Blown speakers

Discussion in 'OT Technology' started by WS6Formula350, Jan 12, 2005.

  1. WS6Formula350

    WS6Formula350 molestache amririte?

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    I took the unit apart and the woofer was 7 ohms and the tweeter was 6 ohms.

    Is that why they blew up? The other two cabinets I have is marked as having an 8 ohm impedence on the back and the receiver says it's 8 ohms or bust. :dunno: Should I get an 8 ohm tweeter to go with the woofer I'm going to be putting in?
     
  2. P07r0457

    P07r0457 New Member

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    was this a pre-built unit? if so, what brand/model?

    depending on the crossovers used, 7/6ohm could be correct.
     
  3. WS6Formula350

    WS6Formula350 molestache amririte?

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    It was a "Realistic" speaker from Radio Shack. On the back it says the input is 8 ohms, 60W max. Model is Nova-15. It's a hand me down, and it blew out so I was looking at replacing the blown woofer with a Dayton component (8 ohms). I don't know shit about speakers-- would the higher impedence units work? I have no idea how to go about checking the crossovers or even what a crossover is.
     
  4. XR250rdr

    XR250rdr OT Supporter

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    Dayton 8 ohm will be fine.
     
  5. WS6Formula350

    WS6Formula350 molestache amririte?

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    Should I get an 8 ohm woofer and tweeter? Or will the 8 ohm woofer work fine with the 6 ohm tweeter that's already in the cabinet?
     
  6. 04

    04 Guest

    The difference between 6 and 8 ohms for nominal impedence is generally not much at all. In fact, the crossover point(s) wont change much with that small of a variation. So you should be fine with using any speaker that is between 6 and 10 ohms or so.

    The 7ohm or 6ohm figures are simply nominal (or average if you will) anyways, and with the crossover parts, the actual impedence of the speaker could be 8 ohms or higher.

    That said though, even though the speaker's total nominal impedence is only 8ohms, if you were to look at a chart showing frequency versus impedence, you would see that it varies QUITE a bit.

    It is very unlikely that the speakers blew because they were rated at 6 or 7 ohms.

    Is it possible that you could take a picture of the crossover on the speaker? It's usually a little circuit board with electrical components soldered to it.
     
  7. WS6Formula350

    WS6Formula350 molestache amririte?

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    Sure thing. I don't know if this is the crossover or not, but it's the only electronics in the cabinet. It looks like a small capcitor (especially since it's measured in micro farads :dunno: )-- markings: "50V 4.7 uF B1-POLAR." It's what all of the speaker lines are running to. Best pic I could get of it and some pictures of the cabinet:

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    That being said, I don't really care at this point why they blew out (the surround on the cone was made out of this really cheap ass foam is what I'm attributing it to) but I'd like to know if I can put some new components in it and have it all work properly. These are in my price range and seem to have a decent frequency response. They aren't audio phile quality by any means but I gurandamntee they're better parts than what I took out. I can also afford these. :hsugh: :o

    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-063
    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=270-034

    The receiver I'm working with delivers 100 watts per channel. I've also got a set of Marantz cabinets I got from my dad that are older than I am but they're still running strong and clear :coold:

    Thanks for the help.
     
  8. WS6Formula350

    WS6Formula350 molestache amririte?

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    Old and busted components to point and laugh at:

    [​IMG]
    [​IMG]
     
  9. 04

    04 Guest

    Well, those parts would certainly work better than the broken ones, but if you're gonna spend the money to fix those parts, I would also suggest doing a little bit more and buy some crossover components :o

    That single capacitor is not really a good crossover at all - it only provides a shallow filter for the tweeter, and does nothing for the woofer. I would suggest at the minimum to upgrade the tweeter filter to a 2nd order network (which would be a capacitor and an inductor), and I would also add an L-pad to adjust the volume of the tweeter in relation to the woofer. You can get good quality parts for less than 20 dollars a pair. And I would probably also get another inductor for the woofer too.

    I can tell you how to do all this, but let me know first if you just want to go ahead and buy those two components and hook them up.

    One problem I see with both that tweeter and woofer you picked out is that there is no frequency response graph. When a manufacturer specifies a frequency range of say "50hz to 4khz" with no other information, that really doesnt tell you anything. The woofer might actually go higher in frequency (but at attenuated levels), or it may have a huge peak in the frequency response. Without a graph, we can't tell. That's why I'd suggest picking a woofer that has already been measured by partsexpress, and that way you can better pick a match. Same thing with the tweeter.

    I do realize though that you are simply wanting to do an inexpensive upgrade, but I thought that maybe you might want to dig deeper into this :o If you just want it to work, the woofer and tweeter you picked out should work fine :)
     
  10. WS6Formula350

    WS6Formula350 molestache amririte?

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    I'd like to get more in depth but I don't have a soldering iron, experience soldering or the money to buy one unfortunately. I wish now I would've paid more attention in Physics when we were going over inductance, reactance and capacitance because it probably would help out here :o The text book is just over there haha.

    This other Pioneer woofer has been rated by them, though I don't really know what the graph means. This woofer supposedly goes to a higher frequency, giving some midrange performance to the cabinet maybe :dunno: I can't really afford to sink the cash into the tweeters that have been measured and benchmarked though, they get insanely pricey in any category other than dome tweeter.

    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-042

    What does a crossover do, exactly? The capacitor and inductor change the current, voltage and resistance through the circuit and I'm sure that obviously changes the overall impedence and resistance of the cabinet. I'm guessing changing the impedence and resistance of the circuit changes the power output of the speaker and that's how you'd modulate the tweeter volume vs. the woofer volume-- by simply increasing the resistance to the tweeter and therefore giving it less power, ergo less volume?
     
    Last edited: Jan 13, 2005
  11. WS6Formula350

    WS6Formula350 molestache amririte?

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  12. 04

    04 Guest

    They would probably work pretty well together, although the single capacitor you have now would not be adequate, and you would have to build a better crossover.
     
    Last edited by a moderator: Jan 14, 2005
  13. 04

    04 Guest


    A capacitor simply divides the frequencies to specific speakers. It can also modify the frequency response of the speaker (act as an equilizer) and do other things as well. Here's a good link for a basic tutorial: http://www.partsexpress.com/resources/capcoil.html

    As for the graph of the Pioneer woofer, a perfect speaker would have a straight line across the chart of frequency versus amplitude. For the most part, the closer the speaker is to being a close line over it's designated bandwith (the frequencies you intend for it to play) the better. But in the graph you see, there are dips and peaks in the line, which are undesireable for the most part. The thing to take into account though is minimising the dips and peaks so that the response of the total speaker system gets close to be a flat line as possible.
     
  14. WS6Formula350

    WS6Formula350 molestache amririte?

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    So what would I need to do to build a crossover adaquate to run that Pioneer woofer and tweeter efficently? Do I have to solder, or can I buy a prebuilt crossover? I'm browsing over that link now and I feel like I'm back in Physics II, it's giving me nightmare flashbacks :o
     
  15. 04

    04 Guest

    Well, it would take quite a bit of work, and soldering, yes :hs:

    You could also buy a prebuilt crossover, but they are kinda expensive.

    On one hand, you could just buy inexpensive replacement parts, and it would probably sound ok. On the other, you could probably get better sound than before, but you'd have to design a new crossover, and end up spending quite a bit of time and money :o

    Which one are you thinking about doing? :o
     
  16. WS6Formula350

    WS6Formula350 molestache amririte?

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    Okay here's the three things I've been looking at buying--

    One of two woofers:

    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-042
    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-480

    One of the cabinets is sitting next to the T.V. so I'm thinking the shielded one would be better. On the other hand, it was sitting next to the TV with the old parts and didn't affect it. The problem with the Dayton woofer is that it's 8.5" wide and I've only got 8 and 3/16" to play with in the mounting process. There's a quarter inch recessed ledge in the box that the woofer was mounted too and the Dayton is bigger than that. The Pioneer is closer to fitting. I suppose I could also drill new holes in the cabinet since the magnet isn't wider than the cutout in the box, however.

    And probably this tweeter because I can't afford much else. I've got mounting clearance issues with most of their other tweeters too-- they claim this one is in a lot of stuff and it also fits the budget nicely :o

    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=270-034

    They have cheap(er) prebuilt crossovers on their site for either 3000hz or 5000hz, I haven't really reached a grasp on understanding exactly what that means though. I think though, since it's a "2-way" crossover and it only has the high end pass, that it limits the tweeter to sounds above the crossover point (correct me if I'm wrong). That Pioneer woofer strays into the tweeters frequency range-- but it seems like it's in mid-range land and that it would just give me more sound reproduction.

    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-174

    Also, in looking at my cabinet, the capacitor that's built into it is integrated into the wire input on the back, so I'm not exactly sure on how to install a different crossover in the first place. Additionally, the speaker input is round (whereas all the prebuilt crossovers are 5x7" rectangular), and none of the replacement terminals they sell on parts express matches the hole in the back.

    [​IMG]
    [​IMG]

    It looks like my most likely purchase is going to be the Pioneer woofer and that cheap Pioneer tweeter. It may not sound the best without the crossover, but it'll also almost have to sound better than they did before :o

    Summed together the woofer is 80 watts and the tweeter is 40 watts, but the receiver will only drive 100 watts per channel-- does that just mean I'm not gonig to get full power out of the speaker, or is a 20 watt overage really that bad? Or is overall power even calculated like that in this case?
     
  17. WS6Formula350

    WS6Formula350 molestache amririte?

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    Btw, thanks for all the input, it's been a learning experience :coold:
     
  18. XR250rdr

    XR250rdr OT Supporter

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    I think really for that much money you can find a new set of speakers that will sound just as good or better than those speakers did new. Watch for speakers on clearance. I've picked up a couple pairs of bookshelf speakers for $50.

    http://www.bestbuy.com/site/olspage.jsp?id=1051826208041&skuId=5376167&productCategoryId=cat03044&type=product <--- A friend of mine has a pair of these and they arent bad. Good bass output. Sometimes they go on sale even cheaper than this. I believe he paid $50 for the pair.

    If I can find something else I'll update my post.

    FYI...Power ratings arent determined by summing the power handling of the individual drivers. A speaker that has a 80W max woofer and a 40W max tweeter would only be able to really handle 40W of power across the entire audible spectrum. Often you can have a higher powered receiver because in reality the tweeter doesnt dissipate as much power as the woofer.Power ratings arent determined by summing the power handling of the individual drivers. A speaker that has a 80W max woofer and a 40W max tweeter would only be able to really handle 40W of power across the entire audible spectrum. Often you can have a higher powered receiver because in reality the tweeter doesnt dissipate as much power as the woofer.
     
  19. P07r0457

    P07r0457 New Member

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    I have those same KLH speakers. I got em for $49.99+tax (back in cali) about 5 years ago. Great speakers for the money.
     
  20. WS6Formula350

    WS6Formula350 molestache amririte?

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    I picked up a pair of Pioneer 3-way 160 watters, but I'm hanging on to the old speaker cabinets I still have so I can dabble in speaker building later when I have more time and money. Thanks for all the advice guys.

    The Pioneer's are pretty clear and tight sounding too, pretty good buy for $100 I think.
     
  21. 04

    04 Guest

    Well, if you want a couple of websites for in the meantime to read to learn a bit more, lemme know :o

    I'm glad you like the new speakers though :bigthumb:
     
  22. WS6Formula350

    WS6Formula350 molestache amririte?

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    Sounds awesome, I'd appreciate the links :cool:
     
  23. 04

    04 Guest

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