DIY JBL 4344 project

[JBLP]

Thanks guys
Odd: you're always there with an answer. Thanks for following.
THE Mr Widget: thanks for your encouragement. I'd like to come back to you at the time I have to do the crossover.
George: don't give up the refurbishment, it's the best therapy...... Yes, still a lot to be done. No rush!!!
Hey Martin: I know, it will be a fight. I'd like to have a splinter of the original and send it to a paint shop to scan.

Stuffing inside, question:
Is it there, to absorb the inside produced sound and is it "the more absorption the better"?
I have some absorption material which they use in offices (interior) to kill the reverberation / echo / resonance.
It seems to have the highest absorption factor of all; a lot more than the glass wool.
Is this better to use?
Txs, Paul

[NickH]

I'm seriously thinking about building a pare of these next. Though they won't look anywhere near as good as yours.

Keep up the good work. What to build me a pare next, lol.

[ivica]

Thanks guys
.................
Stuffing inside, question:
Is it there, to absorb the inside produced sound and is it "the more absorption the better"?
I have some absorption material which they use in offices (interior) to kill the reverberation / echo / resonance.
It seems to have the highest absorption factor of all; a lot more than the glass wool.
Is this better to use?
Txs, Paul

Hi JBLP,

Wonderful work.
Too much absorption would reduce bass-reflex contribution to the frequency response, as the driver alone is almost not 'emitting' sound near box resonance frequency.
I think that the best would be almost not to absorb the frequencies under (say 50Hz), and the absorb all over, but such is not possible in the reality, as absorbing low frequency is very difficult job.
On the attached figure, there is idealized FR response, and the possibilities for standing waves, (depending on the dimensions especially where Lambd/2=one of the internal size, here it is assumed that Dim=0.6m = Lamda/2 ==> Fr=344/(2*Dim[m]) = 172/Dim[m]= 287Hz and its multiple...)

[JBLP]

Hey Nick, always good to hear from you. Build them! I will support you (mental.....).

Thanks Ivica, I'm a building engineer, I can follow a lot..... but this one...... you have to help me.
Dim is content? 0.6m = 0.6m3?, 600 ltr?
Then what is Lamda?
Did you calculate standing waves for a 600 ltr cabinet with the outcome of 287 Hz?
Can I read from your figure how much to stuff the cabinet?

Building sample:
A lot of rooms have a acoustic problem; too long echo's.
To take action you have to measure the echo time in the room. A norm for offices is 1.0 seconds.
When you measure 1.7 sec, you can calculate how much m2 of acoustic absorption material you will have to place/hang to bring it back to 1.0 sec.
The m2 is also depending on the absorption specifications of the material you want to use.
Samples:


So:
Does something like that exists for loudspeaker cabinets?
How much absorption material to use? What figure / norm I have to aim for?
Txs, Paul

[JBLP]

Fixing the 2425 support and preparing the back panels.

[JBLP]

[Krunchy]

What a labor of love... very nice.
Most likely the most beautifully finished interior of any JBL extant... factory made or DIY!
Widget

I was thinking the same thing as I looked at the progression. Great Job!

[NickH]

Jblp I don't think your in the diy realm. Your speakers look like there professionally made.

I can tell by your work, your very meticulous in your task. You've put a lot of thought into what's and his's of your build.

Once I finish my field coil conversion of my 2440's then I probably will attempt an altered version with 2" drivers.

I just have to have my frames coned and source 2 of the 10 inch drivers.

[JBLP]

RAL5007 is an often suggested blue for the 43xx series, but ......
My feeling was that THE blue was somewhere in between the RAL5007, RAL5012 and RAL5015.
RAL5007 is too purple.
RAL5012 is too light but has this "vintage" tone.
RAL5015 is too blue.
So I started mixing and tried several proportions.

Please note that a digital camera is fighting to keep it real! When it sees too much blues it wants to correct it.
RAL5007 even looks more purple next to other blues.

[Odd]

You should take into account that the blue face JBL monitors were in production for many years.
There are several varieties of blue on the original.

You must make a choice.

[JBLP]

Then I selected the 'best' three options;
- nr 4: 1/2-5007, 1/4-5012 and 1/4-5015,
- nr 5: 1/2-5007 and 1/2-5012,
- nr 7: 3/4-5007, 1/8-5012 and 1/8-5015.

I got closer but,
nr4 is still too blue,
nr5 is still too light and
nr7 is still too purple.

Too blue --> less 5015.
Too purple --> less 5007.
Too light --> less 5012.

I narrowed the triangle but had to go in between again: nr13: 0.6x5007, 0.3x5012 and 0.1x5015.

Of course this is debatable and disputable....... it is an effort and maybe the blue I like.......

[JBLP]

Hey Odd.
I saw that picture before and I like that blue.
My nr13 is close; the digi camera made it more blue.
Your picture is with a lot of brown (wood) in it so there the blue is maybe more like it is in reality.

[JBLP]

The cabinet is on going and have to start working on the drivers.

I have a set 2405H in bad cosmetic shape and with a not JBL diaphragm.
See pictures:

[JBLP]

I also have a set 2404's with JBL 2402 diaphragms.
The magnet looks really good and clean.

My question:
Can I use the 2404 magnet, the 2402 diaphragm and the 2405 alu finishings (after repainting) to get my 2405 set?


See pictures:

[JBLP]

I'd like to cut the vents and put them in.
Used your LINEARTEAM.DK vent calculator.

I deducted all the bracings, the LF-enclosure and the drivers from the volume of the cabinet:

Cabinet
58,2	100	33,2	1	193224	193,22	liter
minus
3,14	219,9289	22,5		15537,98	15,54	liter
5,5	2,8	33,2	9	4601,52	4,60
5,5	2,8	47	2	1447,6	1,45
5	2,8	20,5	2	574	0,57
1,9	7	54	1	718,2	0,72
1,8	7,5	33,2	1	448,2	0,45
1,8	4,9	58,5	2	1031,94	1,03
2	1	100	2	400	0,40
2	1	58,5	3	351	0,35
2	1	69,5	2	278	0,28
2	1	33,2	4	265,6	0,27
2,8	2,5	60	1	420	0,42
2,8	2,5	53,5	1	374,5	0,37
drivers					7,50	(4344 Active Project)
					33,95
				Total:	159,28	liter
LinearTeam.dk		159	liter
		30	Hz
		2	number of vents
		10,36	dia vent
		27,762	length vent

Odd: how accurate will this be? I still have to test later?
Thanks.

Strange: when I fill in 159 liter, 30 Hz, 1 vent, 5cm dia -----> Length is calculated to be 0.456cm....... So why to make two big vents?