[eclein]

I have the DIY bug and want to build a speaker kit. I haven't decided which one yet but I would need to do prebuilt cabinets like the PE ones or Madisound. One of the kits I'm checking out calls for a .40 cubic foot cabinet and I can easily find .38 or .50 so which way do I go, slightly larger than spec or smaller than spec? So how critical is it to match cabinet size? What effect does a slightly larger or smaller size make??
 

[JRace]

If you get a larger then needed box you just fill it up to meet the ideal volume.

If your doing a ported design then it is important as it will affect the tunning.

Don't forget, everything that goes into the box will take up volume, so the drivers them self, the cross-over modules and the port.

I just finished a build using the .25 curved maple boxes and a full-range driver (CS125FR). Surprisingly well built box, and the removable baffle makes cutting the driver holes real easy. Like take to your father to do it right - kinda easy.

[Letitroll98]

I applaud your gumption to tackle DIY speakers.  Yes, speaker box volume is critical to the design as it interacts with the driver parameters no matter if vented or sealed box.  I would advise a long list of books and papers to read, but the easist is to either order a kit from Parts Express where they have figured out the parameters for you, or go on Speakerbuilder.com and read some tutorials there.  The math isn't complicated, but the art of making a speaker sing is.  The average hobiest goes through about a half dozen design builds before they get something they would let others listen to.  But the basics of enclosed box speaker design are facinating and worth the time to learn if you ever build anything or not.

[planet10]

As suggested already, get a bigger box and add something to decrease the volume.

The curved PE boxes are reasonable, not as good as a well done plywood box, but definitely worthwhile. The rectangular box needs work (10 litres of bracing wouldn't hurt). No experience with the Madisound boxes.

The FR125 works well in a 7 litre box, sealed or aperiodic (if you've ported it, try plugging the port with some open cel foam). I have a set of Jordan JX92 in my curved PE boxes.

Flat-pak boxes are also starting to become more available.

There are a wealth of proven diy designs, so many that the problem is picking one, i'm partial to FR myself -- and by far, IMHO, best bang for the buck if you are into a build at a reasonable budget (highly suggested for a 1st build). The best place to get a survey of the field is diyAudio.

dave

[eclein]

Thanks guys, that's just what I was looking for! I think the .5 curved PE cabinets lined with no Rez should be just right then. I was considering the rectangular ones to save some cash but would rather spend a bit more and start in the right direction.
Thanks for the link also. 

[JohnR]

What you should probably do is download Unibox and see what the effect of the different boxes is going to be.

[eclein]

Thanks John I'll check it out.

[sreten]

Hi,

Its been stated repeatedly you should reduce internal volume, whilst
you can do this is pointless for 0.38 vs 0.5. The extra volume of the
0.5 can always be used usefully by slight tweaking of the alignment.

Anyone decreasing fairly small box volumes is clueless.

Post details of the 0.4 alignment and driver and I'll tell you how
to use it it in 0.5, it will be "better", unless 0.4 is too big anyway.

rgds, sreten.

[Letitroll98]

Hi sreten, welcome aboard over here.

[JohnR]

What did Ed end up doing?

Which kit was it anyway?

[eclein]

The kit I think I'll try is the Fountek kit from Madisound in some PE .5 curved cherry cabinets. It's the 2 way with ribbon tweeter, gotta start saving for it after the holiday.

[pumpkinman]

The kit I think I'll try is the Fountek kit from Madisound in some PE .5 curved cherry cabinets. It's the 2 way with ribbon tweeter, gotta start saving for it after the holiday.

AE if you want some help let me know,we can do them on my workbench if you like
or I can travel down your way.........Bill

[eclein]

Thanks Bill, I'll let you know when I actually get everything together in a few months.

[JohnR]

The kit I think I'll try is the Fountek kit from Madisound in some PE .5 curved cherry cabinets. It's the 2 way with ribbon tweeter, gotta start saving for it after the holiday.

Oh, I have one of the woofers (FW168) for use in a sub-sat project.

Unibox seems to disagree with the Madisound model. Or I've done something silly. Madisound says 12 liters tuned to 54 Hz, with a port of 58mm diameter 120mm long. These aren't matching up for me, my model says i would need 180mm length to get that tuning 

On the FW168 page it says "Recommended box: 0.45 cubic foot with a 2" diameter vent by 7" long for an F3 of 50Hz." That works for me. Here's that curve (blue) and one with 0.5 cu ft (purple) tuned a bit lower:

[eclein]

John, Thanks for the info....My plan is to take .5 curved boxes and line with no rez, Install the drivers and try it sealed without a port first. I don't understand the numbers to perfectly honest but I figured start with .5 boxes add no rez, effectively bringing it closer to .45 and do it sealed. The kit page shows a ported box, but they did offer a kit that included cabinets and it was not ported, so I guess I'll try it without ports first and add them later if the sound really blows.
 Its my first attempt so I'm trying to make it as simplistic as I can, do you think the port is a "gotta have it" or will a sealed box sound ok??
I never heard any real difference in any of my speakers when I plugged up the port holes to experiment, some change but not drastic.
 Am I making a big mistake by not adding the ports right away??

[JohnR]

Well, with a sealed box your -3dB point will be 85 Hz, so you will need to use them with a sub in that case. If you were going to use a sub anyway, that would be the way to go. You could use a smaller box then as well.

[eclein]

I have and planned on using a sub so I should be ok. I'm still gonna use the PE
.5 cabinets unless thats dumb idea, is it?

[JohnR]

Hi, it should be fine - I should have mentioned that the main thing is that the baffle width doesn't change (much) as the crossover will be designed for a particular width.

[sreten]

Hi,

For the FW168

FWIW using Zaphs numbers : http://www.zaphaudio.com/6.5test/compare.html
Optimum sealed volume is around 0.15 cuft, and 0.5 cuft is 3 times bigger.
Vented is about 0.3cuft or more. 0.5 cuft tuned to 40Hz looks very good.

Quick modelling in WinISD, Unibox may be different.

The indications are due to box size you should use vented tuning, and 40Hz
tuning indicates to me very respectable stand-alone bass performance.

Sealed will be very close to critically damped (Q=0.5) so still workable.

rgds, sreten.