I am sure people will see huge differences where I see little, but in these last few weeks before the election that's pretty common place.
Yes, with the peaks and dips in the frequency responses they're difficult to compare. I don't know what to make of it all. I couldn't see how one could draw useful conclusions from this, except that the monopole is much more efficient below 60 Hz.
Might it be interesting to add EQ based on a spatial average and then compare again?
John,
Would you provide us some more information to make useful conclusions.
Room size ?
Speaker position ?
Mic position ?
Wall (ceiling, floor) materials ?
Acoustic treatments ?
It strongly looks like you are not living in a stone house
- Elias
This is a dedicated listening room build in the basement of my home. The room is approximately 16' wide by 20' long. The ceiling height is nominally 7' 2" but is stepped by about 3' in one area and has an 8" drop down across the length about 3' wide (to cover AC duct work). There is a sub floor over the concrete which is fully carpeted. The back wall is studs build against the concrete basement wall. The side walls are 2x4 studs with sheet rock on both sides. These walls are not against the concrete basements wall as there are other areas to each side of the listening room. The front wall (behind the speakers is also 2x4 studs and there is an air space about 2' wide between this wall and the concrete basement wall. The ceiling is also sheet rock on the 8" floor joists above. All walls and ceiling is insulated with fiberglass. There is also an alcove along one side wall that extends to the back (listening end) and also leads to the staircase up. So the room has a "stubby L" shape.
There are medium weight drapes behind the speakers. Side walls and back wall have no acoustic treatment other that a scattering of pictured in frames. My listening chair and a TV on one side wall are the only furniture but there are several other speaker system stored in one corner and there is an equipment cabinet between the speaker positions.
The acoustic center of the woofer was 3' 3" from a side wall, 4'3" from the front wall. This is the nominal position of my speakers as well. The mic was 5' 8" from the back wall, 3' high and centered left to right, at the listening position. Over all, above 100 or 200 Hz, RT60 is about 300 to 350 msec, which is in line with BBC type rooms, which is what I prefer.
John ... my only gripe ... your choice of blue and violet. I can't tell which is which. Maybe a nice orange for either next time?
The violet trace is the middle one at low frequency. It acrually look more black than violet.
Although we don't have modulation analysis results from John's system so the comparison is not possible, based on CSD it looks like in a purpose built dedicated listening room the differences between sources seem to be moderate.
Now try the same in a small shoebox living room in a concrete condominium. A different story alltogether.
- Elias
Now try the same in a small shoebox living room in a concrete condominium. A different story alltogether.
- Elias
I have to admit that I am still struggling to understand the difference between the wavelet analysis and the raised cosine burst response. For clarity let me strees that the CSD is not a typical CSD. It is the burst response plotted as a waterfall. The sonogram is the same data, just plotted differently.
If the 'wavelet' is formulated having a raised cosine envelope then there is no difference with this 'non typical CSD', except slight mathematical issues like no imaginary part in a tone 'burst'. There are also different methods to calculate envelope. Overall it may also depend on how strick sense we need to define a 'wavelet'.
Still, one would hope to derive some modulation related parameters out from the measurements as it would give more relation of perception of music signals.
- Elias
Thanks John for posting the measurements.
Just wanted a few clarifications:
1) Were the three bass units equalised to have a similar bass extension.
2)What was the BW tested.
3)Was the same driver used in the three units...or is it the same cabinet that was interchangeable into a monopole/cardioid/dipole.
4)Since the measurements look very similar above 50 Hz, what was your subjective perception comparing the three. Even as per Dr. Geddes from 125 to 500 Hz, dipoles may have benefits over other units, perhaps due to directivity (if I understood him correctly).
Thanks again for your measurements.
Just wanted a few clarifications:
1) Were the three bass units equalised to have a similar bass extension.
2)What was the BW tested.
3)Was the same driver used in the three units...or is it the same cabinet that was interchangeable into a monopole/cardioid/dipole.
4)Since the measurements look very similar above 50 Hz, what was your subjective perception comparing the three. Even as per Dr. Geddes from 125 to 500 Hz, dipoles may have benefits over other units, perhaps due to directivity (if I understood him correctly).
Thanks again for your measurements.
Such a room probably doesn't generate the data we're looking for. The typical North American stud wall construction works as a good low frequency absorber. In Europe, one is more likely to find rooms with rigid walls and severe modal ringing.
Guys, you are not paying attention. In my first post I showed that all three sources have the same anechoic far field response. Differences in the in room results are due only to how the different sources behave in that room. Everything is fixed but source type.
See the top two plots in post 376
See the top two plots in post 376
Look at the burst decay. The only perceptual difference is probably caused by magnitude differences.
I'll post the impulse responses. I don't think you would say it's all that damped. My room is probably more rigid than a typical listen room here in the USA, particularly for the axial modes in the front to back direction where there are concrete walls directly behind, or within a couple of feet of the studded walls. What to you guys live in, concrete boxes?
I don't listen to test signals. I have no idea what they are supposed to sound like. As far as music goes, you may recall that the original NaO II had a woofer system which could be mechanically and electrically converted between U-frame quasi-cardioid and sealed box, with identical free field response. The NaO II RS has only the U-frame cardioid. That should tell you something. The only advantage I found with monopole subs was their greater efficiency so they could play louder. I haven't listened to dipole woofers for several years. They are just too inefficient for a small foot print full range speaker like the NaO II RS.
Also, in this test I am not trying to find optimum position for the placement of the woofers. I'm interested in how they perform in a typical stereo speaker setup.
Yes please - thank you.
What to you guys live in, concrete boxes?
Yes and there are steel bars in front of the windows
The walls at my current place are about 70cm (2.3ft) thick.
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