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Nutty question about running an amp at an 8 ohm load


philrab

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I know this sounds nuts, but hear me out: I have a Kenwood X500-1 amp in my car, a spare subwoofer (MTX road thunder 8", dual 4 ohm coils) and want to play around with designing and building my own T-line more for the experience than anything. I REALLY don't want to run this sub at a 2 ohm load since the sub is only rated for 100-200 watts, and 500 watts is almost sure to smoke the poor little thing. I'm especially thinking this since conventional wisdom is that a sub in a T-line on it's rated power tends to bottom out.

What I'm thinking is, if I wire the coils in parallel for an 8ohm load, I should be well under the 300 watts @4 ohms the amp is rated for, probably just about right for what I have in mind. The question is, is it going to frag anything on this amp if I feed it an 8 ohm load instead of 4 or 2 like usual? I've never tried it, haven't seen or heard of anyone trying it, don't want to burn down my equipment.

I'm just testing the waters to see if this is even feasible, since I have some spare wood and a spare sub. I guess push come to shove I could just run the sub at 2 ohms and turn down the sub level A LOT to keep from cooking or bottoming the sub out.

2015 Toyota Tacoma Build Thread

2007 Mazda 3; 5000K HID's, Kenwood Excelon KDC-X997, Infinity Reference 6.5 comps in front and coaxials in the rear doors, JL 320.4 four channel, Rab Designs built ported enclosure with an SA12, Kenwood monoblock, Redline Leater shift boot/e-brake boot/center console cover, JBR short shifter/shifter bushings/rear motor mount.

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1996 Mazda Miata: Kenwood Excelon HU, Alpine speaker in the doors, Clearwater (miata specific) headrest speakers. 

 

1994 Mazda Protege: Kenwood Excelon HU, Infinity Reference 2 ways all around, 2x RF Punch 10's in ported boxes. 

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Awesome, thanks guys for not flaming the shit out of me for such an off the wall question.

Now, time to do lots of reading up on T-lines.

2015 Toyota Tacoma Build Thread

2007 Mazda 3; 5000K HID's, Kenwood Excelon KDC-X997, Infinity Reference 6.5 comps in front and coaxials in the rear doors, JL 320.4 four channel, Rab Designs built ported enclosure with an SA12, Kenwood monoblock, Redline Leater shift boot/e-brake boot/center console cover, JBR short shifter/shifter bushings/rear motor mount.

Build Thread

 

1996 Mazda Miata: Kenwood Excelon HU, Alpine speaker in the doors, Clearwater (miata specific) headrest speakers. 

 

1994 Mazda Protege: Kenwood Excelon HU, Infinity Reference 2 ways all around, 2x RF Punch 10's in ported boxes. 

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Post some pics of the box after you get it done so we can see the good work. Let us know how it sounds

I'll be taking my time with this one. I have pics of the two ported enclosures I designed and built (first time designing my own, came out really good) in my build thread, definitely got the construction part of building enclosures down solid (did woodworking since I was a kid). The design work of a T-line I need to learn, and run through till I'm comfortable with it. Then a sketchup model. Then move to MDF. Just guessing at 8 ohms this sub will pull down roughly half what it does at 4 ohms would put me at 150 watts rms, about 3/4 the RMS the sub is rated for. If it sounds really musical and has good output, next step will be to step up to something like an SA10 with twin 4 ohm coils so I can wake that amp back up.

We'll see how it turns out. I tend to think that if you're designing and building enclosures, the worst thing you can do is stand still. I want to keep pushing myself, more intricate designs and more precise enclosures, just keep refining my skills. I was teetering on building a 4th order bandpass or a 6th, but a T-line is something that little bit less commong that would make for a nice experiment and demonstration. Also figuring if it sounds good, it'll end up getting throw on a little Home AV amp and see how it does as part of the garage sound system. Never know if I don't try it out.

2015 Toyota Tacoma Build Thread

2007 Mazda 3; 5000K HID's, Kenwood Excelon KDC-X997, Infinity Reference 6.5 comps in front and coaxials in the rear doors, JL 320.4 four channel, Rab Designs built ported enclosure with an SA12, Kenwood monoblock, Redline Leater shift boot/e-brake boot/center console cover, JBR short shifter/shifter bushings/rear motor mount.

Build Thread

 

1996 Mazda Miata: Kenwood Excelon HU, Alpine speaker in the doors, Clearwater (miata specific) headrest speakers. 

 

1994 Mazda Protege: Kenwood Excelon HU, Infinity Reference 2 ways all around, 2x RF Punch 10's in ported boxes. 

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I know this sounds nuts, but hear me out: I have a Kenwood X500-1 amp in my car, a spare subwoofer (MTX road thunder 8", dual 4 ohm coils) and want to play around with designing and building my own T-line more for the experience than anything. I REALLY don't want to run this sub at a 2 ohm load since the sub is only rated for 100-200 watts, and 500 watts is almost sure to smoke the poor little thing. I'm especially thinking this since conventional wisdom is that a sub in a T-line on it's rated power tends to bottom out.

What I'm thinking is, if I wire the coils in parallel SERIES for an 8ohm load, I should be well under the 300 watts @4 ohms the amp is rated for, probably just about right for what I have in mind. The question is, is it going to frag anything on this amp if I feed it an 8 ohm load instead of 4 or 2 like usual? I've never tried it, haven't seen or heard of anyone trying it, don't want to burn down my equipment.

I'm just testing the waters to see if this is even feasible, since I have some spare wood and a spare sub. I guess push come to shove I could just run the sub at 2 ohms and turn down the sub level A LOT to keep from cooking or bottoming the sub out.

See above.

Raising the impedance on an amplifier is always fine.

Extrapolate that a little bit for a thought experiment:

Your amp is fine with no speakers connected, right? (just air).

That air will have an impedance in the high MEGA ohm range, maybe even GIGA ohms.

So therefore the amp should be fine between its rated impedance and the mega-ohm range of nothing connected.

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^^^ Thanks Wick. Didn't seam like it would hurt anything, but I second guess myself.

2015 Toyota Tacoma Build Thread

2007 Mazda 3; 5000K HID's, Kenwood Excelon KDC-X997, Infinity Reference 6.5 comps in front and coaxials in the rear doors, JL 320.4 four channel, Rab Designs built ported enclosure with an SA12, Kenwood monoblock, Redline Leater shift boot/e-brake boot/center console cover, JBR short shifter/shifter bushings/rear motor mount.

Build Thread

 

1996 Mazda Miata: Kenwood Excelon HU, Alpine speaker in the doors, Clearwater (miata specific) headrest speakers. 

 

1994 Mazda Protege: Kenwood Excelon HU, Infinity Reference 2 ways all around, 2x RF Punch 10's in ported boxes. 

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Wicks as usual making everything super simple. I feel like an idiot now

750??! Yeah, fuck that. Fuck this website, fuck SMD, fuck Steve, fuck all of his butt buddy mods, and their couches.

^ DON'T BE A DICK LIKE THIS GUY :)

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I know this sounds nuts, but hear me out: I have a Kenwood X500-1 amp in my car, a spare subwoofer (MTX road thunder 8", dual 4 ohm coils) and want to play around with designing and building my own T-line more for the experience than anything. I REALLY don't want to run this sub at a 2 ohm load since the sub is only rated for 100-200 watts, and 500 watts is almost sure to smoke the poor little thing. I'm especially thinking this since conventional wisdom is that a sub in a T-line on it's rated power tends to bottom out.

What I'm thinking is, if I wire the coils in parallel SERIES for an 8ohm load, I should be well under the 300 watts @4 ohms the amp is rated for, probably just about right for what I have in mind. The question is, is it going to frag anything on this amp if I feed it an 8 ohm load instead of 4 or 2 like usual? I've never tried it, haven't seen or heard of anyone trying it, don't want to burn down my equipment.

I'm just testing the waters to see if this is even feasible, since I have some spare wood and a spare sub. I guess push come to shove I could just run the sub at 2 ohms and turn down the sub level A LOT to keep from cooking or bottoming the sub out.

See above.

Raising the impedance on an amplifier is always fine.

Extrapolate that a little bit for a thought experiment:

Your amp is fine with no speakers connected, right? (just air).

That air will have an impedance in the high MEGA ohm range, maybe even GIGA ohms.

So therefore the amp should be fine between its rated impedance and the mega-ohm range of nothing connected.

Always wire to 1.21 jigga ohms just to be safe.

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