Cheap $OB diy

[cheap $OB]

OK,

Im a Cheap SOB, I own the basic wood working equipment (table saw, router, etc.)and I am determined to upgrade my HT a little at a time as I can afford to do it.

Im planning on replacing my 3 pair of little AcousticResearch 2 ways with the TriTrix speaker kits.

Im gonna bite the bullet and replace my cheap projector and home made screen with either a 65" dlp or a 50" plasma. (this makes my wallet cry)

But for right now I would like to get rid of the useless Jensen sub I have that just makes thumping noise that doesnt sound like anything that it is supposed to sound like.

I managed to get a 150 watt (into 4ohm load) subwoofer amp that works for next to nothing. It has a bass boost and an adjustable crossover.

Now I just need to build a box and buy some speakers to put in it.
Ive looked at WinISD and it makes my brain hurt.

Can someone recommend a driver (or two) and a box/port size that will make a respectable sub. I know Im asking a lot , but I what to listen to the opening from Toy Story with Buzz Lightyear flying around and also want to feel the depth charges from U571.


Remember... Im a CheapSOB, I squeak when I walk and my wife has had to vacuum out the dust from my wallet.

Can this be done for around 70 or less? Any help would be greatly appreciated.

[johnastockman]

OK,

Im a Cheap SOB, I own the basic wood working equipment (table saw, router, etc.)and I am determined to upgrade my HT a little at a time as I can afford to do it.

Im planning on replacing my 3 pair of little AcousticResearch 2 ways with the TriTrix speaker kits.

Im gonna bite the bullet and replace my cheap projector and home made screen with either a 65" dlp or a 50" plasma. (this makes my wallet cry)

But for right now I would like to get rid of the useless Jensen sub I have that just makes thumping noise that doesnt sound like anything that it is supposed to sound like.

I managed to get a 150 watt (into 4ohm load) subwoofer amp that works for next to nothing. It has a bass boost and an adjustable crossover.

Now I just need to build a box and buy some speakers to put in it.
Ive looked at WinISD and it makes my brain hurt.

Can someone recommend a driver (or two) and a box/port size that will make a respectable sub. I know Im asking a lot , but I what to listen to the opening from Toy Story with Buzz Lightyear flying around and also want to feel the depth charges from U571.


Remember... Im a CheapSOB, I squeak when I walk and my wife has had to vacuum out the dust from my wallet.

Can this be done for around 70 or less? Any help would be greatly appreciated.


I'm a cheap sob and a total computer luddite, that's why I haven't gotten to designing my own speaker from scratch. I can do cabinet design/modeling, but the XO part requires more time than I can devote. WinIsd is a program that I can use and I've used it to design quite a few subs and small 2-ways. I could help you with WinIsd if you'd like, or input some parameters from some various budget sub drivers and give you the results. The SDVC line of subwoofers have a very high bang-for-buck factor...the SDVC 12" in 3 cu. ft. sealed will make you VERY happy, especially going from a cheap name-brand sub. I've used the 10" SDVC in this arrangement for myself and family/friends with great results, using either the 70 watt or 100 wat plate/sub amp. Granted, this was originally designed for me for 2-channel music, no HT. For HT, probably the 12" SDVC. The 10" version here is in 2.3 cu. ft., net, with a 3"D x 9 3/8"L port and a 70 watt plate amp. It's been compared to many commercial units, both at my house and when taken over to other folks homes. Knocks the wee out of OEM stuff that costs WAY more than what I have into it...even factoring in some extra for my time.

http://custom.smugmug.com/photos/5072111_spp9z-M.jpg

A simple build, but I think the 12" SDVC will be more suited for your HT low frequencies. Let us know what your $$ limitations are. You already have an amp, so the cost of cabinet materials and the woofer could be pretty cheap for what you'll end up with.

John A.

[cheap $OB]

Is this the SDVC you are referring to?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-490

If so I think I can swing that. What size box would I need to build and port size and length?

[arlis_1957@yahoo.com]

i kinda agree. i use the 8" and i does well. but it does not like high spl's.
someone was selling one 12" used.

[cheap $OB]

I'm a cheap sob and a total computer luddite, that's why I haven't gotten to designing my own speaker from scratch. I can do cabinet design/modeling, but the XO part requires more time than I can devote. WinIsd is a program that I can use and I've used it to design quite a few subs and small 2-ways. I could help you with WinIsd if you'd like, or input some parameters from some various budget sub drivers and give you the results. The SDVC line of subwoofers have a very high bang-for-buck factor...the SDVC 12" in 3 cu. ft. sealed will make you VERY happy, especially going from a cheap name-brand sub. I've used the 10" SDVC in this arrangement for myself and family/friends with great results, using either the 70 watt or 100 wat plate/sub amp. Granted, this was originally designed for me for 2-channel music, no HT. For HT, probably the 12" SDVC. The 10" version here is in 2.3 cu. ft., net, with a 3"D x 9 3/8"L port and a 70 watt plate amp. It's been compared to many commercial units, both at my house and when taken over to other folks homes. Knocks the wee out of OEM stuff that costs WAY more than what I have into it...even factoring in some extra for my time.

http://custom.smugmug.com/photos/5072111_spp9z-M.jpg

A simple build, but I think the 12" SDVC will be more suited for your HT low frequencies. Let us know what your $$ limitations are. You already have an amp, so the cost of cabinet materials and the woofer could be pretty cheap for what you'll end up with.

John A.

Question..... You recommend the 12"SDVC in a 3 cu.ft sealed box.
Why the sealed box instead of ported. From what little reading Ive done , I thought that a ported box would be better for HT.... Educate me please.

By the way... nice looking sub you have there.

[terryo]

Question..... You recommend the 12"SDVC in a 3 cu.ft sealed box.
Why the sealed box instead of ported. From what little reading Ive done , I thought that a ported box would be better for HT.... Educate me please.

By the way... nice looking sub you have there.

Sealed enclosures don't usually have the flat frequency response that a ported enclosure can have out to the tuning frequency (after which it drops off rapidly, and will unload if driven hard below the tuned frequency). It does, however, have a mild, smooth bass roll-off that seems to be a good match for room lift ("cabin gain" in car talk) that actually lifts (reinforces) the frequency response as the frequencies get lower, within an actual room.

I've done many ported enclosures, having been a captive to the graphs, until I finally had a moment of enlightenment and actually tried a sealed enclosure. For music, sealed enclosures are better generally, and for HT you can just turn up the bass boost adjustment. Being sealed, the Sub drive won't unload at the lowest frequencies like ported designs can.

These are just observations on my part and results may vary depending on what the spec's of your driver may be. Others may disagree, but this is what works for me.

Best Regards,
TerryO

[johnastockman]

Is this the SDVC you are referring to?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-490

If so I think I can swing that. What size box would I need to build and port size and length?


That's the one. For a box, are you set on a ported design? This driver works well in a sealed cabinet about 3 cu. ft., net. Whether ported or sealed, make sure you add some internal bracing. Some of the gents here could show you some pics of how they did their bracing, so you get an idea. Mostly just tying the side walls and top/bottom together. This is what's lacking in commercial units, no bracing. That's one of the reasons they sound like poo. I've added just internal bracing to retail name-brand subwoofer enclosures and improved the SQ noticeably. Sealed can require some acoustic stuffing of some sort, like polyfill (quilt batting, pillow stuffing). For ported, you can line the interior walls with some of that egg-crate style foam. Make sure air can pass through it. PE has some, I'd use the 1.5" thick variety. If you're set on a ported enclosure, I can run some numbers for you later...about to head out on a motorcycle ride today, so I'll get to it when I get back. Or someone else that has some experience with that driver could give you some good advice. IIRC, Chris Roemer has used that driver in 3 cu. ft. I could be wrong, but I know a few of the guys here have used it with great results. Maybe someone has a ported cabinet and will share their dimensions and port specs. Post up a ? about that specifically, you'll probably get a few responses.

John A.

[johnastockman]

Question..... You recommend the 12"SDVC in a 3 cu.ft sealed box.
Why the sealed box instead of ported. From what little reading Ive done , I thought that a ported box would be better for HT.... Educate me please.

By the way... nice looking sub you have there.


Thanks! TerryO is correct, from what I've read, heard and observed from my 9 years here on the forum. There are too many factors at work to say that ported is better for HT and sealed is better for music. That one in my pic is for 2-channel music in my system. I did the ported because it was my first time using WinISD to design the box and port diameter & length, so I wanted to see how it'd turn out. I have no complaints AFA 2-channel music goes...It gets many compliments on the SQ and bass definition...not one note or boomy at all. The room is a big factor, like Terry pointed out. For your first project, sealed would be a good choice and would work in different room situations. Not to say that a vented box wouldn't. I'm not that much of an expert as some of the guys here, so I'm sure they'll chime in with more recommendations.

[killa]

Sealed enclosures don't usually have the flat frequency response that a ported enclosure can have out to the tuning frequency (after which it drops off rapidly, and will unload if driven hard below the tuned frequency). It does, however, have a mild, smooth bass roll-off that seems to be a good match for room lift ("cabin gain" in car talk) that actually lifts (reinforces) the frequency response as the frequencies get lower, within an actual room.

I've done many ported enclosures, having been a captive to the graphs, until I finally had a moment of enlightenment and actually tried a sealed enclosure. For music, sealed enclosures are better generally, and for HT you can just turn up the bass boost adjustment. Being sealed, the Sub drive won't unload at the lowest frequencies like ported designs can.

These are just observations on my part and results may vary depending on what the spec's of your driver may be. Others may disagree, but this is what works for me.

Best Regards,
TerryO

I personally find that if the sub level is adjusted for a flat frequency response it is very hard to get the driver to reach over excursion.Unless you have some monster mains or tiny subs. Most sub amps also have a low cutoff frequency which also helps.

[dwigle]

I built a pair of subs using the 12" SDVC in a 3ft net box tuned to 28hz. 4'x11.5". Powered by the NHT Foster amps. I'm very pleased with the results. So is my son and his college roommate.

http://i699.photobucket.com/albums/vv360/dwigle/DSCN0200.jpg

[terryo]

I personally find that if the sub level is adjusted for a flat frequency response it is very hard to get the driver to reach over excursion.Unless you have some monster mains or tiny subs. Most sub amps also have a low cutoff frequency which also helps.

Killa,

I'm not sure I understand. You find that tuning a Sub for flat frequency response makes it difficult for the Sub's driver to "reach over excursion?"

Can I safely assume that you mean "flat" in-room response at the listening area (how far away is the Sub?), instead of measurements taken at 1 meter from the driver, then the port and finally merged?

The other detail that I don't follow is what having some "monster mains" will do to influence the sub's behavior.

As far as I can determine, frequency response measurements as normally taken have little to do with over excursion at high output levels. Every driver has various limits (xmax, thermal, etc.), no matter how flat the FR. You can take a driver that has an FS of 51 Hz and design a box tuned to output a
a flat 25 Hz, but it won't go very loud and will quite likely be xmax limited at some relatively low spl level.

Best Regards,
TerryO