"dbw"??

[Coytee]

If a power amp has a rating of:

8 ohms, 400 watts (26 dbw)

4 ohms, 650 watts (28 dbw)

2 ohms, 800 watts (29 dbw)

Exactly what does the dbw mean and how is it calculated and all that nice stuff? How is it correlated to ohms or watts? Doesn't look linear to me given what I see.

[formica]

From the web: Logarithmic representation of a power level reference to 1W of power.



For audio, it's basically the power output from the amp related to the
db outputted by the speakers. This can give a more realistic
feeling for the power increase between two amplifiers than the typical
Watt rating. We already know that every doubling of the power (in
Watts)... only increases the speakers output by 3db due to decibel's
logarithmic scale. Note how dbW rating on the 400W and 800W are
3db apart?



So what can you do with this number?



Lets say you have Lascalas with a 105db/1W/1m and an 8ohm rating... and
your amp actually puts out a clean 50W into 8ohms or ± 17dbW. So
this amp will push your speakers to a 122db (105 + 17) maximum output
if we were ignoring power compression and other factors of the like.




Make any sense?

ROb

PS: LaScalas do have a maximum 121db output btw... but that's a whole different story...

[formica]

Oh... and to calculate the dbW... given it's referenced to 1W (ie:
1W = 0 dbW) you get the following 3db increase for each doubling or
watts:

1 W = 0 dbW

2 W = 3 dbW

4 W = 6 dbW

8 W = 9 dbW

16 W = 12 dbW

32 W = 15 dbW

64 W = 18 dbW

128 W = 21 dbW

256 W = 24 dbW

512 W = 27 dbW

1024 W = 30 dbW

[Coytee]

Ok, so if I understand you...

Let's say the Jubes are 110 1w/meter (I think they're less though)

If I wasn't bi-amping, then I could at max 4 ohms, add another 28 db's to that or take them to 138 db/1 meter?

Yikes.... their sticker says they can handle 1200 watts (sticker on bass bin)

[WMcD]

If a power amp has a rating of:

This overall is the dB above one watt. And remember that 10 Log P1/P2 = dB and here the P2 is 1 watt.

8 ohms, 400 watts (26 dbw)

10 ^ 2.6 = about 400

But you can do this in your head knowing that 10 dB = 10 time power, and 20 dB = 100 times power. 3 dB = 2 times power. So you know you're at 20 plus 3 plus 3 or 100 and a doubling and a doubling.

4 ohms, 650 watts (28 dbw)

2 ohms, 800 watts (29 dbw)

Exactly what does the dbw mean and how is it calculated and all that nice stuff? How is it correlated to ohms or watts? Doesn't look linear to me given what I see.

[formica]

If I wasn't bi-amping, then I could at max 4 ohms, add another 28 db's to that or take them to 138 db/1 meter?

In theory, yes... BUT...

Unfortunately speakers become less efficient with increased output... so in reality it's less. That would explain why the LaScala (again 105db/1w/1m) is rated for 100W but a max output of only 121db... when in theory it should be about 125db. There is also the fact that many speakers will bottom out (or have their suspension extended to their max) before hitting their maximum power rating... further reducing the maximum output.

but that is the gist of it... (don't you hate all the exceptions?)

ROb

[JohnA]

I'm going to pile on here, not that the others' responses haven't been good.

A
decibel is a ratio of one thing to another. It's watts to watts
in power amps and it's usually a voltage ratio for preamps.

The
dBw is a ratio of power output to 1 watt. It's done to make it
easier to calculate max. SPL since speakers are rated at 1 watt.

[DrWho]

hey cool, I didn't know they rated amps this way.

learn something new everyday [Y]

[Frzninvt]

That DBX BX1 can damn near be run into a dead short, it is capable of output even with a 0.1 ohm load. Not bad for an amplifier made in 1988 wouldn't you say. Not to mention the tremendously high damping factor giving it the ability to have superior control over the Jubilee woofer bins.