Proper Setup and Gain For Powered Subwoofers

[Captainmorgan89]

Hi guys,

Just received my LFM-1 Plus, LOVE IT!

Now, first off, should I invest in a Radio Shack SPL Meter ($49) and Avia II DVD? Will these help me to set the gain correctly for my room? What gain is recommended? 5/8? Half?

What, if any break-in, do you guys recommend?

Thanks!

 

[Sheep]

1.) Yes, those will be helpful.
2.) The Gain will be dependent on your room, and personal preferences.
3.) Break in will not do anything, don't waste your time.

SheepStar

 

[Warpdrv]

The Gain on a sub is not really a volume control, it is more like a sensitivity dial, the more sensitive you make it, the more it will respond/react to the signal coming in, and the louder it will get.

Or like a floodgate on a dam, the more you open it, the more flow it will allow.

 

[Captainmorgan89]

So being new these higher end subs, how far can they be pushed before damage takes place? That is, what type of sound should I be listening for that would indicate the speaker being overdriven?

 

[GlocksRock]

If you overdrive the sub, it will bottom out and you will know it, it will make a loud popping noise and you will recognize it right away.

 

[Captainmorgan89]

So I just measured the output of the subwoofer at 20 Hertz using my new Radio shack SPL meter.

With the sub set at 3/10, and my receiver at -18db, at 3m it said it was kicking out 76db. Horrible! Thats using the A weighting, with C it was 106db.

What does the SPL meter weighting determine and what is the best to use in this situation? A or C?

Thanks!

 

[Exit]

SPL measurements for audio setup use the “C” weighting scale and I forgot the technical definition of weighting scales. Actually a C weighting of 106 dB at 20 Hz should have been pretty loud to the point where you would be uncomfortable and want to turn it down.

The way I set it up is to download a sine wave generator program from the internet and generate a range of frequencies from about 200 Hz down to 20 Hz on a test CD. I have a BFD parametric equalizer and I try to get a smooth transition through the crossover range and then a gradual upwards rise towards 20 Hz. If you look up Behringer Feedback Destroyer on Google there is a BFD setup guide and a spreadsheet for correcting errors in the RS meter and plotting a more realistic frequency response curve. The spreadsheet lists the test frequencies to generate on the test disk. There is also a data record sheet to write in the measured data. If you don’t have a parametric equalizer to alter frequency response, you can experiment with speaker placement and the phase control to see if you can minimize any peaks in the frequency response. You want the transition through the crossover frequency to be smooth so there is no abrupt volume increase or dropout to occur. You may have to experiment with the crossover frequency and gain control to accomplish this. I am sure other people have other ways of doing this but it works for me.

 

[Captainmorgan89]

What is the best free tone generator out there?

Thanks!

 

[Exit]

I just searched the freeware/shareware sites until I found one. Mine was good for 30 days then you had to buy it if you wanted it for further use. I can’t remember what it was called though.

 

[Sheep]

So I just measured the output of the subwoofer at 20 Hertz using my new Radio shack SPL meter.

With the sub set at 3/10, and my receiver at -18db, at 3m it said it was kicking out 76db. Horrible! Thats using the A weighting, with C it was 106db.

What does the SPL meter weighting determine and what is the best to use in this situation? A or C?

Thanks!

What, you didn't like how your subwoofer sounded when you force fed it a 20Hz sine wave? Wow, what a piece of junk. I would never buy a subwoofer that couldn't play a sine wave, just the way I like it.

Seriously, calibrate the volume so it corresponds with the volume of your speakers and stop. You're going to break something.

SheepStar