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Multi-Way Conventional loudspeakers with crossovers

Help with troubled JR149 driver
Help with troubled JR149 driver
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Old 31st August 2015, 05:11 PM   #1
bbbiker800 is offline bbbiker800
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Join Date: Jul 2015
Default Help with troubled JR149 driver

Hi All - this is my first post and i'd like to ask for your help with a problem that I have with one of my JR149's. I brought these a while back at a lowish price and I've just got around to checking them out. The seller said they were perfect.

However....after adding new banana plugs, reconnecting to clean terminals, cleaning the fuse contacts, adding new fuses, checking the connections in the block connector (drives to XO) and cleaning the treble adjuster thing with a contact cleaner (as I could hear a very fizzy top end on what is now the problem speaker). That left me with what sounded a good pair or JR149's.

However within 10mins of Frank Sinatra 'Live at the Sands' one speaker became much lighter in the bass and seemed to have a lower output.

This seemed to have recovered to match the other but then it sported this rather nasty crackling noise on bass heavy material (ie Bjork !) across all different volumes (but not that loud TBH). The only way I can describe it is that is like cleaning a stylus with a carbon brush with the volume on - that's what you hear in the music.

Now, I got these as a project with the idea of using them after restoring them cosmetically as that's about my skill limit. I don't have electronics skills and my soldering skills are very poor - but I can learn (?!?!).

My newbie/uneducated thoughts were blown driver/coils or dodgy component or capacitors in the XO. I have of course found replacement drivers and cross-overs on ebay/Falcon. But I see no point in jumping to conclusions just yet.

So, three questions for the experts :
1: What are the possible causes for this ?
2: Whats the logical sequence of checks that I can apply ?
3: What equipment would I need for 2 above ?

All answers and help very gratefully received from the man from Essex, UK
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Old 31st August 2015, 06:02 PM   #2
sreten is offline sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Hi,

Swap parts between the pair to ascertain the problem area.
Inverting old bass/mid units can often help.
Replace all electrolytics with similar.

rgds, sreten.
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Old 31st August 2015, 10:16 PM   #3
VaNarn is offline VaNarn  Australia
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Join Date: Dec 2010
Location: Ivanhoe
Help with troubled JR149 driver
Given the age of the speakers and the fact that small bass drivers work very hard I would inspect the flexible voice coil leads to the cone. Look for fraying or a clean break from a solder joint.
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Old 31st August 2015, 10:38 PM   #4
Chris Daly is offline Chris Daly  Australia
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Join Date: Sep 2004
Location: New Zealand
Hi
Check if another pair of speakers does the same thing, it could infer an amplifier fault
rather than speaker. I also have a pair of JR 149's, so know them pretty well.

There were two crossover models, early ones with components
mounted in a circle later on a rectangular board. Visually check
particularly the positive and negative terminals that connections
are tight, then crossover components, as it suggests there is a
bad solder joint. Next check the B110 connection terminals and
T27 terminals, hopefully just a loose wire.

Cheers / Chris
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Old 1st September 2015, 09:29 AM   #5
bbbiker800 is offline bbbiker800
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Join Date: Jul 2015
Many thanks guys for reading and helping with your suggestions. It all helps my education !

I will work thru these this week and will provide an update on how I got on.

A question for Chris Daly though before I start. To get to the drivers I have to remove the grill. That's stapled on and looks like its never been touched which means the drivers have never been removed. If I carefully remove the staples and prise the grill away then once finished would you know what the best method would be to re-affix the grill as I'll not be able to reuse the staples/holes and get the same solid fixing as have now ?

BTW:

The XO is the circular type (serial number 16256).

I first heard this problem with the JR149's using my normal amp which is a Musical Fidelity XA2. The fault is not heard using that amp and my normal speakers which are Dyaudio Audiance 52's. But, I have an Arcam Alpha 5 Amp (an old spare !) which I'm using to test them and the problem occurs with that amp on the same speaker. So I think that confirms its a specific speaker and not an amp problem.
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Old 13th September 2015, 08:04 PM   #6
bbbiker800 is offline bbbiker800
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Join Date: Jul 2015
Hi Guys .... finally got around to pulling the problem speakers grill off and inspecting the B110 driver and connections.

The +terminal wire came off after removing the driver so I'm suspecting it was fractured at the connector. And the -ve pulled off the terminal fairly easily. The flexible voice coil leads to the cone look sound at the terminal connection point and seem well anchored into the coil.

So to start, I intend to re-solder both wires to their terminal but i'm thinking that its best to use the same method. The question is though (remember i'm a novice and this is education !) how should I do that ? strip wires back and solder on a new connections ?

I found these on Falcon Acoustics - SINGLE-SIDED PCB TERMINAL PINS 1.3mm - are they right things ? they look like they would slide back onto the driver terminal after soldering the wire into them

But next I need a soldering iron to that job and i'll get that from Maplin unless anyone has a good suggestion on that. Ideally it'll be flexible for several other jobs.

The 2nd issue is cosmetic - its a combination of old glue that has been used to stick the foams on in the past and the foam has disintegrated and is caked on hard in spots and is to remove without out scratching but i'll find a way to do that (acetone maybe).

As always all education much appreciated.
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