Input needed on 240 vs. 120v situation

AandPDan

OK, so it usually is drawing 100 watts, that's what you said. A 20 amp (120v) circuit can supply up to 2400 watts without tripping the breaker. It can even handle much higher loads - for say a motor starting - without tripping a breaker for a period of time.

The amplifier is rated in Watts RMS, it's a sine wave. The power output is constantly changing.

Plug the thing in and see what happens.

BigCoolJesus

Using a speaker as an example:

A speaker with sensitivity rating of 93dB takes 1w of power to produce 93dB at 1m away. When listening at a calibrated volume of 75dB during movie playback, peaks of 105dB are normal. This means at 1m away, one would need 16w to watch a movie at the normal 75dB level otherwise clipping/compression of the sound ensues. For each meter of distance wattage must be doubled (and that's being generous by including liberal room gain), so at 2m 32w would be needed, at 3m 64w, at 4m 128w, and at 5m (my average distance in the new room) 256w are needed for each speaker to ensure peaks are not compressed and the audio can play cleanly.

That is for speakers, which are typically rated well above 100Hz during these tests (usually 1kHz). The lower the hertz, the more power is required which is why the recommended crossover settings for speakers is 80Hz (because it takes enormous amounts of power to produce low end bass, which a typical receiver and even mid-level stand alone amplifiers are not capable of handling).

Now LFE tracks of movies carry peaks that are 10dB higher than the 105dB peaks of speakers, meaning that when listening at 75dB, bass peaks from the subwoofer can reach as high as 115dB.....and this is at very low frequencies. The subwoofer I have (Paradigm Sub 25) is rated to play as low as 9Hz. If you honestly think 100w "Typical" is enough to reproduce sub-20Hz notes at said 115dB peaks, you are sorely mistaken.

You must also remember that a 75dB calibrated level is typical for home theater rooms that are setup properly. So your embellishment that needing such power just to "annoy neighbors and acquire an eviction notice" is far from the truth. Maybe you have never had the chance to watch Transformers Dark of the Moon on a properly setup and calibrated system? Because I can guarantee you that 100w of power will get you nothing from that movie. Of course, if you think otherwise feel free to stop by the AVS Forums and ask for yourself.

Not trying to be an a**, just correcting your wrong assumptions.

k_buz

What does the cord end look like for the AC?

What is the FLA of the AC?

What size wire goes to the AC outlet?

BigCoolJesus

That's what the back of the subwoofer says.....but the word typical has infinite meaning behind it. What Paradigm views as typical may be someone listening to a music CD at 55dB (-20 on the master volume knob), which is not very loud at all. Watching Transformers Dark of the Moon or Tron Legacy at the accepted and standard calibrated volume of 75dB is by no means typical. At all.

I currently have the subwoofer hooked up in a smaller room to 120v/15amp circuit and it does just fine accept that the lights dim during said movies above. And this is in an 11x11x8ft room. Moving into a 19x14x8ft room is a significant increase in size, which requires more power to reach the same calibrated levels (more air to move/pressurize).

BigCoolJesus

I will be posting pictures of the breaker box, along with AC cord and AC power label in a few hours.

Thanks

k_buz

Post pictures of the air conditioner outlet and cord end.

Just making sure we are talking about the air conditioner and not the AC power cord for the sub.

BigCoolJesus

Correct.

Also, I just got off the phone with a family friend who is an electrician and he said he would advise running a dedicated 240/15amp by piggy backing enough of my current 120/20amp breakers together to free up two spots for a 2-pole 240v breaker.

Attached are pictures of my breaker box.

Attached Thumbnails

   

M3 Pete

Huh? Other than the obvious things I added, it's an exact quote from your owner's manual. Maybe I should have added one of these?

But seriously, how often have you cranked that thing up ALL THE WAY?

I have a decent sub at home (an Outlaw with only about 1/10th of the watts that yours has), and when calibrated with the receiver's Audyssey system, the gain knob on the sub itself is never more than halfway with any room I've used it in. Even if I played it a bit "hot" I probably would not go past 3/4. In other words, the sub is mostly just loafing along, even when I crank the receiver.

I really can't imagine how loud yours must be when pushing the full 3000 watts. Maybe your pool room is a giant cavern that needs all 3000 watts to fill it, but I'm guessing it does not.

FYI, I've been a member of AVSforum.com since 2004, and know a thing or two about HT subs, calibrated systems, etc.

Anyway, I've digressed into a p!ssing contest, so I apologize for going off topic.

I'm guessing that a dedicated 120V 20A outlet would probably be sufficient to fully power your sub without starving it. Even with all the discussions I've seen about high-powered receivers and subs, I've never seen discussions where people needed to use 240V to power them.

You say the sub has worked just fine, except for lights dimming. What you don't know is how many outlets that circuit was feeding. Use a dedicated circuit for your sub and you "should" have no more dimming, unless your feed from the power company is not adequate.

But hey, if you have a relative who wants to wire up a 240V receptacle, why not?

Report back with the results.

Cheers!

BigCoolJesus

No worries......I apologize for assuming too much.

I am unfortunately much like my father in that I like to do everything "overkill" to make sure I never have to re-do or tweak again. So when the subwoofer says that for "maximum continuous performance 240v is recommended" I can't help but rest until I get it the power it wants, even if it may only use it but a few times (Tron and Transformers are obvious candidates, plus Master and Commander and War of the Worlds).

The other problem is that each 120v/20amp breaker has something something else running off it so that I can't completely isolate one outlet for the subwoofer unless I run a dedicated one. I suppose since this is finally going to be my be all end all home theater room I want to do it right and be done with it

Missouri Bound

Mfg and model number of the sub....that's all we need.

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k_buz

Data Sheet

Owner's Manual

M3 Pete

I'm surprised the electricians have not mentioned this, but your breaker panel appears to be full. I think I remember that you are always supposed to have two empty slots (for what reason I don't know).

But maybe I got that wrong, so one of the pros should chime in here.

You know, since you have that big room now, one of these would solve all your problems. Only need 1000 watt amp, and if it ain't loud enough, you are simply deaf (or will be soon!)
http://www.danleysoundlabs.com/pdf/D...ec%20sheet.pdf

k_buz

That's really only true/enforced when you install/replace a panel.

I'm trying to stay out of this one...there are more than enough people that can advise him on this.

If it were me? I'd slap on that 15 A 120V cord and plug it in.

M3 Pete

THat makes sense, if it's new, you want to be able to add later, so you need the empty slots.

I think that's probably all that's needed, but audiophiles are prone to overkill. Nowhere else will people spend $1K - $2K (or more!) on a one-meter cable to connect two audio components, and then gush about how much better it sounds. Obviously it's worth it to them.

I'm more a bang-for-buck kind of guy. I have nice setup, but I hardly get to use it because I have two little kids who go to bed early and I'm not home enough.

mpoulton

Install a 20A/20A quad breaker in place of two of the 20A single pole breakers. Use the double pole portion of the quad for a dedicated 240V 20A recept for the subwoofer, and place the original 20A circuits on the separate 20A poles of the new quad breaker.