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Dennis Murphy Pioneer SP-BS22-LR DIY Modifications

I realize no one has posted on this thread for 2 years now, but I just picked up a NIB set of BS22s on an auction for $38. I originally planned to wire them up as second speakers to go with my BS41s. After listening I decided the BS22s were even better than the BS41s and then I stumbled across this thread. All parts are now on order, hopefully financed by selling my BS41s. Thank you to whoever managed to keep all those images alive, the internet really can be an incredible place.

Hal
 
I scored my modified ones on Craigslist for $60 and have kept them for 3 years. Best deal ever. Bought another pair (bone stock) for $40 and gave them to a co-worker to use in his stereo system. Right now I’m playing around w some Boston acoustics cr-6’s and they are pretty sweet. I like them a little better for movie playback at the moment. Have fun modding.
 
I think whoever assembled my speakers had stock in the glue company. Both sides of the circuit boards are completely covered in glue. The only way to even get anything loose is to melt it with the junker soldering iron, suck it up with the solder sucker and then slowly carve the components off. So I appear in this process to have munged it up and managed to remove the silvering on the old PCB where the lead from L2 comes through and connects the old and new boards together. Can I just bridge this lead to somewhere else?

2bvhXHWX

 

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These remain my favorite bookshelf speakers. I also did the Dennis Murphy mods for the BR-1, the AA+ for about $400 in cost, but I believe these surpass them. They just seem to sound "right" for vocals and acoustic instruments. And for so cheap! I do use a sub to fill in the low end. These are one of the great deals in audio and with the added satisfaction of DIY.
 
Somehow I managed to make these work, even if my craftsmanship and skill at soldering is quite rudimentary. I do like the improvement, though it does seem like they need to be driven a little more to achieve the same volume. Overall they do seem to project more into space even if the volume is higher and they are absolutely clean and crisp. The top is a little more restrained and the bottom end seems to show better crescendo and diminuendo. As I'm writing this I'm listening to Sam Cooke's "A'int That Good News" and Sam's voice projects out more and the orchestration is clearer while also being less in the front even on my meagre setup.

All in all a fun and successful covid project.

H
 
Two hiccups in my mod !!! I have the two 2.2uf caps , C2 and C3 , swapped in my crossover builds . Don't think it matters , both ploy caps ? Had trouble finding the Vifa /peerless tweeters . Seems the peerless is only one I could find and paid $26 each . sure did like Parts express price of $15 better , but has been out of stock forever ^$%#$!
 
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Twintour said:
Two hiccups in my mod !!! I have the two 2.2uf caps , C2 and C3 , swapped in my crossover builds . Don't think it matters , both ploy caps ? Had trouble finding the Vifa /peerless tweeters . Seems the peerless is only one I could find and paid $26 each . sure did like Parts express price of $15 better , but has been out of stock forever ^$%#$!
Click to expand...

Concerning the two 2.2uF caps. C3 is in series with the tweeter and C2 is a shunt cap. Ideally, you'd want the higher quality cap at the C3 position. However, if the quality of the caps is similar, you likely won't hear any audible difference.
 
Thanks for the input . It will drive me nuts , I just replace the stock one with a new 2.2uF cap . Since I will have time........waiting to receive the one and only pair of tweeter I could find in the US.
 
GR Research had a look at these and he seemed happy with them at their MSRP of $200. He noted the effect that the grill has on the tweeter response and it's pretty obvious on the graph of frequency response. I'm interested to see if he releases kit for it and how it would compare to these modifications.

YouTube link
 
I have a maybe stupid question. Is there a way to tell if my tweeter on the left channel is not working? The tweeters do not vibrate in the same way the woofers do and even with my ear jammed up to the speaker I just cant tell if its not working or if I'm psyching myself out. Would it be obvious?

H
 
I think I'm just in my head. Maybe its just that some of the tracks on Rumors don't push as many highs through the left channel. I'm going to do some more experimentation. I fee like Pet Sounds would be a good trial.
h
 
Try swapping speakers between channels.
If the lack of highs follows the speaker, you know your issue is there.
If not it's not the speakers.
If you find you do have an issue,
Carefully check connections.
I never tried playing with these ( I bought a pair for my son years ago when they were on sale).
I also read the mod thread. It did seem some stuff was snug.
Maybe in reassembling something came loose. It happens.
 
Well its definitely not working. I have the whole crossover and speakers out of the cabinet and can confirm its not putting out a tweeter channel. I guess its backtrack and see where I went wrong.

I'm getting sound through the bass channel but the tweeter channel is not working. I had some issues with the original board where L2 connects to the In+ on the original board. I just bridged it to the lead of the large black thing that looks like a AA battery covered in tape (sorry, don't know what this is).

Otherwise everything looks correct.

H
 
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Sounds like an open
Cracked pcb, cold solder joint, broken lead ( less likely)
You know it's the high section.
Go point to point with a meter.
If you feel up to it. Open working one and measure same connection points. Where they read differently is your problem. Likely help you narrow down. Don't overlook the obvious.
Careful visual inspection with light and magnification might turn up problem.
My best guess is iffy connection on breadboard
.
 
nj pheonix said:
Sounds like an open
Cracked pcb, cold solder joint, broken lead ( less likely)
You know it's the high section.
Go point to point with a meter.
If you feel up to it. Open working one and measure same connection points. Where they read differently is your problem. Likely help you narrow down. Don't overlook the obvious.
Careful visual inspection with light and magnification might turn up problem.
My best guess is iffy connection on breadboard
.
Click to expand...

I don't disagree with any of this but I'm working more from a theoretical understanding than a practical working understanding.

Can I assume that if I am getting sound out of the bass channel that the original PCB is functional?

If so then I need to confirm that I have continuity on L2 between the original PCB and the new board and also on the ground between the two boards.

Assuming those work then I should have continuity from L2 to the positive lead for the tweeter correct? Is there a resistance value I should be measuring or is continuity good enough? The basics of making sure that the + and - channels are separated and that I have not somewhere grounded the new board is pretty straightforward, but beyond that is where I get a little lost.

Any advice? I'll print out the circuit diagram and make sure that I am tracing though the PCB correctly and that I don't have something dumb like the L2 grounding on the new PCB.

If not there is a pair of Kef Cresta 2 for sale locally for $50 that look interesting.

Hal
 
Without looking at schematic.
You know you have to have physical connections between points.
You can test continuity between those points.
What I was alluding to before.
You have a working example.
You can test the portions on the working speaker ( now a known value) and test against non working speaker.
Where are you?
( rough location) maybe someone here local can help you. It's likely a simple fix
 
I am headed out of town for a few days but I'll give this a run through on Thursday or Friday and report back. Comparing the two speakers is very good (and obvious) advice.

I'm in Seattle fwiw.

Hopefully full sound is in my future.
 
So I started just tracing out the continuity in the suspect crossover and pretty quickly identified the problem, two bad solder joints on one of the caps. Not sure if I just put it in the board and then never soldered it or just really did a crap job. It ended up being a quick fix, but it helped to walk away for a few days and let things pickle in my brain with some wine what not.

Now that its back together its pretty obvious how much better it sounds but I swear switching to the Lab 400 TT that I just got really made the floor so much more quiet and made the absence of the tweeter much more obvious.

Thanks for the patient support! Next step is a new stylus and then maybe experiment with phono preamps.

H
 
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