measuring subwoofer SPL

OK, I set all of my speakers at ref level,75db, but I hear people say that they got much higher spl out of their sub. If I have an spl meter and a cd with 15-80hz sinwave how do I go about getting the spl readings that I hear about. I see people say that the meter is 1m away from the sub but I don't have a laptop with anything like rew so is there a way to do it with just the meter? I tried just setting it up at the listening position and setting my avr at 0db for reference and it almost blew up my sub, what am I doing wrong?

First of all, be careful about running tones at very high volume for very long. It's a sure way to fry your voice coil!!!!

Most of what people report is found in movie tracks or music regarding LFE sound pressure levels.

You will often hear of Reference Level, which is 85 dB with 105 dB peaks (115 dB for bass). BUT you need a sub that is capable of handling that kind of out put. Reference level is quite loud and most people don't listen at that volume.

What kind of sub do you have?

I have two subs both that I built myself, one is a 130v.2 Elemental desiegn in a 2cf sealed enclosure and the other is a Shiva x in a 4cf sealed enclosure. I have them stacked and they sound great. I did try a test with the cd of sinewaves and with my reciever set at ref it almost blew them up. The meter got to 120db and the sub started to make mechanical noise so I stoped right away, plus the wife was saying her dishes were all going to break. here is a pic of the subs.....http://i184.photobucket.com/albums/x164/tcarcio/100_0208.jpg

tcarcio said:

I have two subs both that I built myself, one is a 130v.2 Elemental desiegn in a 2cf sealed enclosure and the other is a Shiva x in a 4cf sealed enclosure. I have them stacked and they sound great. I did try a test with the cd of sinewaves and with my reciever set at ref it almost blew them up. The meter got to 120db and the sub started to make mechanical noise so I stoped right away, plus the wife was saying her dishes were all going to break. here is a pic of the subs.....http://i184.photobucket.com/albums/x164/tcarcio/100_0208.jpg

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Nice subs. Whew I hope there's no damage. Those sine waves may be recorded pretty hot;definitely be careful. Sounds like you averted disaster.

croseiv said:

Nice subs. Whew I hope there's no damage. Those sine waves may be recorded pretty hot;definitely be careful. Sounds like you averted disaster.

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Well they seem fine so I don't think any damage was done, thanks for your input...........

120 dB is super! Was that at 1m?

croseiv said:

120 dB is super! Was that at 1m?

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No actually that was about 5 feet from the subs at the listening position and at the time I believe it was a 40-50hz tone, I don't remember which.

tcarcio said:

No actually that was about 5 feet from the subs at the listening position and at the time I believe it was a 40-50hz tone, I don't remember which.

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"C" weighted and set to "fast"?

Actually c weighted and set to slow. That is how I thought it should be set. I always set it to slow to set my levels.

tcarcio said:

Actually c weighted and set to slow. That is how I thought it should be set. I always set it to slow to set my levels.

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Me, too (C-weighted and slow). Just did it last night.

I set my system, which runs its volume settings from -20 to +20 dB, to 80 dB at the 0 dB setting on the volume guide. (I set my sub to 83.5 dB--that's 3.5 dB hot--BTW.)

Chris

Me too

I just did a calibration with a Radio Shack SPL meter. Speakers all sound fine but the subwoofer needed to be increased to +12db for 75db reading. The problem is that now the sub sounds too loud especially with music. I have to bring it down to +6 to make it sound close to bearable.

Is that normal or am I doing something wrong? I have Athena .5 speakers with an Athena P300 sub driven by Onkyo 600 receiver.

An SPL meter on it's own is too vague of an instrument to really know what is going on in room, therefore a reading of 75dB that produces too much bass. But I doubt you're doing anything wrong, and if it sounds fine, why fret?

One thing to keep in mind is that the SPL meter's reading is about 3 dB low (a correction factor must be added) for the subwoofer frequencies below 50 Hz. So if you are setting the sub 3-4 dB hot by the meter, you are actually more like 6-7 dB hot.

croseiv said:

One thing to keep in mind is that the SPL meter's reading is about 3 dB low (a correction factor must be added) for the subwoofer frequencies below 50 Hz. So if you are setting the sub 3-4 dB hot by the meter, you are actually more like 6-7 dB hot.

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Thanks for the reminder. I thought, though, that that was a sliding scale, and the nonlinearity increased as the frequencies decreased. For example, maybe it'd be off by .5-1 dB at 60 Hz, and 3ish dB in the low 20s. (These figures ore off the top of my head, but I hope they're close.)

I don't know what freq my AVR uses for its sub test tone. (I'll try to figure it out this week.) It didn't sound too deep, though.

Somewhere I have a Rives test CD that I won in an Audioholics giveaway. We changed some living room furniture since then, and I can't put my hands on it. (Hmm...just had a thought where it might be.) IIRC, that disc has a complete set of low test tones designed to work specifically with the Radio Shack meter. If I find the disc, I'll repeat the calibration using tones/SPLs designed for the RS meter.

Speaking about low freqs in general, one thing I learned from this site is that low freqs of a certain SPL are not heard to be as loud by most people as mid-freq sounds or high-freq sounds (assuming we stay under about 14,000 Hz) of the same SPL. So running a sub 3-5 dB hot gives the impression of having uniform SPL throughout the normal hearing range. Does this sound correct to all of you?

Chris

~1.5 dB at 50 Hz. Add 7.5 dB at 20 Hz. So if your meter is reading 75 dB running a 20 Hz tone your sub is really outputting 82.5 dB. If this compenstation isn't taken into account, well you can see how one could easily push their sub too far. Also, the lower frequencies require more power, so the overloading can snowball.

If this isn't taken into consideration and you are trying to boost the low frequencies, overtaxing your sub can happen in short order.

croseiv said:

~1.5 dB at 50 Hz. Add 7.5 dB at 20 Hz. So if your meter is reading 75 dB running a 20 Hz tone your sub is really outputting 82.5 dB.

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Good, I wasn't too far off at the top of the subwoofer range. (I have my speakers crossed at 80 Hz.)

But a 7.5 dB difference at 20 Hz? Wow, that's a lot. I'll have to find my Rives disc and recalibrate the sub.

croseiv said:

If this compenstation isn't taken into account, well you can see how one could easily push their sub too far. Also, the lower frequencies require more power, so the overloading can snowball.

If this isn't taken into consideration and you are trying to boost the low frequencies, overtaxing your sub can happen in short order.

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Yup. I think my sub has enough guts to take it, though--after all, it's been fine so far with everything I've thrown at it, including pipe organ music where I cranked up the sub even a little extra. But I'll find my full test disc and run the whole thing.

Thx,
Chris

Wow, I didn't realize the meter was that far off, 7.5 is quite a difference. I will recal myself after seeing the error.

Perfect

7.5 db off sounds about right. As I said, after calibrating, I had to set it down 6db from the 75db value I got (+12) and that sounded good to my ears (if a little heavy). I will bring it down 1 or 2 db more and I will be all set.

On a side note, I had my speakers set to small because that is what the manual and everyone on various forums says but just now I switched them to large and I am loving it. The speakers are Athena S.5 with C.5 center (and P300 sub). Crossover set to 80 Hz in receiver and 120 Hz (defeated) on the sub.

Listening to music, the sub seems like the weakest link in my system. I am just not sure if the Dayton ($130 shipped) would be an upgrade over the Athena P300 or if I should plan on spending more.

Why not build your own. I did as a matter of fact I built two and not only did I save money I got a great sub. It's not that hard to build a sealed enclosure and the two I have sound fantastic for music and movies.