budget sub choices - Page 2

I already ordered the ep4000 because I don't want to have to upgrade in the future when we are powering multiple subs in our future basement. The problem with the pro version is that I don't see where it tells you about the noise coming from the ports when you adjust the port diameter. In the beta version, it gives you something called "vent mach". I googled it and it looks like you are supposed to stay under 0.045 to avoid port noise. I seem to be overlooking this type of feature in the pro version.

As for the high pass filter adapters you commented on, I'm not going for perfection really, I'm just trying to avoid destroying the drivers. I'm not sure if those will do the trick or not... I saw 20hz ones, but I would like to go 1 or 2 hz lower if I can. I might just have to keep the volume low until I can afford a proper high-pass filter maybe.

Ok I found the graph for rear port air velocity. I will be putting it on the front though. So how many feat per second should I be shooting for? Right now it peaks about 1hz below my targeted frequency. If I go with a 4 inch diameter port, 6.84 in length, and .732 end correction it maxes at about 15ft/sec.

So whats end correction? Is that for when you used a flare port? So If I used a single sided flared port, I would want to cut .732in from the length if I'm correct on my guessing.

Oh that's with 2 ports btw. If I use one port it says to go with a 4 inch diameter, and only 2 inches long. Weird. If I use winisd beta I get some huge numbers, something like 6 inch diameter and 18 inches long or something like that. This software is kind of frustrating.

Ok I think my indecisiveness has drove me crazy :P

I'm feeling really uncertain about my box dimensions and port sizes due to my noobage. If someone with some building experience has the spare time, could they run the dayton reference hf 15" sub through some software and recommend the dimensions and port sizes for me? I know I'm asking a lot, but could you do them ported and sealed?

Here are my goals:

Mostly home theater and games, so I would like it to get pretty low. Size is not an issue, except for the 4ft tall factor. I can make up an over sized enclosure in width and depth.

The reason I'm not sure on ported or sealed is because I don't know if I'm going to be able to afford a high-pass filter yet (don't even know what to even consider for that yet). If I can't afford the filter, I will be doing 2 sealed ones. I'm not in any rush, I don't want to come off as pushy. I won't even have the subs for about 2 weeks any way.

I want to thank you guys for all of the time that you've already spent on me :thumbsup:

Ok, I got an email from someone at parts-express with some recommendations:

"The RSS390HF-4 likes large boxes.

A box calculator will tell you that a 2.3 cu. ft. well-stuffed sealed box will yield a "perfect" .707 Qtc alignment, but we actually recommend 4-4.5 cu. ft. for these. A box 4.5 cu. ft. will yield a modeled Qtc of .575 and F3 point of 38 Hz, which is very good for a sealed sub.

For even more dramatic low-end response, a 7 cu. ft. box with a 6" diameter port 30" long will give you a tuning frequency of 19 Hz and an F3 of 21 Hz. 30" is, I realize, a very long port. Just make it as long as you can. 15" long will give you a tuning frequency of 25 Hz and an F3 of 23 Hz.

Thanks for choosing Parts Express! Please don't hesitate to contact us if we can be of further assistance."


So if I go with the a 9ft^3 dual driver sealed box, will it play well in the 20 - 30 hz range? I'm also wondering if I can get away without a high pass filter with this sealed setup. I would have to brace it well, and I'm assuming I wouldn't have to stuff it with anything since the box is already pretty big, and the qtc is already pretty low. Am I supposed to line the walls with anything?

I'm not too sure about the ported option, because the depth of the box would have to be atleast 36 inches, so it would look kind of weird and short with a dual enclosure.

So my scattered questions on the sealed box basically are:

1) Lining the box with something?
2) 20 - 30hz range?
3) high pass filter?
4) no filling?

After these questions are all cleared up, I'm ready to start building!

Ok so I compared what the guy from parts-express told me to what I get in winisd pro, and I get very different results.

A sealed 4.5ft^3 box gives me a qtc of .753, and an fsc (same as f3?) of 33.11hz.

His suggestion of a ported box of 7ft^3 and a 6 inch diameter 30" long port is also different than mine. I get 17.57hz

I'm not saying he is wrong, it's just adding to the confusion.

With the sealed box 4.5ft^3 on the cone excursion graph, it reaches 14mm at 36hz. On max power at 20hz it says around 240. Seems kind of low. I don't think this is a good box to build.

I'm using this file in winisd pro:

http://www.hometheatershack.com/foru...idelity-15.wdr

Ok, I finally figured it out! I'm going to return the ep4000 to amazon ($32 shipping) and get a bash300. The reason is, I'm only going with one ported enclosure now. The ep4000 would be fine, except I'd have to spend another $100 on a high-pass filter. The bash300 has a 17hz filter if I understand correctly. So I have to pay $32 for the exchange, but in the end I end up with around $275 back when I don't have to buy a high-pass filter. Here's how I modeled it:

10ft^3 external enclosure, h 30" x w 24" x d 24". After taking the displacement of the bracing, 2 x 4"D x 17" L ports, and the 3/4" mdf into consideration, I have an internal volume of 7.68ft^3.

This allows me a tuning of 20.75hz. I had hoped to go lower, but the box would be huge, and I would run into cone excursion problems. The transfer function magnitude graph stays above the 0db line for some reason until 200hz. I'm guessing that isn't a problem. For max power 300watts, it gets down to almost 17hz before there is a problem. The highest port noise gets to is about 78ft per second at around 19hz. So there might be some port noise. What should I be shooting for?

The reason I'm going with 17" ports is because that's how long they sell them on parts-express. I'll attach some screens in a little bit.

Here are the pictures of how I'm going to build it. Thanks for all of your patience, I have this pretty much figured out now. I'm on my xp computer right now, and couldn't figure out how to resize them without making them look like crap, sorry for hogging your bandwidth.

Yea that looks much better, and half the port noise. Do I just make the slot port out of mdf? I never considered making one, because of how easy it would be to just make round ports out of pvc pipe.

Thanks for the advice. Once I get the refund for the ep4000 and build this thing, I'll post results.

I finished the project a while ago, but I totally forgot about the pics. First off, this totally exceeded our expectations. We had a little trouble with one of the ports, we messed up one of the parts-express flares, and attempted to bend one our selves, many times... we took the best result, which had slightly cave in just before the flare. When running a test tone below 18 hz, you can hear the port noise from the messed up port. We decided to leave it as is, because as hard as we have tried, you can't hear it during a really low frequency movie scene, and you definitely don't hear it during music.

We came from a htib to this setup, the clarity and lack of distortion is amazing to us at high volume, even though we are aware we are using entry level polk audio, yamaha, and sony equipment. You can feel the dayton subwoofer shake the floor in scenes with below 25hz bass, and our only sound complaint is the noise that comes from the house and windows

Didn't start taking pics until we were half done. We didn't use clamps, just a step bit for the screws and liquid nails. Then bondo to fix up the seams and cover in the screw holes.



My gf and partner in construction sitting in the box, doesn't she look happy?



Bracing



Here it is with both of the parts-express ports. I messed up the right port. I had used a dremmel on the inside of the pvc pipe to make it thin enough to match the flares, then attached them with pvc glue. On the second time around I was rushing a little and dug a little too deep, so the glue would make a good hold. I wish part-express sold elbows, or I would have laid down the $50 for their overpriced tubing.



And the finished project.



Thanks everyone for making our first diy project possible, our next speaker project is for the jeep. Once that's done, we'll have to find another reason to build, I think we might have the itch...

http://www.avsforum.com/t/1421258/diy-suggestions-for-jeep