akirk Posted August 19, 2003 Share Posted August 19, 2003 I have read in another forum about a tweak for paper speaker cones which uses a decoupage sealant called "Mod Podge" (evidently available at Wal Mart). They recommend that you use a foam brush to apply the sealant to the paper cone - three coats for the front of the cone and two coats for the rear. The speaker dust cap and surround are not coated. From what I gather, this is supposed to seal up the pores in the cone and also stiffen it, resulting in better sound. Has anybody tried this, and does it work? Is it worth the effort? Quote Link to comment Share on other sites More sharing options...
marksdad Posted August 19, 2003 Share Posted August 19, 2003 seems to me the cones were made the way they were, out of the material they were made of, for a reason. i could understand if we were talking about bose, but? if it aint broke why fix it? Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted August 19, 2003 Share Posted August 19, 2003 That's a new one on me. I think it would stiffen the cone, but I'm not sure what the resulting change in sound would be. I'd be interested to read the thread on the other forum. Do you have URL for that? Thanks. Dee Quote Link to comment Share on other sites More sharing options...
prodj101 Posted August 20, 2003 Share Posted August 20, 2003 I don't think I would do that....seems just a bit to, too, eh....I don't think the resulting sound would be good. paper cones color the sound less than any other driver material (when made properly) and I don't think modifying them would make them better of companies like eggleston would be doing it. Quote Link to comment Share on other sites More sharing options...
akirk Posted August 20, 2003 Author Share Posted August 20, 2003 Check out this url for info on this: www.t-linespeakers.org/design/tweeks.html Quote Link to comment Share on other sites More sharing options...
ZAKO Posted August 20, 2003 Share Posted August 20, 2003 It will change the MASS of the cone. And may lower Fs but thats not a bad thing (if you know what your doing) I prefer a mass ring at VC at least it can be reversed if I dont like the results. Quote Link to comment Share on other sites More sharing options...
djk Posted August 20, 2003 Share Posted August 20, 2003 The added mass is very low when done right. Read this first: http://db.audioasylum.com/cgi/search.pl?searchtext=damar&b=OR&topic=&author=&date1=&date2=&slowmessage=&sort=score&sortOrder=DESC&forum=hug Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 21, 2003 Share Posted August 21, 2003 I'm not sure what the point is. Since Qes is usually 10X lower than Qms lets just ignore Qms. Fs is inversely proportional to Mm1/2. Qes is linearly proportional to Mm and Fs so this means that Qes is proportional to Mm1/2. So added mass increases Qes and affects Qts (it also effects Qms but that effect is minimal). To realize an increase of 20% in Qes the Mm has to change by 1.45X higher. That means that you've got to add about half the moving mass of the driver in glop. It also assumes the builder has very accurate T/S parameter measurement capability at his/her disposal. I see this as a messy, potentially ruinous effort for a change in damping. Also (last point), a simple regression will demonstrate the drivers with low Qes cost big bucks. The reason is simple, Qes is inversely proportional to (B*l)2. So, the bigger the motor the higher the electrical damping of the transducer. Adding mass to the cone offsets the effect you pay for in motor cost. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted August 21, 2003 Share Posted August 21, 2003 But in this instince nothing is being done to the motor just glopping on filler to the cone (MASS) Get out my slide rule It shows alot changes. Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 21, 2003 Share Posted August 21, 2003 Yes, you do reduce Fs. Say you increase Mm by 1.4X, then Fs drops to 84% of the value it was before you added the glop. That also means Qes increases by 1.18X (since it goes as the sq. rt of Mm). Since Qes is inversely proportional to (B*l)2, a reduction in B*l product to about .90 of its original value will yield an increase in Qes by 1.18X. So, as far as Qes goes, adding the glop is NO DIFFERENT than reducing the flux density in the gap by 10% OR reducing the length of wire in the coil by 10%. Either way the damping afforded by the motor structure is reduced. There is no *good* or *bad* Qes but when you consider the $$$ of drivers, the lower the Qes the higher the cost gets. Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 21, 2003 Share Posted August 21, 2003 The other thing I forgot to mention was the *hit* you take on reference effeciency. The reference efficiency of a driver (unmounted) is proportional to Fs3 and inversely proportional to Qes. So adding mass to Mm causes Fs to go down, Qes to go up resulting in a drop in efficiency. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted August 21, 2003 Share Posted August 21, 2003 Thats the difference I see between JBL 2234 & 2235 but instead of painting the cone I use a mass ring. Witch is reversable painting IS NOT. I go full circle on how not to destroy the cone. Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 22, 2003 Share Posted August 22, 2003 Here's a graph of Qes vs Bl-product for about 1300 drivers. Note that BL-products of ~20 Tesla-m or more get very expensive. Here's Mms vs. Fs for the same group of drivers. Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 22, 2003 Share Posted August 22, 2003 Sensitivity vs Bl-product (B l). Big surprise! Force is equal to i x (B l) where i =current running thru the voice coil. The force is the force applied to the cone at the cone apex by the voice coil. If (B l) is large, the force is large, the SPL which is force/area for a given power level is then large. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted August 22, 2003 Share Posted August 22, 2003 I got a heat rash on my butt that looks like your charts. Thats an awful lot of words for a geeky answere. But as I pick my self up off the floor....A simple answere would suffice... SOME LOWER EXTENSION IN BASS & LOWER EFFIENCY. MINE IS STILL REVERSIBLE. Paint your walls not your speaker cone. John I got my pair of 2123,s but Im going to use them on some thing else. Also still editing K papers. Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 22, 2003 Share Posted August 22, 2003 ---------------- On 8/22/2003 8:33:28 PM Maron Horonzak wrote: I got a heat rash on my butt that looks like your charts. >>I didn't need to know that. Next time I'll post blue data points! John I got my pair of 2123,s but Im going to use them on some thing else. Also still editing K papers. >>Good! Nice driver. I found that they work best in pairs, the coverage between 3-5kHz is better. ---------------- Quote Link to comment Share on other sites More sharing options...
efzauner Posted August 22, 2003 Share Posted August 22, 2003 The increase in mass with resulting change in TS paramters is one thing. But another consideration is the change in the material properties themselves. The cone material, construction, and shape also affects the resonant modes of the cone (piston) itself. The cone should be going straight in and out, but at high frequencies it vibrates in different modes. Think of a kettle drum: depending on how the musician hits it, it will sound different. This is called moding, or cone breakup. These modes will add colloration/distortion to the sound. Mod Podge may make the cone stiffer, but it may also be less damped. One of the main effors of speaker research is into materials that will push the cone moding frequency higher and higher. This is why you also see many high end audiophile type speakers with 6 inch cones crossed over at 2-3Khz. Also why the Klipsh reference have very rigid ceramic cones and can work well till almost 2KHz Another point: How do you know what this mod podge will age like? Put it on and in 5-10 years it may change in ways you wont like. Quote Link to comment Share on other sites More sharing options...
marksdad Posted August 22, 2003 Share Posted August 22, 2003 darn john, you are smart, i wish i could explain things like that Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 23, 2003 Share Posted August 23, 2003 ---------------- On 8/22/2003 8:33:28 PM Maron Horonzak wrote: A simple answere would suffice... SOME LOWER EXTENSION IN BASS & LOWER EFFIENCY. MINE IS STILL REVERSIBLE. ---------------- Adding mass to the cone affects the electromechanical action of the driver. It affects the Fs, Qes, Qms and Qts which means it affects the basic design of the system as a whole. A change in Qes of, say 30%, in more than enough to negate the design alignment of a high quality system. To *understand* what adding mass to the cone means is quite involved. Adding mass is useful only if you know how you are affecting the system. Most DIYers (myself included) do not have the experimental resources to make the acoustic measurements to determine the cause and affect relationships. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted August 23, 2003 Share Posted August 23, 2003 AMEN Quote Link to comment Share on other sites More sharing options...
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