Need help w/two BFD issues

I have a DSP1124 and am working to get my sub a little flatter and better integrated with my mains. There are a few issues I've run into that I could really use some help with. One is that there is roughly a 13db peak at 47Hz that I simply cannot do anything with. I've tried adjusting frequency,Q and gain multiple times and there is seemingly no effect at all. I tried moving the filter to a different position within the preset and that didn't work. I tried moving the x-over point up and down on the receiver to no avail. I've used analog connection to receiver and digital connection, tried stereo (2.1) and DolbyPLII (5.1) and the result is always the same.Is this an uncommon experience? FR is as if no filter is even set at that frequency regardless of what I try. The ohter two filters I'm using within that preset are fine and working as they should.

Next up, room gain (I think). Toward the low end I'm pretty flat to about 16hz and then I'm up 10db@10hz relative to the rest. There are no filters below 20hz on this BFD. Any ideas?

[brucek]

13db peak at 47Hz that I simply cannot do anything with

There are only two reasons I've ever encountered for the problem you describe.

1. The filter mode is OF and not PA.

2. There is a decimal before the frequency value which denotes KHz rather than Hz..
So, to create 47Hz, you should set 50Hz -6 fine, but you may have it set to .50KHz -6 fine (=+470Hz).

Simply use REW to send a 47Hz tone through your system and play with the BFD dynamically on its front panel.....

brucek

Man you guys are fast! I'm praying that it is one of those two issues you describe. Off to go check.

[Wayne A. Pflughaupt]

Another potential cause would be if the mains are running full range...

Regards,
Wayne

That certainly went a long way toward helping me out. I somehow missed the decimal (hope I wasn't the first) and now have a functioning filter. Time to get back to tuning. Any thoughts on the peak at 10hz?

[brucek]

Any thoughts on the peak at 10hz?

Not too much a BFD can do to 10Hz. Its lowest filter is 20Hz (as I'm sure you know).

Corner loading a sub usually brings out these low peaks. Perhaps moving the sub can be of some help, although if it's producing 10Hz, I'm sure it's not too light.... Either way, location (or adding a subsonic filter) will be your best bet.

brucek

It is corner loaded, but unfortunately I'm not able to change the location of the sub. At least not until I graduate from the living room to a dedicated theater space. For the life of me I can't see how I'm getting useable 10hz from this thing. All the modeling I did in winisd pro alpha indicates that i've considerably exceeded exeeded xmax to play at that frequency/output level. Nothing special, a pair of JLAudio12W0-8 woofers in isobaric sealed 2.4ft^3 box with 250 watts. I doubt it weighs 25lbs. Perhaps the winisd doesn't model correctly for isobaric set-up?

[bjs]

toenail wrote:

... For the life of me I can't see how I'm getting useable 10hz from this thing...

Given that, are you sure it is real output from your sub and not low frequency noise in your environment getting picked up in your measurements?

bjs wrote:

Given that, are you sure it is real output from your sub and not low frequency noise in your environment getting picked up in your measurements?

With no tone playing I get nothing out of the meter. When I play 10hz I get uncorrected response of 52db, 11hz=56db, 12hz=58db, 14hz=58db, 16hz=59db etc. When I input the data to the spreadsheet I downloaded from this site it does the compensation for my meter (radio shack 33-2050) and shows compensated output while ploting it on a graph. I would gladly post the graph if I could figure out how to do that. I'm a newb with this stuff. The spreadsheet shows 10hz=82.4db, 11hz=83.6db, 12hz=81.5db, 14hz=78.3db, 16hz=76.1db etc. You get the picture. I can certainly feel the pressure in my sinuses at 10hz=82.4db.

[brucek]

I would gladly post the graph if I could figure out how to do that.

Here's how to post a graph.

brucek

Thanks for the tip brucek. I was able to save the chart to mspaint but when I try to upload into a post I'm told it's too big @1.34mb. I need to see if I can host it to my isp and include a url.