Last year I finished the first round of tweaking a new passive crossover for my three-way speakers (Audax HM210Z0 and HM100Z0 and Scan-Speak D2905-9300). The speakers sound very nice and very easy to listen to, but are perhaps not as transparent or immediate as they might be with my push-pull 300B monoblocks, and have what I perceive to be a dark tonal balance.
I did some electrical measurements of the crossovers, and after some substantial work on impedance correction, they are now an excellent match to 4th-order Linkwitz-Riley, as intended.
So to get an idea whether the warm bias of the sound was an issue with the crossovers themselves or a room problem, I thought I would do some simple acoustic measurements. I played 20 seconds of a white noise track from a test CD, and then used a Panasonic EM60 microphone into an EMU0202 interface to feed this into Audacity, which I used to calculate a power spectrum. The mic is on axis about 50cm from the respective midrange driver, but for the moment I'm not being obsessive about position.
The room is about 4-5 metres square, with a couple of metres square cut out of one corner for the doorway; the room is carpeted, with soft furnishings and Venetian blinds on the windows. The speakers are about a third and two-thirds of the way along a long wall, and are about 20cm from the wall with a slight toe-in.
Here are the responses of the two speakers, first the left then the right channel:
![Click the image to open in full size.]()
![Click the image to open in full size.]()
The responses are quite consistent between channels, which is reassuring, and also perhaps surprising, since the room is quite asymmetrically laid out.
I note the following:
- A raised response between 1.5kHz and 2kHz;
- Some peaking between 3kHz and 5kHz;
- The relative magnitude of the peaks at 2kHz and 4kHz is different in the two speakers;
- A rolloff above 6kHz. I wouldn't expect this from the Scan-Speak tweeters, as they have a very flat response up to 15kHz or more (though I am measuring slightly off the tweeter axis).
So - first of all, should I expect to get results from this technique which are at all useful? In other words, are the three features I mention above likely to be real? Secondly, using white noise at 50cm, how much would you expect room effects to influence the measured response?
The regular peaks at the HF end (separated by about 800Hz) look suspicious to me. Are they likely to be a measurement artefact?
Any other comments would be welcome!
Thanks,
Alex
I did some electrical measurements of the crossovers, and after some substantial work on impedance correction, they are now an excellent match to 4th-order Linkwitz-Riley, as intended.
So to get an idea whether the warm bias of the sound was an issue with the crossovers themselves or a room problem, I thought I would do some simple acoustic measurements. I played 20 seconds of a white noise track from a test CD, and then used a Panasonic EM60 microphone into an EMU0202 interface to feed this into Audacity, which I used to calculate a power spectrum. The mic is on axis about 50cm from the respective midrange driver, but for the moment I'm not being obsessive about position.
The room is about 4-5 metres square, with a couple of metres square cut out of one corner for the doorway; the room is carpeted, with soft furnishings and Venetian blinds on the windows. The speakers are about a third and two-thirds of the way along a long wall, and are about 20cm from the wall with a slight toe-in.
Here are the responses of the two speakers, first the left then the right channel:
The responses are quite consistent between channels, which is reassuring, and also perhaps surprising, since the room is quite asymmetrically laid out.
I note the following:
- A raised response between 1.5kHz and 2kHz;
- Some peaking between 3kHz and 5kHz;
- The relative magnitude of the peaks at 2kHz and 4kHz is different in the two speakers;
- A rolloff above 6kHz. I wouldn't expect this from the Scan-Speak tweeters, as they have a very flat response up to 15kHz or more (though I am measuring slightly off the tweeter axis).
So - first of all, should I expect to get results from this technique which are at all useful? In other words, are the three features I mention above likely to be real? Secondly, using white noise at 50cm, how much would you expect room effects to influence the measured response?
The regular peaks at the HF end (separated by about 800Hz) look suspicious to me. Are they likely to be a measurement artefact?
Any other comments would be welcome!
Thanks,
Alex