I was aware of PMC’s specs, but have gone tontheir website and looked, and looked in my user manual, and in the user manual online for the 25 series. Yes, as I mentioned, they do tell you the transmission line length (Effective ATL, ATL=Advanced Transmission Line, the “Advanced” being a proprietary description for their development of it), but thar, as I said, is the internal construction of the speaker, and nothing to do with listening distance. There is nothing in the specs, nor the website page describing ATL, nor the two manuals I’ve looked at to suggest otherwise, which to me is unsurprising because the two are unrelated. In case my eyes are playing tricks you can find something saying that the ATL is the listening distance please copy it here.
Perhaps also you could describe what measurements you were taking that you felt supported your view, and why at floor level?
I haven’t heard PMCs but recognise what you say about the S40s. When I had them, they were v natural sounding, but because of the cabinet resonance that is used to help extend the bass, they could sound a bit slow. I moved up to Contour 20is which I’m really pleased with - completely organic sound which reveals the very different qualities in recordings without ever sounding harsh. There are probably more explicitly revealing speakers, but the Dynaudio sound is endlessly listenable. I guess one test with your PMCs is whether you find yourself listening to and enjoying new music outside of your usual tastes. I always thought the sign of a good speaker is that it makes you more able to enjoy music you usually can’t stand!
Those comments about the harshness of the top end have been made before. I would agree that with some recordings the 20.23s sound harsh, but in most cases it’s the recording’s fault, not the speakers’. If this was a design fault, PMC would have corrected it, I suppose.
I have a feeling that most of us expect music to sound more mellow than it really is in a live performance. “Natural”, “listenable” may refer to the kind of sound we would like to hear, not necessarily the sound produced in the actual concert hall.
Some weeks ago, I heard Isabelle Faust in Britten’s Violin Concerto, the violin sounded terribly harsh at times - but the performance was stunning.
I’m not sure it’s simply a question of “taste”.
@feeling_zen & @Innocent_Bystander
No comment on ATL length or the internal construction of the speaker, I don’t know about that and don’t discuss it. The fact is given by the manufacturer Effective ATL. PMC dealers will all confirm that the best effect is achieved at the indicated Effective ATL length. It is also my experience I was trying to convey in response to the question raised.
I have been using PMC Twenty5 23s for around 4 years and really enjoy them. I have used them initially with Quad 34/306 combination and moved to Naim in March 2022 with NAC202 and NAP200DR. Both sets of amplifies had no problem in driving them. My room is approx. 7.5m by 3.5m with the speakers situated at the end of the room. They are approx. 60cm from the rear wall. My experience is that they are detailed and have a good deep base that is well defined and fast. Imaging is very good and they excel with vocals. The room does have fitted carpets and a three-piece suite which probably controls any risk of harshness. They do take some time to run in and have found that they have a great sound and have no plans to change them in the future. I have since upgraded the preamp to a NAC282 with NACSC and HiCap DR.
The length of the transmission line determines the lowest frequency the speaker generates and does not affect the listening position in my experience. It always amazes me with the base that they produce for such a modest sized speaker.
My understanding - from many years of reading about TL speaker design, including trying to design my own, the meaning of that word “effective” in the context of effective transmission line length (in PMC’s case called advanced TL) is that that measurement is the length that an untreated transmission line (pipe) would be to have the same resonant frequency as the folded line containing sound restrictive material in the PMC design. The material in the pipe is said to reduce the effective speed of sound in the pipe, which is why it is equivalent to a longer physical length than it actually is, and that longer length is calked the effective length, or in PMC’s case adding the word “advanced”.
Again nothing to do with the room, where best positioning of speakers and listener, including the distance between, will vary greatly with the room.
In my case with PMC EB1i speakers having a declared effective ATL length of 3.5m, and doing extensive measurements with REW software, the best listening position was about 2.7m from each speaker, not 3.5. I don’t know what a PMC dealer you have spoken to might say about ATL but if they say it is the recommended listening position they are wrong. I’ve had demos with PMC speakers at three different dealers, and where they positioned the same speakers was not the same distance from the listening position at each place.
I suppose it could be read that way, with the meter in “Listened and measured with a meter on the floor” was a device like a laser sight, or a wheeled measuring device. For distance think of the normal thing being a tape measure, so “meter” suggested a sound level meter, spectrograph etc.
6 years ago my dealer leant me Twenty5.23s to replace my FB1s. In my room, with my amp. (not NAIM at that time) they lost all control of base at high volumes. Twenty5.24s were fine and I have very much enjoyed them since.
They do have a rather bright top end with some classical recordings so recently I tried a pair of Twenty5.26is thinking the midrange might tone down the tweeter. To my amazement they sounded much the same as my 24s, driven by my SN3.
A trial of NACA5 cables toned down the top end but at the expense of the clarity of Epic X.
Having tried a pair of good quality standmounts I have concluded that I need floorstanders and transmission lines to reveal the lower registers of the double bass that is so important to my enjoyment of classical music.
For the moment I am hanging on to my 24s but plan to upgrade amplification at some stage.
Unsurprising as same speaker family with the same tweeter, though dispersion will vary a little between the narrower and wider boxes. The primary difference as you go up the Twentfive range is improving bass from model to model, facilitated by the bigger boxes, but the 26 of course has change to midrange as well being three way.
A speaker manufacturer tries to design for a flat response in the expected listening environment. And that’s a very complex thing to do involving a lot of market research and guesswork. Speakers of a certain size and price point are assumed to be integrated into the average living room. Soft furnishing etc. The idea of what the average living room is varies greatly of course from maker to maker and country to country.
Above a certain size and price point it is assumed that the speakers take precedence over domestic harmony and are more likely to be flat response in an acoustically treated room.
You are probably likely to find that the Twenty range test flatter in a typical living room than their more expensive studio based models. And find that the studio based models test flatter in a treated room than the purely domestic models.
And if you have a room that is outside of the best guess of the maker then results can be unpredictable. Room correction software can help. As might different speakers or sometimes just hanging curtains and throwing a rug down to bring the top end in line with what measured as a recessed midrange.
It also boils down to the fact a speaker can be brilliant. But it might still not be for you. Horses for courses and all that.
I have often heard this said about PMC’s but I have never found them to be harsh or overly bright in any way, I understand the original Fact 8 was described as ‘speaking the truth’ so certain recordings would be harsh to listen to. I agree that the flooring will not in my opinion give you a warmer sound, I have a large rug in front of my listening position which definitely helps. I have PMC Twenty 26’s which are a larger model, bass is very good but I am driving these with a Parasound JC5 so lots of power, I also recently added a RELS510 sub, just give me that extra bit of low end at a lower volume level. The other thing you could
consider is Townshend bars or platforms, PMS themselves have used these in the demo’s I was gobsmacked at the difference they made, like a further upgrade.
I would get harshness at the top end from my very revealing turntable, this was partly down to the cartridge not being quite right and was better once the manufacturer sorted it out, but still not 100% sorted on all my vinyl and some had bad sibilance.
Not sure why but with the titan 808 this has gone now? Only found this out the other week as i went to show a hifi mate how bad this certain vinyl was only to find out it was now fine. So went and played all the other problem vinyl i had to find the problem had gone.
The only thing that has changed in the vinyl set up is speakers and so can only assume that my fact 12’s was adding or not copying with things?
The Fact 12’s are one down from the the top of the domestic range, the Fact Range will show up everything on a recording, I do not know the Titan Range, maybe they are more forgiving?
@1GiantLeap The tweeters settled down nicely so these speakers have become the best set I have ever owned. Bought them as an interim until I can afford the Dynaudio Heritage Specials (best bookshelf speakers I have ever auditioned) but I think I’ll redirect whatever I can save towards a 555DR.
Funny thing is, at first the whole system sounded clinical and bright, very much opposed to the organic nature of the Dynaudio speakers I owned in the past. Not anymore. They now sound spectacular!
Another interesting fact, these speakers are so fast, not even a Dynaudio Sub 6 can keep up.