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Salk is using the original design. The change to aligned drivers was because Dennis had to change cabinets.
Good to know.
Salk is using the original design. The change to aligned drivers was because Dennis had to change cabinets.
First off, thanks be to Erin for his detailed analysis. That was quite an investment in time and effort, and I, as a speaker designer, particularly appreciate it. There's a lot to digest here, and I'll have a more detailed response a little later. For now I just want to discuss the distortion plots a little, since I think that's the only real negative that jumps out at you. The RAAL is the culprit, and it's pretty much inherent in the design approach. All ribbons will show an increase in distortion at the bottom of their operating range. That's the flip side of the extremely low mass of the ribbon element. Even with the very strong magnetic field present in these designs, the ribbon will flex more than a typical 1" dome as the wave lengths increase.Pretty sure it's the RAAL 64-10, it's why it needs to cross above 3k.
Not quite. Jim is using a picture of the old design. What's coming out of his shop is the newer in-line version. I switched to in-line drivers because (1) People didn't like the looks of the offset drivers, (2) For the most recent Chinese BMR's, I didn't trust the factory to ship matched mirror-image pairs, and (3) The in-line version measured and sounded at least as good. BTW, the BMR tested by NRC had offset drivers and the off-axis response is a little different.Salk is using the original design. The change to aligned drivers was because Dennis had to change cabinets.
Man, I literally just updated my paragraph on this. I was driving my kid and dog to the creek and it kind of *hit* me that I didn't think to mention this aspect. I definitely agree that the PIR may not cover edge cases such as this. But I don't know for sure. I do know that this speaker did not sound remotely as bright as the PIR curve indicates. I agree there is more than meets the eye here. And I also believe the target curve in comparison with a speaker like this may be a bit misleading.
This doesn't apply to you, but it's why I always worry when some take the ideal slope of the PIR too literally, and another reason to be cautious with the preference score's if a speaker features unusually wide of narrow directivity. I personally don't think we should be trying to correct the slope of the PIR when we EQ unless the on-axis isn't flat. I prefer to EQ to the speaker's natural directivity slope, though thankfully most speakers aren't too far off from the norm.
Gotcha. I wonder if any customers got confused when their order arrived.Jim is using a picture of the old design. What's coming out of his shop is the newer in-line version.
This doesn't apply to you, but it's why I always worry when some take 9-10dB down slope of the PIR far too literally, and another reason to be cautious with the preference score's if a speaker features unusually wide of narrow directivity. I personally don't think we should be trying to correct the slope of the PIR when we EQ unless the on-axis isn't flat. I prefer to EQ to the speaker's own directivity slope, though thankfully most speakers aren't too far off from the norm.
Part of that is due to an inherent air leak, addressed by sealed ribbon tech. Right now it's patented but could be interesting long-term.All ribbons will show an increase in distortion at the bottom of their operating range. That's the flip side of the extremely low mass of the ribbon element. Even with the very strong magnetic field present in these designs, the ribbon will flex more than a typical 1" dome as the wave lengths increase.
Part of that is due to an inherent air leak, addressed by sealed ribbon tech. Right now it's patented but could be interesting long-term.
I have noticed that for near field driver measurement, both woofer and tweeter goes up around 1k to 2k Hz. The volumes were pretty high, only -10db compare to intended output. Is it a bad thing or it does not matter much?
The crossover for woofer and BMR looks like to be 550 Hz. Why choose a crossover point this low? Because of directivity or phase alignment? I think the 400 to 500 Hz distortion spike comes from the BMR. The distortion is actually not bad because at normal listening level of 88db, it is less than 1%, but I am still curious why choose crossover at 550 Hz.
nice review. I don't think this is true though. Google suggests this uses an LR4 at 600 & 3500Hz so you'd expect to see these 3 separate peaks in the step response.Zoomed and annotated for the arrival time of each drive-unit’s impulse. You can see the drivers are not time-aligned and arrive distinctly separately. The difference in time between the woofer (2.5ms) and the midrange (1.33ms) is approximately 1.2ms. To put this in perspective, 1.2ms is approximately 16 inches.
I definitely agree that the PIR may not cover edge cases such as this. But I don't know for sure. I do know that this speaker did not sound remotely as bright as the PIR curve indicates. I agree there is more than meets the eye here. And I also believe the target curve in comparison with a speaker like this may be a bit misleading.
Thank you for reply. I saw the review of BMR on hificompass, the distrotion is already more than 1% at 500 Hz, so that's what my concern was. This review showed better distortion than I expected, the crossover is perfect that the lobing is not visible even with 40 degree off vertically. I have seen the facebook post regarding new driver, they said the mid voicing is a bit different for the new one, what is your opinion on the new one?I can't help you out with the near field driver measurements, because I don't know what they mean or why they are relevant. What matters is how the individual drivers measure at the intended listening distance and at one meter. For the BMR, either at 3 meters (design distance) or one meter (usual measuring distance), the individual driver slopes are monotonically declining and follow smooth 4th order roll offs over most of their range(See attached).
As for the woofer-midrange crossover frequency, the actual crossover point at the listening position is 610 Hz. That doesn't strike me as low, given that this model BMR mirange is usually crossed a good bit lower than that (e.g. Cambridge Audio Aero 2), and the factory specs for operating range are 250 Hz on up. Plus, the acoustic slope is very steep, so the mid shouldn't be unduly stressed. However, the crossover point was chosen mainly to use only the smoothest portion of the Scan 8545 woofer. I wanted the first portion of the woofer roll off to be as close to target as possible to optimize phase and system frequency response. That said, the next generation of BMR's (available in October) will have a new woofer that is much smoother in the 800 Hz - 2 kHz range, and I've not only bumped the crossover point up 200 Hz, but I'm using 2nd order acoustic slopes to improve sensitivity due to greater bandpass gain.
Here is a zipped file with all of the measurement angles included in case anyone wants to tackle this.
https://www.dropbox.com/s/jcl7jc8q0z770d5/PhilharmonicBMR.7z?dl=0
Again, for those thinking this is low, the very wide directivity is not something the formula likes.Pref Score : 5.1
Pretty good speaker, too bad it complicated to get in Europe.
(The link to the flat-pack leads back to Your home page.)
The ribbon, sealed or not dictates a higher x/o frequency, but still it distorts considerably. We have uneven directivity in the vertical, the possible mechanical vulnerability, the high price. For not more than a tiny bit of wider dispersion in the tops of the hights.
The BMR again dictates a higher x/o due to otherwise too high of distortion figures. Even bigger problems in respect to vertical directivity.
The woofer is expensive, especially when compared to more contemporary offers. With a more competent mid the x/o would be more relaxed, the woofer could have been way cheeper. Alltogether with less intermodulation, where the woofer is always the main contributor.
So, it seems funny, but the measurements don't look that bad. Two things appear less fortunate to my eye.
- The curved sidewalls are inacceptable, design-wise.
- The distortion, whether perceptible or not, must not be. One might argue, that these aren't that bad, because of and so forth, o/k. But from the standpoint of technical evaluation they are at least a hiccup.
One might take a specific distribution of maximum level versus frequency into account, as it is demanded by a typical music program. To some accuracy it can be discribed as this:
https://www.hifi-selbstbau.de/images/stories/grundlagen/waveana/Track260MaxL.png
So, the demand in the deepest bass region is considerably less than mostly anticipated. Demand in lower treble is way less than in the mids. But even with the lowest levels the ribbon distorts in the 2..3% region.
A second irregularity is the interference that comes from the baffle dimensions. The discontinuity in the dispersion comes up around 3..4kHz.
And third the compression has a hot spot exactly there.
I think the ribbon is clearly the archilles heel for the overall design. I assume it is the most expensive single part. Does it make sense, really?
I think the ribbon is clearly the archilles heel for the overall design. I assume it is the most expensive single part. Does it make sense, really?