Sub only draws 5 watts?

[Destination: Moon]

Hanging around ASR the past few weeks I know there are a lot of people here that understand electronics far better than I do. I'm wondering why the watt meter I plugged my new SVS pro 1000 into only shows 5.1 watts when it's running? Volume isn't deafening but loud enough to my ears.
The wattage draw doesn't seem to fluctuate much. It doesn't spike at power on.

FWIW, I plugged it into the watt meter because it isn't all that clear what the standby settings mean. I wanted the sub to automatically go into standby when not in use. Which it does - drawing 0.3 watts.

 

[Usernome]

You're probably just not listening very loudly, so you aren't using much power.

 

[Destination: Moon]

You're probably just not listening very loudly, so you aren't using much power.

I can't imagine how loud it would be at 150 watts - 50 percent of max constant rating!?

 

[Chrispy]

Does SVS indicate a sensitivity spec? Like other speakers, you can calculate spl, there are online calculators to help out. I've used sub drivers with 93dB sensitivity. But at low volume they, like speakers, don't use a whole lot....

 

[wwenze]

Easy to connect the dots mathematically... sensitivity @ 1w (or 2.83V) is what the words mean, 80dB @ 1W = 80dB @ 1W, so that's your starting point for calculation. Nobody knows how sensitive active speakers are, so I'm just going to say 80dB which is a very low estimate.

Every 10 times increase in power gives you +10dB exactly. 2 times is +3dB, approximately.

Since most people don't go over 80dB when listening the power they use is very little compared to 1W. However if we think about it in reverse, if you want more power e.g. you have a big hall to fill then to increase each 10dB you need 10 times the power so it adds up quickly and hence the need for high power systems.

Even that 5.1W is not the acoustical power, but rather mostly the power the system draws while it is powered up and doing nothing. You can test it yourself: System powered on while playing nothing vs powered on and playing a test tone. The difference is what's used to generate the sound. It's good data to have too, to know how much power you need and how loud you listen to (give or take 20dB), so you can make more informed decisions next time.

 

[Destination: Moon]

Easy to connect the dots mathematically... sensitivity @ 1w (or 2.83V) is what the words mean, 80dB @ 1W = 80dB @ 1W, so that's your starting point for calculation. Nobody knows how sensitive active speakers are, so I'm just going to say 80dB which is a very low estimate.

Every 10 times increase in power gives you +10dB exactly. 2 times is +3dB, approximately.

Since most people don't go over 80dB when listening the power they use is very little compared to 1W. However if we think about it in reverse, if you want more power e.g. you have a big hall to fill then to increase each 10dB you need 10 times the power so it adds up quickly and hence the need for high power systems.

Even that 5.1W is not the acoustical power, but rather mostly the power the system draws while it is powered up and doing nothing. You can test it yourself: System powered on while playing nothing vs powered on and playing a test tone. The difference is what's used to generate the sound. It's good data to have too, to know how much power you need and how loud you listen to (give or take 20dB), so you can make more informed decisions next time.

Agreed. I bought a cheap calibrated mic thinking of would be more accurate than just using an spl app on my phone, but it's not that simple I guess. I'm estimating I'm listening at 70 to 80 db max. My amp draws 80 watts at these levels. I think it's a class A.

The sub is rock steady and doesn't seem to vary over my listening range of 60 to 80db (guessing).

 

[jonfitch]

Not much of a surprise. Most people during casual listening aren't listening at a very high noise level. 99% of the time when I listen to music I'm under 1 watt of power usage. So it's indistinguishable from idle power consumption of my receiver.

 

[Destination: Moon]

Wattmeter? Averaging?

It's not averaging but I can't vouch for it's reaction time. It's a 15 dollar device, nothing fancy

 

[napilopez]

Agreed. I bought a cheap calibrated mic thinking of would be more accurate than just using an spl app on my phone, but it's not that simple I guess. I'm estimating I'm listening at 70 to 80 db max. My amp draws 80 watts at these levels. I think it's a class A.

The sub is rock steady and doesn't seem to vary over my listening range of 60 to 80db (guessing).

Which cheap calibrated microphone? Also keep in mind the stated SPL level can vary rather significantly depending on which weighting you use

 

[Destination: Moon]

Which cheap calibrated microphone? Also keep in mind the stated SPL level can vary rather significantly depending on which weighting you use

This one:
https://www.parts-express.com/Dayton-Audio-iMM-6-iDevice-Calibrated-Microphone-390-810

The only way I've figured to give it a baseline, is to use an offset of minus 20 - to get it reading about 28db
In a perfectly quiet room. I'm not sure that's exactly right, but it's about the only thing I could think of. It's much more sensitive than the mic in my phone. I paid for an app that'll let me load the factory calibration curve that supposedly belongs to my mic. Using c weighting but open to any suggestions!

 

[sigbergaudio]

You need to play pretty loud before your power requirements exceed 5w. A bit complicated with subwoofers due to varying impedance with frequency etc, but still. Whenever I see a subwoofer with like 2000W I go what on earth. But then if it needs 500W to reach 110dB, it will need 1000W to reach 113dB, and then 2000W to reach 116dB. The decibel scale is a bit wonky before you get used to it.

https://www.musiciansfriend.com/thehub/understanding-wattage-speaker-efficiency-amplifier-loudness

 

[abdo123]

I can't imagine how loud it would be at 150 watts - 50 percent of max constant rating!?

That would be ~12 dB louder. Not very hard to imagine.

 

[Mnyb]

Imagine that the meter is not fast enough , but the power supply will average too if it has any kind of of decent energy storage so peak power is probably much more , the crest factor of music is a bit funny peaky with almost low res level a bit different from sine waves .

Yes I think the power supply smooths the peaks on the ac input ?

The dB vs power can get even wonkier with subs as many are eq’ed and in other was compensated via feedback or servo etc so reaching a peak at very low frequency can demands gobs of power there you have your 2000w

Music don’t usually have it’s highest levels in the sub bass so your sub may not need much power at 40-80hz but do need it at 15-30 Hz play a modern sci-fi movie with you wall vibrating and you see more power .