how many Liters for my 15"

[alexfisher7]

So.... Hum, Hum.
I am sure this has been (and will be)covered a thousand time over but can t find any even half-set rules about:
How many liters should I build my trapezoid speaker box to host a 15" speaker.
or more like how small can I get away with.

I will:
use birch ply 18mm
brace da living poop at of it.
vent it using a four corners config
separate the top from the 15".
thank you.

 

[fatmarley]

You need to know the thiele small parameters to model an enclosure. The t/s parameters are usually found in the manufacturers data sheet.

 

[Lojzek]

You can pretty much count on 100 litres vented for a decent design.

 

[alexfisher7]

http://www.jblproservice.com/pdf/Discrete Sales Models/2035HPL.pdf
That s all I could find.
And a diagram for their own cab but with such a different configuration that it is not much help to me.
I guess another question is: what suffers if the cab get smaller? My guess is less bottom but a little more close range pressure???

 

[Cal Weldon]

Here's what you need. Took 30 seconds to find. Google is your friend.
Subwoofer JBL 2035HPL specifications.
Remember with JBL that the black terminal is the +

 

[Lojzek]

JBL 2035 hpl twin 15" open baffle MTM

 

[alexfisher7]

I did try google but couldn t find this...
Well who is feeling like a silly goose now..
Thanks a lot.
And thanks for the JBL exotic polarity tip as well. did not know that so all worth it...


Ta ta.

 

[Cal Weldon]

Alex, AFAIK, they're the only ones who do that. Seems counterintuitive but they are well respected and have been doing it for all the time I've been in this hobby.

 

[alexfisher7]

just out of curiousity tho.
some calculator ask if the cab has bracings so if it does, reduces the volume of the cab. I am a wood worker so (not too brag but) the cab will be built to a quiet high standard with rigidity in mind. Is it worth taking in considaration?
I am not looking for an in depth awnser of cours as I imagine I would be lacking the knowlege 3 words in but you know...

Thanks for your time.

 

[Cal Weldon]

If you are going to use shelf braces then yes add internal volume to compensate. Stick or dowel braces not so much if you then have to redraw your plans. Unless you're only increasing one dimension that is.

 

[GM]

Subwoofer JBL 2035HPL specifications.

Note it's missing Re = 3.9 ohms for nominal 8 ohm for the other specs to work.

GM

 

[GM]

How many liters should I build my trapezoid speaker box to host a 15" speaker.
or more like how small can I get away with.

For prosound, recommend ~127.78 L net tuned to Fs for best trade-off between size, power handling.

Smallest would be ~90 L tuned to ~50 Hz for flattest response.

GM

 

[marabella]

I recommend "bassCADe" - www.selfmadehifi.de

It will meet all your demands in every aspect and best: It will give you all dimensions of the enclosure parts.

I have used it to calculate an enclosure for my 3-way sealed speaker and the simulated FR is verified by real F-measurement.

 

[weltersys]

Alex, AFAIK, they're the only ones who do that. Seems counterintuitive but they are well respected and have been doing it for all the time I've been in this hobby.

Cal,
Beginning in the early 1990s, JBL began an "orderly transition" to the positive-to-red standard in accordance with practices recommended by the AES, EIA, IEC, and other standards organizations.

http://www.jblpro.com/ProductAttachments/JBL_TechNoteN1V12C_v5.pdf

That said, the 2025HPL is not listed in that tech note.
It is always best to check each unit for polarity (a simple "pop" with a 9volt battery will push the cone forward or back) as any unit may be wired wrong from the factory or after a re-cone.

Art

 

[Cal Weldon]

Hi Art,
I had heard that but when I read the black is + I thought perhaps I was mistaken.

 

[GM]

I recommend "bassCADe" - www.selfmadehifi.de

Impressive! Surprised it's not more well known on the English forums.

GM

 

[MrKlinky]

For what it's worth, triangular corner vents are about the worst possible shape you can make a port. Please consider straight tubes at the very least. You can lose many dB of output through port compression, and add even more dB of distortion by selecting an unsuitable shaped port! One large and properly flared port is the best option.

 

[GM]

Indeed! Pretty much gave up getting folks to use one big vent once my 'soapbox' wore out though.

GM

 

[MrKlinky]

Indeed! Pretty much gave up getting folks to use one big vent once my 'soapbox' wore out though.

GM

Quite - a hole is a hole to most folks. Such a shame because there is so much to be gained (or reduced!) almost for free with a little bit of extra work on this 'hole'! There are a limited amount of port white papers on the web, but some with very good pragmatic information which can be readily reproduced by the DIYer.

 

[daemonsgr]

Quite - a hole is a hole to most folks. Such a shame because there is so much to be gained (or reduced!) almost for free with a little bit of extra work on this 'hole'! There are a limited amount of port white papers on the web, but some with very good pragmatic information which can be readily reproduced by the DIYer.

So having a similar design task (2226h around 120-130L) I had in my cad two round holes.
Should I just do one big rectangular?! Do side ratios play a big game?