# Network/Impedance/Power Rating Q :o

Discussion in 'OT Technology' started by Mister Mac', Dec 31, 2002.

1. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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OK, everyone knows (I hope) that the total impedance of the arrangement below is 4 ohms. What I'm having trouble with is the total power rating. According to my calculations it's 300W, but that doesn't sound right for some reason

Anyone know?

Thanks

2. ### 04Guest

Power handling is 300 watts. You quadruple the number of voice coils dissapating heat, therefore the thermal handling is quadrupled.

You might be confused because your wiring in series would raise the system impedence, thus requiring more output voltage by the amplifier to get the same output. Which is true. But, while the voltage needed to get that 300w into 4ohms (as opposed to 1ohm if they were all wired in parallel) is higher, your power handling is still the same.

Power ratings are usually very confusing anyways. Usually it is rated thermally, but for how long? And at what frequency/enclosure? And at what type of signal?

3. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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Thanks!
I knew it had to be 300, why I got confused Probably because I haven't worked with this kind of circuit before.

Just after I posted the Q I worked out the voltages and found basically what you said. Thanks for the confirmation!

4. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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I tested this setup on the weekend. Running ~100W RMS total (because my amp couldn't get enough power from my old battery ) it could be heard 100yds away with the car doors shut

BTW the subs are 8" Avalanches Cost me \$30USD for ALL FOUR The scary thing is, they sound better than my 15" Better SQ, SPL and power handling

4x8" in 2.0 cu.ft (\$200 total) > 15" in 2.8 cu.ft (\$610 total)

5. ### 04Guest

Well, that isnt that surprising. I am surprised they can all fit in .5cuft each and sound pretty good, that is cool. How much louder are they than the 15"? They have similar cone areas... I would almost gurantee that the 4 8" could handle more power though, I mean 4 voice coils are a lot of heat disapating area. Same thing with partsexpress 22 dollar 10" woofers. People on this board would laugh at them, but they would outperform speakers at 3x the cost....

Probably same thing happened with your avalance 8"

6. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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I wasn't really surprised, but I wasn't very happy Maybe I'll have to sell my 15 and keep the 8s instead of the other way around

They sound A LOT better than I thought they would. I've got an old pair of 10" Tornados (same manufacturer) and they were good for the price, but nothing really special. The cones were too flexible to give good SQ However, because the 8"s are that much smaller, they sound a lot better My 15 should sound better than the 8s, but the box size/tuning is completely wrong

I haven't done a direct SPL comparison yet, but I'll be doing one possibly tomorrow or on the w/e. My 15" is 250W RMS, the 8s are 300W total. (but I doubt they'd handle that much)

This was never meant to be a serious project, I only bought the 8s because they were even cheaper than usual I was going to make a computer sub system with dual Isobaric chambers and a central bandpass port, but I decided to make a plain box (cheaper, quicker and much easier ) I wanted to sell the completed box, but now I'm not so sure

7. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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I don't usually buy cheap stuff, but like you said, the performance can be good. The only problem I noticed is, all 4 subs have coil impedance of 3.34 ohms exactly, but ONE of them only moves half as far as the others at high volume. That could be because of the shared airspace, but it's probably the sub itself

If it wasn't so hard to find cheap subs, (because they're so popular around here ) and if I had enough money and an old car, I would make a box with like 9 or 16 8s or 10s just to see how loud they could go

tempowazaman (OT member who doesn't post) wants 4x cheap 15"s for his car. I've designed the box/amp setup and it should cost around \$700 USD total (battery, amp, box, subs, cables)

Last edited: Jan 7, 2003
8. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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A few pics of the box... Screencaps, actually...

9. ### 04Guest

That looks pretty nice. Whats funny is the first car subwoofer box I built was almost the exact same color. Ill take a picture of it today.

10. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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Thanks This was my fourth box, so I'm getting better at building them

The colour was supposed to be similar to the speaker cone colour, but something went wrong I added too much black tint to the red paint and it ended up being mission brown I had to work on it for a while to make it lighter It didn't turn out exactly the colour I wanted, but it's close enough!

11. ### Mister Mac'Av: Daniela Denby-Ashe in Torchwood S1Ep7

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One of the 8s is no longer with us I turned it up a little too high and one was obviously weaker than the other 3 and got nicely toasted It was pure overpowering, no amp distortion involved. In a way I'm happy, because now I know my amp is working properly and producing full power

So on Friday I'll be down at BCS for a new sub

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