The Mysterious Analog Bass Management Knobs - USP-1 (XSP-1?)

[Boomzilla]

OK - Using my calibrated UMIK-1 USB microphone and "FuzzMeasure" software for Mac - I've created the following charts. The speakers involved are Tekton Pendragon models. For purposes of these graphs, "ZERO CLICKS" is the minimum position of the USP-1's high-pass filter, and every click up represents one marked unit going up (clockwise) from the minimum position. On the preamp, the minimum position is labeled "50 Hz" and the maximum (10 clicks) as "250 Hz."

Although these measurements were taken with an Emotiva USP-1 preamp, I'd expect similar behavior from the XSP-1 models (versions one and two) as well. All this is just a FYI:

ZERO CLICKS - Minimum pot position - Labeled "50 Hz.":

ONE CLICK:

TWO CLICKS:

THREE CLICKS:

FOUR CLICKS:

FIVE CLICKS (12-O CLOCK):

SIX CLICKS:

SEVEN CLICKS:

EIGHT CLICKS:

NINE CLICKS:

TEN CLICKS (labeled "250 Hz."):

Cheers - Boom

PS: Assuming that the mean amplitude of the Pendragons is -12 dB on these scales, here's the effect of the USP-1's high-pass filter on the Pendragons' 40 Hz. peak"

@ 0 clicks = -0 dB
@ 1 click = -1 dB
@ 2 clicks = -0 dB
@ 3 clicks = -0 dB
@ 4 clicks = -3 dB
@ 5 clicks = -4 dB
@ 6 clicks = -6 dB
@ 7 clicks = -10 dB
@ 8 clicks = -12 dB
@ 9 clicks = -24 dB
@ 10 clicks = -24 dB

And based on these numbers, it's fair to say that the rheostat used to manage bass is a log-taper pot.

[musicfan]

how come i cant see any of the images?

[Boomzilla]

Uh - Oh - I posted them to Google-Drive & then copied the addresses - Do I need to do something else?

[RichGuy]

None of your images are working for me, I see where 10 images should appear but not the images.

Now they work

[macromicroman]

I can't see them either.

[garbulky]

I can see the images fine. Your waterfall plot seems to indicate signficant reverberations and echoes up to 1 second long (the limits of your measurement). Unless that was done on purpose. I'm no expert at reading these graphs

[garbulky]

Wait they just stopped working

[Boomzilla]

Now they aren't visible to me either. I selected the images in Google Drive, selected the "Get Sharable Link" option and copied the URL to the Lounge. Should work, but now not even I can see them. Any idea why?

[RichGuy]

They did not work for me until I made my post above, after posting they appeared. I'm not sure if you fixed something or they are sometimes not appearing.

[RichGuy]

Now they have stopped again for me as well.

[Boomzilla]

The first image is currently the raw URL of the image. The rest are what Google Drive claims are "shared" images. Which can y'all see?

[RichGuy]

This works very well for posting images and it's free postimages.org/

[RichGuy]

I can now see the first

[Boomzilla]

OK - I put them all back as they were to start with. DAMN Google Drive!

[RichGuy]

All were working for me as I went to post this.

[foggy1956]

Jul 30, 2017 15:33:04 GMT -5 garbulky said:

I can see the images fine. Your waterfall plot seems to indicate signficant reverberations and echoes up to 1 second long (the limits of your measurement). Unless that was done on purpose. I'm no expert at reading these graphs

If I remember correctly in REW if you have a 20db drop in about the first 350ms you are doing pretty well.  These graphs are nowhere near as detailed as REW's and as such I am not sure if that is happening but it does appear to be close.

[Boomzilla]

And as a bonus, here's the FR on the PowerSound Audio S3601 dual 18-inch subwoofer:





Measurements, again, taken 1 meter from the sub with the microphone centered vertically & horizontally.

[RichGuy]

Now the last two aren't working the first 10 do.

[musicfan]

these graphs are terrible...use REW

[foggy1956]

Jul 30, 2017 15:11:49 GMT -5 Boomzilla said:

OK - Using my calibrated UMIK-1 USB microphone and "FuzzMeasure" software for Mac - I've created the following charts. The speakers involved are Tekton Pendragon models. For purposes of these graphs, "ZERO CLICKS" is the minimum position of the USP-1's high-pass filter, and every click up represents one marked unit going up (clockwise) from the minimum position. On the preamp, the minimum position is labeled "50 Hz" and the maximum (10 clicks) as "250 Hz."

Although these measurements were taken with an Emotiva USP-1 preamp, I'd expect similar behavior from the XSP-1 models (versions one and two) as well. All this is just a FYI:

ZERO CLICKS - Minimum pot position - Labeled "50 Hz.":



ONE CLICK:



TWO CLICKS:



THREE CLICKS:



FOUR CLICKS:



FIVE CLICKS (12-O CLOCK):



SIX CLICKS:



SEVEN CLICKS:



EIGHT CLICKS:



NINE CLICKS:



TEN CLICKS (labeled "250 Hz."):



Cheers - Boom

PS: Assuming that the mean amplitude of the Pendragons is -12 dB on these scales, here's the effect of the USP-1's high-pass filter on the Pendragons' 40 Hz. peak"

@ 0 clicks = -0 dB
@ 1 click = -1 dB
@ 2 clicks = -0 dB
@ 3 clicks = -0 dB
@ 4 clicks = -3 dB
@ 5 clicks = -4 dB
@ 6 clicks = -6 dB
@ 7 clicks = -10 dB
@ 8 clicks = -12 dB
@ 9 clicks = -24 dB
@ 10 clicks = -24 dB

And based on these numbers, it's fair to say that the rheostat used to manage bass is a log-taper pot.

Boom,
If this were an REW graph I would think the ideal would be a flat line from 100hz on down, no idea why your lower frequencies are rolling off like that.  Is this with subs or just the dragons with the lower frequencies rolling off below the xover because the subs aren't involved?