Hello everybody!
I recently acquired a pair of three way speaker (Technics SB-R3). They mostly sounded great (especially the tweeter that is very good and not too directional), but the sound seemed "bumpy" and mid-range lacking. Sure enough when I took the grid off I realised the medium speaker wasn't working, on both speakers!
I went through the following troubleshooting steps:
* Took out both medium speaker, measured their impedance. Both were around 6.5 ohms, with 8 ohms written on the back. My take of this is that they are working fine, the nominal impedance technics wrote is just a little off
* Took all of one speaker apart. Checked wiring, and crossover PCB which both seemed fine.
* Suspecting a failed capacitor, I took out all 4 capacitors from the crossover, the drift wasn't huge, except for one (80%) but I changed them all with film one.
The medium speaker still won't work!
So my question is: is there something I missed? How can both speaker have the same defect?
It's a mystery..
EDIT: I was mistaken and those speaker are in fact the SB-R2. Sorry for that
I recently acquired a pair of three way speaker (Technics SB-R3). They mostly sounded great (especially the tweeter that is very good and not too directional), but the sound seemed "bumpy" and mid-range lacking. Sure enough when I took the grid off I realised the medium speaker wasn't working, on both speakers!
I went through the following troubleshooting steps:
* Took out both medium speaker, measured their impedance. Both were around 6.5 ohms, with 8 ohms written on the back. My take of this is that they are working fine, the nominal impedance technics wrote is just a little off
* Took all of one speaker apart. Checked wiring, and crossover PCB which both seemed fine.
* Suspecting a failed capacitor, I took out all 4 capacitors from the crossover, the drift wasn't huge, except for one (80%) but I changed them all with film one.
The medium speaker still won't work!
So my question is: is there something I missed? How can both speaker have the same defect?
It's a mystery..
EDIT: I was mistaken and those speaker are in fact the SB-R2. Sorry for that
Last edited:
Are you sure there is zero output from the mid driver. You could perhaps disconnect the woofer and tweeter and see if any sound does in fact emanate from the mid.
An image search shows there appear to be what look like level pots for the mid and tweeter and also resetable 'protectors'. Something around here is the most likely cause of the problem. Check the continuity of these resettable protectors and also check the pots are OK.
An image search shows there appear to be what look like level pots for the mid and tweeter and also resetable 'protectors'. Something around here is the most likely cause of the problem. Check the continuity of these resettable protectors and also check the pots are OK.
Attachments
Thanks for the answer!
I indeed dit not disconnected both other speaker to test the mid one, but I tested it at a fairly loud volume, gently resting a finger on the membrane and could't feel a thing.
Regarding the panel, yes there is one but my version only has tweeter settings, and I disconnected it while recapping (the potentiometer was very noisy and sometimes disconnected the tweeter). It seemed I was mistaken on my notes and this is in fact the SB-R2. Sorry for the confusion, I'll try to edit the title accordingly
Regarding the over current protector, I can check but if I remember correctly, it was wired between the post and the crossover so my guess was that a failure would affect all three speakers..
But thanks for the suggesting, I'll make sure the mid are totally silent.
I indeed dit not disconnected both other speaker to test the mid one, but I tested it at a fairly loud volume, gently resting a finger on the membrane and could't feel a thing.
Regarding the panel, yes there is one but my version only has tweeter settings, and I disconnected it while recapping (the potentiometer was very noisy and sometimes disconnected the tweeter). It seemed I was mistaken on my notes and this is in fact the SB-R2. Sorry for the confusion, I'll try to edit the title accordingly
Regarding the over current protector, I can check but if I remember correctly, it was wired between the post and the crossover so my guess was that a failure would affect all three speakers..
But thanks for the suggesting, I'll make sure the mid are totally silent.
Last edited:
Hmmm
If you have altered the wiring then its possible a mistake has been made. Level pots like these are notorious for going intermittent... you might have to go back to basics and try and draw the wiring and crossover to determine how it all connects together. If you are removing a pot then you may also need to replace it with fixed resistors to approximate the normal or flat response setting.
You not feel much if any movement on the mid cone but it should certainly be audible with a full range signal.
If you have altered the wiring then its possible a mistake has been made. Level pots like these are notorious for going intermittent... you might have to go back to basics and try and draw the wiring and crossover to determine how it all connects together. If you are removing a pot then you may also need to replace it with fixed resistors to approximate the normal or flat response setting.
You not feel much if any movement on the mid cone but it should certainly be audible with a full range signal.
It looks like you will need two resistors to replace the pot in order to preserve the correct impedance (and cross over characteristics). The pot is almost certainly a linear type and so with it set at the midpoint you would need two equal value resistors, each one half the value of the pot and with the tweeter connected to the midpoint. The wattage needed will be relatively small and 3 watt components should easily cover it.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.