"Big Mo".

[Izzy Weird]

(Rob asked a question about the “rig” in my avatar. This is a project I will be starting soon. )

“Big Mo” (short for Big MF ), is a 20-year-old sound system that is badly in need of some maintenance and upgrades. But it still has good sound and loads of headroom. It is 4-way amplified.

The 2395 lenses have 2425H 1” drivers, the HF is two 2405 (as you can see). I forgot which driver I used for the 15” low-mid. I have already replaced the sub and low-mid amplifiers. The two upper channel amps are Hafler 120s, low-mid is a Crown XS500, sub is a Crown CE4000.

I have a JBL DSC280 crossover ready to add, I’m using an Ashley now. The drivers are all JBL, the wood horns are EAW, but I have an old pair of 4560s I may switch over to.

I want to upgrade from the two B460 subs, probably with four 18” drivers, but so far I haven’t found the solution.

Windows and doors of the room have been insulated and boarded up, and heavy insulation has been added above the hung ceiling too.

I have plenty of time to upgrade this system, and I’m hoping to get some ideas here. I’ve been a JBL fan since I was a child. It sure is great to find so many JBL enthusiasts in one place.




Izzy

[Robh3606]

Very Nice!!


Bet that kicks some serious butt. Thanks do you have some pictures you can drop up. I for one would like a closer look. Upgrades for that?? Well you could always drop 2" drivers on the big mid horns. The 18???? 2242 comes to mind but me I can't imagine needing more than a pair of those beasts. It must get down right scarry with the right source material. 2235's impress the hell out of me. Got to hear a pair of 4350's in what was a small room for them and had my ears pinned back. The lowend was to die for. Just effortless clean and articulate with tons of raw power. Listenning to the drums in James Taylors Gaia was like getting shot out of a cannon. Great Fun!

Rob

[Izzy Weird]

Back then the best 2” driver was the 2441, and I didn’t really care for it as much as the 1” drivers. It may be blasphemy here, but it might be interesting to try a pair of TAD 2” drivers. (I sort of view TAD as “Japanese JBL” anyway.)

One thing I love about front-loaded low-mid horns is the way they reproduce the impact of drums.

I’ve been looking at a number of new JBL subs, two 4642A, or two ASB6128V, or even four 4645C.

The mid-high units really need to be up higher in the room, I’m going to experiment with 24” x 48”wire shelving.

One thing about a large system in a small room is the issue of safety. I have very conservative fusing on all of the drivers. Recently I accidentally opened a mic in the room, and although the feedback was loud, the 1 amp fuses on the 2425 drivers popped right away. As a system like this ages, the chances of loose connections or amp failures probably increases. I want to add a safety switch that can be pulled quickly, and a relay that drops out at the first flicker of the power line. I used a similar system when I ran Big Mo on a generator in California.

Trivial Aside: In California the mid-high units were hung from the ceiling with chains. In the 1989 Loma Prieta earthquake these speakers were swinging so violently they busted holes right through the drywall.

Izzy

[speakerdave]

. . . . the wood horns are EAW, but I have an old pair of 4560s I may switch over to.

When it comes time to part with those EAW horns, please let me know.

Thanks,

David

[Steve Gonzales]

Man when it gets time to get rid of the B460's, get ahold of ME!

[Nightbrace]

Me too!

[Izzy Weird]

Me too!

Trying to get to 195 dB, not quite there yet .

There are few (single band per channel) passive-crossover systems that don’t clip on loud passages. (If you don’t believe me, put a scope on it. )

The ability to get a clean 120 dB SPL is wonderful. The ability to handle wide dynamic range, and really loud crescendos without “mushing out” is great. Even if one rarely uses the available headroom, it’s so nice to have it.

Izzy

[Mr. Widget]

Wow... I can't take it anymore. When I was in my early 20's I had a variety of large JBLs that were multiamped including a Marantz 510. At one point I borrowed a calibrated SPL meter and fired up the system. It was putting out 127dB at 1m. Back then we wore those silly pants with extra fabric around our ankles... bell bottoms as I recall... anyway, they would literally flutter at 20 feet.

Moving forward almost 30 years I still like to have unlimited headroom, but I really doubt I have hit over 110dB more than a couple of times in the last decade. Shockingly I can still hear quite well... my eyesight is becoming annoying, but thankfully I can still enjoy the nuance and detail that fine speakers are capable of producing.


Widget

[Mr. Widget]

Back then the best 2” driver was the 2441, and I didn’t really care for it as much as the 1” drivers.

If you have the chance give them another whirl... in all of my comparisons there is no comparison. The lower distortion is a significant improvement. Especially at higher SPLs.


Widget

[Izzy Weird]

If you have the chance give them another whirl... in all of my comparisons there is no comparison. The lower distortion is a significant improvement. Especially at higher SPLs.

Widget

Thanks a lot for the tip. I've been noticing a lot of discussions, and even freq. response plots of 2" JBL drivers here. I'm going to be watching for more discussions regarding these drivers.

Given the 15" drivers below, I should probably be crossing over lower anyway, and I could probably do that with a 2" driver. For the past 10 years or so, I have been using 100, 1k, and 10k Hz as the crossover frequencies. The Ashley XR88/12 is a 12 dB/octave model.

I bought the DSC280 direct from JBL for half price, so I'm not married to it. I could use a BSS instead. One thing I want to try to do with this project is get the drivers positioned so I can get better "time alignment". Positioning the 2405 in relation to the 2395 horns is the part that has me baffled (so to speak).

Izzy

[John W]

I have a pair of 2440s mounted on smith horns that I would be happy to bring by and swap into Big Mo for a taste-test, since you are in the neighborhood.
They are my babies and I'm not sure I want them peering over the maximum db abyss, though.

[norealtalent]

OMG John, don't let me near them unless I'm wearing a bib. They're beautiful!

[Mr. Widget]

Those are pretty... we may have another 2397 convert.


Widget

[scott fitlin]

I bought the DSC280 direct from JBL for half price, so I'm not married to it. I could use a BSS instead.

Izzy

Pssst, hey Izzy, yeah you, come here, I want to tell you something!






That JBL DCS280, it is a BSS! Its the BSS FDS-388 wearing an American suit!

[scott fitlin]

John, those horns look really great!