PMC 25 24 Home Demo

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ellisdj

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Dec 11, 2008
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seemorebtts said:
ellisdj said:
now you have got better room acoustics you will likely appreciate the benefits of better cables more electro as their benefits won't be masked dude
Totally agree there.
TQ Black 2 - I would start another look at the subject right there if I was Electro and I have heard his system inc his cables, these are a great place to start
 

Andrewjvt

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ellisdj said:
now you have got better room acoustics you will likely appreciate the benefits of better cables more electro as their benefits won't be masked dude
dead flies cause even a bottle of perfume to stink, so a little foolishness spoils great wisdom and honor.
 

Electro

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Mar 30, 2011
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ellisdj said:
seemorebtts said:
ellisdj said:
now you have got better room acoustics you will likely appreciate the benefits of better cables more electro as their benefits won't be masked dude
Totally agree there.
TQ Black 2 - I would start another look at the subject right there if I was Electro and I have heard his system inc his cables, these are a great place to start
If you were to hear my system again now I doubt that you would even recognise it, I have adjusted the room acoustics to my liking ( not neccessarily flat ) and the difference is staggering , I have used the room to enhance the sound rather than take the room out of the sound. Many musicians have a favorite venue or place to play where they feel the natural acoustics of that space enhances their music, this is what I have tried to create to stunning effect imo .

All the equipment remains the same but the sound has been transformed to a point that it is hard to believe, you heard it at 60%, I would estimate it at 90% now.

The system completely dissapears and creates a stage with performers on it in front of you, it appears that the venue has been added to the end of the room with all the space and acoustic intact, with some recordings the soundstage also comes forward and envelopes the listening position so it sounds like you are sitting with the musicians but I would quess this is some sort of phase manipulation in the recording.

I have make one concession in the snake oil cable department *smile* , I have connected my dedicated earth spikes in the garden to the mains power supply earth directly to the system and it really does make a real and positive improvement imo.

I doubt I will start tinkering about with cables again because what I have is so good I don't want to mess it up.
 

ellisdj

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the only way to hear a recorded venue acoustic is to have no venue room acoustic of your own otherwise your hearing your own room acoustic venue on every song.
Very hard to achieve but something to bear in mind.

Happy to come and listen again mate still feel same about the cables though
 

Electro

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Mar 30, 2011
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ellisdj said:
the only way to hear a recorded venue acoustic is to have no venue room acoustic of your own otherwise your hearing your own room acoustic venue on every song. Very hard to achieve but something to bear in mind.

Happy to come and listen again mate still feel same about the cables though
If you look at it from a purist point of view then you are absolutely right.

What my room now adds is quite subtle but very pleasing, it's a slight positive addition to the recordings that adds to that sense of liveness and realism .

Before the treatment the sound of the room totally dominated the sound balance with that huge bass null in the middle of the room and the exaggerated reverb from the ceiling and upper side walls amongst other unpleasant things.

I suppose the ideal situation from a purists point of view would be to listen to a system in an anechoic chamber where there is zero input from the room but we all know how unnatural that can sound .

I have chosen to go down the route of manipulating and moving the sound energy about the room to create a better more balanced sound environment using that energy rather that declare all out war on the room by trying to damp it all out .

You are welcome to visit sometime to see if I have made a complete balls up of it but I think you will be pleasantly suprised.

I would also still like to slot a nice Electrocompaniet AW120 DMB power amp into your system and see yout jaw drop. *biggrin*
 

ellisdj

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you didn't realise that about your room until we met. at that point you thought you had the best sound possible now you know that wasn't the case.

always room for improvement mate can't make it worse with cables only better or back to where it is.
 

Electro

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ellisdj said:
you didn't realise that about your room until we met. at that point you thought you had the best sound possible now you know that wasn't the case.

always room for improvement mate can't make it worse with cables only better or back to where it is.
This is true and I owe you a debt of gratitude for that ! *drinks*

I am so happy with everything as it is atm cables are firmly at the bottom of the list, but who knows what will happen in future.
 

ellisdj

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happy to come round again would really like that. I have just bought really high quality recording equipment so could make a video piece on it would make good content.
 

Electro

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Sounds good to me , but it will have to wait 2 or 3 weeks because we are doing a bit of gardening atm and there is heavy machinery and kango hammers making lots of noise .
 

ellisdj

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no worries mate I am flat out at the minute as well look forward to that I am very interested to see what you have done and see the RPG monster you bought
 

CnoEvil

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Aug 21, 2009
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Alan Shaw of Harbeth is fairly opinionated, so bearing that in mind, and that listening should be the ultimate test....here is what he has said about TL as a design:

"You have to ask yourself why, of all the design choices and the hundreds or even thousands of brands competing in an overcrowded market place all desperate for some Unique Selling Points, something to excite the reviewers, dealers and public why there are not even a handful (to my knowledge) of speakers/brands promoting 'transmission line' technology. The bold fact is, and this is the sad, depressing objective truth, that it is fundamentally wrong from an engineering and acoustic perspective to mount a bass/midrange loudspeaker drive unit on the end of a pipe, tube or tunnel. It could even be the world's finest drive unit, the result would be the same.

The issue is not (necessarily) the performance of the drive unit, the problem is the pipe, tube or tunnel itself. And since this woofer-on-a-pipe is the core element in the 'TL' speaker, the core is rotten and no amount of wishful thinking or brilliant marketing can airbrush out the truth. Pipes behave acoustically like pipes, whether they are made of metal, wood or plastic or concrete. Whether they are circular, oval, square, triangular or rectangular in cross section. Whether they are long and straight, or convoluted, bent or folded. None of that fools the sound wave in the pipe, and when the wavelength [/i]of the sound being reproduced by the woofer mounted on the pipe has a mathematical relationship with the length [/i]of the pipe, strange pressure aberrations occur in the pipe and at the two ends of the pipe.

That's really bad news, because what we call sound [/i]is nothing more than a pressure change, and anything that disturbs that pressure at our ears, as a sound generated at the end of a pipe will, will muck-up the pressure in the room. Very bad news indeed if high fidelity is the goal.

Whether or not the effect, in your real world living room is audible or not is not worth debating, since we know that domestic rooms screw up the response of the finest, flattest speaker. The issue is that using crude measuring equipment the grizzly reality of the 'TL' concept is laid bare, and that really is as far as we need to explore the concept after cross-referencing to 100+ years of understanding of the physical nature of pipes. The wheel has not and cannot be reinvented: a pipe is a pipe!

A 'TL' system has a realistic chance of working tolerably well if and only if[/u] no frequencies above about 100Hz (if the TL is a big box) are allowed to reach the woofer which is driving the pipe. This is an absolutely crucial point[/b]. All the serious issues with the TL are because upper bass/midrange frequencies should not - actually must not[/u] - be allowed through to the woofer that is driving the pipe. There must be a sharp electrical cut-off in the signal that reached the woofer (and is coupled to the pipe) to positively inhibit frequencies getting to that woofer which would stimulate nodes/anti-nodes along the pipe, which is most definitely not the case when a bass/midrange[/u] driver is coupled to a so-called TL pipe.

So there you have the beginning and end of the problem. In the deep bass, the TL is an expensive way of achieving the same result as a well executed sealed or vented box. In frequencies above deep bass, the pipe is a disastrously wrong approach, wrong in every conceivable way. But what do we see of commercial 'TL' systems in production now? Precisely the wrong approach; the single bass/midrange[/u] driver is working the pipe in frequencies far beyond the bass, and the result is, of course, a series of peaks and troughs. That's physics, nothing to do with drive units or marketing and sadly, there is no workaround.

The reason those pipe-speakers have not been taken up by industry is because industry, unlike the DIYer, has test and measurement equipment and all professional speaker designers know only too well what the issues are with mounting a drive unit on the end of a tube will be. After all, anyone who is familiar with church organs or wind or brass instruments, even as a listener if not a player, will be very familiar with the relationship between pushing air into the top of a tube and the sound that comes out.

Another issue is what I see as misuse of the term "transmission line". A transmission line is an electrical term which has been inappropriately hijacked. Electrically, a transmission line is a electrical[/i] circuit which performs very specific actions in conveying a signal from one end of he circuit to the other, and the only commonality with the loudspeaker so-called TL is that there are two ends to the pipe as there is an input and output end to the circuit. As I see it, the so-called 'TL' speaker is in actuality an acoustic labyrinth[/u]. It's not called an acoustic labyrinth presumably because transmission line sound so much more sexy and high tech, but what you can buy is really an AL.

What defines an acoustic labyrinth? Two things ...

1) The drive unit is mounted at the far end of a tunnel of near or actually constant cross sectional area and
2) the mouth of the tunnel at the other end of the pipe is permanently open and of similar or actual cross sectional area as the drive unit end of the tunnel or pipe

Here from The ABC of HiFi by John Earl (1975, definitely worth having) is a drawing of the acoustic labyrinth, the very same technology that is wrongly marketed as a 'transmission line'.

Sound waves cannot be fooled into behaving in a special way just because a speaker designer implores them to, so it matters not whether the tunnel runs up and down inside the cabinet, or front to back, or side to side or side to side and up and down and also top to bottom. A tunnel is a tunnel, and what primarily matters to its acoustic performance is its length and to a lesser extent, its cross sectional area.

So, we've seen what an acoustic labyrinth[/i] looks like. It's a tunnel or pipe or tube driven at one end (by the source, the bass unit) and is fully open at the other end[/b]. That's an absolutely critical point. The far end away from the source (the woofer) is called the mouth or as noted above, the exhaust[/i], and like all motor exhaust systems must be open to the air or the engine will be strangled and cease normal operation.

What then is a transmission line[/i]? The fundamental character of the electrical transmission line is that the end opposite the source is completely sealed-off[/b], an electrical dead end. Not a little bit sealed: completely sealed, air-tight as it were. We can see than that the product claims about the so-called 'transmission line' speaker are technically wrong from first principles: the 'TL' cabinet self-evidently features a gaping-open mouth at the far end of the tunnel, which means that by definition, it is not at all a 'transmission line' because if it was, the end of the line would be sealed.

If we look at the electrical world from which the term transmission line was lifted, we see that a properly designed electrical TL behaves like this here, animation where the input signal to the TL is on the left and the end of the TL and the load at the far end of the pipe is the rectangular vertical box (which symbolically is a resistor) on the right. The essence of the true TL concept is that it is a closed-system[/b]; all the power input to the line is fully absorbed in the line and load. The essence of the acoustic labyrinth is the opposite: it is self evidently and open-system[/b], with energy flowing out of the mouth at the far end of the line and into the room or the room into the pipe.

And there we have the problem. If the so-called 'TL' speaker was really[/i] a transmission line system there would be no open mouth at the far end of the tunnel. Actually, if the pipe was truly a transmission line it wouldn't matter a jot if there was an open mouth or a completely sealed mouth because if there was perfect and progressive absorption of sound energy (not possible with existing materials or techniques) along the pipe there would be no energy left in the sound wave by the time it reached the far end. So open or not, no energy would flow into/out of the pipe.

But what we really have with so-called 'TL' speakers is a gaping hole at the end of a very short and poorly damped pipe (not that the damping can be much improved) and it's that open mouth combined with the nature of air column resonances in pipes - any pipes - that is the beginning and end of the insurmountable problems.

So you may well ask yourself, why not blank-off the open mouth and convert what is evidently an acoustic labyrinth into a true transmission line, assuming that is achievable to some degree or other? Or, sparing no expense or inconvenience, ramming the tunnel chock full of the most sound absorptive material known to NASA."
 

nopiano

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That’s very interesting, Cno. I must admit - and I did read it all - the most persuasive bit is simply how few designs adopt a TL. That said, sealed boxes are none too popular either nowadays and yet I have great admiration for that methodology.

Many years ago I lusted after the larger IMF designs, having once heard a tummy wobbling demonstration of a powerful organ piece. Nevertheless, I’ve heard some very persuasive sounds over the last 5 or so years from various PMCs, from the twenty 21 up to the fact .8, even though I think they are now overpriced to the tune of at least 20%.
 

lindsayt

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Apr 8, 2011
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What Alan Shaw says about transmission lines can be applied to ports, which are, after all, short tunnels.

This makes him a hypocrite.
 

Andrewjvt

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DougK said:
So is Alan Shaw saying that TL speakers are just overpriced Bose Wave speakers *smile*
I think he's saying that
the the TL design is more of a musical instrument like a trumpet rather than a disappearing monitor.
 

CnoEvil

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lindsayt said:
What Alan Shaw says about transmission lines can be applied to ports, which are, after all, short tunnels.

This makes him a hypocrite.
I'm not so sure....but can't argue from a position of authority, as I'm not a speaker designer.

As I understand it, it's something to do with the relationship of the length of the "pipe", to the wavelength of the sound being produced: "...when the wavelength [/i]of the sound being reproduced by the woofer mounted on the pipe has a mathematical relationship with the length [/i]of the pipe, strange pressure aberrations occur in the pipe and at the two ends of the pipe. "

I would love to hear from a speaker designer, who can speak objectively and preferably doesn't have a vested interest in either promoting their design, or rubbishing that of somone else.
 

Electro

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Mar 30, 2011
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Transmission line speaker manufacturers,

PMC, IMF, TDL, REGA, IPL, THOR, KEF, B&W, JM Reynaud, Castle Acoustics, Jordan Acoustics, Etude, Acoustic Zen, Salk Sound,

Cambridge Audio, Sony SSTL series, T&A, Boenicke, Focal/ JM Labs, Avalon etc etc......

I could go on but you get the point.

Transmission line speakers are more expensive to design and build, they need more raw materials and a great deal of experience and expertise to get right, most manufactures take the cheaper easy route with sealed or refex ported speakers .

When done right the transmission line is unbeatable.

The fact that Alan Shaw does not have the skill, expertise or inclination to build them is of absolutely no consequence.

Lets put Alan Shaw in a room with Peter Thomas and see who walks out with a smile on his face. *biggrin*
 

lindsayt

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CnoEvil said:
I would love to hear from a speaker designer, who can speak objectively and preferably doesn't have a vested interest in either promoting their design, or rubbishing that of somone else.
Me too, but I don't think such a person exists. As there will always be the accusation that any designer will be biased towards the type of speakers that they have designed.

There is actually quite a good objective test. Feed your system single cycle test tones at various bass frequencies. Put a microphone in front of the speakers and feed this into an oscilloscope device that has the ability to record onto paper or a digital file. Compare the resulting signal from the speakers against the single cycle test tone.

The technology was around in the 1960's to do this and was used by at least 1 manufacturer.

Testing done at that time showed that no speaker was brilliant at reproducing these test tones, but that some were a lot worse than others. With ported speakers being particularly poor in this respect.

Funny how arch objectivists like Alan Shaw have never shown (AFAIK) the results of single cycle tests for their speakers?

Is that because they either don't know about these tests, in which case one could question their competence? Or is it because these tests would not show their speakers in the best marketing light?
 
CnoEvil said:
I would love to hear from a speaker designer, who can speak objectively and preferably doesn't have a vested interest in either promoting their design, or rubbishing that of somone else.
Problem is, if you found one, how do you know how competent they are? Or how will you know that they know everything there is to know about every type of design? they may be well versed in conventional ported speakers, but not know that much about transmission line. They may be well versed in the theory, but how will their knowledge compare to say the designers at PMC who have been working with the design for decades?
 

Kubs

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Right, let's get back on topic. I've just picked up the KEF ref 1s for home demo. Just stopped off for a coffee before heading home.
Will post findings later .....

I do like the PMCs :)
 

iceman16

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Feb 8, 2011
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Kubs said:
Right, let's get back on topic. I've just picked up the KEF ref 1s for home demo. Just stopped off for a coffee before heading home. Will post findings later .....

I do like the PMCs :)
I’ve demo the ref1 last sat. and they are one of the best standmount speakers I heard.
 

Kubs

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Nov 8, 2007
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iceman16 said:
Kubs said:
Right, let's get back on topic. I've just picked up the KEF ref 1s for home demo. Just stopped off for a coffee before heading home. Will post findings later .....

I do like the PMCs :)
I’ve demo the ref1 last sat. and they are one of the best standmount speakers I heard. 
Was it a home demo?
 

iceman16

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Feb 8, 2011
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Kubs said:
iceman16 said:
Kubs said:
Right, let's get back on topic. I've just picked up the KEF ref 1s for home demo. Just stopped off for a coffee before heading home. Will post findings later .....

I do like the PMCs :)
I’ve demo the ref1 last sat. and they are one of the best standmount speakers I heard.
Was it a home demo?
No I demo them in shop and the Ref3 which I just ordered.
 

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