JBL E140 modification question

[spkrman57]

This is a simple one, but I wanted to be sure before implementing.

I have a pair of JBL E140-8A's that I don't need the aluminum dust cap in the application I have in mind. I want to use in a front loaded horn system from 150hz up to 800hz.

I want to know if I could put a paper dustcap over the aluminum one, or if I need to remove the aluminum to install the paper dust cap.

I am looking at using the 140's due to their extremely low Qes which I believe makes them a good candidate for horn use.

I will be using less than 10 watts in their intended mode. The only thing that might screw things up is the "bump" in response due to design that I read about. Other than that, I figure the dust cap needs to be subdued(aluminum).

Any and all comments welcome on this. The horn is a older Edgar tractix 150hz front loaded which I will use up to 800hz where a GP 399 driver on Edgar 500hz round horn will be used.

Ron

[rek50]

How about a "Snazzy" pair of old-time "Pasties" to tone down the aluminum dust caps. I wouldn't use ones with tassels, but then again.......J/K Ron. I've wondered about adding some self-stick felt like material that I got at JoAnn fabric, for a similiar task.... "Red Green" soft-dome conversion kit.

[Earl K]

Hmmmm Ron,

- I'm not sure what you are hoping to accomplish by leaving the Al dust-cap in place.

- If it is to maintain resale value by being able to return the driver to stock / then I think you are barking up the wrong tree .

- Any effective treatment to that dome will require ; removal ( my favourite ), paint ( ???? ) , "pasties" of all forms , or your idea of paper clad aluminum. For all these ideas to be effective, the new addition must firmly adhere to that aluminum dome ( or "Hello" buzzing ). So, gluing anything on will make it impossible to not inflict damage upon attempted removal .

- I guess that if you want a minimally intrusive mod., I'd start with the virgin speaker, then paint/goop the dome and then go from there. The worst case scenario is that after all your experimenting you'll have to buy an eBay kit of Al domes to restore it to stock.

:)

[spkrman57]

I think if I don't hear otherwise that I will get paper dustcaps from a friend of mine that should be the same size and just have it glued on the aluminum dustcap already in place.

Or maybe just try it in the horn and see if it annoys me or not!

Ron

[spkrman57]

Earl,

Thanks for reply. I just don't know if the aluminum dustcap will spray HF I don't need into the horn. If I could just use it the way it is, then I will leave it alone.

I see the E140 as a great horn driver from the low "Q" specs, basically the reason I picked them up for.

Ron

[spkrman57]

My concern with applied coating to the dustcap is I don't want to "mass-load" the driver and change the specs as I would imagine it would increase Qts by adding weight to the cone/dustcap.

Ron

[johnaec]

I just don't know if the aluminum dustcap will spray HF I don't need into the horn.Wouldn't you be using a crossover anyway? If the E140 isn't getting any high frequencies to begin with, it won't have any to spray around...

John

[edgewound]

The aluminum dome can still have a metallic overtone to it. The best way to deal with that is to remove the aluminum dome and replace it with a paper dome

[spkrman57]

I have heard from those using Bruce Edgar's midbass horns with D130's and complaining about hearing the HF spray(even with using a crossover which is 1st order). So I will go to my speaker repairman and see if he has the time to perform the operation.

I have 2 left thumbs and won't take a chance at screwing up a pair of good drivers!

Ron

[toddalin]

Could you make a conical mask with 4" hole to lay over the speaker and lightly spray the domes with a textured paint or rubberized coating?

[spkrman57]

If it did not add too much mass to the cone, I would think rubber cement would be a good thing to apply to the dustcap. But I think that would add more mass than would be a good thing.

So far the best solution seems to be removing the aluminum dustcap and replacing with a paper dustcap.

Thanks to all for the replies!

Ron

[Zilch]

Dust the dome with Aquaplas.... :D

[scott fitlin]

Dust the dome with Aquaplas.... :DYou could do this, if you know the right material to use, and how much of it to use!

From experience, if you spray paint the dustcap, it will tone it down a bit. Not as much as paper, but it will calm it down! Matte black spray paint. We used to do this years ago when guys didnt want to see the shiny aluminum! It seemed to also dull down the response too!

[Mr. Widget]

Dust the dome with Aquaplas.... :D

I wonder if TiDome has thought of that?:rotfl:


I have used K140s with paper domes and liked them a lot. I'd replace the dome.


Widget

[scott fitlin]

I wonder if TiDome has thought of that?:rotfl:


I have used K140s with paper domes and liked them a lot. I'd replace the dome.


WidgetDitto, the 140,s have a punchiness, best described as JBL sound!

My personal opinion is that if you love that kind of punchy bass, use the K or E 140,s with paper domes, and its a hard woofer to beat! In any application!

[spkrman57]

I have not had time to even listen to these drivers yet. My main system is sounding good(not easy in a small room) and GF seems to think I don't spend enough time with her.

I will have to do something this weekend with the E-140's. At the risk of trying something unacceptable, I might try them in a pair of Peavey FH-1 folded horns.

They are considered pa type enclosures, I think of them as poor mans La Scala's(Klipsch). They are efficient, but I have never put a good driver in them yet.

They are currently loaded with Altec 418's which will outrun a 806/811B horn combo with just a cap in series and a small coil on the bottom end.

Seriously loud, but not necessarily great sounding. The Fh-1 is loosely rated at 60hz to 400hz (a stretch at that).

ROn

[Earl K]

Heh Ron,

- Sorry to leave you hanging. ( work and all that )

- I vote like the rest to move straight to a paper dustcap.
( ie ; I don't have a clue what you can use as a Aquaplas substitute that won't mass load those horn drivers . )

- OTOH ; Try a glue like you've just suggested .

- You guys with WT2 should be able to test for small parameter changes & then tell the rest of us peasants what actaully works . ( and why ) .

- FH-1 ??? ughhh, who dumped those on you ?? Magnetar ? ;)

:p

[spkrman57]

Earl,

They came cheap some years ago. I do have the woofer tester and will probably test the raw drivers 1st and then maybe rubber cement the "chrome" domes to see the T/S changes.

Maybe it won't be enough to change that much.

The horns I want to use these in are 150hz Edgar midbass tractix horns I picked up recently. I think they are made for 10" drivers due to the 4.5" X 4.5" throat. Bruce said a 15" would most likely not be optimum for these horns, but try it and see what happens.

Maybe I should try them without doing anything to the aluminum dustcaps and see how well they work before trying to do any modding.

I used to own Bruce's 80hz midbass horns, but my room is too small and wanted a shorter throw horn to try.

Side not to Earl: We previously discussed 1st order crossover on horns with single oil cap and conjugate resistors and L-pad. On my current system I am using 2 ufd oil paralleled with 12 ufd MPT and .68 ufd MPP cap into L-pad. I think I see what you were telling me about the "overdamped" Altec drivers compared to the "underdamped" JBL's. The use of different caps to obtain the end result capacitance seemed to make a little difference, but I wish I had some JBL drivers (2") that could be had without 2nd mortage to see the differences.

Keep the good info flowing, I really do appreciate it. There are not many hardcore horn fans here compared to direct radiator followers!!!!

Thanks, Ron

[Earl K]

Side note to Earl: We previously discussed 1st order crossover on horns with single oil cap and conjugate resistors and L-pad. On my current system I am using 2 ufd oil paralleled with 12 ufd MPT and .68 ufd MPP cap into L-pad. I think I see what you were telling me about the "overdamped" Altec drivers compared to the "underdamped" JBL's. The use of different caps to obtain the end result capacitance seemed to make a little difference, but I wish I had some JBL drivers (2") that could be had without 2nd mortage to see the differences.

- FWIW : MPT ??? ( I don't know that acronym) , MKT = a metallized mylar capacitor / which will sound somewhat "veiled" in comparison to any MKP ( metallized polypropylene ). If that MPT cap is a mylar, then I would recommend trying some of the inexpensive Dayton MKP types from Parts Express .

- I've been experimenting for about 2 1/2 years with caps and I just can't hear any advantage to DC Biasing a motor-run oil cap. In fact , quite the opposite.
- OTOH, all the dry film cap types I've tried ,( especially MKP types ) really become a different beast when Charge Coupled ™. Biasing caps, seems tp tame resonances ( you didn't know exist ) that really plague this form of cap.
- Also, ( I'm still in the midst of these experiments ) some Film & Foil Bypass caps are best left unbiased if the values are small enough ( seemingly less than .1uf or .2uf ) .

- If you don't have it , here's the price list ( pdf ) for Dayton Metallized Polypropylene Caps. (http://www.partsexpress.com/pdf/catalog05/140pec05.pdf)
- The web page is here (http://www.partsexpress.com/webpage.cfm?&DID=7&WebPage_ID=114#capacitors) for the Dayton caps from PartsExpress .

- Considering just how cheap these Dayton caps are, I would buy the necessary values and Charge Couple ™ just them.


- So in your case ( with Altec 288s ) I'd use the "Oilers" as is ( straightup / non biased , with DC biased MKP types ( paralleled to the oilers ) plus a bypass cap either way ( again paralleled to the first two ).



:)

ps ( are your GPA 399 the same as a 288-8K / with the normal size body ? )

[spkrman57]

But due to legal reasons these can't be called 288K's. It is nice that there is a way to get "NEW" drivers and the cost is a fraction of the JBL driver cost for the same application. If not for that I would still be playing with unknown drivers from whatever source came my way.

I would like to try a JBL 2" driver and it seems the 2441 is the best one for my application, but I have not been able to find them for a decent price, and still have to send them out to be checked anyways. So hence my reason for using the Great Plains products. I don't have to be concerned with how well they work since these are basically same as new!

MPT = unknown to me. They are Dayton Audio from Parts express.

Ron

[Earl K]

Hi Ron


I do have the woofer tester and will probably test the raw drivers 1st and then maybe rubber cement the "chrome" domes to see the T/S changes.

-That makes sense to me. I look forward to your report . ;)


MPT = unknown to me (Earl). They are Dayton Audio from Parts express.

Oh,,, so does that make them a metalizzed polypropylene ? ( I was over at the PartsExpress site and couldn't find that acronym ).


:)