my vintage jbl L100T cabinet build

[krell]

hi friends my jbl l100T cabinets are in bad shape and i was decided to build a new cabinet with reduced baffle width and increased height.
i kept the dimensions to match the same internal volume as 3.3 cu feet.
baffle width was reduced in the expense of increased length.
the components are
12" woofer 2214H
Mid104 H2,Tweeter as 35Ti and the crossover is from 100t3.
The front panel is made from 30mm MDF sheet (joining 18mm+12mm),side panels from 36mm and the back panel is 18mm.
port dia is100mm and the length is 106mm.
the port was taken from the original speaker.
i took the 18mm mdf sheets and local carpenter cut the sheets as per my specs.
made two braces with holes for additional rigidity(original cabinet doesn't have bracing).
mid had its own chamber.so separate chamber was made for mid range and glued to the front panel back side.normal wood glue was used throughout the process and patex silicone was used internally for air sealing.
hurricane nuts was used to mount the woofer.glasswool was taken from old cabinet.
double sided tape was used to hold the insulation.
large clamps was used in all stages while curing for better adhesion.
the painting was to be done.
the result is very nice. due to addition of bracing and some little changes in the cabinet volume i accidentally got the less volume than the required volume of 3.3cu feet.
but the reduced volume is helped me to get the more tight bass.
finally i am very happy with the result.





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[rajiv_kulkarni]

They look excellent, may be a coat of paint will add a feather in the cap :clapping:

BR,
Rajiv

 

[krell]

thanks rajiv,yes painting will be decided.still in dilemma either wood veneer or paint.once decided i will go ahead with process.

 

[rohitmusic]

Hey buddy, I think wood veneer is a safer bet. Good paint job finish is a dicy one. veneer would give guarantee + finish of your choice.

Good job on the cab.

Cheers.

 

[krell]

thanks rohit. i am also considering the same option.will decide in few days.
thanks for ur comment

 

[shafic]

Nice job:clapping: congrats!!

 

[lifewater]

Hey Great job man. Simply love it. Very fine hand I must say.

Best wishes,
Lifewater

 

[gcr]

congrats. nice job. If photos of original cabinet there, please post.
Waiting for the finished fruit.

 

[Audio_Freek]

Great Job, Looking for them after finish.

So how they sound in new Box ? Any difference \Improvement?

 

[mpw]

excellent work !

do tell us about the sound.

 

[krell]

thanks for supporting comments. yes the job makes me to get the back pain. but all vanished in to thin air once starts listening the new boxes.
the new boxes had smaller internal volume than the original ones.
the smaller box volume is giving the tighter bass than the previous large box.
the boominess was completely gone and some tightness appearing in the bass region.
before i am not able to increase the volume because of the slight hint of boom in the bass region.
now all had gone.
really enjoying the new sound.

 

[keith_correa]

Nice job on the bracing. With the wide width and depth of these boxes bracing is essential and I'm sure the box is now rigid. Some questions:

Did you stuff the mid chamber?

Is that port made of cardboard?

Did you stuff below the port?

Do I notice cracks on the back of the woofer cone in the picture of the woofer or are those crinkles?

Any reason why you didn't replace the NPE caps on the x-over with MPP ones?

How did you get the octagonal cutout done to flush mount the mid? CNC?

The originals had the mid and tweeter offset from the centre of the width, right? Any reason why you didn't maintain that offset?

Did you also change the positions of the drivers from the top edge from the original? If yes, any reason why?

Did you reduce the width from the original by around 2"?

Was the mid driver flush mounted in the original cabinet?

 

[sarith]

Excellent job dude!:clapping: waiting to see final finish..and hopefully a video of them singing too?:licklips:

 

[krell]

Nice job on the bracing. With the wide width and depth of these boxes bracing is essential and I'm sure the box is now rigid. Some questions:

Did you stuff the mid chamber?

yes, i stuff the mid chamber with glass wool same quantity removed from original speaker mid chamber

Is that port made of cardboard?

its the original port from jbl l100t cabinet. jbl made the port with cardboard and end finished with plastic ring.

Did you stuff below the port?

yes, the port is touching the braces.so all thress sides covered with the wool.
below the port there is one open brace chamber and it is filled with glass wool.

Do I notice cracks on the back of the woofer cone in the picture of the woofer or are those crinkles?

great to your sharp eyes.but it is the paper just peel.but not having any effect of the sound. the build quality of jbl drivers with aquaplas coating is second to none.so no worries.

Any reason why you didn't replace the NPE caps on the x-over with MPP ones?

crossover is already upgraded from 100T to 100T3 as suggested by lot of jbl fans.
crossover refininement may be a future project

How did you get the octagonal cutout done to flush mount the mid? CNC?

no cnc cut, it is done by router with flat bit.the carpenter done the job by charging amout for all flush mount

The originals had the mid and tweeter offset from the centre of the width, right? Any reason why you didn't maintain that offset?

the offset is preferable for large rooms,but i prefer the centre alignment for better imaging nor wall of sound.

Did you also change the positions of the drivers from the top edge from the original? If yes, any reason why?

yes, i changed the distance to keep the tweeter to my earlevel and raised the woofer to reduce the floor reflections from bass.

Did you reduce the width from the original by around 2"?

yes, reduced about 2.1"

Was the mid driver flush mounted in the original cabinet?

in the original cabinet the mid is not flush mounted.actually the jbl made a lot of cost cutting in the 100T except the top of the line best drivers and crossover.
i just try to overcome the corners and to get the best from the drivers.:yahoo:

 

[pksnathan]

A neat and an excellent work.Please send images of completed work after painting job is over.

Regards,
pksnathan

 

[keith_correa]

My 2 cents:

For the port - take stationery grade fevicol. Dilute it with water till it becomes runny. With a brush, coat the outside and inside of the cardboard tube with the diluted fevicol so that some gets absorbed by the cardboard. Leave it to dry - it dries relatively quick. Apply at least 2 coats. This will make the port more rigid. Some say this makes a difference. It certainly won't harm.

Great job by your carpenter to get the octagonal cutout done by a router. If he did not use a template, hats off to him

The mid and tweeter offset from the edges reduces diffraction. It's got nothing [well, almost...] to do with size of the room or wall of sound or imaging.

The z-offset or acoustic center of the drivers is dependent on the mounting [flush/surface] of the drivers and this is taken into account by the x-over. So if you have not surface mounted the mid as was done originally the acoustic center of the mid relative to the AC's of the other driver's has now changed. But not surface mounting this has a benefit because the diffraction of the tweeter is now reduced. So: one +ve and one -ve

Enjoy the new re-build!

 

[krell]

thanks for your suggestion. actually the port is snug fit with the hole.there is no wiggle. but i will apply favicol or white silicone on inside of the edges to make it complete air tight.
regarding flush mounting the carpenter done without any guide.we draw the line and he carefully moved the router bit around the edges.
for woofer he made some guide and followed it.
i am not technically that much knowledgeble, but the new box sound is better than the oreginal one,especially the bass region.:yahoo:

 

[keith_correa]

thanks for your suggestion. actually the port is snug fit with the hole.there is no wiggle. but i will apply favicol or white silicone on inside of the edges to make it complete air tight.

You misunderstood. I suggested applying/coating diluted fevicol to the surfaces of the port tube - both inside and outside surfaces to make the cardboard more rigid.

 

[krell]

ooh,now i understand.i will definitely do it.thanks

 

[hydrovac]

hi friends my jbl l100T cabinets...
and the crossover is from 100t3.

Nice work on the enclosures!

Interesting...
your signature also shows T3, but you are rebuilding T cabinets with T3 Xovers... do you have both the models, and trying to modify/upgrade 100T?
From what I read basic difference is cabinet construction and crossover points... all the drivers being same. Veneer finish is desirable to retain that vintage look.
Anyways, making them sound better seems to be the objective here...

The originals had the mid and tweeter offset from the centre of the width, right? Any reason why you didn't maintain that offset?

Did you also change the positions of the drivers from the top edge from the original? If yes, any reason why?

Did you reduce the width from the original by around 2"?

Was the mid driver flush mounted in the original cabinet?

Do you anticipate any negative effect from modding the baffle size and driver alignment/positioning? after all the crossover must have been designed taking baffle also into consideration.
Apart from this did you notice both the original speakers are symmetrical!
I am no big fan of symmetrical speakers personally... Krell must be trying to overcome this by redesigning them as symmetrically asymmetric enclosures..