Best Way to Add Fiberglass to an Existing Cabinet

[toddalin]

One thought on helping woofer acoustics integration is through the use of more fiberglass insulation in the cabinet. To wit, I bought a roll of R-30 the other day (heaviest they had and 9-1/2" thick). This 'glass has a heavy paper backing. I would like to apply it over the existing insulation in the L200 cabinet. I also got a can of spray adhesive.

Any ideas on what the best (and easiest) way to add this would be? Shall I spray the paper side of the new insulation and old 'glass in the cabinet and just lay the new insulation in, or remove the paper backing somehow, or...? :dont-know

Thanks guys.

[speakerdave]

I'm trying to remember when it was that JBL did itself use or recommended in any of its enclosure construction guides the use of that much fiberglas. I can't come up with any examples.

David

[Ian Mackenzie]

I really don't think that is it.

Too much fluff and you will mess with the net Volume and the tuning unless the dimensions are scale to compensate. One inch of fibreglass will increase the net volume by 10-15 percent. Mind you the 4430 was jammed with fluff from some pics I have seen.

[Don C]

The B212 was completely stuffed with fiberglass. JBL didn't use any paper backed glass though, and I don't think I would either. Separating the paper sounds like an unpleasant job, but that's probably what you need to do.

[Motus]

:DThe fiberglass I used to buy in Europe was always on paper base. I stripped the fiberglass from the paper since the paper might be set in motion -undesirable noises- if the glue is not properly applied or dries after a while. With a trowel you can separate the fiberglass, scrapping it from the paper and not worry about pieces falling off since the fiberglass is quite dense and holds well even without the paper base.
Good luck.

[toddalin]

I really don't think that is it.

Too much fluff and you will mess with the net Volume and the tuning unless the dimensions are scale to compensate. One inch of fibreglass will increase the net volume by 10-15 percent. Mind you the 4430 was jammed with fluff from some pics I have seen.


Even your 4545s show a slight depression at ~600 Hz coupled with a peak just beyond that, though not to the extent that I've been dealing with.

http://jbl43.net/catalogs/4345/4345-frq.jpg

[Robh3606]

Even your 4545s show a slight depression at ~600 Hz coupled with a peak just beyond that, though not to the extent that I've been dealing with.

Hello Toddalin

What does that have to do with your problem with your drivers. You have several people trying to help you but you have split this into 4 threads.

What exactly have you done based on some of the suggestions others have given you??

What's up with the Zobel??

It was obvious from the simulation that what you were using was rolling off the high end on the 2235.

http://www.audioheritage.org/vbulletin/showthread.php?t=18943

Have you tried different positions in the room??

Probably not an issue if the 130A's didn't have the same problem. Did you have this issue with the 130's??

What else changed besides the woofer swap???

Did you try a different speaker in the same location??

Probably won't help if the issue was not there with the 130A's.

You should be able to get a workable system from the components you have.

Rob:)

[toddalin]

Hello Toddalin

What does that have to do with your problem with your drivers. You have several people trying to help you but you have split this into 4 threads.

What exactly have you done based on some of the suggestions others have given you??

What's up with the Zobel??

It was obvious from the simulation that what you were using was rolling off the high end on the 2235.

http://www.audioheritage.org/vbulletin/showthread.php?t=18943

Have you tried different positions in the room??

Probably not an issue if the 130A's didn't have the same problem. Did you have this issue with the 130's??

What else changed besides the woofer swap???

Did you try a different speaker in the same location??

Probably won't help if the issue was not there with the 130A's.

You should be able to get a workable system from the components you have. Not sure how low you can push the 175's. Do they look OK close in??

Rob:)

From the beginning:

I used the 130As, LE175-HL-91, 075s on N1200 and N7000. I used this on the Yamaha DSP-A1 with lots of eq provided by Yamaha 31-band units tied between the pre-out/pwr in. The noise of the eqs always bothered me, and I even put 10,000 ohms in-line to reduce this noise.

This served well for years until we went with high def and I needed to switch component. At that time (almost 5 years ago now) we purchased the Yamaha RX-Z9 that self-eqs with its internal 31-band units, in the digital domain. This meant I could get rid of the outboard eqs and their noise.

But, without the outboard eqs, there was no way to get the bass out of the 130As. So these were replaced with 2205s recharged and reconed as 2235s two years ago.

At that point, I noted a severe lack in the vocal range (especially male) around 600-700 Hz that irritates the heck out of me (even with the Yamaha self-eq). Maybe the lack was there with the 130As, but the eqs took care of it, or maybe it wasn’t there with the 130As.

Anyway, the 2235 was never intended to be used with a 1,200 Hz crossover, so the “Keeper Crossovers” based on the L200B’s N200B with an onboard N7000 were constructed with a crossover point of about 800 Hz ala the L200B. I used very high quality components and Theta by-pass caps. Should have been an ideal match and it is even noted in the JBL literature that the 2235 is the correct woofer replacement for an L200B!

But the hole persisted.

So…, is it the horn not getting down enough, the woofer not getting up enough, some room anomoly, some cabinet anomaly, or even just a 2205 trying to “pretend” it’s a 2235?

So, all attempts have been focused on filling this “void” between the woofer and horn. That’s the inter-relation between the threads that you are missing here.

The woofers were addressed. Two weeks ago they were again recharged and WT-2 testing confirms that for all intents and purposes the 2205 is identical to a new 2235.

The Zobal was changed from the literature value of 33 mF to 15 mF based on modeling provided by Grumpy, and this in fact does pay dividends in the troublesome area. I can piggy back a secondary cap on the 15 mF to get it back up to 33 mF and watch the Behringer sink in the troublesome range making the hole deeper. Remove the cap and the Behringer rises. It’s not flat, but definitely a step in the right direction.

The fiberglass in the cabinet is an attempt to reduce a potential standing wave in the cabinet that could possibly causing a cone cancellation at the troublesome frequency as noted by one/some LHF members. I’ll also try to add a brace between the front and back of the cabinets if I can (already bought the wood). It was noted that the walls may be absorbing some of the energy in this frequency band.

Probably none of these further modifications will reap sonic benefits and I’ll just end up making more work for myself (and putting a screwdriver through a cone), but just maybe…

[scott fitlin]

Wouldnt using your speakers with their correct woofers, that have the neccesary response, and adding a subwoofer been a better solution?

In my experience, drivers that dont have the repsonse your wanting will not really be corrected by EQ. EQ will not make the 2235,s have the midrange respsonse, and the 130,s do, and sub would give you the bottom you want.

You can push the EQ all you want, youll still have that hole around 600-700hz, giving you that nasal tonality.

[toddalin]

Wouldnt using your speakers with their correct woofers, that have the neccesary response, and adding a subwoofer been a better solution?

In my experience, drivers that dont have the repsonse your wanting will not really be corrected by EQ. EQ will not make the 2235,s have the midrange respsonse, and the 130,s do, and sub would give you the bottom you want.

You can push the EQ all you want, youll still have that hole around 600-700hz, giving you that nasal tonality.

As noted, using the 2235 is now the correct woofer replacement for the L200B.

Yes I use subs, but that's not the same and certainly no substitute for full range speakers..., at least to my ears.

The drop-out at 600-700 Hz gives just the opposite of the nasal effect. The voices are too "laid back" which makes them hard to understand. This is especially noticable with movies making dialog less intelligible.

[scott fitlin]

I always thought the L200,s had a different woofer?

[4313B]

The Zobal was changed from the literature value of 33 mF to 15 mF based on modeling provided by Grumpy, and this in fact does pay dividends in the troublesome area. I can piggy back a secondary cap on the 15 mF to get it back up to 33 mF and watch the Behringer sink in the troublesome range making the hole deeper. Remove the cap and the Behringer rises. It’s not flat, but definitely a step in the right direction.If you are running a 15 uF / 10 ohm conjugate on the 2235H you might want to just pull it out completely.

[hjames]

I always thought the L200,s had a different woofer?

They do - but its currently out of production, so I gather the logic is that the 2235 is the recommended replacement, tho its performance is difference than the 2215 was.

[scott fitlin]

They do - but its currently out of production, so I gather the logic is that the 2235 is the recommended replacement, tho its performance is difference than the 2215 was.Which is WHY it doesnt sound right, it isnt the woofer the speaker was designed for.

I have always been of the opinion that a speaker with a slightly hotter response in certain regions are easier to tame the peaks with EQ,s and make it work, than it is to use EQ to restore dips in freq response, which to me, doesnt really work well at all.

[pos]

The original L200 had a le15B (2216A) and was tuned to 37hz:
http://www.lansingheritage.org/html/jbl/specs/home-speakers/1973-l200.htm
blocking one port as toddalin results in a tuning around 27hz.

The L200B had a 136A (2231A) and was tuned lower (only one, shorter, port, maybe 30hz?), in the same cabinet:
http://www.lansingheritage.org/html/jbl/specs/home-speakers/1975-l200b.htm

[LRBacon]

One thought on helping woofer acoustics integration is through the use of more fiberglass insulation in the cabinet. To wit, I bought a roll of R-30 the other day (heaviest they had and 9-1/2" thick). This 'glass has a heavy paper backing. I would like to apply it over the existing insulation in the L200 cabinet. I also got a can of spray adhesive.

Any ideas on what the best (and easiest) way to add this would be? Shall I spray the paper side of the new insulation and old 'glass in the cabinet and just lay the new insulation in, or remove the paper backing somehow, or...? :dont-know

Thanks guys.

I would have bought the unfaced batts. No paper backing.

Larry

[toddalin]

If you are running a 15 uF / 10 ohm conjugate on the 2235H you might want to just pull it out completely.

Been there tried that..., bad idea. This makes the frequency responce of the woofer more linear, but takes the "boost" out where needed. Also, this lets the woofer play too high into the horn range creating peaks (and cancelations) there.

[toddalin]

I would have bought the unfaced batts. No paper backing.

Larry

Actually, when I unrolled the 'glass, the paper was around the entire mess, but the 'glass was not backed with it. Untimately, I cut a 1 cubic foot section (14"x15"x9") and placed it behind the woofer.

This doesn't seem to have helped matters. :(

[edgewound]

Been there tried that..., bad idea. This makes the frequency responce of the woofer more linear, but takes the "boost" out where needed. Also, this lets the woofer play too high into the horn range creating peaks (and cancelations) there.

If the problem lies with a "hole" in the 600-700Hz range...and taking that conjugate out of the network makes the woofer more linear and reaches up to the horn range...

It would seem to be obvious that the solution lies within the crossover at that range and needs to be reworked....it's just a filter that needs to be tailored to your components.

Todd...at some point you're going to have accept the fact that the "keepers" need to be modified. Just about every possible solution has been gone over and still isn't to your liking.

[Ian Mackenzie]

Kenneth,

Please see the other thread.;)

http://www.audioheritage.org/vbulletin/showthread.php?t=18975&goto=newpost (http://www.audioheritage.org/vbulletin/showthread.php?t=18975&goto=newpost)

Ian

[4313B]

Been there tried that..., bad idea. This makes the frequency responce of the woofer more linear, but takes the "boost" out where needed. Also, this lets the woofer play too high into the horn range creating peaks (and cancelations) there.It isn't a "bad idea". It's perfectly normal to tweak a conjugate or even to leave one out if necessary, or use just a parallel resistor. Or a conjugate and a parallel resistor. And yes, it can be used to tailor the roll-off of the transducer.

[toddalin]

It isn't a "bad idea". It's perfectly normal to tweak a conjugate or even to leave one out if necessary, or use just a parallel resistor. Or a conjugate and a parallel resistor. And yes, it can be used to tailor the roll-off of the transducer.

You missed the point.

In general it may not be a bad idea, but in this case leaving the Zobal off entirely is a bad idea for the reasons I noted. Been there tried that and it only made things worse.