Custom Subs (1 Viewer)

[mayhem13]

Ok, my new theater room is almost finished sans subwoofers and screen. Flanking my soundstage will be two 8.5 ft cast resin round architectual columns each one 12" inside diameter and tapering to 8"at the top that will support a built in overhead screen enclosure.Each column includes a cast resin capitol and base that can easily be worked. I was thinking to load these columns with 12" subs in a sealed design downfiring from the base once i have figured out the enclosure volume and driver specs. i'll drive them with external amps of 500w each. Any thoughts ?

 

[Robert_J]

Determine the volume of the enclosure. Find a suitable driver that gives you the output to meet your goals and your budget (not always in line with each other so we make compromises) and only then do you deterimine the amp required to power these subs. Depending on the driver / enclosure combination, 500w may destroy the sub due to overexcursion. Or 500w may not be enough and the drivers are just loafing along.

-Robert

 

[mayhem13]

i measured the volume of the column without the driver displacement and it measures 2.65 cu ft allowing for the taper which begins at 1/3 the overall length figuring the reduced internal volume as an algorithim within the volume formula for a cylinder. maybe i should fill it with liquid and measure the volume that way. Anyway a jl audio w713 has a recommended sealed enclosure volume of 2.25 cu ft so minus the drivers volume i should be ok. It's also rated at 1000 watts rms so i can up the amp. Two of these should be incredible. Material costs for 2 will be about $1900 including the columns which i already have.If you have any driver suggestions given the volume they would be appreciated-thanx

 

[Robert_J]

I don't have time to model anything but check out the drivers available from Acoustic-Visions. Kyle has a number of sources including Creative Sound Solutions, DIY Cable, Parts Express and Soundsplinter.

-Robert

 

[Brent_S]

Do you mean the 13w7? If so, are you sure it will fit? You indicated a 12" ID column...the 13w7 has a 11.9" cutout. With typical machining tolerance, that could be a tight fit. Even then, the bolt holes are on a 12.7" diameter...is the column made of suitable material that you can screw directly into it?

2.65 - .21 (driver displacement) for a net 2.44 yields a Q of .728, according to WinISD. A little stuffing should get you to .7 or less. Assuming the driver will actually fit.

It would be hard for me to justify an $1100 driver (Crutchfield pricing...no warranty anywhere else online), let alone two. Assuming a 14" frame will work, you should at least take a look at the Elemental Designs 13Av.2 and run the models. I would probably "settle" for a high excursion 12" such as the Dayton Titanic or Torrent Audio's Mistral DVC.

-Brent

 

[mayhem13]

I can Purchase the drivers for under $600.00 each. The qtc i chose was .707 for the flattest response. My design has the driver mounted into a custom base resembling the supplied column base so the driver will fit following it's taper when mounted on 1.5" of an mdf baffle. But now i'm thinking of a different driver with a higher vas so i can use the full column volume or maybe a ported design. Thanx for all the feedback. I will fill you in as it goes.

 

[mayhem13]

With some great advice from forum members,i've made some changes to my design and thank god for that! Without Unibox, i would have made some grave errors in driver choice,encloure size,ports-you name it i would have screwed it up! I've modeled a different driver if anybody would like to proof my design?? Feedback from accomplished sub builders would be appreciated

 

[dhumke]

My guess (emphasize guess) is the taper will act more like a transmission line than a port. I had great results with a transmission line enclosure of 12” diameter sonotube 8 ft long. I used two 12” woofers with a Qts of .45, I think that’s the main parameter to worry about – you want a mid Qts with a transmission line configuration. I used one 300 watt plate amp for both, and it seems to be plenty. You will probably need to play with stuffing a bit. I’d build one first and try it out.

Good luck, and let us know how it turns out.

 

[Robert_J]

If the column is sealed, then it will act like a sealed box.

mayhem,
You may want to post the details of your new driver if you want us to check your work.

-Robert

 

[mayhem13]

Hi Robert-Just want to say thanx again for all your help.My name is Anthony by the way. I'm going to try and attatch the unibox file but if that doesn't work, the driver i am using is a HiVi Sp10 in a ported design throught the top of the column, The sub is downfiring. If my design is right it should play flat to 25hz at 110db using a 500w amp. The only thing that concerns me is the xmax at 22 hz and below!

 

[Robert_J]

That HiVi sub has car audio sub written all over the specs. There are much better subs for less money. Since you were starting with a 13" sub, why not go with a 12". Check Ebay for auction 300188137596. That's a TC Sounds built sub. It has a low distortion TC2+ motor. Based on the specs and other 12" TC2+ subs that I own, it will crush the HiVi. Here are the specs:
http://web.archive.org/web/200304252.../ep/kspecs.htm

I'd even check with John J to see if he has any of these left - Acoustic Elegance :: View topic - C12.1 Alum cone 12" available, similar to old AV12

-Robert

 

[mayhem13]

I hade to reduce the enclosure size-i was wrong about the inside diameter-went by manufacturers spec-final box volume available is 1.9 cu ft so the need for the smaller driver. I modeled some 10" drivers fromt he manufactures you suggested but they're only making car drivers at the moment. So far believe it or not, the hivi was flat at 110 db to 25hz at 500 watts in a ported enclosure according to unibox and i'm hoping that the round enclosure should help with any standing waves, but i've seen some negative feedback on these drivers that they are really inefficient but 110 db with 500 watts doesn't seem unacceptable. Also modeled the Dayton rs10 and it was pretty close-I hear this would be the cleaner more musical choice.Any thoughts

 

[Robert_J]

The Dayton will sound better. It has a smaller voice coil so the inductance is lower. It has also been reviewed dozens of times as being extremely low distortion.

If I were you, I'd still try and squeeze a 12" sub in there. There is more than enough room. I'm using a 1.2 cf, sealed box as my temporary sub and it would satisfy 95% of home theater users. With an older Dayton 275w amp, I've used a Dayton 12" DVC driver, a 12" Stryke/AE Speakers AV12 MKII and currently an Ascendant Audio Atlas 12" in it. All 3 are great performers and most couldn't tell a difference in a blind listening test. Will it hang with my dual 15" setup? Not even close. But the dual 15" is out of commission until I get another amp that pushes at least 2,000w.

-Robert

 

[mayhem13]

I'm gonna take your advice and go with a 12 inch driver in a sealed enclosure although i'm afraid i'm gonna miss that low punch below 26 hz i enjoy so much. What about rythmik audio's servo kits-good,bad,bull$#%^ ???

 

[Robert_J]

Why wouldn't you have the low punch? I used 15's in 3cf sealed boxes and they were relatively flat to 22hz and 3db down at 17hz. My Ascendant Audio Atlas in the 1.2cf sealed box has a lot of low end as well. I just can't turn it up to wall shaking volumes like I could with the 15's.

-Robert

 

[mayhem13]

I think i've found the answer. I know it's a car sub but infinity has a sub called the Kappa perfectQ 12" that has a low q (.33) that works perfectly for my enclosure size ported. Modeled on unibox at 25hz flat from 100 to 25 hz at 116 db at 400 watts with max excursion at 22 hz. Ports a little wide at 4.25" and 26" long so i'll port it straight out of the top and space the capital 2" from the ceiling. Reviews for this subs overall musical quality are higher than jl in all the auto publications while infinity's beginnings are in ultra high end audio. I can use a remotely located power amp (Crown ati1000?) which has 8 band eq and a built in digital sub control module(usb programmable) to tune it to different presets for HT and music. I'm eager to hear your feedback!

 

[mayhem13]

Oh, by the way-they also make a dual voice coil version-what are the advantages if any to 2 coils? nearly the same q for both and the model almost exactly alike.

 

[Robert_J]

It's not a "car sub". It's marketed as a car sub but the Infinity works very well in both home and car settings. I've seen then used in a lot of home subs. Just don't push them hard or the voice coil will dent the cone.

As for the voice coil configuration, it all depends on the amp. I'd shoot for a 4 ohm final load on the amp in stereo or 8 ohms mono. The Crown amps are very good. Find out how loud the fan is. I had to slow mine down on the Behringer because it sounded like a small plane taking off. Also see if the Crown has a programable subsonic filter. You will need one with a ported box. For example, if your Fb is 22hz, then set your filter a few hz below. 20hz or 19hz. You don't want an 8 hz signal from Lord of the Rings to be blasted through a ported sub. It will push it well beyond its maximum excursion and destroy the driver.

-Robert

 

[mayhem13]

The amp is a csi-1000 that has 6 band parametric eq and link-reilly filters at 24 db rolloff. These can be had for a steal at $500.00. They will sum the input to 2 channel output. The also feature a subsonic harmonizer that adds a new signal derived from the input that is an octave lower and then blends it into the output path. Don't know how helpfull or dangerous this is but it is bypassable. Asked a friend access to a cnc machine to cut the mdf for me.The base of the columns that house the drivers will cut 18 pieces of 3/4 mdf into 13.5x13.5 sheets and then cut a hole 11.315 diameter in each. Stacked and glued, this should provide a very rigid base for the column. I'm thinking to reduce the hole diameter by .175 inches per piece to taper the enclosure to reduce standing waves and channel the enclosures air into the column more efficiently-do you think this is neccessasy?

 

[Robert_J]

I just looked up the Crown CDI-1000. Even the smallest model is overkill for your sub. That's fine if you calibrate your system. Don't use the subharmonic harmonizer. You need 4 times the excursion to produce the same SPL one octave lower. Even I would be hesitant to use it on my 15" drivers and they have an xmax of 30mm and an xmech of 38mm. And there's no need to taper the enclosure. You can't have standing waves in a sub box. They are too long.

-Robert