4' wide, 3' tall, 15" deep for HT sub

[warnerwh]

What's your best bet on a sub with a box with a box size that is 4' wide, 3' tall and 15" deep. The goal is max bass for HT duties only. The dimensions are maximum so this will fit behind the couch fired at the rear wall which is about 7' back. Any of the drivers in PE catalog are affordable.

I'm thinking 4 of the 12" HO's or 12" Titanic series. Maybe 3 of the 15" drivers would be better. I'm almost done with my first sub which is sealed.This project therefore is way over my head.

Thank you for any help.

[---k---]

For pure HT room shaking, I think you will want a TC2000 or SS RL-P15 over the PE drivers. I beleive that they can move more air/$$.

Quick math says that you're at about 320L with those dimensions. Lots of people have tried and are happy with SteveCallas's design of an RL-P15 D2, 320L, ~15hz. Place that bad boy behind your sofa and you should have good thump in your rump.

Do a quick search for designs with the TC2000, RL-P and the words LLT and you should find one to copy. (though probably a tube, but shape of the enclosure matters little.)

[dwk]

I know it isn't an approach that gets much interest in this crowd, but if I had that much room I'd at least try on of Bill Fitzmaurice's TubaHT's. Most of the tubas are PA/music focused and their response reflects this, but the HT looks to have enough low-end grunt for the application. It'll need eq, but with 95-100dB/W efficiency @20Hz, it won't need the multi-kW amps.
36x36x20 is better, but I think 15" deep would still work. You'd need one 'side' open, though. Since it only needs a single 12" (or 15"), it's relatively cheap and construction isn't that horriffic based on the other Tuba plans I've seen. So, the downside risk isn't that bad.

IB would still be better, but this seems interesting to me. Unfortunately, I don't have room for one. I might be able to do a Table Tuba, although it's not as clear that this is the best use of ~8 cu ft for a music-only system in a smallish room.

[warnerwh]

Thank you guys for the input. I'll look to copy one of those designs K refers to. This is too much fun

This next project will be much easier now that I have a clue on how to go about it. Just wished someone would have said, Veneer it! Don't try gloss black lacquer because there's too much prep work.

I've never veneered but bet it would have been easier and faster too.

Either way the help here has been great.

[---k---]

If you can increase your 15" dimension to 24", you can copy my dual RL-P15 box. And trust me, if you place it behind your sofa this bad boy has enough room shaking power to make you never need a massage therapists again. :B

Also, for a sub that size, seriously consider using the high quality 13-ply Baltic Birch plywood. It cost twice as much as MDF, but is stronger and weighs slightly less. The stronger part allows you to get by with 3/4" thickness rather than 1 1/2", which makes it a light lighter. For the best of both worlds, JonMarsh laminates MDF to BB.

And another benefit is that if you want to skip the veneer part, you can just stain it and it looks great. I did this with my sub and tv stand. People are pretty impressed with the look. I can't take credit for the idea though. I got it from CJD, who did this with all his projects, and they look great.

There have been tons of threads discussing the virtues of BB ply over MDF, so again search. It goes for ~$58 for a 4x8 sheet at Menards and my local hardwood store has better stuff at $59 for a 5x5 sheet.

[warnerwh]

Well I certainly learn something new every day I didn't know that about the Birch and would have happily bought that instead. It may be more expensive at first but it really doesn't matter when you have to finish it some how anyway.

Thanks for the option but I think 15" or at most 18" is the widest it can be as there's a walk way there and a female lives here that has issues with things like that at times. The things we sacrifice for women. ;x(

[---k---]

Everyone here understands the sacrifices we make to keep the women in our lives happy... Everyone but perhaps SteveCallas!

Don't worry about not being able to go duel driver. I think with it placed so close, you won't need the second one (at least, at first. mhuhahahhsaha). I was just trying to talk you into the dualzilla approach so I wouldn't look so crazy. -You know, I could say, "look honey, this guy likes my sub so much he is making a copy! I'm not the only one!"

[warnerwh]

Ok, I've decided to use two RL-P 15's. Box size has changed though to: 40 in wide/ 20 in deep/ 24 in high.

If someone can tell me what size of port to use to get as low as possible for HT but still be accurate upto 80hz I'd appreciate it as I'm still quite ignorant and don't want to make a mistake.

It looks like buying the 2ohm version of the driver and wiring the two in series for an 8 ohm load or 4 ohm load would be wisest. The amp will not care.

[Bent]

depending on the amp you choose, the dual 4 ohm units might be a more worthwhile purchase.

plate amp, or stereo pro amp?

[---k---]

With 40x24x20, I'm getting about 200L effective after you subtract out the port length, driver, and some bracing. That is going to be a tough volume to make work with 2 rl-p15.

For that effective volume, I would suggest considering 1 rl-p15, tuned to around 18.5 using a 6" port and a length of 27.75". Also, you should see if you can find a 6" flared aero port. I've read that Parts Express is now selling 6" precision ports, but these aren't as good.

You should put together a quick spread sheet to calculate the effect volume you will get for your given dimensions. Then download Unibox and play with it a little. There was a thread recently where Thomas walked someone through using it. If you get a better idea of what you want, and how things are related, we can help you better.

[warnerwh]

Bent: The amp powering it will be a channel of a Earthquake Cinenova Grande rated at 300wpc into 8 or 600 into 4 ohms. It will handle a four ohm load easily. A two ohm load gives me the eeby jeebies. I'd rather err on the side of caution even though the amp is rated into 2 ohms. I don't think I'd be sacrificing much.

From what I can gather it appears these drivers will still work in this smaller box. I also know I want to use a ported enclosure for maximum output. When it comes to ports and box size with driver I'm clueless. I'd guess tuning to 15hz would maybe be a good compromise. The sub will have to play to 80hz.

I realize speaker design is full of compromises but I don't understand one compromise over the other. I've read a bunch of posts here on builds using the RL-P15's but am not comfortable making any judgement calls of my own yet. I'll be straight off to Home Depot as soon as I know what I'm doing.

One more question: Would I be best off firing subs outward from each end, firing at the wall 7' behind them or firing straight up? Thanks

It appears that maybe the baffle with these two drivers should be triple thickness. I'll be using 3/4" mdf as that's the thickest the Home Depot by me carries.

[warnerwh]

This doesn't seem right and I don't know what I've done wrong. Box size and wall thickness are correct. How come it's so weak below 50hz? I set tuning to 18hz. I'd think two of these Soundspliter drivers would have zero problem this low. Thank You

[ThomasW]

Since we can't see the box variables you entered, it's a bit problematic to see the problem.

That plot looks like a sealed box, not a ported one

[warnerwh]

Thomas: If you go here:

http://www.audiocircle.com/gallery/displayimage.php?album=289&pos=0

You'll see them. I also have it set for two .140m vents. The vent length area is greyed out and not accessible.

I'd be happy to post the picture here but it's too big. The one in the above post is the first time I've ever done that and it took me a good half hour to learn to do it. I need to know how to make the files size smaller and not lose the resolution though.

I'm downloading WinIsd Pro right now. Let's see how I do there.

[Dennis H]

The vent length area is greyed out and not accessible.

That along with the title-bar label "WinISD -error-" are not encouraging. Reboot, reload and try again.

PS - save the pics as .gif files rather than .bmp and they will be small enough to post here.

[warnerwh]

This is what I get with WinIsd Pro Alpha:



It gives me a vent of 4.02" diameter and 6.53 inches long. It also says end correction .732 whatever that means.

Does this look better? It appears it's 3db down at 100hz, 8 db down at 30hz and 7db down at 20hz. At 80hz it's down 4db.

I realize I have no experience but it just seems like with two of these drivers this curve would look better. I'm sure audibly it's fine but maybe I could change something to make it flatter.

Thank You

[warnerwh]

Unless I've missed something (likely) it looks like I should tune this sub for 15hz using a port diameter of at least 6".

How does port length and diameter relate to tuned frequency? Thanks

[ThomasW]

You can't (actually don't want) to use a port that small 4" with a pair of higher excursion drivers. At high SPL the port will chuff like a steam locomotive.

The box is really to small for two drivers ported to a low Fb. So your best is just to run a sealed box and use EQ to boost the bottom end

[Bent]

My guess is that volume of box ported would be well suited to a single 15" RL-p.
(build two of them).

Your chosen dimensions are similar to mine for a dual sealed 15" RL-p (mine's 22" x 22" x 43"), I'll try a 1124P first, and then afterwords if needed, I'll Linkwitz-Transform it.

[warnerwh]

"You can't (actually don't want) to use a port that small 4" with a pair of higher excursion drivers."

Ok, I thought that WinIsd calculated the best size for me.

So I should use a sealed box it appears. I'm just trying to get maximum performance from this size enclosure. This is actually a gift for my best friend. My own HT sub won't be anything significant. I just would like to do the best job for him I possibly can. I know Bridgette, his wife, will love me for it. :B You should have seen the look in her eyes when he told her how much the HT system cost :E

I presume two drivers in a sealed enclosure will outperform one driver in a vented enclosure?

If anybody has any idea how this sub could be any better with this box size please let me know. Thank You

[warnerwh]

If I use a sealed sub 10 cuft the FR actually dips more when using two drivers as opposed to one. The response on the SS website shows a 5.8 cuft box with a much better frequency response in a ported enclosure. Here's what I got:



It just goes straight down. Look on the bottom graph to your right on the SS page:http://www.soundsplinter.com/rlp15_premium_series_15_inch_DIY_subwoofer_informa tion.html

This doesn't make sense. Maybe I need to tune it higher and use a smaller box? Then equalize the lower end a bit.

[ThomasW]

This doesn't make sense. Maybe I need to tune it higher and use a smaller box? Then equalize the lower end a bit.

They're changing both the box size and the Fb. So yes it makes sense.

Go with a sealed box and your two drivers.

[warnerwh]

What kind of output capability will this sub have with 600 watts at 4 ohms? For example at 20hz. I'm kind of concerned due to the amount of boost this sub will need down there. Until recently I hadn't been aware that movies were coming with frequencies in the teens. I've been into audio for 35 years but HT is like a new galaxy.

Unless there's something else I need to know I'll go get the mdf and order the drivers, binding posts etc.

Thank You

[---k---]

They're changing both the box size and the Fb. So yes it makes sense.

Go with a sealed box and your two drivers.

Thomas,
If this is going to be for Home Theater only, and placed directly behind the seating position, do you think it is better to use two drivers in a sealed box, or just one in a ported?

I'm just thinking that I would save my money and go with a single driver. It will have more than enough power. But, it is really up to the OP.

[---k---]

I'm going to repeat post #10, it seems to be missed:

With 40x24x20, I'm getting about 200L effective after you subtract out the port length, driver, and some bracing. That is going to be a tough volume to make work with 2 rl-p15.

For that effective volume, I would suggest considering 1 rl-p15, tuned to around 18.5 using a 6" port and a length of 27.75". Also, you should see if you can find a 6" flared aero port. I've read that Parts Express is now selling 6" precision ports, but these aren't as good.

[ThomasW]

Thomas,
If this is going to be for Home Theater only, and placed directly behind the seating position, do you think it is better to use two drivers in a sealed box, or just one in a ported?

Two drivers will have basically double the output of one. The only difference in sealed vs ported is the lift the box gets at Fb.

I'm going to repeat post #10, it seems to be missed:

With 40x24x20, I'm getting about 200L effective after you subtract out the port length, driver, and some bracing. That is going to be a tough volume to make work with 2 rl-p15.

You're correct, he has a net volume of ~200L, not the 314L used in the models. Since he has to go sealed, the volume is basically irreverent.

It would be best to buy a DEQ2496 as opposed to a BFD. That way a Linkwitz-Transform circuit can be used to lower the box Qtc and boost the low end output.

[warnerwh]

I'm glad you pointed out that I made a mistake on the volume here. I'll redo the conversion and see where it happened. I should have double checked anyway. Thanks for pointing this out.

What if we use one driver and let my friend run his mains full range. His mains have 15" low bass drivers with ok output capability. They will shake the room pretty well but I'd guess an F3 of 30hz. What I want is something that will feel like a car crashed into the room. If we augment the mains with this sub and tune low for movies with one driver this may work well.

Getting the FBQ2496 as a crossover and parametric equalizer. Doesn't the FBQ model have a regular parametric equalizer like the DEQ?

Until recently I hadn't been aware of movies having frequencies in the teens. This obviously takes major league woofer power. I'm trying to get him all the information in current movies and with more power than he'll need.

[---k---]

The main differance in our usage of the DEQ and the FBQ, is that in addition to all the parametric features of the FBQ, the DEQ adds shelf filters and the ability to create Linkwitz transform functions. This really extends the low end. It is possible to do something similar with the FBQ, but it isn't the same. The linkwitz site and Dennis's post here do a better job of explaining it that I'll ever will, so I'll let you read those.

I'm unsure why Thomas is pooh-poohing the single vented sub idea in favor of the dual sealed. I think you would get the effect your looking for, for over 1/2 the price. (A FBQ is perfect for a vented sub, while a DEQ is perfect for the sealed) iirc, ~200L and 18hz tune is very similar to the design of his Areal Stryke sub, which Bent copied and used a RL-p15 in. Maybe I'm crazy.

[warnerwh]

Ryan: I think using a single driver will easily be plenty. The living room is only about 18x25. If run in conjunction with the mains the rumble factor will be considerable. Just with his mains running it shakes the deck outside.

His mains though have little Xmax but there are two 15" actives plus two 15" passives. They also no doubt cannot play as low as must be being recorded in movies. Believe me I was shocked to see people talking about 10 and 12hz sounds. As you well know real bass is not common at all in commercial speaker designs, at least what I consider honest low bass.

High end stereo audio has been a hobby for 35 years but HT is very new to me so my knowledge is very limited. I'm bored with High end audio and all the pseudo science and other crap that goes on. This diy is far more interesting and fun. It's also refreshing as I don't have to read about a new wire that will give you better bass blah blah.

I think one driver will be enough. If he needs more power I'll tell him to turn the driver around and fact it at the back of the couch.

Btw my apologies for missing your post yesterday of the 200 liter measurement. No excuses.

[ThomasW]

I'm unsure why Thomas is pooh-poohing the single vented sub idea in favor of the dual sealed.

I'm not pooh-poohing anything, he restarted this thread saying.....

Ok, I've decided to use two RL-P 15's. Box size has changed though to: 40 in wide/ 20 in deep/ 24 in high.

All I'm doing is showing him that only a sealed box will work if the plan is to use 2 drivers with that box size.

[warnerwh]

Thomas: Anything I say is truly ambiguous as I'm just learning. There's no doubt in my mind i'm in for a steep learning curve. Fortunately I enjoy things like this. We could use any driver or design you guys recommend. I'll be doing another sub right after this one, only it will be much more simple.

The only reason I chose the SS driver is because above someone said the SS or TC drivers were better for the money than using the Daytons. With next to zero experience I'll happily appreciate any advice. The only requirement is that the box is no larger than 40 in wide/ 20 in deep/ 24 in high.

You guys tell me. I'm trying to figure out how to do this myself but experience is the best teacher. I've built one sub which leaves me out of the experienced category. :lol:

I did find a sub using a tube that's 9 cubic feet and the guy is getting a fairly flat response below 16hz. This is a ported design I just stumbled upon at AVS in the DIY gallery, first page. His FR plot looks excellent. I emailed him to ask for his port size but am not sure if it will be the same in a rectangular box.

My main concern is that I do it right the first time and any help is needed and appreciated. Thanks

[warnerwh]

Here's the FR of the sub using a 9 cubic foot cylinder:

[WillyD]

That looks like Chuck's frequency response.


Is it sad that I know that?

[warnerwh]

It belongs to Chasw98 from AVS.

[Bent]

I prefer to think it belongs to Chasw98 from HTGuide.

[ThomasW]

Oh that Chas98... :W

https://www.htguide.com/forum/showpost.php?p=231614&postcount=11

[warnerwh]

So should I use the same size port as Chasw98? He obviously has bass traps as the pre correction response is really good.

[ThomasW]

The port size depends on the desired Fb. If you want a 17Hz Fb then yes copy his design.

Chuck has no bass traps.

[warnerwh]

If that guy has no bass traps then he's very fortunate. I don't remember seeing that smooth of a response in the low frequencies.

It appears that I can start number 2. This is almost addicting I've already got two more projects to do. Great way to spend a longer than usual vacation though.

[---k---]

I beleive that FR is after EQ has been applied.

[warnerwh]

K: There's a graph in Thomas' link that shows pre equalization. Worst case is plus 8 minus 5 upto 77hz. I hadn't been referring to the graph I posted.

My room with bass traps isn't nearly that good.

[---k---]

nor is mine. Chuck is one of the lucky few.

[warnerwh]

Chuck is super lucky. That's a really nice FR.

What happens if you lengthen or shorten the tube from the 27"?

Thanks

[ThomasW]

Think of a ported box as a bottle. Blow across the top of the bottle you heard it's Fb (tuning frequency).

Decreasing the port length raises the Fb, making the port longer lowers the Fb.

[warnerwh]

Good analogy, thank you!

Does it matter which way the port is mounted? I will have to mount the port in this sub 90 degrees to the driver. Also does a flare add length to the port the same as the parallel part? Thanks