Intriguing Circuit, LOOK

Hello there. I’m new to this forum and although I have a good deal of circuit building and design experience I cant quite understand this circuit! Maybe you can help me?

I purchased a second hand pair of tower speakers from a very nervous lady who told me she had never used them before. When I brought them home and hooked them up I realised why. Neither the Woofer or tweeter made a sound and the midranges sounded really wacky.

I decided to take a look inside the box, the wires were all connected and at first glance it all looked normal. So I started to eliminate all the possible problems, one at a time. I tested each speaker and its connections and they were fine. I then reluctantly pulled the crossover pcb out to take a look for shorts or anomalies, this is what I found:

Would someone take a look at the circuit and tell me if I’m wrong or was someone at the factory having a bad day!

If I get three separate punters to post a sensible reply, I will make a $5 donation towards running expenses for this site. Cheers and bye for now.
 

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Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
Welcome to the forum.

That's an odd one. The 2.2uF cap in series with the woofer isn't going to allow much bass. (none at all) :) The 33uF on the 2 mids could be a 1200Hz high pass. The little inductor on the tweeter might be to tame the top end.

The tweeters may be blown, thus no sound.
 
Risking the assumption that those component values are correct, the most likely error would have been for the 220uH inductor and the 2.2uF capacitor to have been mistakenly swapped in location. Transposing those two components will create a x-over having a 1st order low-pass to the woofer, a 1st order high-pass to the midrange, and a cascaded non-coincident 2nd order high-pass to the tweeter. The speaker will then function.

Whether the x-over was properly designed in the first place, or the speaker as a system sounds any good even if it were, well, you'll quickly find out. Please let us know what you discover.
 
Hello there Cal, I see you come from Canada wher my favourite pair of Sound Dynamic 100S were dutifully constructed.

I must say that you and I came up with the same idea - that the fellow on the production line just got the curly bit of enamelled wire mixed up with the little tin can.

I am probably wrong (usually) but I cant see how the tweeter could possibly have worked though, due to the location and size of the coil in the circuit.

The speakers are up and running now but they are only just a set of speakers. They sound like one of those cheap gheto-blasters.

The low and midrange drivers are actually glued together with wallboard adhesive and the magnets wobble as they oscillate. NO KIDDING! When I pulled the cabinet apart I found several broken wood screws, due to the fact that everything was rattling around so violently in there! ITS THE TRUTH I CANNOT LIE, and furthermore, all the internal bracing (10mm MDF)! was laying in the bottom of the box! It's like drivin a car with square wheels - not very harmonious at all. FAIR DINKUM, I'm just crackin' up as I type this because the speakers are unique. Meieta is there name.

Thankyou for your comments and it is nice to meet you as I have read a few of your threads before. Have a good week at work and hope to talk again. Sincerely, Phil Elliott
 
Hello Ken, nice to meet you. I like fishing too. Us Tasmanians smuggled a heap of trout from up where Cal lives and now they're all about four foot long because there's no angry bears down here to eat em, they're so big we use explosives to stun them and then we dive in and wrestle them to the bank - we finish 'em off with a sharp blow to the head! I find they are best cooked in a large pot as follows;
  • Bring 50 gallons of fresh water to the boil and find yourself a nicely rounded rock.
  • Place the fish and the rock into the boiling water.
  • Boil it all up until you can stick a skewer through the rock.
  • Discard the fish and eat the rock!
I guess I am a bit of an idiot Ken - but this is what happens to me when I stay up to late.

Ken, you are a very intuative individual, as indeed are some of the other members. You hit the nail right on the head regarding the nonquality of the [Meieta] speakers and if you get around to reading my previous thread you can hear me say that also. I am being truthful when I tell you that they used what appears to be wall-board adhesive to stick the magnets onto the baskets of the mids and low frequency speakers. How can this sort of thing happen?

Anyway, thanks for replying with helpful advice. Sincerely, Phil Elliott
 
Hi there Panamaniac, It is the first forum I have joined and the response has been teriffic! There are some real humans out there! In future I will try to keep the chit chat down a bit and simply drop in from time to time. I will also attempt to answer a few threads if they are within my my scope. I am going to donate on payday because I believe websites like this one are worth their weight in gold.

Electronic circuitry has a magical attraction to me because I have always seen my self as a bit of a dummy - but when someone brings me their $500 AV unit and I manage to isolate a problem that I can fix, it gives me a great sense of achievement to do so and then take it back to them with a big grin on my face. I say to myself; mmm "not bad for a Wood Machinist"! I guess it's a bit of an ego thing, but in a good way - because everyone wins.

BTW I love listening to Blues Music and strumming the Guitar. My latest DVD is a docco on the old blues legends and features young Kenny Wayne Shepard sitting in with a heap of blokes like Coodie Stark and BB King not to mention dozens of other great legends. It is entitled Ten Days Out. (please forgive the spelling)

Cheers mate, and I will drop in again soon. Sincerely, Phil Elliott