New sub, some same old questions

[Mark Holmes]

I would appreciate a bit of help here.

I have a new DIY sealed sub that I am integrating into my system. I am using a Bassis and a BFD.

What I am trying to get is a response curve flat to 10 Hz. The Bassis is incredible in boosting the low end. And I am working on the BFD to smooth things out. I am almost there but...

First question. What does a driver sound like when you reach excursion limits?

Next, Why does it seem that when I limit frequencies above 20 Hz that the output below 20 Hz increases?

Finally, I have a 4 year old Rat Shack meter, and am still confused as to what correction factors I should be using below 20 Hz.

Down around 10 Hz, I mostly hear things shaking in the room.

Thanks,

[brucek]

I have a 4 year old Rat Shack meter, and am still confused as to what correction factors I should be using below 20 Hz

There are three different Radio Shack meters and the model numbers with calibration files are here.

brucek

[Mark Holmes]

Oops, I should have said that I had the old style 33-2050 meter. Sorry.

Is there any accurate data below 16 Hz. I get really significant output down low. If I could figure out how to save the spreadsheet in a small enough format, Iwould post my results. But if the correction factor at 16 Hz is correct, I am getting astonishing output down low. And I need to rethink the boost I am applying.

I really may be flat to 10 Hz.


Thanks,

Mark

[brucek]

Is there any accurate data below 16 Hz.

The url in my post above shows where to get the calibration file for that meter. It goes to 10hz..

[Mark Holmes]

Thanks Bruce,

I was looking at the spreadsheet which only went down to 16 Hz. What am I supposed to do with the .cal file?

[brucek]

I was looking at the spreadsheet which only went down to 16 Hz. What am I supposed to do with the .cal file?

Most people around here use a software program called REW. It is free and downloadable. REW uses the .cal files.

But you can also modify the Excel file if you are inclined. The .cal file is a simple text file that can be read with Windows Notepad. The compensation values could be used in the excel file to extend it down to 10Hz. Using the same 1/6th octave spacing as the existing excel chart would add the 4 values below 16Hz(15.874) of :

14Hz(14.14) = -18.61 dB
13Hz(12.6) = -20.13 dB
11Hz(11.22) = -24.15 dB
10Hz(10.00) = -27.00 dB

I would recommend taking a look at REW...

brucek

[Mark Holmes]

Thanks, sorry for bing so uninformed...

Wow, 27 dB at 10 Hz... That means I am seeing over 100 dB at 10 Hz! It is kinda hard to believe I am getting that much output down that low.