How loud is 80dB??

[surrey lad]

Hi guys..

I spent some time on Saturday setting up REW/BFD and my servo-15 sub (not quite there yet!) and I'm quite surprised at how low, let's say 60Hz sounds when set to 80dB reading off my spl meter.

When running the frequency sweeps I was half expecting to shack and rattle the room annoying the neighbours and wife but instead all I hear is a very subtle sweeping sound.

Is this right

BTW great forums guys. I haven't posted many but read loads!!

[Danny]

I think this is normal, my mower puts out 75Db (by the label on it), if you really want to shake your room turn it up to around 110-120Db. Maybe some of the other guys can tell you more. welcome to the shack

[Chrisbee]

With respect Danny, if you turn a sub up to between 110-120dB you can probably say bye-bye to your sub.

Subs are very few and far between which can tolerate such levels even for the brief period of a test sweep. 120dB @ 10Hz (at the start of the REW sweep) is probably beyond the ability of almost all commercial subs available anywhere.

[surrey lad]

Hi guys,

Thanks for the quick replies. You have a point about your mower. I was cutting the grass with my new petrol mower yesterday (also displaying a 75dB warning label) , I took off my ear defenders to find that, 75db from a mower is pretty tame and bordering not requiring ear protection.

At one stage I did think that maybe the spl meter was faulty, so I used the auto setup procedure with mic that comes as standard on my EAD processor to self generate its own pink noise and allow it to set it's self to 75dB. Checked the RS meter and yes it read 75db, but strangely enough pink noise at 75 is loud.

Maybe I've answered my own question by comparing the calibration of the EAD with the RS meter, it just seemed surprisingly quiet to me.

[josh]

hey Surreylad

Is that Surrey B.C.?

Believe me, the servo 15 will play any frequency to levels that will literally shake you walls and windows and with its built in overload protection, you don't have to worry about hurting it, I've had mine for 9 years and its well used, only shut down on me once and upon inspection, i found a towel had fallen down over the heatsinks, so it overheated, waited 10 minutes, removed towel and off it went.

The only sub I've ever tried that even came close was the Velodyne 18", but the servo 15 had a more pleasing sub 20 hz rumble to my ears.

The Velodyne is rated to 10 hz and the servo is rated at 115 db to 14 hz, but the Velodyne put out substantially less volume on my meter with a warble tone of 15 hz than the servo 15

The servo 15 rocks

[neophyte]

josh, maybe you hear harmonics of 15hz and than you thing its louder than velodyne

[surrey lad]

josh wrote:

hey Surreylad

Is that Surrey B.C.?


The servo 15 rocks

Hi josh, its actually Surrey, UK, way way over the other side of the pond! i've just added the googlearth feature.

Over here the servo 15 has a bit of a cult following. I can't ever see myself having to upgrade unless something goes horribly wrong.

I used to drive a pair of REL Stratas, I couldn't believe the difference when I changed to the servo, within a minute of testing I had a BIG grin on my face,WOW.

Have you set up your servo using REW?

[Chrisbee]

josh wrote:

The only sub I've ever tried that even came close was the Velodyne 18", but the servo 15 had a more pleasing sub 20 hz rumble to my ears.

The Velodyne is rated to 10 hz and the servo is rated at 115 db to 14 hz, but the Velodyne put out substantially less volume on my meter with a warble tone of 15 hz than the servo 15

The servo 15 rocks

It is interesting that you claim to have actually heard frequencies below 20Hz. The RS meter can't differentiate harmonic distortion from fundamentals. It measures the first far more readily than the latter and does so by a very large margin.

Anything much below 25Hz on a low distortion subwoofer is the softest of animal purrs to my ears without any audible clues as to tonal quality or timbre. (No matter what the level)

To describe it as a "rumble" is certainly not the term I would use. I believe you are actually hearing the harmonic distortion components of the fundamental or local sympathetic vibrations.

These very low frequencies tend to modulate higher tones giving them a sort of tremolo or vibrato effect. While the fundamental remains completely inaudible to human hearing. The same can't be said for whales and elephants.

[MACCA350]

I've played around with some sinewaves on my DD15, and I found exactly what Chrisbee said.

10Hz was completely inaudible but had a few windows were rattling.
15Hz I could feel pressure in my ears but no sound, except that the entire room including the substructure of the house was vibrating

cheers

[surrey lad]

MACCA350 wrote:

I've played around with some sinewaves on my DD15, and I found exactly what Chrisbee said.

10Hz was completely inaudible but had a few windows were rattling.
15Hz I could feel pressure in my ears but no sound, except that the entire room including the substructure of the house was vibrating

cheers

What sort of dB levels was you playing at??

[MACCA350]

What sort of dB levels was you playing at??

At the time I didn't check with the SPL meter, but I might do it again on the weekend and see what the SPL meter shows.

cheers

[Chrisbee]

MACCA350 wrote:

At the time I didn't check with the SPL meter, but I might do it again on the weekend and see what the SPL meter shows.

cheers

Remember that with such VLFs the RS meter is very insensitive so you should be adding roughly 25dB to your meter readings.

[Josuah]

Also remember that pushing the volume higher on the DD subs for low frequencies won't increase the volume because it doesn't want to introduce distortion. The REW calibration file will add the right amount of dB, right?

IIRC, I can hit after adjustment 105dB@12Hz and 110dB@20Hz at my seat. My subs are about 11 feet away. There's no doubt distortion at those levels, but they seem to be not as much of a contamination as the house's complaining.

[MACCA350]

OK, I played around with the sinewaves again, this time with my SPL meter. I set it to C weighting and recorded the average reading not peak at my listening position. Set the sub to 30% volume and increased the volume on the receiver up to about -10 while the sinewave was playing.

10Hz --- 88db
15Hz --- 100db
16Hz --- 106db

I have no idea what the correction values are or how that effects these readings, but those tones really get the whole house shaking, I don't want to put the neighbors through an 20Hz tone, because last time I did I nearly $hit myself When I first bought the sub I had it at 25% volume and during movies the SPL meter read around 120-123db in loud scenes, no-wonder the neighbors complained

cheers

[surrey lad]

Last night I finally had everything hooked up and working.

WOW my servo-15 is good!!!

10Hz --- 89db
15Hz --- 101db
16Hz --- 107db





P.s I'll take some TRUE readings tonight!