Intriguing Circuit, LOOK

[farmerjack61]

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.

[Pano]

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.

[Cal Weldon]

Looks like they just swapped the 2.2ufd and the 220 uH. Whoops, like Pano says, the tweeter with just a 33 on it might not last too long.

[Ken Newton]

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.

[farmerjack61]

Nice to hear from you SIR. Are you Panamaniac because you come from Panama or cause you're mentally disturbed? Just kidding cobber! Don't ban me from this site or I'll have no one to talk to!

[farmerjack61]

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

[Cal Weldon]

Originally Posted by farmerjack61

that the fellow on the production line

Are we sure that's a fellow?

Originally Posted by farmerjack61

They sound like one of those cheap gheto-blasters.

Methinking white van. One without shock absorbers to boot. Sad really.

[farmerjack61]

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

[farmerjack61]

Yep I've got a set of those white van speakers too but after tossing the x-overs, building a new enclosure and adding a midrange they sound like a heavenly choir compared to these ones! Still not my favourite speakers though. I'm going to spend some time over the next couple of weeks to check out your gear, so I'll keep in touch.

[Pano]

Hmmm. Yeah that makes sense. Swap the 2.2uF and the inductor. Maybe the small inductor was meant for a slight flattening or roll-off on the woofer. Almost like running it sans crossover. The 2.2uF would be better for the tweet.

Worth a try!