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Discussion Starter #1
A few weeks ago (before I even owned an Altima ;) ) someone asked about replacement speakers for the rear and poisonfist recommended an odd approach - put 6.5" subs in there instead of full range coaxials. I know this will mess up the soundstaging for anyone riding in the back but I don't care about that. I'm definitely not going for SPL, and extreme SQ isn't my goal either - just good sound while I'm driving. I'm already planning on replacing the stock HU and fronts.

Sooo, if I put a pair of 6.5" subs back there, how will they sound? Looking at the specs on the 6.5" RF HEs, it doesn't look like they are designed for free air use. Will the trunk act as a huge and really crappy box? Will I get an appreciable amount of base? I'm not looking to thump the paint off the body panels or shatter the exhaust hangers, just better than stock or aftermarket coaxails can put out.
 

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Mine's bigger than yours
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unless you can find some free air 6.5" subs then i wouldn't put them back there, if you try to free air non free air subs it just turns out to sound like ass....
 

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Nipponese
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5,458 Posts
What to look for is high QTS, since an infinite baffle configuration will not have the damping factor of enclosures, you need to have as much on the driver itself. As a general rule of thumb, you should have a driver with a QTS greater than 0.60 for it to sound good. I would recommend a driver with a QTS close to 1.0.
 

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Nissan God
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poisonfist said:
What to look for is high QTS, since an infinite baffle configuration will not have the damping factor of enclosures, you need to have as much on the driver itself. As a general rule of thumb, you should have a driver with a QTS greater than 0.60 for it to sound good. I would recommend a driver with a QTS close to 1.0.
lol, its been a while
 

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Nipponese
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OK, this is just for you So ;), QTS is the total damping factor of a given driver (more damping = more control). There are two types of damping factors to drivers, QES, which is the electrical damping factor. This usually comes from larger magnets which will have better control of the voice coil motion. The second is QMS, which is the mechanical damping factor. This results from combination of several things. First, a lighter cone will give higher control (think of trying to move your arm in a precise motion, try doing that with extra weight (i.e. holding a dumbell in your hand) it will become increasingly difficult to move quickly and precisely), and second, the stiffness of the spider and the surround. To be able to control is the most important factor when it comes to infinite baffle (a driver mounted on a board without an enclosure), because it doesn't have the help of the damping factor that a sealed encloser would give to the driver (think of an enclosure as a spring, if it's sealed when the driver pushes in, the air inside will be compressed and will have a pressure to push out, and when the driver is pushed out, ther will be a little bit of vacume which it'll try to pulll in. This get's more complicated when it's a bass reflex enclosure). This is how many manufaturers get away with low resonant frequency, low VAS drivers, they don't give the driver itself much damping factor (control) it relies on the enclosure for the damping factor. This is also why many cheap car audio subs sound slow and muddy.
 

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Discussion Starter #8
Well, the RF has a listed QTS of 0.58, so it will probably sound pretty blurred. Do you know of any specific 6.5" subs that have a high enough QTS for this application, or can you give me some ideas as to which brands might make a 6.5" that will work for this application?
 

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Dreamer
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2,712 Posts
the audiobahu AMD60 midbass works with an infinite baffle. I have them and I think they are really good. Goes down to 35-40hz. It won;t be loud outside, but its pretty decent inside :D


and if you decide to put subs in the rear deck, be prepared to get LOTS of dynamat cause it will not stop rattling. You also have the problem of the cone hitting the rear deck cover from the excursion of the cone. I have this problem and I am thinking of cutting a hole on the cover for speaker grills. I hole it won't look getttttttooo
 
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