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Discussion Starter #1
Hello!

Beginner DIYer here. Been reading here and other forums for a few months getting ready for a build over the winter. I have a closed off basement room about 2100 cubic sq. ft. in an L shape with low 7 foot ceiling and concrete floors. I will work up a room layout. Room is 90% HT / 10% Music.

I have a $280 BIC PL-200 12" 250 W sub now that we like to crank to max on the receiver +12 db after audyssey xt eq. in order to get the room rocking more the way we like. It is in a corner and the floors are all concrete. I does o.k., but I would like a bunch more. The "bunch more" is the problem. I am wondering what I should shoot for as a start?

I have room for two subs under the projector screen without any other placement options in the front. Maximum size for two boxes in the front is 42" W x 24" H x 22" D. These will sit on either side of the center channel. We sit about 9 feet from the projector screen that is mounted to the wall. We will sit about 7 feet from subwoofer box to the "ear" after the subwoofers are built.

I have room behind the couch to eventually build just about anything. Even an IB or horn or something, but I would like to stick building something I can look at in the front for now. It would also be nice to build the front and be done with it :)

I was going to go with two SI-18s in ported boxes with an I-nuke 3000dsp. I can afford to build this configuration over this winter.

All of the reading on the forums about monster systems has got me thinking about up-sizing before I even get started.... I wonder if I should start with one sealed FTW-21 or equivalent and build a second FTW-21 later? I can't afford two FTW-21s and an amp this winter.

Any thoughts? Am I going to way over shoot to begin with and never need to turn it up if I go with Ported SI-18s? We like to rock the room, but typically watch movies at -10 with just the current subwoofer at +12. I am going to play around with getting more output from the current sub tonight. Any advice?

I need to figure out how to borrow some bigger subs and try them out in my room I guess to see how much I need? I don't have any measurement equipment yet.

Thanks
 

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You are off to a great start with your thinking! A pair of FTW21 would be awesome, for sure. Finding a pair when you want them is a different story. Two ported 18 SI or Dayton HO is what I was thinking when I started reading your thread. Your room is a great size for filling with good bass. I was messing around with my subs yesterday and planted one firing right against the side of the couch and it created the most tactile feel I could imagine from a sub. Maybe you could build the two ported for the front and see how you like them behind the couch for the tactile feel of near-field. If you like it, build two more to stay behind the couch.
 

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The FTW21 would be superipr in output but only if you give them the power they need. The I-nuke 3000dsp would work well with a pair of ported SI 18's, the FTW21's would each require a EP4000. If your willing to spend the money on the amps then go with the 21's, they would have better low end extension over the 18's and higher output above 30 hz.
 

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Discussion Starter #4
Thanks Doug and Mike.
Mike, I just looked at your builds. You seem to have a same sized space and a bit more than two si18s. Do you ever wish you had more?

I am not shooting for the moon or some hero build. I don't want to over spend and build way more than I would normally use, but I also have no problem doing it right if two 21" and a inuke 6000 or more is needed. I like to think i am an over built it a bit, but be practical kind of person...

I guess I could go over budget and get two 21s. Are 21s in a 9.5 c.f sealed without fill enclosed too large for inuke 6000 power?
Do I need the DSP version to smooth room issues?

Is this all up-selling myself or will I have no regrets? I know there are no clear answers!

Are the ftw21s still available. I may start making boxes next week...
 

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I have 2 18's and 2 15's, all ported, and they provide me with everything I need for low end extension.


Here is some SPL modeling to give you an idea.

Purple would be the combined output of a pair of ported SI 18's powered by an iNuke 3000DSP

Red would be combined output of a pair of sealed FTW-21's powerd by a iNuke 3000. DSP not required.

Yellow would be combined output of a pair of sealed FTW-21's each powerd by a EP4000.

Green is the output of the BIC PL-200, which has been measured as 110 db with a -3 db point at 22 hz, which the graph reflects.

Which ever route you decide to go with you have huge gains over your current sub.

ftw21.jpg
 

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Discussion Starter #6
Thanks Mike.
I don't know think I have much experience with the range of volume that the 21's would provide...
May be a silly question, but would additional low end the 21's at full power would provide be felt as they still tail off? I don't have a clue...
What size sealed enclosure for the 21's that you modeled? And how many watts or volts?

It looks like i will try and blow my budget and see if the ftw21s are available.
What single common amp and box size would work best with two ftw-21s? I would prefer a single amp to power both. Would an inuke 6000 not do the job @ 1800 to 2000 watts at 2 @ 4 ohm?

I am already one of those guys asking a bunch of questions.

How about a 29 w x 22 d x 25 h sealed box. I can go up to 25.5 tall after all.
Down cleaning and measuring dasement now!
 

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Cant go wrong with a pair of 21's. I have a pair and the only thing I don't like about them is I NEED a lot of power to use all their capabilities. But I made mine in much smaller cabinets. So going with a box size that allows you to use RMS power to hit Xmax would be great.
 

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Discussion Starter #9
I measured again this evening. My maximum outer box size to fit under my screen in the front of room is 42" wide x 25.5 height x 22 deep. That size will fit under the screen and outside the center channel. I really can't do speakers behind a screen as the viewing distance is only 9'. It is a funky L shaped room. I will post a room layout tomorrow.

Thanks for the help. I want to get started next week, if I can decide on a woofer and form factor....
If I only go 29" wide I can keep my current main towers tweeters at ear level. Otherwise the main will sit on top of the subs until I can DIY some outside channels the rearrange the outside tweeters and mids. Not a problem, but will take time to save funds....

Louis
 

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Discussion Starter #12
Looks like I will be starting a sealed build thread soon...

Have a FTW-21 on its way.

Thinking about a 7 cf internal enclosure. W 28" x H 25.5" x D 22" external sealed.

Powered by Inuke 3000dsp in 4 ohm bridged. Want the DSP version to play with the DSP. Thinking I can play around with the DSP to maybe boost the low end and try out different settings, but need to learn more.

Attached is a sketchup pic. I need to work on the internal bracing.

I am only building one this winter. Maybe another or something else next winter.

Any advice on the box, amp or other?
 

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The Cerwin Vega CV5000 will give you more than enough power at 5000w bridged 4 ohms. A Sanway fp14000clone would be perfect for a pair of them at 4400wpc at 4ohms stereo. 6 cubes is the suggested box size for your sub. I would at least double baffle the front and use interior braces every 8" of flat surface on the inside for that big boy. I'm excited for you - this will be awesome.
 

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+100 on double baffle.

Brace brace brace. I have a pair of these in 5.5cuft and wish I could do the boxes again. I would do a a much heavier cabinet with more bracing. This is overkill but I don't like feeling my cabinets vibrate at all. To me that means I am losing dbs.
 

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Thanks for feedback,
It does not show in the graphic, but the box will be 3/4 inch MDF with a planned 1" plywood mounting layer. So the sub will mount past a 3\4 inch MDF layer into a 1" ply layer. I am still working on a bracing strategy. At an internal 7 cf with stuffing will 2000 watts be enough to get close to x-max in the real world? It models close to 30mm without e.q.

Do you think a inuke 3000 bridged into 4 ohm will have any more power to e.q.with into the sub 20 range? Or will it be totally maxed without e.q.?

Of course I have no idea what I am doing? ;). I just want a good range to play around with and learn.
 

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I have double 3/4" sides and double marine ply baffle. With just the amp you should be fine for your wants. When you start adding in EQ you are also putting on more load for the amplifier. So the amp may clip if you boost to much. That's why it is recommended to have double the power if you can.

I don't know what your spl wants are but I love bass myself and with 4000watts total with my pair of 21's I am happy in my 2000cuft room. I still want more power but only because I want to add a L/T circuit. 95% of the time I listen at 105dbs and no higher.
 

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Discussion Starter #18
Well if the inuke3000 can't cut it I will save up for more power. The inuke, ftw-21, MDF, and little parts have exhausted my budget for now. I can always save for more later.

How do you accurately check sub excursion? Some kind of laser or slow motion camera to measure distance?

I am curious to see if this will blow me away or make me want more. If I need a second sub then I will amp up.

I could go remeasure and see if I could expand the box a bit (1/2 a cf?), but I probably would regret it in the space.

My thoughts were to use a low shelf filter in the inuke DSP to boost the low end .5 or 1 db or so if I was not pushing the amp overall anyway. May not have the power to do it sounds like. Right now i can find the inuke 3000dsp for less than the ep4000.

If I get my hunny-doos done I will start cutting this afternoon! Sub might arrive today!
 
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