CarlssonPlanet

Hi Guys,

I have a set of OA51 here in Australia that I am upgrading to OA51LE2. What length should the bass reflex tube be? I think John Lasron said lengthen to 265mm but others have said 290mm. What is the latest? What do you recommend?

Regards,

Julian

Swedish Translation:

Hej,

Jag har en uppsättning av OA51 här i Australien att jag uppgradera till OA51LE2. Vilken längd ska basreflex röret? Jag tror att John Lasron sagt förlänga till 265 mm, men andra har sagt 290mm. Vilken är den senaste? Vad rekommenderar du?

Hälsningar,

Julian

Hi Julian,
when checking the Carlsson Illuminati section of the faktiskt forum I can't find any consensus regarding the bass reflex tube length when using SS8545 in OA51. Maybe you can use Gogle Xlate on these two threads:
http://www.faktiskt.se/modules.php?name ... 6r+l%E4ngd
http://www.faktiskt.se/modules.php?name ... 6r+l%E4ngd

According to the calculations there I draw the conclusion that 50 mm extension will only shift the tuning frequency down by about 2 Hz.
I would suggest that you take a few A4 sized paper sheets (210 x 297 mm, number of sheets depending of thickness) and cut off only 7 mm, roll them and shove them into the orginal tube and listen carefully to a good selection of your favourite recordings. Then listen to the same selction without the paper sheet.
What sounds best probably depends much more on the conditions of your listening room, where you place the OA51's and your own listening position.
If the difference is clearly recognizable, but you are undecied, try some other lengths .

Thanks Lennart,

I am going to go with 270mm.

Cheers

Julian

Lennertj: there is consensus about the length.
it is called the A4 mod and is as you described.
I've written a OA51 faq in carlsson illuminati place at faktiskt.se
mooseman: check out the oa51 FAQ thread which is glued. use googletranslate and you'll have all the info you'll ever need about oa51