Are subs power suckers?

[juanedilio]

I just bought a subwoofer from av123 (the x-sub). I currently live with my aunt and cousin. Well a friend of them told my aunt that a subwoofer must be on at all times and that it consumes a ridiculous amount of power. Right now I am getting a lot of BS and discussions about me setting up the subwoofer by them and it is stressing me out.

Is there some truth to both of these statements? What factual data can I present them to calm them down? Any help would be appreciated, thanks!

 

[Sheep]

A sub sitting, not playing, won't draw much power. When it operates, it can draw large amounts (not the X-Sub, it's too small) in peaks (a loud passage).

Some subs can peak in the 1000 watt range and up. You're fine though.

SheepStar

 

[Tod]

Yeah, most always-on amps and other components tend to draw a watt or two continuously just because. A smaller sub hitting a peak would still only be like turning a couple light bulbs on for a bit. Give them $2/month (which is generous) and tell them to go away.

 

[TLS Guy]

Useless manual

As is so often the case the manual for your sub, which I downloaded, is woefully inadequate.

All I could gather is that the subwoofer amp delivers 150 watts RMS maximum output. It does not say what type of amp is in the sub. Many subs use class G switching amps and some, digital amps. These are highly efficient amps and almost all the power goes to the speaker. In traditional class B biased transistor amplifiers, the quiescent current and efficiency are dependent on the biasing of the power transistors.

Also a lot of subs switch themselves off when not in use, and come alive when a signal is presented to the input.

The manual of this sub is silent on the issue of the idling power consumption, peak current and quiescent current. This is a very cheap unit, and I suspect the manufacturer does not want you to know how deficient this device is in these parameters.

Since this device is so cheap, I'm going to assume it is bare bones, and that it has a traditional class B 150 watt amplifier, and that it does not switch off after a period of no signal at the input. Typical specifications for that type of amplifier would be a quiescent current of about 25 to 30 watts and a fully driven power consumption of 300 to 350 watts.

Now this is an educated guess. The manufacturer should be able to give you exact numbers for the parameters I have estimated.

 

[mike c]

and that's when running ... on standby mode, it'd be around 2-8 watts.

an email from av123 would be great proof to show your aunt and that dip$hit friend.

 

[Tod]

I was just reading the manual for the Martin Logan Descent I might be considering, and they mentioned that on but inactive the sub draws 13 watts. At 10 cents/kilowatt hour, that would be...94 cents for a month. I don't know what your power costs are wherever you live, but still it will be pennies. Even if you ran it at high levels all month long it would still be a few dollars. Which means...


You need more power!

 

[juanedilio]

Hey thanks a lot. I will be emailing AV123 to get those exact stand-by numbers. That friend of her really did it for me.

And by the way in the manual of the X-sub it says that it has:

signal sensing auto ON/standby Mode

I suppose that means it has that feature that turns On only when it detects a signal.

 

[juanedilio]

One other thing I stumbled on reading the manual of which I am not sure.

When explaining how to connect the subwoofer it mentions three options, one of them being using the dedicated LFE input. Then going to the receiver (a Yamaha RX-V659 I just bought) I ask: in the back of the receiver there is a section called "Pre-out" which has RCA outputs for left, right, center, surrounds, and subwoofer. Is the output labelled subwoofer in this section what I should connect to the LFE input in the subwoofer?

This is my first time I have had to build a home theater outside of the HTIB world, reason why these probably basic questions are arising. Hopefully I wont regret all the extra money that has went in so far.

 

[TLS Guy]

Pre out

Yes, connect the subwoofer pre out to the Subwoofer LFE input.

I missed the stand by mode switching. When not in use it will consume about two watts. The running power consumption will depend the efficiency of the amp and how loud you play it. However, I bet average power consumption when in use will not exceed 50 watts.

 

[mike c]

When explaining how to connect the subwoofer it mentions three options, one of them being using the dedicated LFE input. Then going to the receiver (a Yamaha RX-V659 I just bought) I ask: in the back of the receiver there is a section called "Pre-out" which has RCA outputs for left, right, center, surrounds, and subwoofer. Is the output labelled subwoofer in this section what I should connect to the LFE input in the subwoofer?

yes, that's it.

 

[mtrycrafts]

Hey thanks a lot. I will be emailing AV123 to get those exact stand-by numbers. That friend of her really did it for me.

And by the way in the manual of the X-sub it says that it has:

signal sensing auto ON/standby Mode

I suppose that means it has that feature that turns On only when it detects a signal.

If that sub has an on/off switch, you can certainly turn it off when not in use and should be. So, it doesn't need to be on all the time, tell your aunt and as was indicated, it doesn't consume much in standby mode. Whoever talked to them are just not informed.