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Frequency Response Measurements

Judas Priest

Judas Priest

Super Member
I finally bought an SPL Meter and did some low frequency response measurements today on my little Grundig Box 5600 speakers and my 18" sub.

The measurements were taken at the listening position. These little speakers put out more bass than what the chart would leave you to believe. I even thought the sub was on until I checked it :)

Here are two charts; one for the Grundigs and one for my sub.
 

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I use an Excel spreadsheet for third octave plots which contains a section for adjustments to your meter.

The following is optimized for the Radio Shack digital meter. You may easily change the values to suit your needs.
 
Your 70 (second sub measument) seems off :) So close to the 80 :)

Cross your sub over at 60.The charts shows overlap. Or is the sub chart with the mains on?
 
You noticed that, didn´t you? :)

I made a mistake and didn´t feel like redoing the chart :)

I measured the mains and the sub separately.

I am going to measure my Cerwin Vegas tonight. I am curious when they start to drop off.
 
I just measured my Cerwin Vegas. The SPL meter was about one meter from the woofer; I arbitrarily chose approximately 90 db C at 100 Hz as a starting point for the measurement. It has nothing to do with 1W/m or the sensitivity of the speaker.

Please ignore the cat hair bump at 20 Hz :)
 

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Judas Priest said:
I finally bought an SPL Meter and did some low frequency response measurements today on my little Grundig Box 5600 speakers and my 18" sub.

The measurements were taken at the listening position. These little speakers put out more bass than what the chart would leave you to believe. I even thought the sub was on until I checked it :)

Here are two charts; one for the Grundigs and one for my sub.
Click to expand...
If your device is accurate and your chart correct, then your speakers are not putting out more bass then the charts would lead you to believe, they are putting out exactly what the charts say. Belief has nothing to do with it.
 
@ Joe: I have heard from others that CVs drop off rapidly under 60 Hz, now I know that that is true. That´s why I built my sub.

I am also in the process of building a Linkwitz-Reily crossover to separate the signal to my CVs and my sub.

I will also be building a new enclosure for my sub soon.

@arcam: I trust measurements more than subjective impressions. The ears and mind are tricked so easily! I think that with many types of music there is very little content below 60 Hz. But if it is there, I want to hear it.
 
I finally got around to measuring my Grundigs with my 12" sub. I´m using a Mini DSP to cross them over at 80 Hz.

Are these mesurements bad, or are they okay?

Would it be worth it to try and get a near flat response curve using the Foobar parametric EQ?

Someday, when I can afford it, I´ll buy a calbrated microphone and let Room EQ Wizard do the adjustments for me. But for now,I would have to do it "by hand".resized_20170113_190910.jpg resized_Grundig Box 5600 AW30000.jpg
 
Without knowing the response curve of your microphone how do you know what frequency and how much to compensate for?

If you can find one of those Rat Shack SPL microphones (should be relatively inexpensive) most of the models have REW calibration files available for them.
 
Of course I don´t know the response curve of my SPL meter. But, I don´t think it would be more off that 2 or 3 decibles (?). Or would it?

Like I said, these are just the measurements that I can make at the time. I will buy a calibrated mic as soon as I can afford one.

Assuming the measurements are exact, are they good or bad?
 
I do not notice any details of the position of the microphone. Do keep in mind that at low frequencies there will be standing waves, thus dips and peaks in the response graph depending on room appointments and nature. A measurement taken at a particular position and one taken by moving the mic just 50 cm off might differ appreciably. Hence the loudspeaker output measurement is rather a function of the room - or if taken close enough to the loudspeaker, might show scant resemblance to what will be heard at a favouroite seating position.
 
I used A and C weighting; both curves are plotted.

The SPL meter was in my listening position; okay, maybe 50 cm closer to the speakers.

I think my system sounds great, but I am curious if it could sound better :)
 
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