairly flat, smooth response and a tight bottom. I'd say you'd probably come pretty close with a Weber ceramic-magnet "Michigan 15". which look to me to be a bit JBL-like.
https://taweber.powweb.com/weber/michigan15f.htm
You'd probably want something a bit different in the 12's, since you'd have the 15's to push the bottom end...possibly a bit warmer than the 15's to give the overdriven sounds as well as the clean tones a bit warmer feel to compensate for the flatness of the 15's. I'd say maybe something along the lines of the Weber British Series ceramic "Silver Bells" in the 50 or 75 watt power rating. They should be warmer than the 15's for cleaner stuff, while still being able to do a great job with heavy crunch tones.
https://taweber.powweb.com/weber/silver12f.htm
Of course, like I said, it's all subjective. Tool around Webers' site and look for yourself, they have good descriptions of the various speakers and their sound/response.
Cheers!
Strat
