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[JohnGeorge]

i think i have to start a new thread (which i already did) since it's a different topic altogether and will help a lot of other DIYers (in my opinion).

as you can see from my previous thread, i have decided to go with either B&C S18AN or S18CN.
Link: http://www.bcspeakers.com/resources/suggested-designs/

i have a lot of obstacles and setbacks and need your help with the following -
1. only 12mm birch ply is available in the market (no 18mm) - so can i use 12mm birch ply + 6mm other wood. or go with 18mm of MDF or any other commercially available wood.

2. the reason I'm still deciding between 18NW100 (S18AN) or 18SW115NEO (S18CN) is because there are only a few amplifier brands available readily, for others shipping cost will be an added expense. they are QSC GXD 4&8, QSC GX3,5&7, Yamaha P Series, Behringer inuke and EP series & Samson MXS & SXD Series.
              Considering i will build 4 of either 18NW100 X 8 ohms (S18AN) or 18SW115NEO X 8 ohms (S18CN). but    mostly will use 2 and sometimes 4. so i need suggestions as to which amp will be the best suitable on both occasions for both designs.

3. is it possible for someone to make a detailed sketch of S18AN & S18CN. Since, I'm not clear with a few details on the designs.

4. please suggest if i have made the right decision for the below mentioned spares. i'll be ordering almost everything from parts express and if someone has a suggestion or a different product that is better  -
a. Parts Express Speaker Gasketing Tape 1/8" x 3/8" x 50 ft. Roll
Link: https://www.parts-express.com/parts-express-speaker-gasketing-tape-1-8-x-3-8-x-50-ft-roll--260-540
b. Acousta-Stuf Polyfill Speaker Cabinet Damping Material 5 lb. Bag
Link: https://www.parts-express.com/acousta-stuf-polyfill-speaker-cabinet-damping-material-5-lb-bag--260-330
c. Penn-Elcom W9000Z 4" Swivel Caster w/Blue Wheel 330 lb.
Link: https://www.parts-express.com/penn-elcom-w9000z-4-swivel-caster-w-blue-wheel-330-lb--262-270
d. Angled Metal Speaker Cabinet Input Dish
https://www.parts-express.com/angled-metal-speaker-cabinet-input-dish--262-838
e. Speaker Mounting Top Hat for 1-3/8" Tripod Stand Steel
https://www.parts-express.com/speaker-mounting-top-hat-for-1-3-8-tripod-stand-steel--245-012
f. Penn-Elcom H1070 Large Recessed Steel Handle
https://www.parts-express.com/penn-elcom-h1070-large-recessed-steel-handle--262-315
g. Penn-Elcom F1686 Rubber Cabinet Foot 1.57" Dia. x 0.61" H
https://www.parts-express.com/penn-elcom-f1686-rubber-cabinet-foot-157-dia-x-061-h--260-770
h. Peavey Black Tolex Covering 54" x 60" Roll
Peavey Black Tolex Covering 54" x 60" Roll

Grill, glue, brace & nuts will be bought locally. pls add if I'm missing something because i want to make sure that everything is shipped at once.

i know this is a lot that I'm asking for. but, i really need you help since most of the stuff i haven't really had any experience with.

Thankyou

[Rick Powell]

I would not recommend trying to make your own ply out of 2 sheets, but if you have the correct glue and clamping it can be done.  I would research this further.  MDF will work fine, but the cabinet will be substantially heavier and will be more susceptible to water damage.

The need for damping material with a sub is probably not there.  Most subs go without it and work fine.

Tolex covering is OK but time consuming.  A Duratex or similar heavy duty paint coating should be good.

[Rick Powell]

http://forum.woodenboat.com/showthread.php?5479-Gluing-thinner-plywood-sheets-to-get-thicker-stock

Found this info on making thicker plywood out of 2 thinner sheets in a boat building forum.  They seem to recommend covering the entire board surface of one of the plies with a roller using a polyurethane glue or epoxy before assembling the plies, and mention several methods of clamping or drawing the two boards together.  A good even weight atop the plies after gluing should be sufficient and make sure the surface is entirely covered with glue/epoxy with no voids.

[Stephen Kirby]

I wouldn't use MDF for something you have to move around.  While the 13 ply stuff is best, a good marine grade standard ply would be better than thin material.  If you can get it, I also like mahogany ply for speaker cabinets.  I've never built subs from it since I can get the Baltic birch but I really like it for tops and guitar cabs.  A bit lighter and has a nice warm sound.

Used the stuff from Parts Express for lots of projects and it's fine.  If you can rout out recesses for things like the handles and pole cup, it will give your project a nice finished look.

Instead of Tolex, if you can get this stuff shipped to you it will be more like a professional cabinet.  http://store.acrytech.com/Speaker-Cabinet-Coating-DuraTex-Roller-Grade-Black.html  They sell special rollers but I find that a regular short nap 6" roller gives a finish very similar to the JBL products.  And it's easy to do.  Sand and seal the cabinet like you would for any other finish and just roll a couple coats on.  It dries fast too.  Although it gets maximum toughness after about a month post cure.

At the performance level that those drivers can attain, I wouldn't bother with the Behringer or Sampson amps.  QSC or Yamaha should be fine.  Get as much power as you can afford so you don't drive the amp into clipping.  Those drivers can take just about what any regular amp can practically dish out.

Good luck.

[JohnGeorge]

thankyou Rick & Stephen

@Rick - ok so the damping material is out and also the tolex.
in comes duratex or similar heavy duty paint coating. (i'll see what is available locally, then make a decision).

@Stephen -
i am thinking that i wouldn't go the 2 sheets (12mm + 6mm) way. since birch is available now, but it may not be available in the future if i decide to build more.

what is available-
marine ply (brands - sumac and marineplex) and mahogany sapele  is available. they also have something called block wood. are any of them better than MDF. or can someone rate them in order?

[JohnGeorge]

@Stephen -
"If you can rout out recesses for things like the handles and pole cup, it will give your project a nice finished look."

i did not understand this part. do you want me to use something else? a link will help. Thanks and yes, i want a nice finished look.

[Tim Weaver]

If you have trouble getting the duracoat, I would do regular black oil-based enamel before I did tolex or carpet. Paint is easy to touch up, and much easier than carpet to keep clean. Plus its cheap.

The router comment is just saying this: flush mount all you hardware. Don't just screw it to the surface if the cabinet.

It will look more professional and it will last a lot longer if everything is flush mounted.

The one thing I don't see in your parts list is metal corners. Some people use them and some don't. But if these cans will see serious use (and abuse) I would add some metal corners to protect the wood.

[Bill Hornibrook]

If birch is unavailable, just use the best 18mm ply you can get your hands on. Look for void free and highest ply count. This is not a disaster and will definitely work.

I like tying opposite walls together with braces. They don't have to be big, and in a sub the subtraction from internal volume is minimal. Just glue and screw them onto your wall braces - side to side, top to bottom. They are not in the B&C plans, but will really help tighten up a cab using less than optimal wood.

Those rubber feet will bust off in no time. i put bolt-on refrigerator glides on all my subs, which are practically indestructible. Here in the US they are available in any large hardware store - dunno about your country.

If money is tight, an iNuke 6000 isn't all that bad on subs. I've done it - not my favorite, but it works. It is much better than a Yamaha P7000s - which I also have. My current sub amp is a Peavey IPR2-7500 which I highly recommend if you can get them reasonably. They are very reasonable here in the US.

[JohnGeorge]

Thanks Tim and bill

Firstly some good news,  it seems like someone will order a few sheets of 18mm birch for me for a small price and can order again if I require more. Sounds good but I hope they actually can.
 
And finally I understood what rout out or flush mount means I was definitely going to do that. Just did not know the term used. Thanks tim for clarifying.

@Tim - yes, it seem that even duratex is not available . The person at the paint shop counter suggested enamel.

And I never liked seeing metal corners on speaker cabinets so for now I think I'll not go with that. 

@bill- thank you, will certainly go with your suggestion to use glides and I did go through your ipr2 7500 thread and looks like that's what I was looking for.

But a quick question. It says that it does 3750W RMS/ch at 2 ohms and 2020W /ch at 4 ohms.
      I was thinking of going with 18sw115 the 4ohms version. So that u can use 1 amp for either 1 sub per channel at 4 ohms or 2 subs per channel at 2 ohms.
Is that a good idea or its not advice able to drive that amp at 2 ohms?  Or is there something else I need to think about?

[Bill Hornibrook]

@bill- thank you, will certainly go with your suggestion to use glides and I did go through your ipr2 7500 thread and looks like that's what I was looking for.

But a quick question. It says that it does 3750W RMS/ch at 2 ohms and 2020W /ch at 4 ohms.
      I was thinking of going with 18sw115 the 4ohms version. So that u can use 1 amp for either 1 sub per channel at 4 ohms or 2 subs per channel at 2 ohms.
Is that a good idea or its not advice able to drive that amp at 2 ohms?  Or is there something else I need to think about?

Personally I keep it at 4 ohms a side. I drive two 4 ohm B&C 21SW152s with it - one per side. There are times (like last night when I was DJing an outdoor 4th of July event) when the limit lights were flashing, but it didn't trip a 20 amp circuit. Since I don't run a distro I may not be so lucky if I were to run it @ 2 ohms. Plus running any amp under 4 ohms kind of scares me.

Also, I believe it's 2750 @ 2 not 3750. You don't gain a lot.

[Stephen Kirby]

This is an oldschool thing but for a covering, something we did back in the day was laminate fabric onto the box.  A corse weave somewhere between canvas and burlap.  Slightly open weave.  Applied with white woodworkers glue in the same fashion as you put fiberglass cloth on.  A wet coat of glue on the cabinet, press the cloth into it (a grooved roller helps here) and paint more glue over the top of it sealing in the cloth.  You can dye the glue black with epoxy paint or some coloring agent.  The result is a textured surface that hides minor flaws in the wood and is much much harder to tear off than just about anything else.

The Duratex is similar to the paint sold as truck bed liner in auto parts stores.  I've just found that stuff to be more expensive and more of a pain to work with.  After doing a couple of cabinets with bed liner, the Duratex was such a breeze.

Even though many amps will be rated into low loads, they always seem happier with higher loads.  I used to have a tri-amp rig driven from 3 QSC PLXs (3402, 2402 and 1202).  One gig I hooked them up with the amps bridged thinking that the increased power would give more headroom and clarity.  This wasn't running particularly hard either.  Bridging effectively halves the impedance seen by the amp in addition to running the speakers in parallel.  So I went from running at 8 ohms to effectively 2 ohms, still within the amp's rated limits.  The net result was that it sounded noticeably worse.  Kind of congested sounding without the punch and sparkle I had running dual mono at higher impedances.

[JohnGeorge]

@bill- 3750w must be burst then, also I don't see a long term output mentioned at 2 ohm..anyways, if u guys say that I shouldn't go below 4 ohms then 2 ohms ratings don't matter.

@Stephen- I think to laminate a fabric will be a more complex process for me and paint/tolex sounds doable to me. I just need to look for it, I'm sure I'll be able to find it.

So now I've got almost everything clarified and I have also decided as to what I'm going for. Thank you all, u have been great with your suggestions, opinions and prompt responses.

Only thing I need help with is the b&c design. Any one got a detailed sketch or a pic showing the inside of the box?

 



 

[Stephen Kirby]

For the paint you want either a polyurethane or epoxy coating.  Enamel won't hold up to much handling.  Another option besides truck bed liner might be epoxy concrete floor paint such as people use on their garage floors.

[Rob Spence]

I would suggest 25mm threaded inserts for poles for the tops. No wobble and they only intrude about a half inch into the cabinet.  Skip the cups.


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[JohnGeorge]

Thanks stephen and rob,

@Rob - i would have gone with the threaded inserts but I'm planning to use the poles that come with the speaker stands.
so when I'm not using the stands i can just use the pole.

[Rob Spence]

Thanks stephen and rob,

@Rob - i would have gone with the threaded inserts but I'm planning to use the poles that come with the speaker stands.
so when I'm not using the stands i can just use the pole.

You are planning on taking the tripod stand apart and using it?

Just get the right poles. Think a little longer out.


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[JohnGeorge]

Yes Rob i understand that but I'm sure that threaded poles will not be available locally and for me to pay shipping on every item becomes illogical.

as far as tripod stand poles are concerned, i have used them like that for years without any issue. apart from this one time when this drunk fella launched himself towards the speaker. it chipped the wood on one side around the cup (on the sub) due to the force and weight. but,if it has to happen then it will also happen with a threaded pole.

other option is to DIY a speaker pole with a thread - i definately do not want to take this risk.

however, i'll will still check if its available but the probability is 0.

and if there i any other reason i shouldn't do that, then pls let me know.

thanks, this type of advice is what I'm looking for which makes me think if i have made the right choices.

[JohnGeorge]

guys pls have a look at the attachment.

parts labeled 1-5 are all internal braces right? can i change the position of the internal bracing since

parts labeled 1 & 2 - its where the handles will come on either sides of the box, in the center. slightly towards the front. (to equalize the weight since most of the weight is in the front where the cone is).

part labelled 3 - it's where the speaker pole cup will come.

also @bill
"I like tying opposite walls together with braces. They don't have to be big, and in a sub the subtraction from internal volume is minimal. Just glue and screw them onto your wall braces - side to side, top to bottom. They are not in the B&C plans, but will really help tighten up a cab using less than optimal wood."
        if the above parts labeled 1-5 are internal braces then they are tied the way you said. it just that its tied on the side and not in the center like a + sign.right?

Sorry, im asking too many questions. it's just that im confused when you mentioned that it's not in the B&C plan.

[Bill Hornibrook]

Somewhere around the center of the cab, I ran a tie brace between 3 and 5, and between 1 and it's counterpart on the blind side of your illustration. On my 21" subs, I also ran triangle braces between 4 and 3&5, but it's a larger enclosure.

For braces I just use scraps left over from cutting the panels of the cab.

[Stephen Kirby]

That tie piece #3 is going to interfere if you put a pole cup in the top of the cabinet.  You either want to make it deeper or put two small ones in parallel.

[Rob Spence]

That tie piece #3 is going to interfere if you put a pole cup in the top of the cabinet.  You either want to make it deeper or put two small ones in parallel.

Or use the 25mm threaded ones. 


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[JohnGeorge]

Thanks Bill, Stephen and Rob.

I think I know the answers to the below 2 question and it may have been already answered. Just need an affirmative from someone more experienced than me for the below -
1. Only the 2 port pieces on each corner behind the baffle need to be exactly as they are?
2.Rest are just braces to make the cabinet stronger and to avoid resonance?

I have a fair idea now after looking at many BR cabinets and how they are internally braced, so I think I now have that covered. (If the above 2 are yes.)

@Rob- yes still on my mind. Just did not get time to visit local stores. Will visit in a cpl of days to see if threaded poles are available.

[Bill Hornibrook]

That tie piece #3 is going to interfere if you put a pole cup in the top of the cabinet.  You either want to make it deeper or put two small ones in parallel.

I used pole cups and mounted them just to the left and right of the top brace on each sub for a mirrored pair.

And yeah JohnGeorge if you are building this particular cab you don't want to change those port pieces.

[ProSoundWeb Community]