Speaker Wattage

What wattage speakers would you need to run a 100 watt tube head into a 4x12 if the speakers are 8 ohms?

Also, concerning a different setup, if I stick a 90 watt speaker in my 15 watt tube Blues Junior would it have any downside?

First of all, if you use a standard wiring scheme, the impedance of the speakers doesn't matter. You add the wattage for each speaker. Theoretically, four 25W speakers is fine. But it really depends on the head. Some 100W heads can put out more than
100W with distortion. Some 25W speakers can handle more than 25W, some cannot.

I might prefer a low wattage speaker, even an AlNiCo, but there is no problem with using a higher rated speaker, other than you won't get speaker distortion.

One thing that you may or may not know: One of the biggest factors (other than tonal characteristics) is the sensitivity of the speaker. A common misconception is that a 90W speaker is "louder" than a 15W speaker. This is NOT necessarily true, you need to look at the SPL rating. The higher the rating, the louder the speaker.

Louder speakers are not always better. I use an old Hiwatt 4x12 Fanes with my 2204 Marshall because they are less efficient speakers. This means an earlier "sweet spot" for the distortion, where a more efficient cabinet would be even LOUDER (it's really to loud as it is).

I "love" the sound of old Celestion 25 watt speakers in my `74 Super Lead half stack. Speaker breakup and the tone is just about perfect for me - nice and woody.

I agree with Steve on the suggestion for your smaller amp. If you have this speaker of yours laying around, and it's the correct ohms for the amp - sure, you can try it out. But a lower wattage speaker may "sound" better to your ear.

A Kendrick Black/Gold 35 watt combo that I sold to the other guitar player has a 12" speaker, and both Rex and I have tried a bunch of different speakers in that amp. The best of the lot was the old Celestion Lead 80.
It didn't exhibit the "cone cry" that I've experienced with Vintage 30's, and sounds really good in that amp.
www.celestion.com has lots of info for speakers. A guitar student of mine e-mailed Dr. Decibel with questions about speakers, and about a week later a packet arrived from England, with two CD's of sound samples, brochures and decals, etc. Excellent customer relations and service in my opinion.
www.webervst.com is an American company making very good speakers; again lots of info there. In a 2 x 12 cab, I have both a Vintage 30 and a Weber ceramic Blue Dog, and while the V30 has a better top end and slightly better mid range, the Blue Dog is far superior for low end. A good match of speakers in this particular cab.

Good luck on your tone hunt; all the best!
Walk in Beauty, Peace. Scott

It won't hurt anything. Some people believe speakers sound better when they're being run closer to their max wattage ratings.

Steve mentioned speaker breakup. I'm not an expert but I'm not sure that breakup *necessarily* correlates with being closer to the max rating, since I see Weber speakers that are rated the same, but some supposedly offer earlier breakup than others.

I agree. However, there is more to it than wattage. You need to make sure that the speakers are wired in such a way that the effective impedance of the speaker setup matches the output impedance of your amp.

Using 8-ohm speakers, two speakers in series would be 16 ohms. Two speakers in parallel would be 4 ohms. If you take two pairs of speakers wired in series (16 ohms) and parallel the pairs, you are back to 8 ohms. This is a pretty common wiring setup in 4x12's.

Are you just replacing speakers, or building from scratch?