prefab ported box

yea i said it! PREFAB! haha i know its the best thing but im in a hurry and have no time to find someone that can make me one.



im planning to put a Type-R in this box. you think it will be loud? i have a 4 door 93` camry.

here are the dimensions: 30.75"X15.5"X15.5" & .75 MDF

Are those inside or outside dimensions?  The dimensions of the port will probably help.

i am an idiot wrote:

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Are those inside or outside dimensions?  The dimensions of the port will probably help.

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im not sure if its inside or outside.

about the port dimensions.. . do you want the length and width of the port?

Measure the outside demension of the box and post that then all the measures you can do of the inside of the port... ie... LxWxD.... then post that.

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Jayce

IF it is a Type-R DVC @ 4 Ohms, 12" driver-

Using this site's calculator and NOT knowing the port dimensions-

It's too big.

Alpine recommends a bass reflex (Ported/4th order bandpass) enclosure of 1.7 Cubic feet. The driver displaces a small amount of that space, but the box dimensions you listed without knowing how it's port dimensions in detail calculates out to 3.31771 cubic feet.

Find us the port dimensions on that slot and we can tell you more...

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Life is too short to build slow computers or weak audio!

wolfox wrote:

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Find us the port dimensions on that slot and we can tell you more...

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when you say port dimensions, are you asking the dimensions inside or the outside?

imupabove wrote:

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wolfox wrote:

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Find us the port dimensions on that slot and we can tell you more...

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when you say port dimensions, are you asking the dimensions inside or the outside?

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Yes, we need to know the square surface area of the port opening (H x W) and then the depth of the port into the box itself (L). The port's total volume (H x W x L) along with the speaker's displacement will tell us the net internal volume and give us an idea what it is tuned for in Hz.AND tell us how much space is in there. I got my DVC Type-R 12" tuned to 34 Hz in my ported, 1.7 cubic foot box. It sacrifices a little of the total SPL, but it's immensely musical, deep and plenty powerful to shake mirrors and deflect door psnels on a mere MRP-M500 Vpower monoblock. :D

It's in a Blazer so the smaller overall dimensions help in maintaining at least half of the cargo area. A consideration to take to heart in your compact car. ;)

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Life is too short to build slow computers or weak audio!

okay great! thanks for clearing that up for me :]. im going to send an email to the box's company.

just to make things for sure .. .

so you need to know the (H x W) of port's opening. and the ( L ) of the port inside right?

wolfox wrote:

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IF it is a Type-R DVC @ 4 Ohms, 12" driver-

Using this site's calculator and NOT knowing the port dimensions-

It's too big.

Alpine recommends a bass reflex (Ported/4th order bandpass) enclosure of 1.7 Cubic feet. The driver displaces a small amount of that space, but the box dimensions you listed without knowing how it's port dimensions in detail calculates out to 3.31771 cubic feet.

Find us the port dimensions on that slot and we can tell you more...

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Recommended specs are worthless. They are merely just a starting point for no particular install at all.

Type R's like big boxes...atleast 2 cubic feet net volume for ported...sealed they sound like crap

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Custom Enclosure Design

aznboi3644 wrote:

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Type R's like big boxes...atleast 2 cubic feet net volume for ported...sealed they sound like crap

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I got some MDF and other supplies laying about - it will not take much to go up an extra .3 Cubic feet. In your experience, how well does it sound/perform in the larger enclosure? Color me curious and willing to accept input on this too. :D What tuning frequency do you lump in with that and suggest? My fear is the sub unloading at lower freq and larger cabinet volumes even with a steep 24 Hz rolloff with my MRP-M500 (fixed - non negotiable I am afraid) Thanks in advance!

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Life is too short to build slow computers or weak audio!

what will it sound like if the box is too big?

imupabove wrote:

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what will it sound like if the box is too big?

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Low frequency power handling may suffer, but the bass response is tighter and "dryer". You may hear the system get "louder" in a narrow frequency range as a result too. (BOOMY peaks/resonance rather than having flat, linear response.) A good read on the subject is here:

The DIY Subwoofer page - pay attention to section 1.05!

In short, a quote:

1.05 - What happens if the box is too large? Typically the low frequency extension of the system improves a little, at the expense of powerhandling. The bass will also sound tighter and "drier", which might not suit your listening tastes. In the case of vented systems, a too-large box may introduce a response peak around the resonance frequency of the system.

There is a megaton of great info on that site that applies to mobile and home theater systems.

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Life is too short to build slow computers or weak audio!

i got the dimensions:

Vent opening 33 square inches
Vent length 16 inches long

thank you.

Type Rs have no problem with going below tuning.

I used to run a single Type R 12 in an 8 cu ft transmission line enclosure. Played 10Hz at 700 watts no problem.

For R's if the enclosure is too small it will sound like a sealed enclosure...low end starts rolling off with a hollow low end.

Me I would do atleast 2.5 cu ft tuned to 30-35Hz.

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Custom Enclosure Design

aznboi3644 wrote:

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Type Rs have no problem with going below tuning.

I used to run a single Type R 12 in an 8 cu ft transmission line enclosure. Played 10Hz at 700 watts no problem.

For R's if the enclosure is too small it will sound like a sealed enclosure...low end starts rolling off with a hollow low end.

Me I would do atleast 2.5 cu ft tuned to 30-35Hz.

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what do you think about the box. on the website its 2.5 cu. ft. but not sure what its tuned at. i got the port dimensions, its on the last reply.

As close as I can model that subwoofer enclosure from listed dimensions and an educated guess from the port dimensions you listed - the computer spat out this:

Assuming an Alpine Type-R SWR-1242D running wired in parallel for 2 ohms load and 500 Watts RMS with THAT particular box at the beginning of your post...





Box Properties
Name:
Type: Vented Box
Shape: Prism, square (optimum)
Vb = 2.916 cu.ft
Fb = 35.36 Hz
F3 = 33.23 Hz
Fill = none
No. of Vents = 1
    Vent shape = rectangle
    Vent ends = one flush
    Hv = 13.04 in
    Wv = 1.863 in
    Lv = 16 in

This is of course an educated guess, feeding numbers through Bass Box Pro v6. based on info you provided and trying to massage the numbers as close as possible to the dimensions you listed. (it fusses a little bit at you after a while if you go a little too far out of spec for the driver, etc. etc.) Though not a *perfect* match, it is NOT bad. It's tuned to approximately 35 Hz (give or take (L)User error on my behalf) which will make it stand out in presence. Lower end response suffers a little bit (I like extended bass myself) but then does unload steeply after 20 Hz. so be sure that your amp's low freq. filter is operational and you will have no worries.

Big ups to aznboi3644 BTW, you are right. I modeled a few changed box parameters based on my prior design for my truck. Tossing it about Vb@2.5 or so and getting it tuned lower makes it shine just that much more brilliantly. Time to pick up the tools and build. :D I got it currently in a Vb=1.7^3 ft. ported box tuned to 34 Hz. Built to your suggestion will extend the lows out just a bit more without worry of unloading - thanks for getting me thinking!




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Life is too short to build slow computers or weak audio!

OR i have another option.. .

their is this guy that has been building boxes for about 5 years. he said he has to measure my trunk first. he charging me 80 bucks but with no carpet and 110 with carpet. ive also seen his work/projects they look nice. should i go this route instead? if so where should it be tuned for really loud bass?

wolfox wrote:

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As close as I can model that subwoofer enclosure from listed dimensions and an educated guess from the port dimensions you listed

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it wasnt a guess. i asked directly through the box's company.

i have 2 12" old school(swr-1241d) 4 ohm dvc type r's for the wifes drango. the box i got for them is as fallows;

30.5"x14"x19"(out side) the port is12.25x2.5x14.5(in side) 

i came up with 34-35Hz and about 1.75ft^3 per driver.

with the port in the middle of the box does that mean its a "common air space" style box? there is not a divider just the one port in the center of the box.

and will this box do the typer r's justice?

they will be powered by a new RF power 1000db,.and they will be ran @ 1ohm.

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Before you see the light, you must die!!

More than likely the box was designed with that common airspace in mind. You can happily do that and does not mean that anything is wrong with the box build from what I have read in passing many moons ago. It just makes it difficult to diagnose if you have one woofer go bad and they are wired in a manner that allows them both to fire from one set of terminals. The working woofer will make the "dead" one jump and vibrate and it can appear that all is okay, though sound would have diminished some.

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Life is too short to build slow computers or weak audio!

Yikes, smart questions come to mind after posting it seems....

Are you wanting a model electronically mocked up to see if what you have is good in your application? If so, give me a little time- I got my hands full with real life(tm) issues but can get something posted definitely by this time tomorrow.

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Life is too short to build slow computers or weak audio!

so what do you think wolfox? that prefab box or a custom box?

At this point, whichever is most cost-effective for you and/or what your patience will allows. The prefab one you pointed out is not a bad match at all, all you have to do is wait for it to ship. Your buddy that builds may be able to offer far better handiwork if he can indeed model and then build a box totally tuned for the speaker, your vehicle and musical tastes. And then you merely have to wait for him to do it for you.

Personally, I totally enjoy building my own and it is worth the blood, sweat and gears. :D That call is entirely up to you. Feel it out with your buddy if he has some passing knowledge of WinISD, etc...

Metaljoey:
If you're still on the line with us, there is nothing wrong with the setup you have, even with a common shared port with the dimensions you listed. I modeled it out to 1000 watts, drivers wired to 2 ohms. Looks good - a very FLAT response curve and the tuning at 34Hz is spot on in your knee-bend. What can I say - DO IT. DO IT PROUDLY. :D

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Life is too short to build slow computers or weak audio!

well i can get that prefab for 65-70 or i can go with that custom box for 80 (w/o carpet). i honestly dont know which option should i choose :[.

with that prefab, will it be crazy loud? i have a mrp-m500 to power the sub.

difference between prefabs and custom enclosures.

prefabs are constructed with the cheapest quality glues and staples. The enclosures never last. Seams blow and carpet peels.

A properly constructed enclosure will last a lifetime.

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Custom Enclosure Design

aznboi3644 wrote:

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difference between prefabs and custom enclosures.

prefabs are constructed with the cheapest quality glues and staples. The enclosures never last. Seams blow and carpet peels.

A properly constructed enclosure will last a lifetime.

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+1

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Life is too short to build slow computers or weak audio!

where should it be tuned for maximum spl?

thanks wolfox!! you set my worries to rest! 

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Before you see the light, you must die!!

tuning is dependent on the vehicle...every vehicle peaks at a different frequency.

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Custom Enclosure Design

am i fine with the mrp-m500? or should i upgrade to a bigger amp?

wolfox wrote:

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"... but then does unload steeply after 20 Hz. so be sure that your amp's low freq. filter is operational and you will have no worries.

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It looks like it begins to plummet at around 30-35 hz, not 20. Am I just completely lost and causing more trouble than an adequate reply is worth? If so, no problem. I'm just trying to understand what it is I think I'm seeing.

Thnx!!