Hi guys,
I am just finishing the boxes for the MLTL from the Jordan site and I realize that the tube I got for the board is 50 mm OUTSIDE diameter, inside it is 46,4
The specified size for the port is 50X127 mm. I spoke with a few shops, they say that this is the standard , everything here is metric and I am wondering what to do - should I use this one and change the length accordingly or should I delay the celebration and search the world for the right type? Please help, it's more that frustrating...
I am just finishing the boxes for the MLTL from the Jordan site and I realize that the tube I got for the board is 50 mm OUTSIDE diameter, inside it is 46,4
The specified size for the port is 50X127 mm. I spoke with a few shops, they say that this is the standard , everything here is metric and I am wondering what to do - should I use this one and change the length accordingly or should I delay the celebration and search the world for the right type? Please help, it's more that frustrating...
Greets!
Technically, it's 50.8 mm i.d., but then I imagine you already know this. Anyway, at 46.4 mm i.d., this is about as small as I would use and if you want to maintain tuning, shorten it to 4"/101.6 mm.
This has been asked enough that hopefully Colin will add this info to the Jordan website.
While we're on the subject, please post the standard metric inside diameters of tubes normally used for vents from ~1" - 8" since the chart I have lists varying thicknesses for a given outside diameter based on its material/application and none work out to 46.4 mm i.d..
GM
Technically, it's 50.8 mm i.d., but then I imagine you already know this.
Anyway, at 46.4 mm i.d., this is about as small as I would use and if you want to maintain tuning, shorten it to 4"/101.6 mm. This has been asked enough that hopefully Colin will add this info to the Jordan website.
While we're on the subject, please post the standard metric inside diameters of tubes normally used for vents from ~1" - 8" since the chart I have lists varying thicknesses for a given outside diameter based on its material/application and none work out to 46.4 mm i.d..
GM
Hi GM - my hint-detectors were working overtime. Yes, I'll put that to Ted and post here when done.
If anyone would care to post standard internal tube diameters (metric or imperial, we swing both ways in the UK), I'll put a small chart on Ted's page. I'll add the ones I can find here in the UK at Wilmslow Audio and the like.
Whilst we're on the subject of ports, what's the largest diameter/shortest length you can use for the 31" port? I've asked on another thread but would appreciate your input as the designer. I'd like to use a forward-firing tube in a triangular enclosure without messing around with u-bends.
If anyone would care to post standard internal tube diameters (metric or imperial, we swing both ways in the UK), I'll put a small chart on Ted's page. I'll add the ones I can find here in the UK at Wilmslow Audio and the like.
Whilst we're on the subject of ports, what's the largest diameter/shortest length you can use for the 31" port? I've asked on another thread but would appreciate your input as the designer. I'd like to use a forward-firing tube in a triangular enclosure without messing around with u-bends.
Greets!
Hmm, since a vent's CSA dictates its length and 'speed', normally we speak in terms of what's the SMALLEST acceptable CSA that doesn't audibly 'honk'/'wheeze' to keep it as SHORT as practical, so the largest I recommend is the one I spec'd, 2" i.d. x 5" long, though if you want the euphonic harmonic distortion of a Jensen Ultraflex/Onken, then use a 3-3.25" i.d. x 13.5" long vent.
GM
Hmm, since a vent's CSA dictates its length and 'speed', normally we speak in terms of what's the SMALLEST acceptable CSA that doesn't audibly 'honk'/'wheeze' to keep it as SHORT as practical, so the largest I recommend is the one I spec'd, 2" i.d. x 5" long, though if you want the euphonic harmonic distortion of a Jensen Ultraflex/Onken, then use a 3-3.25" i.d. x 13.5" long vent.
GM
In my case, the misunderstanding comes from reading that the reflex or port system uses the mass of air in the port. I had assumed that to keep the mass constant, it was necessary to keep the volume the same. Glad I posed the question.
I'm not sure how Ted calculates his reflex ports, but he seems to favour the long, narrow approach.
I'm not sure how Ted calculates his reflex ports, but he seems to favour the long, narrow approach.
Right, but think of the air in the vent as a trapped air bubble that moves back and forth as a half WL resonator when excited by the trapped air bubble in the cab for lack of a more accurate analogy, so the bigger/heavier/massive the vent air bubble is, the lower in frequency it will resonate since it takes more energy to excite it and more surface friction to overcome.
Long and narrow makes it a resistive vent due to its high frictional back pressure, i.e. ~aperiodic, his trademark, so to speak.
GM
Long and narrow makes it a resistive vent due to its high frictional back pressure, i.e. ~aperiodic, his trademark, so to speak.
GM
A couple of follow on questions, rather than start a new thread. I am finally getting around to building the 31 MLTL so I can compare to the 48 and VTL. The drawing shows the port extending up into the cabinet.
Am I correct in assuming all the pipe action takes place at the end of the cabinet so the port would operate better if it extends out, below the cabinet floor?
If a vertical port is built behind the front panel, is an exit as shown in the sketch too much of a compromise? (Sound exiting as shown by red dots - my art teacher would have been proud!) This to avoid a curved port or the reflector shown in the original drawing on the Jordan site.
Am I correct in assuming all the pipe action takes place at the end of the cabinet so the port would operate better if it extends out, below the cabinet floor?
If a vertical port is built behind the front panel, is an exit as shown in the sketch too much of a compromise? (Sound exiting as shown by red dots - my art teacher would have been proud!) This to avoid a curved port or the reflector shown in the original drawing on the Jordan site.
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