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#61 Mr. Foxen

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Posted 15 July 2009 - 11:56 AM

View PostRoob, on Jul 15 2009, 12:05 PM, said:

Hmm, interesting points, bit of a loss and a gain then.

In theory, it would be great to use the 4x10 speakers in the sessionette as it's own cab without the amp (assuming they will take the Mag 600), however i'm not sure how easy it would be to implement that.

Perhaps a cheap used Behringer BB115 to compliment the BB210 would work well?

Mr.Foxen - Could you describe a bit more what you mean by running the ashdown into the sessionette? Would running the ashdown head into the sessionette amp work? I.e. are you saying it just takes the signal and then lets the sessionette run as loud as i've set it, so it works independantly from the Behringer, which will be taking it's signal and power from the Ashdown?


Cheapest option is the best atm :)

Basically, you plug the Ashdown head into the behringer cab as one rig, then run a lead from the tuner out of the Ashdown (supposing is same as my ashdown) into the input of the Sessionette. Might need to eq fiddle. Score a big cheap 15 and run the ashdown into that with the treble right down, and turn the bass right down on the sessionette would be ideal way for this.

#62 Roob

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Posted 16 July 2009 - 11:20 AM

Ok, thanks for the advice guys, did some thinking and will probably start saving the pennys for a good 2x10 or 1x15 combo with plenty of watts to play with (to replace the Sessionette), so I can plug my Behringer cab in.

Superb thread, some good info here.

#63 WHUFC BASS

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Posted 16 July 2009 - 06:48 PM

Bottom line is - if you're worried about Ohms get a head that can handle 2 Ohms.
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Sorry but that is utter sh*te & an idiotic thing to write

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Posted 23 July 2009 - 09:19 PM

So wait- I have a head that is:
700W @ 2 ohms, 475W @ 4 ohms, or 275W @ 8 ohms

a 410 that is:
4 ohms. 350 Watts RMS continuous

and a 115 that is:
4 ohms. 400 Watts RMS continuous

is this good/bad? am i using this efficiently? when talking to my guitarist, should i say i have a "475W rig"?

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#65 stevie

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Posted 23 July 2009 - 09:29 PM

View PostM4L666, on Jul 23 2009, 10:19 PM, said:

is this good/bad? am i using this efficiently? when talking to my guitarist, should i say i have a "475W rig"?
No, you have a 700W rig.
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#66 pantherairsoft

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Posted 04 November 2009 - 10:44 AM

I have a question that I don't think has been covered!!!

I am running a MarkBass SA450, which runs 300W into 8OHMS and 500W into 4OHMS

Its well know that you want your speakers to be able handle more than your amp can give to allow a little headroom... but if you have two speakers.... do you add the Wattage together, or treat them as separate...

I want to use some portable cabs for on the go gigging.

I am planning on getting my hands on some MarkBass Traveler cabs in the near future two of these will run at 400W, 8OHMS each. Therefore my amp will be putting a 4 OHMS load into them (8ohm + 8ohm = 4ohm), meaning 500W...

So Am I likely to cause damage to the speakers, or is the combined wattage of 800W enough to take the 500W @ 4 ohm...

cheers

Edited by pantherairsoft, 04 November 2009 - 10:45 AM.

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#67 Musky

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Posted 04 November 2009 - 11:31 AM

Yeah, you add the power handling of each cab. The power from the amp will be split equally between the two (assuming both cabs have the same impedance, which they do), so each cab will be receiving 250w from your SA450.

It's worth bearing in mind that the 400w of the cabs refers to their thermal power rating, or how much power they can take electrically. How much they can handle mechanically can vary greatly depending on the speakers used. If you're feeding them with heavily compressed sounds and using a lot of bass boost they could run out of excursion even though they exceed the amp's rated power.

Just use your ears - if you hear them complaining turn the amp down or reduce the bass level.

#68 pantherairsoft

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Posted 04 November 2009 - 12:06 PM

Cheers bud... thats the answer I wanted to hear ;-)

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#69 umph

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Posted 04 November 2009 - 12:33 PM

View Poststevie, on Jul 23 2009, 09:29 PM, said:

No, you have a 700W rig.
don't say that it'll just encourage him to get a bigger rig!
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Posted 04 November 2009 - 01:20 PM

View PostMusky, on Nov 4 2009, 11:31 AM, said:

It's worth bearing in mind that the 400w of the cabs refers to their thermal power rating, or how much power they can take electrically. How much they can handle mechanically can vary greatly depending on the speakers used.

Exactly! See Finbar's dead Schroeder driver to for an example of mechanical failure.

View PostMusky, on Nov 4 2009, 11:31 AM, said:

If you're feeding them with heavily compressed sounds and using a lot of bass boost they could run out of excursion even though they exceed the amp's rated power.

Bass boost yes, compression no. The more compression the easier a time the speaker has mechanically (but the worse a time it has thermally).

View PostMusky, on Nov 4 2009, 11:31 AM, said:

Just use your ears - if you hear them complaining turn the amp down or reduce the bass level.

And that's all you need to know! (And if you're going for dirty sounds so you can't distinguish noises of complaint, then err on the side of caution by using more speakerage).

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#71 pantherairsoft

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Posted 04 November 2009 - 01:39 PM

Cheers for the words of advice. I do use lots of effects, but not too much overdrive and distortion... and I never 'push' my amp... As of yet I have never had my gain or volume past 50%. I like a nice clean, smooth tone.

Cheers again for the guidance!

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#72 hillbilly deluxe

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Posted 10 December 2009 - 12:07 PM

My Marshall DBS 200w has 2 speaker outputs on the back,i have a 2x10+1x15 @ 4 ohms cab,and a 1x15 @ 8 ohms cab.
Excuse my numptyness,but what affect will this have on the amps output ?
On the rear of the amp it states,minimum 4 ohms.

Edited by hillbilly deluxe, 10 December 2009 - 12:27 PM.

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#73 Bottle

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Posted 10 December 2009 - 12:28 PM

View Posthillbilly deluxe, on Dec 10 2009, 12:07 PM, said:

My Marshall DBS 200w has 2 speaker outputs on the back,i have a 2x10+1x15 @ 4 ohms cab,and a 1x15 @ 8 ohms cab.T
Excuse my numptyness,but what affect will this have on the amps output ?
On the rear of the amp it states,minimum 4 ohms.
Nothing good - the combined impedance of the 2x10/1x15 will be 2.6666 Ohms (which is less than the 4 Ohms minimum impedance your amp is capable of driving) so, DON'T DO IT!!! :)

Here's the science bit: Impedances in parallel are not simply additive, in fact the formula is 1/R1 + 1/R2 + ... 1/Rx = 1/Rt (being the total)

Therefore your set-up is 1/8 + 1/4 = 3/8, making your Rt 8/3, or 2.66666 Ohms

Hope this explains things.

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Posted 10 December 2009 - 12:37 PM

my power amp has the following specs.

Specifications
4Ω stereo: 2 x 300Wrms
8Ω stereo: 2 x 150Wrms
8Ω bridged: 1 x 400Wrms
Max power: 800Wmax @ 8Ω

I run it into 2 cabs rated 500 @ 8ohms, so i get 150 watts per cab meaning 300 watts? is this correct?

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Posted 10 December 2009 - 12:47 PM

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#76 Conan

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Posted 18 December 2009 - 03:09 PM

OK, I've read this thread through and there's loads ( :) ) of great advice - assuming I understand it all correctly! Ohm I God!!

One thing though, that I am not sure about, is the issue of series vs parallel wiring!

Within the cab itself, presumably the speakers can be wired up either in series or in parallel? If so, what are the relative benefits of each? And one assumes that the info plate on the back of the box will inform the user of how the speakers have been wired if this is important?

On the other hand, can cabs themselves be connected to the amp in either series or parallel? If the amp has 2 jack outputs then if you want to connect two cabs there are two ways this can be done

1. Take one lead out of the amp into the first cab and then connect the first cab to the second cab - so only one output socket from the amp is being used. I used to do this with my old Trace Elliot stack, but using XLR connectors rather than 1/4" jacks...

2. Run two leads out of the amp, one into each cab, so that the cabs are NOT connected to each other.

Does it make any difference? Is one series and the other parallel? Does any of this make sense?!? :wacko:

Edited by Conan, 18 December 2009 - 03:11 PM.

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#77 BOD2

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Posted 18 December 2009 - 03:36 PM

You don't need to worry about how the speakers are wired inside the cabinet and it won't tell you on the plate anyway.

What it does say on the plate is the total impedance of the cabinet and the power handling, which are the only details that matter to the user.

Inside, how the speakers are wired depends on how many there are and the impedance of each speaker.

Generally you cannot connect speaker cabs to an amp in series. With very few exceptions*, everything is geared towards parallel wiring. Unless stated otherwise, if there are two speaker outs on the amp then these will be wired in parallel.

If there are two speaker connections on a cab (to allow daisy-chaining) then these will be wired in parallel too.

So it makes no difference to use both speaker outs on the amp, or to daisy chain the cabs together - in almost every case* they will both be wired in parallel.

The only thing to note is that if you are daisy-chaining two cabs then ALL of the power for both cabs will go through the single cable connecting the amp to the first cab, so make sure this is a heavy duty speaker cable.

(*note - the reason I keep qualifying this is that there will be a serial wired amp or cab somewhere. I've never come across one but that's not to say there aren't some out there, which is why you should always read the manual or check what it says on the rear of the amp or jack plate).
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#78 Conan

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Posted 18 December 2009 - 03:51 PM

Cheers BOD2!

That's kinda what I thought but its nice to have it confirmed! Good advice about the cables BTW. I only found out recently that I had been using the wrong type of cables (i.e. instrument leads) to connect amps to cabs! Nobody tells you these things!! :wacko:
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#79 Al Heeley

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Posted 08 January 2010 - 12:46 PM

How are 4 x 10 cabs normally wired? (eg: 400W Hartke 410 cab)
Is it 4 x 8ohm speakers wired in S+P to give 8 Ohm total resistance?
Is it possible to rewire them to give a total 4 Ohm impedance thus get more power from the amp?
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Posted 08 January 2010 - 03:24 PM

View PostAl Heeley, on Jan 8 2010, 12:46 PM, said:

How are 4 x 10 cabs normally wired? (eg: 400W Hartke 410 cab)
Is it 4 x 8ohm speakers wired in S+P to give 8 Ohm total resistance?
Yep, if the total impedance is 8 Ohm, then that would be the most likely scenario (alternative is 4x 32 Ohm drivers all wired in parallel)

Quote

Is it possible to rewire them to give a total 4 Ohm impedance thus get more power from the amp?
No, not if you're running from a single amp output.

Of course, if you're running two power amps or a head with two separate power amp sections that can both drive into 4 Ohms then you can split the cab into two i.e two drivers (8 Ohms) wired in parallel will give you 4Ohms. Therefore the cab will go from a single input with 8 Ohm nominal impedance to 2x 4 Ohm.

Hope this makes sense?

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#81 tauzero

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Posted 02 March 2010 - 04:09 PM

View PostConan, on Dec 18 2009, 03:09 PM, said:

Within the cab itself, presumably the speakers can be wired up either in series or in parallel? If so, what are the relative benefits of each? And one assumes that the info plate on the back of the box will inform the user of how the speakers have been wired if this is important?

The benefits of parallel wiring:

If one of the driver goes open circuit for some reason, the other one will still work.

Um, that's about it.

There's probably cost benefits as well. 8 ohm drivers are the most common and therefore cheapest, 4 ohm and 16 ohm drivers are also available. This means it's easy to get a 4 ohm 2x10 or 2x12, or an 8 ohm 4x10 using the cheapest versions of the drivers.
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Posted 05 May 2010 - 07:22 PM

View PostJohnston, on May 4 2010, 09:16 PM, said:

I have a Fender M-80 combo with a 1x15". Going by the interwebs it is putting out 80watts through the 15" but if you plug in another cab you get the full 160w it advertises on the front.

On the back of the Head it has two outputs the 15" is in one and underneath it says 160w rms at 4ohms minimum.

Now I got given two 12" PA speakers I was thinking of building into a cab to try and help with the muddiness of the 15" . Both speakers are rated at 40w 4 ohms.

Can I wire these up run them with the 15" and not blow my amp??
Hmmm, not sure?

Sounds like the 15" in the combo is 8 Ohms, therefore putting another 8 Ohms in parallel will bring it down to the 4 Ohms required to get the full output power. To do this you'll need to wire the two additional speakers in series, then connect to the extension output on the combo.

HTH, Ian :)
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#83 algmusic

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Posted 28 July 2010 - 12:01 AM

ok last question. I have two a 2x10 600w@8ohm and a 1x15 400w@8ohm

The amp is switchable 500w @ 4 or 8ohms

When I'm using the 2x10. I should keep it at 8ohms. but when I using a both the amp should be at 4ohms.. right?
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#84 Mr. Foxen

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Posted 28 July 2010 - 12:20 AM

View Postalgmusic, on Jul 28 2010, 01:01 AM, said:

ok last question. I have two a 2x10 600w@8ohm and a 1x15 400w@8ohm

The amp is switchable 500w @ 4 or 8ohms

When I'm using the 2x10. I should keep it at 8ohms. but when I using a both the amp should be at 4ohms.. right?

Provided however you are connecting the pair is parallel (mnost are, but anything with two jacks should be marked how they relate). Usually two jacks on the back of amps say 'Outputs (parallel)' or somesuch.

#85 algmusic

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Posted 28 July 2010 - 07:44 PM

View PostMr. Foxen, on Jul 28 2010, 01:20 AM, said:

Provided however you are connecting the pair is parallel (mnost are, but anything with two jacks should be marked how they relate). Usually two jacks on the back of amps say 'Outputs (parallel)' or somesuch.

It actually doesn't say it's the terror bass. It must be parallel ?

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Posted 29 September 2010 - 10:15 AM

Just had a quick 'skim' through this thread, interesting.

Just a thought, if your using 2 cabs with one head, theres alwys the chance of a dodgy lead, so one cab not working, you wont neccesarily notice with a band playing at full tilt, all the power goint to the one that is working could result in knackered cab. Had it happen to me years ago. so its always worth Checking your leads by pulling em one at a time, and having a good tug at the connections while you listen for anything untoward.

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Posted 05 October 2010 - 06:28 AM

I apologise now if I am repeating something already covered, but as I can't find the answer I thought I would post my question anyway....

I understand the combination of ohm rating in different wiring combinations and the effect on the amps power output.
I also believe the more air you shift in total the 'louder' the rig (if power/ohm matched efficiently).
But does anyone know if a 400w 8ohm amp into 500w 8ohm 4x10 cab produces more or less db than a theoretically identical 4ohm rig; i.e. 400w 4ohm amp into 500w 4ohm 4x10 cab?


My grey matter can't decided the outcome :) ! - thanks for any comments.


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#88 xgsjx

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Posted 05 October 2010 - 06:54 AM

Good question, but one I don't believe could actually be answered. I know many manufacturers will make 4 & 8 ohm versions of cabs, but don't know of any that make 2 identical amps that run at the different loads to test your theory. The wattage of the cab doesn't really get taken into account, just as long as it can handle what it's being asked to draw.

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Posted 05 October 2010 - 07:48 AM

View Postjuice, on Oct 5 2010, 07:28 AM, said:

I apologise now if I am repeating something already covered, but as I can't find the answer I thought I would post my question anyway....

I understand the combination of ohm rating in different wiring combinations and the effect on the amps power output.
I also believe the more air you shift in total the 'louder' the rig (if power/ohm matched efficiently).
But does anyone know if a 400w 8ohm amp into 500w 8ohm 4x10 cab produces more or less db than a theoretically identical 4ohm rig; i.e. 400w 4ohm amp into 500w 4ohm 4x10 cab?


My grey matter can't decided the outcome :) ! - thanks for any comments.


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#90 alexclaber

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Posted 06 October 2010 - 02:47 PM

View Postjuice, on Oct 5 2010, 07:28 AM, said:

But does anyone know if a 400w 8ohm amp into 500w 8ohm 4x10 cab produces more or less db than a theoretically identical 4ohm rig; i.e. 400w 4ohm amp into 500w 4ohm 4x10 cab?

If the cabs are identical (bar the impedance) and the amps have identical frequency response, distortion and power output then the output will be identical. However I've yet to come across a loudspeaker where the 4 and 8 ohm versions have absolutely identical performance, let alone getting everything else to match!





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