Emit-r damaged?

[Fleime]

Hello,

Although the following has nothing to do with the post title, just to be polite, I will give a short introduction. I am, obviously, new here but I have been reading posts from this forum for some time now. I am from The Netherlands and have been caught with the Infinity virus, though to be honest I have not caught any other speaker viruses so I can not really compare. I currently use Infinity Reference 50 speakers (somewhat akin to the Reference Five) and also have in stock, awaiting repair (surrounds obviously), a pair of Reference 60 speakers (somewhat akin to the Reference Six) in otherwise very good condition. Both sets of speakers have IMG cones and emit-r tweeters.

(Vintage) Infinity speakers are not as common/available here as in the USA, and accordingly the prices are relatively higher in these parts (I can only dream of some of the 'grabs' that have been mentioned). Hence, I have to be somewhat careful when acquiring vintage Infinity stuff.

Which brings me to the post of my title. I am considering acquiring a Kappa video center II to go with the main speakers, which has an emit-r tweeter. Although I have gained some insights in the quality of an emit-r, I am not sure when an emit-r is considered (too) damaged. Concerning the emit-r from the center, I have posted some pictures below. My main concern is the black spot or missing piece of ribbon (is it the ribbon, or diaphragm, or are those the same thing?) in the southwest part of the tweeter near the edge. Is this considered damage and if so, is it too severe? Or is this not possible to determine this on sight alone? Can you measure the quality of the tweeter, e.g. with impedance? And if through impedance, what should the readout be (or not be)?

Your advice is appreciated.

 

[goodolpg]

Yes, you can measure the speakers resistance (ohms) with a multi meter.
If you get no reading it very well could be broken. If you get a reading (just guessing around 4 ohms, maybe someone will know for sure ) that should mean it is fine.
It might just be a piece of stuff, but I see some bubbles in the trace closer to the center as well.

 

[markuus3889]

Hi Fleime,

Welcome! If the silver line (actual voice coil on diaphragm) is missing or broken or cracked the diaphragm for all practical purposes is damaged and most likely not able to be satisfactorily repaired. This is most definitely measurable on a resistance meter and a typical Emit-R is around 4.0 ohms +/- .5 ohms. For instance my Emits measure 3.7 ohms. On the older Emits it was possible to get a very high resistance measurement that was due to aging solder connections from the voice coil wires to driver tab connectors. This could be fixed by reflowing the solder.

Good luck,

Mark K.

 

[Fleime]

goodolpg and markuus3889, thanks for your replies and advice.

@goodolpg: I am not sure I can see the bubbles you mention. Do you mean the grey spots between the black spot mentioned and the center? If not, could you point out the locations of these bubbles?

 

[tubed]

Remove the four screws holding the tweeter diaphragm in place and remove the diaphragm.
Cut a tiny sliver of aluminum foil to bridge the gap, place the sliver on a small piece of scotch tape.
Trim the tape down just enough to stick, carefully apply to bridge the gap.
Have fun.

 

[goodolpg]

Hi Fleime,

Welcome! If the silver line (actual voice coil on diaphragm) is missing or broken or cracked the diaphragm for all practical purposes is damaged and most likely not able to be satisfactorily repaired. This is most definitely measurable on a resistance meter and a typical Emit-R is around 4.0 ohms +/- .5 ohms. For instance my Emits measure 3.7 ohms. On the older Emits it was possible to get a very high resistance measurement that was due to aging solder connections from the voice coil wires to driver tab connectors. This could be fixed by reflowing the solder.

Good luck,

Mark K.[/QU

goodolpg and markuus3889, thanks for your replies and advice.

@goodolpg: I am not sure I can see the bubbles you mention. Do you mean the grey spots between the black spot mentioned and the center? If not, could you point out the locations of these bubbles?

Yes, in the second picture between the black spot (about 7:00) and the center, looks like 2 or 3 bubbles (small sections of lifted traces?), could be dust or something else. Can't see them in the third picture, maybe the piece of frame is hiding them.
Lifted traces are quite common and as long as they aren't actual breaks it should be ok.

Oh, you will need at least one of the EMIT wires disconnected to get an accurate Ohm reading. Easy if they are push on crimp connectors, a bit harder if they are soldered. Just looked at a couple pair and it appears they are push on and not soldered.
For the resistance (ohm) test remove the THREE outer screws. DO NOT remove the 4 inner screws unless you will be attempting a repair. Once you have a resistance reading (or no reading) we'll know if you need to go further.

 

[Fleime]

Well I contacted the seller and he measured the impedance at 4.25 ohms, see picture. About the supposed breaks or bubbles the seller claims these are dust particles, but he will be sending another picture to confirm this. If correct, I do not see any other objections, unless you guys have something else to add.

 

[markuus3889]

Should be good!

Mark K.

 

[goodolpg]

Resistance reading is good.
What are your main speakers?

 

[Fleime]

Well I have the following updates (and questions):

First, @goodolpg: my main speakers are currently the reference 50. I bought these with poor knowledge and discovered the bass woofers both had voice-coil rub. So I got somewhat cheated there. Otherwise the speakers were fine (enough). I replaced them with woofers from a reference four originating from the USA and acquired on ebay, knowing they were not the exact same replacements. I still don't know if there are any performance consequences due to this swap, because I can't compare them to the original. Anyway, upon receiving the reference four woofers it appeared one of the gaskets had been broken and glued back together. Though perhaps not the biggest of issues, I felt slightly cheated there as well. Ah well, at least there is international consistency. As stated earlier I also have a pair of reference 60 in oak veneer acquired from the original owner and, as far as have been able to determine, in very good condition, except the surrounds need replacements (which I will outsource since I have no experience on the matter).

Back to the subject, the seller informed me that he tried to clean the above mentioned emit-r, and consequentially broke it.



Since the seller had two centers available, he offered to exchange the emit-r's. He checked out the resistance and, admittedly, it did look better on the outside than the first one.



After agreeing upon the purchase, and receiving the center, I immediately noticed the right woofer (when looking at the front side) had a crack in the cone, patched together with a bicycle tire repair patch (well points for ingenuity).



The crack is also sort of visible in the picture in my first post, where the light is somewhat distorted. And luckily for me, I had retained a picture from the seller from before the sell took place, where the crack is also discernible (now knowing what to look for). Current status is that I confronted him (respectfully) with the issue and he has offered to exchange the damaged woofer for another one from his other center. I must acknowledge that he had offered to sent me the other center in the first place, so I will file this issue under the heading 'honest mistakes' for now.

However, doubt continues upon inspecting the emit-r. It appears to be the correct type of emit-r for the speaker, although I am not used to the second magnet on the back. After searching I have noticed that the design is not uncommon. Is this for magnetic shielding or just a different design? There is no usual type number present (like 902-xxxx). There is another number that yields no results on the internet (831TNG), though I have seen similar numbers on other pictures of emit-r's. Lastly, the tweeter is partly covered with something like petroleum jelly, and it gives me the impression as if it has been tampered with. Has anyone got an opinion based on these observations?

 

[jazzmans]

it's for shielding I'll bet. All Emit-Rs were the same construction. long as it measures ~3-4 ohms you're fine.
No Idea about the dielectric gell, (vaseline)
that cone is no bueno! good thing he offered the center.. is it the precisely same driver by number? post em up and we'll verify.

Who here has kappa centers? can you check your emits? it'd be nondestructive, just check for the second magnet and the jelly.

 

[markuus3889]

I recently rebuilt my Kappa center series 1 and the rear magnet is for Magnetic shielding and normal! I am not sure about the "petroleum jelly" and mine was dry like every other driver I've tinkered with.

The "831 TNG" is an infinity numbering scheme and likely signifies batch.

Mark K.

 

[Fleime]

@jazzmans : I am not sure on the same construction statement, as most emit-r's I have seen are without the additional magnet, though perhaps that is not what you are saying.

Heading into the realms of conspiracy here: I noticed an 'orange horizontal band' on/behind the ribbon on the front of the emit-r, present or visible on the yellow circle:



Not having seen this before I googled it but could not find it, or discern it (flashy ribbons), on other pictures of the "kappa emit-r series II". I did however find it on other (older?) emit-r's, predominantly on the 902-4578A and 902-4578C types:

https://www.aussieaudiomart.com/details/649222888-infinity-emitr-tweeter-9024578c/images/1051036/
https://www.worthpoint.com/worthopedia/infinity-emit-ribbon-tweeters-pair-171485147
https://www.finn.no/bap/forsale/ad.html?finnkode=155123994
https://www.ebay.com/p/1001727108

902-4578D not so much: https://archiwum.allegro.pl/oferta/emit-r-infinity-glosniki-wysoko-tonowe-i7098056162.html

Am I possibly correct in these findings, or can someone prove me wrong? And if possibly correct, could it perhaps be that the emit-r has been repaired with another ribbon, and the jelly used to put a (perhaps stubborn) magnet in place? Just wildly guessing here, I do not know anything about repairs. And finally, if so, any ideas on the possible consequences or performance?

 

[jazzmans]

those emits look fine to me, and I have 10 different emit-r's around the house, not including all the original emits(10 or 11) I have.

if they measure fine, they're likely fine.

I think the second magnet was a modification done to make the emit-R magnetically shielded, and has no other purpose, nor influence on the sound of the Emit-R, that's what I was trying to say earlier.

 

[Fleime]

those emits look fine to me, and I have 10 different emit-r's around the house, not including all the original emits(10 or 11) I have.

if they measure fine, they're likely fine.

I think the second magnet was a modification done to make the emit-R magnetically shielded, and has no other purpose, nor influence on the sound of the Emit-R, that's what I was trying to say earlier.

Thanks for your clarification on the second magnet. Was shielding only necessary with tube tv's or is it still useful with flat tv's?

It is not the fact that the emit measures and perhaps works fine, it is the fact that I have been told that the center is in great condition and all the parts are original.

Meanwhile, I have purchased the same type of center from Hifinity, a company that restores (older) Infinity's and some other brands, located in Germany. I showed him the pictures of the suspected emit as well and they are of the opinion that the front part containing the ribbon has been replaced. I informed the first seller and based on the woofer and the emit, he has kindly offered to cancel the purchase.

However, I have offered him to compare the two centers performance wise (and personal curiosity) before returning his, once I have them both, and he has agreed. I suppose it would be handy to listen to both centers simultaneously instead of swapping out cables all the time, should I temporarily hook them up as my main speakers?

 

[swechsler]

Thanks for your clarification on the second magnet. Was shielding only necessary with tube tv's or is it still useful with flat tv's?

Flat TVs (and pretty much all other modern electronic components) aren't bothered by magnetism. Even a hard drive sitting right on top of a speaker wouldn't be damaged.

 

[markuus3889]

I recently rebuilt my Kappa center series 1 and the rear magnet is for Magnetic shielding and normal!

Well I apologize, my Kappa center does not have the second magnet on the emit-r it was a sony center I was thinking of. Sorry for the misstatement! The second magnet was used for Magnetic shielding and added by someone and probably a good idea if the person had a tube TV in use with the center. I am actually surprised the Kappa Center doesn't have shielding since there were a lot of tube TV's in use when the speaker was made and it was a presumably expensive center channel..

@Fleime I wouldn't get too hung up on the diaphragm as Jazzmans has said if it functions and resistance measurements checkout. Modern TV's (flat panel LCD) are not affected by speaker magnets like a tube TV and since a center channel is usually in close proximity to the actual source of visual entertainment the magnet should have been shielded so as not to affect the tube TV picture quality. Also VHS tapes and any magnetic tape types should also not be kept in close proximity to your unshielded speaker drivers. I was once told a couple of feet away and you're safe.

Good luck,

Mark K.

 

[Fleime]

@markuus3889 , @jazzmans , @swechsler , @goodolpg

Meant to round this up earlier, but better late then never. So I tested both centers simultaneously and there was no difference in the emit-r's that I could distinguish. The cracked cone as expected didn't perform well. I was able to send that center back and kept the other one. Now happy with a decent center.

Thanks for your help!