I just built my first custom sub. How do I figure out how much power to throw at it? - Car Audio Classifieds!
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Old 10-06-2015, 01:40 PM
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Default I just built my first custom sub. How do I figure out how much power to throw at it?

Well, my first "from scratch" build went off without a hitch, and just 5 hours after the parts came in the mail, I got it all clamped up and drying in the kitchen. (Fun fact: the guys over at fixmyspeaker.com have never built a quad leadwire 2.5" spider before, or at least up until a few days ago. They thought I must have made a mistake ordering the damn thing.)

Overkill? Probably. But my build's full of overkill, so what's a little extra?

Anyway, after it's all said and done, there's still one question that remains unanswered: How much power will the damn thing take? I was planning on hooking it up to my amp and increasing the gain until I got scared, but there must be a more scientific way of finding that out.

Lets get down to the nuts and bolts of it:

Im using an Arc Audio Flatline motor, which has double stacked 6.7" dia ferrite magnets and a .51 inch top plate. Conveniently, the bottom plate is also milled out a fair bit, which means the bottom spider will contact the top plate about 3/16" before the voice coil ever contacts the bottom plate, so bottoming out and ruining the voice coil is impossible with this design.

Here's the link to the voice coil I'm using.

As mentioned before, I got quad leads on this thing, so that's not gonna be an issue. Soft parts (to the best of my knowledge) don't matter much, but they're all from fixmyspeaker, so they're top notch, if that means anything.

Anyone got an idea on this one? If you need more info about anything, just say the word. Thanks.
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Old 10-06-2015, 01:48 PM
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Old 10-06-2015, 01:58 PM
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Honestly, without getting all Einstein, here is only one way to find out what kinda power your driver can take.
And I'm afraid we gone need some pics or there will be consequences ...
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Last edited by colorblind83; 10-06-2015 at 01:58 PM. Reason: I Kid, but seriously though...
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Old 10-06-2015, 02:14 PM
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the issue with that much lead is mass. there heavy and restrict movement when the spider tries to move. they basically far exceed the thermal power limits of the coil, hence why they didn't understand why you wanted that.

theres two power limits. thermal and mechanical.

power handling doesn't equate to its wow factor or worthiness. especially if it doesn't use the power for gaining output.

mechanical limit is when the movement exceeds something that restricts its movement. if the surround allows so, the coil hitting the top plate would be the limit. the linearity of the spiders will create distortion at high throw once the leads start to hinder smooth travel.

thermal limits will only matter if the power applied is being put to use via movement of the cone. lets say the cone moves a max of 1" each way but you keep adding power. at that point the power is simply wasted and increases the coils temp causing rise in resistance.
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Old 10-06-2015, 02:15 PM
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Generically, I feel like 1k is about right on good 2.5" coils. Granted, many can take more, but 1k is a safe estimate
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Old 10-06-2015, 04:08 PM
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Any idea what stiffness and how many spiders you have?
Did you use a spacer if more than 1

That coil should take around 1000rms fairly easily
But I think you will reach mechanical limits before/mechanical problems if your spiders are too stiff

It should be a great sub
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Old 10-06-2015, 05:13 PM
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Quote:
Originally Posted by colorblind83 View Post
Honestly, without getting all Einstein, here is only one way to find out what kinda power your driver can take.
And I'm afraid we gone need some pics or there will be consequences ...
OP TO THE RESCUE!!!



Unfortunately, this is the only non-blurry photo I took mid-build. Sorry. I was just so focused, that I just didn't even think of documenting what I was doing.

But hey, to make it up to ya, I ran out to the other room and took a few photos of what it looks like now:








Literally all the welding clamps I could find in a 5 block radius went towards clamping that surround. And my god, what a sexy, sexy surround it is.


Quote:
Any idea what stiffness and how many spiders you have?
Did you use a spacer if more than 1
I have 2 8" medium compliance spiders. Used a .25" spacer. By the way, as far as I can figure out, there's no good way to install spacers. Unless you're literally building the thing in the basket from the ground up, spider by spider, you really have to get your hands dirty to get those things glued right in between the spiders. That was probably the hardest part of the build, by far.


Quote:
the issue with that much lead is mass. there heavy and restrict movement when the spider tries to move. they basically far exceed the thermal power limits of the coil, hence why they didn't understand why you wanted that.
Restrict movement? Even with PSI's fancy unobtanium thread, hand stiched a billion times around each lead for maximum durability and mobility? You know, the thing they're constantly bragging about on their websites?

In all seriousness, though, these things are stitched in SOLID with a good amount of slack between threadings. If your talking about the effect extra weight has on the spider, yeah, I can agree with you there, but as far as actually pulling the spider and restricting it from stretching, I can't see that happening.

Quote:
mechanical limit is when the movement exceeds something that restricts its movement. if the surround allows so, the coil hitting the top plate would be the limit. the linearity of the spiders will create distortion at high throw once the leads start to hinder smooth travel.

thermal limits will only matter if the power applied is being put to use via movement of the cone. lets say the cone moves a max of 1" each way but you keep adding power. at that point the power is simply wasted and increases the coils temp causing rise in resistance.
Believe me, I understand that completely. But knowing a ballpark figure of how much power you can expect to handle is still very useful and comes in handy pretty often when you're first setting things up- for example, I need to know whether I should wire the sub in series and bridge two amps at 1 ohm each to get 3K watts maximum RMS, or wire in parallel with one amp at .5 ohms for 2300 watts, or wire in series with one amp at 2 ohms for 1000 watts. So yeah, I get that more power =/= louder, but I still need to know.

And just for future reference's sake, here's the breakdown on the excursion limits: xmax, one-way linear: 1"; one-way non-linear: 1.5"; absolute max mechanical excursion, one way: 1.9375".
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Old 10-06-2015, 05:25 PM
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I'd say 2k at 1 ohm or 1k at .5 ohm is your max daily power.

How did you arrive at your throw numbers? Xmax should be driver movement within ideally 70% BL and xmech should be mechanical limits.

Also.. quad leads for a 2.5" coil is about 4x overkill...
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4 15s + Flat Wall + 10k = Loud

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Old 10-06-2015, 05:46 PM
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Quote:
Literally all the welding clamps I could find in a 5 block radius went towards clamping that surround. And my god, what a sexy, sexy surround it is.


I have clamp rings so you don't need so many clamps when you recone.

I have 2 8" medium compliance spiders. Used a .25" spacer. By the way, as far as I can figure out, there's no good way to install spacers. Unless you're literally building the thing in the basket from the ground up, spider by spider, you really have to get your hands dirty to get those things glued right in between the spiders. That was probably the hardest part of the build, by far.




Restrict movement? Even with PSI's fancy unobtanium thread, hand stiched a billion times around each lead for maximum durability and mobility? You know, the thing they're constantly bragging about on their websites?

yes. a lead wire isn't without resistance. they add a lot of weight and strain to move them when bunched together. ask anyone that designs subs. has nothing to do with the thread or how many wraps they sew them with.

In all seriousness, though, these things are stitched in SOLID with a good amount of slack between threadings. If your talking about the effect extra weight has on the spider, yeah, I can agree with you there, but as far as actually pulling the spider and restricting it from stretching, I can't see that happening.

it does and will effect efficiency . you basically doubled the resistance of the leads normally used.

Believe me, I understand that completely.
But knowing a ballpark figure of how much power you can expect to handle is still very useful and comes in handy pretty often when you're first setting things up- for example, I need to know whether I should wire the sub in series and bridge two amps at 1 ohm each to get 3K watts maximum RMS, or wire in parallel with one amp at .5 ohms for 2300 watts, or wire in series with one amp at 2 ohms for 1000 watts. So yeah, I get that more power =/= louder, but I still need to know.

And just for future reference's sake, here's the breakdown on the excursion limits: xmax, one-way linear: 1"; one-way non-linear: 1.5"; absolute max mechanical excursion, one way: 1.9375".
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Old 10-06-2015, 05:56 PM
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Wire it to .5 on one amp and be happy
You can always turn the gain down

I ran "theoretical" 5k to 2 8's daily, but I was cautious with the gain
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