PMS, built by Linas/Lithuania
Copyright 2011 Troels Gravesen
       

Hi,
I've finished PMS almost 1,5 year ago. Construction was based on you kits components and drawings. Finished photos attached. Againts my wishes i've made cabinets on wheels due to better mobility and stability (finished cabinted (wheight is about 40 kg each ) You did a great job with this project, so i just tried to copy as close as possible (except of height -my PMS is 120 cm therefore ext volume is 55 ltr and main MDF is 25 mm) and calculated net volume for bass ~40-45 litres) :)
Sound?
Yes PMS sound good, but many listeners voted that PMS need more bass... But i dont worry about it too much because vents weren't tunned at all (mounted only vents from kits).
Current gear setup is:
Advance accoustic integrated amplifier MAP 105 (2x70W) have no bass and treble regulation.. Sound like no name, but but i purchased it new for half price just 250 Euros form dealer sales with 2y warranty and remote .. http://www.advance-acoustic.com/en/produits/index/detail/id/3/sec/1
Technics SH -GE90 equalizer and Technics CD player SL-PS 840
I've read your articles about vent tunning, calculations, etc and some theory and practice differences on vent tunning results.. and i lost on huge amount of information.. I'll appreciate if you could give hints espacially for FINAL vents tunning? Your recomendation -The vent tuning appear to be around 34-35 Hz. This with the two 4.6 (ID) x 12 cm vents.
My Initial data are External PMS volume 55 litres. NET volume ~40-45 litres, i calculated it and it seems close to 45 litres
And for 45 litres i calculated 4,6x 14 cm vents (vent tuning for 34-35 Hz). But i've added 20 ltr wool damping into each cabinet and placed it acc PMS recomendation (see photo), so do volume increase virtualy And vent lenght must be changed?
With PMS kit i get 4 pcs vents with lenght 13 cm and ID1 -5,0 cm and Id2- 4,4 cm i.e. vent tube is narrowed down -(inside cabinet). So I'm lost between my calculations, litres, damping and vent tuning.... And how do i know if the vent tunning is right?
Usually in internet articles goes recomendations to shorten the vent lenght durring vent tunning process...Can i hear it clearly thet vent tunning is right and speakers must play very loudly??? i havent serious measuring equipment but i have CD with separated sound files with signals from 20 hz to 87 hz (i.e. 20, 21, 22 ,23..87 hz - 12-20 sec each).
Thanks in advance for your thoughts on helping me with final PMS manufacturing stage..:)
Keep going with your next projects :)
Best regards
Linas/Lithuania

Hi Linas,
As discussed via email, the vent tuning should be solved. What remains is the lack of bass level and I strongly suggest reading comments from this recent PMS builder:
http://www.troelsgravesen.dk/PMS_Andy.htm, and here also: http://www.troelsgravesen.dk/PMS_builders.htm.
Based on your photos, I'm sure the lack of bass response is due to too heavy damping of the cabinets. PMS only takes minor damping material and due to the narrow cabinet it's easy to stuff the cavities too heavily. I used 10 mm felt on all real panals and only a minor amount of acoustilux at top and bottom. Damping of mid cab: Felt materials on all sides except front panel + 30 mm acoustilux at rear panel around vent - if such is present.
Best regards, Troels