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-   -   Fixing An DAP Audio Festival Speaker? (http://www.diyaudio.com/forums/pa-systems/236104-fixing-dap-audio-festival-speaker.html)

DogOnASpeaker 16th May 2013 09:00 PM

Fixing An DAP Audio Festival Speaker?
 
Hi DiyAudio People! My name is Moon, and as sure as i am a doggie on a speaker is this Posted in the wrong section. I'd bet! (: I suck at forums. x)
Ah well! Let me get this to a Point, i recently Bought a Sony STR-DE545 Reciever, A Sony S.A.W Active sub and four Sattelites of a friend for A tiny 20Dollar. (Proud Proud!) I hooked it all up, when i one day at school (where I'm famous for being handy and loving to fix stuff) Was given a DAP Audio Speaker set. two Big "Kind of" Festival, Live performance speakers. I thought those things could go well with my new setup at home, if i could fix them. i took them home and well, the 120w Bass Speaker (subwoofer?) Plays beautifully well. smooth and nice. But the Two horns said like, Nothing? so i only got hard Lined bass from those. Then when i took them apart for closer research, i first found the Piezo's to be "dead." as in stepped on Muffin. (no good Taste!) I then when taking a closer look behind the Woofer where the cables go in, discovered a PCB, With a Yellow (capacitor?) and a Coil, and two other components, on both speakers this though Shows Remarkable big *Fire!* damage! the PCB boards actually took so much fire damage on the one speaker that the board itself had began to bubble? I got a picture right here for you : https://www.dropbox.com/s/jrhspx8xgn...516_223157.jpg
I believe this board is what manages the input, for the Woofer to get its 120w and the Piezo's their 5w or so, Right? Can this board be replaced? Or can i simply Re-solder it with The right parts? And why did this Happen in the first place? Questions Questions, Curious doggies. Somebody tell me?

-Moon

indianajo 18th May 2013 04:34 PM

Uh, yeah, crossovers can be replaced but not usually from the manufacturer. Your location is "in a basket" so I don't know if digikey.com has a warehouse there. If you were in the US I would tell you to buy a crossover board from them. Something like a 2khz inflection point or something. mcmelectronics.com in OH has a few, too. Make sure any crossover assembly you buy has at least a 120 W rating, higher would be better. This crossover has two active elements, an inductor and a capacitor, so it is probably a 12 db/octave one. A 10 v clamp (MOS overvoltage supressor) across the tweeter would be a good aftermarket accessory.
Your capacitor looks good, unusually, but it is 475 value and probably plastic film, which is pretty long lived stuff. The inductor looks suspicious with burns behind it, the 20 W resistor should be measured versus what ever it says (I can't read the value), and the paper board has to go, it is all carbon. There may be something missing, a overvoltage protector possibly, vaporized by somebody's high wattage PA amp, or by amp transistor failure.
If you're somewhere that you can't buy crossovers, you could probably unwind the inductor, repaint the wire with urethane floor varnish, and then wind it up again around a round eraser or a wood dowel. The board I would replace with NEMA LE or CE laminate, but that is also a US sourced part. Most people live in countries supported by farnell.com warehouses, but they don't sell speaker crossovers or LE laminate either. Who knows what you can buy in basket.

JMFahey 18th May 2013 06:26 PM

Quote:

Who knows what you can buy in basket.
Eggs/apples/oranges/onions/nuts/ ..... /etc.

If you want to buy a baby Moses, I guess the Special Sale was finished .... huh .... some 4000 years ago.

And unless you live within 3 months on a camel away from the Nile River and can pickup by yourself, freight cost will really hurt.

Now, ..... speaker parts? .... I doubt it ;)

chrispenycate 20th May 2013 02:00 PM

Here goes.
Two components would normally be a 6dB/octave crossover with the inductor (coil) in series with the bass unit and the capacitor (yellow thing) with the HF. However, this is a piezo tweeter which is sort of self crossing over (as it's a purely capacitive load, just about, it doesn't take any current at low frequencies). So that could be just a low pass filter on the bass driver, inductor in series, capacitor across it, and the resistors stepping down the rather nasty tweeter.

Now, it looks to me as if the resistors have been cooking, while the inductor is fine. This is supported by the fact the bass diver is still functioning. Good; getting power resistors is a whole lot easier than specific value inductors. I suspect the amplifier driving them went into radio frequency oscillation, as that much high frequency audio would have been extremely unpleasant.

Before ordering up new components, take your multimeter and put it across the terminals of the piezo tweeter (disconnecting it from the crossover first, no need to complicate matters). It shouldn't read a resistance but it should make a click (actually, if your multimeter is digital, put a battery across the terminals, but only because it's a piezo). You could also connect the tweeter across a headphone output, to see if you can hear music from it. If it doesn't click, you're going to need a new tweeter, and now is the moment when you have to decide whether to get a new piezo or something that sounds decent.

I would normally expect the tweeter to burn out under these conditions, but seeing that the 8.2 ohm 20 watt resistor seems to have cracked from the heat and it would presumably only have been taking enough current to do that if the tweeter were still working, so perhaps the nasty little b has survived. In which case, you only need to replace the resistors. Two each of 8.2 ohms 20 watt and 4.7 ohms 5 watt (I don't think it's worth getting higher power ratings; I'm convinced the amp was faulty). Take the crossover board off, and follow the circuit; if it seems the resistors are in series with the tweeter, and the other components associated with the bass driver, we're fine. If not, take a picture of the other side of the board and post it (nice trick with the drop box, by the way; how to you find its URL?).

Now, we're not even going to replace the board. If, as I suspect, the big resistor is in series with the tweeter and the smaller one in parallel to ground we'll need three brass screws screwed partially into the particle board of the cabinet, spaced for the big and little resistors (it was easier when they were hollow and you could just put the screw down the middle), spaced for the resistors. then we find something heat proof to put between the resistors and the cabinet (but they don't normally run too hot; the fact they used a nylon cable tie indicates this.) a piece of metal would be fine, as long as it doesn't short to the screws) Wind the resistor legs round the screws, move the wires from the board to the equivalent point on the bodged circuit, stick the resistor to the plate and the plate to the cabinet with high temperature adhesive, and solder all the joints carefully;it's going to need a lot of heat.

If you choose to put a decent tweeter in, come back and we'll look into getting a full crossover.

Hmm, dollars for the surround system? Probably stateside, maybe Australia or Hong Kong…

DogOnASpeaker 20th May 2013 03:43 PM

Quote:

Originally Posted by chrispenycate (Post 3497841)
Here goes.
Two components would normally be a 6dB/octave crossover with the inductor (coil) in series with the bass unit and the capacitor (yellow thing) with the HF. However, this is a piezo tweeter which is sort of self crossing over (as it's a purely capacitive load, just about, it doesn't take any current at low frequencies). So that could be just a low pass filter on the bass driver, inductor in series, capacitor across it, and the resistors stepping down the rather nasty tweeter.

Now, it looks to me as if the resistors have been cooking, while the inductor is fine. This is supported by the fact the bass diver is still functioning. Good; getting power resistors is a whole lot easier than specific value inductors. I suspect the amplifier driving them went into radio frequency oscillation, as that much high frequency audio would have been extremely unpleasant.

Before ordering up new components, take your multimeter and put it across the terminals of the piezo tweeter (disconnecting it from the crossover first, no need to complicate matters). It shouldn't read a resistance but it should make a click (actually, if your multimeter is digital, put a battery across the terminals, but only because it's a piezo). You could also connect the tweeter across a headphone output, to see if you can hear music from it. If it doesn't click, you're going to need a new tweeter, and now is the moment when you have to decide whether to get a new piezo or something that sounds decent.

I would normally expect the tweeter to burn out under these conditions, but seeing that the 8.2 ohm 20 watt resistor seems to have cracked from the heat and it would presumably only have been taking enough current to do that if the tweeter were still working, so perhaps the nasty little b has survived. In which case, you only need to replace the resistors. Two each of 8.2 ohms 20 watt and 4.7 ohms 5 watt (I don't think it's worth getting higher power ratings; I'm convinced the amp was faulty). Take the crossover board off, and follow the circuit; if it seems the resistors are in series with the tweeter, and the other components associated with the bass driver, we're fine. If not, take a picture of the other side of the board and post it (nice trick with the drop box, by the way; how to you find its URL?).

Now, we're not even going to replace the board. If, as I suspect, the big resistor is in series with the tweeter and the smaller one in parallel to ground we'll need three brass screws screwed partially into the particle board of the cabinet, spaced for the big and little resistors (it was easier when they were hollow and you could just put the screw down the middle), spaced for the resistors. then we find something heat proof to put between the resistors and the cabinet (but they don't normally run too hot; the fact they used a nylon cable tie indicates this.) a piece of metal would be fine, as long as it doesn't short to the screws) Wind the resistor legs round the screws, move the wires from the board to the equivalent point on the bodged circuit, stick the resistor to the plate and the plate to the cabinet with high temperature adhesive, and solder all the joints carefully;it's going to need a lot of heat.

If you choose to put a decent tweeter in, come back and we'll look into getting a full crossover.

Hmm, dollars for the surround system? Probably stateside, maybe Australia or Hong Kong…

Wowow! You guys are advanced! haha. I'll read into this and see what i can do. Maybe i'll be able to find a board close to me, now where i know what they're named. I live in Denmark By the way. I just didn't know it was necessary. i'll add it in a minute. About the dropbox thing, after uploading things theres a little link icon on the element as you hover your mouse over it, clicking that will give you the ability to share Public links. (:
I'll take a look at if i can find a proper Board for this, and report back on what i find. Thanks for all the Help People!

DogOnASpeaker 20th May 2013 03:59 PM

Quote:

Originally Posted by chrispenycate (Post 3497841)
Here goes.
Two components would normally be a 6dB/octave crossover with the inductor (coil) in series with the bass unit and the capacitor (yellow thing) with the HF. However, this is a piezo tweeter which is sort of self crossing over (as it's a purely capacitive load, just about, it doesn't take any current at low frequencies). So that could be just a low pass filter on the bass driver, inductor in series, capacitor across it, and the resistors stepping down the rather nasty tweeter.

Now, it looks to me as if the resistors have been cooking, while the inductor is fine. This is supported by the fact the bass diver is still functioning. Good; getting power resistors is a whole lot easier than specific value inductors. I suspect the amplifier driving them went into radio frequency oscillation, as that much high frequency audio would have been extremely unpleasant.

Before ordering up new components, take your multimeter and put it across the terminals of the piezo tweeter (disconnecting it from the crossover first, no need to complicate matters). It shouldn't read a resistance but it should make a click (actually, if your multimeter is digital, put a battery across the terminals, but only because it's a piezo). You could also connect the tweeter across a headphone output, to see if you can hear music from it. If it doesn't click, you're going to need a new tweeter, and now is the moment when you have to decide whether to get a new piezo or something that sounds decent.

I would normally expect the tweeter to burn out under these conditions, but seeing that the 8.2 ohm 20 watt resistor seems to have cracked from the heat and it would presumably only have been taking enough current to do that if the tweeter were still working, so perhaps the nasty little b has survived. In which case, you only need to replace the resistors. Two each of 8.2 ohms 20 watt and 4.7 ohms 5 watt (I don't think it's worth getting higher power ratings; I'm convinced the amp was faulty). Take the crossover board off, and follow the circuit; if it seems the resistors are in series with the tweeter, and the other components associated with the bass driver, we're fine. If not, take a picture of the other side of the board and post it (nice trick with the drop box, by the way; how to you find its URL?).

Now, we're not even going to replace the board. If, as I suspect, the big resistor is in series with the tweeter and the smaller one in parallel to ground we'll need three brass screws screwed partially into the particle board of the cabinet, spaced for the big and little resistors (it was easier when they were hollow and you could just put the screw down the middle), spaced for the resistors. then we find something heat proof to put between the resistors and the cabinet (but they don't normally run too hot; the fact they used a nylon cable tie indicates this.) a piece of metal would be fine, as long as it doesn't short to the screws) Wind the resistor legs round the screws, move the wires from the board to the equivalent point on the bodged circuit, stick the resistor to the plate and the plate to the cabinet with high temperature adhesive, and solder all the joints carefully;it's going to need a lot of heat.

If you choose to put a decent tweeter in, come back and we'll look into getting a full crossover.

Hmm, dollars for the surround system? Probably stateside, maybe Australia or Hong Kong…

Wow, Reliable Forum client, didn't send my reply twice? I'm sorry About that.

I don't know as much about these audio things but now where i know what I'm looking for its much easier. I love in Denmark By the way. I'm Sorry for not listing that. I'll see if i can get that replacement part i need here, or i fix myself on Up by ordering the components online and a Matching PCB.

And about the dropbox thing, when you upload an Element you highlight it, seeing an little "Link" icon to the right side of the blue selection. Clicking it gives you an Share with public link. But yes. as Said, ill look into fixing this and report back, thanks for the help people!

-Moon

DogOnASpeaker 25th May 2013 02:17 PM

Done~
 
I bought an amplifier board off dx.com made a box and connected the speaker to the Subwoofer output, put two sonos Outputs on the rear of my box and it all works flawlessly. its not as Beautiful quality as it was originally but it works. so i like made myself an "kind of" Active Subwoofer out of it instead of fixing it. Problem solved, is the original Speaker box worth keeping guys?

indianajo 25th May 2013 05:31 PM

Every component of a properly designed speaker package is important, even the cardboard, holes, and bits of fluff stuffed in the odd corners. Those details smooth out the sound, can give a +- 3 db flat frequency response on a well designed speaker. Any other random collection of parts may cover the same frequency range, but not be as smooth. Peaks and valleys in the frequency curve cause distortions. Glad you like what you came up with. You won't be able to buy exact replacement anything IMHO for an minority brand speaker like this, so don't worry about the keeping the old boxes.


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