Box Building, Amp Matching

[Island Bumpkin]

I'm currently working on adding some low end to my current car, a 99 Accord with a JVC head unit and Pioneer TS Series speakers in the front and back.

I've been eyeing the Sundown E series woofers for a couple years now, but I've never really been in the financial situation to go forward with the project (Not to mention I've gone through a few different vehicles in that time). In the mean time, I've been researching box theory and learning what I can. The last time I was working on box designs I came up with something that I thought would work, but it was just my luck I lost track of the Solidworks file. Instead of trying to recreate what I had before, I figured I'd try my hand again.

Sundown recommends a 1 ft^3 tuned to 33 Hz for their 10" when using a ported system. They also recommend having a port CSA of 16 inches, so using that info I went to mobile info labs to figure out my port size. What I came out with was a port 1 1/3" x 12" x 35.65 inches long. This was the result

3/4" baltic birch

http://i986.photobucket.com/albums/a...ps1rqilbrt.jpg

Internal structure feat. port length

http://i986.photobucket.com/albums/a...ps3ymyhsma.jpg

Iso-ish view without top and bottom

http://i986.photobucket.com/albums/a...psgfnbcbke.jpg

For rigidity, the internal pieces are a half inch longer than the exterior pieces so I can sink them 1/4 inch into the top and bottom plates.

http://i986.photobucket.com/albums/a...psifpb0pag.jpg

Volume of the box minus the port is 1.03 ft^3, which means with the sub in there (.11 ft^3 displacement) it would be around .91. Thought's on this being too small?

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Next on the dockett is an amp. I can't really afford anything more than $150, which I know isn't ideal. I was looking at 2 different factory referb Kenwood units, a Kenwood KAC-5001PS and a Kenwood X500-1, and a new Power Acoustik RZ11500D PA. The two kenwoods are both a 500W @ 2 ohm load, and the Power Acoustik is 900. The RMS on the E10 v.3 is 600W, so the kenwoods would be under and the PA would be over. I was leaning towards the PA because it is "overpowered", but I worry about the brand. I know Kenwood has a fairly good reputation, so I'm leaning towards that now. Comparing the Kenwood models, the only difference I found was the signal to noise ratio is 81 vs 83, while the PA is 70. Based purely off that, I would think the X500-1. Thoughts?

Thanks in advance

Jameson

[Island Bumpkin]

Just realized my photos didn't work. Here are updated links

http://rs986.pbsrc.com/albums/ae344/The_Muffin_Man2/Full_zps1rqilbrt.jpg?w=480&h=480&fit=clip

http://rs986.pbsrc.com/albums/ae344/The_Muffin_Man2/Port%20Measurement_zps3ymyhsma.jpg?w=480&h=480&fit=clip

http://rs986.pbsrc.com/albums/ae344/The_Muffin_Man2/Isoish_zpsgfnbcbke.jpg?w=480&h=480&fit=clip

http://rs986.pbsrc.com/albums/ae344/The_Muffin_Man2/Sunk%20in_zpsifpb0pag.jpg?w=480&h=480&fit=clip

[Triticum Agricolam]

Your box layout looks pretty good. Having .91 cu ft of internal space shouldn't cause any problems, though it will raise the tuning a little bit.

With your port being 1-1/3" wide x 12" tall it has an aspect ratio of almost 10:1, which is higher than I like to see, but there probably isn't much you can do about it without significantly changing the box dimensions. With the amount of power you are going to be running, your port velocity should be fine.

Making the internal panels larger and cutting rabbets in the top and bottom panels really is unnecessary and will make getting everything to fit well more difficult. If you feel you have the woodworking skills to do it well and want to do it then go ahead, but if it was me I would just cut those panels the same width as everything else and not worry about it. Your box will be PLENTY strong all the same.

I'd avoid that Power Acoustik amp, just based on its fuse rating its not likely it put out much more than 400 watts. Either of the Kenwood amps would be better.

What part of Washington are you in?

[Island Bumpkin]

Your box layout looks pretty good. Having .91 cu ft of internal space shouldn't cause any problems, though it will raise the tuning a little bit.

With your port being 1-1/3" wide x 12" tall it has an aspect ratio of almost 10:1, which is higher than I like to see, but there probably isn't much you can do about it without significantly changing the box dimensions. With the amount of power you are going to be running, your port velocity should be fine.

Making the internal panels larger and cutting rabbets in the top and bottom panels really is unnecessary and will make getting everything to fit well more difficult. If you feel you have the woodworking skills to do it well and want to do it then go ahead, but if it was me I would just cut those panels the same width as everything else and not worry about it. Your box will be PLENTY strong all the same.

I'd avoid that Power Acoustik amp, just based on its fuse rating its not likely it put out much more than 400 watts. Either of the Kenwood amps would be better.

What part of Washington are you in?

If the volume is going to affect the tuning, should I adjust the port to lower the frequency? Making it 31 Hz would only increase the port length by 5ish inches.

As far as the rabbets are concerned, I am able to easily do them as I'll be using a (very old) shopbot to make cuts. But it occurred to me, unless I use a smaller bit and make multiple passes to cut the pockets, I'll have to radius a full semicircle rather than just the edges. While it's not the end of the world since it's only a 1/4 inch on each end, it's still just a tad more work.

I had two reasons for wanting rabbets; The first was for the ease of assembly, since it's much easier to place "floating" pieces when they have matching holes to go in to on either side of the box so there's little chance of them getting out of alignment due to errors in measuring. The other reason was to reduce the number of fasteners. By making rabbets I am able to fill em up with glue, then use the upper and lower pieces (that get screwed to the exterior) to put them in a state of permanent compression and thus not requiring me to put in screws in the middle of the box.

I guess my next question is in regards to the thickness. I figured 3/4 inch because I want this to be as strong as possible. but looking at the boxes you have done, I wonder if I might be overbuilding. Would 5/8 be a better choice? It'd sure help to keep the weight and size down...

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I live on the west side of the mountains. South end of Whidbey Island, which is about an hour and a half north of Seattle. Although I am currently in the corn field that is Iowa as I'm attending Iowa State University.

Thanks!

Jameson

[ckeeler11]

Your box layout looks pretty good. Having .91 cu ft of internal space shouldn't cause any problems, though it will raise the tuning a little bit.

With your port being 1-1/3" wide x 12" tall it has an aspect ratio of almost 10:1, which is higher than I like to see, but there probably isn't much you can do about it without significantly changing the box dimensions. With the amount of power you are going to be running, your port velocity should be fine.

Making the internal panels larger and cutting rabbets in the top and bottom panels really is unnecessary and will make getting everything to fit well more difficult. If you feel you have the woodworking skills to do it well and want to do it then go ahead, but if it was me I would just cut those panels the same width as everything else and not worry about it. Your box will be PLENTY strong all the same.

I'd avoid that Power Acoustik amp, just based on its fuse rating its not likely it put out much more than 400 watts. Either of the Kenwood amps would be better.

What part of Washington are you in?

If the volume is going to affect the tuning, should I adjust the port to lower the frequency? Making it 31 Hz would only increase the port length by 5ish inches.

--

Thanks!

Jameson

Remember lengthening the port will take away more box volume. you would have to increase the external dimensions of the box.

[Island Bumpkin]

That reminds me, When I'm looking at the volume of my box, do I include the air inside the port or not? Or do I just look at the "free" space before the port?

[Triticum Agricolam]

You can make the port longer to lower the tuning frequency back down, but I'd only do that if you are willing to increase the external dimensions of the box. Otherwise making the port longer will eat up more internal volume, which will again raise the tuning and you quickly find yourself in a "chasing your own tail" type situation.

If you want to do the rabbets, there really is not reason not to other than the additional effort, so I say go for it.

As far as using 3/4" material goes, its kinda the standard for box building, but it isn't a requirement and you don't have to use it. Box strength comes down to a lot more than just material thickness. I know of boxes and are getting thousands of watts put to them and are built out of 1/2" material and are very rigid and strong. Though they were carefully designed from the beginning to use 1/2" material and are doubled up were needed and are well braced.

If you want to save weight the first thing I would do is not use MDF. I use Arauco plywood for most of the stuff I build. Its lighter and stiffer than MDF, but you may have to look around a bit to find it in your area. For further weight savings you could go down to 1/2" material, either Arauco or true baltic birch. You will need to add some significant internal bracing though.

[Island Bumpkin]

I was already planning on Baltic birch. I don't have any problems making it larger, but I'm wondering if it's worth the extra material?

[Triticum Agricolam]

There shouldn't be any difference in performance between a 1/2" material cabinet and a 3/4" material one. You just have to ask yourself if the potential weight savings is worth the extra bracing effort the 1/2" cabinet will require.

[Island Bumpkin]

I added 1/4" to the interior depth dimension and adjusted my port, and that bumped the volume up to 1.12 cubes, so I'll be right on the money

Thanks
Jameson