6db.
Every three decibels of volume requires the power output to double.
in contrast, a perceived doubling of volume is something like 10db (I forget exactly how much).
2 Likes
Yes
3 Likes
Thanks, that helps
1 Like
+1
Itâs 10
3 Likes
Is there any way to guesstimate something like:
125w amp full power would be equivalent to 250w at 7/10 and 500w at 5/10, or are there too many variables to make a generalization like that.
and I donât mean 7/10 and 5/10, just using numbers to fill in, if you know, what would they be
1 Like
I wouldnât be able to guess it.
1 Like
Here is what I used to use for stereo amps. It is a generalization. It also assumes some things. One is you have to know the sensitivity of your speaker. A speaker that is 85 dB sensitivity (average home speaker) means 1W will give you 85 dB with your head 1 meter in front of it. most guitar and bass speakers have a higher sensitivity than this, and thus will play louder with less watts. (however sensitivity isnât usually given by bass cab manufacturer like it is in home audio speakers). holding your head 1 meter in front of a speaker is not realistic in the real world, and sound diminishes quickly with distance. so the farther away/bigger the room the more watts you need, which is why the rolling stones require a billion zillion watts in yankee stadium.
anyhoo, hereâs the chart. explanations will follow.
Watts to dB
1W = assume 85dB/w/m = 85dB
(so 1W gives you 85dB at 1 meter away from speaker)
2w = +3 dB = 88dB
4w = +6 = 91dB
(notice we have to double the watts each time to get an additional +3dB)
8w = +9 = 94dB
16w = +12 = 97dB (2x loud as 1w)
32w = +15
64w = +18
the sweet spot IMO:
**128w = +21 = 106 dB (2x loud as 16W)
**256w = +24 = 109 dB
**512w = +27 = 112 dB
1024w = +30 = 115 dB (2x loud as 128W)
2048w = +33
4096w = +36
8192w = +39 = 124 dB (2x loud as 1024W)
some sample spl readings at performances:
New age: 60-70 dB
Folk: 75-90 dB
Jazz: 80-95 dB
Pop: 90-95 dB
Classical: 100 dB
Rock: 95-110 dB
Heavy metal: 110 dB
Itâs kind of accepted that the smallest increase in dB that can be easily heard is +3 dB (i.e. increasing 5 dB to 8 dB sounds âa little louderâ). In order to get this you need to DOUBLE the ampâs watts. A +10 dB increase is perceived as twice as loud. So as you can see as amps get bigger you get insane diminished returns. Which is why I think buying huge amps is a waste of money. Some people will argue that a gigantic amp gives you added âheadroomâ (peak transients/loud short bursts) but the usefulness of this seems to be controversial amongst engineers (and basses donât have nearly as much peaks as guitars). To me, for most people the sweet spot zone for amps is marked above, which is why most bass amps are between 100-500w.
tldr: get a 500W amp. do you need a super monster 1000W amp? itâs only a little louder than a 500W amp. also notice you can use this chart in interesting ways. want a practice amp? 15W is almost as loud as 50W and might be a lot cheaper. (all things being equal of course. a low quality speaker may sound like crap for reasons that have nothing to do with itâs power). play jazz? pick a smaller lighter cheaper amp that puts out around 100W.
Crown amplifiers has a great article on this.
2 Likes
@itsratso I read the whole article.
Now I want to play a coffee shop with 10,000 watts and a double stack of 105 db sensitivity speakers. 
Seriously though, that was a great article.
3 Likes
I think it has to do with what resource the amplifier runs out of first. If it drives down to 4 Ohms it has the current capacity. If it can supply the same power at 8 Ohms it has to also have the voltage capacity.
2 Likes
not a lot of manufacturers publish the sensitivity ratings of bass cabinets, but i have a feeling they are much more sensitive than home speakers. i found a 1x12 cabinet that was rated at 97dB 
thatâs close to twice as loud as a comparable home stereo speaker. high sensitivity home speakers became a big thing when audiophiles would fall in love with low power tube amps, where you could drive 110 dB speakers to insane levels with 8 or 10 watts. also a big thing in japan, where stereo guys sit 2 feet in front of their stereos (nearfield listening) because apartments are so small.
4 Likes
Thatâs classic Bradford Benn. I guessed him after the first sentence. He definitely knows what heâs talking about. Samsung bought Harman(Crown) and very siilily let him go. He landed as the manager of technical systems for Universal Studios theme park creative division.
4 Likes
Audiophiles here are as⊠audiophile as you would expect. Another way they go are extremely high power electrostatic ribbon headphones, like Stax.
So you see guys running their stereos in to a $3k 50W 6SN7-based tube headphone amp like this, just to drive their 'phones.
Audiophiles: the same everywhere
2 Likes
3 Likes
I mean, FFS:
â Impedance: 170 KΩ (at f = 10 KHz)
1 Like
Pffft pocket change.
2 Likes
I just literally LOLed at Beyerâs $1200 pair claiming they use âTesla-based technologyâ.
2 Likes
3 Likes
itâs almost like they are trolling audiophiles hard with that, and if so, I fully approve 
2 Likes
yeah thatâs what I though, it canât be serious
2 Likes
@DaveT Can you offer any tips on finding a power amp that will do 250 watts @ 8 Ohms?
Iâve come across some on the used market that are a lot cheaper than the ones in the list above. Although I would like something smaller, going with a cheap rack mount would be easier on my wallet.
1 Like