Need Help Optimizing Enclosure

[HipoFutura]

I've been modeling an enclosure for my new 2235H subs using WinISD. The attached graph represents the best specs I've been able to come up with. I would like to get closer to 25 hz with less db loss. I thought the 2235H capable of better. Is this just my ignorance or have I hit the lower limit for the driver. I should add that I'm trying to keep the enclosure smaller than my house! Working with 200 Liters (there abouts). Any suggestions?

Don

[Robh3606]

Your not going to get there without EQ. You might want to look at the B380 and the BX-63 crossover. Smaller box, added EQ at 25Hz.

Rob:)

[Zilch]

Rule-of-thumb limit for "usable" bass is -10 dB.

Search the forums for "B380" and "B-380" to find various discussions of optimum "alignments" for 2235H. I run them in 4.5 (B380) and 5 (4507, L200) cuft. with great satisfaction here.

[morbo!]

Hiya`s

I just want an answer to thwe following question`s

That graph goes alll the way to 1k
Not bieng an expert
But the post said sub
From that ive read on subs.The cut off would be lower than that
why would you measure a sub to 1k?
And would it not have a steep roll off after the point at wicth u decided to cross over?
wouldnt that just create a muddy sound if it were over lapping with the woofers?


now morbo becomes a pain in the ass!

[Zilch]

wouldnt that just create a muddy sound if it were over lapping with the woofers?Morbo is correct. Use as a sub assumes that a lowpass filter would be applied at the desired crossover frequency.

The simulation doesn't know what type, or what frequency, so it just shows the response as if used as a woofer, full range.

The designer then superimposes the chosen filter upon the response.

Some more sophisticated simulators allow inputting actual filters to show the predicted behavior of box, driver, and filter combined.

At this point in the process, HipoFutura is manipulating box sizes and tunings to achieve and optimize his desired response at the lowest frequencies, which will have little effect at his anticipated crossover point....

[morbo!]

oh wow
thanks zilchy
a big hand for morbo:applaud:
And even bigger hand for the whole lh gang :applaud:
I`m sure i could not have made that obversavtion 12 months ago

again thanks all here
an amazing place starting or finishing your audio jouney
im sure this is the place to do it

sim vs reality (i get that now) but still good thnx

[HipoFutura]

My crossover point is 80hz. I find things begin to get muddy above that. The 123A-1 in the L100 picks up quite nicely at that crossover point.

Zilch, I started modeling with the B380 cube of 4.5, but wasn't satisified with below 35 hz specs. It did have a smoother slope from 100hz down, but dropped off too fast below 50hz. It looks like I'll get more thump with the bigger box.

My initial thought was to follow your advice on the B380, but the sims indicated it wasn't utilizing the full capability of the 2235H. For that reason I started modeling different cubes and tuning freqs. The best seemed to be the 200 liters and 28hz combo. I will research old post regarding the B380.

Don

[Robh3606]

To use the B380 box size you need the BX-63 to add EQ to get the desired response.

http://www.lansingheritage.org/html/jbl/specs/home-speakers/1983-b380-b460.htm

Rob:)

[HipoFutura]

Rob, I just read up on the BX-63. I don't think it's required for my configuration. I'm now using an Ashly XR2001 crossover to tri-amp. All I have to do is crank up the gain on the LF channels to pick up a few db for the subs.

My question now is whether or not the 200L box tuned to 28hz is an improvement over the B380 box. I think it is, but would like to hear from others.

Don

[spkrman57]

I plan to research Zilch's posts regarding that implementation as I have the L200 cabs and a pair of 2235s to use as subs underneath my E-130(paper dustcap) and 2404H project.

The E-130 when using a paper dustcap is very sweet and smooth(to my ears) between 120hz and 3.6khz.

Ron

[Zilch]

My question now is whether or not the 200L box tuned to 28hz is an improvement over the B380 box. I think it is, but would like to hear from others.There's real experience regarding this documented in earlier posts here, including comparative analysis of various alignments using 2235H.

You'll have to dig for it, as Giskard is on sabbatical right now.

BB6P suggests tuning 200L to 22 Hz for "extended bass" (black). Your 28 Hz tuning is shown in red.

I run them in 5 cuft. at ~27.5 Hz.

Frankly, with room reinforcement, B380 works even without EQ. A different optimum alignment may be found in the archives here.

BX63(A) provides the design EQ contour for B380/B460, as described here:

http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm

You'll need a highpass filter to protect the driver from overexcursion if you intend to crank these (bottom). BX63(A) has that built-in for B380....

[HipoFutura]

Thank Zilch! I have spent some time searching, but haven't made it through all the old posts yet. Your graph supports my modeling. It looks like I'll drop off much faster below 26hz. At that point your just about done with the audio range anyway. My tuning does give a bit more gain in the 28 - 80 range. Either way I can re-tune the box to see if there's a "real" difference. It does seem the 200L box is the way to go. Bit bigger than I wanted, but I can live with it.

Don

[Zilch]

200L is pretty big for use in living space. Even 5 cuft. is "major."

A big advantage of B380 is its small (by comparison) size.

See here for alternative tunings using that smaller box:

http://audioheritage.org/vbulletin/showthread.php?p=40770#post40770

Also, the link to Gordon W's prescription in the first post here:

http://audioheritage.org/vbulletin/showthread.php?t=7365

And, finally:

http://audioheritage.org/vbulletin/showthread.php?p=24539#post24539

[Zilch]

I plan to research Zilch's posts regarding that implementation as I have the L200 cabs and a pair of 2235s to use as subs underneath my E-130(paper dustcap) and 2404H project.Easy. Mount woofer, 4" plumbers' plug in one port, kick back and enjoy.

If you decide they're "Keepers," add a triangular brace from above the woofer to the rear, and cross-bracing. It's a big cabinet with no stock bracing.

For higher tuning, just unblock the second port. My simple Fmin measurements of the resultant tunings are here:

http://audioheritage.org/vbulletin/showthread.php?p=93134#post93134

I've since learned how to measure ported box tuning more accurately, but that's the "ballpark." :thmbsup:

[duaneage]

Designing for response based on box tuning ignores the effect the room has on the system. Room gain can be significant, adding as much as 10DB to the low end in the right room. YMMV but at low frequencies placement is everything. Corner loading in a large room may increase the low end enough to remove the need for equalization. There are programs out there that model room nodes, I can't think if any free ones at the moment.