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Frequency Response Measurement - First Attempt

This chart shows how changing to a measurement distance of 3 feet, versus 1.5 feet changes the response curve. I double checked the 100 Hz reading, the dip is there. At 3 feet, the high frequencies don't drop off nearly as much as measured at 1.5 feet.

The distance from the speaker was the only change made for this set of measurements.

Am thinking I should raise the crossover point from 1.6k Hz to 2.0k Hz and see what happens?
 
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The dip at 100 Hz is very likely a room node you have now found. You can move the mic around and plot its location.... :yes:
 
whoaru99 said:
What do you mean by "normalized to 80dB"?
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I have learned to try and set the volume knob on my preamp to get an 80 dB signal at 800 Hz. But, I don't always hit that exactly, so I average all the dB values measured at every Hz. And, the difference of this average from 80dB is added to the each actual reading. This allows me to compare subsequent readings on the same auido system or two different audio systems, even when the overall volume level was not exactly the same each time.

Basically, just a volume error correction method since I'm doing all this manually.
 
Here's what happens when you raise the crossover point from 1.6k Hz to 2.0k Hz. You can clearly see the boost in the 0.8 - 2.5k hZ range. No other changes were made, so the rest of the differences are run to run measurment error with my completely manual set up.
 
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BmWr75 said:
Here's what happens when you raise the crossover point from 1.6k Hz to 2.0k Hz. You can clearly see the boost in the 0.8 - 2.5k hZ range. No other changes were made, so the rest of the differences are run to run measurment error with my completely manual set up.
Click to expand...

Thats a huge suckout between 65-100hz
 
In the time spent making your next measurement...you could have downloaded, installed, and calibrated REQW. ;)
 
BmWr75 said:
Here's what happens when you raise the crossover point from 1.6k Hz to 2.0k Hz. You can clearly see the boost in the 0.8 - 2.5k hZ range. No other changes were made, so the rest of the differences are run to run measurment error with my completely manual set up.
Click to expand...
NOW we're havin' speakergeek FUN! :thmbsp:
 
OK, whoaru99, you've said it twice. I'm gonna get that sucka and see what it does. Sounds like the real stuff. I've been trying (between rebuilding a KLH-17 and doing Real Work) to get Speaker Workshop going. Have also tried Winisd & a couple others. Sure would be nice if something came along that's cheap, reasonably intuitive and works the first time!
banghead.gif
 
whoaru99 said:
In the time spent making your next measurement...you could have downloaded, installed, and calibrated REQW. ;)
Click to expand...

Am not sure I have the right cable to hook the SPL meter to my sound card. Looks like the SPL meter needs an RCA plug and my sound card needs an 1/8 inch plug. Will have to look around and see if I have all the cables to do this.
 
that big "suck out" between 60 and 100 Hz is probably all room mode. You might want to spatially average your low frequency measurements. The are pretty omnidirectional below 100Hz. You might need to change your mic position by 5 feet or so for the LF stuff. Every position you choose will exhibit some measurement error. That is the 'fun' of eq'ing in a room.
 
BmWr75 said:
Am not sure I have the right cable to hook the SPL meter to my sound card. Looks like the SPL meter needs an RCA plug and my sound card needs an 1/8 inch plug. Will have to look around and see if I have all the cables to do this.
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The famous Shack has a cable already set up to do this - #42-2551. Has stereo 1/8" on one end and 2 RCA plugs on the other and ~6' of wire in between. I leave it to you to figure out which one is the left channel. :stupid:

Guess how I know about that cable...
 
Paratima said:
The famous Shack has a cable already set up to do this - #42-2551. Has stereo 1/8" on one end and 2 RCA plugs on the other and ~6' of wire in between. I leave it to you to figure out which one is the left channel. :stupid:

Guess how I know about that cable...
Click to expand...

Must be like the ones I bought...dunno if they were from the Shack, but red isn't right on both sets cables. :scratch2:
 
whoaru99 said:
In the time spent making your next measurement...you could have downloaded, installed, and calibrated REQW. ;)
Click to expand...

OK....I downloaded REQW....nice looking software. Found all the cables needed to hook the SB Audigy 4 sound card to the SPL meter. And have started reading the HELP section. Am not sure I know how to calibrate my Radio Shack SPL Meter model 33-2050 using the software. Or, am I supposed to load a correction factor file from somewhere to correct the errors in the SPL meter? :scratch2:
 
Yes. You download the SPL meter correction factors.

I've attached the cal file, but note it has a .txt extension. When you save this file, change the .txt to .cal, then you can load in the .cal file from the Mic/Meter tab of the Settings menu.
 
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whoaru99 said:
Yes. You download the SPL meter correction factors.

I've attached the cal file, but note it has a .txt extension. When you save this file, change the .txt to .cal, then you can load in the .cal file from the Mic/Meter tab of the Settings menu.
Click to expand...

Thanks whoaru99. Have saved the file and loaded it into REQW using the settings page.

Here's the next problem I encounter. I can play tones from the REQW software through my audio system. But, as soon as I plug the cable into the SPL meter output, it pegs the meter, regardless of the dB range I select. That's not right, but am stumped as to why its happening.
 
Sounds like you might have the soundcard output going to the meter instead of the meter going to the soundcard input. Also, you must use the line input on the sound card, not the mic input.
 
whoaru99 said:
Sounds like you might have the soundcard output going to the meter instead of the meter going to the soundcard input. Also, you must use the line input on the sound card, not the mic input.
Click to expand...

I'm learning, did have the SPL meter hooked to the mike input on the soundcard, but switched the red RCA plug to the white RCA plug in the meter and it started working.

I then switched to the line input on the soundcard and everything still appears to be working. Red not always equal right, as someone previously stated.
 
Ended up having to use the microphone input on my soundcard. The line input only worked on one channel for some reason. Soundcard and SPL meter calibrations went fine.

Attached measurement graph is using 1/6 octave smoothing. Measurement was taken using a RS SPL Meter sitting in front of my listening position on a speaker stand (not ideal) which placed it at the top if the woofer on a horizontal plane. The speakers are the Zilch/Heath ones built earlier this year.
 
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It's wrong above 10 kHz. Need to be on-axis with the tweeter.

Get the mic stand and mount adapter to work under standard conditions.

The room interference node has now moved to 300 Hz.... :yes:
 
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