# How should I calculate the amount of power needed to achieve certain level of dB?

#### asahi.

##### Member
Pls bare with me being stupid, I'm new to this kind.

I've recently bought a pair of susvara and I'm kinda confused about whether my amp can power it enough or not.

So basically I can get the amount of wattage by multiplying the effiency of susvara and the power amp provides on that impedance, right? Is this not source-related? To elaborate, my go-to genre is classical, which needs higher volume(or gain) in general. So the amount of power needed to achieve 85dBSPL on classical music is identical to that of normal music(which has more compressed dynamic range)? Then why do I have to turn up the volume to reach that level of loudness?

Pls help me about this matter. I am currently using chord qutest(3v, rca)with smsl sp400. So it's not typical rca output voltage but definitely less than that of xlr. I'm clueless rn if my amp can handle this can(especially this amp does not make any palpable difference between each gain stage, and the measured power is different to the marketing material)

No, you can't multiply dB sensitivity by wattage, becasue it is logarithmic.

Basically for each 3dB extra SPL you need x2 power.

EG Sensitivity at 1W = 87dB
90dB needs 2W
93dB needs 4W
96dB needs 8W and so on.

But these are at 1m distance. Similarly each doubling of distance costs you 6db (4 times the power)

So at 2m 4 times the power is required.
At 4m 8x the power is required.

Probably easier to use the caluclator here:

To elaborate, my go-to genre is classical, which needs higher volume(or gain) in general. So the amount of power needed to achieve 85dBSPL on classical music is identical to that of normal music(which has more compressed dynamic range)? Then why do I have to turn up the volume to reach that level of loudness?
Because classical generally has a higher crest factor, which means that you have to turn up the volume more to get the same AVG SPL.

Pls help me about this matter. I am currently using chord qutest(3v, rca)with smsl sp400. So it's not typical rca output voltage but definitely less than that of xlr. I'm clueless rn if my amp can handle this can(especially this amp does not make any palpable difference between each gain stage, and the measured power is different to the marketing material)
WIth 3V RCA in and 1/4" TRS out, the SP400 can drive the Susvara to about 107dB SPL Peak.
With classical music, that translates to about 85dB SPL AVG, but only if your tracks are mastered to -0dBFS Peak. Any dB of headroom in the file will lose you one dB of SPL (use volume normalization)

If you use the SP400's 4pin XLR output, then it can drive the Susvara to about 113dB SPL Peak, or 90dB SPL AVG.

Because classical generally has a higher crest factor, which means that you have to turn up the volume more to get the same AVG SPL.

WIth 3V RCA in and 1/4" TRS out, the SP400 can drive the Susvara to about 107dB SPL Peak.
With classical music, that translates to about 85dB SPL AVG, but only if your tracks are mastered to -0dBFS Peak. Any dB of headroom in the file will lose you one dB of SPL (use replay gain!)

If you use the SP400's 4pin XLR output, then it can drive the Susvara to about 113dB SPL Peak, or 90dB SPL AVG.
Thanks for the detailed answer! You blew my confusion away.

No, you can't multiply dB sensitivity by wattage, becasue it is logarithmic.

Basically for each 3dB extra SPL you need x2 power.

EG Sensitivity at 1W = 87dB
90dB needs 2W
93dB needs 4W
96dB needs 8W and so on.

But these are at 1m distance. Similarly each doubling of distance costs you 6db (4 times the power)

So at 2m 4 times the power is required.
At 4m 8x the power is required.

Probably easier to use the caluclator here:
Oh yeah, I totally forgot the dB is logarithmic lol thanks a lot! I'll definitely use the calculator for my future purchases

@asahi.
In case your SP400 doesn't get loud enough, even when using the Balanced output and ensuring that your tracks are played at close to -0dBFS Peak, you may want to consider the Topping L70. It has very high gain and can play about 30% louder than the SP400 with 3V RCA in, XLR out, 60Ω Load impedance (a.k.a Susvara).

@asahi.
In case your SP400 doesn't get loud enough, even when using the Balanced output and ensuring that your tracks are played at close to -0dBFS Peak, you may want to consider the Topping L70. It has very high gain and can play about 30% louder than the SP400 with 3V RCA in, XLR out, 60Ω Load impedance (a.k.a Susvara).
Actually I'm considering the A70 pro mainly because it looks sexy and black one would go pretty well with my black qutest! But sp400 would do since I usually stay around 70dB on average. Thanks anyway. Have a good one!

I've recently bought a pair of susvara and I'm kinda confused about whether my amp can power it enough or not.
If it goes loud enough for you and it still sounds good (if you're not hearing distortion) you are good to go!

To elaborate, my go-to genre is classical, which needs higher volume (or gain) in general. So the amount of power needed to achieve 85dBSPL on classical music is identical to that of normal music(which has more compressed dynamic range)?
Yes, more dynamic music requires more (peak) power to get the same volume. So you need a "bigger amplifier", although on average you might be using less power.

Then why do I have to turn up the volume to reach that level of loudness?
The peaks don't correlate well with our perception of loudness. It's mostly related to the short-term average. Most popular music is over-compressed (IMO*) to "win" The Loudness War. With compression and limiting you can bring-up the average & loudness without clipping-distorting the peaks.

If you compare a classical radio station to a popular radio station the classical will be quieter even though they are broadcasting at the same peak level.

Most radio stations add their own compression to get constant maximum loudness. I assume classical stations use some compression/limiting, but less, and the recordings are less compressed to begin with. A limiter is required for broadcasting because it's illegal to over-modulate, but if the peaks aren't too high it won't kick-in.

All of the popular streaming services are using "loudness normalization" so you don't get much variation from song-to-song. The level is adjusted before the song starts so the musical dynamics aren't affected. But in order to do this, they have to lower the loud tracks, because there are quiet-sounding tracks that can't be boosted without clipping the peaks. They don't want everything too quiet so the target volume is a compromise. And since they won't boost the quiet tracks into clipping, some tracks, and probably most classical tracks, will still be quieter.

P.S
I'm not a classical fan but sometimes I wonder if I'm listening "louder" and using more average (and peak) power with more dynamic music... because when it sounds good I like to turn it up and listen louder! With constantly-loud crap I'm not enjoying it and I turn it down.

* Obviously, most people like it or it wouldn't sell and they wouldn't do it.

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