Dual RL-p15 D4 Sub

[Andy Shoppa]

Here's the somewhat "final" idea for my sub project. Two RL-p15 D4's in a enclosure that's 48x38x17 external. Final internal volume has yet to be calculated, but should be somewhere between 13-13.5 ft3. It's going to be tuned around 15-16Hz via a single 8" sonotube port. Powering this beast will be an EP2500 when I get it, until then it will be my old receiver.

Anyone see anything obviously wrong with this design?

I've got a few questions on the enclosure it's self.

1) I know that MDF and BB Plywood are the "ideal" materials, but how bad would it be if I just used regular 3/4" particle board and heavily braced it?

2) Is there any reason to flush mount the drivers, other than cosmetic reasons?

3) For bracing, I was going to use 3 horizontal pieces and some staggered verticle ones, will this be sufficient?

4) On the braces, as far as cutting holes in them, is there a preferred method? Circles? Rectangles? Triangles? This will be done with a jigsaw.

5) As far as stuffing the enclosure, would lining the walls/port with fiberglass batting be sufficient?

I'll be posting pics as soon as I put down the saw.

[RandyMidd]

Are you going to wire this up for a 4 ohm load.

If so how are you going to wire it?
Drivers vc in parallel for 2 ohms then in series with each other?
or
Drivers vc in series for 8 ohms then in parallel with each other?

Just curious.

I think the MDF is easier to finish if you were planning to paint the outside because it is already pretty smooth.

Why do you want to use PB instead of MDF?

It may not cost or weigh any less to an equivalent MDF box once you're done bracing and the equivalent PB box would have a bit larger overall dimensions I'd think....

Wait for someone with more experience then me to chime in here...

[ThomasW]

If you need to use a cheap wood use thick OSB for all the structural elements and put a veneer layer of thin MDF on the outside.

[steve nn]

2) Is there any reason to flush mount the drivers, other than cosmetic reasons?

No not really. You'll actually have more meat to back them up by not going flush and it'll reduce the need for the third layer,..I'm taking it for granted that your doubling up on the baffle?

1) I know that MDF and BB Plywood are the "ideal" materials, but how bad would it be if I just used regular 3/4" particle board and heavily braced it?

I would stay away from it myself. Dual RL-p is going to come in very strong, anything you can do in the build process to coincide with this will be realized as a positive affect in the final result.

3) For bracing, I was going to use 3 horizontal pieces and some staggered verticle ones, will this be sufficient?

If your coming in at 1.5' surface area from the next brace then yes. If your going to use the particle then :boohoo: :lol:

4) On the braces, as far as cutting holes in them, is there a preferred method? Circles? Rectangles? Triangles? This will be done with a jigsaw.

No not that I have noticed. I like window myself, but it wont be quite as strong as the other options you mention...I would suggest trying to go as large as you can with the Circles, rectangles or triangles to simplify the project, if that's the way you go.

5) As far as stuffing the enclosure, would lining the walls/port with fiberglass batting be sufficient?

Yes.

[Andy Shoppa]

The problem is that the MDF isn't available at the 2 places I went to, they don't have 13 Ply 3/4 baltic birch either. The one place said they could special order me some sheets of 3/4 MDF, but the $ was way more than I thought it would be.

I can't see how there is that much difference between particle board like this and mdf
, but there must be because of the $ difference.

And Yes, I am planning on wiring each sub to 2 ohms then wire them as a 4 ohm load. Not sure if there is any difference one way or the other, this is just the way I've always done it.

Hmmm this project may be put on hold until I can find the right materials, no sense in making a box then having to re-do it.

[---k---]

The problem is that the MDF isn't available at the 2 places I went to,

You sure. Home Depot, Lowes and Menards all carry 3/4" MDF here.

If you're spending $600 on a pair of drivers, does it really make sense to worry about spending $100 versus $50 for the wood?

You don't want to have any regrets. Do the best you can now or you'll be punished with thoughts of "what-if" and wanting to redo it.

[chasw98]

You sure. Home Depot, Lowes and Menards all carry 3/4" MDF here.

If you're spending $600 on a pair of drivers, does it really make sense to worry about spending $100 versus $50 for the wood?

You don't want to have any regrets. Do the best you can now or you'll be punished with thoughts of "what-if" and wanting to redo it.

Ryan -
I have 2 Home Depots and a Lowes within 5 miles of my house and only 1 of the HD's carry MDF. The rest claim to have it but never do. So I always have to go to the "special" HD for my MDF and even then the quality varies dramatically.

Chuck

[seattle_ice]

Are there any lumber stores? The ones that sell to builders.

Look in the yellow pages. Dunn Lumber up here is where I get all my wood supplies. They are more helpful and much more knowledgeable to boot.

Circle cutouts are inherently the strongest, or the least 'weakening' to a structure in a shear/compression application.

[steve nn]

Are there any lumber stores? The ones that sell to builders.

If not, I would suggest going back to HD and having them order you some. I just went though a quagmire trying to acquire 22" sono in which one of the dealers told me that HD would special order it for me. None of the dealers would help me out unless I paid a $250 setup fee. I guess it's considered a odd size here in Or. Lots of 20" and 24", but no 22". They have the muscle to get pretty much anything you want. MDF certainly has to be a item they would be willing to help you out with.

MDF is much heavier/denser than particle. For what your using it for (dual 15" RL-p driver LLT) it's the way to go. You want your enclosure as dead as reasonably possible.

[ThomasW]

Ryan -
I have 2 Home Depots and a Lowes within 5 miles of my house and only 1 of the HD's carry MDF. The rest claim to have it but never do. So I always have to go to the "special" HD for my MDF and even then the quality varies dramatically.

Chuck

Must be terrible living in a 3rd world country.....:wink:

[steve nn]

Must be terrible living in a 3rd world country.....

:B
What cracks me up is Chucks emphases on "special" HD. There must be about five or six of them fairly close by with one a little over a mile away, and I wouldn't consider any of them special. Ok I give.. the closest HD will be the "special" HD.

Our 23rd anniversary is coming up here on the 7th, maybe the wife would appreciate an outing to the special HD?? Of course your invited Chuck, just be sure to bring your own wife.

[chasw98]

Must be terrible living in a 3rd world country.....:wink:

You should try speaking technically to the indigent population. A wrench in spanish can be a socket, open end, combination, or possibly a screwdriver! And don't even try to get into electronic schematics! My wife lived in Spain for 10 years, taught english to spaniards and she is resented down here because she speaks "castillian" spanish!

Now, shall we discuss driving?

[chasw98]

:B
What cracks me up is Chucks emphases on "special" HD. There must be about five or six of them fairly close by with one a little over a mile away, and I wouldn't consider any of them special. Ok I give.. the closest HD will be the "special" HD.

Our 23rd anniversary is coming up here on the 7th, maybe the wife would appreciate an outing to the special HD?? Of course your invited Chuck, just be sure to bring your own wife.

Hey now, the "special" HD is in an area of gated communities and BMW/Benz weekend warriors. You can buy lots of pretty things at the special HD, but they carry MDF and the others don't. Go figure.

She has put up with you for 27 years! You better go somewhere nicer than the special HD, like maybe Woodcraft or Rockler. And, yes, I would be honored to accompany you on your anniversary (would we get any guy time together that night?). I was just told this afternoon that I have to go to Michael's with her to buy thread for crocheting so she can talk to me. Claims all I do when I'm home is "play" with my speakers!!! Do you believe that? I just can't figure it out :E :roll:

[steve nn]

You better go somewhere nicer than the special HD, like maybe Woodcraft or Rockler

You always hit the nail on the head Chuck... I knew something didn't seem right about the special HD outing. We'll save that for us.:W I bet she would really appreciate Woodcraft though.

I was just told this afternoon that I have to go to Michael's with her to buy thread for crocheting so she can talk to me. Claims all I do when I'm home is "play" with my speakers!!! Do you believe that? I just can't figure it out

Now I find that hard to believe! She said that? I'm sure after your little trip, your going to be clear to go for another few days or so anyway. Listen to this..I found myself in one of those places that all the ladies go and paint plates, cups and the like. After your finished, they take your project and put it in a kiln. I was the only guy in there!..now holt it! I was with my two daughters and wife. Anyway looking forward to seeing you at the Bash Chuck, I'll give Bill W a call and see if he can make it, as to keep us in line. :T OH! bring your sub/s!

[chasw98]

Of course, there is the ever popular "High End Audio Store". There is sure to be something for everyone to enjoy. She can ooh and aah over the pretty speakers and you can salivate over the amps!

[Andy Shoppa]

Okay well I was able to find a place somewhat locally that has 3/4 mdf for $25 a sheet, which is better than the $40 something the other place wanted to charge to special order it.

Well I'm going to bring it up again, the dreaded particle board. I have some of this laying around from past projects, would it be okay to use for bracing or should I just stick with using MDF for bracing as well?

Also, what is the preferred method of fastening/joining MDF together? Glue brads and clamps? Predrilled screws and glue?

Thanks

[steve nn]

Well I'm going to bring it up again, the dreaded particle board. I have some of this laying around from past projects, would it be okay to use for bracing or should I just stick with using MDF for bracing as well?

It would be best practice to stick with the MDF. Being this is going to be such a large unit at 3/4 thick with extensive bracing, I would try to keep everything consistent. The particle would work, but it wont be optimal. Some underestimate bracing and how important it really is..your use and positioning will make a very large determination on the performance of your project. With that said, if the temptation to use the particle over-rules, being diligent in extensive will be the most important.

Also, what is the preferred method of fastening/joining MDF together? Glue brads and clamps? Predrilled screws and glue?

I like to clamp and then screw and glue myself. I don't use as many screws as I used to since I have more clamps now, but it enables me to move along with the project at a higher clip and come out with a solid enclosure. Pre-drilling is very helpful in not splitting out the MDF, but you have to be careful to drill small diameter or you wont have any meat for your screws to bite into. Admittedly any time saved with going the screw and glue will be lost with going back and filling your inset screw heads with wood putty though. It's always good to dry fit (using screws or clamps..both) first and mark your project in a way that your sure your going to understand when you disassemble and glue it up. You'll most likely catch a mistake before it's to late.

[Andy Shoppa]

Well my RLP's got here yesterday! Now to start on the box, which I will have more time to work on in the next few weeks. I'm going to be ordering some stuff from parts express, and I was wondering what t-nuts should I get? Size?

Here's a new vs. old driver pic (excuse the mess, I'm in the middle of parting out a car and my bedroom has become a mini junkyard of 69 Cutlass parts!)

[Bent]

Are you ersting that rl-p in it's surround>?

oops - edit here... my spelling sucks..

Are you resting that rl-p on it's surround?

[---k---]

1/4" screws are very very very close to fitting throught the holes in the driver, but they don't quite make it. Some people just use a drill to enlarge the holes.

So, if you are willing to enlarge your holes, get 1/4" tee nuts. Bigger is better, right.

If not, get the #10. I used #10-24 on my sub.

[chasw98]

Go to PE and look at these. http://www.partsexpress.com/webpage....7&WebPage_ID=3
I have found them to work very well in MDF. They may not hold well enough for a 50 pound driver upside down. In that case look into 10-32 or 1/4-20 t-nuts. You will usually need some wood like plywood for the t-nuts to sink into and hold properly. A lot of people get the t-nuts mounted and then use a dab of epoxy to make sure that they are held in place over time and won't "spin out" when you need to unscrew the bolts holding the driver in place.

Chuck

[SteveCallas]

Are you resting that rl-p on it's surround?

Yeah, I never understand that when I see shots of drivers positioned upside down on a flat surface. How are you not crushing the surround? That can't be good

[Andy Shoppa]

Chuck, your link doesn't seem to work.

Okay so the 1/4 if I want to enlarge the holes or the 10-32 will work as is. I'll probably go with the 10-32's.

No the sub is propped up on the other side, so I guess it's sort of resting on the surround on the one side, but it wasn't like that long.

Using these with the EP2500, will 12 ga speaker wire be okay or should I get the 10 ga?

Thanks for the replys

[Bent]

BTW, I have # 10 black hex socket screws on my RL-p too, I needed to hof the holes out just a tad to fit the # 10's

I had used # 12 wire on mine 'cause it was availalbe., but my new dual 15"er will have number 10 wire..

[---k---]

Yeah, I never understand that when I see shots of drivers positioned upside down on a flat surface. How are you not crushing the surround? That can't be good

Oops. I'm guilty of this too. I always figured that that big rubber surround wouldn't be damaged by having the driver upside down for five minutes or so while I tried to get it wired and then lifted into place.

I guess this should go into the FAQ.

[WillyD]

Oops. I'm guilty of this too. I always figured that that big rubber surround wouldn't be damaged by having the driver upside down for five minutes or so while I tried to get it wired and then lifted into place.

I guess this should go into the FAQ.

I personally wouldn't do it, but I don't see how it could cause any damage (well, not for short periods of time anyway). The surrounds aren't exactly made from woven silk.

[SteveCallas]

The surrounds aren't exactly made from woven silk

Yeah but my Avalanche 18s are ~45lbs each :M

[Andy Shoppa]

I ordered the EP 2500 along with some t-nuts and terminals from parts express on Friday night so those are on the way. Got the chance to work on the box for a few hours this week, got most of the pieces cut. Also picked up a router, so hopefully a few practice runs first, then driver and port cutouts will go smoothly. All I really need to do is cut the holes in the braces, and the holes for the drivers and port, run a flush-trim bit around it and then take it all apart and do final assembly in room.



Here's a few pics I took before the camera battery ran out:

[SteveCallas]

I'd also use at least one vertical brace :T

[Andy Shoppa]

HAhaha yeah I've got 8 pieces cut for verticle braces, but didn't get around to putting them in yet.

[steve nn]

Hey Andy,

Could I bother you for a little update on your box dimensions including the location of your baffle and port?

[Andy Shoppa]

Final external dimensions are 49x38x17.75. It's done, but it's not finished, still unsure if I want to try and veneer it or just paint it. It sounds better than what I had, but I've yet to mess with eq at all, so hopefully I can get it sounding better. I've had the clip lights on the EP2500 on several times today while testing it out, and it doesn't really seem like the speakers are really moving that much. Maybe have to re-check my wiring or something.

Anyways I think this sub is just the begining of my DIY projects, but no more for at least a few weeks, I'm still trying to hose off all the MDF dust off the back side of the house.

[nick77]

It seemed my driver needed a little break in period to get it moving.

[Andy Shoppa]

That's a good thought, I'll give it some time.

holy freakin screws!

[WillyD]

Good god...that cabinet has to be strong. Nice work!

[SteveCallas]

I've had the clip lights on the EP2500 on several times today while testing it out, and it doesn't really seem like the speakers are really moving that much. Maybe have to re-check my wiring or something

8O Clip lights on several times during testing? Unless you are testing at ~120db levels, you shouldn't be experiencing any clipping. I'd definitely recheck your wiring. What were you shooting for as an effective volume and what is the length of the 8" diameter port?

[steve nn]

I've had the clip lights on the EP2500 on several times today while testing it out, and it doesn't really seem like the speakers are really moving that much. Maybe have to re-check my wiring or something

Yes as Steve says. I'm having a real hard time comprehending this if everything is setup correctly. To get the EP2500 to clip with my dual driver RL-p D2 600 liter unit takes more foundation shaking than I or our neighborhood is willing to put up with, we're talking 119-120dB in a very leaky 2880.

Your bracing looks awesome though. If you paint, your never going to hide all the screws regardless of what you do in prep. If your in a room with no sun you'll be ok, but it'll still take a extremely good amount of work. Veneer, vinal or some sort of textured application would be my suggestion.

[Andy Shoppa]

I don't have the best test equipment, a radio shack spl meter and a few cd's that have some pretty decent bass, along with a couple of dvd's, and a cd of test tones. But yes my radio shack spl meter was reading in the 115-120 db range with the clip lights on. Now, don't get me wrong, that's louder than I'd ever need, but still seems like the drivers had quite a way to go before reaching 24mm xmax.

Yes on the finish as well, there is no way I'd ever want to paint this with a glossy paint, it's far from straight and would look terrible. I'm leaning towards something like a roll on flat black paint or a bedliner type material.

[steve nn]

But yes my radio shack spl meter was reading in the 115-120 db range with the clip lights on.

I'm sorry for asking this, but it has to be warranted out. You are speaking of the red clip lights and not the green input lights correct? Like I said I'm sure you are but I have to ask. I can barely bottom a single D2 RL-p with the EP2500, but it doesn't have the juice (nor is it rated) to bottom my dual on most material from what I can tell. If you put your drivers in a sealed enclosure you would see the full 24mm I guarantee. What tune did you shoot for Andy?

[SteveCallas]

but still seems like the drivers had quite a way to go before reaching 24mm xmax.

Again, what effective volume did you shoot for and how long is the port? Before the 4th order rolloff, the point at which you use the most excursion will be in the low to mid 20hz region, and I'd estimate with full rated power you are getting up to ~20mm excursion. That's a good thing, as you don't want to have to reach the limits of the drivers' excursion capabilities if you don't have to, especially when you are already getting up to 120db - that means your distortion levels are still going to be fairly low, though the amp is probably starting to put out all kinds of garbage since you are clipping it.

Something still seems off here though. You were measuring 115-120db levels from how far away? Was this just from the sub or with your speakers on as well? What media were you using to reach the 115-120db levels?

[---k---]

It seems like several people (myself included) have just not gotten the expected output from an RL-P15 sub at first. For me, it took pulling the driver, unhooking everything, hooking it back up in the same way I thought I had it before, and then trying agian. After that, it had the output.

Maybe my wiring was wrong, maybe the driver just needed a little bit more time to break in, I don't know. But, check your wiring and give it a bit of time, and then see what happens.

[Andy Shoppa]

According to my quick math here, I'm looking at an effective 12.4 ft3 or 350 liters, after taking in consideration the port, drivers, bracing and so on. The port is 8" i.d. and is 38 inches long, which according to WinISD is about a 15-16 hz tune, which is what I was shooting for.

As far as the wiring goes, I wired both coils on each speaker in series, then hooked the 2 speakers together in parallel. It's hooked to the EP2500 mono.

The 120 db that I was reading is in the listening position in my room, which is quite small at only 170 ft2 or 1400ft3, so it's about 15 ft from my sub to where i was measuring. The material was just some rap music that has some strong 20-30hz material. It was with the sub and my mains, but the mains are only getting 60hz and up.

Yeah it's the red clipping lights, not the orange signal lights. I'm not that out of it, hehe not yet anyways.

[WillyD]

Why not wire the coils on each speaker in series and run each driver on its own channel? Just a thought.

[SteveCallas]

According to my quick math here, I'm looking at an effective 12.4 ft3 or 350 liters, after taking in consideration the port, drivers, bracing and so on. The port is 8" i.d. and is 38 inches long, which according to WinISD is about a 15-16 hz tune, which is what I was shooting for.

Hmm, did you experiment with modeling this design at all before building it? That enclosure, in my opinion, is far undersized - your response is basically a continuous shallow rolloff, not really optimized for such a low tune. I apologize for not chiming in on this thread earlier, I figured you were being taken care of. Are you experiencing any audible port resonances with the port being 38" long?

so it's about 15 ft from my sub to where i was measuring

Realize that every doubling of distance results in ~6db loss, so getting 120db at 15' is actually pretty impressive all things considered. At this point, I'd consider shortening the port.....your enclosure isn't really optimized for this sub to be a bottom troller in the first place, and it seems like you might prefer the punchier sound of a higher tune. There is no clear answer here though, as I'd make that 8" diameter port only 17" long for a ~21.8hz tune in 350 liters, but then your port velocity gets high, as you should then ideally be using a 10" port instead of 8", but I don't think you can change that now. You'd also probably need a highpass at 15hz, but then the output you would have gained is reduced. Man, I don't know what to tell you. I'd have used 350 effective liters for just ONE RLp15 D4 ops:

[Andy Shoppa]

Yeah I modeled it, and I know about the roll-off, but I was sort of limited on the size of the encosure. That and even at 560 Liters, at the same tune, shows only 2 db more output at 20hz and 3db at 15hz.

No audible port noise what so ever, as a matter of fact I really do like the way is sounds. I watched a little bit of WOTW last night, and even at only 90db it was rattling windows and doors. I was just concerned about not reaching the full output potential of this set-up, but it seems like from what I'm hearing here that I am.