Does anyone has got PMC bass driver T/s parameters to analyze what`s soo unique approach about the driver to get loaded in TL
I am surprised nobody has attempted to answer your question.
Maybe you already have read this
https://audioxpress.com/article/thor-a-d-appolito-transmission-line
Table 1 gives details of the Seas drive unit parameters used for the Thor design.
As to PMC I think the Peerless HDS series Fibreglass ( Gweave?) drivers would allow you to design something using a TL design programme. I think that the HDS series are great drivers for the money, I have used the 5 and 6inch 8 ohms for reflex loaded designs crossing over around 2Khz.
I am sure all the other well known brands will have something suitable. Maybe a SB acoustics 6 inch CAC driver might be a sensible choice?
I haven't built a TL yet maybe one day.
The folding of the line has got to help with cabinet resonances, and the way the bass gradually diminishes possibly lessens some room interaction's. People do seem to like the bass aspects of PMC.
Also PMC typically keep their cabinets slim, and the tweeter position tends to get mounted high close to the top of the cabinet.. I notice that they also use a claimed low crossover frequency of 1.7KHz and 4th order crossover slopes, all subtle choices. They do seem to get through listening and technical reviews quite well.
However, to make it sound like a PMC you will need to use military grade PCB's, formula 1 inspired CFD to model the laminar flow vents, maybe laser scanning technology for measuring cabinet vibrations, a stainless steel backplate for the crossover mounting and custom made binding posts. Phew.
Maybe you already have read this
https://audioxpress.com/article/thor-a-d-appolito-transmission-line
Table 1 gives details of the Seas drive unit parameters used for the Thor design.
As to PMC I think the Peerless HDS series Fibreglass ( Gweave?) drivers would allow you to design something using a TL design programme. I think that the HDS series are great drivers for the money, I have used the 5 and 6inch 8 ohms for reflex loaded designs crossing over around 2Khz.
I am sure all the other well known brands will have something suitable. Maybe a SB acoustics 6 inch CAC driver might be a sensible choice?
I haven't built a TL yet maybe one day.
The folding of the line has got to help with cabinet resonances, and the way the bass gradually diminishes possibly lessens some room interaction's. People do seem to like the bass aspects of PMC.
Also PMC typically keep their cabinets slim, and the tweeter position tends to get mounted high close to the top of the cabinet.. I notice that they also use a claimed low crossover frequency of 1.7KHz and 4th order crossover slopes, all subtle choices. They do seem to get through listening and technical reviews quite well.
However, to make it sound like a PMC you will need to use military grade PCB's, formula 1 inspired CFD to model the laminar flow vents, maybe laser scanning technology for measuring cabinet vibrations, a stainless steel backplate for the crossover mounting and custom made binding posts. Phew.
No clue, but the only unique part of TL design is than ANY driver will work well if it meets the needs of the app, so OK, time for a bit of a [BR], [ML]TL basic design tutorial to at least get you pointed in the right direction, if not a 'close enough' finished box alignment in the hope that you'll be able to critique yours and improve on them:
As for how far below Fs is practical depends on a number of things, though with a basic BR out away from walls/corners, a 1/2 octave [~0.707] below Fs is the rule-of-thumb [ROT] based on excursion increasing at 4x/octave.
In short, > ~0.403 Qts' is where Fb < Fs and its effective upper mass corner is where basic T/S theory peters out, so, any change in a basic sealed/vented box alignment's sim above this point will be due to the driver's inductance [Le].
upper mass corner: Fhm = 2*Fs/Qts'
[Qts']: [Qts] + any added series resistance [Rs]: http://www.mh-audio.nl/Calculators/newqts.html
[Rs] = 0.5 ohm minimum for wiring, so may be higher if a super small gauge is used as a series resistor plus any added resistance from an XO/whatever.
There are many T/S theory box alignment routines, though this one for max flat reflex alignments is my preference:
Margolis-Small's HP 67/97 & 41C calculator program: http://www.aes.org/e-lib/browse.cfm?elib=3902
net volume [Vb] [L] = 20*Vas*Qts'^3.3
box tuning [Fb] [Hz] = 0.42*Fs*Qts'^-0.96
To the 1st approximation then is to calculate the box net volume [Vb], tuning [Fb] for ANY reflex BR = vented] alignment with these basic understandings:
While the 'sweet spot' [mean] is a ~0.4412 Qts', a 'close enough' simple guideline for [BR], mass loaded [ML = vented] TLs is:
~0.403, Vb = Vas, Fb = Fs [MLTL]
< ~0.403, Vb = < Vas, Fb = > Fs [inverse tapered MLTQWT]
Where Qts' breakpoints are IME since I've never seen any professional docs on the subject per se other than the Efficiency BW Product [EBP]: http://redspade-audio.blogspot.com/2011/03/efficiency-bandwidth-product-ebp.html
< ~ 0.312 = low
~ 0.312 ~ 0.62 = medium
Heavy damping limitations:
While the three different tapered TLs and their vented alignment variants [mass loaded/MLTL, MLTQWT, MLhorn] can be used with any driver, there's a 'best overall' range for each IME, so FWIW:
Inverse tapered TQWT for when the vent's dimensions are long/large for the box size [Qts' < ~0.312] same as for passive radiators [PR]
Expanding tapered TQWT [horn] for when specs dictate a tuning below Fs for flattest response [Qts' > ~0.403]
Constant [straight] tapered TL for when specs dictate an alignment in between the above extremes [~ 0.312 - 0.403 Qts']
The vent/horn terminus opening causes a downward shift, hence the distances are further down than a closed box's 1/5, 1/3rd, etc., but both the driver and vent should be at a vented pipe's odd harmonics. You can figure it out using Hornresp's
'path' slider in 'chamber' or just use these as proven audibly 'close enough':
Driver offset [Zd] = [L]x ~ 0 [top], 0.217, 0.349, 0.424, 0.561
Of course the first one doesn't apply to any ~zero area [CSA] terminated pipe/horns and if your desired ear seated/whatever driver height doesn't line up close enough to your design, suggest you change the alignment tuning [pipe's length] by adjusting Fs to get it to line up with one of these offsets.
Vent offset only, depending on box HxWxD ratio: vent offset [Zv] = [L]x ~0.651, 0.714, 0.848, 0 [bottom]
For the twenty 5i series, my first guess would be something from the Peerless HDS series.
See below.
https://www.soundimports.eu/en/peerless-by-tymphany-hds-p830991.htmland
https://www.soundimports.eu/en/peerless-by-tymphany-hds-p830990.htmlThe new I tweeter is somewhat more difficult probably a custom SEAS 19mm soft dome with wide surround and mesh grill.
If was thinking of a 1.7KHz Xover and SEAS I would go with the fairly new SEAS (H1825) metal dome with a wide fabric surround
https://www.soundimports.eu/en/seas-27tacgb.html.
The 50mm dome maybe a variation on the Visaton 50mm dome with custom mesh grill and edge wound voice coil ?
All conjecture of course.
See below.
https://www.soundimports.eu/en/peerless-by-tymphany-hds-p830991.htmland
https://www.soundimports.eu/en/peerless-by-tymphany-hds-p830990.htmlThe new I tweeter is somewhat more difficult probably a custom SEAS 19mm soft dome with wide surround and mesh grill.
If was thinking of a 1.7KHz Xover and SEAS I would go with the fairly new SEAS (H1825) metal dome with a wide fabric surround
https://www.soundimports.eu/en/seas-27tacgb.html.
The 50mm dome maybe a variation on the Visaton 50mm dome with custom mesh grill and edge wound voice coil ?
All conjecture of course.
Like Quested and Neumann PMC started out using the ATC 3" dome mid until they became more popular and ATC stopped supplying them.
Neumann just cancelled the model they used the ATC in, Quested uses the Volt dome and PMC make their own.
Volt now makes a 2"/50mm dome but I do not know if that is what PMC uses.
Volt Loudspeakers | VM527 (2″ Midrange Dome)
Neumann just cancelled the model they used the ATC in, Quested uses the Volt dome and PMC make their own.
Volt now makes a 2"/50mm dome but I do not know if that is what PMC uses.
Volt Loudspeakers | VM527 (2″ Midrange Dome)
I think for the Finestra and others at that level of performance they use their own in house developed dome.
I guess seas is making for them now. I have never seen their inhouse developed driver assembly video anywhere.
For great control in performance one should have inhouse drivers engineered and built which many big companies are famous for.
To Rhythmsandy.
With GM's advice on the necessary pre requisites for design are you going forward with a build?
Have you started shortlisting drivers and plugging in the numbers and exercising your calculator and a piece of paper, or are you going to use horn response or SpicyTL to crack this ?
With GM's advice on the necessary pre requisites for design are you going forward with a build?
Have you started shortlisting drivers and plugging in the numbers and exercising your calculator and a piece of paper, or are you going to use horn response or SpicyTL to crack this ?
First point is that in my observation that a TL cabinet requires same volume as the length of tuning and the cross section area x length of the tunnel to be in similar with Vas so that the loading is quiet in balance with the compliance of the driver. Hence just wanted to know if pmc is making cabinets where the Vas is custom specified. I feel if Qts is low then the overall required volume is quite low and will not suffice the Sd x length of the TL to be in sync. Hence I see most of the cases either PMC having low sensitivity since it should have higher VAS and lower Fs with Qt being in the region of 0.4. So if anyone had the T/s parameter data then i could co relate what they are actually doing. The conventional story that its very complicated need to be reconsidered. So if anyone has the real measured T/s param one can clearly validate what Vas they are aiming for.
You can look up standard params for all of the drivers be it Volt or Tymphany Peerless and see if they come close to the criteria you want.
The params may be easily available in the Vituix driver database, I havent checked yet, still having a cuppa.
The params may be easily available in the Vituix driver database, I havent checked yet, still having a cuppa.
I see Vas is only 0.71cubic foot which no way will get any TL length without over sized cabinet. It might be a custom driver built for pmc.
I don't know which driver you have in mind but for the 12" Volt the ideal ported box is somewhat larger than Vas (86L) at 110L and the T-L comes out at a similar size.
Note that box calculators do not return sensible box volumes for low Qts drivers (below 0.32 or so). They suggest boxes which are way too small and tuned to high ie above Fs.
Note that box calculators do not return sensible box volumes for low Qts drivers (below 0.32 or so). They suggest boxes which are way too small and tuned to high ie above Fs.
To be fair I know nothing about that driver.
I only know about the Volt because I have a pair for which I've built transmission lines.
I only know about the Volt because I have a pair for which I've built transmission lines.