28-12-2020, 06:15 PM
Of course, the difference between 20 watts and 4 watts is only 7dB...
Guitar speakers are very efficient. Picking one at random, the Celestion "Eight 15" - just picked at random as the smallest (8") guitar speaker on their website - the sensitivity is quoted at 95dB. That's an incomplete spec: what they really mean is 95dB, measured at 1 metre, with a 1 watt electrical input.
Just let that sink in for a moment. Just 1 watt will produce 95dB, relative to the threshold of hearing (20µPa). That is a seriously loud noise. From just 1 watt.
For comparison, good monitor loudspeakers might be 85dB/W/m. The LS3/5A is nearer 83dB. An efficient hi-fi speaker might be closer to 90dB/W/m.
This speaker has a power rating of 20W. That's 13dBW, meaning that one of these speakers fed from a 20W amp will peak at 108dB at 1m! Even a small 4W amp will make something like 101dB. That's ignoring second-order effects like power compression, breakup, etc...
Just out of interest, I noted that their 15" guitar speaker (the "G15V-100 Fullback") is 99dB/W/m. And it has a power rating of 100W, which is 20dBW, so one of these will make 119dB at 1m.
After the drummer, my biggest challenge when doing live sound is persuading the guitarist(s) to turn down their amps. If I'm aiming to keep the whole band below around 90dBSPL, you can see the problem... Don't forget that the guitars (and most of the other instruments and vocals) have to be piped to the stage monitors so the rest of the band can hear their colleagues more clearly. A lot of the time in our small venue, the PA is virtually just carrying the vocals and kick drum! Slight exaggeration, but you get the idea... Thank goodness for power soaks and modelling amps!
If building a power soak for home practice use, I'd instinctively expect to need more than 10:1, which is only 10dB of loss. Perhaps have an option for 100:1, giving 20dB? Obviously it depends on the power output of the amp in question and the speaker sensitivity, but having shared a student house with a guitarist using a 3W valve amp (found in a skip!), I know how loud these things can be in a small room!
Guitar speakers are very efficient. Picking one at random, the Celestion "Eight 15" - just picked at random as the smallest (8") guitar speaker on their website - the sensitivity is quoted at 95dB. That's an incomplete spec: what they really mean is 95dB, measured at 1 metre, with a 1 watt electrical input.
Just let that sink in for a moment. Just 1 watt will produce 95dB, relative to the threshold of hearing (20µPa). That is a seriously loud noise. From just 1 watt.
For comparison, good monitor loudspeakers might be 85dB/W/m. The LS3/5A is nearer 83dB. An efficient hi-fi speaker might be closer to 90dB/W/m.
This speaker has a power rating of 20W. That's 13dBW, meaning that one of these speakers fed from a 20W amp will peak at 108dB at 1m! Even a small 4W amp will make something like 101dB. That's ignoring second-order effects like power compression, breakup, etc...
Just out of interest, I noted that their 15" guitar speaker (the "G15V-100 Fullback") is 99dB/W/m. And it has a power rating of 100W, which is 20dBW, so one of these will make 119dB at 1m.
After the drummer, my biggest challenge when doing live sound is persuading the guitarist(s) to turn down their amps. If I'm aiming to keep the whole band below around 90dBSPL, you can see the problem... Don't forget that the guitars (and most of the other instruments and vocals) have to be piped to the stage monitors so the rest of the band can hear their colleagues more clearly. A lot of the time in our small venue, the PA is virtually just carrying the vocals and kick drum! Slight exaggeration, but you get the idea... Thank goodness for power soaks and modelling amps!
If building a power soak for home practice use, I'd instinctively expect to need more than 10:1, which is only 10dB of loss. Perhaps have an option for 100:1, giving 20dB? Obviously it depends on the power output of the amp in question and the speaker sensitivity, but having shared a student house with a guitarist using a 3W valve amp (found in a skip!), I know how loud these things can be in a small room!
