help me understand how speaker wattage capacity and amp wattage interact

[tsp17]

i’ve always heard that amp wattage and speaker wattage capacity “shouldn’t” be too far apart.  For a rough example and rule of thumb (subject to what you like to hear)  a 35 watt tube amp would call for a speaker capable of 50-75 watts.  just my non-tech understanding of the prevailing view. 

I have multiple amps mated to speakers  (either in combo or cabinet) that will take up to 250 watts.  I have a 2x12 cabinet with a pair of 250 watt 8 ohm speakers that sounds amazing with a 50 watt amp.  

So what am i not understanding here?  

I just put the same 250 watt rated  speaker in a 35 watt combo amp (3rd Power Wooly Coats Extra Spanky).  Sounds pretty good so far (needs to break in).  Very touch sensitive, but really good first five or so hours on it.   Thinking about experimenting with something lower wattage.    I’m a big believer in Duke Ellington’s saying that “if it sounds good, it is good”, but curious about what difference it might make to more closely match the amp wattage to speaker capacity, e.g., try a 60-70 watt similar speaker. 

thanks, 

Tad

[kbp810]

Eh, lots of variables and generalizations in play... but in a nutshell; if the amp wattage is higher than what the power/watt handling of a speaker is, it's going to lead to 1 of 2 likely outcomes - 1) the speaker will easily distort... which in some scenarios could be a desirable effect and compliment the amp distortion (especially when paired with another higher power/sensitivity speaker); in other scenarios, it could just sound muddy, "farty", or bad. 2) The speaker could just fail...blow the cone out or toast the voice coil. 

In the reverse role; if the speaker watt/power handling is way higher than the amp output... usually this will make very little difference. It depends more on the design and sensitivity of the speaker at this point. For example, I love to pair the 300 watt EVM-12L with all sorts of amps, including little 5 watters; fairly transparent speaker pairing that let's more of the amps own voicing be heard (minimal speaker distortion/coloration). 

Usually the only negative scenario is where it's a speaker with a very heavy cone and low sensitivity; that could be a speaker that needs a whole lot of power to make it move in order to sound good. There's not many guitar oriented speakers out there that fall into this grouping though. It's more in the extreme cork sniffers high end of car or home audio (or cheap garbage speakers from temu or something).  

TLDR - Low power amp with high power speaker; okay. High power amp with low power speaker; may cause death of speaker, or could get you that cinnamon girl sound you've been searching for all your life (if one was to ever search for such a sound). 

[TalismanRich]

The wattage on a speaker is an indication of how much power you can put through the voice coil without it heating up to the point that burns out.   The suspension, cone material, available voice coil travel will determine if it breaks up,  and sensitivity will tell you how loud the speaker will be at a reasonable power level.   The speaker will distort if you exceed the rating, especially if you try to exceed the cone travel. 

If you  play highly distorted,  then you should have a higher power speaker capacity since those distorted squared off waves are actually higher in power than a sine wave of equivalent amplitude.

Something like the Celestion Peacekeeper handles 50W but only puts out 86dB for 1 watt of power.   A Vintage 30 will handle 60W and puts out 100dB for that same single watt.

Also, it depends on where you set the amp.   A Twin can put out a lot of power, but if you only turn up to 2, you might only be putting out 3 or 5 watts.

 

[tsp17]

thanks guys.  I knew i was asking the right crew.  much appreciated.

[bolero]

yep summed up pretty good above

There is a dynamic between particular speakers & particular amps. Always good to play around with combinations but use caution. Unless you can afford recones or don't have any rare vintage speakers.

I have an old ~15w tube amp I put an ancient Bell & Howell alnico film speaker in it, very light resonant cone. That thing RAWKS when it's cranked up. I bet it's just on the verge of the speaker's power handling

[bolero]

man, I was just thinking about this thread again. I wish I still had my celestion alnico blues & alnico gold 12" speakers. They were really good.

I sold them when I unloaded my Vox & Matchless amps

[tsp17]

16 hours ago, bolero said:

man, I was just thinking about this thread again. I wish I still had my celestion alnico blues & alnico gold 12" speakers. They were really good.

I sold them when I unloaded my Vox & Matchless amps

with you there my friend.  my list of things that I wish I'd kept, or should have snagged, lives in my head rent free. very happy with what I have now, but there a few items that in hindsight ....

[bolero]

haha, very true, that!

[rockabilly69]

My favorite speaker is the Weber 12A125A. It's a low wattage speaker that I use in three amps currently

Mesa DC-2 (25 watts)

Clark Beaufort Supreme (20 watts)

TopHat Club Deluxe (20 watts)

The speaker is rated at 30 watts, but sometimes I throw a lot of outboard gain pedals into these amps (Origin Effects Revival Drive and M/EQ driver, Analogman Sunface BC108 fuzz, Durham Sex Drive) so I try to listen carefully to see if I'm at that edge. Because as Rich says above, square waves (particularly fuzzes), can destroy speakers if pushed close to their ratings!

That said, I WANT the speaker to distort as I think that is part of the rock and roll sound.

[tbonesullivan]

4 hours ago, rockabilly69 said:

That said, I WANT the speaker to distort as I think that is part of the rock and roll sound.

Guitar speakers are definitely designed to have a "non-linear" response zone, and they do break up when pushed. How much they do has to do with the design, and also how much "dope" has been put on the cone.

[bolero]

8 hours ago, rockabilly69 said:

My favorite speaker is the Weber 12A125A. It's a low wattage speaker that I use in three amps currently

 

I have one of those with a destroyed cone I keep forgetting about. I should get it reconed!

[rockabilly69]

6 hours ago, tbonesullivan said:

Guitar speakers are definitely designed to have a "non-linear" response zone, and they do break up when pushed. How much they do has to do with the design, and also how much "dope" has been put on the cone.

Mine are lightly doped and they break up gloriously. 

3 hours ago, bolero said:

I have one of those with a destroyed cone I keep forgetting about. I should get it reconed!

yes you should!

[tbonesullivan]

13 hours ago, bolero said:

I have one of those with a destroyed cone I keep forgetting about. I should get it reconed!

oh boy, is there a good story to go along with that? I've only once had to deal with a bad speaker, which came in a Rivera Pubster 25. The horrible wiring job should have been a clue, but man the frame was even bent. No idea how the person who sold it to me could have not been aware of that.

[bolero]

shipping damage, unfortunately. I never even got to hear it!

[zguitar71]

A speaker that is rated at twice the amp power rating has long been the safe standard, or the combination of multiple speakers equaling twice the rated power. I personally don’t think that is really necessary though. I have now built 3 6g3 amps and paired them with 65 watt Scumback M75 Speakers. I would use lower wattage but there isn’t one until you get down to 25 watts. The amps have varied in output based on the power transformer used and plate voltage supplied. The lowest wattage of the three was 12.9 clean and 17.4 cranked all the way up with 355 volts on the plates. That would be fine for a 25 watt speaker. The first one I built I used a vintage spec PT and had 440 volts in the plates which gave almost 30 watts when fully turned up, that would not be good for a 25 watt speaker. So from a manufacturing standpoint, a company would spec a speaker that can cover variations like that. Smaller builders may have much less variation or can even spec the speaker based on a single build. I’m comfortable with a speaker that is around 10 watts more than the amp is rated for something lower wattage like a 17 watt amp. I built a JTM 45 that maxes out at 42.78 watts (JTM 42.78?) and I’m comfortable using the same 65 watt M75 in that amp but I probably wouldn’t go lower than that. The last gig I used that amp on I had a 200 watt Eminence Em12n speaker and it sounded great, especially clean. There is zero speaker breakup but the dirty sound is just a little sterile compared to the M75 that gets a little breakup and adds some warmth to the sound. Some may prefer the 200 watt speaker though, to each their own. The amp has a master volume and I turned it down to the level the sound guy wanted, then when I got home I measure the output. I played the gig at 14.5 watts dirty and about 8 watts clean with a 200 watt speaker. 8 watts with an efficient speaker is louder than most people realize and with todays stage management makes amps like the JTM 45 obsolete without a master volume or attenuation. I have a 20 speaker that is going into yet another 6g3 variant I’m building only this is a single channel and uses 6k6GT power tubes and should max out at 10-12 watts and be perfect for most places I play. 

Edited 18 hours ago by zguitar71