My First Sub

[collo]

Hidden volume

If you're going to locate your sub next to a sofa that is against the wall, you might consider the space behind and underneath the sofa.

Most sofa's sit out from the wall at the bottom, leaving enough room to extend your box along the wall and under the sofa.

This gives you additional volume to play with, allowing the visible part of the sub to be more presentable.

The other advantage is that you can fit a long port or two, allowing that infrasonic tuning you were considering!
Throw in a 90 degree bend and you can exit the port next to the driver.

regards
Collo

[---k---]

Mike got back to me. He said 3 cu ft. would be "just fine". So, I'm not going to worry about it.

[borderdad]

For Bent

What's the story about the sub in post 11? I'm assuming it's not the 11cuft sub you mentioned. Is it a Soundsplinter with the elusive 6 in aeroport? Looks about the size I need. Thanks. Kevin.

[ThomasW]

What's the story about the sub in post 11?

That's Ben's version of my AS-15 design. External measurements are 18" wide, 29" tall, 35" deep, so almost 11 cu ft, gross volume.

SS doesn't sell ports. There are currently 2 sources for 6" flares. In Canada (they'll ship to the US)

http://2loud4you.ca/shop/index.php?main_page=product_info&products_id=3&zenid=b915fc78891bb55ba2461d9f56376034

And in the US until supplies run out.
http://cgi.ebay.com/ws/eBayISAPI.dll...Pr2_PcY_BIN_IT

[---k---]

Torture is:

Torture is: Telling your wife that you are going to be buying a BFD anyway, so it would make a great Christmas gift. Why, because now it must stay in it’s box until the 25th.

[ThomasW]

This is a not so subtle hint to start building the enclosures....

[---k---]

Is that a subtle hint from you or my wife?

I've been meaning to "borrow" a copy of Autocad from work, so I could make some drawings to print out full size and use as templates. I guess I need to get moving.

I'm still not set on my box size. I'm set on 26" high. I would like it to be as narrow as possible, so I think that makes it 18" wide. I'm flexible with my depth. I was thinking about 20" deep, which gives me about 90L total. My Unibox model shows that with no fill, this gives me Qtc=0.555, and with heavy fill Qtc drops to 0.509.

Does this sound optimal? I'm a little confused, because this still sounds smaller than what I thought you guys were recomending. I could make it an inch or two deeper, but I'm a little worried about dropping my Qtc much lower, because I've read on other sites, such as diysubwoofers.org that Qtc should be between 0.6 and 0.7, and that seems to be where Mike was. I understand that there are a couple of differnt schoolsof thought. I was just hoping that I could learn what they both were. (But I do trust you guys fully. )

Unibox seems to show me that lowering the Qtc just flattens the response down low, and I'm no where near max excursion until I get my box volume up to around 140L with lots of fill.

Thoughts?

Thanks,

[Bent]

I'm not the expert here, but I say you want to run out of excursion at about the same time you run out of available power, try to make your enclosure as such. I'd think response irregularities could be easily dealt with via a BFD in the loop and youd have the most to work with if the box is large..

Thomas, any thoughts?

[ThomasW]

Unibox seems to show me that lowering the Qtc just flattens the response down low

Yep

and I'm no where near max excursion until I get my box volume up to around 140L with lots of fill.

That's okay, it's nice to have a little extra headroom when time comes to dial in EQ.

The effects of room placement will likely make a the difference between a "Q" of 0.555 and 0.509 inaudible.

but I say you want to run out of excursion at about the same time you run out of available power

That's an interesting design exercise. For safety it's better to run out of power before you run out of excursion. That's probably not an issue given the design of the RL-p 15"s

[---k---]

The amp has arrived. The drivers should be here on Monday. So, I need to finish ordering all the other parts I need.

I know I need terminals. I've seen this terminal box recommended before: GOLD HIGH POWER TERMINAL RECTANGLE , or do I just want binding posts like these: DAYTON BPT-38G BINDING POST PAIR w/TAB RED/BLK . It seems silly to me to use 1 1/2" thick MDF and then to use a wimpy plastic terminal box. Am I underestimating the strength of that terminal box? And am I correct in thinking that to use the binding posts, I just drill a hole in the box and seal them in with silicone sealant?

Next up, spikes. PE sells these for $18.88. I'll need one of those for each sub, so thats like $40/shipped. That seems crazy expensive to me for spikes. Is there a better/cheaper alternitive? My floor is carpet over concrete. I guess I could just use make something either out of MDF or doll rod, but was thinking that something more finshied polished looking would help my subs not look so DIY.

Fill: I have new unfaced R30 in the garage. I beleive this is good to use.

Seals: I'm going to be placing an order with PE. Is it better to use SPEAKER GASKETING TAPE 1/8" x 3/8" x 50'. Or, should I just get some weather stripping from Lowes? Cost really isn't a differnt, so which works better.

Grills: for simplicity, I'm thinking I will surface mount the driver. I haven't decided what to do for grills. I kind of like how AJpoe's turned out: https://www.htguide.com/forum/showpo...&postcount=187 . Is there an easy way to acheive this look with a custom box size? I'm gussing cut a frame out and wrap it in speaker cloth. Or is there a source for decent looking 15" round grills. The PE ones are plastic. Yuck.

T nuts: I need some of these. Are the PE hurricane nuts better?

Anything else? What have I forgotten?

Thanks,

[ThomasW]

PE also sells these spikes, they're what I use for subs

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=240-730

No don't use the PE gasket stuff, over time it will harden and glue down the driver. Instead use closed cell foam weatherstripping tape from a big box store.

T-nuts don't hold well in MDF.

The little plastic back plates work fine. We're concerned with large areas vibrating, not small areas

[SteveCallas]

I went with those exact binding posts you linked to - the second ones. They give you good length to work with and you can use spade rings and just screw them down onto the back as opposed to soldering. I didn't feel right cutting a big rectangle out of my MDF either, so I just made two small holes and screwed them in. I used a couple dabs of hot glue on the outside and a couple neoprene washers on the inside to keep it sealed, even though they screwed in really tight and were probably sealed already.

Would rubber feet honestly be any worse than using spikes? I'd consider something like this:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-774

As for the T Nuts, via a suggestion from Thomas, I used some plywood rectangles behind the MDF to mount the T Nuts into. I used 3 layers of 1/2" plywood for each T Nut, but I'd imagine you would be fine with just 1.

[wildfire99]

I've always used coarse thread drywall screws with MDF, since having the usual nightmare of free-spinning T-Nuts on my first 'project'. I've mounted and unmounted drivers many, many times in the same holes with no problems. Just don't tighten the screws down past "hand tight".

With a good circle jig, I've found putting in circular terminal cups to be a breeze. I used the binding posts on my surround speakers and disliked it enough to not want to do that again. The posts are very nice and easy to use, but they stick out and catch and scratch everything they possibly can, and make handling the box just a bit trickier. The gold plated ones also do not hold onto spades with a death grip. (Not that I like spades even if they did hold down well. )

[---k---]

Steve,
Man those rubber feet are UGLY! But, you're probably right that they would work just as well. I just need to concentrate the weight of the sub on the feet to prevent it from walking (or so I'm told). The rubber feet would make it easier to move these monsters around, and likely won't be seen if they are only 3/4 inch tall. I was looking at Madisound and they got some smaller spikes for $.90/ea. They also got some smaller rubber feet. I'm going to think about it.

In other news,
I realized tonight when reading though some of the PE projects, my garage isn't heated and glue doesn't dry well in the current Chicago weather. I think I'm going to have to buy a space heater and put one of those window kits up and new eather stripping on the door. Boy, this is getting expensive.

[ThomasW]

On a carpeted floor spikes are the best choice.

PE has smaller and cheaper spikes too, but they aren't a good idea with the weight of a well built 15" sub.

I always use t-nuts or some form of threaded insert. It's more work up front, but much less hassle than dealing with stripped out wood screws. When tuning the amount of damping in a sealed sub one takes the driver in and out frequently.

The only issue with the single long posts is that getting them aligned for dual banana plugs is a royal pain, and I use dual banana plugs for all my speakers.

[Brian Bunge]

The only issue with the single long posts is that getting them aligned for dual banana plugs is a royal pain, and I use dual banana plugs for all my speakers.

Thomas,

It's interesting to hear you say this as I've never had any trouble getting single posts aligned for dual banana plugs. I mark my holes 3/4" apart, use a center punch to accurately mark a starting hole, and then use my cordless drill with portable drill press to drill them out. My posts always end up aligned well enough that the dual banana plugs fit nice and tight.

I'll admit that taking the time to measure, mark, double-check, drill, etc. is a bit time consuming, but it's always worked well for me.

[SteveCallas]

Umm, or you could just go with single banana plugs?

---k--- no free space in the basement or anything like that? I built might right in the middle of my living room - it was a HUGE mess, but it was only a mess for ten days.

[---k---]

Thomas,
I'll order the spikes you linked to. I looked again at the Madisound ones, while they look like a decent size cone, they use a 1/4" dia insert. I can see the sub getting bumped and those ripping out. So the 1/2" dia of the PE is probably better.

I've seen you recommend the plywood blocks on back. I'll do this. I was just wondering if those Hurricane Nuts or Barbed nuts would work without the plywood backing. I've done some searching, and it doesn't look like anyone has given them a shot.

As for bananas, I'm still using bare wire! But I hear you.

If those terminal boxes are okay, have you ever put those handle boxes in the sides? If this thing is going to be 200lbs, it might not be a bad idea. It will be ugly, but might be worth it.

[---k---]

Steve,
You are obviously single! We'll talk again in a few years when you're married.

The basement is finished, with the family room where the sub is going. My wife actually is pretty good with all this. She said I could bring pieces inside at night to dry.

[ThomasW]

I've thought about using thosee handles, but I have both 4 wheeled furniture dollys, and 2 wheel appliance dollys/hand trucks, they make moving heavy stuff a snap

[Brian Bunge]

Thomas,

I sure could use your help moving my big 3-way towers from GA down here to Orlando in a few months. Wanna come down and help me out?

[---k---]

I'm scared that I didn't know what I was getting myself into! Oh my gosh!





:B :B :B :B :B

I'm hoping that the finished boxes will look a lot less intimidating. At least for my martial status' sake.

[Ray_D]

---k---

I'd be interested in how close you can put those drivers to a conventional TV before you can see the effect.

Ray

[---k---]

See where the Nady box is. Both are sitting in their boxes in that position. I was worried, but it doesn't seem to be a problem.

[PoorboyMike]

If I had all that stuff I would be hooking those suckers up and seeing how they sound sitting on the floor.
:B

[---k---]

It took them well over an hour to come out of the deep freeze they were in. Its kind of cold here in Chicago, and they were in my trunk most of the day. Well, one was in the trunk, and the other was in the passanger seat, because they both wouldn't fit in the trunk!

By the time they were warm, my wife was home, it was dinner, etc.... I'm going to hook them up tomorrow night.

[SteveCallas]

Tell me about it. I'm originally from Chicago, but now in St. Louis, and all of a sudden in the past two days the temperature has dropped into the low teens. Damn you El Nino :M

[ThomasW]

It's 3.7 degrees F in my backyard right now, 10:00PM

[PoorboyMike]

It's 3.7 degrees F in my backyard right now, 10:00PM

Wow, that's cold! It's almost twice as warm here.

With all the remodeling I've been doing on our house lately, I didn't get a chance to insulate my shop this fall. Looks like I better hold off on the rest of the kitchen and get to work out there if I want to do all these crazy projects brewing in my head. Any tips on explaining this to my wife?

[collo]

Whilst we're completely off topic and talking temperature, today I measured 42 degrees centigrade in the shade. Thats about 107F
Damn you El Nino.... :M

[GrahamT]

I'll trade with ya, it's 10°F here right now, 1°F with wind.

[ThomasW]

Okay I'll trade ya it's -6.6F (-16F windchill) here this mourning ...

[SteveCallas]

Thomas, what area are you from? -6 almost makes me feel better.

[ThomasW]

See location below avatar = 5280', aka Denver, the mile high city

[Brian Bunge]

You guys make me feel even better about moving to Orlando last month. The coldest it's been so far is about 40 degrees F, and that was only overnight for a couple of nights.

[cjd]

Wonderful weather in which to wait for the train, to be sure. This morning, 6 degrees + a very nice breeze. And a late train. Yesterday I think it was 3 degrees and a late train. And that's Chicago!

Will be in Orlando Friday morning though. Just through Sunday. It's probably going to rain the whole time, too, just because.

C

[---k---]

Well, since were in a "my house is colder than your's" contest, it is currently 1 degree here, and few days ago it was -11 degrees. And just to make you go hummm, did you know that +11F is the same as -11C. Hummmmm.

Anyway, back to subwoofers. I hooked up the twins to the amp this evening. I just set them on the floor, and wired them in series. I threw in The Incredibles and Matrix. I'm not so intimidated by them now.

I am correct in my thinking that they need an enclosure to function, right? Because there was very little there, and I had the amp turned 3/4 of the way up.

[edit silly math error on temps.]

[Bent]

LOL - yup, what you heard is the "twins" pumping air from the front of the cone to the rear and back again...

Yes, they need an enclosure (or a baffle at least.)

BTW, it's minus 18°Celcius here, with a windchill...

[ThomasW]

BTW, it's minus 18°Celcius here, with a windchill...

This is a contest you Canucks will always win ....

I am correct in my thinking that they need an enclosure to function, right? Because there was very little there, and I had the amp turned 3/4 of the way up.

They have a VERY stiff suspension, so it will take some time for them to loosen up.

Also BE CAREFUL running the drivers without a box, you can damage the drivers doing that.

Little sound in free-air? Yep that's because the front and rear waves are out of phase. When there's no box they meet and cancel each other out

Box?

Okay just build the biggest box you can comfortably live with.

And your question about a low "Q". Critically damped 0.50 makes the best sound quality for music. Not interested in that? No problem, you've got the Behringer and it's no big deal to dial in a bit of EQ to make a low "Q" box sound like a high "Q" one. But you can never EQ a high "Q" box to sound like a low "Q" one. Make sense?

[---k---]

I will begin building as soon as possible.

Got a question about sheilding the drivers. If I want to put some 16ga steel in the box, do I want to put it between the layers of MDF? If I do this, what is the best way to deal with the gap along the edges.

I found out last night that 10" to 12" is about as close as I can get the drive to the TV without problems. I don't think I will ever have them that close, but it is cheep and easy to put some sheilding in, and then never have to worry about how my wife wants to rearrage the room.

[ThomasW]

When we built Tibor's MTM center channel (unshielded 8"s) we alternated MDF, steel, MDF, steel. The sides and back were made this way, there was no steel in the front baffle. We also hot glued a bucking magnet to the back of each driver. His CRT sits directly on this speaker and there is no distortion.

There was no gap around the edges. We assembled the box excluding the back, it was built separately. The back was made from two pieces of MDF, the smaller inner layer slid inside the frame by the side and top/bottom, the larger outer layer capped the back of the box.

Understand that this from of construction makes the box VERY heavy.

[---k---]

Thomas,

You used the layers of MDF to make lap joints. That makes sense. I was originally planning on building my enclosure that way,but then I got worried about having make all my cuts that much more straight and accurately, so I figured that I would go with butt joints.

If I want to use butt joints, is there any good way to fill the 1/16" gap?

Are there any tips you can provide for saving weight? I was thinking about using 3/4" MDF laminated with 1/2" MDF and then use the 1/2 for my bracing also. I know Brich ply, but that is too expensive.

[ThomasW]

We used butt joints, but built the box in 2 separate layers, not from a single piece of 1.5" material

First we build the outer shell minus the back. Then layed in the steel. Next we inserted and glued the inner layer of MDF, then added the final layer of steel.

Now that may have been overkill, don't know. Since his intended use was as a stand for the CRT, I didn't want to take any chances.

During construction when all the steel was installed on the top/bottom/sides, we mounted the drivers in the cab and left the back off. We took it up and placed it on top of my CRT and there was no distortion.

To save weight you can make the inner layer with 3/4" OSB (oriented strand board, aka flake board) instead of MDF. It has the strength of ply but is much cheaper

[---k---]

Oh, I see. You didn't laminate the MDF before building the box.

Is there a thread for Tibor's center? I searched for posts by Tibor, but didn't see one relating to his center.

[ThomasW]

No sorry there aren't any construction photo's of the center. Here's a chronology of the construction

First we made the outer 3/4" box. Next we glued in the 2nd 3/4" piece to make the front baffle 1.5". Then we cutout all the driver holes.

Note if you intend to flush mount (recess) the driver, the front baffle needs to be at least 3 layers of 3/4" material. If not the suspension will stick out

Next we added the first layer of steel. We sanded the steel to provide some tooth for the contact cement used to glue it down.

Next the second layer of wood and finally the second layer of steel.

His center was only 11" high by 30" wide by ? deep. As a result we couldn't get a drill or screwgun inside the shell. Since your box is much bigger, after everything is assembled, I recommend drilling and screwing the laminated panels together with sheet metal screws from the inside.

Contact cement holds the steel to the wood but the bond isn't structural. So drill and screw a grid across the field of each wide piece of wood.

We used TiteBond II where wood met wood, and real contact cement (not the H2O based stuff) where wood met steel