127A box

[Hans]

Hi, I've just got 2 JBL 127A in fairly good condition. Any of you who can help me (yes offcourse you can) with the net volume and the porting of a box to make these sound good? I would appreciate the smallest box possible.

Hans

[Zilch]

127A is one of a small group of JBL drivers, basically the vintage "Decade" woofers, well suited for closed-box alignments. EBP = 54 for 127A

BB6P suggest really big boxes >10 cuft for venting, but they run out of cone displacement at low power. Looks great, but is impractical (red).

Venting alignments <2 cuft behave like L100 - a boomy peak in the bass (orange). That's how JBL used them, typically.

BB6P's suggested closed-box alignment is 2.75 cuft, but that size pushes the cone excursion limits. Use that, or a little smaller (2 - 2.5 cuft,) if you're willing to keep the SPL under control (blue).

My experimental 127As are out for refoam right now. They'll be going into an even smaller 1.5 cuft, a true acoustic suspension alignment, without excursion limit, due to box damping (violet).

You can see from the graphs, that basically provides L100 equivalent bass without the boom.

More on my recent adventures with closed boxes here:

http://audioheritage.org/vbulletin/s...ad.php?t=12036

[Hans]

Thanks a lot Zilch! I follow your ideeas and build a sealed 1.5 cuft box and we will see what the result will be. Please let us be in contact to exchange the results.

Hans

127A is one of a small group of JBL drivers, basically the vintage "Decade" woofers, well suited for closed-box alignments. EBP = 54 for 127A

BB6P suggest really big boxes >10 cuft for venting, but they run out of cone displacement at low power. Looks great, but is impractical (red).

Venting alignments <2 cuft behave like L100 - a boomy peak in the bass (orange). That's how JBL used them, typically.

BB6P's suggested closed-box alignment is 2.75 cuft, but that size pushes the cone excursion limits. Use that, or a little smaller (2 - 2.5 cuft,) if you're willing to keep the SPL under control (blue).

My experimental 127As are out for refoam right now. They'll be going into an even smaller 1.5 cuft, a true acoustic suspension alignment, without excursion limit, due to box damping (violet).

You can see from the graphs, that basically provides L100 equivalent bass without the boom.

More on my recent adventures in this area here:

http://audioheritage.org/vbulletin/s...ad.php?t=12036

[Zilch]

Good!

We'll compare results here, good or bad, for everyone to see....