Extension cab. More volume? Better spread? Stereo? - Jemsite
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post #1 of 8 (permalink) Old 10-19-2010, 04:53 AM Thread Starter
 
Join Date: Sep 2010
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Extension cab. More volume? Better spread? Stereo?

You guys look like you know what you're talking about it's all "greek" to me - ohms/series etc. I'm not looking for a technical explanation just what will it bring me?
I have a Marshall 5150,150W 2x12" combo
This combo was introduced in 1987 and was discontinued in 1991. It is a transistorised Split Channel combo.The rear panel of the amp has 2 speaker outs, one already going to the combo speakers of course. It states "minimum 4 ohms total load"
My mate wants to sell me a Marshall TSL212 extension cab 150 watt (2x75w speakers) Impedance: 16 Ohm
What I want to know is (in laymans terms) - what could this extension bring me? Volume? Better sound spread? Stereo?
I gig regularly with a Nottingham (UK) heavy metal band and use a Korg AX3000g for my sounds. I would appreciate your opinions….

Last edited by Marine Boy; 10-19-2010 at 04:57 AM. Reason: Font problems
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post #2 of 8 (permalink) Old 10-19-2010, 08:58 AM
 
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Re: Extension cab. More volume? Better spread? Stereo?

It won't necessarily make it louder...

If your amp is 150w, then it'll be 150W at 4 ohms (this only applies to solid states) generally. You need to know what impedance your speakers are in the combo to know what effect adding another speaker will have, but lets pretent the total impedance from your combo speakers is 16 ohms. Because 16 ohms is 4 times 4 ohms (the impedance at which the amp runs at 150w) you get roughly a quarter of the overall power (it normally works out a little more than this, but we'll keep it simple).

If you add another cab of 16 ohms in PARALLEL (which an ext speaker jack will be) this will HALVE the total impedance and DOUBLE the amount of power the amp is putting out.

You get double the power but across twice as many speakers so no one speaker is necessarily louder, there's just more of them. This tends to fill the sound out, and means you get the benefits of running a higher wattage e.g. more headroom (louder cleans before they get distorted) and tighter bass response.

Hope this helps, I've lost track a bit of what I'm saying that's 'too complicated', lol.
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post #3 of 8 (permalink) Old 10-19-2010, 03:09 PM Thread Starter
 
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Re: Extension cab. More volume? Better spread? Stereo?

Thanks Fun111. Everything is seeming a little clearer after your fine plain english explanation. So the power an amp puts out depends on the impedence of the speakers? Impede = "To retard or obstruct the progress of" means to restrict the output of the amp!
It's not extra volume I'm after (the combo is obscenely loud enough) so I should have more "headroom" for those cleaner tones at volume.
Is there any way I can run stereo effects with it if I put one each side of the stage?
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post #4 of 8 (permalink) Old 10-19-2010, 03:17 PM
 
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Re: Extension cab. More volume? Better spread? Stereo?

does this mean full stacks aren't that much louder than half stacks? not a smart alec, I just dont know anything about this lol
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post #5 of 8 (permalink) Old 10-19-2010, 03:46 PM
 
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Re: Extension cab. More volume? Better spread? Stereo?

One question at a time people! Lol.

Stereo: No, in order to achieve true stereo you have to have more than one poweramp driving more than one speaker set. It's the difference in signal (sometimes only very subtle) that gives something a true stereo effect. You can however simulate stereo by moving speakers around and using delay and reverb.

Impedance: yeah, your summary isn't exactly re technical explanation but it's near enough right. Reduce the impedance, you get more from the amp.

Headroom: yes.

Full stacks: this is slighty different. With solid state amps, the volume per speaker isn't louder necessarily, itdepends on what cabs you're ysig, you just get more sound.
Vale amps however put out the same amount of power regardless of how many speakers are connected. So take your dual rec, slap a couple of four twelves under it and valve amps put out I'm such a way that having two cabs chuck out the same kind of power that one would on it's own does make it seem quite significantly louder. The individual speakers arent louder, but justa ssinf one speaker to a valve amp makes the 'perceived intensity' notably higher (cabinetry assumed to be the same). It's to do with transient responses and spl which I'm not in the mood to attempt to explain in a way anyone can understand. I welcome somebody smarter than me to have a go lol.
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post #6 of 8 (permalink) Old 10-19-2010, 04:21 PM Thread Starter
 
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Re: Extension cab. More volume? Better spread? Stereo?

Excellent term "perceived intensity". So: more often than not - adding cabs when a perfectly good PA is being used (and backline) can be a hinderance to a sound engineer trying to create a balanced sound stage for a show. QED - More artistes than would openly admit may add a cab as they are in need of a boost in "perceived rockstarishness" rather than a boost in sound quantity or quality (transient responses notwithstanding). I'll get that cab!!!!!!!

Last edited by Marine Boy; 10-19-2010 at 04:29 PM.
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post #7 of 8 (permalink) Old 10-19-2010, 04:30 PM
 
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Re: Extension cab. More volume? Better spread? Stereo?

Very much so. Ideally, live, you want a 112 or somethin close miked and not too loud. Unfortunately, as with many aspects of 'rockstarishness' (to use your term), the bigger-is-better rule does apply. It's my honest opinion that big cabs and cranked valve amps sound best, my way of dealing with this is using Mesa cabs which are very directional, and having power switching options in my amp. It looks a bit imposing, but sounds fab and works well for the sound guy. :-)
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post #8 of 8 (permalink) Old 10-19-2010, 04:37 PM Thread Starter
 
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Re: Extension cab. More volume? Better spread? Stereo?

Valve overdrive (without speaker overdrive) + switchable power options on modern amps makes for the best of both worlds. In sound terms I have always thought there is a difference between a "loud" sound and a "big" sound. That extra cab certainly gives me big (and looks great too incidentally). Thanks for your advice Fun111.
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