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Similost's Speaker Build - Watch this space for lots of laughs.

similost said:
Well.. just ran the idea of building out the back of the box a little bit to increase the size by the wife.... "....then why didn't you buy drivers that would work in that size?"


WAF is a drag....

:tears:
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My bet is you're going to be very pleased with them is the stock cabinets. Run what you have and if you're not happy then look at alternatives. I do like Dave's idea though...
 
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A little googling leads me to believe that filling the enclosure with damping material can effectively increase the box volume by 20%, which should put you at your target. I don't really know what I am talking about, but it would probably be another cheap variable to play with, without having to further modify your cabinets.

4.5 ft^3 * 1.2 = 5.4 ft^3
 
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OK... I got all the wood and blads and such I need to get this done (I love an excuse to buy more tools :D)

Anyway, They didn't have 6" PVS so I went with 3" PVC, and I'll put two ports in the rear. I could MAYBE get by with them in the front, but I'm already cutting out enough wood in the front baffle to weaken it more than I care..

So since I needed a 6" port at 5 and what ever inches long.. would I just shorten that length by half for each port, or would I need to do something different?
 
similost said:
So since I needed a 6" port at 5 and what ever inches long.. would I just shorten that length by half for each port, or would I need to do something different?
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You need to do something different. Don't ask me what but I know you do. :yes:
 
The problem is, two 3" diameter ports have only half the cross-sectional area that a 6" diameter port does.

6" diameter has a sectional area of 3*3*3.14= 28.26 sq.in.

3" diameter has a sectional area of 1.5*1.5*3.14= 7.065 sq.in

For two port tubes, area of each needs to be 14.13 sq.in. That translates to 4.24" in diameter.
 
DAMN! .. this crap just keeps getting more and more confusing...

So there is no way I can use 2 3" tubes then.. correct? In other words, I need to go back and get 4" tubes... and then how do I figure out how long I need them to be?

This math is WAY over my head.. I do understand your math for the sectional area, but I don't understand the math to figure out the length to cut them at.
 
You're gonna need Ray or somebody to tell you about length, if you go with 4" tubes. If you want to stay with 3-inch stock, you'll need four of 'em to equal the area.
 
similost said:
DAMN! .. this crap just keeps getting more and more confusing...

So there is no way I can use 2 3" tubes then.. correct? In other words, I need to go back and get 4" tubes... and then how do I figure out how long I need them to be?

This math is WAY over my head.. I do understand your math for the sectional area, but I don't understand the math to figure out the length to cut them at.
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It will cost you some money, but have you checked out these?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=268-354

You could start with it tuned for 30Hz, and shorten it from there. It looks like you cut the tube to length, and glue the flares on with PVC cement. You could use a more temporary adhesive to prototype with.

From the reviews:
"They have a website at http://www.psp-inc.com/tools.html that will calculate the total length of the ducted tuned port. The first number is without the flares attached & the second number is with the flares attached. The difference between the 2 numbers is the length of pipe you need to fit between the flares!"

This is an interesting thread. :yes:
 
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hhhhmm.. very interesting.. I like those. but damn.. That means after I told the wife I got all I need except little screws and stuff.. I'm done.. .now I gotta tell her I need to spend another $80.. .this project is getting very insanely expensive..

I just went and spent another $80 for a sort of decent router.. mine was pretty ancient and a real bitch to adjust..

These things better knock us back on our heels once they are done..
 
On the plus side... I have the front baffles all cut out..

Now all I need to do is get the mounting rail boards cut and glued in, recess the horn, drill and recess the holes for the T-nuts, and get everything attached..

I can almost taste them.. but I'm still a long way away...
 
You saved me Mchaz.. that calculator was PERFECT!... I'm gonna go ahead and use these 3" tubes I have.... The calculator works out great and shows I can use two, or even 3 ports.. but what's interesting, is if I use 2 ports, the tubes are shorter than if I use three... but all still very reasonable lengths.

I just hope this doesn't cause it to be a huffer.....
 
The more port area you have, the longer the length of the ports. The smaller the box, the longer the port for the same tuning. Thats why you see PRs used in small footprint subwoofers. The required port lengths become too long. A 15" PR, is essentially a 15" port, the weight of the cone is roughly equivalent to the mass of air that would fill the gigantic port.

What tuning freq are you shooting for with the 3" ports?
 
I can understand that.. Thanks for the explanation...

I think my best bet is going to be 40hz.. it seems to be the least excursion above the limits from what I'm seeing in the numbers I've been running.. .

I had thought about 35hz, bit I'm about 1mm more on the excursion if I do..

What would you do Dave? I can't decide between 2 or 3 ports. .I think I'd get less huff with 3, even though the tubes would be longer.
 
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If you tune down to 35Hz with less than 4 of those 3" ports then you'll probably get chuffing from the port when you get silly with the volume. The smaller the port area, the higher the air speed inside the port. For your max power about a 5" diameter (or equivalent area) is the minimum you need. With the ports on the back you might be able to get by with the chuffing not being audible though. That'd be a personal call.
 
dnewma04 said:
What kind of power will you be sending to the Lambdas?
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Here's my thoughts.. for now, both drivers will be on my QS's... 40w each. speaker.. not just the Lambda's..

Eventually I'd like to get them on my Bogens.. 100w per chan.....

Then once I get my Altecs and Stromburgs built.. then it would be 200w on each Lambda and 80 on each horn..

I won't ever be pushing the 500w, so I don't think over excursion will ever be an issue.. That's what is giving me a hard time on what to tune for.. what will sound better..
 
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The output level will also affect the point where chuffing will occur.

If you are set with 3" ports, I'd used 3 of them, min with 200w.

With corner loading planned, I'm kind of liking a 4.5 cu ft box tuned 35hz. Three 3" diameter, 8" long ports.
 
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