OT: speaker wattage vs. amp wattage...

[marrstians]

if you have two speakers in a 100watt combo do the speakers wattage have to match each other? would a 60watt and a 30watt give you 90watt speaker handling? what's the dangers of the speakers wattage being lower than the amps output?

[brett]

Hi.  I'm no expert, but here's what I know...

if you have two speakers in a 100watt combo do the speakers wattage have to match each other?

No they don't.  Especially if their frequency-handling characteristics are different.

would a 60watt and a 30watt give you 90watt speaker handling?

Usually, yes.

what's the dangers of the speakers wattage being lower than the amps output?

You can overheat the speaker coils (very nasty) and cause other physical and electrical damage to the speaker.

It is worth noting that speaker ratings are "nominal" and really only apply to sparticular signals under particular conditions.  For example, heavily clipped signals tend to cause more heating per unit of volume than sine waves.  I'd also suspect that speakers are more prone to overheating inside in Florida than outside in Alaska.  

Some speakers have two ratings - continuous power and peak power. The continuous figure (usually about 1/2 of the peak figure) is more likely to be a good match for amp output.  

Maybe it's just bad luck (or maybe that 200W amp) but I've blown a few speakers that I feel should have handled what I was feeding them.  (eg. 2x100W Eminance speakers didn't last 2 minutes, but my 250W Daichi can take everything I throw at it and not even get warm).

cheers

[smoguzbenjamin]

a 60 and 30W speaker together will give you 90W in series, not sure about parallel. But if you've a 100W amp you're still feeding the speakers too much. Don't count on them surviving in there. Get a speaker that has a nominal rating above what you're going to do to i, ie get 150W speakers for your 100W amp just to be safe.

[Paul Marossy]

From what I understand, using a 30 watt and 60 watt speaker together in series or parallel will give you a nominal rating of 90 watts. But like it was said earlier, it depends on how those speakers are rated. If it's 30 watt continuous and 60 watts continuous, then you should be OK. But if those are peak power ratings, then you run the risk of frying your speakers.

[petemoore]

the speaker will only "handle' 30w if it's 15w...
 no that's not it [actually it is but] wattage is like a funny thing to me.
 Ppl think a 100w speaker will sound louder than a 25w ... which is 'sorta' true in a way, I call it a misnomer.
 a spk 'rated' at 100w will tend to absorb more inergy without failing than a 25w would...I have 25w speakers that get very very loud...that's not what determines loudness per AMP's watt.
 Ohmage is what determines how much, and more importantly the proportion that two speakers wired in series or parallel draw.
 If you're running two 8 ohm speakers hard, they both are sounding' about equal volume...one is a 2w speaker, one is a 10w...which one is going to blow first? 'probably the 2w.
 Basically I disregard wattage as long as the cone doesn't 'cannon' out of the socket, and they don't reach untouchable temperature real quick...
 What I do instead is listen.
 Listen intently to what a speaker does under *WCS [*worst case scenario], is probably the best method of choosing speaker applicability for me these days.
 Personally I like my guitar speakers on the 'lo-watt side...Jensen, Celestion 'types' so many brands I just go by type evermore...low wattage/high quality construction.
 I like the idea of getting a garbage speaker and slowly [as you can] torturing it to death ... sort of like a 'Medschool' experiment...take notes on how hot it felt to touch, what types of 'odd' noises came out of it...'usually' speakers will warn you about overload conditions before failing outright....the slow overheat being the one that's hard to listen for...basically the speakers probably gonna hafta sound half like sh__ for a time to get it into overload mode...no reason for it really...every speaker I've ever tried didn't sound as good as at 'normal' levels when pushed past it's optimal operating levels...
 Basically you're volume control on the amp like turns 'mushy' as does the sound, having little effect on amplitude increases, mainly the sound becomes more muddy past a speakers opt. op. point...by not ever running your $ speaker that hard you can exponentially increase it's 'durability'...you can put a 'hidden' weak spot in a speaker...and not even be able to detect it...well till it rears it's ugly head...
 There's plenty of reasons to develop skills that allow you to never overload speakers...the only reason 'to do it is the haunting 'death cry' that they may make before sounding like total garbage or failing altogether....kind of a pricey way to get a few seconds of mayhem...well when JIMI did it for the first time it was cool...evermore I'm not all impressed with blowing stuff up for the sake of blowing stuff up.

[Aharon]

Make sure the impedances are the same.There's a danger (i'm not sure) that one speaker will get a bigger share of the power coming from the amp.
I would not feed 90W to the pair ,not even close.
I would keep it at a max of 45W.In any case you still gt the benefits of having two speakers instead of one.
I'm not saying I;m 100% right here,just look into it further.
Aharon

[smoguzbenjamin]

Loudness just depends on how much air you can move. An 8ohm 12" speaker will move more air than an 8ohm 6.5" speaker at the same wattage. But if you have a 50W amp, it might be usefull to have a speaker that can handle those 50W and a bit more.

And if one speaker is 4ohms and the other is 8, the 4ohm speaker is going to get 2/3 of the load because of its lower impedance.

[Boofhead]

When driven from the same amplifier the overall power *rating* is not the sum of the two when using drivers with different powers.  The power *to* each speaker adds and the amplifier will be outputting this amount of power... but.... the problem with the rating is the lower rated speaker will hit it's limit before the higher rated speaker so the overall rating will be double the rating of the lower speaker - this assumes the speakers are of the same impedance.  So in your case the overall rating will be 2x30W = 60W. At the rating point your amplifier will be producing 60W but it has the potential, for example if you overdrive your power amp, to produce 50W+ into both speakers thus stressing out the 30W driver.

The overall loudness depends on sensitivity of each driver - it's quite possible to get more output from a high sensitivity 30W driver driven by 30W than a low sensitivity driver driven with 60W.  Regardless of drive level the higher sensitivity driver will always sound the louder of the pair.

[petemoore]

Whatever speakers you have, they divide the load of the amp, if you can get accurate enough ohmage readings [even two 'matched' speakers will have and will likely develop more ohmage differences as time and current goes by and through them].
 a 4ohm sp and an 8 ohm sp wired to the same amp...yes the 4ohm will draw the LIONS share [might as well disconnect one of the two at this point] of the load, as well putout the lions share of the loudness produced and percieved...you'll have to stick your ear IN the 8 ohm to even tell if it's 'on' at all.
 So naturally I would put my money on a 60w speaker if I had to choose between a which of the two [a 60w and a 30w] *like ohmage [*within say 5% of being the same ohmage] speakers would give out first when pushed...
  another way...watts rating has little to do with how much power a speaker draws. Ohmage is what determines how much load the speaker sees...[especially useful to know when two speakers are running off of the same amp].
 If you disconnect your cabinets speakers for some reason, take an ohms reading on your coils...you might be surprized at the differences in coils resistance in one 4x12 cabinets coils.
 I had 30 yr? old VOX Bulldogs in VOX 4x12'' cab. One of the four Bulldogs read 6.2 ohms and another read 7.4 ... do the %age math ... Definitely a noticable difference in output/draw from even 8 feet away from the cabinet [if I moved around the front] speaker to speaker...I would want the 'weaker' higher ohm ones on the bottom of the cab.
 Hopefully this will prompt some other readings, as I say these speakers came from a 60's VOX, and were used for very high amplitude Bass for years..coil damage was suspect, the Speakers sold and [feedback from new owner] tales of 1 failure as they were used in a combo amp  for a short time.

[Boofhead]

You shouldn't read too much into DC resistances.  The *impedance* of a speaker varies substantially with frequency and small differences in DC resistance can be swamped by the AC impedance effects.  Check out for example,

http://www.aikenamps.com/spkrload.html

Output differences are due to speaker sensitivity, this is determined by efficiency of the speaker magnet system and the mass of the cone and the area of the cone.  Light cones with stong magnets are usually more efficient.  Larger cones allow a better transfer of electrical energy to acoustic energy - think of how much air disturbance you can do with your hand compared to that of a large hand fan.  The differences can be enormous, in the order of 10dB across all guitar speakers, which equates to one speaker requiring 10 times the power to give the same output as another.    Many home stereo systems using small 5" speakers have heaps of power but don't produce much volume.