Tube wattage in relation to decibels

[PRR]

A story.

Back in the 1970s, the school bought an Ampeg VT-40. It was two bottles cranked-up to 595 volts and rated 60 Watts. This model has an open-back four 10" cabinet with fairly efficient cones.

It was REAL DARN LOUD. (VT-22 was the same chassis with four bottles; I hope I never meet one.)

And it lived (and died) way too close to the edge of disaster.

The last disaster took out the power transformer.

I re-built with a 400V supply. I cathode-biased, shedding another 25V of supply and encouraging more graceful failures.

It came out near 20 Watts.

60W/20W = 4.8dB "less"

With the four 10", it's still REAL LOUD.

It isn't the dreaded barn-rocker that it used to be, but is more than ample with a big Jazz Band.

The frontal area of air-smacker you can carry makes near as much difference as the Watts you can carry. One 12" cone is 70sq.in., two 12" is 140sqin, one 10" is 50sqin, four 10" is 200sqin. While one modern 10" will easily carry my downrated 20 Watts, it would be a much less impressive amp.

And working at ~5W clean 9W fuzz each, those 10" drivers will probably last another 30 years.

The flip-side is that a four-10" is a beast to move. In this case, it rarely leaves the building, and the users are young, and it isn't my problem.

We also have a Traynor YBA with 18 clean watts and one 15" (130sqin) cone. (Sadly not the original Norelco, a beefy slug stolen from a high-power amp.) It is impressive for a "good value" amp, and did well with/against mild jazz drummers, but isn't in the same league as the 20W ex-VT-40.

 

[CJ]

Please use only watts and loudness for guitar players.
Don't play the "db", card, we run and hide.

Standard "git player math" is square the watts to double the sound.

Close enuff to out hustle a sales geek on the floor at git center.
But from 10 to 100 watts is gonna mean more speakers, so this kind of counteracts the ear wax that never gets cleaned out, not to mention the tinitus.

Nobody mentioned what happens when you connect the 15 watt ac 15 to 2 12's, which is what I run. Different speakers, for different phase differentials, (delay), adds dimension.

I think doubling the speakers is a much better way to get louder.

I use to measure watts as me jamming down on some Montrose , with a slow needle voltmeter on the speaker cone, it jumps from 10 watts to 100 on a good twin reverb, so what is real watts anyway?
It changes every second in a git amp, so then impulse might mean something, if you double your tubes but make the pwr xfmr not twice as big, and thus lose stiffness in the supply, do you lose power?
Think stomp box.

So stiffen up a power supply, raise the B+, to get an "apparent" increase in loudness.

Nobody listens to loud music any more, all us old boomers are switching to old Martins, so if you can get people in a room with a good AC 15, you are a better geek then I.

Outdoors?
Well, all bets are off.
Bring on the stacks.

 

[Guest]

[quote author="PRR"]
In the Big Geetar Amps' heyday, PA systems sucked and the g-amps were expected to fill the room without help. That's why 2*100W + 2*8*10" Marshall Stacks happened: they will fill a football stand with level the PA systems of the day would not touch. Now that everybody and his kid brother has a 4,000 Watt PA system, the custom is for guitarists to carry a 5W-20W amp with "the right sound", and mike it to the PA system for kilowatt delivery.

[/quote]

By the way, speaking of speakers, I'm laughing reading such descriptions:


McIntosh Laboratory Reference System
Put together the ultimate high-end sound equipment from McIntosh (www.mcintoshlabs.com), and you get the Reference System. This $191,000 melange is only available at a double handful of dealerships on the continent. The skyscraping XRT2K line array speakers feature six woofers, 64 midranges, and 40 tweeters. Each. The MDA1000 DAC converts your ordinary 16-bit CDs to amazing 24-bit, 768KHz audio. And the C1000 controller/preamp set lets you choose vacuum tube or solid-state amplification—or both. In total, 2,000 watts of power await your command. Thumping trip-hop? Or seductive world lounge? I have a feeling you won’t care what you’re listening to. Even “Fish Heads” will sound phenomenal. And if you’re more interested in a full-on home theater with a projector and eight times the wattage, pony up half a million for McIntosh’s Ultimate Screening Room.

Guys definitely understand well what they are doing; but why did they put 2 rows of midranges on a big distance to each other with tweeters between them? for worse (I mean more frequency dependent) horizontal directivity pattern?
And what for they need 40 tweeters? To mount them on a flat surface then power tap'em? If they mount half of them on an aluminum frame they could easily curve them mechanically, anyway it is a casted frame...

...and what they are going to do with 2 kilowatts, if they have 64 (sixty four!) midranges? 100 times less of power would be more than plenty for a living room of any imaginable size!

...and re-sampling of CD rate... What's the reason?

...and why to switch from tube to solid state and back, why not hybrid for mid and high, and solid state for bass?

I can explain that only like "Twice of materials plus some loss of quality equals 20 times more of price".

 

[aletheian-alex]

I have this little calculator stored away in my bookmarks for those situations.

http://www.myhometheater.homestead.com/splcalculator.html

 

[Guest]

[quote author="aletheian-alex"]I have this little calculator stored away in my bookmarks for those situations.

http://www.myhometheater.homestead.com/splcalculator.html[/quote]

For line arrays results will be different.