Trying to figure out the alignment for JBL 2216ND-1

jmpsmash

Hi all,

I am trying to arrive at a alignment and thus box / port size for the JBL 2216ND-1. The cabinet will be vented and the driver should handle anything from F3 (whatever it ends up to be) up to 1kHz. My goal is to have a good tight bass but at the same time not sacrificing F3 too much.

For the JBL 2216ND-1, a member in another forum measured a pair of 2216ND-1 to have:

T/S data measured from the first driver:
Re = 5.556Ohm
Fs = 28.26Hz
Qts = 0.376
Qes = 0.397
Qms = 7.12
Le = 0.461mH
Mms=134.1gr
Vas = 332.8liters

T/S data measured from the second driver:
Re = 5.52Ohm
Fs = 27.59Hz
Qts = 0.3572
Qes = 0.3776
Qms = 6.589
Le = 0.4703mH
Mms=123.8gr
Vas = 378.4liters

they differ a little as one is warmed.

I tried plugging into WinISD for a few different standard alignments.

SBB4 : 7.443 ft^3, tuned to 28.26Hz, F3=33.8, GD@40Hz=9.6ms, GD@30Hz=15.25ms
SC4: 8.869 ft^3, tuned to 29.48Hz, F3=30.5, GD@40Hz=10.6ms, GD@30Hz=18.5ms
QB3: 9.017 ft^3, tuned to 29.62Hz, F3=30.5, GD@40Hz=10.8ms, GD@30Hz=18.6ms

Those are pretty big boxes, but their FR is pretty flat with no hump. And supposedly they are the alignments with tighter bass.

QBB4 seems to be the most practical in terms of size.

What I still trying to understand is...

The JBL 4367 cabinet (where the 2216ND-1 is used) is way smaller than the QBB4. From the 4367 dimensions, I estimated it to be less than 5 ft^3. Is there something JBL knows? or is it just a marketing decision to go with a smaller box as a compromise?

SBB4 traded off 3Hz for a few seconds GD. I know 3Hz is probably audible, how about a few mseconds in GD?

There are also some stuffing in the 4367 cabinet. Is that something worth considering ? supposedly in closed box, it "adds" 10% effective volume.

What would be the sound quality difference if I go with a even smaller boxes? I know GD will go up which means slower and less tight bass?

I want to make sure the bass is tight good quality. If there is small sacrifice in F3, I can EQ it back. But how about a few ms in GD?

David Morison

JBL's White Paper on the 4367 gives its frequency response curves and impedance plots, so you can see perhaps a little more about what design choices they've made - you could then simulate to see how closely you can match that using the T/S parameters you have obtained.
Might help by giving you a reference for what they have considered acceptable at least.

HTH,
David.

A few ms of group delay in the low bass is a non-issue. You can use whichever alignment suits, usually I prefer to tune below max flat. I don't know or care about the formal specific Q alignment names, because they're just points on a continuous 2d matrix. Basically I typically sim to max flat then adjust the tuning downward to be around F6.

This does a couple things:
Prevents "boomy" bass since there's boundary gain at and below tuning in most situations
Limits cone excursion to a lower frequency, and limits the need for highpass filters
Lowers vent air velocity and thus audible turbulence somewhat.

The first one is really the only applicable matter for a large woofer in home use, unless you're routing HT bass at high level.

John Busch

Another suggested alignment

Using Thiele's alignment based on QT you end up with:

VB: 9 cu. ft. gross (250L)
FB: 28 Hz
True operating QTS' assuming .5 ohm RG: .395
F3: 28 HZ
DV: 8"
LV: 14"

Nice all the way around except the box size. Excellent group delay. Symmetrical impedance peaks. No surprises. Good luck!

jmpsmash

Thanks all. I have only been reading books and articles and forum postings. Glad to hear that specific alignments are for reference only. I plan to start with 7.5 cu ft cabinet rounded to 28Hz. WinISD shows a pretty decent FR and GD. I will make the cabinet with some flexibility so I can play with different sizes and do more experimentation and learning.

Also do look at the excursion graphs. Some tunings (looking at you, "Large Low Tuned") can be risky in that they don't effectively control cone excursion, particularly as you go below Fc. For home use with "typical" music it's generally a non issue for 15"s but if you do HT without a high-pass, or like Some EDM/1812 Overature/Pipe Organs/Some Pop/Some Rap at (very) high level, it can be a problem.

jmpsmash

@badman, with a 7.5 cu ft box, max excursion above 30Hz is around 7mm @ 100w. There are no hard published limits but there is datasheet with test results and it shows tests being done at 9+mm.

Thanks for the tip!

Robh3606

Reading this has me scratching my head. I know the main difference was adding 10 grams of aquaplas and lowering FS to 28Hz. They must have changed the suspension as well as I don't think that's enough mass to make that large of a change. I found a much cleaner version of the Imp plot for the 4367 and Fb in that box is 32Hz judging from the min between the peaks. The box sizes here seem to big compared the JBL box volume Fb and F6 of 30Hz. You might want to just clone the box and tuning or try a test box before you cut wood.

Rob

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jmpsmash

the T/S param I got is from another person's measurements.

4367 is only 4-4.5cu ft net which is pretty small. they might have made some compromise to make it home friendly.

I will measure the params once I receive the 2216ND-1.

I plan to build the box without gluing in the back panel. I will do some undo-able sealing and do some measurements and listening before fixing it at an optimal volume for good.

GM

A bit late to the 'party' , but FWIW, a couple of pre-T/S alignments were Vas/1.44 and Vas/1.44/2, which the latter appears to have been used.