PMC Speakers

[Ron Texas]

For the PMC: It's not flat anywhere, it has a big suckout in the bass due to the transmission line system, directivity is all over the place.. And you'll pay a lot of money for it.

Reread my penultimate sentence. I have no problem with criticizing PMC in this context. What you said is exactly what he should have said instead of gratuitously trashing seven other manufacturers all from the same nation. That's improper. Several of them make replicas of the famous BBC LS3/5a. It's irrelevant if that old design is not textbook perfect because people want them whatever they are.

 

[graz_lag]

To put in my two-penny worth ...

I own a pair of Twenty 5.26 from PMC in my second setup, which I have put together with the goal to get a kind of British sound signature.
These are driven by a NAIT 5si integrated amplifier from NAIM Audio.

I mostly use the said setup for my late evening / night listening, where @ -45dB volume I can get so many details whilst it takes -20dB to take the same out from my Klipsch RF-7MKII in my other setup. (American sound signature)

I like both pairs to the same extent, the relevant applications of each of the two are simply too different.
Low volume listening with a lot of details ---> PMC Twenty 5.26
Do you like to rock? The PMCs are not for you.

So, go out and try to listen the speakers you have in your short list coupled with an amplifier in your budget, in listening environments you feel they're are as close as possible to yours.

 

[617]

As a speaker hobbyist I have very mixed feelings about PMC. On the one hand, I think their externally braced woofers and mid-domes are really cool. On the other hand, their transmission lines are clearly undersized.

Regarding these measurements, they are pretty bad. If you're designing a 2 way monitor without a waveguide and you want decent power handling, you're using steep crossover filters (LR4 or whatever) and that necessarily puts huge holes in your off axis response, especially vertical. What is really unforgivable is the axial response, this looks like a bargain speaker with a cap and a resistor on the tweeter. Considering the cost I would steer clear of PMC.

ATC I might consider however - the use of a mid dome can create wonderful wide dispersion which I maintain is a valid approach to hifi.

 

[Ilkless]

As a speaker hobbyist I have very mixed feelings about PMC. On the one hand, I think their externally braced woofers and mid-domes are really cool. On the other hand, their transmission lines are clearly undersized.

Regarding these measurements, they are pretty bad. If you're designing a 2 way monitor without a waveguide and you want decent power handling, you're using steep crossover filters (LR4 or whatever) and that necessarily puts huge holes in your off axis response, especially vertical. What is really unforgivable is the axial response, this looks like a bargain speaker with a cap and a resistor on the tweeter. Considering the cost I would steer clear of PMC.

ATC I might consider however - the use of a mid dome can create wonderful wide dispersion which I maintain is a valid approach to hifi.

Yes, make no mistake, despite my disdain for how remarkably overrated ATC's relatively pedestrian speakers are - I still recommend the ATC SCM7 under very rare circumstances: when someone local to me/some adjacent country to Singapore is looking for only made-in-Europe (pride of ownership thing) sealed passive speakers in that form factor to be bought locally. This is because the local distributor for ATC has very good pricing compared to the local prices of the usual active suspects (Genelec, Neumann, ADAM etc.).

 

[amarsicola]

Low volume listening with a lot of details ---> PMC Twenty 5.26

Owning a Twenty5.24 i fully agree.
The frequency response i found online was only for the previous model (https://pmc-speakers.com/sites/default/files/attachments/HiFi Critic twenty 24 review.pdf) and this reticency is irritating.
The approach is pretty british-euphonic with upper treble exalted and the Gundry dip at 4khz. Off-axis (lateral) response they say is non-linear in a controlled way, rolling off a lot the treble. According to the designer in this way the user can control the tonality by deciding the toe-in... not completely convincing. Anyway have a look at the in-room spectral balance which is nice. Bass extension is very good also.
Frequency response then is not everything, this speaker is damn coherent and tight in bass response thanks to transmission line that avoids the mid-bass crossover. Detail and dymanics are top level too.
So it is a joy to listen in its wide frequency range and slight "loudness" effect, provided you keep the volume reasonably low, you are in a room (pretty obvious), and you carefully adjust the toe-in, all the conditions being very reasonable. My choice was dictated by subjective superiority towards similarly priced ProAcs and B&W 702 s2 and Vienna acoustics.
Can you suggest a very well-measuring floorstanding speaker?

 

[Willem]

I am not a fan of PMC because of the transmission line technology. However there is no justification to be so rudely dismissive about some other brands that only share their British origin. Harbeth e.g. are truly scientifically designed speakers with their own cone material developed in a proper scientific research program. Their design is based on careful measurements and comprehensive computer simulation of relevant variables. The frequency response that results is remarkably flat and their quality is respected in many professional contexts. I admit that not all British brands are equally well designed but that is true for products from any country.

 

[Koeitje]

I tried Twenty.22's but they weren't an upgrade over my DIY Scan Speak Reference Monitors. I still want to try ATC because I want to try a closed monitor speaker and those are fairly rare in Europe.

 

[digicidal]

I think part of the sense of consistent failure being attributed in many of these cases is deliberate... and therefore not a "failure" at all. In all the stated cases, it makes perfect business sense for these manufacturers to tune at least some of their models/lines to reflect a "traditional BBC tuning" regardless of the fact that much of the rest of the audio world (producers and consumers alike) prefer a flatter on-axis response.

It's part of what comes with history and tradition. There are plenty of similarly "outdated sound designs" from manufacturers with long histories in every country (JBL, Klipsch, and many others have them). Even if they "know better"... they're in business to make money - and selling a product many of their customers want drives that... not seeking a ruler-flat anechoic response from every single SKU in their catalog.

Just because a manufacturer makes product(s) which are more nostalgia-based than current-standards-based doesn't make them a bad manufacturer... it likely just makes them a business savvy one. Which also makes them more likely to be around long enough to eventually give us something special (hopefully).

EDIT: As a contrary example... the Harbeth Model 30, while being a "retro styled" speaker in most respects actually has nearly a Harman target in FR (on-axis at least) - while still having a bit of extra midrange suckout to keep that "laid back British sound" I would imagine. I guarantee long hours were spent to achieve that, regardless of whether everyone would consider them "optimal" (they wouldn't).

I definitely don't like the BBC LS3/5a sound at all (makes me feel like my ears are plugged)... but as long as they weren't my only speakers, and if I had the room/budget for them... I'd definitely own a pair simply for historical significance.

 

[Ilkless]

I am not a fan of PMC because of the transmission line technology. However there is no justification to be so rudely dismissive about some other brands that only share their British origin. Harbeth e.g. are truly scientifically designed speakers with their own cone material developed in a proper scientific research program. Their design is based on careful measurements and comprehensive computer simulation of relevant variables. The frequency response that results is remarkably flat and their quality is respected in many professional contexts. I admit that not all British brands are equally well designed but that is true for products from any country.

The off-axis of the Harbeths are sheer mediocrity. Graphs were posted earlier in this thread. Glaring directivity mismatch.

I think part of the sense of consistent failure being attributed in many of these cases is deliberate... and therefore not a "failure" at all. In all the stated cases, it makes perfect business sense for these manufacturers to tune at least some of their models/lines to reflect a "traditional BBC tuning" regardless of the fact that much of the rest of the audio world (producers and consumers alike) prefer a flatter on-axis response.

It's part of what comes with history and tradition. There are plenty of similarly "outdated sound designs" from manufacturers with long histories in every country (JBL, Klipsch, and many others have them). Even if they "know better"... they're in business to make money - and selling a product many of their customers want drives that... not seeking a ruler-flat anechoic response from every single SKU in their catalog.

Just because a manufacturer makes product(s) which are more nostalgia-based than current-standards-based doesn't make them a bad manufacturer... it likely just makes them a business savvy one. Which also makes them more likely to be around long enough to eventually give us something special (hopefully).

EDIT: As a contrary example... the Harbeth Model 30, while being a "retro styled" speaker in most respects actually has nearly a Harman target in FR (on-axis at least) - while still having a bit of extra midrange suckout to keep that "laid back British sound" I would imagine. I guarantee long hours were spent to achieve that, regardless of whether everyone would consider them "optimal" (they wouldn't).

I definitely don't like the BBC LS3/5a sound at all (makes me feel like my ears are plugged)... but as long as they weren't my only speakers, and if I had the room/budget for them... I'd definitely own a pair simply for historical significance.

That is horrendous off-axis response, with the dip that deepens off-axis. There is simply no psychoacoustic evidence that points at this being a legitimate design choice (quite the contrary), and we would do well not to be apologists for regressive engineering.

 

[617]

The off-axis of the Harbeths are sheer mediocrity. Graphs were posted earlier in this thread. Glaring directivity mismatch.

That is horrendous off-axis response, with the dip that deepens off-axis. There is simply no psychoacoustic evidence that points at this being a legitimate design choice (quite the contrary), and we would do well not to be apologists for regressive engineering.

Any two way with baffle mounted drivers will have mismatches but it is possible to do much better than this.

 

[Willem]

I think off-axis response at 60 degrees or so is a bizarre design criterion. Who ever listens at such an angle? Also, note that the speaker was measured without the grille even though it was designed to be used with the grille and hence with an unintended somewhat higher reponse in higher frequencies. Anyway, see here for some more measurements of the most recent incarnation of the M30.2: https://www.stereophile.com/content...-anniversary-edition-loudspeaker-measurements
Yes, there is a heritage in these designs, but it is to the tradition of the BBC research department and its insistence on scientific methods. As for the LS3/5a, I think it was a remarkable speaker for its day, but it is beaten hands down by Harbeth's modern P3ESR designed for similar applications (I own both). I do not really understand why people should still try to imitate it with revival designs, but the P3ESR certainly is not that. I am not the only one who compares their transparency to that of the Quad Electrostats that I also own (2805s).

 

[pozz]

I think off-axis response at 60 degrees or so is a bizarre design criterion.

It's about room interactions. Flat on-axis and uneven off-axis response will produce an overall uneven response at the listening position given that what you hear is always comprised of direct and reflected sound.

I like the Harbeth sound honestly. Back when the BBC research was first made it was for the better. Though since then much more has been done which has made plain box speakers a gesture to an older era at best.

 

[617]

I think off-axis response at 60 degrees or so is a bizarre design criterion. Who ever listens at such an angle?

The off axis behavior of the speaker effects the reverberant field of the speaker. Yes, the axial response may be the most prominent thing you hear, and yes, almost all speakers exhibit a downward sloping power response, but a 10db dip of considerable bandwidth in the middle of the speaker response is not a good thing.

The conventional solution to minimizing this dip would be to use a shallower crossover slope to better blend the drivers. I would also comment that the midbass boost at 100hz in all these speakers really jumps out at me.

 

[Willem]

That bass boost is not real but a product of nearfield measurements.

 

[pozz]

That bass boost is not real but a product of nearfield measurements.

View attachment 41556
Any two way with baffle mounted drivers will have mismatches but it is possible to do much better than this.

https://www.soundstagenetwork.com/measurements/speakers/harbeth_30_domestic/
Made in an anechoic chamber.

 

[617]

That bass boost is not real but a product of nearfield measurements.

Thanks for pointing that out. I see this error in a lot of measurements. Small variances in measurement distance in the nearfield can create vastly different levels, so merging with farfield gated responses is not trivially easy. I mean, it's not hard either but you need to pay attention to baffle step and so on.

These measurements look a lot better.

 

[direstraitsfan98]

Two years ago when I was debating what end game speaker to step up to, I was considering a high end $10-15k pair of PMC speakers until I realized that no amount of genius engineering can escape the fact a couple of 6 inch drivers will start to have massive distortion at higher volume levels in the bass frequency. I am so glad I got my 4367 instead.

I think trying to create a full range loudspeaker using small drivers is a pointless endeavour and no amount of marketing hype and fancy cabinet construction can escape the simple truth of physics. That small drivers will distort massively when attempting to playback high spl in the bass regions.

Speaking of brit fi... I owned Harbeth 30.2 at one point. It was a lovely speaker and whatever the Harbeth 30.2 was doing to the midrange was kind of like magic. Made everything sound so pleasant to listen to. A dream to listen to female vocals on, like Diana Krall, Aimee Man, or Joni Mitchell. Of course compared to a speaker with a larger driver it will sound 'smaller' in comparison... which it did. Not to mention the Harbeths basically fell apart playing anything near 95db SPL. Bass would get very distorted, and there was a design flaw where the magnet holding the Harbeth logo against the grille would rattle against the baffle. Trying to blast Rush on the Harbeths was a bad idea... trying to blast Rush on 4367 is the BEST idea.

I suspect a large part of the Harbeth speaker failing to handle high spl (and this probably is true of PMC, ATC, Falcon, and all the other britfi brands mentioned in this thread so far) has to do with my final conclusion that expecting smaller drivers to handle full frequency response is a fools errand. Though its apparently is possible... I haven't heard Revel Salon2's but apparently they go down to 20hz. I've honestly never heard a speaker with under 8inch drivers tuned to play down to 20hz. It would be really interesting to hear how it would sound.

 

[Soniclife]

The conventional solution to minimizing this dip would be to use a shallower crossover slope to better blend the drivers. I would also comment that the midbass boost at 100hz in all these speakers really jumps out at me.

The high crossover point seems to be hurting the of axis, if they crossed over lower the dip would be much better controlled. I don't know why they use that high frequency crossover.

 

[Sal1950]

I was considering a high end $10-15k pair of PMC speakers until I realized that no amount of genius engineering can escape the fact a couple of 6 inch drivers will start to have massive distortion at higher volume levels in the bass frequency. I am so glad I got my 4367 instead.

Agreed, I'd got a bad case of green-eyed envy over your 4367's. If only I had the room and $.
I'm hoping for good things from the new JBL HDI line due for release after the first of the year and to be able to listen to them at the Tampa show in January.

 

[Ilkless]

I think off-axis response at 60 degrees or so is a bizarre design criterion. Who ever listens at such an angle? Also, note that the speaker was measured without the grille even though it was designed to be used with the grille and hence with an unintended somewhat higher reponse in higher frequencies. Anyway, see here for some more measurements of the most recent incarnation of the M30.2: https://www.stereophile.com/content...-anniversary-edition-loudspeaker-measurements
Yes, there is a heritage in these designs, but it is to the tradition of the BBC research department and its insistence on scientific methods. As for the LS3/5a, I think it was a remarkable speaker for its day, but it is beaten hands down by Harbeth's modern P3ESR designed for similar applications (I own both). I do not really understand why people should still try to imitate it with revival designs, but the P3ESR certainly is not that. I am not the only one who compares their transparency to that of the Quad Electrostats that I also own (2805s).

There is still a directivity mismatch.