New Philharmonic BMR HT Towers

[Dennis Murphy]

Yes the zebra wood finish is nice and all but HT needs a low lustre matte/flat black finish option too. Glare = bad.

Looking back a few posts, you might have mistaken the zebra wood for the ebony, which is what's shown in the posted pic. I'm not sure. But the zebra wood is really a flat finish. There would be no glare.

 

[chych7]

Looking back a few posts, you might have mistaken the zebra wood for the ebony, which is what's shown in the posted pic. I'm not sure. But the zebra wood is really a flat finish. There would be no glare.

Oh I see, the zebra wood would look like the better choice if the speaker is used in a dark room projection theater. I ended up having to wrap my piano black BMR monitors with black velvet cloth, as the glare was too much.

 

[cavedriver]

I swear I've sensed wind from a porthole as I was sitting. Just a sharp strong wind. Some speakers must move some air through those portholes.

The Monitor Audio Bronze's previous generation had obvious port chuffing, it was audible and you could feel it if you were near the speaker.

 

[cavedriver]

Oh I see, the zebra wood would look like the better choice if the speaker is used in a dark room projection theater. I ended up having to wrap my piano black BMR monitors with black velvet cloth, as the glare was too much.

The light from current OLED's is astounding. In the scene where King Theoden is putting on his armor in TT's there's a white light backlighting him from the doorway. When we first watched it on the OLED in a black room it was literally blinding, hehe.. Btw, I'm currently demo'ing a pair of the new HT towers in a prototype matte finish and they work quite well in the home theater environment.

 

[witwald]

Passive radiators produce the same alignment as a port.

Is that the case? Small wrote that the passive-radiator suspension compliance makes the response of a passive-radiator system different from that
of a comparable vented-box system.

 

[Dennis Murphy]

Is that the case? Small wrote that the passive-radiator suspension compliance makes the response of a passive-radiator system different from that
of a comparable vented-box system.

In what way? Different box size requried? Different roll-off characteristics below box tuning?

 

[tw 2022]

I swear I've sensed wind from a porthole as I was sitting. Just a sharp strong wind. Some speakers must move some air through those portholes.

I've experienced that with an emotiva 8" sub, the thing created it's own weather pattern when driven hard on ht material....

 

[witwald]

In what way? Different box size required? Different roll-off characteristics below box tuning?

In this way: the sound pressure magnitude response of a passive-radiator system is different from that of a comparable vented-box system. For example, doesn't the magnitude response function of a passive-radiator system typically contain a notch? This isn't present in the magnitude response of a vented-box system. Isn't it the case that a vented-box system typically has a sound pressure response function with a 4th-order roll-off rate below its cut-off frequency, while a passive-radiator system has a 5th-order roll-off rate? It would seem that, although passive radiators produce similar alignments to a port, they are not identical alignments.

 

[RickS]

Very nice, Philharmonic Audio delivers another impressive speaker value. If I did not so many parts around myself, would be buying BMR towers.

Bravo Dennis!

 

[Dennis Murphy]

In this way: the sound pressure magnitude response of a passive-radiator system is different from that of a comparable vented-box system. For example, doesn't the magnitude response function of a passive-radiator system typically contain a notch? This isn't present in the magnitude response of a vented-box system. Isn't it the case that a vented-box system typically has a sound pressure response function with a 4th-order roll-off rate below its cut-off frequency, while a passive-radiator system has a 5th-order roll-off rate? It would seem that, although passive radiators produce similar alignments to a port, they are not identical alignments.

I wasn't challenging your statement, just interested in learning the specifics. Thanks. But I think it's fair to say that the decision to use PR's rather than porst is based mainly on logistical considerations and concern about port noise rather than alignment.

 

[warpdrive]

Great that there are more choices of ultra high performance speakers at a reasonable price. Not one of the usual suspects like KEF or Genelec.

I am not in love with look of the exposed screws on the drivers though especially the BMR driver.

 

[MarkS]

It seems to me that a sealed alignment would be best for main speakers that are to be integrated with subwoofers. Both ports and passive radiators produce sound that is 180 degrees out of phase with the active drivers in the main speakers. So what is the subwoofer supposed to be in phase with, the active drivers, or the ports/PRs? It can't be in phase with both! I never see this question addressed. It seems clear that the best practice would be to cross the subs well above the driver/port transition; but then the port/PR does not seem to be serving any useful function. And Amir's plots often show nasty port resonances well into the midrange.

Not picking on you Dennis! Very very few companies make sealed mains these days, Sigberg being a notable exception. I just don't understand why this is the case, as it would seem to make for better sub integration.

 

[Dennis Murphy]

It seems to me that a sealed alignment would be best for main speakers that are to be integrated with subwoofers. Both ports and passive radiators produce sound that is 180 degrees out of phase with the active drivers in the main speakers. So what is the subwoofer supposed to be in phase with, the active drivers, or the ports/PRs? It can't be in phase with both! I never see this question addressed. It seems clear that the best practice would be to cross the subs well above or the driver/port transition; but then the port/PR does not seem to be serving any useful function. And Amir's plots often show nasty port resonances well into the midrange.

Not picking on you Dennis! Very very few companies make sealed mains these days, Sigberg being a notable exception. I just don't understand why this is the case, as it would seem to make for better sub integration.

The Purifi woofs don't do well sealed. But if you cross the sub high and use a high pass filter on the mains, I think the problem would be minimized.

 

[MarkS]

How high do you recommend for your HT speakers?

 

[witwald]

It seems clear that the best practice would be to cross the subs well above the driver/port transition; but then the port/PR does not seem to be serving any useful function.

Well, the port/passive radiator is part of the tuning of the low-frequency alignment. By that, I mean that they interact with the dynamical parameters of the driver to keep the output level from the low-frequency driver at a higher level than it would otherwise be.

And Amir's plots often show nasty port resonances well into the midrange.

I shudder every time I see those port resonances showing up. They must add a significant degree of sound coloration to the loudspeaker's response. Did not the loudspeaker designer care enough to check using a simple measurement?

Not picking on you Dennis! Very very few companies make sealed mains these days, Sigberg being a notable exception.

The ATC SCM40 loudspeakers come to mind...

I just don't understand why this is the case, as it would seem to make for better sub integration.

The bass output is significantly more limited for the same enclosure size and sensitivity, or the sensitivity is much lower for the same low-frequency cut-off and enclosure size. However, you are right in saying that a sealed enclosure has the potential to make for much better subwoofer integration. The second-order Butterworth high-pass filter on AVRs is testimony to that. Two second-order Butterworth filters create a 4th-order Linkwitz–Riley high-pass acoustic transfer function, which is complementary to the 4th-order Linkwitz–Riley low-pass filter supplied on many subwoofers (but not all) and AVRs.

 

[Dennis Murphy]

Well, the port/passive radiator is part of the tuning of the low-frequency alignment. By that, I mean that they interact with the dynamical parameters of the driver to keep the output level from the low-frequency driver at a higher level than it would otherwise be.

I shudder every time I see those port resonances showing up. They must add a significant degree of sound coloration to the loudspeaker's response. Did not the loudspeaker designer care enough to check using a simple measurement?

The ATC SCM40 loudspeakers come to mind...

The bass output is significantly more limited for the same enclosure size and sensitivity, or the sensitivity is much lower for the same low-frequency cut-off and enclosure size. However, you are right in saying that a sealed enclosure has the potential to make for much better subwoofer integration. The second-order Butterworth high-pass filter on AVRs is testimony to that. Two second-order Butterworth filters create a 4th-order Linkwitz–Riley high-pass acoustic transfer function, which is complementary to the 4th-order Linkwitz–Riley low-pass filter supplied on many subwoofers (but not all) and AVRs.

We did consider these issues when choosing the MLTL alignment. Three things to keep in mind. First, we didn't want the HT to be only attractive as a dedicated home theater speaker. Many people might find the smaller dimensions of the HT a bonus for music compared with the larger tower, and also would consider the Purifi woofers a big plus because of their extremely low distortion on up into the midrange. If we had run the Purifi's sealed in this cabinet, the F6 would be around 55 Hz., which is pretty high for a $4,500 tower. With Paul Kittinger's Mass Loaded Transmission Line optimization, the F6 is around 34 Hz. (Note the grid demarcations are 3 dB) Second, port resonances can be avoided with careful modeling in a tower cabinet. The problem is much harder to deal with in a stand-mount, particularly if a slotted port is used. The software Paul uses optimizes the location of the port as well as its dimensions. Below is some of the modeling for the HT. The first plot shows the system bass response--the dotted line is the woofer response if sealed. The second plot shows the port response and the woofer response with the port in play. Finally, The port can probably be sealed if, say, an 80 Hz crossover point is used, and it may not be necessary to use a high pass on the towers. I haven't tried that because the mass-loaded cabinet worked well enough for me in my HT.

 

[Hemi-Demon]

Looking back a few posts, you might have mistaken the zebra wood for the ebony, which is what's shown in the posted pic. I'm not sure. But the zebra wood is really a flat finish. There would be no glare.

Hello I plan on ordering a pair of these for my theater room. May I ask what do you recommend for a matching center channel, and two rear speakers?

 

[Dennis Murphy]

Hello I plan on ordering a pair of these for my theater room. May I ask what do you recommend for a matching center channel, and two rear speakers?

I'm working on a dedicated WMTMW center, although it will be large. A single BMR monitor on its side with the tweeter rotated will work well. We'll have a mini monitor in July that will work as surrounds. So will the BMR monitor, but it's big and more than you might want to pay. The Emotiva B1+ might be an interim choice.

 

[witwald]

So what is the subwoofer supposed to be in phase with, the active drivers, or the ports/PRs? It can't be in phase with both!

You've raised an interesting point. For starters, the subwoofer's low-pass acoustic response needs to blend in with the high-pass acoustic response of the main speaker system. The latter is made up of the driver's acoustic response as well as the acoustic response of the port or passive radiator.

As the wavelengths of sound at typical port/passive-radiator resonance frequencies are very long, the combined driver and port/passive-radiator acoustic output can be treated to a good approximation as a single source of acoustic output (a monopole). Of course, there are more complex low-frequency systems (e.g. dipoles), but for this example, we won't delve into those.

If the filtered acoustic outputs of the subwoofer and the main speakers are designed to follow the 4th-order Linkwitz–Riley response shapes, then the subwoofer and main speakers will be in-phase with each other. This is particularly important through the crossover transition region, probably for about an octave above and below the –6dB crossover frequency. The high-pass and low-pass shapes are what is called complementary, as they sum to unity magnitude.

The phase shift of the subwoofer at the crossover point is also affected by the inherent phase shift of its own low-frequency roll-off characteristics. Hence, the response of a typical subwoofer can only be approximately complementary to that of the high-pass filtered main speakers. However, the Linkwitz–Riley filter topology is relatively tolerant of phase shift errors, so any blending issues are usually well and truly hidden by the typical effects of room modes. Note that the phase shift difference between the subwoofer and the main speakers can usually be adjusted using the phase shift control (not the polarity switch) that some subwoofers provide.

It is of course possible to create a well-blended subwoofer and main speaker response using other types of filters. For example, the subwoofer could have a 3rd-order Butterworth low-pass filter applied to it, and the main speakers could have a 3rd-order Butterworth high-pass filter applied. The resulting acoustic outputs will be approximately complementary. However, 3rd-order Butterworth filters are sensitive to phase errors around their crossover point. Hence, achieving a smooth blended result, even theoretically and without including the effects room modes, is not entirely straightforward. There are interactions occurring that can be difficult to minimize, and that means that the summed response through the crossover region and either side of it can be a bit lumpy (not entirely flat).

 

[witwald]

I wasn't challenging your statement, just interested in learning the specifics. Thanks.

I didn't take your question as a challenge. My reply was maybe a bit wordy, as I felt that I needed to be as clear as possible about what I was referring to.

But I think it's fair to say that the decision to use PR's rather than ports is based mainly on logistical considerations and concern about port noise rather than alignment.

I would agree with that. Port noise can be a problem with vented systems, whether it be from chuffing sounds or port resonances, and the passive radiator gets around that issue quite neatly.