Philharmonic BMR Speaker Review

[ctrl]

Do you know why at around 600 Hz the dispersion start to get narrower?

This could be the influence of the rear speaker cabinet edge. But to be sure I would have to do another simulation with different depths of the loudspeaker cabinet.

Why is the combined response at 3k Hz is actually a small dip rather than a peak?

The Phil-SPL diagram is not normalized to the axis frequency response, so you can see the influence of the edge diffraction on it.
If the frequency response is not made as flat as possible by force, the dip in the axis frequency response partially compensates for the humps under the angular frequency responses.

Also may I ask what is the software you used?

The program is called ABEC, the current version is called AKABAK3 and is also available in a free, restricted version.
http://www.randteam.de/AKABAK3/Index.html

 

[hardisj]

3) Question for hardisj. I'm sure this has been explained somewhere sometime, but I'm still very confused about how the nearfield Klippel measurements get translated into one meter or far field response. I know there's lots of math involved and I'm not expecting you to go into that. But are the curves you're showing what Klippel is predicting the one-meter response will be? And can you ask Klippel to give you the predicted response at virtually any distance, like the 3-meter distance I optimized the BMR for? Anyhow, thanks very much for your contribution. I'll ask Santa to stick a Klippel machine in my Xmas stocking. Ho Ho.

Before Klippel invented the Near Field Scanner (NFS), "Klippel" was a reference to any number of products provided by them but typically it meant the Distortion Analyzer and the LSI module because people associated Klippel with linear xmax measurements, mostly.

Now that Klippel has the NFS, "Klippel" means different things to different folks. So, let me clarify what I have:

I am *not* using the NFS. I am using the Distortion Analyzer 2 (a rack mount piece of hardware) along with various modules, depending on what I am measuring. For example, their TRF module is used to measure frequency response. DIS is for intermod, harmonic and compression testing using log-spaced tones, one at a time (or two at a time for intermod). LPM would be for T/S. LSI would be for linear xmax. Etc, etc.. I do not perform any near field measurements for frequency response (other than to try to isolate the individual drive units so I can understand breakup, port resonance, etc). But, all of my FR measurements are based on two measurements: an indoor 4-pi measurement and an outdoor ground plane measurement. Each of these are a set, used in conjunction with Klippel's ISC module which then allows me the ability to create a room correction filter and achieve anechoic measurements from an indoor measurement. The drawback is, I have to conduct each angle's measurement twice (the indoor and outdoor measurements I just mentioned) because no two speakers are the same in how they "light up" the room and each angle needs its own room correction filter. It takes hours and hours doing this because it is all manual. I literally, *literally* walk about 2 miles round-trip to conduct this full set of spin measurements.


Anyway, I believe the answer you were looking for from me is: I don't have the NFS so I don't know the science behind how it extrapolates the nearfield measurements to "project" in to the farfield. There is a thread here about it, though. https://www.audiosciencereview.com/...nderstanding-how-the-klippel-nfs-works.13139/


If you want to read about the various modules, here's a link:
https://www.klippel.de/products/rd-system.html

 

[Dennis Murphy]

@ctrl Wow, very nice work, thank you for doing this. Now I see why the 3k Hz and 6 to 7k Hz are dffraction. Your simulation is very close to the real speaker measured. Do you know why at around 600 Hz the dispersion start to get narrower? Why is the combined response at 3k Hz is actually a small dip rather than a peak? Also may I ask what is the software you used?

Here is a small analysis why the radiation of the loudspeaker looks like what it looks like.

I have simulated a very simple model of the loudspeaker. For this purpose the ideally behaving driver cones were simply placed flat on the baffle, the dimensions of the drivers should be roughly correct - the ribbon tweeter is 1cm too short (had measured wrong), but this should only have a vertical effect.
To save computing time, a depth of only 20cm was set for the loudspeaker cabinet - thus the simulation to low frequencies (<600-800Hz) is not quite correct. At about 10Khz the simulation is also no longer reliable (again to save computing time).

View attachment 74242

First we look at the horizontal normalized frequency response of the midrange driver - which in the Phil BMR has its crossover frequency at 3kHz.
It is clearly to see that the midrange driver radiates somewhat narrower between 1-2kHz and in the range 2-4kHz it radiates much wider due to the edge diffraction (interaction with the baffle) - related to the normalized 0° frequency response.
View attachment 74243

If we only look at the midrange driver, a crossover frequency of 2kHz would be appropriate to avoid broadening in the radiation. But of course we also have to look at the radiation pattern of the tweeter - again normalized to the 0° frequency response:
View attachment 74244

You can immediately see that the edge diffraction is more dramatic for the tweeter. Even between 5-8kHz the edge diffraction is still clearly noticeable.
So of course it makes no sense to choose the crossover frequency as low as possible e. g. 2kHz (even if the ribbon tweeter would be able to do so), because otherwise the effect of edge diffraction would be even more pronounced.

Let's put it all together and look at what the simulation predicts at a crossover frequency of 3kHz with LR4:
View attachment 74245

This results for the horizontal radiation of the loudspeaker normalized to 0°:
View attachment 74246

It is easy to see, for example, that the 60° frequency response increases steadily in sound pressure from 1.5kHz onwards and that from 2.3kHz onwards it has a higher sound pressure than the midrange.
In order that the loudspeaker does not sound too bright at a short distance from a side wall, the axis frequency response would have to be corrected accordingly to compensate for the increase at the different angles.



I don't think I made myself clear.

The dispersion is very even, but at an angle the sound pressure of the tweeter is up to 70° clearly above that of the midrange, which could lead to the said bright sound at a small distance to a side wall, since the LW and axis frequency response are rather flat.

In large rooms and at normal volume this tuning ensures a high level of detail - it's always a compromise.

Glad to see this review has stimulated so many thoughtful posts. I did do some simulations myself using the late Jeff Bagby's diffraction software, and that's why I tried to offset the issue at least somewhat with the on-axis dip. Just for the record, the crossover point is 3400 Hz, And, as I just posted before I saw your post, I will be offering a curved cabinet that eliminates most of the problem. (We went with a more attractive veneer than this)

 

[MZKM]

It's interesting that someone posted about the possible meritorious effects of using a curved cabinet that bowed out on the sides and would therefore in effect create a much wider round over and reduced off-axis diffraction. We ordered a test cabinet with that shape a few weeks ago, and it just arrived yesterday. I took some measurements using the current BMR crossover, and there were absolutely no peaks or dips off axis. We'll offer that version as an option early next year.

That was theory, glad to know it is actually of merit. It would be interesting to see how much of a difference it acrually is.

 

[Dennis Murphy]

Before Klippel invented the Near Field Scanner (NFS), "Klippel" was a reference to any number of products provided by them but typically it meant the Distortion Analyzer and the LSI module because people associated Klippel with linear xmax measurements, mostly.

Now that Klippel has the NFS, "Klippel" means different things to different folks. So, let me clarify what I have:

I am *not* using the NFS. I am using the Distortion Analyzer 2 (a rack mount piece of hardware) along with various modules, depending on what I am measuring. For example, their TRF module is used to measure frequency response. DIS is for intermod, harmonic and compression testing using log-spaced tones, one at a time (or two at a time for intermod). LPM would be for T/S. LSI would be for linear xmax. Etc, etc.. I do not perform any near field measurements for frequency response (other than to try to isolate the individual drive units so I can understand breakup, port resonance, etc). But, all of my FR measurements are based on two measurements: an indoor 4-pi measurement and an outdoor ground plane measurement. Each of these are a set, used in conjunction with Klippel's ISC module which then allows me the ability to create a room correction filter and achieve anechoic measurements from an indoor measurement. The drawback is, I have to conduct each angle's measurement twice (the indoor and outdoor measurements I just mentioned) because no two speakers are the same in how they "light up" the room and each angle needs its own room correction filter. It takes hours and hours doing this because it is all manual. I literally, *literally* walk about 2 miles round-trip to conduct this full set of spin measurements.


Anyway, I believe the answer you were looking for from me is: I don't have the NFS so I don't know the science behind how it extrapolates the nearfield measurements to "project" in to the farfield. There is a thread here about it, though. https://www.audiosciencereview.com/...nderstanding-how-the-klippel-nfs-works.13139/


If you want to read about the various modules, here's a link:
https://www.klippel.de/products/rd-system.html

Thanks very much. I'm glad I didn't pay you by the hour (or footstep) for the review. So, what is the measuring distance for, say, the listening window?

 

[Dennis Murphy]

That was theory, glad to know it is actually of merit. It would be interesting to see how much of a difference it acrually is.

Well, I can measure that for you tomorrow. it won't be a perfect test one-on-one test because I'll be comparing a rectangular BMR with the Scan woof with a curved cabinet with the new SB Acoustics woofer, but at the very least I think I can show that the far-off axis plot for the curved is better than for the rectangular.

 

[thebabyparrot]

That directivity is absolutely gargantuan. I really wonder how that effects imaging. I imagine soundstage will be excellent. This sounds like a speaker version of the Sennheiser Hd800

 

[LightninBoy]

That directivity is absolutely gargantuan.

 

[GelbeMusik]

I can honestly say I don't agree with anything you've said. "The curved sidewalls are inacceptable design-wise"?? The distortion, whether perceptbile or not, must not be" ??? Don't get me started. But for the record, the tweeter is not the most expensive driver. It still won't be when I replace the 8545 woofer with the SB Acoustics Ceramic. I'm using this particular RAAL because it provides the kind of sound I like. And it does that because of its broad dispersion and flat and extended response. I've done a version with the much more expensive 70-10, and I couldn't hear or measure any advantage. I've done everything I can think of to keep the price of the BMR down without sacrificing performance. if you can build a speaker that sounds as good, goes as deep, and can be sold for less, I urge you to join the fray. (But I hope you have $1M in the bank to cover losses )

Dennis, of course You defend Your product. And for the sake of Your right to do so I won't go into an argument. As far as I understood Your response You would anyway emphasize Your and others subjective impression, which actually is not my field. I cannot fill the gap between the objective data and the highlighted statement above. Nope, any 19mm dome would do better, but that is it from my side.



Btw, Your commercial interest shines through a bit. That's o/k with me.

 

[thebabyparrot]

Glad to see this review has stimulated so many thoughtful posts. I did do some simulations myself using the late Jeff Bagby's diffraction software, and that's why I tried to offset the issue at least somewhat with the on-axis dip. Just for the record, the crossover point is 3400 Hz, And, as I just posted before I saw your post, I will be offering a curved cabinet that eliminates most of the problem. (We went with a more attractive veneer than this)View attachment 74252

Will this be via the Taiwanese variant set to launch later this year? or is this a Salk model?

 

[ctrl]

Just for the record, the crossover point is 3400 Hz,

Sorry, I wasn't paying attention. But it makes very little difference in the simulation.

I will be offering a curved cabinet that eliminates most of the problem.

This should not eliminate the main problem in the horizontal radiation, because the front baffle would have to be modified.

A rounded baffle placed close to the tweeter and midrange and the woofer in B&W style would optimize radiation. Then the horizontal radiation would be....

...absolutely gargantuan.

Simulation with [email protected] horizontal normalised deg0-90

Due to the "virtually" narrower baffle, the edge diffraction shifts to higher frequencies and due to the lateral rounding the effect is less dramatic and more even (around 5kHz).

The less advantageous vertical dispersion remains unchanged - vertically wide radiating midrange driver with narrow radiating tweeter leads to a " step change " in the vertical dispersion.
Simulation with [email protected] vertical normalised deg0-90 (negative angles show the radiation upwards)

 

[thebabyparrot]

I guess there has to be some compromise made if their is an insistence not to use a waveguide.

 

[GelbeMusik]

It does adress it, because the question has no single number answer, as masking is frequency dependant, which means H2 and H3 don't have the same audibility limit.

I gave a valid (!) method for DIY'ing that sought after investigation. It is added to the TANNOY thread. No response so far. Seems to be an US American thing to just ignore. I was told so, sorry.

( => https://www.audiosciencereview.com/...-xt-6-speaker-review.14662/page-7#post-455717 )

But does it make sense waving with AES "papers", maybe 60y old, showing only some graphs, and then calculating numbers to a fraction of a percent for a miss or hit verdict? Please do that self-evaluation I recommended, it is easy. I developed the method during a short lunch break. It shouldn't need more than 10 minutes to get some motivating results.

 

[overg]

That directivity is absolutely gargantuan. I really wonder how that effects imaging. I imagine soundstage will be excellent. This sounds like a speaker version of the Sennheiser Hd800

In my experience, the production of my music has far, far, far more influence on imaging than my BMRs. Put on some Pink Floyd, and every instrument and vocal is going to be locked in its own unique location in the soundstage. On the flip side, something like Fugazi is going to essentially be a wall of sound, with the guitars especially sounding like they're coming from almost everywhere in front of me.

I suspect an accurate but narrower dispersion speaker would likely give me even more pinpoint imaging on the good stuff, but in my judgment, the BMRs are within the "margin of error" for realistic imaging. The "images" might be bigger than some other speakers, but not so big that they destroy my ability to close my eyes and imagine a realistic looking soundstage.

 

[GelbeMusik]

In my experience, the production of my music has far, far, far more influence on imaging than my BMRs.

Fugazi, good stuff. The production is as good as the content. Very strange feeling of some unique space in between, which underlines the perfect timing of the musicians.

My experience with wide dispersion speakers is tainted by more than a decade of listening using a CD / waveguide design. I felt, with another experimental wide dispersion alternative, the soundstage, the whole stereo magic was more relaxed, more forgiving. Deep space, if only a bit artificial. A new stereo experience. But I decided to stick to the CD, while giving up exactly that pin point location of phantom sources. I can't stand sitting there like a lifeless puppet. Double mono is enough for me.

Besides that general considerations, could the BMR considered basically different compared to a standard design, say 3-way 8" / 4" / 0,75" with a regular drivers? I doubt that. A tiny bit more here, but less there, just another compromise, right? I even argue that all the dispersion talk is an aftermath to the subjectively motivated choice of the ribbon as such. But lets see how far we get with that. Maybe there is something ;-)

 

[hardisj]

Thanks very much. I'm glad I didn't pay you by the hour (or footstep) for the review. So, what is the measuring distance for, say, the listening window?

*Most* of my measurements are made at 2 meters ground plane and 1 meter 4-pi. The listening window is an average of ±30° horizontally and ±10° vertically.

If I have a tall loudspeaker that requires a further distance to be "far field" then I will measure that way. I have a very large floorstanding speaker due sometime this month (hopefully) that I plan to measure at 4m/2m (groundplane, 4-pi).

 

[ctrl]

Besides that general considerations, could the BMR considered basically different compared to a standard design, say 3-way 8" / 4" / 0,75" with a regular drivers? I doubt that. A tiny bit more here, but less there, just another compromise, right? I even argue that all the dispersion talk is an aftermath to the subjectively motivated choice of the ribbon as such.

It's only that simple if you ignore details.

A 0.75'' tweeter would certainly improve the vertical dispersion, but completely ignores the unusual characteristics in the horizontal dispersion - whether one likes it or not.

From 4-10kHz the frequency response under angles up to 60° deviates less than -3dB from the axis frequency response. I don't know of any 0.75'' tweeter that can do this - even a Scan Speak 2010-851100 is far away from this.
A real alternative would be to maintain this behavior while improving the vertical radiation.

 

[ribosradagast]

You can watch a demonstration of this testing via my YouTube channel:

Goodness gracious, those test tones sound horrible. Hope for your family's sake your garage is detached from the rest of the house...

...also, obligatory comment about how the pink bike improves room acoustics

 

[GelbeMusik]

It's only that simple if you ignore details.
A 0.75'' tweeter would certainly improve the vertical dispersion, but completely ignores the unusual characteristics in the horizontal dispersion ...

Ja, these infamous details. I don't ignore them. I only do not want to discuss the whole design in total. There is a gross problem with the ribbon. Reiterated, I only feel that a lot of the talk regarding something special is an aftermath to a choice that was originally due to some other criteria.

If You and others don't see how and by far it gets a bit off at around 3-4kHz (actually and really the most sensitive frequencies for the human hearing, by the way), and so under different aspects, I couldn't tell either. So, I won't tell ;-)

@Dennis, I liked it more with straight sidewalls

 

[hardisj]

Goodness gracious, those test tones sound horrible. Hope for your family's sake your garage is detached from the rest of the house...

...also, obligatory comment about how the pink bike improves room acoustics

It's not. I wish it were. When it gets in to the 90dB+ region it begins to become a real annoyance.

That pink bike flies.