ar.com dimension question

[Bobhof]

I am building a modified ar.com speaker pair (you can see my design in this thread: Help with ar.com kit from madisound). One thing that has been bothering me is the internal dimensions of the schematic provided with the ar.com kit. The schematic can be downloaded here: http://www.madisound.com/pdf/arcomcabinet.pdf.

The cabinet measures 9.25" X 8.75" X 13" (L X W X H) and is made of .75" material.
When I convert to metric I get 235 X 222 X 330 (in mm) and 19mm material.
Subtracting the width of the walls: (235 - 38) X (222 - 38) X (330 - 38) = 197 X 184 X 292 = 10.6 liters. This is before subtracting port and driver volumes.

However, the site says the box is around 15 liters internal. Are my calculations wrong? I need to know this so I can calculate the volume of my own design properly.

Rob

[lousymusician]

I thought about building a pair myself and found the same thing, their dimensions don't add up. Even 15 l seems too small for a vented box. IIRC, the desgn mentions that the box could be increased to 20 l if size was not a concern. I thought 25 l (tuned slightly lower) would be even bettter

For use with a sub, I'd probably just build a sealed box in the 15 - 20 l range.

[Bobhof]

Nice idea; a sealed box would save me a lot of trouble. I will be using these with a sub (see this thread for a description of my current design: Help with ar.com kit from madisound) All this Vb Fb Qtc etc is giving me headaches. ISD online suggests a 17.5 L sealed box for this driver. Space is an issue though, so I can't go larger than 14 L and it's a shame to waste the ports I have purchased. If I am building a 14 L box, do you think it would be better ported or sealed?

[xstephanx]

in DIY we dont call it waste....

...we call it "planning ahead"


im madisound screwed up on quoted volume and cabinet sizes, it doesnt really matter, designing a woofer enclosure is not too hard a task with todays modern softerware.

the only thing id be worried about is that they screwed up here...where else could they have screwed up? crossovers are VERY sensitive and one decimal place can make a crossover next to useless.

BUT im sure the diyaudio forum could help you with modified crossovers if it turns out those ones are no good (though i suspect they are fine, the kit must have been assembled by a few people)

since you are crossing these to a sub, id say use the LARGEST sealed box you can allow, and enjoy.

[infinia]

Better to come to DIY for advice here before you press the "order button".
As someone else pointed, wouldn't trust their (are they Mad) crossovers after seeing their box design suggestions. Also seems to cost alot fot what you get. IMO Peerless midbass are pretty good but tweeters are better elsewhere. I guess all the monies in the crossover.

[Bobhof]

Thanks for the advice. Sealed would certainly be easier. Have been working so far with a 14 L enclosure but could go a bit larger if it will help a lot.

[Bobhof]

Originally posted by infinia
Better to come to DIY for advice here before you press the "order button".
As someone else pointed, wouldn't trust their (are they Mad) crossovers after seeing their box design suggestions. Also seems to cost alot fot what you get. IMO Peerless midbass are pretty good but tweeters are better elsewhere. I guess all the monies in the crossover.

I did a fair bit of reading before purchasing and the kit I bought does get very favourable reviews. I'm sure the crossovers will work well. I have heard that the tweeters are not so hot but it seemed a good place to start. Unfortunately, I will be unable to post an objective review once I have finished construction since I have nothing to compare these with: this is my current sound system: http://www.alteclansing.com/product_details.asp?pID=IM3