Hello,
I'm installing new X-overs (JBL L100 Century) for the 4310 and will be adding bracing and redoing damping in the process.
Question: After opening the speaker and removing the drivers, I found fiberglass behind the mid-driver. Is this normal, what JBL did? Or did someone add it along the way?
If it's a good thing.. do I just leave it there?
For the damping, I'm planning 2mm bitum + 4cm corregated foam..
I have enough foam to replace the fiberglass behind the mid-driver if that's better.
As you can tell this is my first upgrade to speakers. My experience is building a couple guitar amps, and rebuilding a tube hifi amp.
Thanks for the advice, Paul
I'm installing new X-overs (JBL L100 Century) for the 4310 and will be adding bracing and redoing damping in the process.
Question: After opening the speaker and removing the drivers, I found fiberglass behind the mid-driver. Is this normal, what JBL did? Or did someone add it along the way?
If it's a good thing.. do I just leave it there?
For the damping, I'm planning 2mm bitum + 4cm corregated foam..
I have enough foam to replace the fiberglass behind the mid-driver if that's better.
As you can tell this is my first upgrade to speakers. My experience is building a couple guitar amps, and rebuilding a tube hifi amp.
Thanks for the advice, Paul
Attachments
fiberglass is pretty good at damping, but it is better for bass. I would leave the fiberglass since there is not a lot of it and fill the cavity with loosely with long hair wool (madisound) which is going to have the greater effect on the upper frequencies ...foam would change the volume of the chamber and has no real sound absorbtion properties except at extreme high frequency.
Corrogated Foam is used more as a diffuser externally (for the most part foam is marketing hype in regards to absorbing sound)- we line our walls with fiberglass in our recording studio, cover by open weave burlap)...it is never used in speakers. . .You want to dampen the chamber so that the soundwaves do not reflect back into the cone . . .If you are happy with the midrange- don't fix what is not broke. JBL are very good designers. A lot of thought went into that speaker system...check out Lansing Heritage.
I am not saying it sounds good ( I never heard one ).
You should not be using a crossover from a different speaker system, and that is what it is a system. The crossover is interacting with the impedance curves and frequency response of the drivers and the effect the cabinet is having on the impedance curves.
All drivers are very different (some manufactors get similar curves in tweeters as they share voice coils in their lines) . . .You could swap out parts of identical value in the cross over ie: upgrade the caps, mix caps to achieve values/quality and price point (bypassing) and replace iron core inductors with air cores . . .
Corrogated Foam is used more as a diffuser externally (for the most part foam is marketing hype in regards to absorbing sound)- we line our walls with fiberglass in our recording studio, cover by open weave burlap)...it is never used in speakers. . .You want to dampen the chamber so that the soundwaves do not reflect back into the cone . . .If you are happy with the midrange- don't fix what is not broke. JBL are very good designers. A lot of thought went into that speaker system...check out Lansing Heritage.
I am not saying it sounds good ( I never heard one ).
You should not be using a crossover from a different speaker system, and that is what it is a system. The crossover is interacting with the impedance curves and frequency response of the drivers and the effect the cabinet is having on the impedance curves.
All drivers are very different (some manufactors get similar curves in tweeters as they share voice coils in their lines) . . .You could swap out parts of identical value in the cross over ie: upgrade the caps, mix caps to achieve values/quality and price point (bypassing) and replace iron core inductors with air cores . . .
Thanks for the comments. I'll leave the fiberglass as is, and btw, the cylinder enclosure is closed on the bottom.
Erickalan77, The new X-over kit (I got) is specifically designed for the 4310. (It's just on the L100 page.)
After using the speaker a few years, I agree with what's written on this site, JBL L100 Century.
Of course being my first mod, I'm plenty nervous about the results, but going back to original X-over would be pretty easy.
Reversing out foam for fiberglass as well.
Understand the bracing comment, however Troels recommends it - and I would like less boomy bass. That change could be reversible but with considerable more trouble.. Hoping for the best.. as am half way done with it now..
Erickalan77, The new X-over kit (I got) is specifically designed for the 4310. (It's just on the L100 page.)
After using the speaker a few years, I agree with what's written on this site, JBL L100 Century.
Of course being my first mod, I'm plenty nervous about the results, but going back to original X-over would be pretty easy.
Reversing out foam for fiberglass as well.
Understand the bracing comment, however Troels recommends it - and I would like less boomy bass. That change could be reversible but with considerable more trouble.. Hoping for the best.. as am half way done with it now..
Hi erickalan77,
I think I need your help with something you said.
If the damping material is less effective as the frequency decreases then I am trying to wrap my head around your statement that fiberglass is better at bass while the long hair wool is better at the highs. To me if it is better at damping the highs then it will be better at damping the lows also. I agree with you that the long hair wool is a very good product but I can't see why the fiberglass is good or better on the low end. To me it's not, it's just cheaper. Correct me if I misread your post.
Is there something I could read on this rather than have you go through it with me? I have done many experiments with cabinet materials, panel bracing, panel damping, and internal damping so I'm not inexperienced but you've got me intrigued and I appreciate any input you have.
I think I need your help with something you said.
If the damping material is less effective as the frequency decreases then I am trying to wrap my head around your statement that fiberglass is better at bass while the long hair wool is better at the highs. To me if it is better at damping the highs then it will be better at damping the lows also. I agree with you that the long hair wool is a very good product but I can't see why the fiberglass is good or better on the low end. To me it's not, it's just cheaper. Correct me if I misread your post.
Is there something I could read on this rather than have you go through it with me? I have done many experiments with cabinet materials, panel bracing, panel damping, and internal damping so I'm not inexperienced but you've got me intrigued and I appreciate any input you have.
Hello...Fiberglass is very dense and uniform. It can be used in sheet form. I have been using 1 1/2 myself this week the first few 6 inches from the baffle along the perpendicular walls to reduce reflections back into the cone. but for fill I use wool as I cannot get the density and uniformity of glass. It would not be practical to line a wall with wool as you can not get it in that fashion. Wool is ultimately better than glass in a stuffing scenario. Wool is better for some reasons pertaining to transfering the "soundwaves to heat"....The sound waves lose their energy exciting the wool and glass... Wool has more mass than glass and is softer so it is better...I have raw wool (unprocessed except that it was washed) pretty dense in that form.
I did a test after that first post this morning while was re-stuffing my monitors to experiment with taming midrange irregularities... I put a matted clump off wool to my ears, and 1 1/2 glass (fret not about glass dust and particles I lightly sprayed the sheet pieces with 3M supper 77 - rubber cement to lock the fibers to the sheet and increased mass/damping). . . wool was more effective at higher frequencies especially midrange....
@ Paul...some bracing will reduce boom (reverberation as the panels release their energy) One per panel would have significant effect. It would effectively double the mass by locking the two panels together..3/4 becomes 1 1/2 panels and reduces cabinet panel expansion and contraction...it is so effective I would suggest restrained use so as to not significantly change the volume.
A couple weeks ago I was bored and trying to tweek some 5" Sony's into decent shape for bedroom duty. I put a single 5/8 hardwood dowel from the baffle to the rear panel (the other panels were small and solid). Lined the cabinet with 1 1/2" glass. WoW...the awful boomy midbass, deep bass reverberation and midrange leakage through the port were significantly reduced or gone from perception...Ultimately the speakers are sitting in the closet cause I never could get the midrange resolution out of them that I am use to with the cabinet mods, a new tweeter and good poly caps . . . no great loss, I was just playing around.
I would suggest a little glass ($4 - sold at home depot to wrap HVAC and stuff voids) and 3/4 dowels polyureathane glued...The stuff will expand to fill voids . . I like dowels as they are hardwood and wont pose a surface to create a reflection but what ever floats your boat or wood working skills.
back panel, one side, one top bottom...If it gets over damped for your taste you can take it out . . .have a nice day . . .~erick~
I did a test after that first post this morning while was re-stuffing my monitors to experiment with taming midrange irregularities... I put a matted clump off wool to my ears, and 1 1/2 glass (fret not about glass dust and particles I lightly sprayed the sheet pieces with 3M supper 77 - rubber cement to lock the fibers to the sheet and increased mass/damping). . . wool was more effective at higher frequencies especially midrange....
@ Paul...some bracing will reduce boom (reverberation as the panels release their energy) One per panel would have significant effect. It would effectively double the mass by locking the two panels together..3/4 becomes 1 1/2 panels and reduces cabinet panel expansion and contraction...it is so effective I would suggest restrained use so as to not significantly change the volume.
A couple weeks ago I was bored and trying to tweek some 5" Sony's into decent shape for bedroom duty. I put a single 5/8 hardwood dowel from the baffle to the rear panel (the other panels were small and solid). Lined the cabinet with 1 1/2" glass. WoW...the awful boomy midbass, deep bass reverberation and midrange leakage through the port were significantly reduced or gone from perception...Ultimately the speakers are sitting in the closet cause I never could get the midrange resolution out of them that I am use to with the cabinet mods, a new tweeter and good poly caps . . . no great loss, I was just playing around.
I would suggest a little glass ($4 - sold at home depot to wrap HVAC and stuff voids) and 3/4 dowels polyureathane glued...The stuff will expand to fill voids . . I like dowels as they are hardwood and wont pose a surface to create a reflection but what ever floats your boat or wood working skills.
back panel, one side, one top bottom...If it gets over damped for your taste you can take it out . . .have a nice day . . .~erick~
Wool is better (if you were stuffing) ...but for restrained, consistent use- such as lining a wall; glass is better. . . I took apart a Cerwin Vega 12" 3 way once . . .they had made a chamber out of 1" wool (or cotton or nylon???) like carpet matting or perhaps say; under-layment . . you might have scene the stuff under your car's carpet. So that the sound waves had to pass through it leaving (and returning to) the cone ... basically a little 1 cubic foot enclosure of damping material inside a 3-4 foot box and a rear port just to be sure of limited coloration of the primary signal . . . an interesting speaker. Don't try this at home folks, that was a factory tweek for that system....just bending your ear . . .~erick~
Ok.. now I'm getting worried..
I spent my Sunday adding braces to one speaker. (In Paris, there is a time difference.)
Here's in my own words, what Troels kit states - adding bracing to rear panel and sides could help sound.. (that's an approximation).
So I did not add braces to what one calls in a guitar amp, the baffle.
The back has ~1"x1" glued and screwed into the corners.
Same was done for the sides, coming towards the baffle but stop about 1/2" before the baffle. Just a few screws were used since access is difficult.. Quite a job!
Am I correct in figuring that foam will increase volume, therefore equalizing the space taken with the braces, or even leaving more volume?
In any case the braces along with caulking are complete for one speaker.
Next will add 2mm bitum (adhesive), and 4cm foam.
I have wool but not a lot. Will cover the new X-over panel with wool, which lies directly behind the bass driver.
Could probably put a little wool in the midrange driver enclosure.
For sure I will test this before proceeding with the 2nd speaker.
Please reassure me that I didn't ruin the thing by not bracing the baffle.
If I did wrong I will correct but recognize will be a big job..
I spent my Sunday adding braces to one speaker. (In Paris, there is a time difference.)
Here's in my own words, what Troels kit states - adding bracing to rear panel and sides could help sound.. (that's an approximation).
So I did not add braces to what one calls in a guitar amp, the baffle.
The back has ~1"x1" glued and screwed into the corners.
Same was done for the sides, coming towards the baffle but stop about 1/2" before the baffle. Just a few screws were used since access is difficult.. Quite a job!
Am I correct in figuring that foam will increase volume, therefore equalizing the space taken with the braces, or even leaving more volume?
In any case the braces along with caulking are complete for one speaker.
Next will add 2mm bitum (adhesive), and 4cm foam.
I have wool but not a lot. Will cover the new X-over panel with wool, which lies directly behind the bass driver.
Could probably put a little wool in the midrange driver enclosure.
For sure I will test this before proceeding with the 2nd speaker.
Please reassure me that I didn't ruin the thing by not bracing the baffle.
If I did wrong I will correct but recognize will be a big job..
I keep seeing quotes about certain materials being "better than fiberglass" without any facts to back it up.
The people that know about this are those in architectural acoustics that are constantly measuring the absorption vs. frequency of a variety of materials. Generally, soft absorption materials have some lower frequency where they become effective from and from that frequency up they have full absorption (an alpha of .9 or greater). Generally the only way a material has lesser performance at higher frequencies would be if they had a hardened surface, such as fiberglass with with a heavily laquered surface, or intentionally band-passed aborption materials such as fiberglass with a heavy membrane surface, sometimes used as a tuned bass absorber.
Fiberglass is generally the best material around in terms of effectiveness for a given thickness. People seem to think that, since it is cheap and available at Home Depot, it must not be the best material for sound absorption. I would disagree with that.
David S.
I generally have pretty good luck with fiberglass. I'm sure there are measurable differences, but meh. I've got a pile of fiberglass and a pile of acousta-stuff in the garage and more often that not I reach for fiberglass.
In the event that a madman with a measuring device holds me hostage and measures my speakers I might be in trouble, however to me it all kinda gets lost in the enjoyment of the music
I use rockwool now. $ for $ and " for " I believe it is the best. I wonder of Erick was really pointing out the virtues of use rather than sonic qualities.
Sheet lead with holes punched in it sandwiched between two layers of rockwook is effective when hung near the back of the cabinet. So are linoleum tiles for panel damping. There's all kinds of products you might not associate with it that are fine and inexpensive.
Sheet lead with holes punched in it sandwiched between two layers of rockwook is effective when hung near the back of the cabinet. So are linoleum tiles for panel damping. There's all kinds of products you might not associate with it that are fine and inexpensive.
Like this Cal?
http://www.amazon.com/Grodan-Starter-Plug-Rockwool-Media/dp/tags-on-product/B0002IU8MA
Or something different?
That looks like it would work but they are pricey as they're meant for starting plants. The rockwool I was referring to is mineral wool or stone wool often made from basalt. Similar to fiberglass in that in comes in batts and used for insulating things but it is heavier and denser and from my pov seems to be the winner.
Here's a site on it:
http://www.baztex.ru/en/
Here's a site on it:
http://www.baztex.ru/en/
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I was pointing out sonic attributes...fiberglass is only outdone for absorbtion of sound waves by long hair wool. . .to dampen the waves by converting the energy of the vibrating air.. . . edge/corner brcing is going to do nothing for a factor speaker that was assembled with clamps or hydrolic press/clamps (real cool machines- I use to use one in cabinet shop when I was young) open cell foam has no effect on bass or midrange or much of anything( it is nice to sit or sleep on though )...adding braces you do not need and bitum is going to change the volume (lower it) which is going to change tuning of a sealed or vented cabinet. . ..
braceing could be used from panel to panel to stiffen the middle of the panels effectly cutting their length in half and doubling the panel thickness at the point of fastening. . .
I am going to modify some B&W's with 3/4 dowel from the front baffle to rear as the panels are only 1/2" thick and from side to side; the tops are small enough that they pass the knuckle rap test .. instead of bracing or using 3/4 stock - B&W use 1/4" bitum throughout...that was part of the design though so the volume and WOOL (factory) stuffing works to tune the (sealed) cabinet to a Q of .7 ...A pair of dowels would have not volumetric effect that could be perceivable. . . . . .google attributes of stuff and panel damping materials material if you do not want to take my word for it....ounce for ounce... long hair wool ( unprocessed - just cleaned and combed) is the most effective followed by fiber glass . . .I am not talking sound proofing...but sound wave absorbtion ( reduced reflections ) Polyfil sucks and foam has no place anywhere except as a sound barrier when it is closed cell . . . . have a nice day . . .~e~
braceing could be used from panel to panel to stiffen the middle of the panels effectly cutting their length in half and doubling the panel thickness at the point of fastening. . .
I am going to modify some B&W's with 3/4 dowel from the front baffle to rear as the panels are only 1/2" thick and from side to side; the tops are small enough that they pass the knuckle rap test .. instead of bracing or using 3/4 stock - B&W use 1/4" bitum throughout...that was part of the design though so the volume and WOOL (factory) stuffing works to tune the (sealed) cabinet to a Q of .7 ...A pair of dowels would have not volumetric effect that could be perceivable. . . . . .google attributes of stuff and panel damping materials material if you do not want to take my word for it....ounce for ounce... long hair wool ( unprocessed - just cleaned and combed) is the most effective followed by fiber glass . . .I am not talking sound proofing...but sound wave absorbtion ( reduced reflections ) Polyfil sucks and foam has no place anywhere except as a sound barrier when it is closed cell . . . . have a nice day . . .~e~
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I did some googling of "long haired wool sound absorption" and didn't really find anything other than a lot of audiophile references to its use in TLs. In general if a material is good for sound absorption you'll find measurements on it. If not then you won't. If you have a reference with valid measurements I'd like to see it.
Ditto BAF wadding. It was designed for stuffing pillows and has poor acoustical properties. You won't find acoustical measurements on it because anyone that started taking measurements would find it worthless and not bother to list it. Speaker dablers like to use it because it looks like it should do something, is cheap, and is easy to use.
Lots of measurements out there for fiberglass and rockwool and some specialized foams.
By the way, B&Ws 1/2" panels with thick bitumin closely follow proven BBC design tenants. The thinner panels make the damping more effective (better ratio of damping to stiffness).
David S.
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