Have space for 27w x 33d x 20h box - what to do????

[dan_whip]

Hey all - diy novice here. I'm going to start my sub build soon, but need quite a bit of help on the design. Here's a quick rundown on the basics:

Room - approx 2400ft^3

Use - 95% HT/TV - rarely game or play music

Box size limit - the absolute max is 27x33x20. I would put me in the advanced category as far as woodworking goes, and I have access to any tools I may need, so no problem there.

Amp - Leaning towards an EP2500. I may in the future decide to do a second sub, so it would be nice to not have to buy a second amp.

Driver - wide open here. Budget is about $200 - $250.

Major Limitation - Here's the problem. I own a townhouse, so 2 walls are shared. That means I can never play anywhere near reference levels. I am hoping to move into a house in the next couple years, so I want something that that will play clean at low levels for now, but will be very capable once I move.

So my question is, what would be a good driver/enclosure combination given the size considerations? Any thoughts and ideas would be a huge help - I'm hoping to start cutting wood next weekend. Thanks in advance.

[Mike P.]

A box 27x33x20 will give about 8.5 cu.ft. internal volume. The best you can do in that size and price range would be a Mach 5 Audio IXL-15.2.2 for $220 shipped. A round port 8 inch diameter and 54 inches long would deal with the port air speed. Or a slot port with the same surface area and same length. The net volume of the box would be about 7 cu.ft. after all deductions. SPL would be 114db down to 17 hz, plus room gain, with 1000 watts input power.

[dan_whip]

How would the Mach 5 compare to the tempest-x in the same size enclosure? Perhaps I've read wrong, but from what I understand the tempest is the better performer? I don't really remember reading too much about the IXL, so I could be way off.

I know the tempest is on backorder right now, but I don't mind waiting a few weeks if it would be a better option. As long as I decide on the driver, I can build the box next week and do the cutouts when the driver comes in.

Thanks much for the quick reply.

[salvasol]

dan_whip wrote:

I know the tempest is on backorder right now, but I don't mind waiting a few weeks if it would be a better option...

If I recall correctly, Tempest X will be available 02/09 (I asked before I got my Mach5) ...

Mach5 IXL 15.2.2 is a good driver (you can see my build here ), I'm happy with the results

[Mike P.]

I'm hoping to start cutting wood next weekend

The Mach 5 was mentioned due to the Tempest-X not being available until Feb. 09. Within the box size you stated the IXL-15 would have more output between 22 hz and 14 hz while the Tempest-X would have more output above 22 hz. The Tempest-X needs a bigger cabinet then the limit you stated for it to outperform the IXL-15 in the low end.

[dan_whip]

Ok, so I resized the easy button end table design to fit my size requirements, and came up with this:


I know - it's a terrible excel drawing, but I have no idea how sketchup works. Hopefully you get the idea. This would be the top view - just imagine it 20" deep.

But I'm confused as to how to calculate the internal volume and port size. Hopefully someone with more knowledge could let me know if these dimensions would work for the Mach 5 15", or if I need to adjust anything.

Thanks again for all the help.

[Mike P.]

The net volume of the box (from the numbers shown and assuming a 18.5 inch internal depth) is 5.6 cu. ft. The port is 2.5" x 18.5" and has an effective length of 74" and will tune the box to 16.7 hz. The problem with this is the first port resonance is too low at 91.5 hz. The solution would be make the port length 60 inches long. The net volume is now 5.9 cu.ft and the box is tuned to 18 hz and the first port resonance is 112 hz which will do. The port length is shown by the red line running through the middle of the port.

Between your Excel drawing and my Paint abilities, ya think we should start a business?

[dan_whip]

Thanks Mike!!! That seems like a really simple build. But because I like to overthink things, how would a CSS SDX15 go with this design? From my intense 15 minutes reading about T/S parameters, the SDX looks really good. Any thoughts on this driver?

PS. I'm jealous of your paint skills - I tried to draw a speaker and it turned out looking like a sombrero.

[Mike P.]

For about $50 more you're getting a sub with the benefits XBL2. Both subs have about the same expected SPL output.

[dan_whip]

What are the benefits of the XBL2? I'm sure I'm reading WinISD wrong, but it looks like the Mach5 has just a 2db loss between 80hz and 18hz, while the CSS has a 6db loss. Plus, the Mach5 has more output between 21hz and 14hz. Am I missing something?

[dan_whip]

(yes, I had a bit of insomnia last night)

To measure the length of the port, do you basically use the center point of the port? If my math is correct, this drawing gives me a 60" port.

Also, should I use any polyfill, or do I just line everything with insulation?

[Mike P.]

Output wise both subs are within a couple of db as shown in the graph in post #9. The advantage of XBL2 is lower distortion. The effective length of the port is determined by the length of the center line. All corners in the port need to be rounded over to ensure smooth air flow. Lining the walls of a ported enclosure is debatable. Some say yes, some say no. Personally I line the walls with egg crate foam.

[dan_whip]

Here's a quick SketchUp of my hopefully final design:


Are there any design flaws I would need to change before I start cutting? All internal edges will be rounded, plus the port opening will be rounded. I don't know how to round edges in SketchUp yet, but they are in the plan.

[Mike P.]

Looks good to go. Post some build pics as you go along.

[dan_whip]

Thanks Mike!! I take it you don't sleep much either?

I should be able to start building this by Friday at the latest, so I'll dig out the camera and get some pics for ya. Now I just need to decide on the finish. Some sort of veneer......luckily I work next door to a Woodcraft store, so I'll sneak over there today to get inspired. Maple burl? Zebrawood? Or maybe a lacewood? Might as well go all out, right?

[Mike P.]

I have always built the cabinet, installed the sub and tested it out before I've done any finishing. I like to verify the end result before any expense is put in on veneering. Just a thought.

[Ricci]

I posted this over on AVS for the OP in answer to a question posted there. I originally recommended a sealed IXL18 as it would be easy, the OP lives in a townhome so he doesn't need to crack the earth right now and I figure once he moves somewhere else he could build a vented enclosure for the 18" and really let it do it's thing. Figured I may as well cross post it here. I would get the SDX over the Mach5 for the reasons stated below.



Actually the SDX should have more output everywhere over the IXL15. It should have more headroom and a better inductance. In theory the SDX will take 1800w before it exceeds excursion above 16.5hz in that cab. The IXL15 will only take an estimated 1100w. I'd go with the SDX if you do go vented 15". A sealed IXL 18 would have more output in the upper bass above 35hz and in the really deep bass below about 13hz. The vented SDX would have more output 14-30hz. Your port will compress a bit at the highest output levels so the advantage won't be quite as good as on paper, but still there nontheless.

One option if you could squeeze the driver budget to $310 would be to get a pair of Mach5 MJ18-M's and put one on each end of the cabinet in a dual opposed sealed config. With your 20" dimension it would be tight but not hard to get them in. The vented SDX would still have an theoretical advantage 14-30hz but with 2 18's taking the power instead of just the 1 15" and all of the added cone area they would be really powerful above 25hz for music and be under much less stress than the one 15" due to both excursion and thermal heating. You wouldn't need a HPF either. You could let the electronics roll off. You would probably need to EQ the low end up though.

Just a thought.

[dan_whip]

Thanks Ricci. I just ordered the SDX15, so the big decision is done. I'll start working on the box this weekend, and hopefully have the driver here early next week so I can finish the cutout. Guitar Center has the EP2500 for under $300, so I'll probably get it from them unless there is a great deal somewhere else.

Now back to pondering the finish options. That zebrawood sure looks nice.....

[dan_whip]

So as I'm waiting for the weekend to get here, I've been trying to read a bit more about sub designs, specifically the ports. From what I understand, the important things to keep in mind are first port resonance and port speed. I want a higher first port resonance frequency and a port speed under 34 m/s, right?

In my original design with one port 2.5" x 18.5" x 60", the first port resonance was about 114 and the port speed was about 20.6 max. I toyed around with it a bit and came up with a design that uses 3 ports, each 2.25" x 5.5" x 50". This would give me a resonance of 137.5 and port speed of 25.7 peak.

Here's a SketchUp:


I'm wondering your thoughts on a 3 port design rather than a single port. Would I be able to block a port or two to change the tuning, or am I looking at this wrong?

[Mike P.]

Blocking a port or two will give you more low end extention at the expense of output higher up, plus higher port air speeds. That plus more friction with 3 ports compared to one. I personally don't see an advantage since the majority of program material is above 16 hz.

Green 3 ports - tuning 17.8 hz
Pink 2 ports - tuning 14.6 hz
Orange 1 port - tuning 10.3 hz

[a1161979]

Please make sure you you post build pictures and pictures of the Driver Sorry im a picture addict.

[dan_whip]

Hmmmmmmm..........



What to do, what to do.....

[Mike P.]

Maple Burl gets my vote!

[a1161979]

Mike P. wrote:

Maple Burl gets my vote!

Raw MDF or high gloss black Nothing else for a subwoofer