Ian's (& Bo's) 4345 project

[Ian Mackenzie]

Has anyone done any listening tests for crossovers in or out of the Box?

I read in the recent JBL brochures they isolate the crossover from the chambers.

But does this really matter? Are capacitor or chokes more prone to vibration interference?

To isolate the large iron laminate core chokes from each other and still have them in a small inner compartment is not practical so I may mount the parts in a section of MDF and scew down on the rear panel like previously

Any ideas?

Ian

[Robh3606]

Hello Ian

Why not just put them outside?? That's where mine are L pads and all. They are not attached to the cabinets at all. They are wired into panel connectors on the back of the cabinets. I don't know if they are microphonic or not but outside it sure is easier to tweek them.

Rob

[Ian Mackenzie]

More progress,

Today I put the 1st undercoat on the new baffles following a quite chat with our resident JBL paint expert Bo Putman.

The project is coming together nicely, the new stiffeners have been installed on one enclosure and I am pleased to say its rock steady.

My next task is to arrange the rear access panel.

For the sake of completeness, I have decided to mount the crossover in the original location (with the LF inductor mounted remote to the main crossover board). I may mount the smaller elements in a sealed 5mm clear perspex enclosure if removal of the board external to the box offers a subjective improvement

I have posted this image just to put these monitors in perspective, even along side the might 4355, it's still one kick arse loudspeaker don't you reckon. By the way that smaller box atop the 4355 is a 4312, not the 4311 so no rants please.

Ian

[boputnam]

Originally posted by Ian Mackenzie
...I have posted this image just to put these monitors in perspective, even along side the might 4355, it's still one kick arse loudspeaker don't you reckon. By the way that smaller box atop the 4355 is a 4312, not the 4311 so no rants please.

And, atop the 4345 is the meritorious 4301B, my favorite tyke of the 43xx series...

[Ian Mackenzie]

Here are some low res snappy from the Pc Cam, no santa did not bring a new digital camera.

The baffles have been stopped up and undercoated ready for mounting in the main enclosures.

Today I plan to finish the wood work on the main cabinets and then start fitting the baffles.

Ian

[Ian Mackenzie]

The front of the baffles....

[Ian Mackenzie]

I have already starting thinking about grill covers and other projects like amps for the new boxes....(all we need is the fabric)

I was thinking about an X 350 or 600 for the woofers and X 200 for the mids, but that would be about 1000 watts class A dissipation per channel.......may have to install water cooling and a Zen fountain for a primary cooling tower (only joking)

Although I will actually build a X 600 this year as I am a firm believer in dynamic headroom, and to celebrate my visit to Passlabs in Northern Califorina around May 2004.

Ian

[Ian Mackenzie]

Massive isn't it, they weigh 150 Ib each

Ian

[jtgyn]

G'Day Ian,
Nice cabinet work!
From your photo it looks like you have sealed the back of the baffle with clear lacquer. Is there a reason for this?

Regards Scott

[Ian Mackenzie]

Scott,

That is just effects of lighting and surplus dust from the spackle sanding, no lacquer here.

I propose not to paint the interior at all, but chalk all the seams and joints to ensure an absolute air tight enclosure.

In fact discarding the effects of the 3/4 inch fibreglass lining, I'm hoping for low box ( QL=7) losses, as the enclosure is very rigid ad made as per the original design to the letter.

The net effect will be minimal colouration from box resonance and maximum perceived LF extension. I recall from the previous system prior to pulling it down, the bass was tuneful, tight and extended with an effortless quality unlike no other.

Only time will tell...

Ian

Here is a pic of the old box, and the proposed new look..

[Ian Mackenzie]

The final anticipated image (courtesy of Bo Putman)

Ian

[4313B]

The better JBL enclosures measure a QL of roughly 10 to 12. The last 3.4 cubic footer I built for an LE14H-1 came in just above 14. A QL of 7 is pretty typical for mass produced stuff. A QL around 3 is considered worthless junk.

[Ian Mackenzie]

Giskard,

A while ago I did the manual measurements for the 2245h in the existing enclosure albert 10.30 cubic feet at the time.

It was a very tedious measurement following the prescribed method by Dr Bullock as the actual RE of the system is difficult to determine when the woofer is one huge microphone.

I recall vaguely its was about QL=11 but can't find the paper work paperwork, so all things being equal the result should be similar.


Ian

[Ian Mackenzie]

Here's a good question

To Bolt or Not to Bolt?

I am deliberating over how to attach the front panel/baffle to the box proper.

Scews are easy enough to install and hide with counter sink and filler, however it is one way trip usually and I always find regardless of how well you will fill those scew holes they always show through the damm paint. (Also One box caused me grief with screws that broke when I tried to undo them removing the old baffles)

That said I would like the option of baffle removal at least initially in case anything is overlooked or needs changing. So I started looking at bolt on options.

The most elegant solution so far appears to be these Screw-In insert nuts with self tapping body and connector bolt with allen key fitting.

I tested to idea today on a mockup peice of hardwood and MDF board using a trip of soft cell 4 mm foam rubber for the gasket and it worked well.

Any thoughts / ideas are much appreciated.

Ian

Ps I was thinking of covering the bolts witb velcro strips for the grill covers.

[Robh3606]

Even when predrilled I have had screw heads shear right off using my deck gun to assemble things. What a PITA that is. The only issue with either is without glue you need many as the glue is what really hold things tightly together and does the real work. I will be facing the same issue when I make my new cabinets with removable baffle plates. I was thinking a screw/bolt every 4-6 inches. They look like an atractive solution and bolts with a suitable anchor can be torque with greater force without stripping like a scew will do. I for one don't mind seeing hardware as long as it is nicely spaced and not all chewed up. Hiding them under velcro is a good idea.

Rob