Decided to go ported, and more questions.... (1 Viewer)

[Justin Ward]

I have decided to build a ported enclosure for the Tempest. Instead of buying port kits, is it ok to use PVC tubing? This will be a passive model, how should I wire the sub to a 120 watt minisystem(impedance must be at or above 6 ohms).
Thank you all for putting up with my questions.

 

[Justin Ward]

also, what do you guys think of the SBB4 design for a Tempest enclosure?

 

[Jon Torres]

A 6" PVC pipe should be fine. Is that 120 watts RMS? You could probably hook it up w/ one channel to each voice coil giving it an 8 ohm load. SBB4 design, probably best to use the search function.

 

[Justin Ward]

If i use PVC pipe will I change the size of the hole in the cabinet? So about 6 inches of 3 inch PVC will be acceptable?

 

[Justin Ward]

That is 60 watts x 2 per channel RMS into 6 ohms at 10%THD. So it is probably around 50 watts x 2 RMS into 8 ohms.

 

[Dustin B]

A single 3" straight port will severely limit a Tempest. A single 4" flared port is the absolute minimum. With straight ports a pair of 4" diameter ports would be ok, as would a single 6" diameter port.

Wiring each channel of the minisystem to one of the voice coils should work. But I wouldn't be surprised if it was actually less than 20Wx2 at 8ohms. Those minisystems aren't up to much. The damping factor will also likely be horrible which isn't good when you are driving a subwoofer.

Should work though until you can afford a better amp. You could also check pawn shops for a really cheap but decent receiver that you could then use to power the Tempest with.

 

[Dan Hine]

So about 6 inches of 3 inch PVC will be acceptable?

What size box and what tuning freq. are you looking at? Also, keep in mind that while a certain size port may tune a box properly, the driver used may not work well with it. For a Tempest, I would say a 6" long 3" diameter port will not be enough.
Edit:
I see Dustin beat me to it. Are you ever not on the forum, Dustin?
Also, Justin, how do you intend to use the mini-system? Is it one of those "bi-amp" deals with the separate amp section for both highs and lows, or does it have an Aux input that you are going to be using?

 

[Dustin B]

Heh, pretty much no. But hopefully not for much longer. Have a promising job interview on Tuesday. Keeping my fingers crossed

 

[Justin Ward]

The minisystem is not biamp compatible but it has an aux input. This would only be temporary until I bought a plate amp or a higher quality external amp. Also wouldn't 40 watts total be enough to drive the Tempest quite loud in small room(especcially with a ported design)? Basically with the ports all I need to know is: How do I modify the sbb4 design(from the Adire website)to take PVC but maintain similiar sonic performance.

 

[Michael R Price]

Justin, you will need larger diameter PVC ports to match the performance of flared ports. As a consequence of this, they'll have to be a bit longer. My recommendation would be to use a single 6" diameter port 24" long, which would be about right for the SBB4 alignment (190L tuned to 19Hz, I think). So you can rearrange the box dimensions to fit a 6" diameter port while maintaining the same volume.

40 watts will work fine. You'll be 6-10db under the potential of the Tempest. So, I'm not sure how loud you want it but you'll be in the 95-100db range with 40w, maybe more.

 

[Justin Ward]

oops, just noticed the SBB4 calls for (2)4 inch flared ports(not 3 inch) how will this change my design?

Do the plans for the SBB4(the pdf files from adireaudio) include all nescessary information or is there anything else I need to consider? I am starting a list of items needed to complete the project. Here is what I have so far:
MDF(not exactly sure how much)
Hardwood(4 inch lengths with 2 inch diameter).
Tempest(obviously)

Are there any other materials I need(remember this is a passive model)? Is there any reason not to start buying materials for, and building the enclosure without having bought the actual driver? I only ask because after this paycheck(hard earned cash from Dairy Queen!) I will not have enough money to buy the Tempest but I will have more than enough to start buying the other materials.

One more thing. If I went with a 24 inch long piece of PVC, the PVC would almost be touching the top of the enclosure on the inside, will have any effect on the sound?




Sorry for all the questions, this is my first DIY project and I want it to turn out well. Thank you all.

 

[ChristopherD]

Justin,
Follow the Adire plans EXACTLY (flared ports, etc), that way you'll know you're getting the most out of your driver for that particular design. In other words: imagine reading later what you COULD have had if... You can upgrade the amp section later (which is a super idea since you're on a budget), but if you skimp in the planning/execution of the design, you will have issues that more money (DQ promotion?) CAN'T rectify. I am building a Tempest soon, so keep me updated on your thought processes. Just my $0.02, but please think twice, build once.
Best wishes on your endeavor and FAT respect for putting your hard-earned burgerflippin' dollars into a DIY project.
Do your best!!

Chris

 

[Casey H]

Dustin,
You can't take a new job! Your input is greatly appreciated here at the forum!
Casey

 

[Dustin B]

Take a new job, it's getting my first real job as I just graduated in May :p)
Bonus will be I'll have money to spend if I get the job, so I'll eventually get a chance to build a screen (mmmm, FPTV), some hush boxes and some more speakers
Stupid technology sector deciding to take a nose dive when I graduate :frowning:

 

[Justin Ward]

So, other than MDF, PVC and hardwood legs what else do I need to buy(with the exception of the driver). How much MDF do I need to buy?

 

[Jon Torres]

You'll probably need screws, glue, closed cell weather stripping (not sure if tempest includes this), and a terminal cup. Oh.. and maybe some speaker wire if you don't have any.

 

[Dustin B]

Paint, fabric for the sock, mounting hardware for the driver(t-nuts and bolts), silicon.

 

[Justin Ward]

Fabric for the sock? Is that only if I build a Sonotube sub? I am getting paid today so I hope to start buying materials tomorrow. I can probably find 3/4 MDF at the local Central Supplies. How much will I need for this project?

Also what is a terminal cup? I think it is the device that connects speaker wire to the voice coil, correct me if I am wrong. Since I am plugging in one channel of the minisystem into each coil how many will I need? Will I be able to find these at radioshack?

I still have a bunch of 16 gauge wire left over from when I wired all my speakers to the receiver, is this of adequate size or should I buy something larger?

Assuming I went with dual ports(the Tempest calls for 2 4-inch flared ports) what size PVC would I need to match this performance?

And one last question(I promise!)what kind of paint should I use(is normal black spraypaint ok)? And assuming that later I wanted to put a vinyl finish on it(black ash)would it be more difficult if I waited a while to do this?

Thank you guys so much for putting up with my questions, I am really fired up about this project.

 

[Dustin B]

Sock is ususally used for a sonotube. Although some people have just painted the tube, one guy is trying to veneer the tube and another guy even managed to tile the tube. A sock could be used on a box sub as well.

MDF comes in 4'x8' or 4'x4' sheets. So how much you will need depends on how thick you make the end caps and if you have a base plate or not.

Terminal cup is what we call the plastic cup you mount to your enclosure that contains binding posts. They make dual terminal cups with two sets of binding posts. This is what you'll want for your desired hook up method. You could also just get two sets of binding posts like I used on the Twins (see my website).

Don't forget primer. MDF really soaks up paint. You'll want to get a really good primer coat (ie several coats of primer will need to be applied) on the MDF before you attempt to paint it. Just ask the guy at the paint shop about a good primer for MDF and what paints will work well with that primer base coat.

If you want to laminate something to the MDF painting it first is a bad idea. You don't have to, but you should sand all the way back to bare mdf, which could be tough with how it will soak up the primer.

Two straight 4" ports shouldn't be a problem.

 

[Justin Ward]

How long should those 4inch pipes be Dustin? I have about $85 Canadian left over this paycheck(after buying wall mounts for my Titans, paying back a loan to my parents and saving $75 for a long term purchase(street and trail motorcycle)). So, with the exception of the driver, will I be able to buy of the other materials with this amount of money? I suppose I will start buying the MDF and PVC so I can start doing the more time consuming parts of the ocnstruction first. Also, where can I buy terminal cups at(ones with 2 sets of binding posts)?