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Free air question

Old 04-28-2006, 09:12 PM
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Free air question

I am thinking of mounting a pair of these EU700's:

http://edesignaudio.com/product.php?cid=15&pid=32&cur=USD

in the rear deck of my car. It had 5x7's originally, and I planned on making some adaptor rings, and deadening the hell out of the back dash. When I had a look last night though, I realized that there are two big holes in between where the speakers mount (in the middle of the back dash area). Probably 6"x6" each. If I deadened over top of these, and deadened the whole area around the back would it likely cause problems with air leaking through? Thanks!
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Old 04-28-2006, 11:42 PM
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Speakers are simple creatures. They require a box of some sort. When you have an unregulated port, or hole, or leak in some fashion, (the more the box flexes changes it too) they won't respond very well.

The bigger the box, the lower the frequency response. The smaller the box, the punchier it will be. The science is to find the best level for the sound that you're looking for.

When you start talking about free air, you start changing the variables.

What kind of trunk is this going to be in and what are the Thiel Smalls for this sub?
As each sub has a different set of specs, they will require a different setup.
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Old 04-29-2006, 02:05 AM
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Vehicle is a 1984 Toyota Cressida (old man luxury car). Decent size trunk, have not measured to get an idea of total volume of it yet. The EU700's are designed to work free air, specs:

re 3.2
fs - 28hz
bl - 13.3 TM
qms - 10.5
qts - .29
qes -.3
vas - 22 L
xmax - 13mm
spl- 85dB


Not sure if these are detailed enough for you, will try to find more complete specs.
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Old 04-29-2006, 07:59 AM
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The eu700's will work well in an IB set-up.

I think if you deaden the rear parcel shelf like crazy, maybe even cover those two larger openings with 1/4" panel board, then deaden, you will have created a good enough baffle to have made it an effective IB set-up for those drivers.
Or you could get 2 more and have 4 going on back there!

Always liked those old Cressida's; too bad they all rusted out around these parts...

Good Luck Jeepbeats.
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Old 04-29-2006, 09:30 AM
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Thanks Fever, sounds like a good plan! Yeah, mine is in surprisingly good shape, overall. Will post some pics one day.
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Old 04-30-2006, 09:39 AM
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Is it possible to re-do your rear shelf with quarter inch plastic to basically reintroduce a clean, flat baffle to the trunk? Of course you'll have to sound deaden the existing structure first, both sides. But that should give you what you're looking for.

It's unfortunate that the drivers are only 85db, as you'll have to put a lot of power to them in order to get the desired results. I typically look for drivers with a 90db rating, that way I don't need a lot of power to make them do what I want...POUND!
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Old 04-30-2006, 10:54 AM
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Yes, I will have to see what I can do with them, maybe I can add some reinforcement, and cover up the holes at the same time. Higher efficiency would be nice, will probably work alright though.
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Old 05-01-2006, 02:47 PM
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Question

^ Sooo you're pro-IB, why not offer some advice or guidelines to follow.
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Old 05-01-2006, 03:38 PM
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Cool

In an earlier post, he said that he didn't want to go too elaborate. My suggestion to use quarter ince plastice mounted to the double sound deadened shelf would be very appropriate for this application. If he really wanted to go full bore with it, I'd have suggested to cut out the existing structure and refabricate a new one from quarter inch aluminum.

As for the efficiency of a speaker having very little to do with the output of the system...I think that this is a totaly different topic and should be posed to the entire community for a debate on that.
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