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SumOne

Amp power for multiple cabinets

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Do I understanding correctly for this example:

  • 4x10 600W 8 Ohms + 1x15  400W 8 Ohms = Two 8 Ohm cabs wired in parallel have a total impedance of 4 Ohms.
  • Orange Terror Bass 500W  is 250 Watts into 8 Ohms or 500 Watts into an 4 Ohms (but that is split 250W per cab).
  • So that Amp only ever actually powers each cab up to 250W, meaning the 4x10 will only ever be powered to less than half of it's capacity and the 1x15 at less that two thirds. 

......so potentially something like the the Orange Terror Bass 1000 Watt version wouldn't be complete overkill (as long as not turning up beyond about 3/4) because it actually gives a maximum of 500W power to each 8 Ohm Cab? 

 

Edited by SumOne

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Yes that’s right, if plugging in two cabs each will get the same amount of power, however, in the case of a 1000 watt amp and a 410 & 115, each cab will get 500 watts but in the case of the 410 each speaker gets 125 watts whereas the 115 speaker gets all 500 (if running on full power of course). So it’s possible to overpower the 115, especially as in most cases that’s the cab on the floor whereas the 410 on top of it is more audible. 

Given how loud the Terrors are it’s unlikely you’d ever be anywhere near full power but it’s something to be mindful of. The theory is two of the same cab works the best rather than mixing speaker sizes.

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25 minutes ago, Lozz196 said:

Yes that’s right, if plugging in two cabs each will get the same amount of power, however, in the case of a 1000 watt amp and a 410 & 115, each cab will get 500 watts but in the case of the 410 each speaker gets 125 watts whereas the 115 speaker gets all 500 (if running on full power of course). So it’s possible to overpower the 115, especially as in most cases that’s the cab on the floor whereas the 410 on top of it is more audible. 

Given how loud the Terrors are it’s unlikely you’d ever be anywhere near full power but it’s something to be mindful of. The theory is two of the same cab works the best rather than mixing speaker sizes.

Nice one, cheers. Yeah I wasn't considering the Watts per speaker rather than per cab but that makes sense.

There's a 1000 Watt Terror for sale at what seems an alright price (£400) which I'm considering as long as it's not overkill that's going to blow any speakers I get in future.

Edited by SumOne

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1 hour ago, SumOne said:

 that Amp only ever actually powers each cab up to 250W, meaning the 4x10 will only ever be powered to less than half of it's capacity and the 1x15 at less that two thirds.

That capacity is thermal, not mechanical. The average cab has a mechanical capacity no more than half the thermal capacity.

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All amps come with a built in feature to stop you blowing speakers... it's called a 'volume' control.  

Be aware that amp and cab ratings aren't an absolute science and it is difficult to accurately compare 2 manufacturers.  

Finally the difference between 500 and 1000w is not double; 1000 is not twice as loud as 500w.  If you want double the output power you need TEN times as many watts (like for like amp).

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I just got this from an audio blog:

"Many sound engineers will say that “underpowering”, or using amplifiers that are too small for the speakers, is worse than “overpowering” them. Although they have good reasons to say such a thing and in practice speakers do tend to break mostly when the amp is being driven beyond its operating range, the truth is a bit less straightforward than that; basically, overdriving a small amp can actually release as much power to the speaker as a big amp, and it isn’t the distortion per se that breaks the speakers but rather the increased power of the signal at different frequencies............It’s usually a good call to err on the side of caution by choosing a bigger amplifier than strictly required; it will happily output the correct power cleanly, and if it eventually runs loud enough to break the speaker, that’s a good sign that the speaker needs to be replaced with something bigger. A smaller amp would have been clipping at that point, and most likely would have eventually broken the speaker anyway.https://proaudioblog.co.uk/power-ratings-2-why-speakers-break/

So I guess although something less powerful than 1000W would be probably plenty, it's not necessarily a bad thing to get the 1000W and  just keep it turned low. (this one I've got my eye on is a fair bit cheaper 2nd hand than the 500W brand new).

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3 minutes ago, SumOne said:

So I guess although something less powerful than 1000W would be probably plenty, it's not necessarily a bad thing to get the 1000W and  just keep it turned low. (this one I've got my eye on is a fair bit cheaper 2nd hand than the 500W brand new).

I personally have no problem with that view (I've driven 200w cabs with amps that 'could' deliver 1000 - 1600w BUT I wasn't using the full potential) but you must listen to your gear and adjust volume (and frequency boost/cut) accordingly.  Amplifier watts have never been cheaper (or misquoted) so why wouldn't you future proof your purchase and have spare headroom.  

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Probably not helpful during a lockdown, but the numbers are really no substitute for actually hearing the thing in action.

I've owned 2000W power amps that left me thoroughly underwhelmed, and 200W heads that are just ridiculously loud. And I'm only talking about solid state amplification.

Move to valve amps and you have to start all over. This last two days, I've been playing through my old WEM Dominator open-backed combo (built 1971). Way too loud in the studio to crank even to the halfway point, and that's rated at 15W. Which is rubbish because everyone knows they actually put out 17W.

With modern amplification it is highly unlikely that you will manage to blow anything up, and extremely likely that (in real world gigging volume terms) you will have more headroom than St. Paul's Cathedral.

 

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34 minutes ago, Happy Jack said:

This last two days, I've been playing through my old WEM Dominator open-backed combo (built 1971). Way too loud in the studio to crank even to the halfway point, and that's rated at 15W. Which is rubbish because everyone knows they actually put out 17W.

Funny how we all go on about Mesa, Ampeg, and even Marshall, as well as so many others, yet WEM rarely get a mention on this forum, despite the tone being lovely and as you say Jack, their tube amps being rather good at being heard despite their conservative power ratings

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1000w amp will have no trouble blowing up the 15'' cab if you let it. Even easier to do with the 410 on top drowning out the sounds of the 15 dying.

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2 hours ago, SumOne said:

I just got this from an audio blog:

"Many sound engineers will say that “underpowering”, or using amplifiers that are too small for the speakers, is worse than “overpowering” them. Although they have good reasons to say such a thing and in practice speakers do tend to break mostly when the amp is being driven beyond its operating range, the truth is a bit less straightforward than that; basically, overdriving a small amp can actually release as much power to the speaker as a big amp, and it isn’t the distortion per se that breaks the speakers but rather the increased power of the signal at different frequencies............It’s usually a good call to err on the side of caution by choosing a bigger amplifier than strictly required; it will happily output the correct power cleanly, and if it eventually runs loud enough to break the speaker, that’s a good sign that the speaker needs to be replaced with something bigger. A smaller amp would have been clipping at that point, and most likely would have eventually broken the speaker anyway.https://proaudioblog.co.uk/power-ratings-2-why-speakers-break/

So I guess although something less powerful than 1000W would be probably plenty, it's not necessarily a bad thing to get the 1000W and  just keep it turned low. (this one I've got my eye on is a fair bit cheaper 2nd hand than the 500W brand new).

The critical information being left out of the statement above is that "underpowering" is not what causes the damage, but the clipping which causes damage primarily to the high frequency drivers. Otherwise, how would all of the overdriven tones work... they are various forms of clipping. This information is from a pro audio perspective, one that generally avoids high level clipping, and also generally has better (more effective) processing to prevent mechanical damage form too much power.

Speakers have both thermal and mechanical failure modes. Clipping is generally a thermal failure mode in the high frequency driver, which is why players who use overdriven and distorted tones generally play cabinets without tweeters also. Not only do tweeters disproportionally reproduce the harmonics generated by clipping, but they don't last long doing so at higher power levels. In bass guitar, the most common form of speaker damage is mechanical, and this always occurs from too much power. This is either from an amp that is too large for the speakers, or a misunderstanding of how the amp and the speaker are rated (ie. RMS, program and peak descriptors). When a speaker is rated at say 1000 watts, without any descriptor, the FIRST question to ask is HOW that rating is made. 

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Just as an aside, the pairing of a 1x15 and a 4X10 is horrible. The 1x15 has no chance of keeping up with a 4x10. If you're thinking that the 1x15 will add lows you couldn't be more wrong as the typical 4x10 will put out more! 

Edited by BassmanPaul
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36 minutes ago, BassmanPaul said:

Just as an aside, the pairing of a 1x15 and a 4X10 is horrible. The 1x15 has no chance of keeping up with a 4x10. If you're thinking that the 1x15 will add lows you couldn't be more wrong as the typical 4x10 will put out more! 

Cheers, that was my long term plan so am considering a bit of future proofing for the amp to handle it - my understanding was that they would combine okay but it looks like I'll have to give this more thought. (GAK's upselling pitch for the  Orange 115 is "Combine with one of the AD200B heads and a OBC410 cab and you'll have a completely Orange, 100% floor-punishing bass rig!") 

.....I might not go for Orange at all though. I mostly play reggae/dub so eventually want to build up to something that can push out a lot of sub and rattle chests and assumed 15" were best for that. 

Edited by SumOne

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Have you considered a separate preamp and a class D power Amp as an option as that would give you more options with different cabs. I play reggae too and I use one with my barefaced cabs and having a Dubster II (18"sub), on one side of the power amp and a BBII 12" + tweeter on the other gives a heck of a lot of chest rattling bass and I can control what I deliver to each cab. 

 

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6 hours ago, jazzyvee said:

Have you considered a separate preamp and a class D power Amp as an option as that would give you more options with different cabs. I play reggae too and I use one with my barefaced cabs and having a Dubster II (18"sub), on one side of the power amp and a BBII 12" + tweeter on the other gives a heck of a lot of chest rattling bass and I can control what I deliver to each cab. 

 

Nice one, I've got my eye out for a Dubster 2, they seem pretty rare though.

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55 minutes ago, SumOne said:

Nice one, I've got my eye out for a Dubster 2, they seem pretty rare though.

Wasn’t there one in the classifieds awhile ago? Might not have sold. A Super Twin would work well. They are sensitive cabs so your watts sound louder. A500 watt amp would probably be ok.

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21 minutes ago, chris_b said:

Wasn’t there one in the classifieds awhile ago? Might not have sold. A Super Twin would work well. They are sensitive cabs so your watts sound louder. A500 watt amp would probably be ok.

No sign of a Dubster 2, but there is a Barefaced Big One which I've just enquired about - looks good.

Almost anything would be an improvement on my current setup of PA Poweramp and speakers (saved slightly as it's fed via tube DI and a Cab sim pedals).

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Much good advice above. A 15 won't necessarily produce more lows than multiple smaller drivers. Chris B raises the important point of efficiency/sensitivity - how much acoustic output you get for a given input power. That is down to cab design, as well as driver type/size. Simply adding a large single driver cab won't necessarily give you more of what you want, especially if it produces a lot of subsonic or infra bass, which can cause issues with the PA via low frequencies travelling through the stage floor, up mic stands and into mics. It can also muddy the sound in the room.

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To confuse things ideally I would like to be able to use the Amp and Cabs not just to play Reggae via the Bass, but to also use with my Decks and DJ mixer (and perhaps combined with my current PA Poweramp and speakers) when I DJ Reggae. The DJ mixer has separate main output and monitor outputs so could possibly run the PA Poweramp and speakers via one output and the Bass Amp and Cabs via the other. Or possibly something like the Barefaced Big Baby covers the whole spectrum better and it could replace the PA gear, but them I assume a Bass specific Amp isn't going to be ideal for that.

 

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As it happens 2yrs ago i did a gig with my band at a big garden party used my BTII for my bass and Dubster added to the keyboard players small pa for the rest of the band and sounded great. Afterwards my mate who is a reggae DJ was doing his thing with his cabs inside and outside the house, so i suggested using my cabs instead so we had the BTII outside and dubster inside and it sounded incredible, full, clean with lots of bottom end. i think two BTII's and a dubster would be a fantastic quality lightweight pa, Not that you'd really  need a dubster with two BTII's but can' hurt.

 

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1 hour ago, jazzyvee said:

As it happens 2yrs ago i did a gig with my band at a big garden party used my BTII for my bass and Dubster added to the keyboard players small pa for the rest of the band and sounded great. Afterwards my mate who is a reggae DJ was doing his thing with his cabs inside and outside the house, so i suggested using my cabs instead so we had the BTII outside and dubster inside and it sounded incredible, full, clean with lots of bottom end. i think two BTII's and a dubster would be a fantastic quality lightweight pa, Not that you'd really  need a dubster with two BTII's but can' hurt.

 

Nice one, so you reckon the BT2 has enough mids and highs to be a decent PA? that's good to know....there's a BT2 for sale on here for £600 and I guess it should have at least a 600W amp  (2nd hand for about £400) so I could have a decent Bass rig for about £1k that could also double up as a Reggae DJ rig (perhaps combining with my current PA amp and speakers for the DJ stuff, but ideally it could replace them to partly fund it....and as I think my wife might kill me if I fill the house with many more speakers!). 

Edited by SumOne

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