Sub Question....

[hapy._.face]

2235 likes 5 cu ft and 2 ports at 4" ID and 11" in length for an ideal 30Hz-28Hz tuning. Do what you must to work your way into this- those 35's will sound like completely different when you give them this tuning. Believe me- I tried several different ways and got tired of the "one note" BS. 2235's at 30Hz makes them open up and become more...well...muscial. I used old L200 cabs for test beds and I simply added enough internal bracing to offset the volume to equal 5 cu '. I popped in a couple of ports from parts express (flared 4"ID cut to 11" long) and presto- instant focused bass.

[Zilch]

See line 8 here for 30 Hz tuning of 5 cuft. enclosure:

http://www.jblpro.com/pub/manuals/enclgde.pdf


Any tuning below 27.5 Hz in your 5+ cuft. enclosures, which is where I have my 2235H's similarly aligned and tuned, will require derating of the power handling capacity of the drivers.

Your present 23 Hz tuning cuts it in half, as I indicated above.

You may indeed find that raising the tuning frequency of your bass boxes will alter the total system performance in a desireable manner....

[Mr. Widget]

So we have a pair of 2235s in vented enclosures a pair of midbass horns operating from 100Hz to 500Hz, a pair of compression drivers running from 500Hz to 6KHz and tweeters above that....

There has been a lot of discussion about box tuning... that's fine and can be important but it seems premature to me. I think the discussion should be about system integration and not just focused on the subs... unless your horns are quite large, they would probably be best crossed over at 120Hz or maybe higher. I think with the system you are describing you need to think of the 2235s as woofers and not subs... they should be part of each speaker cluster. If you are not getting good bass out of both speakers you may need to rearrange the room and/or position of the speakers so that you do.

You should buy a crossover that allows you to vary the crossover frequency and ideally the slope too... at the very least you should get one that allows tweaking of the crossover knee as well as frequency. There are several on the market that should get the job done and many that may be had for under $200 on the used market.... in all likelihood they will be of the pro audio or prosumer variety so you may then discover ground loop issues but that will be the discussion for another day.

Sounds like you will be having many hours of fun and frustration ahead.


Widget

[lpd]

See line 8 here for 30 Hz tuning of 5 cuft. enclosure:

http://www.jblpro.com/pub/manuals/enclgde.pdf


Any tuning below 27.5 Hz in your 5+ cuft. enclosures, which is where I have my 2235H's similarly aligned and tuned, will require derating of the power handling capacity of the drivers.

Your present 23 Hz tuning cuts it in half, as I indicated above.

You may indeed find that raising the tuning frequency of your bass boxes will alter the total system performance in a desireable manner....

I'm wondering, rather than adding another four inch port if I could use a single four inch port at 5 inches instead. I suppose at loud volumes it may "chuff" abit, but I'm not a large volume fella. Moving the one 2235 to a different corner really cleaned up the bass, although I'm going to tune the boxes to 30hz, and then pick up a better xo and post my thoughts.

Yes Giskard, lots of frustration, but with each discovery I feel I'm one step closer to the ultimate system. BTW I've tuned the 2235's at 140hz which creates an overlap, but I might experiment with the midbass xo and instead of allowing it to rolloff I'll cut it off. Any thoughts?

[Zilch]

I'm wondering, rather than adding another four inch port if I could use a single four inch port at 5 inches instead. I suppose at loud volumes it may "chuff" abit, but I'm not a large volume fella.

Yes, especially O.K. for testing.

With single 4" ports:

27.5 Hz - 5.0"
28 Hz - 4.7"
29 Hz - 4.1"
30 Hz - 3.6"

[4313B]

Any tuning below 27.5 Hz in your 5+ cuft. enclosures, which is where I have my 2235H's similarly aligned and tuned, will require derating of the power handling capacity of the drivers.

Unless you apply boost at the tuning frequency of the box. Applying the boost also serves to attenuate response below tuning at a faster rate thereby adding protection to the transducer during unloading. Of course then you have to accept the increased group delay. Nothing is free. If you go with the old 20 Hz tuning and boost there will be a power sag in the 25 Hz region, but tuning and boosting at 25 Hz will handle full rated input as you know since you have a B380.

Yes, especially O.K. for testing.

With single 4" ports:

27.5 Hz - 5.0"
28 Hz - 4.7"
29 Hz - 4.1"
30 Hz - 3.6"

All of which should be measured afterwards since we have no clue as to how well you can build a box and minimize losses. Some of those old JBL boxes can have a loss factor around 5 or so. JBL TOTL boxes (250Ti, 4430) are up around 10. Mine usually push 14. (The higher the number the lower the loss, 3 is junk, 7 is typical). Basically cut the ports long to start with just like those old 60's and 70's manuals state. The point is, this stuff really needs to be measured. The math is neato, and BB6P comes surprisingly close consistently well, but if you underbuild or overbuild or use some kind of goofy fill you need to adjust accordingly.

I think with the system you are describing you need to think of the 2235s as woofers and not subs...

True. You might even consider pulling those mass rings and going with real subs. Put the resulting 2234H's in smaller boxes tuned higher. They have more kick and are more efficient. As has been posted several times - Mass rings are now "out of favor", 2234H's with EQ are probably the most desirable use of that transducer, 2235H's and 2245H's got beat silly when used as dedicated subwoofers. These concepts are all verifiable by examination.

Yes Giskard, lots of frustration

I think you mean Mr. Widget in this particular instance.

I suppose at loud volumes it may "chuff" abit, but I'm not a large volume fella.

Neither am I. The single 4" port has worked for me personally since day one. I never use it for other people though. As for high volume and room response - sometimes people get their woofers placed in a null and start cranking the gain. It might not seem real loud but then an errant tone on some CD or DVD comes along and damage occurs. Point being, watch your cones for physical stress during demanding passages after placing them and be familiar with your source material and it's effects on your system.

[Zilch]

If you go with the old 20 Hz tuning and boost there will be a power sag in the 25 Hz region, but tuning and boosting at 25 Hz will handle full rated input as you know since you have a B380.

Indeed, and lpd's 5234A has boost filter capability built-in, at 20 Hz, at least, without modification. We've earlier and elsewhere discussed how to change the frequency of that, but for now, i believe it's beyond the realm of resolving the immediate difficulty.

Regarding which, I view Mr. Widget's observation as critical. The goal of using the 2235H's as subs is an apparent misdirection. What's needed instead is a capable low-frequency system physically integrated with the mids and highs (as opposed to spread around the room,) and additional subs, if then still desired, separately addressed....

The math is neato, and BB6P comes surprisingly close consistently well, but if you underbuild or overbuild or use some kind of goofy fill you need to adjust accordingly.

Yes. I'm just posting BB6P calcs here. They should best be viewed as starting points or "guidelines" for experimental determination of final tuning. I currently use Woofer Tester II, plumbers' test plugs, and a calculator for actual cabinet tuning measurement:

http://audioheritage.org/vbulletin/s...ad.php?t=10129

[lpd]

Ok guys, I cut down the port size to 4.75 inches and returned to experimental mode. After a few hours of placement attempts I hit the spot. Seems two subs are trickier to place than a single, not sure why. Bass is really smooth, transparent, and the boom is removed. It took a few to get used to as the bottem boom is gone, but its way smoother and easier to listen to. I'm not sure abot measurements, I am borrowing a measuring device from a friend at the end of the month and perhaps I can even improve the situation.

Next is a better XO and power amp for the subs.

Again thanks for the help and the reading material!!!

peter

[4313B]

Seems two subs are trickier to place than a single, not sure why.

Me neither. I've never had any problems but we can all pretty much guarantee that someone somewhere is going to have a different experience.

[lpd]

Me neither. I've never had any problems but we can all pretty much guarantee that someone somewhere is going to have a different experience.

Unfortunately I have a room of "node hell" and placing any speaker system in it has been a task. This is my first attempt at a home build/diy. What I did was place one sub and then fine tune for smooth bass easy as pie. The second sub not so easy. Seemed really dry where I had it, but I moved it to another corner and found the perfect placement for it. Bass is strong on both channels and really smooth. Now I'm going fine tune with a xo ect. I have researched that the 5234A is not really recommended for a xo. Will it suffice for subs? How do I calculate parts to build a 100hz card for it?

[4313B]

The biggest problem with the 523x networks is the top end. They're pretty bad for home fi-fi use. They were pretty bad back when they first came out and nothing has changed. The low pass still works for subs. Frankly, you'd be better off ripping the guts out like I do and building a new low pass based on something like the BX63A circuitry. You can add in or leave out the bump filter. I posted all about that at length at one point but it may have been one or two forums ago. Another option would be to build one of Rod's projects in the 523x case. I'm real big on building my own active filters, have been since the early 80's.