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Hofmannhp
01-07-2004, 07:41 AM
Hi Forum,

is anybody in this forum who can tell me if the diaphragma for the 2402 (bullet) and the 2405 (slot) are the same?
Whats with the gap space?

I place this question, cause Cannonsound tells that they only have the dia for 2405.

thanks for any reply

HP

4313B
01-07-2004, 08:16 AM
The 075/2402 uses the D8R075 diaphragm. Possible alternatives are the D16R076 and the D16R2405.

The 077/2405 uses the D16R2405 diaphragm. Possible alternatives are the D8R075* and the D16R076.

* Note that I personally have never seen where JBL has specifically stated that the D8R075 can be used in the 2405, only in the 077. I have no idea why.

Both the D8R075 and the D16R2405 are formed from 0.0022" aluminum alloy. Both have a 0.025" gap. Both have a DCR range of 5.7 ohms to 6.7 ohms.

Mr. Widget
01-07-2004, 10:44 AM
Originally posted by Giskard


Both the D8R075 and the D16R2405 are formed formed from 0.0022" aluminum alloy. Both have a 0.025" gap. Both have a DCR range of 5.7 ohms to 6.7 ohms.

Hey Giskard,

Are you sure about that? I read somewhere that the difference between the D8R075, D16R076, and the D16R2405 was the moving mass, with the 075 being the one with the most mass and the 2405 having the least mass. Ignoring the D16R076 for this discussion, if the VC and diaphragm material are the same, then how could the mass be different?

Widget

Earl K
01-07-2004, 11:18 AM
Hi there

- I have 20 yr old ( Fall, 1983) JBL service info that supports a contention for a different diaphragm mass ( or maybe different coil - though not likely with the duplicated DCRs ) . It comes from a service bulletin ( # 231183 ) that describes the difference between the regular 2404 and the 2404H-1 ( as found in the 4612 ). The published statement is; the replacement of the regular D162405 diaphragm with a D8R075 ( giving a 2404H-1 ) enables a lower cross-over point that's 1000 hz lower than whats recommended for the typical 2404H .

HP : FWIW, those Cannon Sound knock-offs are made with titanium vs JBLs' aluminum diaphragm type. You'll need to collect some opinions on what this swap in metal types may mean to your listening experience.
- On the other hand; the low worldwide prices charged by Cannon Sound put those diaphragms into a category of "Buy it & Try it - You Might Like It" . :D I'm thinking of buying a pair for my Altec 288s - just to compare against the original Altec aluminum types.

regards < .EarlK :)

Dieter
01-07-2004, 11:36 AM
Hi,

look at:
http://www.jblproservice.com/pdf/Goes%20Into%20List/03%20Goes%20Into%20List.pdf

in this list JBL wrote that the D16R2405 is for 2405 and 2404 and not for 2402.
The D8R075 is for 2402, 075 etc.

I've bought in the past from a guy 2 2405. I wondered, why they sound different. i opened them and i saw that the dias looked different. at one the aluminium dia was wider ( 1 or 2 mm ) than the other.
i asked him, and he said, that a german distributer (Thomann) told him the dias from 2402 and 2405 are the same, but i don't believe. yes they fit the 2402 and 2405, but they are different!
But i don't remember which one was the right one: the wider or smaller.

I hope this helps

Dieter

4313B
01-07-2004, 01:19 PM
Originally posted by Mr. Widget
Hey Giskard,

Are you sure about that? I read somewhere that the difference between the D8R075, D16R076, and the D16R2405 was the moving mass, with the 075 being the one with the most mass and the 2405 having the least mass. Ignoring the D16R076 for this discussion, if the VC and diaphragm material are the same, then how could the mass be different?

Widget What I posted is from JBL's own data. Whether that is correct or not is anyone's guess ;)

Back when I was actually messing around with the 075/2402 and 077/2405 transducers it never occured to me to mix and swap diaphragms so I never actually held both diaphragms side by side to note their similarities/differences. I guess I'm boring in that I only replace a D8R075 with a D8R075 and a D16R2405 with a D16R2405. It would never occur to me to buy an aftermarket diaphragm for a JBL so I can't really help in that respect.

Hofmannhp
01-07-2004, 03:18 PM
Hi folks,

first of all....thanks for your ideas....but I'm a little more confused in some points.
Whatever....I learned a lot.....I think I follow the words of EarlK ( the price for testing)...he maybe right....I will try it with some 2405 dias (with least mass). The different mass may be called " a different dynamical mass"-----(called Compliance). The result with a dia with less mass can only be better for what I want. Maybe I can push the high freq section a little over the 15k.
The main thing what I wanted to know was ...does it fit mechanicaly?.....ok.


thanks again

HP

Mr. Widget
01-07-2004, 03:45 PM
The aftermarket diaphragms being made of titanium will inherently have higher distortion than the original aluminum ones. This of course may or may not be audible, only a careful listening test will reveal that.

In my experience the titanium diaphragms used in the midrange do suffer a bit from this added distortion, but at UHF frequencies it will likely be much less of a problem.

boputnam
01-07-2004, 05:25 PM
Originally posted by Hofmannhp
Whatever....I learned a lot..... What I've learnt here, and elsewhere, is while swapping can work, best is sticking with design. Anything other is experimentation in something other than ideal (anechoic...) conditions.

But, as has been said, here, so long as no one loses an eye... ;)

subwoof
01-07-2004, 08:58 PM
All the diaphrams are interchangeable ( 2402 / 2403 / 2405 ) and are color-coded to distinguish.

As far as the gap, I use a plastic shim set to clean the gaps and all but the 1950's 075's seem the same. Alnico or ferrite.

The PITA alignment posts are sometimes out of alignment and require judicial elongation of the replacement diaphram to make them fit. This then required manual alignment with an oscillator before tightening the horn/wedge/plug located in the center.

If the coil rubs, suspect the magnet is weak and has shifted. ALL that holds them together is the magnetic strength...look ma, no screws! This is the same for the alnico 1" and 2" drivers

As far as thickness, since all else is the same, it seems logical that it's the only significant difference..???

BUT since these can go pretty high, it seems a minor issue if the 2402 can kill a bat while the 2405 can kill a teenage bat.

I have a wall of blown diaphrams that stretches back 30 years for reference sake - all the tweets are in one place and look the same.

One interesting variant was the "OEM" model sold to the railroad industry. They had special diaphrams that **seemed** to me to be stainless steel....?? I have to look and see if I can find one.

sub

Oldmics
01-09-2004, 01:48 PM
Quote from Giskard
"Back when I was actually messing around with the 075/2402 and 077/2405 transducers it never occured to me to mix and swap diaphragms so I never actually held both diaphragms side by side to note their similarities/differences. "

Well today I had that very opportunity.To do a side by side comparison.And you know what,appearance wise they are identical.HOWEVER- Now I question the application that is suggested from JBL in Earls post above.
The only reason that I did this is because the opportunity presented itself and I am personally looking for the differences in the older original 075 diaphragms that are rated at 16 ohms.
The D.C. resistance was found to within specs quoted by JBL.The voice coil former height and winding height was found to be the same on both units.
The weight however was found to be different between the diaphragms.This supports both Widget and Earls comments.
Weight was found to be heaver on the D16R2405 diaphragm at 6.5 grams.The weight of the D8R075 is lighter and weighs in at 5.5 grams.I weighed 4 of the 2405 diaphragms and 2 of the 075 diaphragms.The weights found were identical on each of the particular series of diaphragms.So if you don"t know whatcha got-weigh it for the answer!

I measured the thickness of the diaphragm and found the 2405 to be thicker at .050 and the 075 thinner at .045.(I suspect a potential for greater margin for error in my measurements due to the potential "crush factor" of the sandwich of materials).Again ,makes sense.If its thicker it will weigh more.

If the service manual that Earl is quoting from, recommends that the lighter weight 075 diaphragm can be used at a lower crossover point.How is this possible?How can a diaphragm that has less density be subjected to a greater operating range on its low frequency reproduction end where a greater number of non-linear vibrations are prevelant?
Or am I just splitting hairs over 1000 Hz?
Well thats it for todays saga.

Oldmics

4313B
01-09-2004, 02:16 PM
Interesting Oldmics! Thanks for the info :)

Earl K
01-09-2004, 04:12 PM
Hi Oldmics

- You've certainly brought forth some conflicting information. You're right, all other things being equal a heavier diaphragm should have a lower Fs. The problem here is that you've measured the weight of the whole assembly including mounting ring .


(A) So, to further your study on the matter here are some suggestions;

(1) Measure the Fs of each diaphragm type when mounted in a 2404. It would be useful if this was done in two ways; with and without the BiRadial horn in place. I suggest a 2404 because the horn should present a noticeable/readable load .

(2) If you have "cooked" diaphragms of each type ; cut away all the diaphragm from the mounting ring and then measure the weight of the mounting rings of the two types.

(B) An offered Adhoc explanation;

- It might be that the 2405 ( 077 ) is "purer" aluminum stock while the 2402 ( 075 ) is built wth a sort of Duraluminum alloy. These 2 alloys will have different Fs points. These two alloy distinctions used to show up in older JBL literature. The two alloy types would have different "fatigue" points .
- And it might be, that we are looking for a "higher" Fs to work within the 2404 horn. Apparently (I've never measured this ) - a properly loaded/constructed horn will "lower" a drivers' Fs. So ; the softer / thicker 2405 may actually have an Fs that drops "too" low when the horn is added. This Fs shift or "unloaded" condition might drive the need for a higher crossover point .

Just a couple of thoughts <. Earl K :)

Guido
01-09-2004, 05:34 PM
Originally posted by Giskard

Both the D8R075 and the D16R2405 are formed from 0.0022" aluminum alloy. Both have a 0.025" gap. Both have a DCR range of 5.7 ohms to 6.7 ohms.

Thats what I found

2402H and 2404H-1 use D8R075 0,0015" diaphragm

2404H and 2405H use D16R2405 0,0010" diaphragm

Of course they are interchangeable

JBL Data somtimes confuse;)

Oldmics
01-09-2004, 10:31 PM
Quote from Earls previous post

"The problem here is that you've measured the weight of the whole assembly including mounting ring ."

Correct

"(2) If you have "cooked" diaphragms of each type ; cut away all the diaphragm from the mounting ring and then measure the weight of the mounting rings of the two types."

This thought came to me as I was ascertaining weather the weight difference came from including the mounting rings or not.The particular diaphragms that I was replacing were cooked and pieces of the voice coil were missing.The required disassembly procedure would have to be preformed on a diaphragm that has all of the materials still intact so correct weight could be calculated.

I am sure that I am not explaining anything new to you here Earl.I just want clairification for anyone else who reads this thread.The real info lays in the fact that the weights were all exactly consistant in the various series of diaphragms.I feel confident in identitfying the two different diaphragms through the weight of each.I also wondered if the stamping angle may be different on the top edges of the aluminum.

If I have another opportunity to do Fs measurements on the driver I will do so.As you know reverse engineering is a job really based upon the tools availiable for the research.My little shop trying to second guess JBL-I don"t think so.

Best regards and thanks for the views,Always appreciated.

Oldmics

4313B
01-10-2004, 05:35 AM
Originally posted by Guido
JBL Data somtimes confuse ;) Well it's a combination of factors :) First would be the old standby - "JBL continually engages in research related to product improvement. New materials, production methods and design refinements are introduced into existing products without notice as a routine expression of that philosophy. For this reason, any current JBL product may differ in some respect from its published description but will always equal or exceed the original design specifications unless otherwise stated." Other factors could be typing errors and incorrect data. I have to admit that I have discovered conflicting data and incorrect data among JBL's documents over the years.


Originally posted by Oldmics
As you know reverse engineering is a job really based upon the tools available for the research. My little shop trying to second guess JBL-I don't think so.Good point.

Düse
02-06-2010, 04:42 AM
Thats what I found

2402H and 2404H-1 use D8R075 0,0015" diaphragm

2404H and 2405H use D16R2405 0,0010" diaphragm

Of course they are interchangeable

JBL Data somtimes confuse;)

..i have orderd a original jbl D16R2405.. the DC Resistance is 7,2 Ohms
messurement the same built in or not.

1audiohack
02-09-2010, 09:26 PM
Both the D8R075 and the D16R2405 are formed from 0.0022" aluminum alloy.


That's what I measure.



Are you sure about that? I read somewhere that the difference between the D8R075, and the D16R2405 was the moving mass, with the 075 being the one with the most mass and the 2405 having the least mass.


Right



It comes from a service bulletin ( # 231183 ) that describes the difference between the regular 2404 and the 2404H-1 ( as found in the 4612 ). The published statement is; the replacement of the regular D162405 diaphragm with a D8R075 ( giving a 2404H-1 ) enables a lower cross-over point that's 1000 hz lower than whats recommended for the typical 2404H .

Right


I've bought in the past from a guy 2 2405. I wondered, why they sound different. i opened them and i saw that the dias looked different. at one the aluminium dia was wider ( 1 or 2 mm ) than the other.


Right, good eye.


If the service manual that Earl is quoting from, recommends that the lighter weight 075 diaphragm can be used at a lower crossover point. How is this possible? How can a diaphragm that has less density be subjected to a greater operating range on its low frequency reproduction end where a greater number of non-linear vibrations are prevelant?
Or am I just splitting hairs over 1000 Hz?
-

The 075 assembly is lighter because the stationary rings are of different dimension, the outer ring has a larger I.D. and the inner ring has a smaller O.D. creating a larger radiating area. With the same 0.0022" material, this gives more moving mass than the 2405 and a lower spring rate equating to a lower FS. The lower safe frequency operating range is due to the fact the bending moment at the suround termination points are reduced by the longer distance edge to edge.


It might be that the 2405 ( 077 ) is "purer" aluminum stock while the 2402 ( 075 ) is built wth a sort of Duraluminum alloy. These 2 alloys will have different Fs points. These two alloy distinctions used to show up in older JBL literature. The two alloy types would have different "fatigue" points .
- And it might be, that we are looking for a "higher" Fs to work within the 2404 horn. Apparently (I've never measured this ) - a properly loaded/constructed horn will "lower" a drivers' Fs. So ; the softer / thicker 2405 may actually have an Fs that drops "too" low when the horn is added. This Fs shift or "unloaded" condition might drive the need for a higher crossover point .


I don't think so.

As a note the 2404H1 and the 2404 have different phase plugs, the plug in the H1 is smaller. Be sure of what you have and carefull if you mix parts.

Allanvh5150
02-09-2010, 09:54 PM
Ummmmmmmm..............why doesnt someone just measure the thickness of an old diapragm and compare the two?

Oldmics
02-10-2010, 01:22 AM
Good stuff there hack :applaud:

That question has bugged me for awhile.

Appreciate the input.

Oldmics-Old but never too old to learn !

1audiohack
02-10-2010, 08:53 AM
I did measure them, 11 of them, old ones, new ones, blue rings and gold rings, 075's and 2405's, with a Mitutoyo ball mic, they all measured 0.0022" within 0.0001".

Earl K
02-10-2010, 10:10 AM
The 075 assembly is lighter because the stationary rings are of different dimension, the outer ring has a larger I.D. and the inner ring has a smaller O.D. creating a larger radiating area. With the same 0.0022" material, this gives more moving mass than the 2405 and a lower spring rate equating to a lower FS. The lower safe frequency operating range is due to the fact the bending moment at the suround termination points are reduced by the longer distance edge to edge.

Good Info ( for this ancient thread ) .

To Paraphrase ( your findings ) ;

- The "2402 bullet" ( when compared to the " 2405 slot" ) has a larger diaphragm / "radiating area" ( the most important part of the complete assembly ) .
- This larger diaphragm results in a lower Fs which allows a slightly lower crossover point .

>< cheers

Allanvh5150
02-10-2010, 11:03 AM
So there does seem to be a lot af variance between .010 and .022. I do not have any old 2405's laying about so I cant do any measuring. I do know that one upon a time I checked this out and the 05 was noticably thinner and with a blue ring.

Allan.

subwoof
02-10-2010, 03:40 PM
Please read again what was posted. in engineering quickspeak he said that the *tolerance* was within 0.0001

That means 0.0021 to 0.0023


" I did measure them, 11 of them, old ones, new ones, blue rings and gold rings, 075's and 2405's, with a Mitutoyo ball mic, they all measured 0.0022" within 0.0001"."

Go Dawg Go
04-15-2010, 01:39 PM
Hey fellas,

New to Lansing Heritage...

I have been playing around with 2402's and 2405's for a while. I recently replaced my 2402's with aftermarket diaphragms and they sounded horrible. Joined Heritage to find out why? Poking around the internet and conversations with my friends at Orange County Speaker, I was told the diaphragms are indeed not interchangeable and a shim needs to be made from tape to offset the dimensional differences in the center phase plug seat (pole piece). Basically, the diaphram is bottomed out on the pole peice and doesnt permit proper excursion affecting efficiency and life of the diaphragm. I was also told there is no after market diaphragm for the 2402/075, just OEM. Anyone who says there is at this time is mistaken???
Attached is a "you tube" video which explains the offset and shimming. I just installed the tape shim on one of mine and I will let you know the outcome..

http://www.soundspeakerrepair.com/DWP_JBL_2404_1.asp

Tab down to the JBL-2404-Video Instruction

Thanks

Bob

4313B
04-15-2010, 02:57 PM
Here is JBL's final response on the whole ring radiator thing:

075/2402, 076/2403, 2404, 077/2405 (http://audioheritage.org/vbulletin/showthread.php?t=23869)

toddalin
04-16-2010, 10:11 AM
Hey fellas,

New to Lansing Heritage...

Poking around the internet and conversations with my friends at Orange County Speaker, I was told the diaphragms are indeed not interchangeable and a shim needs to be made from tape to offset the dimensional differences in the center phase plug seat (pole piece).
http://www.soundspeakerrepair.com/DWP_JBL_2404_1.asp

Bob


Eric Sundra at OCS actually has a plastic shim that I made and gave him when I was testing the 075 with the 2405 diaphram.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/Shim2.jpg
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/shim1.jpg

Rudy Kleimann
05-15-2010, 10:54 AM
So, Toddalin (and others in the know), how does the 2405 dia measure/sound in an 075/2402 driver?

Has anybody measured the frequency response of an 075/2402 driver with a 2405 diaphragm in it?

Would you dare say that this hybrid results in more extended UHF response than an 075 diaphragm in the 075/2402 driver?

I have pondered and researched this very question numerous times over the years, scouring JBL documents and everything I could find on the ring radiators on this website. I have learned a lot about these drivers and diaphragms, but never could get to the answer of this question. I always "knew" that the differences between the two diaphragms would end up being simple and straghtforward, but never had one of each to measure myself. Lacking sufficient test equipment and the funds to bankroll such an experiment, I have been hoping for all this to come out from the efforts of others more fortunate than myself...

I own an old pair of "bullets" that I'd like to use for UHF on a pair of long-throw 55* PA cabinets (horn-loaded 2012 from 300Hz and 2447/2383 crossed at 1250Hz). The coverage pattern of the bullets seem acceptable for this application, but I wasn't gonna go to all the effort of re-engineering the crossover and making cabinet mods unless I would get better response than the stock 075 would do, hoping to get all the way out to 20K.

toddalin
05-15-2010, 11:14 AM
So, Toddalin (and others in the know), how does the 2405 dia measure/sound in an 075/2402 driver?

Has anybody measured the frequency response of an 075/2402 driver with a 2405 diaphragm in it?

Would you dare say that this hybrid results in more extended UHF response than an 075 diaphragm in the 075/2402 driver?

I have pondered and researched this very question numerous times over the years, scouring JBL documents and everything I could find on the ring radiators on this website. I have learned a lot about these drivers and diaphragms, but never could get to the answer of this question. I always "knew" that the differences between the two diaphragms would end up being simple and straghtforward, but never had one of each to measure myself. Lacking sufficient test equipment and the funds to bankroll such an experiment, I have been hoping for all this to come out from the efforts of others more fortunate than myself...

I own an old pair of "bullets" that I'd like to use for UHF on a pair of long-throw 55* PA cabinets (horn-loaded 2012 from 300Hz and 2447/2383 crossed at 1250Hz). The coverage pattern of the bullets seem acceptable for this application, but I wasn't gonna go to all the effort of re-engineering the crossover and making cabinet mods unless I would get better response than the stock 075 would do, hoping to get all the way out to 20K.


If you are going to cross over to the tweeter at over 7,000 Hz, its a big improvement! It extends the HF and takes some of the 8-9kHz dip away. The dispersion in the verticle plane is actually better than the 2405.

Additionally, you can add an elastomaric band to the 2402/075 as a filter to slightly increase its dispersion and further extend and smooth the UHF even beyond that of the 2405/077.

Grumpy was present for this testing and we used his computer (CLIO I believe) to capture the data. Angles/distances were maintained using a length of string and protractor.

Yes, I had posted pics here, but they were pulled from the thread at the time and you will have to go elsewhere on the web to find them, if they still exist.

If I were to use 2402/075s in the home, I definately would have used the 2405 diaphrams with the shims. :applaud: But at the time I came across three 2405s with original diaphrams and the owner traded me straight across for three LE175s, two HL-91s (no lenses), and a potato masher I had on the shelf.

grumpy
05-15-2010, 12:12 PM
45730
Grumpy was present for this testing and we used his computer (CLIO I believe) to capture the data. Angles/distances were maintained using a length of string and protractor.Fuzzmeasure ... :)

0º on-axis
15º
22.5º
30º
45º

(do note that this was for -one- -specific- -modified- driver, spacer and 2405 dia...
no rubber bands)

Rudy Kleimann
05-15-2010, 01:28 PM
That just might work for me! Certainly worth a try now.

Thanks for responding, Toddalin and Grumpy.

Did you run any baseline benchmarks with D8R075 dias? In the same driver?

How does bringing them in at 7KHz take care of a dip above this?

What the "rubber band trick"? Where/how? Got any pics? Any charted results?

I like your shim much better than masking tape.

I like the "Marketing Spin": "Elastomeric" That'll sell...:p

toddalin
05-15-2010, 02:08 PM
That just might work for me! Certainly worth a try now.

Thanks for responding, Toddalin and Grumpy.

Did you run any baseline benchmarks with D8R075 dias? In the same driver?

How does bringing them in at 7KHz take care of a dip above this?

What the "rubber band trick"? Where/how? Got any pics? Any charted results?

I like your shim much better than masking tape.

I like the "Marketing Spin": "Elastomeric" That'll sell...:p


The magnet was recharged and OCS installed a brand new 2405 diaphram so the tweet was basically as new.

Yes we did both baseline and with the elastomeric filter in place, and I believe that Grumpy may have the data.

They could be crossed a little lower, but I note above 7K because this is typically about the minimum used with the 2405 diaphram that has less mass (because of less surface area) than the 2402. The Jubal crosses over at 6,500 Hz. Regardless, that dip you see between 7-10K is worse on the 2402 than what you see here.

The elastomeric filters are obtained in the produce deparment of the grocery market and are typically found holding bunches of asparagus or broccolli. Most are purple in color.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/DSC_0038.jpg

This is about where it will end up.
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/DSC_0039.jpg

It must be applied in real time with simultaneous monitoring. Playing pink noise and watching an RTA, the band is simply slid over the "nose cone" and pushed toward the gap using a toothpick/thin stick. Watching the RTA, just before the gap is closed, the UHF will extend and flatten out. If you go too far, hook the band with a bent pin and pull it back out for another try.

The cost is volume, but using this method, you can actually even get the 2402 diaphram to extend and smooth its response above 10KHz almost to that of the 2405.

Rudy Kleimann
05-15-2010, 02:30 PM
and measuring with my calipers. I'll post all my findings when I'm done.


Does anybody know the difference in pole piece height between the 2404H and the -1 variant?

IIRC, Zilch posted pics (and dimensional measurements?) of two different phase plugs from 2404's. I'll PM Zilch about this... it would take me forever :p to manually review all his threads to find this...

I have here on hand for measuring dimensions:

1-AlNiCo 075 with the "ring clamp" mounting plate from early/mid '70's
1-AlNiCo 2402 with the "new style" mounting flange from early/mid '70's
1-2404H-1? (rear label missing) from a JBL4612B * I can almost make out 2404H1 in very small (much smaller than I've seen on other 2404's) white ink print on magnet
1-2405 w/2404H-1 magnet (eBay auction)
1-2405 w/ ? magnet (same eBay auction)

I'll FINALLY KNOW what I have...

ivica
08-22-2011, 03:25 AM
Eric Sundra at OCS actually has a plastic shim that I made and gave him when I was testing the 075 with the 2405 diaphram.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/Shim2.jpg
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/shim1.jpg

What is the thickness of the mentioned "shim" materila

toddalin
08-22-2011, 11:04 AM
~ four sheets of paper thick.

Lee in Montreal
08-22-2011, 11:28 AM
~ four sheets of paper thick.

Which translates into 0.40mm or 0.0155" :D

toddalin
08-22-2011, 11:58 AM
Which translates into 0.40mm or 0.0155" :D

I found it on-line. It's 0.30mm. They also have 0.20mm and that would work.

I used STSC-2

http://plastruct.com/picat/STRIP_ROD_9.pdf

ivica
08-23-2011, 04:44 AM
~ four sheets of paper thick.

Thanks:bouncy:

ivica
08-25-2011, 07:23 AM
I found it on-line. It's 0.30mm. They also have 0.20mm and that would work.

I used STSC-2

http://plastruct.com/picat/STRIP_ROD_9.pdf

as i can see STSC-2 is 0.03" = 0.76mm, I think too large??

toddalin
08-25-2011, 10:50 AM
Not too large as it worked fine. But you can also go with STSC-1 at 0.5mm (0.020").

ivica
08-31-2011, 07:51 AM
Not too large as it worked fine. But you can also go with STSC-1 at 0.5mm (0.020").

I did some experiments,
http://www.audioheritage.org/vbulletin/showthread.php?6368-Ring-Radiator-Comparisons&p=319363&viewfull=1#post319363

and the conclusions are:
- response become "more flat" BUT
- High Freq. bandwidth reduced
- efficiency reduced

toddalin
08-31-2011, 11:05 AM
When I was looking into the effects of the shim, I was using a 2402 diaphragm. All the effects you show are above 16KHz and almost above audibility. The 2402 never gets that high to see these differences.

2402 without shim. Note the "hole" we discussed.
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/2402c15.jpg

2402 with shim. The "patterns" are essentially the same and this may even be a bit smoother across the band.
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/shimc15.jpg

ivica
09-05-2011, 12:41 AM
When I was looking into the effects of the shim, I was using a 2402 diaphragm. All the effects you show are above 16KHz and almost above audibility. The 2402 never gets that high to see these differences.

2402 without shim. Note the "hole" we discussed.


2402 with shim. The "patterns" are essentially the same and this may even be a bit smoother across the band.


Yes I understand that, and interestingly even the dias were different some of the conclusions remain :
-less efficiency
-"flatter" response,
but less UHF part is visible on 2405 dia as been expected too.