JBL Dynamics Project - Initial discussions

[Bigyank]

@hjames take a look at DBX Driver's. Not sure if it will fit the task but they can be found relatively cheap.

 

[donprice]

So...how do you turn the spare diaphragms into mid drivers like used on the XPL series? Off topic...

 

[Nyjblbob]

test leads while I played a 200Hz tone to be sure it was centered

I never heard of anyone doing that with an 8 screw diaphragm, with centering pins.
or do they not have them?
Was that in the instructions with the new ones?

 

[hjames]

test leads while I played a 200Hz tone to be sure it was centered

I never heard of anyone doing that with an 8 screw diaphragm, with centering pins.
or do they not have them?
Was that in the instructions with the new ones?

Nope - the directions had some errors that did not relate to my drivers - stated 4 cap screws instead of the 3 I have,
and a different wrench size for the push-connectors on the cap. No centering pins that I could see, old or new.
I did google before I started and a post from Edgewound said test tones was a way to go.
(Who am I to argue with Ken - he's a proper certified JBL tech!)
https://www.audioheritage.org/vbulletin/showthread.php?43104-2451h-installation-of-2450SL-diaphragms-centering&highlight=Install+Diaphragms?

 

[Nyjblbob]

Ok that explains it.
I have only the changed out the Phragms on my 2440's and 41's
and he states the older Alnico drivers have the centering pins

 

[Riley Casey]

The centering on the 45 is accomplished by the slight recess that surrounds the diaphragm ring although just as with the older drivers with the pins the real centering is done with a sine wave. A few 2441 diaphragms I had back in the day had to have the mounting pin holes on the plastic ring reamed out to achieve the best, buzz less centering.

 

[Macaroonie]

Right , so whats in the Valencia boxes ?

 

[hjames]

Right , so whats in the Valencia boxes ?

The Altec 15 woofers, which have some mods by my guru friend so it hits deeper and harder than stock.
Basically Heathkit branded Altec Valencia drivers, but the tweeter control is turned down so it’s
mostly acting as a woofer box. Placeholders for now. But playing some old Mayall now (Back to the Roots) and they are sweet.

Update - here is a picture from my 2018 build thread, showing the original Altec woofer on the right
compared to the modded Woofer on the left. Its got some punch to it!

 

[markd51]

The Altec 15 woofers, which have some mods by my guru friend so it hits deeper and harder than stock. Basically heath Valencia drivers, but the tweeter control is turned down so it’s mostly a woofer box. Placeholders for now. But playing some old Mayall now (Back to the Roots) and they are sweet.

Nice choice of tunes.

 

[powerman]

The JBL 2403/076 and 2404 will also work with that Nelson pass circuit. Also the 2407 is a great ring radiator too.

The 2404’s usually can be had for $400 a pair. You just have to make sure they are not the H-1 models.
The 2407’s are a great driver also but you do not see too many 2407J’s up for sale.
The BMS 4540 is also a nice match

 

[hjames]

The JBL 2403/076 and 2404 will also work with that Nelson pass circuit. Also the 2407 is a great ring radiator too.

Yep - but most of the JBL Ring radiators have gotten stupid expensive in more recent years,
I believe they are all out of production currently, so I'll probably steer clear of them.
Besides - the Great Heils are paid for, are here, and are doing well for tweeter use for me now.

 

[Macaroonie]

Whoah horsey. So , inside the Heathkit boxes you have a passive X/O with the tweet turned full off.
Hence the bass filter of the NP network is now feeding a full range network.
I would strongly advocate getting the 'Spanish ' network out of the equation , hook up directly on to the Altec 15. You will want to check whether it's an inny or an outy although you can flip that at the NP end.
Better bass awaits you.

 

[hjames]

Well, I have collected the parts I will need,
but I have stopped at this point. I STOPPED.
I am happy to stay at Stage 1 for now, it all sounds good, and I can relax.

Until the Heath/Altecs are sold, the Von Schweikerts are sold,
and the JBL L212s are sold, I have no room to make the next step,
so there is nothing more for me to do right now.

There is a plan and a method to all this, even if you hadn't seen it yet.
The next stage is sorting out the woofer boxes. That will come when it's time.
I'll need a place to mount the 2216Nd woofers before I can "put them together."

Sweep, waterfalls and more will not sell the speakers nor give me room to work.
That can all come later when something can be done with it.
No need to rush any of this, it will happen when it's time.
But thanks.

Put them together, do a sweep, waterfall plot, see what you've got.
I know that Nelson wrote that he struggled a bit with polarity on his crossover design, tried it a couple of ways before he was happy. It truly is art after all of the science is applied.

If you've never attended a DIY speaker club meeting, you're missing a treat.

 

[hjames]

Another box enters the room ...
Compare the difference in finish and relative size of the Heathkit AS-101 (Valencias) and the Heathkit AS-1348 on the right.
Surprised to find the top of the 1348 narrows to just 10" deep,
Its overall dimensions are 24 x 38 x 15" ... its a non-conventional shape.
The AS-101 is a traditional box - 27 x 32 x 19.75 inch

The AS-1348 is a 3 way design with a rear facing, slot loaded 15" driver,
and under the top front grills, two 5" mids, and 3 dome Tweeters in a semi circle array.

Overall, a very attractive MCM looking design

 

[Nyjblbob]

Are you considering them for the JBL ND/ Smith project?

 

[hjames]

Are you considering them for the JBL ND/ Smith project?

The new Heaths? I honestly don't know yet. The box is more attractive than the moroccan/Pecan finish of the Heath Valencias. Its a nice MCM design with decent bass response.
The bad part is the top is 24" wide but narrow; no place to hang the horn/drivers up there.
Also, I haven't measured the Woofer area to even see if the 2216Nd will fit inside.
So I have no idea how this will move forward.
I have offers to help build new woofer design boxes of Baltic Birch, and that may be the final direction.

But I have a potential buyer scheduled to demo the Valencias to on Thursday;
so if that is successful, once they move out I can focus on the possibilities.

 

[hjames]

Yep, like I keep saying "I wanna sell the Valencias (and the Von Schweikerts, and the JBL L212s)".
We'll see ...

And as of 4PM yesterday, the Heath Valencias issue has been resolved, at least!

 

[hjames]

Very cool concept, Mac! I've seen builds on the Lansing site using kerfed plywood that can be curved like that.
I like the look of that a lot!
And, of course, I did get that new pair of Heath speakers with the rear-facing slot loaded 15" woofer.
Not real excited about the mids and tweeters concept - but I haven't been focussed on much
except moving the Valencias out this week (and clearing all the leaves we get in fall!)
Well, I'm headed off shortly for opening day of the Capital Audio Fest across the river in Maryland -
who knows what interesting things I'll see and hear in the 90 rooms its scheduled for this year!
Talk back to you later.

Hi Heather. Given that you were pondering having bass cabinets made I came up with an idea that you might like.
The most immediate problem aesthetically is the lip on the front of the Smiths , it doesn't fit well with a stock cuboid box.
Then I remembered these

View attachment 2711256
These are B&W DM70's from the early 70's. The top doo dah is an electrostatic array.
So , what if you took the curve of the Smith and had a cabinet made as a floor stander in the above form but to match the dims. of the Smith.
You will be looking at this in horror of course , how on earth does Mac think I can get this done ( even if I wanted to )
Ah well lhere is a way. In the US you can buy pre formed curved plywood
It comes in a variety of curve radii.
I can locate the vendor , I have a bookmark somewhere.
Done well it could look brilliant IMO

 

[Macaroonie]

I've done more CES shows that would last a lifetime. Cacophany usually.
Have fun.

Here's a teaser. The curved ply is steam and pressure formed , ie no kerfs.
In other words its structurally sound.

 

[hjames]

I've done more CES shows that would last a lifetime. Cacophany usually.
Have fun.

Here's a teaser. The curved ply is steam and pressure formed , ie no kerfs.
In other words its structurally sound.

Woah! A big steam box is probably beyond our capability!
But it was a good audio show!