Okay I bought this TC OEM 10 and a PR for it and want to use it but not sure how to make the box to make them fit and not take up too much of my trunk space. The sub has a mounting depth of 7.5 inchs and weighs in just under 30 lbs, the PR looks identical to the sub but has a mounting depth of 3 inches. I need to box to be around .7 ft of airspace, do you guys have any ideas?
PR
note this is not my picture so neither is the toe
A subthump type of box will not work due to the passive radiator should be horizontal so it does not sag (think of it as a sub with no motor on it)
I was thinking of something similar to my current box but for 2 10s instead of my current 1 12, anyone have any other ideas? The way the current box works is that it sits in the little rectangle part of the center storage bin and the sub faces forward, so it still leave the slope portion of the center storage bin.
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2008 Corvette Z51
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Last edited by PolishDude; 06-06-2007 at 06:40 PM.
Hmm only think I could think of is a relatively tall box that sits into the center compartment and has the 2 subs back to back inside of it. Maybe a tall wide to narrow shape with the subs firing angled upward on the opposing sides.They make a nice sub for sure but I do not know enough about passive radiators and their configuration options to give you much more of an option. I don't believe that you could build a chambered box of different air spaces so to speak and have the PR work correctly nor do I know for sure whether a basic rectangular box will work with the sub and pr on the same side.
You could always pick up an ED 300w plate amp for $90 and build yourself a nice HT sub with that
i heard these subs barely move at 600 watts...haha. They can be on the same side, thats why I am thinking just basically doing what I already have accept have two subs rather then just one
i heard these subs barely move at 600 watts...haha. They can be on the same side, thats why I am thinking just basically doing what I already have accept have two subs rather then just one
They have to move to make sound. The larger the movement, the larger the sound. A good woofer will move with very small amounts of power.
Passive radiators do need to be vertical. The purpose is to make the box act as a much larger box. So they must share the same box space in order to work. The shape of the box is of little consequence. I assume that the .7 cu.ft. box was recommended including the passive radiator? You will notice a weight built into the dome of the PR. This has been calculated along with its diameter to work in a specific volume with a specific woofer.
Passive radiators perform fundamentally the same as port tubes. There are very specific requirements for their use, and it's more stringent than designing with a tube. They don't need to be vertical any more than the driver itself does. The spider in the passive radiator returns the radiator's cone to neutral, not gravity. The calculations are somewhat complex. Do whatever the manufacturer says in designing the enclosure (I'm assuming they intend this radiator to match this driver) unless you have very specific moving mass and compliance numbers for the passive radiator.
Passive radiators perform fundamentally the same as port tubes. There are very specific requirements for their use, and it's more stringent than designing with a tube. They don't need to be vertical any more than the driver itself does. The spider in the passive radiator returns the radiator's cone to neutral, not gravity.
You are probably right about vertical mounting but my experience with a particular passive radiator with a large mass would make me not do it. I guess it depends on the amount of weight on the cone, the spider/suspension will definitely be stressed to one side which would make me have doubts about its performance. I have not actually measured the difference if any. On the other hand, I have a speaker system right here in front of me that uses a passive. It has a small mass and seems to look fine when tilted on it's back. No perceptable movement.
The PR is specifically designed for this sub, even looks identical to the sub on the cone side. In that pic you can see it has a long threaded rod in the back, that is where the weights go so that you can tune it to your specific frequency. When I was looking at it, I too thought that it should not matter if its not horizontal because the thing is STIFF, it literally takes probably around 10 lbs of force to move it so I was thinking if its laying flat with a few grams of weight on it, it should be fine but I will consult with the people of TC.
According to everything I have read at TC, you should not mount the PR horizontal. While I don't necessarily agree, I can understand why the recommend this.
"Somebody" is concerned that the weight of the PR and the gravitational forces acting on it will somehow cause it to perform incorrectly.
All things being equal, motion of the cone will be in/out... and in a vertical plane the acceleration due to gravity is a non-factor.
When mounted in a horizontal plane, the acceleration due to gravity will have to be considered when looking at the PR cone motion. The cone will have to overcome the gravitational forces when moving outward (up) and will be additive when moving inward. (down) The driver motor will have to overcome it's own cone mass AND the PR mass upwards... but will have less 'effort' downwards.
How much effect are we talking about here? Depends on the mass of the cone, the PR, the force applied, and the spring coefficient of the spider/surround. I don't have the info in front of me, so I really don't know...
But if the folks at TC are saying to run it vertical vs. horizontal... they must have a reason for doing it. Why not ask them in their forums?
Mark
Last edited by Fasthotrod; 06-07-2007 at 03:21 PM.
Already did, but yeah you are right, I thought about how gravity effects it that way. Now If i can just figure out a box that wont look like ass and work.
Come on there are a couple box builder's out here, be creative, I will need your services to build the box anyways..haha
All things being equal, motion of the cone will be in/out... and in a vertical plane the acceleration due to gravity is a non-factor.
Gravity is a non-factor anyway, as it is with the driver itself, UNLESS a large amount of weight is added to the PR. If gravity had to be considered, this would be a seriously loose suspension and obviously that's not the case here. Also, the driver itself would be just as susceptible to this problem. If TC is recommending horizontal mounting, then it likely has something to do with the method in which any added weights are distributed.
Quote:
The PR is specifically designed for this sub, even looks identical to the sub on the cone side.
This is because that's exactly what a PR is: a driver minus the motor assembly (i.e.: the voice coil, magnet structure...) The spider's function is to provide the restoring force to neutral. The surround merely keeps the cone centered in the lateral plane. Compared to the strength of the spider, the surround (and gravity) are weak at best.
Think of a PR like a port. The extra mass is akin to lengthening the port tube, and lowering the resonant frequency of the enclosure. The PR's function is to share the load with the driver at frequencies above Fb, just like a port. Above Fb, the driver has no *extra* work to do to move the PR, no matter the physical alignment. The PR makes the driver more efficient. The PR/box compliance factors are very important, but gravitational acceleration is irrelevant.
looks like you know your stuff on this, are you saying I should be okay mounting this thing horizontally? If I put on all the weights that the thing came with it would not even move the thing, thats why i dont see sagging as a problem. I just dont want to spend money on a center storage bin box to only find out it doesnt work with what I have.
In terms of functionality, and assuming TC doesn't have some special requirement, yes, you can mount both facing upward. Make sure you have specs to determine EXACTLY how much mass to place on the PR shaft, though. This will be determined by the size of the box, and TC should have a simple table to reference. This isn't something you can just *wing*. Whether this is a viable driver combination in your car, I can't say.
In terms of functionality, and assuming TC doesn't have some special requirement, yes, you can mount both facing upward. Make sure you have specs to determine EXACTLY how much mass to place on the PR shaft, though. This will be determined by the size of the box, and TC should have a simple table to reference. This isn't something you can just *wing*. Whether this is a viable driver combination in your car, I can't say.
Yikes, I thought all you needed was wood/screws/glue!
As I stated earlier, I think it depends on how much weight the PR has on it. Some PR's have very little and others have a significant amount. If TC recommends it being vertical, they have a reason and although it may not make an awful lot of difference it may make SOME. The PR is always significantly heavier than a normal speaker cone. It does move in and out like a speaker and is tuned to replace a port in an ADDITIVE function. If its movement is not symmetrical in both directions, it is distorting its output, no if's and's or but's. Gravity can and will have an effect on it if the mass is significant enough. But then whether it is an audible difference or not is another issue.
After an evening of digging through my reference materials... Robvuk is correct, however this is an issue of extremes. If enough mass is added to a PR, it can sag. That said, the alignments this applies to are rather exotic and well beyond the scope of this thread. They also won't be found in car audio (at least none I'm aware of), so the horizontal/vertical mounting question then is moot.
In this particular case, the PR is nearly identical to the driver in terms of it's area, so this easily qualifies as a traditional PR configuration, and unless significant weights are added (more than 3-4x the driver's cone mass), or they're added in such a way as to make the PR response non-linear, the mounting method doesn't matter.
Bottom line... if TC says vertical only, obey them, but it would help if you can share their reasons for doing so, as there are a few possibilities.
Wonder if you could get the 2 side by side with enough airspace to make it work in the center storage bin .. might need to come up a couple of inches above the factory floor but I bet you can make it happen. Couple inches out of the floor minus the woofer displacement should get you to 1cu^3 pretty easily. Would look like the subthump dual 10" box or the one that NVTHIS builds.
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Some box ideas...
A good woofer will move with very small amounts of power. 
Yikes, I thought all you needed was wood/screws/glue!
