Yeah! Here they are.
I didn't forget to use the calibration this time, I've just hidden the microphone response! 😆
Also, I didn't disconnect the tweeter.
I didn't forget to use the calibration this time, I've just hidden the microphone response! 😆
Also, I didn't disconnect the tweeter.
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That's because I took the first impedance measurements in free air, outside the box, because for the type of crossover I wanted to realize low-end impedance didn't matter. However, I took some more impedance measurements of the entire speaker! There's a smaller peak at 43Hz and a bigger one at 110.
The lowest point is at about 62Hz, that should be the tuning frequency of the box right? If so I think I'm just dealing with an high-ish Qts woofer rather than a box that is tuned too high.
The lowest point is at about 62Hz, that should be the tuning frequency of the box right? If so I think I'm just dealing with an high-ish Qts woofer rather than a box that is tuned too high.
IMHO the quickest trick with this type of speakers is to employ a 1st order Series XO without any Zobels and maybe with Rs/Rp on the tweeter if necessary. Choose your XO frequency wisely but don't be too worried, it's a self adjusting circuit.
The tuning of your box looks like an ML-TL to me, not a regular BR, which is good. That might explain the scarcity of damping material inside the box.
The tuning of your box looks like an ML-TL to me, not a regular BR, which is good. That might explain the scarcity of damping material inside the box.
I've already made the new crossover, it's a 3rd order electrical for the HP and 2nd order electrical for the LP, the acoustic crossover point is at 3.1kHz. I'm pretty satisfied with it.
Why do you say it's a MLTL and not a BR? I barely know anything about transmission lines.
When I added acoustic foam inside the speaker the sound improved by quite a lot. It became less boomy (the 150Hz region dropped by about 2dB) and also the midrange became more detailed. I had a null at about 2kHz which disappeared when I put the sound deadener.
I was thinking about using a 1st (or 2nd with very low Q) order active high pass filter at about 100Hz to smooth the response and also improve power handling and distortion. These speakers will be very likely used in conjunction with a 10" subwoofer which I already have which will take care of the region under 100Hz.
Why do you say it's a MLTL and not a BR? I barely know anything about transmission lines.
When I added acoustic foam inside the speaker the sound improved by quite a lot. It became less boomy (the 150Hz region dropped by about 2dB) and also the midrange became more detailed. I had a null at about 2kHz which disappeared when I put the sound deadener.
I was thinking about using a 1st (or 2nd with very low Q) order active high pass filter at about 100Hz to smooth the response and also improve power handling and distortion. These speakers will be very likely used in conjunction with a 10" subwoofer which I already have which will take care of the region under 100Hz.
Indeed! Mentioned it a couple of times using a cheap pot on similar threads to 'deaf ears', so said to heck with it.
Don't believe it has a high enough aspect ratio to be a MLTL and agree that it's probably just due to a high Qts driver requiring a < Fs tuning for flattest response.
Here are some measurements I took outside. It wasn't the quietest environment possible but at least I could measure something. Each angle was measured twice to reduce the noise. The microphone was placed between the woofer and the tweeter 1.20 meters away from the speaker. The speaker was placed on a ladder which was about 1.5 meters high.
Red= on axis
Green= about 20 degrees off axis horizontally
Blue= about 45 degrees off axis horizontally
Fellow SB-PM01 owner here... well, technically, they're my parents' PC speakers. Those were stuck behind a monitor for years and only recently the whole setup was moved to the desk with lots more space, they even got desk stands now (~21 cm high). Here are some stock measurements (grilles on) in situ on their SA-PM01 receiver (tone controls at 0) taken with my Sonarworks SoundID Reference mic, moving microphone method, mic kept pointing towards speaker, 0° compensation, 1/48oct smoothing for comparison:
(Red: left, green: right.) Both have a serial number of TQ8IA48143. Sample variation seems low.
I would have fairly high confidence from about 500 Hz up (especially the right = green one which is approaching free-standing), below 300 is a bit messy as the circles I was making weren't particularly large but can serve as general guidance.
There are some similarities but also a number of noteworthy differences to @Vic1184's set. They start diverging sonewhere around 1.2 kHz. The woofer in ours would seem to be better-behaved on the whole, e.g. the ~10 kHz breakup is well short of the tweeter's peaks.
For the time being I threw 18 PEQ bands at the whole affair (13 wouldn't cut it), 17 automatic plus 1 more manual to fill in around 75 Hz. Predicted responses:
(Green: left, blue: right.)
I may still experiment with some loose cotton wool or similar in front of the woofer, there should be enough space behind the grille cloth. As-is, the sound is leaps and bounds better than it used to be, although I do notice a slight treble coarseness / sharpness that improves when blocking the path between the woofers and my ears. Unfortunately, I do not have a parts box with used crossover components, so would have to buy everything.
The next issue to address would be the SA-PM01's hiss level when cranking it. Especially for classical, I have to turn the volume up past -20 dB, at which point it gets quite annoying. Unsurprisingly, the electronic volume/tone ICs in quarter century old inexpensive micro stereos are not exactly HiFi grade; I'll have to look for a higher-performance replacement unit.
Here are some pictures of the drivers and the measured response of the speakers as they came from the factory (scale is 10db/div):
(Red: left, green: right.) Both have a serial number of TQ8IA48143. Sample variation seems low.
I would have fairly high confidence from about 500 Hz up (especially the right = green one which is approaching free-standing), below 300 is a bit messy as the circles I was making weren't particularly large but can serve as general guidance.
There are some similarities but also a number of noteworthy differences to @Vic1184's set. They start diverging sonewhere around 1.2 kHz. The woofer in ours would seem to be better-behaved on the whole, e.g. the ~10 kHz breakup is well short of the tweeter's peaks.
For the time being I threw 18 PEQ bands at the whole affair (13 wouldn't cut it), 17 automatic plus 1 more manual to fill in around 75 Hz. Predicted responses:
(Green: left, blue: right.)
I may still experiment with some loose cotton wool or similar in front of the woofer, there should be enough space behind the grille cloth. As-is, the sound is leaps and bounds better than it used to be, although I do notice a slight treble coarseness / sharpness that improves when blocking the path between the woofers and my ears. Unfortunately, I do not have a parts box with used crossover components, so would have to buy everything.
The next issue to address would be the SA-PM01's hiss level when cranking it. Especially for classical, I have to turn the volume up past -20 dB, at which point it gets quite annoying. Unsurprisingly, the electronic volume/tone ICs in quarter century old inexpensive micro stereos are not exactly HiFi grade; I'll have to look for a higher-performance replacement unit.
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