JBL E140-8 cab build

[ThisBass]

Here's a pretty decent article on this matter
Measuring Loudspeaker Low-Frequency Response

Figure 4a:

"First, the sharp dip in woofer response at 37.6 Hz indicates the tuning frequency of the vented enclosure. In general, this value is more accurate than one obtained from the impedance curve, since it is not corrupted by voice coil inductance."

That's very interesting.
Yet I can't tell why the Port SPL does reach its peak center still a little bit above the "dip" of cone SPL, about 2..3 Hz or so.

Figure 9:
For the MIB pressure measurement the SPL that is generated by the Helmholtz resonator (SPL peak center) and the SPL generated by cone (dip) do share the same frequency (Fb).
That's what I'd expect by default.


edit:
as it can be observed in Figure 4a, a smallish frequency deviation of port peak SPL vers cone dip SPL does have only little effect to the magnitude of total sound, and was probably negligible.
But its not negligible anymore once the measured deviation is quite large, such as ~8Hz within this low-end frequency bandwidth of interest.

 

[12bass]

I just hope that this particular E140 feels pretty darn special for getting so much care and attention!

 

[Redbrangus]

 

[byacey]

Some may find this of interest:
Measuring Loudspeaker Driver Parameters

 

[squarepeg]

I just hope that this particular E140 feels pretty darn special for getting so much care and attention!

All JBLs are special:

 

[bass wood]

Any thoughts on replacing the factory speaker with this JBL in an Ampeg PF 115 HE sealed cab?
All your inputs would be highly appreciated!

 

[Pontiac Thrasher]

Any thoughts on replacing the factory speaker with this JBL in an Ampeg PF 115 HE sealed cab?
All your inputs would be highly appreciated!

Just do it!

Pic is Peavey cabs with JBL's, and awesome tilt-back Showman cab w/JBL's.

: )

 

[agedhorse]

Any thoughts on replacing the factory speaker with this JBL in an Ampeg PF 115 HE sealed cab?
All your inputs would be highly appreciated!

JBL speakers are generally poor performers in sealed cabinets, that was never their intended application. I did a comparison using the K-140 and the results are very obvious. Maybe somebody can provide a link.

 

[Pontiac Thrasher]

Any thoughts on replacing the factory speaker with this JBL in an Ampeg PF 115 HE sealed cab?
All your inputs would be highly appreciated!

Add a port to the cab?

 

[6thplanet]

Yeah, with it Qts, not really a sealed box speaker. First you need to measure the inside of the box to see what kinda volume your working with. Mine is around 4cf, but you can probably get by closer to 3. Adding a port shouldn't be an issue.

If your dead set on a sealed cab, then I'd search for a suitable driver that fits your needs.

I will add, in my opinion, if the E140 will work in your cab, ya probably won't be disappointed. That said, you do have to be mindful that it's not an SPL monster. It is decently efficient, but has a relatively low power rating compared to the drivers offered today.