JBL-NOT!! - DIY 4351 Studio Monitor

Unbelievable! You are amazing churning out these masterpieces.
Damn fine work:applaud:

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Originally Posted by Ken Pachkowsky

As stated in my first message, you have done a great job and I am sure you will like the speakers you have built. When you’re ready to go to the next level you will find many opinions here.

I have had the privilege of owning factory built 4345's and 4350's as well as Westlakes. The 4345 systems smaller 1” 2421B combined with its longer horn assembly (2307/2308) sounds much smoother than a stock 4350 with (2392?) or whatever that stubby horn is. You can’t compare the sound of a stock 4350 horn to those of the 4345. The difference is staggering. A stock 4350’s horn is simply “ear shattering harsh”. On the other hand the 4345 horn is less harsh, even at high SPL’s.

That being said, a quality wood horn designed for and attached to any 2420/2421B/2440/375/2441 will simply out perform any of these older "stock" horn and lens systems hands down.

Take it from someone who’s owned all the above systems. Once you have listened to a JBL/TAD/Westlake wood horn system, you will never go back to the old standard metal series horns and plastic lenses.

In Ian’s well chosen words “Game over Man, Game over.

Enjoy your new speakers and if I can ever be of assistance don’t hesitate to ask.

Ken

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Gentleman Ken, excuse me for butting in here but, I love the 4350a's I have and have like many of you guys, looked at the various horns, I love JBL stuff $$$$$$$$$.
Now I have a serious interest in the BMs planar horns. Anyone here familar with these animals?
A couple of weekes back I had joked about flipping my 4350s over to gain some floor space so with a very welcome heart I am enjoying these trials and tribulations. also what was the active crossover for the 4355?
No this is the best project that would solve so many problems for me.
Thanks Rissen! very nice! :D

this is a great thread....;)


I like the end result of the vertical orientation......:D

Regards, Ron:)

I've been dabbling with the similar exercise on tranducer arrangment.

Several questions have arisen. I'll toss these out and hope some ight have particular responses to some of the questions and possible solutions I've pondered.

1) What minimum and maximum separation is recommended between the 2235H frames? ... baffle cutouts?

Minimal separation constraints:
a) Structurally, we could always go to a steel wide flanged angle idea between the 2 speakers to maintain cabinet structural integrity, thereby reducing the floor space. This means it might be as minimal as the width of say a 1/2" steel plate custom shaped to maintain a 90 degree (or variant) angle between baffle and cabinet base, thereby also allowing the plate to be drilled and tapped to allow 2235 mounting hardware attached to a common axis. Vibration analysis might be appropriate.

b) Electromagnetically, if we are inducing the same signal from the same source to both 2235Hs, then are we might be increasing some magnetic field interference between the 2 woofers. Negligible perhaps? I haven't quantified this to discern at what amplitudes such field interference might occur. If the effects occur, I suspect they would tend to oblate the field forces on the voice coils hence their respective cones, but perhaps no greater than transient overtones from a universal spectrum of music reproduced on the system.

c) Acoustically, once the sound wave emanates from the 2235s, are their harmonic separation distances one should discourage in the 2235 placements?

Maximum 2235 separation constraints:
a) In constructing a Helmholtz resonator, is the separation distance between the 2-2235H woofers integral to the cabinet depth? .. port distance from the cone? port depth? What eqns are generally assumed/used in speaker design for Helmholtz resonance? I tend to think symmetry wrt to the enclosure volume and the 2235 placement is simplest, but the original 4350/55 didn't respect that perspective, so maybe it isn't significant.

2) Location of the mid-bass with respect to the Bass? wrt the Mid range compression horn?

3) In considering the alignment of voice coils, some recommend aligning all voice coils along the same plane such that the electric signal from the sound system reach the voice coils concurrently and their conversion from electrical energy to mechanical kinetic energy occurs concurrently, thereby reducing timing problems between transducers and signal paths.

If I worry about cutting all my conductors to the same lengths between the electronics/ power amps and the speakers, then it would also seem significant to align the voice coils.

In my case I have 2-2235H, 2-2202J, 2-2440J with 2390 horns (12"deep) +serpentine lens, 2-2405s.

I'm experimenting first with some deeper boxes (24" ext, int 21-7/8") since the JBL enclosure guide recommended 5cuft per 2235 per encl) using some free plywood, playing with configurations, toying with integrating some sand filled walls, and incorporating the mass into cabintry to hold records, some electronics, and all the while playing with some architectural furniture themes.

The 2390s have given me cause to deepen the cabinets, and make some options open to also consider some horn loading on the low end.

If we align the voice coils, I'm afforded about a foot of depth in the front of the cabinets, but if calculated the reduced acoustical impedence of that effort may effect the xover design.

This leads me to quesry what the differential/integral format eqns are describing the acoustical impedence.

Probably enough here for several threads, but they all seem pertinent to the particular issue of a 4351 variant.

If you want to get a nice blue you need to bleach the fronts white and then go over it with a white stain that has blue added to it to make it the blue you want. I used to sand and finish hardwood floors and we would make floors different colors by this method. I know it sounds like the wrong way to go but believe me if you want a nice blue or any other color for that matter it will work well. Use a non-yellowing finish, swedish Glitsa or water base. Make sure the bleach dries for 2 or 3 days before it is stained. The bleach is a two part system.

riessen,

I finally got around to tweeking the biased equivalent bandpass filter on the 2441 today and compared it against stock. I think I've nailed it.

This is real life:

My 4351 project started out with the desire to create a 4350 system that didn't take up as much valued floor space AND to get the mid range and high frequency drivers up into the listening area.

Initially these cabinets were loaded with standard 4350 components, including NOS 3107 cross overs. One thing led to another and I decided to upgrade them to 4355 configuration, lacking the ability to include the factory 3155.At that point Giskard jumped in and offered to develop and build a custom charge coupled version of the 3155.

As of today the new networks are fully installed and the system is up and running as the JBL Gods intended. It may be just my imagination but they seem to have taken on a new image. One thing for sure - the 2441's are now on par and flat with the rest of the components. Running them with the 3107's gave them a dominating presence and at the higher end they literally screamed at you.

I spent a few hours so far listening to everything I could find that I have extensive listening experience with on this system, my 4350's, etc. and their performance is outstanding. It will be some time until I can get my speaker storage room converted back into my listening room. I will then be able to do some serious listening/testing.

All interested should give these new networks a spin - cost is very fair considering all of the R&D time involved and the cost of the high quality components used.

Rick :bouncy:

Always great to see reports on your projects.

Thanks

Ken

http://audioheritage.org/vbulletin/s...t.php?p=110284

It has been awhile and some of the parts in that drawer were substituted with different values to get the networks "right" according to CLIO and LEAP. As G.T. heartily suggested third quarter of last year, LEAP ended up being the fourth Ace in the hand. I really like the way they ended up sounding.

The 3144/3145 bi-amp only networks should be finalized by the end of April at the very latest. There will be three versions. 1st will be with the stock 1" compression drivers and stock horns, 2nd will be with the 1.5" compression drivers (435Be) and subwoof horns, and 3rd will be with the TAD compression drivers on the stock horns.

Rick those speakers are awesome and really deserve the new networks.

BTW Giskard - your networks are truly beautyful.

very goood veryyy gooooood !!!!!!!!!!!!!!!! :applaud::applaud::applaud::applaud:

which material is the polyester cotton and the grill ?
and where do you get this ? how much is ist ?

thanks matthias

Now all that’s needed is special design for the centre channel because that small centre channel above the TV monitor will not cut it against those titanic monstrosities, wow there's enough of those 4351 in that room to sink a battle ship. :applaud:

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Originally Posted by saeman

My 4351 project started out with the desire to create a 4350 system that didn't take up as much valued floor space AND to get the mid range and high frequency drivers up into the listening area.

Initially these cabinets were loaded with standard 4350 components, including NOS 3107 cross overs. One thing led to another and I decided to upgrade them to 4355 configuration, lacking the ability to include the factory 3155.At that point Giskard jumped in and offered to develop and build a custom charge coupled version of the 3155.

As of today the new networks are fully installed and the system is up and running as the JBL Gods intended. It may be just my imagination but they seem to have taken on a new image. One thing for sure - the 2441's are now on par and flat with the rest of the components. Running them with the 3107's gave them a dominating presence and at the higher end they literally screamed at you.

I spent a few hours so far listening to everything I could find that I have extensive listening experience with on this system, my 4350's, etc. and their performance is outstanding. It will be some time until I can get my speaker storage room converted back into my listening room. I will then be able to do some serious listening/testing.

All interested should give these new networks a spin - cost is very fair considering all of the R&D time involved and the cost of the high quality components used.

Rick :bouncy:

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Hello Seaman
I am trying to find a measures CAD Raw cabinet of JBl 4351 .If You has the measurements available, I would be really grateful to get a copy!

My Email : [email protected]
Thank

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Originally Posted by saeman

For a friend in Aladambama I build another pair of my living room friendly 4351 Vertical Monitors. They're pretty much identical to mine in finish and components. They were temporarily parked in my wife's living room until this past Saturday when we loaded them for their trip to Birmingham (she was happy to see them go). At 300# a piece I was glad to finish the loading and kiss them goodbye. On to something new. :bouncy:

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I'm in the process of collecting components of my own JBL studio monitor build. I have been researching the forum for other DIY projects... but when I saw this ... I was in total aw...

Now this project is truely a work of art. -- (See post # 89)

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Originally Posted by Mr. Widget

Nice work!

You've obviously come to a point where you know the sound you like... :applaud:

If I were going the 43XX+ route I think I'd go with a 4345 but swap out the 2421 with a 2441 and a Westlake horn... just my take on it. As for tower configurations, this is what Westlake did. It is a real monster with dual 18" woofers!

Widget

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where would the horn go? outside.