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Always wondered

 

Gold Member
Username: Araknid

BOCA , FL U.S.

Post Number: 1367
Registered: Nov-04
I always wondered if you can wire a resistor in series with the sub to change the final impendance.

Like say you wanted a 4 ohm load but you had dual 1.5 coils. So you wire in series then add a 1 ohm resistor in the circuit for a 4 ohm load? is that a good idea or not? I dont see why it wont work.
 

Silver Member
Username: Robert_d

MIA, FL USA

Post Number: 439
Registered: Sep-05
good though ... i dont know the answer but i think watts would have an effect like you would have to get a certain size resistor to withstand the constant heat
 

Gold Member
Username: Araknid

BOCA , FL U.S.

Post Number: 1373
Registered: Nov-04
Im almost 100% positive it can withstand the constant heat. Resistors do it all day long.
In almost every appliance.
 

Silver Member
Username: Mixneffect

Orangevale, Ca. USA

Post Number: 661
Registered: Apr-05
Why dont you try it, and let us know the results?
 

Gold Member
Username: James1115

Wilton, Ct

Post Number: 4346
Registered: Dec-04
that is a question for glass! Jonathan might know the answer also.
 

Silver Member
Username: Baseball1187

Columbia, SC

Post Number: 335
Registered: Dec-04
that is a HUGE amount of power being transfered directly into heat energy. I don't think a typical resistor can do it. Plus, if it was that easy, it would be quite useful and people would do it!
 

Gold Member
Username: Insearchofbass

Post Number: 3904
Registered: Jun-04
im thinking you could raise the impedance bassmanmike I raised the question could you go the other way I think the answer is yes with mods even in my question....no ofense baseball but just because no ones doing it doesnt mean it cant be done remember someone has to be first....the solution lies in solving the problems preventing you from doing something one at a time then you become closer to the final solution....remember thomas edison he failed many times with scoffers around him but ultimately succeded
 

Gold Member
Username: Insearchofbass

Post Number: 3905
Registered: Jun-04
Im no longer a I CAN'T person and I consider NO idea is a stupid one...not that im saying anyone is saying the idea is stupid......just a piece of scrpiture to consider "All things are possible with God." thats Truth people.. The final reality Praise God!
 

Gold Member
Username: Carguy

Post Number: 5065
Registered: Nov-04
It can be done. The problem is, you won't find a resistor that can handle the power. If you look at 80w resistor, it is quite thick and expensive. Not very practical. You'd be better off getting an amp that meets your requirement (probably cheaper too).
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 5064
Registered: May-04
It would take more than the average resistor to handle the power from a subwoofer. If you had a nominal 3 ohm load (speaker) and a 1 ohm resistor, with a voltage output of 40V, it will equal 400watts. 40V divided by 4 ohms is going to give a 10A current draw. The resistor will drop 10V, have 10A, and total power would be 100W. Not a typical resistor, but one with a heat sink could take it. That's assuming your amp is putting out 400W, though. Of course, with a dual 1.5 ohm load you're usually talking about a 13W7, and 1000W is going to take one heck of a resistor. Another problem is that if you add a series resistor, it will cut your damping down. Not really by a lot with a 1 ohm resistor, but it will cut it down since the speaker sees the resistor as source impedance.
 

Gold Member
Username: Insearchofbass

Post Number: 3906
Registered: Jun-04
"Not a typical resistor, but one with a heat sink could take it."

I like that idea
 

Silver Member
Username: Baseball1187

Columbia, SC

Post Number: 336
Registered: Dec-04
sean - if it could be done that easily, it would be. Impedance loads are the most typical problem with people matching subs/amps. If you could just pop a resistor in and solve your problem it would be the most common fix in car audio. It's not a novel idea. Plus, it will completely mess things up, like Jonathan said, if you start getting resistors in the circuit with different impedances.

Isaac is right, of course it can be done, physics tells you that. A speaker is simply a resistor. At school we were frying the little radioshack resistors in the labs using 4v and 2amps. Yea 8w. And they got extremely hot. Think about 1000w.
 

Gold Member
Username: Insearchofbass

Post Number: 3908
Registered: Jun-04
well baseball I never it was easy in terms of getting your mind around it but what you missed in jonathans example is "the inventive factor" hence the heatsink idea for one. Saying you cant and accepting it simply stops any POSSIBLE forward progress all im saying is dont say you cant say I dont know how you could achieve your goal

Thanks,

Sean
 

Gold Member
Username: Carguy

Post Number: 5070
Registered: Nov-04
Whoa, look at that, I finally beat Jonathan's post count.
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 5065
Registered: May-04
A heat sink isn't the only savior. You have to get a wattage resistor capable of handling that much power, and it will cost as they are very large and use components capable of handling the heat produced by the current going through the resistor. Many are aluminum cased, and the surface area is much greater than that of a more typical 5 or 15W resistor.
 

Gold Member
Username: Araknid

BOCA , FL U.S.

Post Number: 1377
Registered: Nov-04
Yeah I did get the thought from the W7 but it can be used in many different ways to get the impendance you want. I promise i will try it though. Whats the worst that can happen? The resistor failing?
 

Gold Member
Username: Insearchofbass

Post Number: 3909
Registered: Jun-04
Well if im following you right jonathan this is a problem with a high wattage speaker but if it was of a much lower value say 100 watts for one speaker this would be much easier to do ....I guess what I should be asking is in your opinion with exsisting technology in resistors what would be the maximum amount of power one could handle then I would say how could you over come the other factors you mentioned
 

Gold Member
Username: Insearchofbass

Post Number: 3910
Registered: Jun-04
bassmanmike get on aim if you can bud
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 5067
Registered: May-04
You can get resistors that can take thousands of watts, it's just that it'll cost you.
 

Gold Member
Username: Insearchofbass

Post Number: 3911
Registered: Jun-04
ok so now that i know resistors can handle large amounts of power my next logical step would be to figure out what makes up a resistor and what seperates the small capacity resistors from the large capacity ...what im pointing out for all of us here is its a step by step process of problem solving keping it within your desired cost range and type of useage
 

Gold Member
Username: Insearchofbass

Post Number: 3912
Registered: Jun-04
thanks for your replies jonathan
 

Silver Member
Username: Redskin

LondonEngland

Post Number: 235
Registered: Dec-03
I wouldn't get to bothered about ohm loads, just because a speaker is rated at 4 ohms doesn't mean it is a constant 4 ohm load. It will vary dramatically from that figure over the typical frequency range a sub handles. Adding series resistance alters speakers Qts. Large value inductors have resistance and no-one worries about burning those out in a rush. While writing this I remembered this link.......

http://www.audiodiycentral.com/resource/PLehmann/pikku9rev4.pdf

You'll need a PDF viewer to see it though.

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