Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: joecool85 on December 22, 2010, 08:56:56 AM

Title: Watts vs Volume (db)
Post by: joecool85 on December 22, 2010, 08:56:56 AM
Everyone seems to think that they need more watts to get more volume.  While it is true that more watts will be louder than less given the same speaker, it is also true that the speaker is more important than the watts in most cases.

For every 10db gain (double perceived volume) you need a 10x multiplication of wattage.  So a 100watt amp is only twice as loud as a 10watt amp.  The reason this doesn't normally seem so is that 10watt amps normally have poor spl rated speakers, making the 100watt amp sound more than double the volume.  Playing through a better speaker will help increase your db rating, and hence your overall volume.

I've attached a chart to give you an idea of how an efficient speaker is louder than more watts on a less efficient speaker.

With this chart you can see that a 90db speaker on 100watts is less volume than a 102db speaker cab with only 10watts.  Most inexpensive amps come with speakers of about 90-93db.

To keep up with an average drummer you will want about 110db.  To reach this level you could use a 100watt amp with a single 90db speaker or you could run a small 10watt amplifier through a cab with rated 100db or better.

The calculation for total db is this:
{log (watts of amplifier) x 10} + speaker spl rating in db at 1w = total db output

Or if you want to figure out what db speaker (or cab) you need to hook into to get a certain desired db output:
Desired db output - {log (watts of amplifier) x 10} = Necessary speaker/cab db rating at 1w

Here is an excellent calculator for adding up speaker db and finding what the total output is: http://www.sengpielaudio.com/calculator-spl.htm

And thanks to Roly, another good table:

Speaker sens. (1dB/W@1m) Required power (watts)
104db1
101db2
98db3
95db6
92db12
89db24
86db48
83db96
80db191
77db382
Listener range 8 feet, desired listener SPL 80dB, amp headroom 15dB
Title: Re: Watts vs Volume (db)
Post by: trialabc on December 24, 2010, 02:03:37 AM
But for what I have seen, most likely, there will not be db marked on the speaker. Usually I see Ohm and Watts.
What can I do if I can just see the two information marked? Perhaps the size can help?
Title: Re: Watts vs Volume (db)
Post by: J M Fahey on December 24, 2010, 08:25:43 AM
The datasheet sure helps.  ;)
If the speaker was a "house brand" one pulled from a guitar amp, as a "Jaguar" from a Randall, a "Fender special design" or an unnamed one from a Crate or Peavey, etc., they are almost always an OEM Eminence; most probably available to the general public as one of the "Legends".
Generic "Celestion inside" boxes most often have "Rocket 50" , sometimes V60 or at best "Seventy 80", being the least expensive ones.
Beware, they all sound good, it's just that they were not "used by Hendrix"
Title: Re: Watts vs Volume (db)
Post by: rowdy_riemer on December 24, 2010, 12:32:02 PM
You could possibly rig something up to do the measurements yourself. You can put a sine wave through your amp and hook up an oscilloscope across the speaker terminals. Then adjust the gain until you have one watt across the speaker. You might need to put a known resistance in series with the speaker to measure the current to help determine power since the exact impedance of your speaker at that frequency isn't going to be known (I guess you should use a 1 khz frequency for your test signal).

After knowing the power put through the speaker, you can then measure the dB spl, which I unfortunately am not to sure about how to do. Has anyone here made such measurements?

I bet someone could rig up an arduino board to both generate signals at a variety of frequencies and take measurements of the current through the speaker by measuring the voltage across the sampling resistor. And maybe even read the signal level from whatever microphone you use for db spl measuerments. Maybe after measuring all this, you can compare the impedance and frequency response curves with those from known eminance (or other manufacturer's) speakers to figure out which model was rebranded for your amp.
Title: Re: Watts vs Volume (db)
Post by: joecool85 on December 28, 2010, 10:03:45 AM
My little Dean Markley which is running at 20watts on a 92db speaker is pushing 105db or so.  If I ran it through a 4×8 cab with four 93db speakers that would get me up to 112db – enough volume for me to do some small gigs with it.  Although more likely I would get a Fender Frontman 65R as it pushes 111db stock on it’s built in speaker, or 120db with a 4×10 cab loaded with 96db speakers.  This would do small gigs on it’s own and most larger ones simply by plugging in a 4×10 cab.  To get the 120db needed for a larger venue with my Dean I would need to plug it into 3 cabinets of the 8×10 cab variety loaded with 96db speakers…you can see at this point more wattage is necessary.  There is definitely a diminishing point and I would say that 4 speakers is it really.  Maybe 8.
Title: Re: Watts vs Volume (db)
Post by: trialabc on December 30, 2010, 04:37:59 AM
Thanks, now I get the general idea of it.

Sadly, I don't have instruments to do those testing. Perhaps I should buy the speaker with specification provided.
Title: Re: Watts vs Volume (db)
Post by: J M Fahey on December 30, 2010, 05:44:10 AM
To measure at home, you need an amplifier (*any* amplifier), download a "Pink noise MP3" , there's a few around or, worst case, I send you a sample, and a SPL meter, there's a Radio Shack one which is very affordable. U$45 the analog one; U$49 the digital one.
It's available almost anywhere thanks to those guys who want to set perfectly their "5.1" home theater systems, maybe somebody you know has one you can borrow for an hour or two.
You play your pink noise into the speaker through the "line input/loop return/Pwr amp in" , straight into the power amp , not through the preamp, and set the volume so you send 2.83 Volts into an 8 ohm speaker, 2V into 4 or 4V into 16.
In all 3 cases you are sending a nominal 1 Watt to the speaker.
You put your meter at 1 Meter distance pointing at the speaker and take the reading.
*That* is the naked truth, forget Marketing embellished datasheets.
You'll be surprised !!!
That's what they mean when they say: "X" Db SPL at 1 Watt at 1 Meter.
Without an SPL meter you can't take a numeric reading, but still can compare speakers for your own use, just play your pink noise as before, set it to 2.83 V and switch between both speakers back and forth, let your ears be the judge.
You will not only hear "volume" differences, but "response" differences, no two speakers will sound alike (unless same brand, same model, and sometimes not even so).
Do the experiment, it's very useful and mind-opening.
Title: Re: Watts vs Volume (db)
Post by: sound-pro on February 17, 2011, 03:48:48 AM
A factor seldom taken into consideration is that with higher power available for less per watt, speaker elements have grown less efficient because they have to be designed to handle more power.

There are a couple ways to make a dynamic element more able to withstand higher power. You can increase the voice coil wire size, which adds mass which lowers efficiency.

You can make a speaker able to handle further excursions of the diaphragm which presents a problem. The suspension of the cone needs to be more compliant, to be able to move to greater extremes. The means the concentrically of the voice coil in the pole piece(the magnet gap into which the VC is placed) worsens. At any given instant the position of the center axis of the VC and the pole piece is less known, with more variability. To solve the resulting rubbing that can result from less precise VC placement during it greater excursion, the gap is made wider. That decreases flux concentration which reduces driver efficiency a great deal deal.

The suspension can be made stiffer instead of increasing the pole piece gap. That also increases efficiency.

 High power speakers, as a general rule, are less efficient than speakers of the same size that are designed for less power so more power is needed for the same acoustic power coupled to the room.
An array of small, efficient speakers in appropriate cabinet at any mid point frequency will create more acoustic power per watt.
But guitars are not signal generators operating at a single frequency. The speaker/amp/guitar combination is interested in specific parts of the spectrum, not the full audio spectrum. Speaker specs such as sensitivity are general clues but since they are taken at a specified very easy to produce frequency, usually 1khz or 400hz, the spec does not tell you as much as you might want to know in predicting how loud a particular combination of cab/driver/amp will sound like.
Flat frequency response is not a major goal in guitar amps so cabinet tuning is usually not done, which can greatly influence speaker efficiency as a system. But the tone difference between cabinets becomes pretty dramatic when a driver is working into an restricted infinite baffle style cab, like open back combo's usually are.
The question is, what efficiency do you get get in the portion of the spectrum your music requires to produce the tone you want? The specs on a spec sheet for a raw driver tells very little about that. Almost any speaker can be made to sound like any other but not at the same efficiency. Compare the flat linear response from a tight pole piece system in a horn, such as the Klipshorn or even the Altec folded midrange horns, and their great efficiency to your current 200watt blaster master driver. 1 watt, through most of the audible spectrum will drive you out of the house, 60 watts fills auditoriums. But 100 watts would burn up their highly efficient drivers.
Guitarists can get a closer approximation of their desired tone character from speaker experiments than anything they can do with their amps. The harmonic spectra generated by a speaker in appropriate cab or baffle can be very muscial, particularly with tube amps because of the lack of damping tube amps with little or no negative feedback have to control the fidelity of the cone movement to the signal level. Solid state amps, usually have a high damping factor so control the absolute fidelity of cone position to signal instantaneous level much better. That means less distortion generated by the cab alone. That is great for "reproducing" sound but less desired in "creating" sound. More attention needs to be payed to the amp signal impressed on the speaker in solid state because of that great control of the sound produced than with a tube amp.
A tube amp might sound good in a particular style of play but not in another because the amp and speaker are pretty much free agents doing as they please despite the intent of the other. As a result of that fact, solid state is more versatile and can handle a wider range of material, but needs to take more responsibility for the resulting sound. There is a lot more potential, but underused, upside potential in good SS designs. Given that the speaker is less a free agent, not imparting its character completely on the sound as much as tube gear allows, the player is freer to experiment with speaker/cab designs that have greater efficiency, without worrying too much that some mysterious mojo smoke might escape.
If you can create the transfer function of the sound you want, you can get it from a wider range of speaker choices and designs, but get it you will with solid state.
Players usually do not know that they are in control of the tone and are responsible in solid state. A high power amp, much more powerful than the speaker can handle is not a bad thing....unless a player treats the combo like a tube amp/speaker.
If they focus on tone, at a moderate lower SPL, the power section will simply provide the drive and not impart any particular sound character to the signal. In that way, the same tone can be had at various power levels. So why try to overpower the speakers when you already have the tone dialed in at 1/10 th the power? Maybe because they grew up with tube gear that did not sound the same at different power levels, and the sweet spot for a lot of desired tone was between 99 and 110% of amp capacity. They HAVE to run high power to get tone. A solid state user only overpowers their cab or gets close to clipping the power section due to misunderstanding their system.
The usual comment is thst "I need to get over the drummer". That is not an acoustic power problem, that is a personality problem. The audience is not going to be left in the dark as to whether you are playing or not dropping to YOUR rig's sweet spot which is any level well under clipping of the amp and within comfortable excursion limits of the speaker. In the very few situations where the guitar just did not stand out because of volume level, it becomes a problem for the house PA system to fill the need. Because you have 400 watts of SS power does not mean any person in the audience will enjoy it any better running at clipping. In fact, just the opposite is the case, all improves with lower stage volume...vocals, guitars playing, dynamic range of the whole group etc. If the band can't "balance" themselves, but instead run flat out in all instruments, it is boring and not musical.
If the drummer can't play as a member of a team, fire them, they have no business in a team. Play in your sweet spot, not the drummer's ego trip. A club with 200 audience does not need much power to fully fill their consciousness. Anything bigger has a PA system that is designed to do that. But to sound good, you much take responsibility for the overall sound, not just on stage but also in the hall so be prepared to fire the sound guy if they are playing ego trips with power, his job is to compliment your sound by re-enforcing it, not creating it. If you are not having at least 20 db headroom in the house system your music is dead and lifeless in dynamics, but most systems by dead ear sound guys are pushed to have 3 or less total DR between average and peaks levels. Take control, it is your career.

All this comes back to speakers. With solid state the choice and design or even power are not the major tone consideration it is with tube gear, if sensible levels are used that compliment your music.

This is from the perspective of a recording engineer, EE, gear designer and audience member, not a player.



Title: Re: Watts vs Volume (db)
Post by: joecool85 on February 17, 2011, 06:09:30 AM
Holy cow!  I read that whole thing.  Very interesting indeed, and great first post!
Title: Re: Watts vs Volume (db)
Post by: sound-pro on February 17, 2011, 02:39:02 PM
Sorry about the length, sometimes I get carried away with a theme, in a stream of consciousness text, typos and all.
In all music, I am more concerned with the audience than the players or sound guy since it is apparent in live gigs the only ones not considered is the audience. The band, roadies, monitor mixer and house mixer, all have their own tastes go by but no one actually consults with or goes out into the audience to see how it sounds or if the audience is even enjoying it.
In recording I always assumed that role of being the audience's representative in the session. It seems to have worked based on the records on the walls.
Title: Re: Watts vs Volume (db)
Post by: joecool85 on February 17, 2011, 03:15:50 PM
Sorry about the length, sometimes I get carried away with a theme, in a stream of consciousness text, typos and all.
In all music, I am more concerned with the audience than the players or sound guy since it is apparent in live gigs the only ones not considered is the audience. The band, roadies, monitor mixer and house mixer, all have their own tastes go by but no one actually consults with or goes out into the audience to see how it sounds or if the audience is even enjoying it.
In recording I always assumed that role of being the audience's representative in the session. It seems to have worked based on the records on the walls.

Very interesting.  Can you share who you've done recording with/for?
Title: Re: Watts vs Volume (db)
Post by: Jack1962 on April 11, 2011, 11:56:59 AM
Great 1st post indeed Sound-Pro
however , there are many way's to get more volume out of your amp , the easiest way is to add a more efficient speaker , or multiple speakers that works fairly well.
Joecool what 100 watt amp do you have that has only 1 speaker , to compare to a 10 watt .
my 100 watt amps blow away ANY 10 watt amp with as many speakers as you want to attach to the 10 watt amp with my 100 watt am on 1 lol lol lol

                                                Rock On
Title: Re: Watts vs Volume (db)
Post by: joecool85 on April 11, 2011, 04:29:17 PM
Great 1st post indeed Sound-Pro
however , there are many way's to get more volume out of your amp , the easiest way is to add a more efficient speaker , or multiple speakers that works fairly well.
Joecool what 100 watt amp do you have that has only 1 speaker , to compare to a 10 watt .
my 100 watt amps blow away ANY 10 watt amp with as many speakers as you want to attach to the 10 watt amp with my 100 watt am on 1 lol lol lol

                                                Rock On

It was a theoretical situation pointing out how important speakers are.  That said, most 100w amps will have 2x12" speakers with a fairly high spl rating while most 10w amps will have a low spl 8" speaker, this makes the volume discrepancy quite large.
Title: Re: Watts vs Volume (db)
Post by: J M Fahey on April 11, 2011, 06:31:50 PM
Yes, that's where 90% of the discrepancy lies, 99.9% of small, cheap amps have *very* cheap (and poor) speakers.
The 10 to 100W comparison is acceptable if both are driving the same cabinet (say, a 4x12" Marshall) and there is no other loud sound source (such as a drummer) to confuse your ear.
Title: Re: Watts vs Volume (db)
Post by: bry melvin on April 12, 2011, 04:00:41 AM
one factor everyone forgets about is frequency!  I often use a Fender 25 R for my steel... you can definitely hear it in the mix.

My bassist however cannot use her 60 Watt Acoustic practice amp with it (the Acoustic Brand not FOR acoustic)
25 wats is then > 60. seemingly.

She does use that amp when we're doing unplugged stuff...doesn't own an acoustic bass. And to agree with what's said before...get a different drummer. Two dreadnoughts electric bass and a drummer works for our acoustic blues gigs. And actually when I switch to the 000 for a few songs it pierces through to the top as it is less bassy...have to back away from the mikes.

Because we simply don't hear bass as well.

On the same token, scooping the midrange out makes an amp apparently softer then the same levels clean because we hear midrange best...That's why my steel and mandolin can get through the mix with much less power.

Actually for a too loud drummer buy him electronic drums...turn his earbuds up and turn him down in the mix  :lmao:
Title: Re: Watts vs Volume (db)
Post by: joecool85 on April 12, 2011, 06:15:42 AM
Yeah, I hadn't mentioned anything about frequency since I was only referring to guitar.  But it is true.  Bassists normally need roughly 3x the wattage to get loud enough to be heard well and not be "fuzzy".

Part of that is due to not being able to hear the bass as well (human ear limitations) but alot of it is also mechanical limitations of he speaker - it is simply more difficult to produce low frequency notes, thus requiring more watts.
Title: Re: Watts vs Volume (db)
Post by: Jack1962 on April 12, 2011, 06:58:46 AM
yes bry frequency makes a world of difference the higher frequencies will ride on top of the low frequencies.
yes in theory joecool and jm this is true , but in practice it isn't , it is true that between a 100 watt and a 50 watt amp you won't hear much difference in volume. I have a Marshall JMP and a MG10 and 2 1960 cabs if ya want to come and prove your theory  :lmao:

                                          Rock On
Title: Re: Watts vs Volume (db)
Post by: DavenPaget on September 11, 2011, 12:27:39 PM
yes bry frequency makes a world of difference the higher frequencies will ride on top of the low frequencies.
yes in theory joecool and jm this is true , but in practice it isn't , it is true that between a 100 watt and a 50 watt amp you won't hear much difference in volume. I have a Marshall JMP and a MG10 and 2 1960 cabs if ya want to come and prove your theory  :lmao:

                                          Rock On
Ears naturally compress high volumes :D
So 100 watts is actually 2x louder then a 50w much further away . ( like 20m )
Title: Re: Watts vs Volume (db)
Post by: Puguglybonehead on September 18, 2011, 01:07:24 PM
As a guitarist, I've come to realize, not that much power is really needed. My band is a basic old-school punk band. (we started playing in 1978) Drums, bass, guitar, singer (if you can actually call what he does "singing"). In the past, I would use an 80 watt, 80 lb Traynor Mark 3 combo. This thing could blast a Fender Twin off the stage, no problem. It was way too much power! I only had occasion to turn it above 3 once. That was at an outdoor gig at Nathan Phillips Square.

I realized how much I hated hauling this 80 lb monster around. Now I use an old 20 watt Supro, a small combo with a single 10" speaker. It's so small, I can carry it to gigs in my backpack. I installed the best 10" speaker I could afford, an Eminence Ragin' Cajun. It's rated at 100dB SPL sensitivity. I've found this setup to be more than enough, even with an aggressive drummer. No problem being heard. Strangely enough, I'm still not turning this amp up much past 3.  ???

I would think that a 20 to 30 watt amp in a combo with something like the 12" Eminence Wizard (103 dB SPL) would be more than enough for any situation. In fact, I'll bet that a speaker like that could make a decently designed 10-watt amp be heard just fine.
Title: Re: Watts vs Volume (db)
Post by: DavenPaget on September 18, 2011, 01:44:46 PM
As a guitarist, I've come to realize, not that much power is really needed. My band is a basic old-school punk band. (we started playing in 1978) Drums, bass, guitar, singer (if you can actually call what he does "singing"). In the past, I would use an 80 watt, 80 lb Traynor Mark 3 combo. This thing could blast a Fender Twin off the stage, no problem. It was way too much power! I only had occasion to turn it above 3 once. That was at an outdoor gig at Nathan Phillips Square.

I realized how much I hated hauling this 80 lb monster around. Now I use an old 20 watt Supro, a small combo with a single 10" speaker. It's so small, I can carry it to gigs in my backpack. I installed the best 10" speaker I could afford, an Eminence Ragin' Cajun. It's rated at 100dB SPL sensitivity. I've found this setup to be more than enough, even with an aggressive drummer. No problem being heard. Strangely enough, I'm still not turning this amp up much past 3.  ???

I would think that a 20 to 30 watt amp in a combo with something like the 12" Eminence Wizard (103 dB SPL) would be more than enough for any situation. In fact, I'll bet that a speaker like that could make a decently designed 10-watt amp be heard just fine.
The reason why people think tube is louder then solid-state , is because . well SS practice amps are always given *s!!t* speakers .
10W can do some serious *s!!t* with a 103db monster . ( no less 30W )
but i think it can at most do ... 105db .
i don't know about 30W , though . But my insane 30W DSP amp ( i have never been able to crank it up above 2 ) , came with a unnamed mad 10" 98db , can do some serious sound . It even won those dumb AC30's
Title: Re: Watts vs Volume (db)
Post by: joecool85 on December 29, 2011, 01:27:26 PM
I fixed some math and stuff in the first post.  You can't just add speakers to get more volume.  If you take two 96db/watt speakers and run them together each with their own 1watt source, you would come out with 99db.  If you ran them together splitting a 1 watt source, you would still only get 96db.  This is assuming a large distance between the speakers (say one on each side of the stage or farther apart).  If they speakers are in a single cab, they will work together acoustically, producing more volume per watt and also producing more vibrant lower tones due to the increase in cone area.

So the big advantage of more speakers is two fold: tone (yes, it will sound different) and maximum wattage handling.

I apologize for any confusion.

The key thing to remember is use efficient drivers.  It doesn't matter if you have a single 8" or two full 4 x 12" cabs, the more efficient the drivers, the more volume you get.  Look for at least 97db, ideally 100db or better.
Title: Re: Watts vs Volume (db)
Post by: its_cabs on June 29, 2012, 10:49:54 PM
Sound Pro,
go ahead - 'spress yerself! Couldn't agree more. It's the sound, not the volume, that leaves an impression. I mean, even Cream, loud as they were, was very considerate of the sound, all well balanced and clear for each player. Conversely, after weeks of practice, and only one warm up gig, when my nephew and I finally got a good tone dialed in at this club for our Costa Rica debut, after 2 or 3 songs I noticed the sound was all messed up. I told the promoter to track down the culprit. Seems the club owner, accustomed to louder, more aggressive hard rawk than our own down home, mostly accoustic southern blues thing, kept sneakin over and cranking up the board - after we had it set just right for the room. Oh, well, he did recently ask me when I'm coming back...cabs
Title: Re: Watts vs Volume (db)
Post by: Axeslinger61 on July 15, 2012, 08:27:52 AM
Fascinating. Quite informative, as well. Who do y'all recommend for a manufacturer of efficient, reasonably priced speakers? Back when I was gigging regularly as a bassist, the Peavey Black Widow was one of the most efficient speakers out there-but I wasn't that crazy about the tone. Nowadays, I'm playing guitar primarily, and am thinking about downsizing my rig, so speaker efficiency is a definite concern.
Title: Re: Watts vs Volume (db)
Post by: Puguglybonehead on August 01, 2012, 10:23:18 PM
For speaker efficiency, have a look at some decent quality ceramic speakers. The "vintage-tone"snobs seem to love alnico, but those speakers are seldom as efficient. If you can find the full specs (including the all-important SPL rating and frequency range) then you can get some idea.

Eminence make really efficient speakers, full specs available. So do Weber. (but they don't publish their full specs) Also, decide on which speaker size works best for you, tone-wise. The larger the speaker, the better chance of it being more efficient. Lots of loud 15-inch, 12-inch and even 10-inch speakers out there. 8-inch or smaller and you're starting to lose out.

Read lots of the reviews online. They may seem subjective, but they've usually steered me right. Anyways, Eminence and Weber both make great sounding, loud speakers.
Title: Re: Watts vs Volume (db)
Post by: KMG on August 02, 2012, 02:41:10 AM
Don`t forget another important thing - specific "voices" of different speakers.
One speaker maybe good for vintage sound but poor for modern.
http://www.youtube.com/watch?v=jWK0sa7tlfI
Title: Re: Watts vs Volume (db)
Post by: QReuCk on August 02, 2012, 03:42:47 AM
Most of "vintage" speakers do have a huge boost (sometimes 3 to 6db more than the overall ratting) in high mids (in the region of 3KHz to 6KHz). I do think you should really be carefull when selecting a speaker based on efficiency. Try to find response curves and see if most of this efficiency is located in frequencies you don't want to push too far. Overwize you will need to filter them out somehow and obtain an overall efficiency of the speaker + filters that is not what the overall spl indicates.
E.g. if your tone is more in the 200 to 2000 Hz frequency range, a speaker with overall 100 db/W.m with a speep boost at 4KHz won't be more efficient for you that a 98db/W.m one which have a boost precisely in the frequency range you seek.
 
Title: Re: Watts vs Volume (db)
Post by: Steve Dalllman on March 19, 2013, 07:38:33 PM
Many if not most of modern guitar speakers are in the high 90's to low 100's in dB's. Even high excursion bass speakers are usually in the high 90's but the compromise is usually less highs.

This is for 12's and 15's. As you go smaller, especially with 8" and 6 1/2" speakers, the sensitivity is often lower, in the 92dB range.

Most manufacturers will not only give all the specs, but will include a frequency graph. Every speaker will have a rather shallow low end rolloff, relatively flat across the mids, and then have a large peak between 2 and 4kHz followed by a treble rolloff that may extend gracefully to 5-6kHz or beyond, or be rather ragged.

A guitar pickup is similar, with it's "resonant peak" producing a characteristic tone.

Bass and PA speakers will usually use a crossover selected to be below that large peak, bass less so.

Tube VS SS watts...an endless argument. Let me give my take. When you reach the limits of a SS amp, there won't be much beyond it's limits. A 100watt amp may be rated 100 watts @ .05% distortion. Once the rails are hit, there may be nothing much left above a certain point.

With a tube amp rated at 100watts @.05% distortion, may be capable of 200 watts @ 30% distortion and sound great doing it.

The tube amp may keep putting out far more than it's rated power, at a very high distortion level, but still sound good. With the SS, the possible output will be limited by it's power supply limits, and at high distortion, may not sound very good.

My 12 watt Princeton Reverb will put out a lot more than a 15 watt SS amp using a TDA2030 power amp chip...a LOT more.
Title: Re: Watts vs Volume (db)
Post by: Roly on March 20, 2013, 07:20:10 AM
Quote from: Steve Dalllman
A guitar pickup is similar, with it's "resonant peak" producing a characteristic tone.

Just to remark that I've done a bit of modeling of guitar pickups where it seemed that the input impedance of many amps was too low and seriously damped this self-resonance, and lately building some high impedance buffers which has confirmed that impedances in excess of 1Meg (e.g. ~5Megs) lets the pickups "sing" more, are more tonally rich (and that's into a s.s. amp).  Adding shunt capacitance to bring this resonance down in frequency, VariTone style, is something I'm also fooling with.

Quote from: Steve Dalllman
Tube VS SS watts

Not taking sides, since I use one of each, but Rod Elliott at ESP has some interesting views on the very different output impedances of each.

Another factor is that when a s.s. amp clips it presents the speaker with an effective short circuit, and thus high damping, but when a valve amp with an output transformer clips di/dt goes to zero and it's more like an open circuit; the upshot of which is that during clipping the speaker in one is highly damped while in the other it's effectively cut loose.
Title: Re: Watts vs Volume (db)
Post by: Jack1962 on April 02, 2013, 06:48:10 AM
Great explantions on this subject  :dbtu:

I love hearing JM and Joe lay the info down for ya , so here's a twist to this , why is a lower wattage tube amp louder than higher wattage solid state amp , thru the same speaker.


Title: Re: Watts vs Volume (db)
Post by: Roly on April 02, 2013, 11:00:12 AM
Again Rod Elliott at ESP has an interesting take on this;

http://sound.westhost.com/valves/valve-trans.html (http://sound.westhost.com/valves/valve-trans.html)
http://sound.westhost.com/valves/valve-trans2.html (http://sound.westhost.com/valves/valve-trans2.html)

There are a number of factors in play, but the essence of this observation is that a valve amp has a much higher output impedance than a transistor amp, perhaps as much as 20 ohms compared to a fraction of an ohm.  This results in a valve amp behaving somewhat like a current source, while a transistor amp behaves much more as a pure voltage source.

Into a resistive dummy load there is little apparent difference between the types, but the situation changes considerably when they drive a real world loudspeaker load.  The impedance of a real loudspeaker cab is anything but constant across the audio spectrum and the drive voltage available from a valve amp tends to track these changes of impedance and thus seems to have more headroom to overload than a transistor amp of the same power.

Apart from technical considerations, I have been running a 60 watt valve amp and a twin-50 watt solid state amp, both homebrew, for guitar and keys/synth into the same cabs for many years now, and as a player the difference is very apparent when I have been forced for some reason to cross over and use the valve amp for keys or the solid-state amp for guitar.  Running keys into the valve rig results in a more or less dirty/muddy output at all levels, while running guitar into the transistor rig has a "distortion wall" at overdrive that sounds downright nasty.

The inherent and progressive distortion of valves sound better with tenor guitar, specifically, but keys, PA, and I note bass guitar, sound better with the ample clean power of a solid-state amplifiers run below clipping.  Bass rigs frequently contain some form of signal compression as well as very large amplifiers so they rarely clip.

Title: Re: Watts vs Volume (db)
Post by: Jack1962 on April 02, 2013, 07:27:13 PM
The output impedance from the tube is between 3k ohms and 8k ohms depending on what tube you are using. however I agree with most of what you are saying , the real difference is drum roll please , the tube is indeed a constant current source due to the output transformer , the transistor amp has it's signal dump directly onto the speaker. Myself I have and use both types tube and solid state I prefer the solid state for keys because the amp I'm using is a Peavey Musician you can use it for anything , best frequency response I have ever seen from a stock production amp. for guitar and bass I usually use tube amps because of the output power , I generally don't use anything larger than a 50 watt guitar amp for Bass I use my vintage Ampeg SVT with a 8x10 cab and a 15 jensen that I really don't remember where it came from I"ll put it up against any 500-1000 watt bass rig anytime lol

Title: Re: Watts vs Volume (db)
Post by: MTmopars on April 05, 2014, 10:08:39 AM
Such a good thread. While I am fairly novice to guitar amps and their application, I used to compete in car audio and many of the same principles apply here and have been stated.

Every 3dB is doubling the volume. So to double the volume get a 3dB more efficient speaker, double the cone area, or double the power. In car audio completion you could also port the enclosure to give 3-9dB boost at the frequency the port is tuned for.
Title: Re: Watts vs Volume (db)
Post by: g1 on April 05, 2014, 01:37:52 PM
Every 3dB is doubling the volume. So to double the volume get a 3dB more efficient speaker, double the cone area, or double the power.
No.  It was established that it takes 10db to double the volume in the first post  :).
The 3db boost in volume from the methods you mentioned does not double the perceived volume.
  In car audio competitions you measure SPL.  Does a given system with a 200W amp sound twice as loud as the same system with a 100W amp?
Double the power does not equal double the volume, you need 10db increase to sound twice as loud.
Title: Re: Watts vs Volume (db)
Post by: MTmopars on April 05, 2014, 04:13:52 PM
I stand corrected on part of my post. 10 db is doubling perceived volume. 3db is the gain from doubling power or speakers. It has been about 10 yrs since I was active.
Title: Re: Watts vs Volume (db)
Post by: Anomaly on December 27, 2014, 11:34:40 AM
I'm straying a bit here but.... I think perceived volume has a lot to do with the amplifiers natural EQ curve, cause if an amplifier has a good mid range response, and is of good quality it is going to be LOUD. I've owned many different amplifers, tube and solid state, and the higher quality solid state amps like the Randall RG's and Ampeg SS and VH series heads through a good cab are just as loud as equally rated tube amps, and they cut no problem too (when dialed in right). No one can say an Ampeg SS-150 or Randall rg100es can not cut through a mix, they cut through like butter.