sonix7

Here ya go guys. I am working a new fiberglass enclosure for my FD, this is going to be competition orientated. I am running a Soundstream T4-12 Tarantula 1200 RMS, 1.2 farad cap, off a 6 channel D'Artagnan movie amplifier. I decided to get as much room as possible out of the trunk and try and still make it lighter than wood. The speaker weighs 38lbs by itself. I went ahead and framed out the enclosure shape and then I am in the process of wrapping it with a special fleece and then I plan to fiberglass it. It fits perfectly nice and snug. Oh yeah I did this in 4 and half hours. I will finish it off later. the top will be completely fiberglassed and shaped to the edge of the trunk. It may have a CF top and blue neon accents. I may even do some special blue kevlar to match the soundstream blue. Anyway LMK what you guys think so far.

sonix7

sonix7

HKS7fanatic

this is gonna look sweet man. thats a heavy *** sub. are you going to build more supports for it? i imagine u might need it if ur sub weights 38 lbs. either way its going to look awesome. ur products are awesome.

chinaman

Looks very nice and heavy! Why did'nt you use mdf instead of that saw dust looking board?

sonix7

Thanx guys. Yeah I am adding more braces for the sub. I had a whole sheet of MDF, that is what I used. Its 1/2 inch thick so I could alieviate the heaviness. Yeah It will be nice, I have a bunch of stuff yet to do. I figured I would show what I am capable of. All you will see on top is a nice contoured surface probably in CF, the driver, amp rack lined with blue CF(lit up with blue neon accents) and that port. The sub I have is ideal for a 2.5 cubic foot enclosure with that port. its tuned to 34 hz when done. I will post more pics tommorrow.

purerx7

iTrader: (61)

looks good, be carefull, if you have a rear window wiper, you have that bump in the lower left corner it needs to clear.

RE-Amemiya

That looks really good so far...i love the idea of the blue cf with neon accents.

sonix7

Awesome advice, yes he is right. That motor sticks out substantially. That is why the top will be fiberglassed and smoothed. There will be a small indentation like a coin tray to clear that in the top. Its just like the one you can get from Japan. I may put a badge there so it doesn't just look like a coin tray. The Blue kevlar hybrid fabric is sick. I guarantee this is going to win something. I didn't just drop $3000 + to have it suck. I already had it hooked up in the last shitty design I was so rushed to make. It is overwhelming, and that is without the cap, the BX-12 bass restoration unit, and tuned. I am going to finish the fiberglass right now. We have a hot day coming so curing times outside should be perfect. Stay tuned.

DamonB

If that tube is a port you don't want it crammed into the corner like that. Space it a minimum of it's diameter from any obstacle. Ideally more than that.

sonix7

DamonB I was waiting for you to chime in. Can you suggest where would be a better place for the port? I just tried to get it in a logical place. Can you explain the min. diameter theory. I am always open to more knowledgable suggestions to improve the set-up. I wish I knew everything, but I don't. Plus I have been out of the car audio loop for a few years. Just catching up. Thanx

DamonB

The port is going to have pressure flowing through it. If the port is too small in diameter compared to the speaker you can get port noises or "chuffing" as the port then becomes a restriction. You see (hear!) this happen very often! This throws the tuning of the enclosure off somewhat but worse the port will make funny noises at higher volume levels. The bigger your woofer gets the bigger in diameter your port needs to be. For high power, high excursion 12" woofers I use at minimum a 4" diameter port.

The length of the port is of course directly determined by the frequency the enclosure is tuned to and the diameter of the port. As port diameter increases then port length also has to increase to maintain the same tuning frequency. Sometimes this leaves you with the problem of wanting a larger port diameter but the port is so long it won't fit in the enclosure easily (or at all!) without being close to something. At that point don't be afraid to bend the port so it's no longer straight (very easy to do if you're using pvc pipe and plumbing fittings). It's much more preferable to bend the port then to instead go with a too small diameter.

Since pressure is flowing through the port at all times we want the port to represent the least restriction possible. Proper diameter is important and so is placement. With the port stuck right up against the enclosure sides or back the port again becomes restrictuve because it makes it harder for air to smoothly enter the port from the inside. For this same reason port tubes flared at both ends work great; they're more efficient at getting air through the port (flared ends don't change port length. Just add the flares onto calculated length of the port tube). The general rule of thumb is to at minimum maintain one port diameter of empty space around the ends and sides of the port opening inside the enclosure, but more is always better.

sonix7

Very nice. I respect your audiophile knowledge quite a bit. Now I got that measurement for that port in the pics from the specs of the driver I am running. Based on a 2.5 cubic foot box, which is close to what I estimate this box to be when completed, they said make the port that diameter and length to be tuned to 32hz. Now I am interested in what you have stated, how would be the best way for me to determine the length and diameter of the best port possible. Could you use two ports instead of one to achieve the right sound? My old box that had very similar dimensions used this same port and it rocked. I did not notice any of the symptoms you described, but can't remember pushing it that hard. Thanx DamonB

DamonB

"They" I assume is the speaker manufacturer, right? Because they're the one that counts. Don't just roughly estimate the enclosure volume though, try and be close. With really funky shapes like yours which make it tough to figure with a ruler you can measure with styrofoam packing peanuts. Fill the enclosure with peanuts and when full dump the peanuts out into a pile and measure them into a convenient container to determine volume.

The specs of the woofer are going to dictate the enclosure size and tuning frequency. Once you know those two there are simple formulas that say if the port is x diameter it needs to be y long in order to tune the enclosure to that frequency. There's really no "perfect" port; they all work. You just don't want to go too small. My preference for a 12" woofer is at least a 4" diameter port.

Yes but the box is still tuned to the same frequency, you just reach it by using two (or more) ports instead of a single one. You might do this if you don't have the physical space on the baffle to fit a single big port, so you use a couple smaller ones. No difference in sound quality.

The port is a tunnel and the woofer is going to move a given volume of air through it. If the port is too small the air velocity in the port has to be high and that can lead to port chuffing. The larger the port the lower the velocity of air inside the port and the closer you come to a perfect model of pressure rather than velocity.

If you're using the same woofer and enclosure size you had before there's nothing wrong with using the same exact port as well because you haven't done anything to re-tune the enclosure, you've just made it look different. If you've changed the woofer and/or the size of the enclosure the tuning frequency (port size) needs to be computed again.

There are tons of freeware programs out there that will figure all this stuff; WinISD is one I use often but there are many others. You will need all the specs (Thiele/Small parameters) of the woofer in order to compute anything. You don't need to know what the numbers mean but you do need them in order to use the software. Keep in mind that in a car the small interior space boosts the bass frequencies so the rolloff the software shows will in reality extend considerably lower when placed in the small car interior.

sonix7

thanx. very comprehensive answer. I did obtain the specs from Soundstream, I had been thinking of a way to figure the volume of the enclosure. Shipping peanuts is just an awesome idea. I have tons of it downstairs. My friend suggested water, but I cringed on the idea of filling up the box with water. Yes the box before was same size minus about a 1/2 Cft. so I will definately measure it accurately this time. In the old box the port was about 3 inches from the driver on the right side looking in from the trunk. I will brace it and set it up in the same configuration. Yeah so if the port is not big enough then the air will have to go through the cone of the driver and thats what causes the condition you spoke about right? or maybe I missed that one. However thanx for the insight and help. wish me luck.

rynberg

I hope you are planning on adding a lot of bracing. A high excursion driver like that will flex the crap out of a big enclosure like that, especially since it is only 1/2" MDF. You should definitely consider adding a damping compound or material to the interior of the enclosure.

Personally, I think one 4" port is a minimum for something like that... Although I'm surprised a port of that size and length would result in a 32 Hz tuning...I would think it would be well down in the 20s.

DamonB

The woofer displaces a volume of air that can be computed just like engine displacement. The diameter of the cone X cone extension = displacement. The louder you play the woofer the further the cone will extend so higher loudness levels require greater displacement of air. The woofer will continue to play louder as power in increased until 1) the voice coil burns up because it can't handle the current or 2) the woofer reaches it's mechanical limit of extension.

In a ported enclosure everytime the woofer moves air is also passing through the port. The woofer is moving a given amount of air and that amount must also travel through the port. If we have a small port then the air must travel through it at a much higher velocity in order to get the same volume of air through in a given amount of time compared to a large port. With too small ports you can literally hear noises that sound like someone blowing through a pipe because that is what is happening.

At the same time a too small port will become a restriction as the air cannot move freely through it, so it doesn't. A restriction in the port will also limit cone motion of the driver. This can cause it to breakup (usually) or just plain lose output and frequency extension. You don't want that. You want the port big enough that no matter what the woofer doesn't have to work hard to move air through it, you just want it to happen. At low power levels it's rarely a problem since not much air is being moved but at high power levels with woofers capable of large displacement it can be a real problem.

sonix7

yes I am adding a ton more bracing and I plan on using either liquid roadkill or cascade v-block sound dampening sauce on the inside. I have so much sound dampening material going in the car in should be a recording booth. So the consensus is at least a 4" in diameter port. Wow. the speaker is DVC, long throw spl driver 900 RMS - 2400 burst rating.
http://www.soundstream.com/subwoofers-tarantula.htm here is a link to the specs. It is the T4-12 DamonB and Rynberg maybe you guys could look at the specs at tell me what you think. It says 2.2 Cft vented. It gives the aeroport demensions but I have a different spec sheet that has port size and thats where I got that port from. Thanx for the help gentlemen.

sonix7

ah yes physics! air movement and all of that. I understand. I also understand the whistling concept and the restriction of air movement. Damn, sometimes I wish I was much smarter. More education I guess huh? Wish I had time and money for that. Instead I am building huge speaker boxes and messing with carbon fiber. Thanx guys

DamonB

^ Use what the manufacturer says. Typically they've done extensive modeling with small auto interiors so 99 times out of 100 what they recommend it great. If you want to split hairs and go nuts you can often eke out a little more but I wouldn't even bother.

Another trick I use:

Often when experimenting you want to try different enclosure volumes and it's a huge pain in the *** to keep building enclosures even if you're just banging together ugly test boxes. Instead build one test enclosure but build it too big. Then you can adjust the actual enclosure volume by putting things like closed cell foam blocks or even bricks and lumber scraps inside. Once everything is sounding like you wish you then build the "real" enclosure with the internal volume your experiment said you like best. If you're doing this for a car keep in mind you have to listen to it inside the car when experimenting.

DamonB

When I look at what you have mocked up I see a hell of a lot more than 2.2 cubic feet. My enclosure is positively tiny compared to that and it's nearly three quarters of a cubic foot. You must have about 4 cubic feet right now, even allowing for the amp rack.

John64

Why all the MDF? You could have made the entire base out of fiberglass with MDF sides. The enclosure would be half the weight it is now and completely contour to the base of the car.

It's in my FB, but you get the idea.

sonix7

Looks good! Basically as Rynberg said, I need more support. The woofer I have is no joke. It will rattle anything loose. I am also vacuum bagging this and also going to do two layers of fleece with the inside lined with chopped strands and resin. I make a sauce with the resin and the chopped strands and black pigment. It is liquid fiberglass. Works awesome. It won't come apart!!! also I measured the port and it is a 4 inch port. Its actually 4 x 7 inches long. I am going to brace it up a couple of inches to the right of the speaker. I will post pics soon.

HardHitter

iTrader: (4)

sonix7, I am doing basically the same exact install, (check my thread in the forums here) and I agree with John, there is no need for all that wood but we are doing different setups and I'm sure it'll turn out the way you want it, just a little different than some might do.

I'm doing mine for a 10W7 so I know that both of our enclosures are going to have to be strong enough to withstand the amount of pressure these subs will be making not to mention the weight. You'res will be a little easier since it's straight up and down, but mine is at an angle, so I'm sorta of worried about it not supporting the weight of the sub. We will see though, I'm going to be doing 6-7 lays of fiberglass for strength.

Can't wait to see your enclosure plan looks great!

sonix7

Thanx HH, I think we should make this the official fiberglass enclosure thread. I did check yours out and am very hyped to see what you guys are doing. Yeah I just wanted a good frame. I am using less fiberglass for that reason. This should be emensly strong. Here are some pics from todays step. Covered ready for resin. I moved the port right next to the speaker and in a better location for flow. I also added more braces, it holds the speaker no sweat. Next is the messy part, I am bringing this in to my paint booth resin room and may make a vacuum bag to go around it. That way all I do is add resin and bag it and wait til tommorrow. I am thinking the vac bagging might be counter productive because I want this shape not every contour there can be. Thats where it works with laminating CF. Check you guys on Monday!!