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building an enclosure for a subwoofer (1 Viewer)

boss hawg

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robert branson
what specs would i need to give you, for you to be able to tell me what size enclosure and port size i need?
thanks
boss hawg
 

Robert_J

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The Thiele/Small parameters as well as budget, goals, listening preferences, amp, etc. There is no 'one right answer' when it comes to building a sub.
 

Mr645

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Start with the driver. The manufacturer will have specs as to what size and type enclosure will deliver different results.
 

Dave Upton

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Once you have a driver in mind, you can input those parameters into WinISD (A free program) to model various box sizes and configurations. Can you tell us what sort of driver and amp you'll likely choose?
 

Robert_J

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I like Unibox better than WinISD but Unibox requires Microsoft Excel. I do know a handful of people that don't use it.
I'm with Dave on this. Any ideas on where you want to go with this? I've seen DIY subs from $200 to $20,000.
 

boss hawg

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ok, new question. i bought a pair of technics sb-cr77 speakers. now, i'm only going to use the subwoofers out of these. they are 8 ohm's each. i'm going to wire them to have a 4 ohm load. you guys seem to be very intelligent about these matters. so. tell me how many cubic ft. do i need to build an eclosure for these two subs. also port size. i do thank you for your time and ideas. i hope it's 4 cu. ft. or less. lol.
robert
 

Robert_J

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Those aren't subs. Those are woofers.
You just took them from the proper sized enclosure. Don't expect much from them if they are used as subs. The biggest difference is excursion. Where a woofer will move 3 to 4 mm each way, a quality sub can move 4 times that much.
 

boss hawg

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they are currently. still in the enclosures they came in. they sound surprisingly nice. considering i have 90 bucks in the nht amp and the speakers. i'm surprised actually.
 

boss hawg

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i do understand your point about the excursion. i'm just having fun with my experiment. but, back to the original question. i guess i should build a box equal to the enclosures that the woofers were in originally.
 

Robert_J

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boss hawg said:
i do understand your point about the excursion. i'm just having fun with my experiment. but, back to the original question. i guess i should build a box equal to the enclosures that the woofers were in originally.
Excursion is how far the cone moves each direction. Watch the cone in this video move more than 1 inch in each direction - That's a sub. Your woofers move about 1/8" each way. They are not designed to play extremely low frequencies like a subs are.
If you are using this as a learning experience, I'll keep helping you. Are your current enclosures ported? If so, what are they tuned to?
 

boss hawg

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they are ported. i have no idea what they are tuned to. i'm going to build an enclosure equal to the enclosures they are in now. and i'll port it also. i know now that they aren't optimum for low bass but, i'm going to use them anyway. they do sound pretty good. i'm going to order a 4'' inch flared port kit from partsexpress.com. thanks for the help
 

Robert_J

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Here's the calculations for porting - http://diysubwoofers.org/misc/portcal.htm
For your current enclosure, you can measure the volume as well as size of the port and use the formula in the link to determine the tuning frequency.
 

boss hawg

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i have no idea about that formula. lol. lets say i build a 6 cu. ft. enclosure for the two woofers. i'd like to tune it flat. you think a 4'' in. port 5.5 or 5.25 in. will do ok?
 

Robert_J

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i'd like to tune it flat
Without knowing the Theile/Small parameters of the drivers there is no predicting the response.
build a 6 cu. ft. enclosure for the two woofers. ..... you think a 4'' in. port 5.5 or 5.25 in. will do ok?
A 5.5 inch port gives you a tuning frequency around 26 hertz. That's not bad. As long as you NEVER feed a signal to them with a frequency lower than 26hz and you don't overpower them, it should be OK.
 

boss hawg

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i think i'm gonna go with 30 hertz. they surprised me with how they sound . i'm looking forward to building the box now. tell me your thought on putting both woofers in one chamber or should i divide the box in two chambers and port each chamber. thanks
 

boss hawg

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i have been reading more. since i watch movies alot. should i tune the woofers lower? 15 - 20 hertz? thanks for your opinion.
 

Robert_J

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I'm pretty sure your NHT amp doesn't have a subsonic filter so the lower you tune the subs, the less likely they will bottom out (over excursion) during action movies. So yes, tune the enclosure lower.
 

boss hawg

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ok, can do. i've been thinking about how the enclosures the woofers came in. i know the size of the box, i know the port size. so i should be able to figure to what they are tuned to now. correct? but i'm gonna tune it low. thanks for your advice. i appreciate it very much.
 

Robert_J

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Rather than use that formula I posted earlier, you can use this - http://www.psp-inc.com/tools.html
You have the enclosure size and the port diameter. Just change the tuning frequency until the port length in the tool matches the real port length.
 

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