Amp speaker

[surfdaddy65]

My question is this,

I have a Peavey pro 40 amp with a 40w speaker. I want to replace it, so do I have to find a 40w speaker or can I go a bit higher say 50w or 75w without damaging the amp or losing some sort of tone?

[armstrom]

Choosing a higher wattage speaker will not damage anything. You should probably use the same impedance as the stock speaker. As for the tone, that is where you will see the most difference. Each guitar speaker has its own unique character so changing to a different brand or model can affect your tone (for the better or worse). Another thing to look at is the efficiency of the speaker. If you buy a speaker with a lower efficiency rating than the stock speaker the amp will not seem as loud as it was before, if you get a higher efficiency rating then the amp will seem louder.

-Matt

[surfdaddy65]

Thank you Matt for the response. I am going to match impedance and go with a 50w since that is close to what the original speaker was. I will also use your advice and check the rating.

                                                     Thank you again,
                                                             Brett

[Enzo]

Are you sure the old speaker was only rated at 40 watts?  That would be most un-Peavey-like to mount a speaker barely rated for the amp.

[pete.a]

They well may have used a 60w or even higher rated speaker, depending on the voice coil . Your now entering into the "twilight zone" of tweeking mass produced electronic equipment...Make a successfull product, then cheapen the part's to gain profit..as production cost's rise. It happens all to often with most thing we buy an take for granted.
There's quite a few units to try out there , make sure you match the impeadence , and stick to your budget . They may well have used a driver that only cost peanuts to them , bulk purchasing has it's benefits . But you'll be amazed at the audiable difference a better driver..ooops speaker will do to an amp. It will then have your " signiture sound "
Try a hifi speaker very breifly and note the difference...

Hope this helps.

[slideman82]

I've read something and some experte made me a comment about it: when you push your powera mp very hard, till clipping section, probably the output will reach peaks of almost twice the total output of the amp. Abouyt efficiency, you'll have to look for 100dB/W/m or higher. For a veeeery reasonable price, I would buy a 75W Eminence speaker, the L1258 (cheapest) or maybe the other 75W, a bit better probabably (I think it was the Black Powder or something like that). They have 100dB of SPL!!!!! Thats a lot.
Peavey Classic series (30 and 50W tube amps) come with a 12" Blue Marvel speaker, made by Eminence, but they have only 96.5dB, not bad, but they also sound dark. New tube Fenders come with a golden label Eminence speaker, but it's nothing but the cheapest 12" guitar series speaker made by Eminence, the L1258. I've got one of those a friend gave me as a gift,  and sounds amazing!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Remember to match impedances, be sure your actual speaker is 8 ohms, so you can use some of the ones I mentioned.

[teemuk]

I've read something and some experte made me a comment about it: when you push your powera mp very hard, till clipping section, probably the output will reach peaks of almost twice the total output of the amp.

It's the issue about how they derive that rating. A power rating is typically the rating for average, continuous power produced by signals that have a form of a sine wave.

Now, you need to remember that the rating for amplifier's output power is quoted at some specific percentage of harmonic distortion. When the amp is overdriven and the distortion begins to increase pretty much anything can happen depending on the amp.

If it's your generic "soft clipping" amplifier, the distortion will increase gradually and the amplifier's peak output power may rise a lot before significant signs of clipping off the wave form's top begin to appear. The maximum output power limit is of course when the amplitude of input signal can no longer increase. But if the transition to this "total clipping" is slow, the peak power of a distorted signal – in reference to peak power of a clean signal - may double, triple, quadruple or about anything, depending how fast the amp transitions to greater amounts of distortion. In the attached image you can see this transition as "non-linear area", between full clipping and the "linear area", which ends when the distortion exceeds a certain % of THD.

A generic "hard clipping" amplifier will enter the state where output signal's amplitude no longer rises much faster. In the example image, the "non-linear area" of amplification is non-existent. Usually there's at least some in conventional amps, though. You can notice that in such amplifier the maximum power output does not differ a lot from the "clean" peak power output. Yet, an important point is that clipped signal is no longer a sine wave and the average power depends on the signal's waveform. It's much higher in case of, say, square waves, which at extremes are what distorted amplifiers output. You have the same issue with soft clipping amps, coupled to a fact that when they are overdriven to clipping where the waveform "flat tops" significantly also the peak power is typically a lot higher.

Estimating how much power an overdriven amplifier feeds to a speaker is pretty difficult and always a case-specific issue. If you have a scope you can derive it by calculating the waveform's area and using that information for approximately deriving how much average power such signal put out. It's difficult, though since you can't rely on handy equations that apply to nice geometric signal forms such as sines or squares. Without this kind of information... well, you're just risking it by relying on rules of thumbs that might not apply in your case.

[Jack1962]

Great info Teemuk, but if your amp is a peavey , and you are wanting to replace with a speaker that is not peavey , I recommend a 75 Watt. Peavey amps are rated at RMS(average output, a old standard) however , most new amps are rated at peak values(speakers as well)

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