Hi,
Rabbitz is correct - Peerless used that snap in magnet arrangement.
You have a choice of 5 versions from madisound for $7 each ......
/sreten.
Rabbitz is correct - Peerless used that snap in magnet arrangement.
An externally hosted image should be here but it was not working when we last tested it.
You have a choice of 5 versions from madisound for $7 each ......
/sreten.Yes, I just found that page, noticed the Peerless snap-in similarity, could not find the exact 811877 number, but looked at the Madison page, and they list part numbers those diaphrams replace but none match exactly, and none are the aluminum ones. Well, for $7 each I'll get a pair of fabric ones and try them. Now, do I need to do anything about the fluid?
timbert said:
You certainly could try this. Nothing looks too badly damaged. If your lucky the resisters have acted as fuses for your main drivers. The caps look good. You could replace them with similar values for very little money even for better caps.
timbert said:
I would guess that the coil will remove with some pressure applied. Looks to me more that the glue holding it together has melted. it probably is just knotted up inside the groove. It may come out
Cant really see abrasions on the tweeter in your picture, but yep that tweeter must have been moving some to damage it. The dome is pretty scratch resistant (I'm clumsy, I know this for sure)
No its not oil (well not really) thats reached out of the magnet, its ferrofluid. It normally sits in the groove, held there by the magnet (Its magnetic you see) You will probably have heard the term before, the stuff basicly acts as a coolant for the tweeters voice coil. Looks like your tweeter had a violent enough death that the fluid splashed out.
timbert said:
I would be very interested in where this quest takes you. Replacement drivers may be an upgrade I would be interested in.
FWIW, When researching the speakers, I could find little information about them in the public domain though i am rather talentless when it comes to googling. However I believe (from what I have read anyway) the missions cross their tweeters at about 2.1khz. You should be looking I believe for a replacement thats flat in its response to below this figure.
Give me a few days for the parts to arrive and I'll post my experience. I have not heard back from an email to Mission, but I ordered the closest approximate replacement voice coils, in fabric not the original aluminum, and a couple 2.2 ohm resistors, but they only had 10W, not the original 5W, from Madisound. I assume that higher power handling is ok, and that the cylindrical shape, not square cross-section like the original, is ok. I also found these discontinued Peerless tweeters for $10 each on ebay, and they are close to the original model number and appear to be aluminum-domed, but are listed as 8 ohm when my originals are 4. I think I will leave the old fluid in the old tweeters and just put the new coils in and see what happens. Then if that doesn't work I'll install the 8 ohm tweeters, figure out if I have to modify the crossover, and try it. Until today I had never taken a tweeter apart, so I appreciate the confidence and expertise you guys have all given me. Also justblair's schematic appears to be the same as what I have, though the layout is different.
Attachments
timbert said:
Hi,
811877 will be a Mission only driver. As I recall the tweeters are
are sandwich, i.e. aluminium foiled fabric domes. Ideally you should
keep the ferrofluid, any differences in the tweeters can be adjusted
carefully with kitchen paper edging mopping up oil.
I'd go for the 811830 diaphragm, level may need adjusting in the c/o.
TBH the main voicing of a speaker does not depend on the tweeter.
I think you will be fine with new diaphragms - also see :
http://www.speakerdesign.net/tweeter_tweaks/tweeter_tweaks.html
/sreten.
I have had that tweak on my bookmark for some time. Just haven't seen the lambswool that is reffered to on my travels since I vowed to try it.
There is a scholl store in town, I must remember to sweep by it and get some of the lambswool.
The foam blug in the tweeter looks very low tech. I guess there is room for improvement there.
Very keen to hear howyou get on with the fabric dome. If it works, I will try changing over from metal to fabric. Its relativly cheap, and may be an improvement.
There is a scholl store in town, I must remember to sweep by it and get some of the lambswool.
The foam blug in the tweeter looks very low tech. I guess there is room for improvement there.
Very keen to hear howyou get on with the fabric dome. If it works, I will try changing over from metal to fabric. Its relativly cheap, and may be an improvement.
ashok said:
I have a friend who also had a bad woofer in a mission 780. The man from the shop said that the 78 series all had bad woofers. He had to replace dozens of them. They were made by AUDAX and had a problem with some coating that burned into the isolation of the wires.
After a year or 2, mission noticed the problem and the later models had a new type of woofer.
You should replace the 2 woofers, because the other one will also go bad.
Just to keep this thread clear, there are four identical woofers in each speaker in the Mission 753. All my woofers are okay, just blown tweeters and crossover resistors at this point. Here's sreten's photo again. I will update this thread when the new parts arrive. I'd like to emphasize I bought these for a few dollars from someone that seriously abused them and for a few dollars I believe I can get them up and running again.
Attachments
sreten said:Hi,
Just to be clear the c/o schematic would be helpful if an 8 ohm coil is
going to be used instead of a 4 ohm one . I can suggest the sensibe
c/ o mods for the above case.
(and its likely not putting an 8R in parallel with the new tweeter).
It, according to a previous post by timbert is the same as this one.
Hi Diy_peter,
I got my replacement drivers just last year and so they must be the new ones.
The old ones had a small sector ( about 1cm ) on the surround that had turned hard ( inflexible ) and eventually cracked .
Funnily it happened to both drivers at exactly the same spot Bottom part of the surround as you look at it. It was also "moist " inside !
The driver seems to be OK so far. I wouldn't spend any more money on it !
Cheers.
I got my replacement drivers just last year and so they must be the new ones.
The old ones had a small sector ( about 1cm ) on the surround that had turned hard ( inflexible ) and eventually cracked .
Funnily it happened to both drivers at exactly the same spot Bottom part of the surround as you look at it. It was also "moist " inside !
The driver seems to be OK so far. I wouldn't spend any more money on it !
Cheers.
justblair (...)
iT IS DIFFICULT TO BELIEVE THAT SOMEONE HAS (sorry) a 2R2 7W (or less from it's size) in series with the power woofers... Maybe a 50W would fit (or don't abuse it).
timbert do you have new components?
I would probably "erase" that resistor from the filter if it can be redesigned. One way of doing it is to get new high intern. resist. inductors at least for Nº1.
iT IS DIFFICULT TO BELIEVE THAT SOMEONE HAS (sorry) a 2R2 7W (or less from it's size) in series with the power woofers... Maybe a 50W would fit (or don't abuse it).
timbert do you have new components?
I would probably "erase" that resistor from the filter if it can be redesigned. One way of doing it is to get new high intern. resist. inductors at least for Nº1.
Hi,
the 2.2R resistors will increase the Q of the bass alignment.
Reducing / omitting it will tighten lower bass somewhat but
may increase upper bass.
Worth experimenting with 1R here ?
FWIW peak power handling of a 10W resistor is around 2KW.
The problem was no ventilation and lots of juice.
For the 8 ohm Tweeters a parallel 6R resistor is useful for trials.
If acceptable ideally values would be scaled for 8 ohm. It does
depend on if additional attenuateion is needed what to do.
/sreten.
the 2.2R resistors will increase the Q of the bass alignment.
Reducing / omitting it will tighten lower bass somewhat but
may increase upper bass.
Worth experimenting with 1R here ?
FWIW peak power handling of a 10W resistor is around 2KW.
The problem was no ventilation and lots of juice.
For the 8 ohm Tweeters a parallel 6R resistor is useful for trials.
If acceptable ideally values would be scaled for 8 ohm. It does
depend on if additional attenuateion is needed what to do.
/sreten.
justblair said:
I don't mean that, I'm just saying that he can increase power by using two or four resistors (10W) making it 20 or 40Watts. 7W is low, not enough. Or to make sure, check to see if it is very hot -> high compression and distorsion. You mention the factory, now (sometimes/most of the times) they don't use the components they should, that's for a fact.
sreten said:Hi,
the 2.2R resistors will increase the Q of the bass alignment.
Reducing / omitting it will tighten lower bass somewhat but
may increase upper bass.
Worth experimenting with 1R here ?
FWIW peak power handling of a 10W resistor is around 2KW.
The problem was no ventilation and lots of juice.
For the 8 ohm Tweeters a parallel 6R resistor is useful for trials.
If acceptable ideally values would be scaled for 8 ohm. It does
depend on if additional attenuateion is needed what to do.
I'm lost here sreten, I clearly have a lot to learn on crossovers... I might have a play with this though.
Inductor said:
Fair point about the factory, they have to make a price compromise somewhere. However looking at the example of blown speakers this thread aludes to, The tweeter blew at high volumes as did the resistor, but the bass drivers survived.
The resistor concerned blew when the speaker was clearly operating well outside spec.
I have had my missions for many years. I have never noticed distorsion or compression from these speakers even at party volume. My living room is slightly above average size for a UK household with high ceilings.
I really dont think that the 7w rating of this resistor is anything to worry about. I'm trialling 5w resistors in the speakers at the moment. I have one speaker wired with the 5w, the other with the standard resistors. When I get back from my travelling, I will give each a high volume burst and see if i can detect compression or distorsion from the lower powered resistor.
If it shows up it will indicate the 7w value is marginal. Even then i cant see any more than 10w being practical. Get into the higher values and the tweeter will pop anyway.
justblair said:
It all depends on the use of them (speakers) and you are forgetting about the peaks and transients.
justblair said:
Well, it shouldn't. You can have a polyswitch or lamp for that mater. Is the cap fine or not?
timbert you didn't post your xover, this is jb's. I assume your's the same.
The 4 Ohm section on the tweeter is very important now, since the xover was designed for a 8 Ohm section, I'm guessing.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.