My First Sub

[ThomasW]

I've been wondering what was best to use to fill the countersunk holes and such. Now when you say Bondo, do you mean something like this http://www.lowes.com/lowes/lkn?actio...00075127-20052
which is more like a dry wall putty, or do you mean the real two-part epoxy?

I've not seen that before. The stuff I use is the 2 part auto body filler.

[noah katz]

Right, Bondo is 2-part polyester, resin plus catalyst.

[---k---]

I'm making some progress. I went through my first 16oz bottle of Tightbond last night while laminating all the sides. I actually ran out before finishing. I'm going to have to pick up another bottle tonight. The garage is freaking freezing! The panels are drying inside the house. I'm going to try and get them all laminated this week, so that Monday after Christmas, I can assemble the box. Good times!

[Bent]

I didn't use titebnd, just plain old yellow wood glue on my AS-15, but I used 3.5 litres of it.

[ThomasW]

Ryan,

Sounds like you're in the groove ..... :T

[---k---]

Ben,
3.5L ??? That can't be right. That much glue would fill up my whole sub.



Got a question on routers. Last time my dad was in Chicago, I had him bring his router with to borrow. Unfortunately it is a fixed base model. I could probably borrow a plunge router, but I don't like borrowing tools from other people. I'm thinking about just buying myself a cheap plunge router. Lowes has a couple too choose from. A Black & Decker $69 plunge router, a $100 Skil 2 1/4hp fixed/plunge, and a $175 Hitiachi 2 1/4hp varible speed fixed/plunge.

The B&D at $69, I would feel I got my money's worth out of it and not care if I never used it again. I wouldn't mind having the both the fixed/pluge abilities of the $100 Skil, but that is almost to the point where I would need to find another project to use it on. I really liked the Hitiachi (I've always liked Hitiachi tools for some reason). I've almost convinced myself to just get the Hitachi and never have to worry about the router crapping out on me while cutting through 2" of MDF. But, I'm going to need to find future projects to justify a $175 tool. (I'm sure you guys can help there. hhehee)

Do you guys think the $69 B&D would be up to the job, or should I just go all out and buy the Hitachi? Or any other recomendations? I've never done Harbor Freight, but they are local, so that is an option.

(and yes I could do the cuts with a jig saw, but my jig saw I got from my grandfather and is a wimpy B&D that is probably 20 years old. I would have to buy a new one of these. Might as well just buy the right tool.)

[cjd]

1. I am glad to hear you brought the panels in the house to dry! It's MUCH too cold for proper glue joints right now.

2. Best deal I've seen is the ~$150 3HP Hitachi Amazon has had for a while (though I did not check just now to see that they still have it). I have a 2.25HP Bosch (got plunge/fixed bases). The similar Porter Cable package is also excellent, both just over $200. Hitachi's offering in this range is generally well reviewed I believe. I do not belive in cheap tools, but that's me.

3. It won't fit your timeline in all liklihood, but you're welcome to swing up to Gurnee and we can take care of your routing needs. I expect I will be home on Monday, Dec. 26th - for that matter, I believe I will be working from home that whole week (all full time employees get the week off - us contractors get the option).

C

[---k---]

CJD,
I didn't realize that you are in Gurnee. It would be really cool to get some local help, and I would love to check out your gear sometime. I really don't have any referance points for what real big bass should sound like, so that would be cool.

Monday could work, if you don't mind routing the driver holes without the box being assembled, or maybe latter in the week. I was planning on taking Thursday and Friday off. I'll pm you my phone number, and we can go from there.

[Paul H]

... The garage is freaking freezing! The panels are drying inside the house. ...

You might consider one of these at the link below to take the edge off the cold. It's not a full-bore space heater, but it's cheap and easy to set up and will get a garage that's just below freezing to just above freezing. That'll let you keep the wood in the garage rather than the living room.

http://www.leevalley.com/wood/page.aspx?c=2&p=44590&cat=1,43456,43465

Paul

[---k---]

I'm just going to line the inside of the box with the steel. I figured that I would cut the steel about 1 1/2" smaller than panels, use contact cement to adhere it, and then assemble the box. I was only planning on doing the top, sides, and rear. I don't see a need to put steel on the bottom or the baffle. Is this correct?

Also, I'm assuming that since Thomas offered this as a possibility, that it won't have a negitive effect on performance. But, I'm having a hard time accepting the inner layer of the box be steel. Won't this give the sub a tinny sound? Do I need to be extra carefull in any step here? I wasn't extremely presice with my previous cuts, so I need could probably use some warnings if needed.

[SteveCallas]

If it were me, I'd probably use short screws and screw the steel into the MDF in addition to using contact cement, just to be sure it will never move.

[ThomasW]

Ryan,

The steel won't have a negative impact on the SQ of the sub. It will add mass damping to the enclosure, that's always a good thing

The only surface that doesn't need steel is the front baffle board. All the other surfaces should have a layer of steel.

Use both contact cement and screws.

[Mark Seaton]

But, I'm having a hard time accepting the inner layer of the box be steel. Won't this give the sub a tinny sound? Do I need to be extra carefull in any step here? I wasn't extremely presice with my previous cuts, so I need could probably use some warnings if needed.

Echoing what Thomas and others mention with respect to the contact cement, be sure there is glue between the entire contact surface to insure there won't be any rattling and that any structural benefits will be maintained.

I would point out that it's pretty easy to get caught up in little details of things like exact bracing methods (I know I've done it!). In many cases the real concerns should first be placed on insuring there are no leaks, rattles or gaps where braces contact. Don't get me wrong, a good box is of definite value, but there are many ways to get there. Some like 3" thick walls, and some employ bracing on single layer construction. I know that Earl Geddes has posted that many who post measurements of panel resonances do so without correlation to resulting acoustic output nor any relevance to audibility. If you search through Linkwitz's website you will find info on some general observations about resonances in panels with a given unbraced area. I believe he notes that it's not all that difficult to get 3/4" MDF to not have resonances until above 1kHz or so. On the flip side, there is SVS which has relatively little bracing in their box subwoofers in comparison to most DIY expectations and audiophile expecations. Somewhere in between the extremes I'm sure there is some reasonable balance between efforts, costs, and benefits.

Ryan, be sure to drop me a line when you get the subs up and running. It should be fun to compare to some other things I have around the house.

Best Regards,

[collo]

I'm thinking about just buying myself a cheap plunge router.

I bought a cheap plunge router four subwoofers ago and have been very pleased with it.

At the time I bought it, I didn't know if I would be building more speakers, so a small outlay was justified, particularly as it came with a range of bits.

The plunge action is a must for cutting circular holes for drivers and ports, so I would not recommend buying anything that didn't have this facility.

A small router is easier to get inside a partially built box if you need to cut slots for bracing etc.

I like to user a rollover bit to cut flares for my ports. This is the one area where I wish I had a full sized router.

The rollover bits available (at least in Australia) are determined by your router size. For my router, the largest flare radius I can cut is 13mm, which is not always enough. If you go for a full sized router, you'll be able to get up to a 30mm radius rollover bit.


regards
Collo

[---k---]

Steve,
Thomas suggested the screws also. I got some self tapping metal sheet screws and was planning on adding a few.

Thomas,
Thanks for answering my fears.

Mark,
Great to see you here! I've been using a foam brush to spread out the glue while laminating the two layers of MDF. It seems to work well. I will do the same with the steel.

As for bracing, I'll look though the Linkwitz's site again. I did it once a while ago, but I was looking at the Transform stuff and must have missed the comments about bracing the boxes.I still having a hard time beleiving the need for all the stiffness in the boxes. But, this week I received a DVD from B&W speakers and was watching it, and they showed the bracing in their 800 speakers - wow! And those are ported speakers with I'm guessing a lot less pressure inside. Hometheaterhifi.com also has an article about a tour of the Paridigm factory, and they have photos of the bracing in the Sig series. Again, wow. So, there must be more for me to learn!

I will definitely give you a shout when I get these bad boys finished. I would be honored to have you listen to them and give me your impression (And anyone else here, you just have to come to Chicago).

Collo,
Thanks for that. I'll take another look at those routers at Lowes and probably pick one of them up.

[ThomasW]

Ryan,

Regarding routers. Amazon is your friend. The big Hitachi will last a lifetime and has enough power to pull a plow. Unfortunately it has zero dust collection capability. The DeWalt DW621K, while a bit smaller than the Hitachi, has amazing dust collection abilities when used with a large shop vac.

If you go up and work with Chris D., you'll see the astounding amount of dust a router generates. Whenever possible I route outside. When that's not possible I only use my 621, and even with it's vacuum capabilities I drop-cloth off an area in the basement when using it.

[---k---]

I was just looking at this: http://www.vikash.info/audio/xls10/construction.asp

He installs the driver so that it is tight against the bracing. Is this recommended?

[cjd]

If you go up and work with Chris D., you'll see the astounding amount of dust a router generates. Whenever possible I route outside.

As do I. In fact, MDF *only* gets worked on outside under any condition now. But yes, they do in fact generate a lot of dust.

C

[ThomasW]

He installs the driver so that it is tight against the bracing. Is this recommended?

Never done it, but have seen it done before.... The REALLY high-end speaker companies do it (Avalon Acoustics for example). Not sure if it's worth the hassle.

What's ironic about that project is that he fails to give the amp it's own enclosure = bad. Other than that, his cabinet skills are exceptional.

[Mark Seaton]

-k'-

I'm sure that does help in securing the driver, but two things you have to watch for:

1. Don't impede airflow from the pole vent. You can get some odd noises if you place a flat surface too close to the pole vent. Worst case is in open air, which is easy to test, and as the box gets smaller, the problem can reduce some. It looks like he did offset the backing brace to account for this.

2. Back to rattles and how things fit. I would only do this with some closed cell foam tape or pad on the contact points. I would want something compressable to keep things snug. While it should be obvious, I would only do this when using T-Nuts for driver mounting.

Sigfried Linkwitz has some stuff on his website about mounting via the magnet/basket which is after a little different goal, but worth taking a look at. I would think the best way to compress against the magnet would be to use a brace with a hole enlarged to accomidate the pole vent and probably some stand off ring to make contact with the back plate. Depending on the woofer and use, the back plate can provide some heatsinking, so I wouldn't go too nuts with too much contact area if it was a truly flat back plate.

[noah katz]

I agree with Thomas, don't think it's worth the hassle to brace the back of the driver.

There are two conditions which might warrant it

1) The driver is on a large panel so that the mass of the driver on the panel's compliance gives a low resonant freq

2) The woofer has a stamped basket and will operate at a freq high enough to excite the resonance of the magnet assembly flexing the spokes

[---k---]

As do I. In fact, MDF *only* gets worked on outside under any condition now. But yes, they do in fact generate a lot of dust.

C

Ouch! It is cold out there, This might prevent us from hooking up!


btw, I pm'ed you my phone number if you missed it.

[cjd]

Nah, it's supposed to be 40 on Friday (the 30th or whatever it is.) I got the phone number, but have had no time available to use it during the hours you outlined.

C

[---k---]

Well, a bit of an update.

I spent all day working on my enclosures. I got a lot done, but no where nead as much as I thought. Things are taking about three times long as I had expected. A lot of that has to do with cleaning up my poor workmanship.

So, I got out my Dad's fixed based router and cleaned up all the edges today. Wow, what a wonder tool a router with a trim bit is! I used the trim bit to clean up all the edges where the two layers of MDF weren't perfectly that same. Where edges weren't straight, I screwed down a peice of 1x4 and trimed both. This was really slow, because I only had a 1" trim bit, so I had to do four or more passes. But it all came out real good. I got all the edges flush and square.

I got the steel all cut for one sub. While it sat under a stack of MDF to flatten out, I worked on the bracing for the other sub. I got the other sub test fitted up. Then I measured the opening and cut the MDF peices a hair bigger. I hand sanded each peice untill it fit snugly. I then marked out my patern on the bracing and made the cuts with a drill and a jig saw. The bracing was then wood glued and screwed. I used 1/2"MDF, which made screwing a little difficult. I split the MDF in a few spots, but it seams solid. I poured some glue in the gaps, so it should all be good.

I put a hole in the center of my bracing, because the end of my driver with the bucking magnets is going to be very near the center of the box. I didn't want to be slightly off, and have problems getting the driver in. This took care of that.

I'm really happy with how things are progressing. This is where I'm at with one:







Tomorrow, I plan to get the bracing for the other sub done, then take them apart and glue the steel to the sides. I should be able to do a final assemble of the boxes later this week. I'm meeting up with Chris on Friday to cut the hole for the driver. After that, I should be listening to these bad boys!

[ThomasW]

Progress is our most important product.... :B

Looking good...... :T

[SteveCallas]

Looks good - did you give any consideration to staggering the two layers at the corners instead of stacking them so that it would be harder to have any leaks?

[noah katz]

"Things are taking about three times long as I had expected. A lot of that has to do with cleaning up my poor workmanship."

Don't feel bad; I'd say my AER (actual to expected ratio) is double that.

[---k---]

Steve,
I had actually planned on doing it that way originally. I was going to do it more because my joint strength would be much higher. But, with my poor woodworking skills, it just wouldn't have worked out. This way is much easier.

[---k---]

More progress today!
I got the bracing done for the other sub and all the steel laminated to the sides. I need to add a few screws and sand down the bracing joints to get rid of the over glue.


I'm going to try and get the box glue together tomorrow night so it will be good and dry by the time I try and transport them on friday.

Here is what the inside of my box will look like:



I'm hoping I got this right. Now, I just plan on stuffing the box with R30 or whatever, and not adhering anything to the sides. I've asked this several times, and I believe that I keep getting that I'm fine, so...

Getting there.
(edit: oh, and I know that the steel isn't going to be extremely effective this way, but shielding is really a secondary concern.)

[cjd]

You did say before you're not putting steel on the baffle, right? 'cause that's not something I want to be routing through!

Lookin good!

I got a new 1HP dust collector for Christmas I can attempt to use on this project.

C

[---k---]

Yeah, there is no steel on the baffle. And, you'll notice that I left a spot on the back panel for the terminal box.

[ThomasW]

Well that's doing the steel the hard way.....

I'm fundamentally lazy, so I'd just use whole pieces on each surface and attach the braces to the steel with liquid nails....

[---k---]

Thomas,
I had considered that, but after going through the trouble of making COOL bracing, I wanted to make sure that it would be rigidly attached to the sides and prevent the panels from bowing out. With the contact cement not being structural, I wasn't sure that would be possible. So, the hard way it was.

[---k---]

I'm an idiot. I just realized that I only ordered one terminal cup for my two subs. I ordered one of these from Parts Express:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-311

They want $6.60 to ship a $3.40 part.

Is there any place that I can get one of these local? Radio Shack has this one: http://www.radioshack.com/product/in...entPage=search

Is it worth ordering from PE? Or should I just get the one from Radio Shack (or somewhere else) local?

Silly as it may sound, I kind of want them to be the same. The one from Radio Shack seems slightly less quality. And, I figured it would be a lot easier to cut a perfect circle with a router and a jig than to cut a square with a jig saw -- I actually don't think my jig saw would be up to cuting 1 1/4" MDF.

Thoughts?

[ThomasW]

Well you don't need to cut a perfect hole for either since the flange covers the hole.

As for cosmetics that's your choice, I don't know how many people are going to be checking the back side of the boxes .....

[cjd]

I do believe I have some binding posts hanging around - they're this model from PE.

May work just as well since you won't have to back the terminals, or something like that. Certainly won't do to have just a thin plastic cup between the sub and the outside world. Can below-surface mount them even so they don't stick out.

C

[SteveCallas]

-k-, you're going to be purchasing some new speakers soon right? I'm sure you can easily find a few more things to pick up from PE - speaker wire, banana plugs, spade rings, a Y cable, etc. That way, you won't feel as bad about the shipping :T

[collo]

I made some recessed connectors as suggested by cjd.
The plastic binding posts can't really be done up nice and tight - I woud suggest the metal ones if you're going down that road.

As usual, some pics and a little story....

http://www.users.bigpond.com/bcolliso/speaker-terminals.htm

regards
Collo

[---k---]

Steve,
Yeah, PE told me the other night when I was looking at that D-cup that if I only spent $95 more, I would get free shipping!

I'm sure there are a few more things I can order, I just won't know what till I get there. My last order, I tried to buy all the extra bannana plugs and stuff to get the free shipping.

I'll probably just take Chris up on his generous offer, and see what we can come up with.

[cjd]

someone's got holes.

Also forgot binding posts. Ahh well. Pick up some Sound King 12ga wire while you're shopping at PE.

C

[---k---]

I got about five miles on the tri-state when it hit me that I forgot the binding posts! Doh! Hello, PE....

Chris and I had a good time. He was very gracious and did all the work for me. He was able to do it in no time flat. Afterwards we listended to a few of his systems. First up was his IB - very impressive. It shook his whole front wall, which the IB is mounted to. :T If for a second I thought that the wall was load bearing, I would have been leaving the room quickly - luckily it isn't. Chris played a mix of things, and it was very to me that it was able to hit low, very cleanly; which is something my current sub can't do. We also watched a few bits from the Incredibles. His IB could so prussurize the small room. I could feel the futon we were sitting on moving beneath me - very cool.

I also got to listen to his big bad boy speakers. They also were impressive. They had great imaging and big full body sound. I put in some Dave Mathews and Live, and was impressed. His speakers were more out in the middle of the room than I'm used to (mine are about 12" off the wall w/ a tv between) so it was really cool the way that his speakers gave a ton of depth to the imaging. They weren't as bright as what I think I prefer, but I think they are speakers you could listen to all day. With no sub, they still had tons of bass, that was very clean. Oh, and they looked good to.

We also very breifly listened to his MTMs. Chris tells me that they are around $300 to build, and boy was I impressed. They didn't have as full of sound as his big boys, but they filled the room with a very light airy sound that I enjoyed. I would be happy to have those in my house.

Well done Chris.

Anyway, back to my sub. Got the holes done, so now all I have to do is assemble the box and trim up the front. I picked up a 2" trim bit on my way home from Woodcrafters, unfortunatly it is a 1/2" shank, and the router I borrowed from my Dad won't take it. I guess I'm going to have to break down and buy my own router. I've been dragging my feet on it, and now am regreeting it. I should have bought the Hitatchi from Amazon, but ... I go take another look at them tomorrow at Lowes. The Hitatichi combo kit for $174 is still a good deal, and I think that there is a rebate for a free detail sander on it. :T
I think if all goes well, I should be listening to at least one by Monday - depending on how long I need to let glue dry.

[cjd]

With that size flush-trim bit, you don't want a 1/4" shank anyhow. I go 1/2 for everything but spiral cuts or really small detail bits. I've broken too many 1/4 shanks.

C

[Dennis H]

I've broken too many 1/4 shanks.

Yikes! I was only a carpenter for 20 years or so before I moved on to other things but I never broke a router bit. Methinks someone needs to learn the old "touch" thing.

[cjd]

Yikes! I was only a carpenter for 20 years or so before I moved on to other things but I never broke a router bit. Methinks someone needs to learn the old "touch" thing.

I broke 1. That's too many in my book. It was a flush trim bit and the guide bearing toasted about a second before the shank split. I lost two guide bearings from that company, so I think it's not so much a shank size thing but it did make me realize it was worth looking to 1/2" shank whenever possible.

Hard to say for sure what caused it. It was also fairly early on in my router "career" so it's entirely plausible it was something I did.

C

[---k---]

I got a quite a bit more done yesterday, not quite as much as I wanted, but I guess that is how it always goes.

Anyway, I went to Lowes and bought the Hitatchi combo router to use to trim up the 2" front baffle. Unfortuantely, the first one I got had a bad collet, so I had to take it back for the last one they had. When I got it home, I assembled the boxes and mounted the front baffle to trim it up... First oops. I had measured all the sides to make sure they were the correct size, and I thought I measured the fronts, but guess not. The both were about 3/8" too long, but about 3/8" too narrow. Ughhh. I just centered them up, trimed the ends, and figured that I could take care of the sides with a couple of layers of Bondo.

Second oops happed in the triming. I should have practiced with my new router a bit more before tackling the fronts. I got it off balanced a few times and dug into the top in a few spots. Again nothing a little sanding and bondo can't fix. On one of the backs, I had taken a couple of screws out, and the board sliped, and I got a nice J into the back. Oops... This router is so much more powerful than my Dad's craftsman that I was using, and with the big 2" trim bit, it was real easy to make mistakes fast. Oh well....

I got one of the subs inside, and glued up 3 sides, the back, and the bracing. I let that to dry for about 6 hours, and then removed the side and added some liquid nails along the edges of the bracing to make sure it was held tight, and used Silcone sealant along all the joints. I gave it another layer of sealant this morning.

Here is a tip for all those out there that I haven't seen anywhere: DO NOT BUY CLEAR SEALANT! I couldn't see it in the box. and I bought the 4 pack. ooops.

The last side got glued this morning, and is drying. So all I have left to do is drill the holes for the driver, add the T-Nuts, and then glue it down, and one will be done.

I'll post photos later this afternoon.