transparence dipole loudspeaker

Fo what it's worth, I suspect Johnny has felt a little irritated by some of the responses he has received in his other "threads" (responses he deserved IMO), he then spotted Thorsten's sig, looked at his site and started this thread with the intention of trying to niggle Thorsten. I also think Thorsten is perfectly entitled to defend and clarify with regards to his product in response to a thread centred around it. Johnny's motives apart, some of this thread has been rather interesting and debates some pertinent points so, oddly, I'm glad he started the thread.

 

Hi,

Sorry, I'm not following what you are trying to say in your last sentence. As for the rest, yes, percussion will be different, multitracked vocals with slight delays etc between multiple instances of the same track are not comparable, but FWIW, there will still be different seperate transients, if there is no delay we simply get 6db gain.

You likely have learned a lot less about my own products (compared for example to others in whose design I had a hand but where I have no commercial involvement as the designs where placed in the public domain) than you have about other manufacturers products.

There are some of "my" products that get more mention, simply because they use sufficiently unusal technologies and hence are mentioned as examples.

Actually, my intention was to allow me to quit a discussion quickly sliding towards the silly and to instead let the product speak for itself.

But I suspect that with sufficient ill will even me placing many of my designs in the public domain is merely "promoting" my products. Had I more time I'd probably borrow a little Lewis Carrol from the introduction to "The Hunting of the Snark".

Ciao T

 

I wasn't really thinking of this thread (more the ones talking about CD players for instance where T links to pictures of the new models from his company). It was just that in this thread he saw fit to name the dealerships where you could dem his products along with a link. For me, that's sailing a little close to the wind. It's not as if anyone had asked for these details.

 

FFS Mike! Some of us are actually interested in the speakers. If Thorsten hadn't mentioned where they can be heard, I would have asked the question myself. I have been interested in single driver speakers for some time now and have done a lot of reading, although I have yet to hear a pair. If I were closer to Aylesbury or London I would go and listen. I look forward to their arrival in Bristol or hereabouts.

 

Hi,

Actually, the picture was of a Prototype, the final chassis work is just being approved and looks considerably different (that one looked a little to stark for my taste). But maybe that was sailing too close, can I be excused on the ground that this project has been going on for the better part of two years and consumed progressively more time and effort on my part (and much more than planned) and also from the others involved and I am REALLY excited to see things finally come together, so I bragged a little....

They are going to be really nice products in all aspects, but rest assured that we will use the conventional channels of promotion and do so very well (at least as well as we make the gear)....

BTW, you may be shocked that I will even invite ZG Members to come around for a listen (and offer to lug the stuff over as well) once I have really final prototypes at hand.... Now THAT might be considered promotion, though I see it more as "opinion polling" prior to a final release and more traditional promotion campaign....

Ciao T

 

T, will you be showing anything at the Bristol Show next month?

 

I don't think anyone has ever complained about Steve from 7V using this forum to market research, in fact I'm sure most of us are glad to help. Did anyone complain when he did the poll about which speaker we preferred the look of........No.
I'm sure that most of us are glad to feel our opinion matters and has some value.
If you have a ready made think group why not use it.

 

T, can I be the first one to take up your offer of lugging the kit over to my place?

 

Hi,

Maybe, maybe not. I find the majority of speakers to be misrepresented, simply because the engineering fails to account for application.

But to cover the behaviour of an open baffle in room briefly....

For starters we assume the open baffle is in an entierly open space (say 15m Up in the air.

First, if the wavelength of the radiated sound is small, compared to the baffle dimnsions all sound is radited out perpendicular to the baffle, nothing cancels. There is of course rear radiation, however the rear of conventional cone drivers have a natural acoustic lowpass filter formed by the magent and basket and the air trapped between basket and cone. The less skelletal and the more "oldfashioned" the driver frame is the better the attenuation of higher frequencies towards the rear.

Secondly, as the wavelength of the sound approaches the dimensions of the baffle some of the sound from the rear will fold forward and will be delayed "just so" which introduces a response peak at that frequency. If we have the driver entered in a circular baffle this peak is strongest at about 6db and fairly narrow. With a suitable design of rectangular baffle this can be kept to around 2db and over a wide bandwidth and can be used to offset some driver frequency respone aberation if present.

Thirdly, as we further increase the wavelength we observe that the rear wave progressively cancels the frontwave. This leads to the much vaunted 6db/8ve rolloff. However this rolloff, as you rightly observe covers only the baffles own action.

All of this is covered in great detail on Sigfried Linkwitz website using first order approximations, Mr. Backman accounts to fifth order effects, making his model more accurate, including even higher order effects will make the model even more accurate, but computationally more intensive.

The Drivers response is superimposed on what the baffle does. If we select a drive unit (or have one designed) whose response is more or less the inverse of that caused by baffle (this would imply a depression somewhere in the midrange and a boost towards higher and lower frequencies) we can achieve a pretty flat measured response, on axis, anechonic.

Fourth, as we now proceed to place our open baffle into a room we find that we have a number of further effects. These ARE actually covered by Siegfried Linkwith on his website, but not in the section on dipole theory, but in the section on crossovers, where they are treated as undesirable deviations from the "ideal".

I personally consider them instead as usefull allies in attaining a fairly wide bandwidth from a fairly compact dipole.

First, if our baffle is sitting on the floor, we have the floor image, which ultimatly adds theoretically 6db SPL at low frequencies, the exact amount with frequency being determined by the geometry between baffle, driver and floor.

We can use that effect conciously to extend the LF response of our speaker, in this case any anechonic measurement should be taken with the speaker placed in a halve-space envoironment (in other words on a floor that is sound reflective), easier approximated outdoors.

Second, at low frequencies our open baffle is very close to an ideal dipole, meaning it radiates as much sound towards the rear as it does to the front. In that it is actually identical to any other speaker, the main differences are that no sound is radiated at a 90 degree angle compared to the front axis and that the rear radiation is 180 degree out of phase with the front radiation.

Regardless what particlular phase or polarity the rear radiation has, when reflected forward by the wall behind the speaker it will lead to a comb filter effect with the direct sound, if we have a speaker that radiates sound omnidirectional at low frequencies we will get additional comb filtering from reflections from the side wall.

So, regardless what speaker we use, this comb filter pattern must develop, the one produced by a dipole is simply less complex and different to that of a conventional speaker. This combfilter pattern should also make clear why often moving a speaker as little as a few mm hcan have a profound effect on percieved sound.

Finally, dipoles interact differnet with room modes than monopoles (or indeed unipoles). The simple reason is that dipoles work by modulating air velocity and monopoles by modulating air pressure. As a result a monopole (traditional speaker) will excite room modes maximally when placed at room boundaries, which are pressure maxima zones, while a dipole will excite room modes maximally when placed at velocity maxima, that is right smack bang in the rooms center.

The reverse observe also holds. Thus a dipole will have the least room mode excitation when placed in a corner and a conventional speaker will have the least room mode excitation when placed in the room center.

Each of the above issues, together with actual driver behaviour determine what happens with Dipoles, making them in the end as simple and predictable as traditional speakers, however the theory and mathematical tools to predict them are still thin on the ground and where practically non existent when the actual design work on what became a commercial product in the transparence was designed.

Past that I feel that using dipole (or unipole) radiators throughout the modal range of the room has great merit and is among the possible solutions the best possible compromise (shedsize horns that retain teir directivity to below 50Hz are not practical in almost all situations).

Ciao T

 

Hi,

Nope, I have too many other priorities....

Ciao T

 

Hi,

Will see. Ilford is a LONG way. But we'll see.

First we have to get the prototypes, probably another month or two....

Ciao T

 

If you fancy a northern outpost.....

 

You made an unconditional offer, can't qualify it now. What's a few miles between friends? (I'm actually in Goodmayes).

BTW, I suppose I should ask what is the product?

 

Hi,

I best direct you to the post that so offended SM....

http://www.zerogain.com/forum/showpost.php?p=143812&postcount=23

Past that I could mention that there will be a matching hybrid integrated Amp, around 200WPC, quite a lot of the unique features and maybe even post a few more pictures from the Protypes, but that would only offend more, so I better not....

Ohh, okay then, just one itsy bitsy teeny weeny one...



This is the same chassis as in the old picture, except playing and lit up.... The rats nest next to it is a very early Amplifier prototype, final Amplifier chassis is the same as CDP, except no sliding door on top....

Ciao T

 

Have you come across alternative audio who are down near Taunton?

Peter stocks Vandersteen which whilst not single driver have 'minimum baffles' and 'optimize the dispersion and transient accuracy of the drivers while maintaining the input signal's time and phase integrity' (from the Vandersteen site) - which seemed to echo much of this thread.
Only heard them briefly but they sounded rather good and if you are investigating different approaches to the speaker question may be worth a listen.

 

Don't worry about offending S&M, he's alright really and not that easily offended, just likes to argue a lot for some reason.

 

No I don't Dev.

 

:d :d

 

Read the bit in bold, then ask yourself why '' digital room eq introduces phase distortion''.

Thinking about it, you've answered your own question.

 

I suppose it depends on if you consider distortion to be a deviation from how the system would be without the correction... or if you consider distortion a deviation from how the speakers would be without the room interfering and closer to the original recording and how it was intended to be heard.

I know which I consider the cause of distortion to be.

Johnny, could I know which 'properly designed' rooms you have heard? (or not, if they are well designed)