Speaker wattage vs amp wattage

[rutledj]

Two question really:

1.

Can someone comment on the relationship between matching a low wattage amp (I'm talking 5 watts) to a high wattage speaker (say 50-100w)?

I don't know of any 5 watt speakers but there are some 10w guitar speakers. Would there be a difference between the high and low wattage speakers on the same amp (assuming the same tonal characteristics)?

2.

I have built a Marshall Class 5 clone and put in a weber 10" alnico blue pup. What I notice is that the bass notes make the speaker sound like it is actually rattling. I even took the speaker out of the cabinet and listened to it and got the same noise.

Is this just normal for 10" speakers or could I have a defective speaker?

Thanks,
Rut

[teemuk]

Can someone comment on the relationship between matching a low wattage amp (I'm talking 5 watts) to a high wattage speaker (say 50-100w)?

Like the sensitivity or "SPL" rating states, the speaker produces x amount dB of sound pressure at 1W of power, measured one meter away from the speaker, on axis. If you want to get more specific about it, examine the speaker's frequency response that depicts the same information but throughout the entire bandwidth, not just as some nominal value.

Additional power will increase the outputted sound pressure in a logarithmic manner. The power rating tells how much power the speaker can safely handle.

I don't know of any 5 watt speakers but there are some 10w guitar speakers. Would there be a difference between the high and low wattage speakers on the same amp (assuming the same tonal characteristics)?

If everything else was indeed the same (which it hardly never is in real-life) the speaker with higher power rating would merely just withstand higher driving power without failing due to voice coil overheating or cone exceeding its excursion limits. Allowing this twofold increase in driving power would provide a 3dB higher sound pressure when things were pushed as hard as possible. For human ear and brain, that's only about 1.2x increase in perceived loudness.

If everything else was indeed the same that would be the only difference you'd hear. In practice you won't really hear any loudness differences due to different power ratings but differences between responses and excursion characteristcs of different speakers. And those can vary A LOT.

I have built a Marshall Class 5 clone and put in a weber 10" alnico blue pup. What I notice is that the bass notes make the speaker sound like it is actually rattling. I even took the speaker out of the cabinet and listened to it and got the same noise.

Is this just normal for 10" speakers or could I have a defective speaker?

Speakers of all size do sometimes rattle. Might be that you are hearing distortion, might be you're hearing the speaker hitting the resonant frequency, which sometimes rattles or "farts" things out, might be that the speaker is indeed defective. We can't really tell that from your description.

[pdf64]

Best to try the amp with a different speaker.
Even if it is the speaker, is it new? It may need time to break in.
Pete.