Question about ohms and watts of speakers.

[rcpmturbocho]

So I'm probably gonna buy the Ibanez TSA15h (Tubescreamer Head), and I want to make my own cabinet. I'm planning on buying Eminence speakers, so my question is, since the amp is 15 watts, can my speakers add up to, say 150 watts, or will there be too much headroom and not sound good? And does anybody have a good cabinet wiring website? Thanks much!

[cynical1]

Greetings and welcome to the Nutzhouse.

Rather then rehash everything all over again, let me direct you to lengthy discussion we've had previously regarding this subject at Topic: musicman speaker replacement

It offers several different views on the subject, but if it doesn't answer your question directly feel free to come back and ask.

Happy Trails

Cynical One

[rcpmturbocho]

Thanks! But the speaker in the cabinet that you can buy with is 80 Watts, so I just wouldn't want to exceed that wattage with two speakers?

[newey]

There's just so many variables that I don't think you can make a blanket statement that a higher-rated speaker will have "too much headroom".

[JohnH]

15W isnt a tiny amp, and there is plenty of evidence of peoples grinning faces when they plug their small but tasteful 5W, 2W or even 1/2W tube amps into 300W 4x12 cabs. So I would just pick your speakers according to overall tone.

[sumgai]

Akshully......

There is indeed good reason to be concerned about the output wattage of an amp versus the rated handling capability of a speaker.

But first....

---

turbo,

Hi, and to the NutzHouse!

---

OK, with the important part out of the way.....

Most players don't think about it, because we usually go for the big guns. Only in recent years have we become sensitive to the Charles Atlas muscle building strategm provided by behemoth amps and speakers. Most of us know that if you drive an amp too hard, it will clip (that is, it will distort very badly). But the audiophiles will tell you what we don't often hear as guitarists, and that is clipping a signal to a square wave is just about the most damaging thing you can do to a speaker.

Now it's true, what you've read on other websites and such, that this usually occurs at higher frequencies, but don't be fooled by that statement. While the clipping phenomenon may become visible earlier in the treble range, it's still present to some degree over the whole spectrum.

Long story short, the wise audist uses enough output power to keep from clipping the waveform at the desired volume levels. He/she then matches the speakers to handle that much power. (Some safety factor may be justified, such as 1.5x or 2x the power rating. However, there is a point where further investment is a waste of gilders.)

A word to the wise, and all that.

HTH




sumgai

[sydsbluesky]

I use a 65 watt speaker for my 5 watt tube head and a 320 watt 4x12 speaker cab for my 100 watt solid state head. I haven't had any trouble yet

[ashcatlt]

I'm pretty sure that we covered it in that other thread, but...

SG is correct that square waves are very bad things as far as speakers are concerned. It's important to note, though, that a tube driven power section is pretty much incapable of producing a true square wave. This is a good thing for us, since many of us specifically want to punish our output tubes in search of that magical tone thing you get from power amp distortion and/or power transformer saturation. In fact, that's one of the reasons so many people are switching to smaller amps. You can get that extra crunch without rattling the house apart. With a tube amp, you're more likely to burn up the amp itself than the speaker.

I'd venture to guess that most manufacturers of solid-state amps are aware that guitarists have a tendency to push their amps beyond the limits of sanity, and build some sort of speaker protection into their power amp sections.

Of course, for my part, I find it impossible to blow virtual speakers. In fact, I can match a 200W head with a 35W speaker without a thought. Don't change too many tubes either...

[sumgai]

ash,

Apr 19, 2010 11:49:50 GMT -5 ashcatlt said:

It's important to note, though, that a tube driven power section is pretty much incapable of producing a true square wave.

Absolutely false. All it takes is for the bias to go out of the linear range by about 15 to 20%, and the magic goes away. Sadly, this happens more often than we might think.

Worse, the damage is usually found in the upper frequencies because of harmonic interaction. This is where several lower harmonics are all at, or close to, the very nearly squared-off condition, but when they are forced to commingle, the resultant waveform is most definitely a square wave, albeit at some multiple of the original fundamental.

The unexpected ameliorating factor here is the output transformer itself. That worthy actually tends to be unable to follow a square wave accurately, at lower frequencies. But in the treble regions, it's not so good at rounding off the corners, so to speak. This one factor alone is why amps that handle the whole spectrum, pushing through speakers with or without crossovers, will tend to damage/burn out tweeters of any design, not just those with diaphrams. It speaks a lot to using a line-level crossover with two (or more) amps to break up the workload - it really does help reduce the risk of blown-speaker-itis.

HTH




sumgai

[spudler]

Would that same Idea apply to running a Peavey CS-800 power amp? I get 280 watts before the DDT enables at 8 ohm resistance so I don't have the clipping issue that will destroy the speaker but should I be looking for 100 watt 15" LF drivers or is this Idea only for guitar amp heads? I am looking to find 2 8 ohm drivers so I can get 4 and allow the amp to do 460 watts at DDT enable or find some 4 ohm drivers. I found this interesting along with the link as most of the Drivers I have found have been 400 watt and higher.

[sumgai]

spudler,

Is what idea only good for guitar heads?

If you're referring to the issue of overdriving an amp into clipping, and accidentally destroying a speaker because you couldn't hear the distortion (too high a frequency), then yes, the idea applies across the board to all audio-dom, not just guitar amps.

BTW, have you checked out the DDT circuit, or more accurately, have you googled for what others think about it? What I'm getting at is that DDT is Peavey's fancy name for a compressor, and nothing else. Yes, used correctly, it might help to save a speaker from being overdriven (emphasis on the might), but it's certainly not fool-proof..... one can indeed misuse it, and still blow up expensive stuff. The moral of what I'm saying here is, don't depend on it any more than you would your own innate common sense.

HTH



sumgai