Help me build HT enclosure using 18inch Fi btl.

[pilyo 1]

I now have my 2nd 18inch fully loaded btl, This time am planing to build it for my large home theater room setup powered by a home DIY amp that can produce 2.5kwrms.

in our country we use 220vac.

http://i165.photobucket.com/albums/u72/pilyo168/schematics/5000W_power_amplifier.jpg

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As for car design. From Fi tech recommends:

Fi 
BTL 18 – Ported box we recommend using 5-8 cubic feet @ 30-35Hz tuning, you can tune a little higher if you wish but we recommend keeping it close to 32hz for a daily driver. Again the same 12-16 square inches of area applies per cubic foot of volume.

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Could someone help me design an enclosure for HT use. w/ port tuning at 32hz btl's best lowest FS feature. i know Fi Q is lower but i want btl to do job done.

This is just an example enclosure style i want... seems easier to build. and no out of phase cancellation on the ports and sub issues.

again an example. cut list for 3/4 mdf

2 - 25x35 top & bottom

2 - 27x25 sides

2 - 25x25 front & back

1 - 25x25 port

6pcs - 4x4 gusset

I provided a blank pattern list below to build the box using 3/4 mdf wood. i know the above sample is way too big and tuning above my preference of 32hz. please help me correct necessary inputs below.

2 - x top & bottom

2 - x sides

2 - x front & back

1 - x port[/color

6 - gusset

i also want to add a simple 3 x 3/4 mdf cross bracing inside like this for extra box stiffness.

if you have better design than this pls share.

Thanks.

Edited September 25, 2009 by pilyo

[iputon326 9]

some people on here mite give u some crap bout this because FI's HT sub is the IB3.

[///M5 2,833]

Actually FI's IB sub is the IB3.

Home theater you should be tuning to WAY, WAY lower than 35Hz in which case the BTL isn't really a great solution. You'd really be better off selling it and buying a more appropriate driver.

[KU40 173]

Actually FI's IB sub is the IB3.

Home theater you should be tuning to WAY, WAY lower than 35Hz in which case the BTL isn't really a great solution. You'd really be better off selling it and buying a more appropriate driver.

Yeah if this is for true HT. If you're listening to movies a lot with it, you'll be missing out on a lot of reproduction with a 35 hz tune. For a real HT, try 15 hz. But as M5 said, in that case the BTL is not the best choice. If this will just be for music, then technically it's not HT, but 35 hz would be barely acceptable. I'd still rather have a lower tune even for music in home.

[1phatclipse 2]

good luck with build

[onebadmonte 235]

Try doing a search for a tapped horn. In the diyaudio forums they are having good success with a low tuned tapped horn and a high Fs sub.

[NDMstang65 403]

I've got a BTL 18 in 15 cubes @ 15Hz for the house...with a down firing power port..

Sounds great ..contrary to what some people may believe

[todd.brust 29]

BAAAAAAM! GREEN EGGS AND HAAAAAM!

[///M5 2,833]

I've got a BTL 18 in 15 cubes @ 15Hz for the house...with a down firing power port..

Sounds great ..contrary to what some people may believe

You also have the T/S parameters which I would never recommend designing a HT sub without. Balancing LFE, power handling and cone excursion isn't so easy otherwise and you'll end up with a compromise that could be rather detrimental.

But obviously considering the OP now has an answer 15cubes at 15Hz. How much power?

[NDMstang65 403]

I've got a BTL 18 in 15 cubes @ 15Hz for the house...with a down firing power port..

Sounds great ..contrary to what some people may believe

You also have the T/S parameters which I would never recommend designing a HT sub without. Balancing LFE, power handling and cone excursion isn't so easy otherwise and you'll end up with a compromise that could be rather detrimental.

But obviously considering the OP now has an answer 15cubes at 15Hz. How much power?

Bash 500..couldn't afford the 1kw at the time.

Some of our OEM work is in the HT field..and gets rave reviews from big names...

[pilyo 1]

How come in the roe 12inch challenge tests fi btl leads in hitting the lowest notes. It seems the 25hz is way louder than the popular HT svs ultras specs. Am sure 18inch btl will give way way bigger scores than this.

Ive audition two svs pb13 ultra placed in front and back and it sucks in my spl meter. tested a tone 10 to 25hz is just plain crap i sense small amount of rumble compared to my 18" btl suv install. the svs effect is no sound but air only. my fart could be louder than this. hehe the svs ultra 30hz is not good either... weak imo this will be easily beaten by single 15inch RF rfr3115 sub placed on 4cu port tuned to 30hz.

Stupid question, Do you think svs ultra13 could match this scores? what if you throw 4 of these in an astro van?

i know audio spectrum will not be as flat. i just want spl on my ht. i want to hear loud canon blast, i want my lazyboy chair vibrate as the sub excursion does. lol

thanks sir nick could you share your 15cu 15hz cut outs? am now surely will continue this project with confidence.

.

Edited September 28, 2009 by pilyo

[shizzzon 461]

I was just about to say do it anyway when NDMStang showed up, lol.

I've tuned some subs way below their recommended tuning before and the only thing i've seen u gotta watch out for is lower power handling.

I'm sure ///M5 can elaborate what else happens in terms of the way it sounds from a higher Fs because i've never used a true HT sub before.

I've ran an Audioque HD3 in a 29hz enclosure once in a car, single 15 in 8cubes.... it's Fs is 40hz. Very, very low... i wouldnt recommend doin that again, it tore the car apart.

I also designed an enclosure recently for somebody for a single 5.25" sub with a 45hz FS that i tuned down to 34hz and i got great complements on how much more alive the speaker is now. I just told him to lower the power handling some and it should be fine, monitor the excursion for a while and should be good to go. This was just for music, not HT.

So, what is happening when tuned way below FS?

[///M5 2,833]

Excusion limits are easier to hit.

My comment was based on the fact there are no published T/S parameters. When you tune below Fs I really like to have a model that is going to show me what is going to happen at what frequency in order to set things up to maximize LFE without killing the driver.

[onebadmonte 235]

I found some down loadable WinISD Files these are for the pro version.

http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html

There are probably some T/S params in there. I can't vouch for the accuracy. You'll have to join to download most likely.

[///M5 2,833]

I found some down loadable WinISD Files these are for the pro version.

http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html

There are probably some T/S params in there. I can't vouch for the accuracy. You'll have to join to download most likely.

The BTL is most definitely not in there. Not on Fi's site either which is exactly why I said what I did. Understandably though because if noobs had them it would create more confusion than it would solve.

[NDMstang65 403]

I found some down loadable WinISD Files these are for the pro version.

http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html

There are probably some T/S params in there. I can't vouch for the accuracy. You'll have to join to download most likely.

The BTL is most definitely not in there. Not on Fi's site either which is exactly why I said what I did. Understandably though because if noobs had them it would create more confusion than it would solve.

The parameters are on the site...

BTL18

DUAL 1 | DUAL 2

Fs: 31.9 Hz | 31.1 Hz

Re: 0.7 Ohms/coil | 1.4 Ohms/coil

Qms: 6.26 | 6.42

Qes: .26 | .24

Qts: .24 | .023

Mms: 313g | 329g

Sd: 1210cm^2 | 1210cm^2

Vas: 163.1 l | 163.1 l

Spl: 94.9dB 1W/1m | 94.9dB 1W/1m

Bl: 18.3 N/A | 27.2 N/A

Xmax: 28mm * | 28mm *

Rms: 2000W * | 2000W *

Sealed box: N/A cuft | N/A cuft

Ported box: 5-10cuft | 5-10cuft

Sub OD: 18.500” | 18.500”

Cut ID: 16.750” | 16.750”

Mounting depth: 10.250” | 10.250”

Displacement: 0.26cuft | 0.26cuft

Standard 3-7 business day build time.

Product code: 00218

Price: $ 414.00

[pilyo 1]

I found some down loadable WinISD Files these are for the pro version.

http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html

There are probably some T/S params in there. I can't vouch for the accuracy. You'll have to join to download most likely.

The BTL is most definitely not in there. Not on Fi's site either which is exactly why I said what I did. Understandably though because if noobs had them it would create more confusion than it would solve.

The parameters are on the site...

BTL18

DUAL 1 | DUAL 2

Fs: 31.9 Hz | 31.1 Hz

Re: 0.7 Ohms/coil | 1.4 Ohms/coil

Qms: 6.26 | 6.42

Qes: .26 | .24

Qts: .24 | .023

Mms: 313g | 329g

Sd: 1210cm^2 | 1210cm^2

Vas: 163.1 l | 163.1 l

Spl: 94.9dB 1W/1m | 94.9dB 1W/1m

Bl: 18.3 N/A | 27.2 N/A

Xmax: 28mm * | 28mm *

Rms: 2000W * | 2000W *

Sealed box: N/A cuft | N/A cuft

Ported box: 5-10cuft | 5-10cuft

Sub OD: 18.500” | 18.500”

Cut ID: 16.750” | 16.750”

Mounting depth: 10.250” | 10.250”

Displacement: 0.26cuft | 0.26cuft

Standard 3-7 business day build time.

Product code: 00218

Price: $ 414.00

What's the * specs when loaded?

DUAL 1 | DUAL 2

Xmax: 28mm * | 28mm *

Rms: 2000W * | 2000W *

Sir Nick could i use the re cad enclosure calculator building the 15cu @ 16hz? would there be a difference front port vs down firing power port? please help.

[NDMstang65 403]

The * is with the Hixmax coil...

http://www.hometheatershack.com/forums/fi-audio/16903-built-new-box-house.html

I've got a down firing power port that polk has a patent on that I built for it..works great.

Join the community..they have a great bit of information there.

[onebadmonte 235]

Ha, I though that was a Q sub you were using. Nice.

[NDMstang65 403]

It was at one time...i get curious and flop things out from time to time

[onebadmonte 235]

It was at one time...i get curious and flop things out from time to time

That's cool, I flop things out from time to time... Wait, what are we talking about?

[///M5 2,833]

What's the * specs when loaded?

Exactly what I meant. Modelling the stock BTL shows me that I'd never even think about using it for HT without a BFD or other extreme equalization. It'll swallow that 2500w though If I were building a box for it I'd shoot for a lower tuning, you don't lose much output as that sub has excursion to give and you will get something that will thunder the lows. You'll have to roll it off up top though. 12Hz should be fine.

*Caveat is that the rec'd/model I did was for the T/S on the site

[NDMstang65 403]

What's the * specs when loaded?

Exactly what I meant. Modelling the stock BTL shows me that I'd never even think about using it for HT without a BFD or other extreme equalization. It'll swallow that 2500w though If I were building a box for it I'd shoot for a lower tuning, you don't lose much output as that sub has excursion to give and you will get something that will thunder the lows. You'll have to roll it off up top though. 12Hz should be fine.

*Caveat is that the rec'd/model I did was for the T/S on the site

Which is why I'm dead set against modeling things and taking them as the second coming of Christ.

It would give you an idea..but it doesn't sound anything like it 'should'...sounds quite good actually.

[///M5 2,833]

I didn't hit the "go" button, I actually utilized the software as a tool