Philharmonic Audio BMR Speaker Discussion

[ROOSKIE]

Every time I look at these I really wish the woofer didn't look like that, lol. It's almost made worse by how perfect those Corian cabinets look.

Go figure I like the look. I have always liked the look of those woofers, really speaks to the material involved. Very cool to me.

 

[stren]

Looking forward to seeing the purifi results

 

[DeruDog]

I use a vertical BMR as the center speaker. At the time this could be ordered done by Salk with a front port.
If this fits your layout you can ask Dennis Murphy for the plans of the speaker cabinet.

When it's vertical, do you place it under your screen? If I had a projector and an acoustically transparent screen that would be ideal. If it is under your screen do you have any problem with the acoustic location being so much lower than the screen?

Thanks for the not on the cabinet. I will ask Dennis if he can send those along after I order the speakers. Probably will be a month or two before this makes the top of my list.

 

[bogart]

When it's vertical, do you place it under your screen? If I had a projector and an acoustically transparent screen that would be ideal. If it is under your screen do you have any problem with the acoustic location being so much lower than the screen?

I struggle with this as well. Today I have a plain ol' MTM oriented horizontally under a projection screen, fairly low. I'm sure I'm getting sub-optimal horizontal dispersion, but I'm also pretty sure I'm worse off if I try to get it vertical and have to hit the precise angle and starting down so low. If only I had sprung for that acoustically transparent screen!

 

[stren]

BTW any thoughts on the purifi 4" driver - seems like a preview on the website is up but with little real data. Wondering if there's any reason to suspect it might be an upgrade to the current mid unit.

 

[bogart]

Thanks very much for starting this thread Bogart. I hope it will provide some useful and polite correspondence. I think that, if nothing else, my design raises interesting issues. A full reply to all of the points raised so far would would require to much space and effort right now, so I would just like to make some bullet points.

@Dennis Murphy thanks for joining in the conversation! It's a rare privilege to get to talk with someone with your level of knowledge and experience about their work. It's definitely interesting to get a peek at what's down the road and what's exciting for you as look ahead. Would you consider the design as superseded by those potential changes or would it be a "variant" of the base edition?

Maybe saying the same thing differently, are the potential changes a way to more fully realize your design goals, or effectively a performance bonus?

 

[Dennis Murphy]

BTW any thoughts on the purifi 4" driver - seems like a preview on the website is up but with little real data. Wondering if there's any reason to suspect it might be an upgrade to the current mid unit.

The 4" Purifi would be too large for the BMR mid. The whole design goal is to maximize and even out dispersion across the audio spectrum, hence the use of the BMR midrange. It might make more sense in a small center channel.

 

[Dennis Murphy]

@Dennis Murphy thanks for joining in the conversation! It's a rare privilege to get to talk with someone with your level of knowledge and experience about their work. It's definitely interesting to get a peek at what's down the road and what's exciting for you as look ahead. Would you consider the design as superseded by those potential changes or would it be a "variant" of the base edition?

Maybe saying the same thing differently, are the potential changes a way to more fully realize your design goals, or effectively a performance bonus?

A Purifi version would just be an upgrade option. I don't have any plans to continue with the Scan woofer now that the SB Ceramic is available.

 

[Zvu]

Weaker motor, smaller voice coil, lower Sd and lower linear excursion with SB17CAC in comparison to ScanSpeak 18W8545-01

Not much of a fair replacement.

 

[Dennis Murphy]

Weaker motor, smaller voice coil, lower Sd and lower linear excursion with SB17CAC in comparison to ScanSpeak 18W8545-01

Not much of a fair replacement.

There are pluses and minuses to both woofers. As far as bass reach, they're identical from 32 Hz on up. I took very careful TS measurements after the Ceramic was completely broken in, and Paul Kittinger's modeling and my testing showed no significant differences, although the Scan probably has slightly better power handling, particularly when it decouples below the tuning point. On the other hand, the Scan is very rough from 900 Hz on up and you have to use a 4th order slope at no higher than 600 Hz to get a linear system response. The Ceramic is dead smooth out to 2 kHz, and by crossing second order a little higher up, I got system sensitivity up by about 1.5 dB due to bandpass gain in the midrange. The Ceramic is also a good bit cheaper at the Port of Entry in China, and I'm trying to make the BMR's as affordable as possible. Finally, it looks like the Purifi will be a significant improvement over both woofers, and those wanting the ultimate bass response and are willing and able to pay for it will be able to get it in the Purifi version.

 

[goldark]

There are pluses and minuses to both woofers. As far as bass reach, they're identical from 32 Hz on up. I took very careful TS measurements after the Ceramic was completely broken in, and Paul Kittinger's modeling and my testing showed no significant differences, although the Scan probably has slightly better power handling, particularly when it decouples below the tuning point. On the other hand, the Scan is very rough from 900 Hz on up and you have to use a 4th order slope at no higher than 600 Hz to get a linear system response. The Ceramic is dead smooth out to 2 kHz, and by crossing second order a little higher up, I got system sensitivity up by about 1.5 dB due to bandpass gain in the midrange. The Ceramic is also a good bit cheaper at the Port of Entry in China, and I'm trying to make the BMR's as affordable as possible. Finally, it looks like the Purifi will be a significant improvement over both woofers, and those wanting the ultimate bass response and are willing and able to pay for it will be able to get it in the Purifi version.

Dennis, will the Chinese BMR's come in kits or finished speaker systems with no need for DIY?

 

[Zvu]

Since you succesfully solved the problem of ScanSpeak roughness i'll assume that it actually isn't a problem but just needs a different type of solution.

.... The Ceramic is dead smooth out to 2 kHz, and by crossing second order a little higher up, I got system sensitivity up by about 1.5 dB due to bandpass gain in the midrange...

How did you manage to achieve this ? If the crossover is over 600Hz, which would be absolute minimum for BMR given the distortion measurements, and you've made full baffle step compensation - the only option would be that SB17CAC is more sensitive. That is possible only if you use 4 ohm version. How is sensitivity at say 200Hz and its relation to F3 and F6 related to midrange bandpass gain ?

 

[Dennis Murphy]

Dennis, will the Chinese BMR's come in kits or finished speaker systems with no need for DIY?

They'll be real speakers with some very nice veneered cabinets. No need to break out the soldering iron or router.

 

[Dennis Murphy]

Since you succesfully solved the problem of ScanSpeak roughness i'll assume that it actually isn't a problem but just needs a different type of solution.



How did you manage to achieve this ? If the crossover is over 600Hz, which would be absolute minimum for BMR given the distortion measurements, and you've made full baffle step compensation - the only option would be that SB17CAC is more sensitive. That is possible only if you use 4 ohm version. How is sensitivity at say 200Hz and its relation to F3 and F6 related to midrange bandpass gain ?

I used the 4 ohm version. It was tricky keeping the system impedance up, but it's a very easy load from a phase angle standpoint.

 

[Zvu]

Thank you for clarification about sensitivity shift Mr Murphy.

I consider BMR Philharmonitor with 18W one of the nicest loudspeakers of that format and philosophy available. It will be exciting to see how will 17CAC and Purifi versions measure.

 

[ob1]

Hi everyone, please accept my apologies for I'm far from being technically versed and my English skills are deficient. Yet, I felt I can have a very modest contribution, since I am the lucky owner of a pair of BMR in Salk maple finish. I have owned them for about 2 years and couldn't be happier.
I am afraid I cannot shed any light in your particular application, I am using them in an open living room of roughly 19X19ft (that is about 6.33mX6.33m) in a stereo set-up.

What I wanted to highlight was that my particular pair, which I believe was assembled by Jim Salk is very tightly matched. I am using them with Acourate room correction, but still regularly listen to them uncorrected depending on source. Once correction is applied, Acourate evaluates IACC, interaural-cross-correlation, at different time intervals. At 10 ms, I have reached about 97.0% IACC, which to the best of my knowledge, is a testament to how closely each speaker is matched to its sibling. Given that some anomalies are due to the room and may not be fully corrected by Acourate, I tend to believe it is a testament to great care in matching the speakers. What is for sure is I have not had any speakers I have personally tested that reached such a high value (amongst Sonus Faber Cremona auditor, PSB X2T, PSB B5 and a few others I may have forgotten).

Long story short, I am glad I have opted to have them built professionally. Just to make it clear, the following pic is not mine, it was taken from
http://gp-architecte.com/project/amo/

Sorry for this long post, but I wanted to share how satisfied I was with my purchase, Dennis is a true gentleman. If it weren't for audiosciencereview that pointed me towards Dr. Toole's book, I wouldn't probably have even considered those speakers. Thank you all guys!

 

[DDF]

On the other hand, the Scan is very rough from 900 Hz on up and you have to use a 4th order slope at no higher than 600 Hz to get a linear system response.

Na, gotta take care of the edge surround resonance, but in the right cabinet it can be made nice and flat even off axis.

Here's my Scan 8545 (sealed) and Usher 9950 from many years ago. Some smoothing in this from the FFT, but its still a decent 5.5 ms window.

I used staggered crossover points and shapes approximating acoustic butterworth third order. Great for controlling tweeter off axis bloom.

Orange is inverse null. Full null hits at +15 degree vertical

 

[Dennis Murphy]

I've done a couple of 2-ways with the 8545 and was able to deal with the surround-cone resonance fairly well with a trap circuit using 4th order slopes. But my objective with the SB BMR was to achieve a nearly perfect 2nd order acoustic roll off as far out as possible in order to boost sensitivity. It's a lead pipe cinch to do that with the SB Ceramic. I've attached the reverse null simulation at 3 meters--the 2nd order slope is maintained on out to over 4000 Hz, which is far enough to produce almost perfect phase tracking and get the sensitivity up. The horizontal off axis system response is very smooth even at 80 degrees. I might have been able to do fairly well with the Scan with enough components, but the Ceramic only takes one inductor, a damping resistor, and a cap.

 

[Xyrium]

Every time I look at these I really wish the woofer didn't look like that, lol. It's almost made worse by how perfect those Corian cabinets look.

You guys are crazy, I love the look of that melted obsidian woofer (MInecraft reference, my 6yo assures me).

 

[617]

I've done a couple of 2-ways with the 8545 and was able to deal with the surround-cone resonance fairly well with a trap circuit using 4th order slopes. But my objective with the SB BMR was to achieve a nearly perfect 2nd order acoustic roll off as far out as possible in order to boost sensitivity. It's a lead pipe cinch to do that with the SB Ceramic. I've attached the reverse null simulation at 3 meters--the 2nd order slope is maintained on out to over 4000 Hz, which is far enough to produce almost perfect phase tracking and get the sensitivity up. The horizontal off axis system response is very smooth even at 80 degrees. I might have been able to do fairly well with the Scan with enough components, but the Ceramic only takes one inductor, a damping resistor, and a cap.

I didn't realize you were using such a shallow slope on the BMR up so high, that's very interesting. Do you have any issues matching the dispersion of the 8545 and the BMR at 900hz? Or does the shallow slope take care of that?