2009 toyota corolla custom port slot box

2009 Toyota Corolla
2 x 12" Alpine Type R (2x2ohm)
1 x Alpine MRP-M1000 monoblock

I hope this is all the vital information needed about equipment.
The speakers are already in the car with a sealed box at a net of .80cf. It sounds good, but im in the mood for deep, low bass.
Everything forward i just need information about constructing a slot port box for the type R speakers.

I used mspaint to make a diagram of what i think will work(constructed out of cardboard and seem to be pleased, but will adjust accordingly). The dimensions on the back side are pretty much in stone. The front side can come out further if i need more displacement or less. I yielded 1.8cf per chamber with 3/4" mdf.



Now, i dont know anything about slot porting formulas, or frequency, etc. A lot of music is rock but i mix it up with rap etc.
For some reason everything i read was port tune to 33hz for the best sound quality and spl.

Please let me know what you think, what i need to change, what my missing dimensions should be(slot port length, width, height, and any bracing you think i should add).

kris

Yes, 32-33Hz is going to be a good frequency for both sound quality and output. So I would recommend tuning in that range if that is what you are looking for.

From your drawing I am betting you will have some issues with the slot port design. In order to get a 32-33Hz tuning frequency with that internal volume you are going to need a fairly long port. The port would not be able to fit in the area you have with that design unless you make the port area small.

The problem with making the port area small is that you will have port noise. So you need to find a mix between having a large enough area to not have port noise and not having too much area to have a really long port.

On the back of the enclosure you have a slant. Is there going to be another piece on the inside so the port area doesn't change? What I mean is that is the port going to be a rectangle for its entire length? If it isn't then that isn't a proper design. If it is then I wouldn't really see the point of it other then for aesthetics.

Thanks for the reply. I have ZERO knowledge of port design, but once i have it on paper i can make it happen. My dad is a wood worker and he owns ever piece of shop smith ever made.
Now let me try to answer everything.

Do i need to add more volume? I can achieve this easily as i have no limitations to the front. The rear has the limitations because of the angle of the back seat. I can straighten out the rear a little, but not too much. Can i still accomplish the goal with the rear at an offset?

Do you have an idea for the back side "piece on the inside". Im open to all criticism to make this happen. Aesthetics i guess are what its for, but im trying to utilize all the space available so its usable aesthetics.

I added a few inches to the front and cut off the angle part on the back. Can anyone suggest a good slot port design(just use a rough mock up in paint and ill be happy) for the following picture

You could use this design....



It is pretty much the same as what you drew except I had to lengthen it to make get the internal volume needed. This should work well for your Type-Rs.

The height is the same as well and you should make it out of 3/4" MDF. There is a little room available for adding bracing.

Thank you very much whiterob. You took the time to help me above and beyond. What program did you use if you dont mind me asking? I would like to give it a shot for future endeavors.
Kris

quick question for you white rob, or anyone else. When calculating displacement of the box does the port get calculated or do i stop calculating displacement to the point of the port opening?

Thank you,
kris

I ran all the numbers and i cam up with a net volume(gross volume - speaker displacement - port volume - mdf thickenss) and came up with 1.86 cf / chamber.

I have a port length of 36.5 inches
port volume of .541 cf / chamber

When i plugged everything into the calculator on the site i came up with a port tune of 31 hz.

Is 1.86 cf adequate air for the alpine type R's?

Do all the calculations sound correct?

Thanks again for all the help. Im thinking this will come out really well.

The port is not included in the internal volume calculation. The sub and any bracing displacement is also not included.

The Type-Rs perform well in a larger enclosure then what Alpine recommends. I typically use around 2 cubic foot tuned to 32Hz. In your case I didn't want to make the enclosure too large so I made it slightly smaller.

The internal volume will be slightly smaller once you add some bracing. This will also raised the tuning frequency. In the end it should be around 32-33Hz which is great for a mix of loudness and sound quality.

I use BassBox to figure out the specs to make the enclosure to. I then used SolidWorks to design the enclosure.

This enclosure design should work out pretty well for your subs. It will give you a pretty good mix of sound quality and loudness. It also has a good amount of port area to help prevent any port noise. If you wanted to adjust it slightly then you could add a little more internal volume. That would give you a little more output and a little deeper bass with a slight loss in overall sound quality. You would want to slightly shorten the port in order to keep the same tuning frequency though.

How does one know how large of a box to make vs how long of a port. I ask because i have been plugging numbers into the calculator here on the site and it seems like one could make a huge box with corresponding port length tuned to the Hz one would want and still have too large of a box. Where would one find the happy median or magic numbers? I guess what im trying to say is, If i didnt have your help, which i am glad i do, how could i figure this out?
kris

suprfast wrote:

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How does one know how large of a box to make vs how long of a port. I ask because i have been plugging numbers into the calculator here on the site and it seems like one could make a huge box with corresponding port length tuned to the Hz one would want and still have too large of a box. Where would one find the happy median or magic numbers? I guess what im trying to say is, If i didnt have your help, which i am glad i do, how could i figure this out?
kris

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Well that is kind of the trick to designing ported enclosures. There is no way to do it other then messing around with different configurations until you get an enclosure that will work the best. It involves a lot of trial and error until the best design is determine.

I personally always use a CAD program such as SolidWorks. This allows me to make slight adjustments in the design until I get what is required or what works the best.

When I design an enclosure I start with finding out the best internal volume and tuning frequency for the sub being used. So before I even start making my design I know what internal volume I need, the tuning frequency I need, and the maximum dimensions I have available.

Once that is determined I start my design in a CAD program. I plug in some initial values that are within the maximum dimensions available. I will make an "ideal" design which is typically a very large port. Then I modify the design until it meets my internal volume requirement. If this design is too large then I will modify the port and make it smaller which makes it shorter. I will do this until I finally figure out a design that will work. Sometimes it will require taking away internal volume or going with a smaller for in order to get the specs I need.

There is usually a give and take in a design. Unless you have a huge amount of area to work in you will have to give up a little something in the design.

I don't know if this is what you wanted to know but this is how I typically design an enclosure...

whiterob wrote:

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When I design an enclosure I start with finding out the best internal volume and tuning frequency for the sub being used. So before I even start making my design I know what internal volume I need, the tuning frequency I need, and the maximum dimensions I have available.

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Your first sentence is what im looking at. Apparently these sub manufactures (speaking on alpine particularly) claims that a 1.25 CF is ideal. Yet everyone i talk to and trust more than alpine says that a 2-2.5 cf box is the goal for the 12" type R. How do we know if the claim by alpine is rubbish? Is this what the calculators are doing for us with the Xmax, depth, numbers, etc?

Thank you again.
kris

suprfast wrote:

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Your first sentence is what im looking at. Apparently these sub manufactures (speaking on alpine particularly) claims that a 1.25 CF is ideal. Yet everyone i talk to and trust more than alpine says that a 2-2.5 cf box is the goal for the 12" type R. How do we know if the claim by alpine is rubbish? Is this what the calculators are doing for us with the Xmax, depth, numbers, etc?

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Well people that design enclosures will use enclosure designing software. If you use this software you can see that a larger enclosure that is around 2 cubic foot is going to be a bit better then Alpine's recommended enclosure.

This does not mean Alpine's recommended enclosure is bad. In fact, I can easily see why they would give those recommendations. Alpine is a large manufacturer which means they want to appeal to the largest audience they can. Most people don't want to have a large enclosure in their car. For this reason Alpine recommends a smaller enclosure.

Alpine will also recommend that enclosure because it is fairly forgiving. You can be a little off on the specs either way and not have a huge difference in overall performance.

I know that Alpine says that a 1.25 cubic foot enclosure is "optimum" in the manual. The truth is that there is no such thing as an "optimum" enclosure. The best enclosure design will depend on your own space available and your own type of performance. So if you are looking for something that is good for output you would have a different enclosure then you would if you were looking for sound quality. So the "ideal" enclosure is the one designed specifically for your own taste.

Thank you whiterob, i appreciate all the input. Helped me greatly.
kris