confused about watts and stuff

Slappindabass48 · #1 09-01-2011, 05:28 PM

okay, ive been playing bass for years, and i know im gunna sound like a huge noob right here. but whats the difference between wattage and volume?

ive had a 1000 watt head and it was the same volume as my 450 watt and i cant figure it out.

that aside, whats the difference in wattage capability in cabs?

i have a 450 watt svt 3 pro, if a 410 ampeg cab can support 600 watts, and my 810 can support 800 watts, do they put out the same volume?

rad bassman · #2 09-01-2011, 05:41 PM

for answers to these questions, and more... see FAQ's sticky threads

AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

Red Planet · #3 09-01-2011, 05:44 PM

Watts is a neighborhood in LA where Fred Sanford lives.

GrowlerBox · #4 09-01-2011, 05:47 PM

Watts are units of electrical power -- in principle simple, calculable and make for good advertising copy (see recent controversy over TC Electronics).

"Volume" is a far more complex entity, assuming that by volume, you mean "loudness" (not exactly the same), which is the result of the interaction between the frequencies produced by your preamp, the power generated by your power amp, what your speaker can do with that output, the environment into which that speaker produces sound waves, and finally your ears and central acoustic processing unit (i.e. "brain").

As a very basic rule of thumb, if everything else above remains the same, approximately doubling the power (e.g. from ~450 W to ~1000 W as in your example above) will add around 3 dB to your loudness. This is certainly audible, but will not make an appreciable difference in a live performance setting. In order to double the loudness (i.e. to add 10 dB), about 10 times the power output is required, i.e. 4500-5000 W to double the loudness of your 450 W amp.

JimmyM · #5 09-01-2011, 05:51 PM

Quote:

Originally Posted by Slappindabass48

okay, ive been playing bass for years, and i know im gunna sound like a huge noob right here. but whats the difference between wattage and volume?

ive had a 1000 watt head and it was the same volume as my 450 watt and i cant figure it out.

that aside, whats the difference in wattage capability in cabs?

i have a 450 watt svt 3 pro, if a 410 ampeg cab can support 600 watts, and my 810 can support 800 watts, do they put out the same volume?

Nope. The 810 will put out 6db more than the 410 because of twice the speakers, and 6db is pretty significant. And wattage really won't give you a giant bump in volume because it takes 10x the wattage to sound 2x as loud. If you're looking to be loud, it's always about speaker area and cone travel and not so much wattage, though it does play into it.

GrowlerBox · #6 09-01-2011, 06:02 PM

Quote:

Originally Posted by JimmyM

Nope. The 810 will put out 6db more than the 410 because of twice the speakers, and 6db is pretty significant. And wattage really won't give you a giant bump in volume because it takes 10x the wattage to sound 2x as loud. If you're looking to be loud, it's always about speaker area and cone travel and not so much wattage, though it does play into it.

I forgot the second part of the OP's question ...

The 6 dB increase is due both to the doubling of the speaker area (~3 dB) and doubling of the power (~3 dB), assuming that your 410 has an average impedance of 8 ohms, and your 810 has an average impedance of 4 ohms.

The "rating" of speaker cabinets in watts provides little information regarding how much power the speaker can actually use to generate loudness -- in almost all cases, it refers to the amount of power it takes to damage the voice coils through generation of heat. On average, speakers can use about half their "rated" power to produce useful sound pressure.

Nothing's ever simple. If it looks like it is, you probably shouldn't believe it.

JimmyM · #7 09-01-2011, 06:23 PM

Growler, I could be wrong, but I thought Bill FM always said that doubling your cabs gives you +6db by itself.

Also, Ampeg is one of the few companies that rates their cabs honestly, so when they say an 810 takes 800w, that's about what it takes real world.

fdeck · #8 09-01-2011, 06:28 PM

I think Growler is right. The 6 dB represents a doubling of swept air volume, which requires a doubling of input power.

projectMalamute · #9 09-01-2011, 06:33 PM

You get 3dB from the extra speakers and 3dB from the extra wattage.

This assumes you are adding 4 identical speakers.

If you are comparing, say, an 810e with a 410HLF you can't make these kind of assumptions. At 50Hz I'd expect the HLF to be louder.

GrowlerBox · #10 09-01-2011, 06:33 PM

Quote:

Originally Posted by JimmyM

Growler, I could be wrong, but I thought Bill FM always said that doubling your cabs gives you +6db by itself.

Also, Ampeg is one of the few companies that rates their cabs honestly, so when they say an 810 takes 800w, that's about what it takes real world.

Hey Jimmy -- as I understand it, doubling the acoustic power (however that's achieved) produces a 3 dB increase. There may be other advantages in terms of improved reproduction of low frequencies, and also getting speakers nearer your ears, of course. Maybe Bill or one of the other acoustic engineers will come and break the tie!

And I take your point about Ampeg cabinets -- very much in the minority, unfortunately.

Edit: these guys are quick!

will33 · #11 09-01-2011, 06:37 PM

3db comes from doubling the cone count, 3 more comes from the power increase from halving the impedance ( doesn't apply to tube amps ). There's an acoustic coupling that gets you a couple more db in the lows. Too complicated for me to explain but some increase below whatever frequency's wavelength = the center to center distance of the farthest apart cones.....something like that but don't quote me on it. There's the thing where a taller stack puts speakers closer to ear level making it seem louder.

babebambi · #12 09-01-2011, 06:42 PM

Doubling the speaker surface area alone gives you +3 dB.

That usually means dropping of the nominal impendance to half, which could potentially double the power output of an SS amp. That's where the additional +3 dB comes from.

vin*tone · #13 09-01-2011, 06:44 PM

Here it comes.

Red Planet · #14 09-01-2011, 06:58 PM

I just wonder what kind of amp Jimmy likes. It's on the tip of my tongue. I just can't think of it right now. Oh well it'll come to me later.

JimmyM · #15 09-01-2011, 07:16 PM

Quote:

Originally Posted by Red Planet

I just wonder what kind of amp Jimmy likes. It's on the tip of my tongue. I just can't think of it right now. Oh well it'll come to me later.

Ha!

**IvanMike** · #16 09-01-2011, 07:28 PM

The whole doubling the cab size (e.g.) using two identical 8 ohm cabs vs one) results in a theoretical Maximum of +6 dB. This of course assumes doubling the wattage, which we all know never happens as thermal (and other) considerations in amps mean that the power output of an amp @ 4 ohms is almost never twice what it is @ 8 ohms. +4-5 dB is a lot more realistic. Of course stacked vertically this will help dispersion quite a bit, so the apparent volume increase in the FOH may be closer to +6 dB.

+1 to the info concerning doubling the wattage gives a +3 dB increase in volume (assuming the speakers can take it and don't max out in thermal capacity), and FWIW - to the OP, a 3 dB difference is generally considered the minimal volume difference that a person can hear.

Edit - the big advantage to an increase in wattage (especially in SS amps) is an increase in headroom, generally for transients - so you are less likely to clip the poweramp (which in SS amps sounds really bad)

will33 · #17 09-01-2011, 09:27 PM

Quote:

Originally Posted by Slappindabass48

i have a 450 watt svt 3 pro, if a 410 ampeg cab can support 600 watts, and my 810 can support 800 watts, do they put out the same volume?

The amp puts out the power and the speaker accepts it. A higher watt speaker does not draw more power. In speakers, the watts indicate how much power in the form of heat the voice coil can take before it burns up.

How loud the speaker can play is a function of it's sensitivity (spl rating) which how loud it will play with 1 watt of power measured 1meter away. That varies with frequency. In combination with it's excursion (xmax rating) which is how far it can move back and forth before it can't make anymore bass.

In your 410/810 example, the 810 would play 3db louder provided the exact same drivers in the exact same design, just twice as many in twice the box. If they use different drivers and/or different box designs, the difference could be something different entirely.

Look at the response graph here for example. It's a commonly used bass cab driver.

Speaker Detail | Eminence Speaker

A one number spl rating is an average. The driver actually plays louder or quieter at different frequencies.

funkinbottom · #18 09-01-2011, 10:14 PM

Doesn't voltage gain play a role in the volume of an amp? A friend of mine has a QSC power amp, and I have a Carvin power amp. He has way more watts, yet my amp is much louder. (using the same 8 ohm cab and same preamp) My amp has 35db voltage gain, his is 28db voltage gain. I'm no expert but he is. Has worked as tech for large high end audio firms, and that's the explanation he gave me. So, Maybe your 450w amp has considerably more voltage gain than the 1000w.

Or maybe my friend doesn't really know, but certainly makes sense.

HolmeBass · #19 09-01-2011, 10:31 PM

So for the OP, just to clear some stuff up, the wattage rating of a cabinet has nothing to do with how loud it is, although if it can take more watts it can probably get a bit louder by turning your amp up.

Sensitivity ratings for cabinets are supposed to tell you how loud it is - usually in terms of db produced with 1 watt of power at a distance of 1 meter - but the way in which various manufacturers measure sensitivity makes it quite difficult to compare based on that number. It's much more of a ballpark figure. Sensitivity ratings look something like: 98db @ 1w/1m. That is, 98 db for 1 watt of power measured 1 meter away.

The issue comes when considering the frequency content/spectrum of the test signal used- white noise, pink noise, a 1 kHz sine wave, etc. They usually don't tell you and it can make a significant difference on the resulting value.

Cristo · #20 09-02-2011, 10:50 AM

Slappindabass,
If you haven't noticed already, it is a complicated topic.

In simple and not entirely accurate terms, (which I'm sure will be corrected by others in many pages of debate to follow) all other things being equal, your 1000w amp is actually only capable of being a small bit louder than your 450w amp.

Doubling the power of the amplifier produces a change in volume that is only slightly noticeable by most people (again ignoring the effects of many other things relating to the amp and cab).

In other words, the 1000w amp IS only a little bit louder than the 450w amp, because of physics and math. It probabaly is capable of sounding better at higher volumes though.