Minimum Power Requirements for Subs?

kberg

All,

A lot of talk is posted on receiver power, but I'm curious about minimum power level "requirements" (or perhaps I should say "suggestions") for subwoofers. Is there a minumum guideline one should use in determining how powerful a subwoofer one should consider, based on their receiver power output?

Just curious as to what power level at which you really notice the "punch".

Thanks,

Kevin

Dr. Spec

The amplifier power of a subwoofer really has very little to do with its ability to generate SPL.

There are several interrelated variables at work, like driver efficiency, enclosure size, porting, and whether or not electronic equalization is being employed.

There are subwoofers with amps in the 1,000-2,000W range that are no louder than subs with 500W amps because their design is inherently inefficient and they use tons of EQ to achieve extension and this requires mondo amplifier power.

Anyway, to more directly answer your question, if you can generate CLEAN sound pressure level bass peaks of 105-107 dB - measured at the key listening positions, you will definitely be noticing the "punch". This assumes an average size HT room - maybe 1,700 ft3.

Get up into the clean 110-112 dB range at the couch, and you have an exceptionally powerful subwoofer.

Anything higher (113-117 dB) can only usually be achieved with dual subs, a properly vented and tuned DIY sub, or a single upper end commercial sub like an SVS, HSU, Velo HGS, Paradigm Servo, Klipsch RSW.

I have measured SPL bass peaks of 114 dB 11 feet from my sub during the ship explosion from the opener in SWEPII - AOTC. Move to within 6 feet of the sub, and it hits 118 dB on the same passage. My HT room is 1700 ft3.

Ron-P can hit 120 dB peaks from his newly ported Tempest DIY sub, but the Driftwood Theater is quite a bit smaller than the typical HT room and has no fixed openings to other rooms. This helps dramatically to boost SPL.

If you are going to be measuring bass SPL at the couch, use the C-weighted Fast setting on the meter and having a tripod helps too.

kberg

Originally posted by Dr. Spec

to more directly answer your question, if you can generate CLEAN sound pressure level bass peaks of 105-107 dB - measured at the key listening positions, you will definitely be noticing the "punch". This assumes an average size HT room - maybe 1,700 ft3.

Thanks! One more question - I have an SPL meter - how can I tell if I am generating "clean" sound pressure level bass at any given dB level?

Dr. Spec

Well, it's definitely a subjective term, but if the sound remains dynamic and effortless like it does at lower levels, you are still within the comfortable operating range of the sub.

Don't push your sub to the point of damage for the sake of getting max readings. I have never pushed my SVS beyond its safe limits - I probably have another 2-3 dB left in the tank and I have no desire to prove that at the risk of blowing the $300 driver.

The sounds of a sub in distress (not recommended) are pretty obvious - it will start to sound compressed and the quality and tone will change for the worse - this is harmonic distortion creeping in - usually noticeable around 10% at loud playback levels. The amplifier may start clipping also, which will introduce its own grating sound and distortion.

Push it any harder (definitely not recommended) and it will start to pop, snort, ****, or make a loud CLACK, which is the driver bottoming. Permanent damage is imminent at that point - note the SEVERAL new 404 owners who have already toasted their drivers.

kberg

Read you loud and clear (pun intended).

Thanks!

Kevin

Dr. Spec

As a favor for all that writing - tell me what you are getting in the room from your sub.

kberg

Ok, although it seems I will have to be careful in determining this (I don't want to push the sub too far and damage it), and of course I need to do this at a convenient time, like when the wife isn't around to complain about the "noise". And I KNOW I'm not the only one with this problem!

faster100

spec, I concur on the popped 404 driver, put me in for the idiot award for busting a 2-3 week old 404 subwoofer... Not again i tell ya not again,

kberg

Originally posted by Dr. Spec
As a favor for all that writing - tell me what you are getting in the room from your sub.

Hey Dr. Spec,

Ok, for my room (carpeted and of approx. 2500 ft3), I popped in LOTR EE (DTS of course) for the opening battle scence and was able to peak my Infinity sub at 105 dB w/o any form of distortion, etc., so far as I could tell. I may have been able to go higher but didn't feel comfortable taking any unnecessary risks. Anyway, I would never play it that loud. Not sure what that means in terms of decent punch power for the Infinity BU2 (rated at 30-150 Hz frequency response +/- 3dB). What do you think?

Kevin

Dr. Spec

Pretty good SPL in that size room - Infinity doesn't make crap, that's for sure. I agree - don't push it any further. Was that when the ring dropped, or the reverse sweep when Sauron disintegrated?

shiu

Dr. Spec, I didn't realize people are frying their 404 drivers. I set my 404's volume at the 10:30 position. Not that it matters, but my receiver is a Sony STR-DA4ES rated for 110W per channel. My worst souce would be DVD movies such as LOTR, Star war series type, do you think I should be fine as long as I leave the volume at 10:30 postion.

Dr. Spec

The volume setting is not an absolute. The mix of the input signal strength and the volume setting is what matters. It is possible to overdrive a sub with the volume setting at 1/4 if you have a strong enough input signal.

You need to calibrate your sub along with the rest of your system with an SPL meter and test tones. Usually blown subs are the result of running the sub too hot without realizing it.

I have no direct experience with the 404, other than it seems fragile and gives not warning before the woofer gives up the ghost.

shiu

I guess I need to buy a meter. Could you please recommend a simple calibration procedure. My source input is the sub out from my Sony receiver. I left all the EQ settings at factory default, but I set the high cut to 130 hz. Thanks,

kberg

Originally posted by Dr. Spec
Pretty good SPL in that size room - Infinity doesn't make crap, that's for sure. I agree - don't push it any further. Was that when the ring dropped, or the reverse sweep when Sauron disintegrated?

The reverse sweep - I love that part - a great test for any sub, I think. Another one of my favorite chapters was Balin's Tomb (I think that's what it's called), not so much for just the sub but for center and surrounds, especially. Oh well, enough of that - thanks!

Dr. Spec

Originally posted by kberg


The reverse sweep - I love that part - a great test for any sub, I think. Another one of my favorite chapters was Balin's Tomb (I think that's what it's called), not so much for just the sub but for center and surrounds, especially. Oh well, enough of that - thanks!

The reverse sweep extends to 50 Hz and is a piece of cake for any sub - it's very loud (110 dB in my room) but not deep.

Do you remember what you recorded when the ring dropped and what your subjective impressions were? THAT is a brutal test for a subwoofer. It should give you a 2 dB higher reading than the reverse sweep at the same volume. So you should have hit 107 on the drop if you hit 105 on the sweep.

Dr. Spec

Originally posted by shiu
I guess I need to buy a meter. Could you please recommend a simple calibration procedure. My source input is the sub out from my Sony receiver. I left all the EQ settings at factory default, but I set the high cut to 130 hz. Thanks,

Buy the RS analog meter for $35. Order it if they are out of stock.

Buy the Video Essentials, AVIA, or Sound & Vision calibration DVD, follow the directions, and go to town.

The RS meter reads progressively lower as the bass drops deeper, but for the sub calibration tone it only reads about 2 dB low.

kberg

Originally posted by Dr. Spec


The reverse sweep extends to 50 Hz and is a piece of cake for any sub - it's very loud (110 dB in my room) but not deep.

Do you remember what you recorded when the ring dropped and what your subjective impressions were? THAT is a brutal test for a subwoofer. It should give you a 2 dB higher reading than the reverse sweep at the same volume. So you should have hit 107 on the drop if you hit 105 on the sweep.

Great - that even better news.

Dr. Spec

Originally posted by kberg


Great - that even better news.

???? Not sure what you mean here. I was looking for your subjective and objective observations on the ring drop after it gets cut off Sauron's hand in the opening scene.

Dr. Spec

The original theatrical version in DD is easily mastered the hottest on the LFE track - wow.

While the entire DVD is loaded with deep bass, the huge deep bass hits are the ring drop, the wraiths first leaving the castle on horseback, the cave troll first entering and then falling dead, and the fire demon approaching when the rocks on the mountain walls are shifting and falling.

kberg

Originally posted by Dr. Spec
The original theatrical version in DD is easily mastered the hottest on the LFE track - wow.

Didn't quite get what you said above - are you saying that the original DD version is mastered hotter than the EE DTS version?

Dr. Spec

Way hotter - about 4 dB louder at the same master volume level. Many thought it was overcooked.

shiu

Just notice in my previous question, I forgot to mention that I left my Sony receiver volume control at -37 to -43 dB (404 volume at 10:30 position) when playing DVD movies. I would never go above -30 dB. Given that, I hope you would tell me (by your experience) my 404 is safe. May be I am overly concern, I have never owned a subwoofer, until last December. Is the RS sound level meter available at Radio Shack. I am in Ontario, not far from Toronto. Where can I buy the Sound & Vision calibration DVD?

Dr. Spec

If you have an average sized HT room and you are playing at moderate levels, you should be fine, even if you are calibrated on the warm side.

Polk doesn't make junk subs - all their stuff is decent quality. Many 404 owners report room shaking SPL and I don't doubt it - it's a pretty beefy unit.

I think those that fried their 404's were probably pushing it very hard - upwards of 105-108 dB peaks at the seat.

If you are in the 103 dB and under range for bass peaks at the couch in an average size room, you should be A-OK.

shiu

Thank you Dr., I feel better now. My HT room is only 11 X 18 X 8. I am still going to get the meter and DVD and do the calibration anyway.

goingganzo

another bad sound is a cherping sound. like a little bird. i have a car sub that i drove with a 1000 wat rms amp and it was olny rated at 200 wats rms you got the distorshon that dr said then when you go past that it starts to cherp. i figure with my modleing i will get around 123db+ with my new soon to get drivers super sub. that is at 1 meter and my first couch is at 1 meter.

Dr. Spec

Oh **** you'll be doing better than that Gonzo. I'm hitting 119 at 1 meter and I'm only using a single 12" TC Sounds driver. If your room is not huge, you'll be hitting near 130 at one meter.

kberg

Originally posted by Dr. Spec


???? Not sure what you mean here. I was looking for your subjective and objective observations on the ring drop after it gets cut off Sauron's hand in the opening scene.

I hit 105 db on the sweep at about 3 meters, so I just figured if I could hit 107 dB on the ring drop (without distortion) that would be even better. However, when I get a chance (i.e., when the wife is out of the house), I'll also meter the ring drop scene on the DD original release and let you know.

Dr. Spec

Edit: Kevin, you don't have to crank it to evaluate the ring drop scene. You are looking at this point to record only the difference between it and the reverse sweep. You can always do that at a lower volume.

If you are switching to the theatrical DD version, make sure to record both the sweep and the ring drop at the same master volume level for a valid comparison.

On the DD theatrical version, the ring drop is 3 dB louder than the peak volume on the Sauron reverse sweep disintegration scene.

If your ring drop is the same or lower volume than the reverse sweep, it's a very good indicator your sub is checking out early.

That ring drop extends well into the SS region with good amplitude. Hearing it ALL for the first time was a real eye opener for me. The SS room decay lasts about a 1/2 second after the ring hits the ground. It's really impressive.

If you do decide to crank-it, be careful on the DD version - it's very hot. There were many a wrecked subs reported over at HTF when this DVD first came out in August of 2002.

kberg

Originally posted by Dr. Spec

If you are switching to the theatrical DD version, make sure to record both the sweep and the ring drop at the same master volume level for a valid comparison.

On the DD theatrical version, the ring drop is 3 dB louder than the peak volume on the Sauron reverse sweep disintegration scene.

If your ring drop is the same or lower volume than the reverse sweep, it's a very good indicator your sub is checking out early.

Hey Doc,

I finally got around to testing and here are the differences in results (weighting C/slow response on the SPL meter) at the same volume level:

DD Version - Ring Drop (98 dB)/Reverse Sweep (110 dB)
DTS Version - Ring Drop (96 dB)/Reverse Sweep (106 dB)

So yeah, it appears that although the sub sounds great, it is "checking out (quite a bit) early", so I can only imagine what it would sound like if it wasn't.

Looks like I may have to save up for an SVS.

Dr. Spec

Kevin:

I just re-ran that scene and matched my volume to yours on the reverse sweep with the DD Theatrical version with the SPL meter in three different spots and set on C-weighted Fast and got the following readings:

Location #1:

Ring Drop - 109 dB
Reverse Sweep - 110 dB

Location #2:

Ring Drop - 110 dB
Reverse Sweep - 110 dB

Location #3:

Ring Drop - 111 dB
Reverse Sweep - 110 dB

Clearly, the SPL readings are location dependent, but maybe a more conservative statement would be the amplitude is about the same for each scene. I was not able to duplicate a 3 dB advantage for the ring drop, and my furniture arrangement has changed since, and that is probably the culprit.

I agree - you are anywhere from 10-12 dB down on the Ring Drop. Clearly, the sub is ignoring the vast majority of it.

Yes - get your "save" on. The beauty of a great sub will not necessarily be its ability to play louder than what you already own. Rather, it will be its ability to play just as loud at 20 Hz as it does at 40 Hz.

At the same reverse sweep volume, my sub is up a staggering 11-13 dB over your Infinity with the ring drop. This is not meant as a dis against the Infinity, but as an objective comparison. Remember, a 10 dB increase in volume is perceived to be TWICE as loud. The difference between the two subs in your own room - as you can well imagine - would be pretty remarkable.

Doc

goingganzo

do you know the fr of each sene? aka the ring is that a more of sub sonic. also is these volumes for testing or do you normaly get bass this loud?