Sony SS-CCP500 2-4k frequency dip

[ansluk]

Hello,

I recently replaced an old malfunctioning mini stereo with a WiiM amp pro. I was going to get new speakers as well, but couldn't decide what to get so I thought I'd use the speakers(ss-ccp500) from the Sony mini system for a while. Thinking of the EQ possibilities in the WiiM, I made an attempt to measure the frequency response of the Sony speakers.
I measured using an Omni1 mic from Line Audio that's supposed to be pretty flat, but I don't have a calibration file. It looks like there is a pronounced dip of around 7dB between 2000hz and 4000hz. I generated a test file with tones at 1800, 3000 and 4200hz, double checked levels 30 cm from the speakers with a cheap dB meter(+-1.5dB accuracy) and one speaker was down 7dB and the other 10dB at 3000hz compared to 1800 and 4200.
Is there any chance that the 2-4k dip isn't real? I don't have that much space so I only managed an on axis mic distance of 80cm without reflective surfaces getting to close.
If it's real, is this expected performance from speakers bundled with mini stereos from 2002 or could anything have gone wrong with the crossovers after close to 25 years?

Thanks

 

[AnalogSteph]

Try taking some nearfield measurements of both woofer and tweeter to get a feel for their respective individual responses. The drivers are given as a 4.5" cone and 1" semi-dome (the response past 12 kHz sure looks more like cone than dome tweeter), so I wouldn't be surprised to see a crossover as high as 4-5 kHz. They may just not mesh very well in the problematic region, or it may just be a pure woofer thing. The phase response would suggest a change in origin location around 4 kHz.

With speakers like these you have to be prepared for some eccentricities. Consider yourself lucky if the crossover consists of anything more than a single small electrolytic. That may be worth changing if it's of dubious origin, but don't expect too much.

 

[DVDdoug]

I'd assume it's real although it may not be exactly as you are measuring it.


FYI - SPL meters are for measuring "loudness" and they usually don't have flat response. But a dip in the mid-frequencies is the opposite of what you'd usually get. On the other hand, if it's correlating with what the mic is showing that's good.

SPL measurements are usually A-Weighted which rolls-off the highs & lows to (very roughly) approximate human hearing. If the meter has setting for Z-weighting that's supposed to be flat, but I still wouldn't use it for frequency response.

 

[ansluk]

Thanks for the advice! So that's why the units on the SPL meter says dBA. You were quite right about the single electrolytic crossover. The valley between 2 and 4k remains when measuring the woofer nearfield and also when disconnecting the tweeter. I assume that means it's a woofer thing I can't do much about.