Building a kind of 4691 JBL - crossover questions .

[BeDome]

I am in the middle of re-upping my Home theater system.

I have all the products available to build a sort of (custom fit to install space) Cabaret 4691 plus a super high 2405 slot tweet for extended range.

I have one already built to test how the squashing the box to my spatial needs affects the low frequency performance and honestly it kicks all kinds of MAJOR ASS (!!!!!) just fine in the range below 2K.

I have tried to analyze the crossover and I really have no need of the functions outside of just setting it and forgetting it.

Does anyone see any trouble with just using the two caps and the coil (makes it super simple!) and totally skipping all the other functions?

I will end up with a cap in series with the horn driver at 8 microFarads, a .75 milliHenry shunt coil across those terminals.

Then it seems that a 3 microFarad goes in as a shunt across the E140 to limit its High Frequency response.

I will never bi-amp these boxes, so all the other connections just add to confusion. I plan to use a single cap at 6dB/octave to the super tweet in parallel with the horn driver set for about 7K or 8K. (want to keep it protected if I decide to really crank up Chickenfoot or something)


I am still figuring out the L-pad ... or if I really need it. I might just use a static Resister in series, but not that far along yet.



Am I really missing something, or is it truly this simple?

[martin_wu99]

I am in the middle of re-upping my Home theater system.

I have all the products available to build a sort of (custom fit to install space) Cabaret 4691 plus a super high 2405 slot tweet for extended range.

I have one already built to test how the squashing the box to my spatial needs affects the low frequency performance and honestly it kicks all kinds of MAJOR ASS (!!!!!) just fine in the range below 2K.

I have tried to analyze the crossover and I really have no need of the functions outside of just setting it and forgetting it.

Does anyone see any trouble with just using the two caps and the coil (makes it super simple!) and totally skipping all the other functions?

I will end up with a cap in series with the horn driver at 8 microFarads, a .75 milliHenry shunt coil across those terminals.

Then it seems that a 3 microFarad goes in as a shunt across the E140 to limit its High Frequency response.

I will never bi-amp these boxes, so all the other connections just add to confusion. I plan to use a single cap at 6dB/octave to the super tweet in parallel with the horn driver set for about 7K or 8K. (want to keep it protected if I decide to really crank up Chickenfoot or something)


I am still figuring out the L-pad ... or if I really need it. I might just use a static Resister in series, but not that far along yet.



Am I really missing something, or is it truly this simple?
Great!you are building a more punchiful L300 or 55000:D

[BeDome]

More punch is good for a home theater system! Right? Gunshots, car chases, explosions, women screaming, etc. :bouncy:

I had not thought of the parallel you mentioned, but I need to use what I have available and E140s, 2370s, 2426s, 2405s, is what I have sitting around gathering dust, BUT no more!!

Any tech-heads out there who can offer guidance on my crossover question?

[BeDome]

I went with a simple slot loaded enclosure (slot loads the corners of the room!), tuned to around 42 Hz, which really seems to support the E140s quite well. My receiver is set to cut them off at 50Hz and defer to my dual 18/quad 15 (biamped dual mono) subwoofer system at that point.


I L-padded the horn (using the Cabaret style specs for the XO) and added a simple resistor, cap and coil for the slot super tweet.

I intend to find some "JBL Blue" for the front face, just to suit myself. :D

Still figuring out a grille, but NOW I have my old JBLs inside and SMOKIN' on my movie rig!!

[BeDome]

As far as I can tell, I have my enclosures tuned to 38Hz (somewhat bowing to the needs of my original E140 drivers), but after setting in a pair of "McKenzie recones" (E140s reconed as 2235? We'll see!) built around some blown E140s, using 2235 materials, I am amazed at how much MORE "bass presence" I have on hand.

Remember, this is a Movie/Home Theater rig. Not a studio rig or a sound reinforcement rig. It just mainly whispers in a 24 by 16 by (8 to 12 slanted ceiling) foot room.

My receiver is now set to send all program bass to all the drivers. The center is dual E110s with 2370/2246 mid/tops and the surrounds are E110 with 2402s. (Sub is somewhat complicated, but substantial.)

(So, except for my newly enhanced fronts, I have a "Cabaret Style movie rig." to listen to. But honestly, I like to rock out at times and this works well.)

After adding these recently reconed - E140/2235- ish bombs to the mix in front left and right, I am amazed at what they sound like with the most demanding of program material.

I have used JBLs for many years, since these drivers were new - whispering them and driving them into compression when needed, but just whispering this system (movies or music) is such an amazing thing!!

Even though I am using a non standard enclosure (my best guesstimate=3.6 cu ft for the low driver, tuned to 38 Hz via slot port.) these seem to rock my whole house if called upon, but used sensibly (some accounting for WAF) they simply purr.

Very pleased!!

Still have to grille them, though. (low priority to me, but WAF is becoming a factor! She just can not have blue speakers in her house ... what ever.)

[BeDome]

For SOME reason I wrote 2246 as the model of the compression drivers used on my 2370 horns.

I am sure that combo would NOT work very well.:D

Anyway, the drivers are actually 2425Js mounted on 2370 horns, Left, Right and Center.

[BeDome]

After some many weeks of listening, I am not going to completely Dis' the McK recones. They sound great, but after laying in some original 2205s in my fronts L&R (Yep, bought these 2205s thirty something years ago and probably abused them some, then set them aside when I replaced them with stronger, more current drivers circa 1981 - as far as I can recall, original 2205s were AlNiCo, but I wait to be corrected).

I thought that the E140s would be the best match for the rest of the system, but these old puppies are amazing! Just as low and more smooth toward the XO point. I think I have found how my lows are going to be in my movie rig.

I am only two weeks in with this latest version and I have played many movies (coldest days in twenty years last week; we stayed home and watched movies for three days), some old jazz, soft jazz (my fifteen year old son's favorite, since he learned to play sax) some classic rock, modern rock, classical, then TOTAL rancor with Lord of The Rings (lots of nice lows), Man Of Steel, Pacific Rim, Master and Commander and so many more chosen for detailed soundtracks.

My thinking is that as the low driver approaches the XO freq, the E140s were still rising in response, but the 2205s are almost flat from lower to high enough to reach the horns without producing an ounce of shout. No problem either with the box tuning around 38Hz.

I roll off my fronts at 40Hz now from my receiver. Plenty of LFE power to call upon; I do not need any real lows from my fronts, but 40Hz is pretty good, compared to many Home Theater rigs, these days, which often use a "so-called" subwoofer to reproduce everything below 80 or 150Hz.

So, now 2205, 2425J/2370, 2405 (6Db/Oct @ around 10K). Still think I need to find the right "value" to cut off the mid horns a bit lower than they are right now, using a single cap on the super tweets. I plan to do something similar with the high cut off on the 2370s on my center channel. It will be another adventure, since the center has dual E110s below the 2425j/2370

Just now, I feel cool.

[JuniorJBL]

Sound like fun!! :D