Philharmonic BMR Monitor Semi-Objective Review - Road Show Stop 1

[Dennis Murphy]

Erin's plots above are the old BMR. Doesn't the new one have a lower order low end crossover, so much different step response? Has it been measured?

The current BMR uses a second order (acoustic, not electrical) cross from the woof to the mid, and 4th from the mid to the tweet. I haven't seen any measured step response for it.

 

[thewas]

In my experience the biggest audible difference of vertically longer tweeters like bigger ribbons and AMTs is their higher vertical beaming which significantly influences the total sound power and floor and ceiling reflections, since on the previous page the horizontal directivity of the Philharmonic BMR to the Ref 1 Meta was compared, here is the vertical one which shows that:

 

[Dennis Murphy]

In my experience the biggest audible difference of vertically longer tweeters like bigger ribbons and AMTs is their higher vertical beaming which significantly influences the total sound power and floor and ceiling reflections, since on the previous page the horizontal directivity of the Philharmonic BMR to the Ref 1 Meta was compared, here is the vertical one which shows that:

View attachment 205290View attachment 205291

The BMR actually has wider vertical dispersion than I remembered. But it is certainly restricted compared with a coaxial or a lot of other dome speakers. Counter-intuitively, however, the BMR actually throws a very tall sound stage. When switching to most other speakers, the sound stage seems to collapse inward and sound a little pinched in comparison. We have a long way to go in assessing the impact of differing patterns of vertical dispersion.

 

[moonlight rainbow dream]

Dennis,

Have you worked with any designs using 3/4-inch or 1/2-inch domes? On paper, don't they offer the same wide dispersion that ribbons do?

 

[Dennis Murphy]

Dennis,

Have you worked with any designs using 3/4-inch or 1/2-inch domes? On paper, don't they offer the same wide dispersion that ribbons do?

I've never used a 1/2" dome (are there any that aren't really super tweeters?), but I've done a bajillion with the Hiquphon 0W1 3/4". But as I posted above, the sound character still isn't like a ribbon.

 

[mmi]

For all the BMR lovers on this thread: do you think there's any objective measurable data that could explain why the RAAL tweeters sound "magical" on some material?

I don't feel qualified to comment alongside Dennis who has obviously has vast amounts of specific experience, but I did trawl the entire interewbs looking for comments made by RAALs designer Aleksandar on this topic. I quoted some his comments on this ASR post, and below are a few more I had saved. From memory he discusses low level mechanical behaviour quite a lot, ie interactions on a materials level that will not show up in measurements.

I personally don't know why there is this assumption Spinoramas are the be all and end all. They obviously get part of the way there, but surely there is plenty they don't tell you. Whether what is lacking is important information or in the realm of being able to be described is another matter.

If you could model a speaker down to whatever low level physical properties and interactions might affect its performance, simulate it playing in various real environments, then look at the data from any point in 3d space at any point in time or over periods of time, then surely that would start to show you a much more complete picture.

Take for example a recording of a classical orchestra. Presenting the acoustics of a hall is an essential part of tricking a listener that he’s witnessing the real event. A dome tweeter will take 30 dB signal and show it as a starting point. Effectively, it will expand the dynamics downwards by presenting a strong signal as weak and lose the information. Acoustic decay of a hall will be shortened. Ribbons will not do that. They will steal a lot less, and ours are stealing the least of all ribbons out there.

Showing measurements of dynamics tracking (basically – how much information is lost) will allow us to compare speaker A to speaker B and it will tell you which is better in listening.

Do we have that nowadays? No, we don’t, not readily available. Will I go to great lengths to establish this procedure? Nope, not me! In order to effectively use digital measuring equipment, I guess one should create a pseudo-noise signal consisted of different information embedded on different discrete level steps, play the burst, then crunch the acquisition data to see how much information can be retrieved. It is not my field of expertize.

You can't say how fast is the mechanics by measuring impulse response (or derived FR, same thing) with a transformer.

It's not about efficiency at all. Low mass-low friction is a requirement for good sounding speakers in general, not just tweeters.

 

[Chromatischism]

The BMR actually has wider vertical dispersion than I remembered. But it is certainly restricted compared with a coaxial or a lot of other dome speakers. Counter-intuitively, however, the BMR actually throws a very tall sound stage. When switching to most other speakers, the sound stage seems to collapse inward and sound a little pinched in comparison. We have a long way to go in assessing the impact of differing patterns of vertical dispersion.

One has to first prove that the perception of vertical soundstage is related to vertical dispersion. I think at this point that is an assumption. For all we know, there could be an aspect of the horizontal causing that. There are a lot of oddities in psychoacoustics.

 

[Chromatischism]

I personally don't know why there is this assumption Spinoramas are the be all and end all. They obviously get part of the way there, but surely there is plenty they don't tell you. Whether what is lacking is important information or in the realm of being able to be described is another matter.

https://smile.amazon.com/Sound-Reproduction-Psychoacoustics-Loudspeakers-Engineering/dp/113892136X

I'm open to there being more to know. That's why we get up in the morning. But the current state of things is that there is a lot of evidence on one side and virtually none on the other. If humans can go to other moons and planets – endeavors which require an enormous array of measurements – surely they can measure speaker effects to the nth degree. Or, audiophiles are seriously overcomplicating this. Approach most issues in life in this way and you'll be on the right side of things more often than not. So side with the evidence, but be open to new evidence, as long as it's quality and is verified by others. So far, we don't have that.

I don't feel qualified to comment alongside Dennis who has obviously has vast amounts of specific experience, but I did trawl the entire interewbs looking for comments made by RAALs designer Aleksandar on this topic. I quoted some his comments on this ASR post, and below are a few more I had saved. From memory he discusses low level mechanical behaviour quite a lot, ie interactions on a materials level that will not show up in measurements.

I personally can't trust the statements of the RAAL designer simply because he has a product to sell and I don't know him nearly well enough to overcome that. Same goes for most audio creations that aren't 3rd party verified.

But let's look closer at this "dynamics tracking" idea. While seemingly reality-based, if there were anomalies there, they too would show up as ripples in a frequency response, distortion, or compression measurement. There, you are seeing how loud each frequency plays and how cleanly and faithfully it plays. What else is there? Further, if a speaker is going to behave a certain audible way during music playback, I'd bet it will behave the same way when put through the ringer of measurements. Otherwise, claims are essentially being made that a speaker performs differently when sending music signals through it yet it doesn't misbehave at all when signals are put through it on the test stand. That would be quite a stretch.

Further, if the RAAL were something special in this area, I'm not seeing it in the RAAL 64-10. Refer to this compression test where the "dynamics tracking" deviates from linearity approaching 90 dB and especially above that in the 2500-3500 Hz range:

Since it was mentioned: 3/4" dome tweeter using the same procedure about 6 weeks prior:

Distortion:

Clearly the larger woofer used in the BMR has the bass distortion under control, but the tweeter is another story.

How much of this is audible? I have no idea. I just wanted to expand a bit on this dynamics thing since it comes up now and again, but always seems shrouded in mystery.

Best regards.

 

[mmi]

But let's look closer at this "dynamics tracking" idea. While seemingly reality-based, if there were anomalies there, they too would show up as ripples in a frequency response, distortion, or compression measurement. There, you are seeing how loud each frequency plays and how cleanly and faithfully it plays.

But what does that tell you about micro detail? I understand you don’t trust the designers bias, but the information for why he designed it and what he believes differentiates it is out there and I don’t think anyone else will give you a clearer answer. Whether you believe him or not is up to you. See these posts:

Raal tweeters-are they worth it ? - Techtalk Speaker Building, Audio, Video Discussion Forum

Want a second or third opinion about your speaker cabinet design or other audio related problem? Post your question or comment on the Technical Discussion Board. Hundreds of technicians, engineers, and hobbyists, nationwide read and discuss electronics related questions each week. We welcome...

techtalk.parts-express.com

https://www.avsforum.com/threads/raal-tweeters.3075988/post-58461890

https://www.avsforum.com/threads/2-0-bookshelf-compared-wharfedale-philharmonic-chane-musichall-elac-energy-kef.2233954/page-39#post-46526969

 

[Chromatischism]

But what does that tell you about micro detail?

I'm not sure. Does "micro detail" have a definition? Or is this another audiophile theory? Can someone pick it out in a blind test?

I've followed RAAL discussions on AVS for years. I never really felt like they got to the bottom of anything.

 

[mmi]

I'm not sure. Does "micro detail" have a definition? Or is this another audiophile theory? Can someone pick it out in a blind test?

I've followed RAAL discussions on AVS for years. I never really felt like they got to the bottom of anything.

I feel he has been rather clear. Within their optimal range his products reproduce low level signals that domes can’t (very soft signals > 30db down) and stop and start in a way domes can’t. The former won’t show in measurements, the latter is partly proven by spectral decay plots (I think?), and according to him both are audible.

I’ve got no skin in the game, just find his comments interesting. As someone with more knowledge maybe you could explain your thoughts on detail and if it is measurable? It does seem this is the thing the maker says distinguishes it.

I did manage to finally hear a Raal yesterday which is what piqued my interest in this post. I was auditioning Kef R3s and the dealer also had the Serhan and Swift Mu2 Mk2 and a prototype BA2.

Listening conditions were all over the place in terms of distance and level, my extremely unreliable subjective impression was:

R3 sounded nice and clean and the coaxial was interesting in terms of sound not changing so much with height, but bass seemed rolled off or a bit thinner that I was hoping. I was further from other speakers tested, which may explain it. I am also not really after them I just wanted to hear them.

Mu2 Mk2 was a great little bookshelf that I could happily live with if I had far more money than I do and wanted a small bookshelf. I believe it would measure well.

Regarding the BA2 with Raal it sounded great, very clear and cohesive and I think I get what people say about the tops being smooth. What interested me, and this was probably due to seating which was only 1.5-2m, was the stereo effect in that range was very head in a vice in that the sound became very directional from one speaker with slight head movements. I was hoping for a more holographic effect with a phantom center that stuck in place as I moved around, although I was probably too close and it was impossible to test further back. Also the vertical response drops off very quickly as you’d imagine from the measurements.

 

[pjug]

I noticed the Salk site is now showing the newer BMR Monitor with the ceramic woofer. Also looks like a front slot port. But then there are still photos of the old BMR as well. Is there a "standard" current version from Salk or are the driver choice, port, offset tweeter, etc. all up to the customer?

@jsalk and @Dennis Murphy I thought I'd ask here instead of email since others may also be wondering.

 

[Dennis Murphy]

I noticed the Salk site is now showing the newer BMR Monitor with the ceramic woofer. Also looks like a front slot port. But then there are still photos of the old BMR as well. Is there a "standard" current version from Salk or are the driver choice, port, offset tweeter, etc. all up to the customer?

@jsalk and @Dennis Murphy I thought I'd ask here instead of email since others may also be wondering.

Jim can make either model, and with a slotted port or a round rear port. That's about it. I've never claimed the new version was "better" than the previous one, just a little different. For people wanting the highest possible playback levels in the bass, the previous version with the Scan is probably a better choice. For people who want greater sensitivity and a slightly smoother midrange, the current version is preferable.

 

[Chromatischism]

I feel he has been rather clear. Within their optimal range his products reproduce low level signals that domes can’t (very soft signals > 30db down) and stop and start in a way domes can’t. The former won’t show in measurements, the latter is partly proven by spectral decay plots (I think?), and according to him both are audible.

I would be skeptical about all of this, especially the bolded part. If someone wants to tell me my speakers stop making sound if they are turned down lower than the RAAL because they "can't reproduce quiet signals" I would laugh them out of the room. My AVR works relative to THX reference level, and the range goes down to -80. I can still hear them at that level. It is not a level that anyone would ever use - it is barely a whisper. That's low enough for me!

Additionally, I know the difference between 100 dB and 70 dB. Both are clearly heard. For -30 dB to not be heard, it would have to be well below the noise floor of the room. The test would then be to play both speakers at something like 50 dB and play content that has both full scale signals and some at -30. You could guess the result: you would lose the -30 information from both speakers in most rooms. Floyd Toole compiled research on this showing noise floors and hearing thresholds.

 

[mmi]

Additionally, I know the difference between 100 dB and 70 dB. Both are clearly heard. For -30 dB to not be heard, it would have to be well below the noise floor of the room. The test would then be to play both speakers at something like 50 dB and play content that has both full scale signals and some at -30. You could guess the result: you would lose the -30 information from both speakers in most rooms. Floyd Toole compiled research on this showing noise floors and hearing thresholds.

This makes sense, testing would obviously be the best thing to do. In the interests of clarity, here is a quote I am referencing I am not sure if this means something slightly different to what I said above:

Tweeters operate about 10-20dB lower than mids, so when listening at 90 dB, highs are 10-20dB lower. If you expect good dynamic range and audibility of low level detail, the tweeter should not ignore signals that would play at 20-30dB of SPL. Yes, the ambient noise is higher, but music is not noise and it will get distinguished from the noise...

And CSD plots of "140-15D, before updates, that include changes in Aluminum foil (2009) and transformer (2012)", which I believe provides data illustrating this supposed characteristic. I am just playing devils advocate here btw, I was super interested in Raal's because of the wide dispersion – I want room filling sound, I'm not a sit and listen type – and the fact I collect Afro/Latin/Caribbean music with lots of fast guitar and brass... anything that tames the harshness a bit seems good to me and Dennis has mentioned quite a few times how Raal's tame sibilance in comparison to some domes.

 

[Chromatischism]

Tweeters operate about 10-20dB lower than mids, so when listening at 90 dB, highs are 10-20dB lower.

Is he referring to an average of musical content?

 

[mmi]

Is he referring to an average of musical content?

Absolutely no idea sorry. Regarding testing such a thing, I unrelatedly stumbled on this which seems at least tangentially related:

The Audibility of Intermodulation Distortion

In this blog post I compare a driver's intermodulation distortion (IMD) against the spectral content of music. Unfortunately there is not a great wealth of study data to support the audibility of IMD. However we can first begin to ask some other questions relating to it's impact on the music...

josephcrowe.com

 

[mj30250]

It's strange how it's seemingly so difficult to reach any objective conclusion that would settle the dome vs RAAL debate.

I used Ascend Sierra RAAL Towers in my main setup for a while (apologies as this is a BMR thread) until conducting a comparison and swapping them out in favor of Revel F226Bes in December of last year. I recently moved the Sierra towers back into place (after listening to nothing but the Revels in this setup since that time) and conducted another comparison. It was remarkable how immediately the RAALs made their presence known. The custom 70-20XR ribbons used in the Ascends simply do some things differently than any dome I've heard. In comparison to the Revel's Be tweeter and waveguide, horizontal dispersion is relatively wide for both and a reasonably close call, with the Ascends running a bit wider before narrowing at around 7kHz. Vertical dispersion is much broader on the Revels, which is clearly heard when standing up and listening above the tweeter axis. But on-axis, with certain program material, the RAALs are simply more "present" in the room, and can truly sound like a live instrument in ways that I haven't heard from the Revels (or other dome speakers). It can't simply be laid at the feet of a treble rise that would show up in the spins, as it would in a typical "bright" versus neutral speaker comparison. I could throw level matching to the winds, crank up the Revels to well beyond the Sierra's output, and much of the differences would remain.

For me, the mark of a good speaker is one that doesn't sound like a speaker. Within the higher frequencies, and for program material that is well-suited to reveal the differences, the RAAL ribbons simply sound less "speaker-like" than the Revel domes. And no, I don't have any personal double-blind test results to share that would support my claim. But in this case, I find the differences to be so readily apparent as to render blind testing totally unnecessary to prove their existence, just as it would be unnecessary to prove that there are differences in the flavor of apple sauce and ranch dressing. Blind testing for preference, of course, would be an entirely different situation.

 

[Chromatischism]

It's strange how it's seemingly so difficult to reach any objective conclusion that would settle the dome vs RAAL debate.

Thanks for sharing your experience. I'd love to hear both of those speakers.

I'll just add what one of the most reputable audio researchers has to say on the subject:

The "quick decay" you speak of is totally predictable from amplitude vs. frequency responses because transducers are minimum-phase devices. Impulse response plots are impressive, but the reality is that humans do not respond to phase shift so these time-domain plots are misleading. We humans do not hear waveforms. I am an engineer and had to learn this myself, fortunately at an early stage.

It is interesting that one of the first loudspeakers I tested in the anechoic chamber at the NRCC in 1967 (52 years ago!!!!) was a ribbon tweeter, the Kelly Ribbon from the UK. I just looked at the measurements in my personal archive. At the time it was promoted for the same reasons that ribbons and electrostatic loudspeakers are today: "massless" diaphragms, "Instant" transient response, etc. etc. It was a learning experience for me, and only definitively provable in double-blind listening tests. Of course, nothing back then was as good as things are now, but the implied superiority simply was not heard. As time passed and measurements and knowledge improved, nothing has changed. There are good loudspeakers and not-so-good loudspeakers, and the method of moving the air has not revealed itself as being the dominant factor. If any one method was obviously superior, it would dominate the products we can buy.

As far as the "massless" consideration is concerned, I have a Tesla S P90D in my garage that accelerates from 0-60 mph in 3.2 s. It is a heavy four door, potentially 7-passenger, sedan that is much quicker than most two seat sports cars - and I have owned a few. The secret is in the motor, and that is also the relevant factor in loudspeaker transducers. Ribbons and electrostatic speakers typically have relatively weak motors compared to what can be put behind a cone or dome. In the end, frequency response is king.

I really do think we're looking at frequency response and dispersion patterns and not anything magical. If only someone could engineer a "dome" with the same pattern to test.

 

[mj30250]

Consider what one of the most reputable audio researchers has to say on the subject:

To address one of Dr. Toole's points, I would venture to guess that a couple potential reasons for RAAL ribbons not having taken over the marketplace is A) their comparative expense versus most non-exotic domes (particularly the larger ones), and B) their narrow vertical dispersion, with the latter likely to be lacking in showroom-friendliness. Whatever science or "magic" might be responsible for their positive feedback, there's no question that you need to be nearly locked into vertical alignment with the RAAL tweeter to hear it at its best. That's probably not conducive to someone wandering through a store while listening to several speakers.

Beyond that, I don't doubt that the remarks relating to phase shifts, transient response, etc, are valid - but again, it then begs the question - so what is it? Is it simply the implementation of a good speaker design and crossover, and not much of anything to do with the so-called massless advantage of true ribbons? If so, why are domes so challenged to get there?