got cabinets made from local builder, a little upset with quality

[mazurek]

I've been working on a loudspeaker project forever now, and I shelled out a good bit of money to get some cabinets built (I live in a condo, and electronics are my main game right now).

I asked for void free baltic birch, and the builder gave me a quote that said they will be made from russian birch. Anyway, two-three months later, I finally took delivery of the cabinets, and they have all sorts of voids. Of course I don't know what expect, so could you please assess the quality of what I got, I have some pictures attached. Some internal parts look a little flimsy with voids, they did a good job of hiding them on the outside.

Also he laminated 1/4" and 3/4" plywood to make my 1" thick baffle, but clamped them together with many staples all throughout. I thought that was a little stupid seeing as how I told him I would have to route holes. I'm confident a carbide bit can work through that, but it seems a like a bad idea to plow through staples. Not sure though.

He gave me one warped baffle that he said he would replace, so I used that to cut some test holes. I was planning on using socket head screws, and got a counter-sink bit from mcmaster. Some of the holes ended up well, but some ended up with the socket screw pulling through when I tightened them. Is high quality plywood supposed to be that weak? I figure I will try and use some wood hardener in the next baffles.

So what would your advice be, and how should I salvage these cabinets. Are they that bad? I don't really have money to redo. My plan right now is to brace them a whole lot, and use wood hardener for all screw holes.

Thanks,
Lee

[Chris7]

It's hard to see if there are any voids in those pictures. Strictly speaking, voids are air pockets. Are there open, visible air pockets between the plys? All wood has knots; even high quality void free ply has areas filled with different bits of wood. Areas filled with glue rather than wood are arguably voids, depending on who you talk to.

Anyway, that doesn't look like the highest quality ply, but it doesn't look too bad either. This picture has really bad, low quality voided ply on the left:


You should not use your router on that baffle unless you remove the staples first. Cutting through staples will destroy your router bit and is very unsafe; a sharp enough piece of metal could puncture safety goggles.

I would suggest getting a 1 inch thick piece of MDF for the baffle. MDF is easier to route... you'll get some tearing with ply no matter what. Your supplier laminated 3/4 inch ply with 1/4 inch because he'd have to order an expensive full sheet of 1 inch thick ply that I'd imagine he wouldn't find much use for beyond your baffle.

Also, birch is soft, so it's not unexpected that screws will sink into it when tightened. They shouldn't come all the way through though. I would still suggest using T-nuts.

[Rolex]

Regardless of what it looks like, take them back if you are not happy. Some would argue that 3/4 laminated to 1/4 is a strong material than one piece of 1" material.

[mazurek]

Sorry, its unclear from the picture. There are several air pockets where large sections of one or two plys are missing, its worse in some areas than others.

Thanks for the advice, I think I'll try to work with the cabinets, and see if he can recut the baffles out of MDF.

[---k---]

That ply looks similar to what I got when I bought the 13-layer BB ply. I had a few voids, but not many. I also bought some 7-layer, and it was definitely worse. I wondered the many times if the voids I saw were really voids, or if a dull saw blade or router made them just at the edge.

I think I'll leave it to some of the guys that have built lots of speakers to give you advice on what to do next. But, I don't think the guy screwed you.

[peterS]

one way to find out- cut up the baffle that is unusable

probably just used a rip saw instead of the proper blade

reason #242398 to not have a builder design your house or in this case box

[warnerwh]

You may want to try filling the voids with wood filler.

When you screw use a cordless drill with an adjustable clutch if possible. Then put some screws into a scrap piece of wood trying different levels on the clutch. For example on my Makita cordless I use 14 for drywall screws 1 5/8" long. On a softwood like Birch on this drill I'd try around ten and work my way up. This will obviously vary by the drill's torque and make etc etc. My Bosch cordless wants to be set much lower than the Makita but it's an 18v as opposed to 12v too. You can get cheapos from Schucks that will probably work fine as cordless drivers too. They're not that bad for the money at all. For 20 dollars you'll make life much easier on yourself if you get one. They're faster too.

It seems that you're in a tough spot because I get the impression you don't want to take them back. You can definitely brace them better and that will certainly help. I don't know what you're using in them but they will probably work great.

[PMazz]

The plywood looks about as good as it gets these days. It's a real crap shoot.

Have him make new baffles! There is no way that 1/4" should be stapled to create any sort of uniform bond. The staples would need to be a couple of inches apart and those very staples will compromise the structural integrity of the board. As has been stated: do not try to route thru them!!!

Forget about those corner blocks being structural. If they were just put there to try to keep the open end square, fine, but don't expect them to be that strong. Edge grain of ply is a notoriously weak gluing surface.

Pete

[mazurek]

Yeah, I am reluctant to totally reject the work, that will involve many hours of labor for me, or months more waiting.

Thanks for the advice so far, I think they may just have ruined the structure on the open side. I'll use some wood filler for that to prevent it from being too fragile.

I'll definitely try to get the cabinet maker to make new baffles then. The fellow is proud of the work his shop does, and wants pictures of the completed speakers, I think he or some of his employees just didn't know any better.

Forget about those corner blocks being structural. If they were just put there to try to keep the open end square, fine, but don't expect them to be that strong. Edge grain of ply is a notoriously weak gluing surface.

I was planning on using those corners to hold on baffle sections, each section is about 12x12 to 12x18. I had done a rough calculation given the shear strength of glue, and figured it was plenty to hold the baffle on and compress the gasket. Should I install a backing made from another material?

Thank you everyone for your advice, I've been trying to be self sufficient and not ask for too much hand holding on the forums, but maybe I should have posted some designs before sending them out.

Lee

[JonW]

Lee-

Please, please, please promise us all that you will not try to route through those staples. A 10,000 rpm router bit biting into a metal staple could kill someone. So promise us you won't even try that, OK?

Like people have said, there is better BB ply out there and there is worse. Best of luck with your project.

[PMazz]

I was planning on using those corners to hold on baffle sections, each section is about 12x12 to 12x18. I had done a rough calculation given the shear strength of glue, and figured it was plenty to hold the baffle on and compress the gasket. Should I install a backing made from another material?

Use solid wood. Either replace what's there with a thicker chunk of solid wood or glue an additional chunk of wood behind what's there.

End grain to long grain glue joints are very weak as the glue only creates a strong bond "with" the grain. Since plywood is layers of alternately oriented grain, half the gluing surface is compromised.

Pete

[warnerwh]

You should ask questions you're unsure of. That's how we learn. I'm also new to diy and to this forum. The people here have been very friendly and very helpful to the point I've felt guilty about being a pest and not asking anything that I don't consider very important to know.

It's always better to make sure you know what's going on before you do anything. Like they say: Measure twice, cut once.

Being as you have staples holding the panels together I wonder if they can be pulled easily and how many there are. Maybe you can post pics and someone can come up with a good resolution for you.

What would concern me is using two pieces of plywood like that. Unless they're glued well too you could get some vibrations between large panels. If you could remove some of the staples and look at least and then use glue and screws to keep the panels together if there is none it would be best to do now.

If it were me I'd have the baffle done with mdf and veneer it. I've never veneered but have been assured that it's not that difficult if you take your time and try to do as good as you can you'll end up with a decent looking job.

[mazurek]

Thanks for all the advice, I didn't want to challenge anything with the builder without knowing any better.

The staples are embedded in the wood, there is no way to remove them. At least at this point, I have several strategies now to fix things. I'll repair the cabinets, and work on getting new baffles.

Hopefully, I'll resurface one day, maybe several months from now, with cabinet drawings, frequency response/distortion testing scripts, crossover, amplifier schematics, power supply, and pcb drawings for all this stuff I've been working on for ages. Everything is in working prototype stage and was just waiting on my new cabinets.

[cjd]

This looks to me like they're done well, according to cabinet spec as most folks would build a basic carcase for a cabinet of the type you install in your home.

Some more robust bracing in the cabinet can very easily be retrofitted.

Baffles, yeah.

I would chalk this one up to the builder doing what he thinks is right, you expecting something different. Did you make a point of giving him an accurate build sheet, or did you just ask for cabinets of x-y-z dimensions? Without a build sheet, I think this is just a "ahh, we've both learned" experience - in the future you need to be more specific, and he'll now know how to build speaker cabinets.

You can use the pics of the 3-ways Brian and I did if it helps you any... main post here, in birch ply.

C

[warnerwh]

Well as you can see mazurek there's plenty of good quality help here. I don't know diddly myself but am learning.

Fortunately like has already been said some shelf braces or at least cross bracing will make up for any weaknesses easily.

If you look at commercial designs you'll rarely see the build quality that I've seen in pictures of speaker cabinets that have been built here. The link cjd provided has great pictures of shelf bracing and some unusually well made cabinets. When yours are done they'll be far superior to what you buy.

I've seen alot of high end speakers that have little or no bracing. With cross bracing alone your cabinets will be superior to many high end commercial designs. I think part of the reason is cost of materials, time and shipping costs. Regular manufacturers have to make a profit where you and I don't.

I hope your speakers turn out well. I once thought of designing and building a pair of speakers until I did alot of research on the subject. Apparently crossover design is much more difficult than it would appear. Crossovers also have a huge effect on the sound quality. To make a long story short I'd be too chicken to do what you've done. Just building this sub has made me nervous. The best part is though I've had excellent help here so am confident it will perform as well as I expect, which is outstanding. Plus I'll have done it myself which I've enjoyed every step of the way.

So it looks like you're really not in any significant trouble with your cabinets. Some bracing and new baffles and you'll be in business. If you don't mind me asking could you tell me the drivers and crossovers you're using as well as the bass performance theoretically expected please. Thanks

[HMenke]

If you take them back for nothing else, take them back to have the staples removed. They're not necessary now that the glue has set. I'd be pissed about this if I were you. :M

[warnerwh]

If the staples are going on the inside you'll be fine. Just get a hot glue gun and some extra strength glue sticks. Put a dab of hot glue over each staple and it's not going anywhere.

Hot glue is very strong. Even on MDF. Someone asked me why I used it as well as my wife. That worried me because I'd used it on wood but not mdf. On wood the wood will rip apart before the glue comes off.

So I did a test on MDF, it will also rip apart before the glue goes anywhere. In effect it's not going anywhere and your staples will not be able to vibrate out.

I sure hope you don't have staples on the outside of your cabinet :cry:

I've never used a router but can imagine that being potentially dangerous as heck going through staples so you may have to get some out.

If you draw a circle where the circular cuts will be made and take out all staples within an inch at least you may be able to use the router. I'll let someone else who knows better than I do confirm or deny this.

You can get the staples out with a small pry bar. They make them to remove tiny nails with pointed and curved ends. With a hammer you should be able to tap this nail pry bar under the staples to get them out. I'm afraid I have to recommend the more expensive one which is about 17 bucks at a hardware store.

Be sure it's got the pointed and not squared ends and it will work.

[mazurek]

Thanks everyone, here's some more details about what I've been doing. I submitted the following drawing for manufacture. I expected to require some additional forms of bracing retrofitted, thats not a huge deal. I was mainly concerned with material quality and the staples.

It includes 3 spaces, two one cubic foot spots for the subwoofers. One cubic foot spot for the midwoofer, and space for a chambered tweeter. Everything is on separate baffle segments because the drivers will be heavy and a little awkward. I had a detailed look at the RS 3 way cabinet drawings before drawing my own. My cabinet design philosophy was to not worry about the subwoofer spaces too much because the walls are too short for resonance to occur, though I will add one or two cross braces. I will extensively brace the midwoofer cavity, and apply acoustic foam (which does not appear as good as fiberglass, but I'd rather work with, and should have absorption in the frequencies I require).

The tweeter will be horn loaded with a shallow horn to help with diffraction and time alignment, and maybe power response if I'm lucky to some extent.

The first set will go to my dad who is paying for parts cost.

I have for each loudspeaker 2 Dayton Reference 10HF, 1 ScanSpeak 18W4531G or Peerless Exclusive 830883, and Seas 27TDFC. Crossover points will be 100-160Hz and 2000Hz LR4 acoustic, depending on what my measurements will say.

My current setup involves Dayton 12HF, Peerless Exclusive 830883 and Seas 27TDFC. I am quite happy with the Sub and Tweeter, but I used the Exclusive as a drop in replacement for the 830875 and did not take the 1000 Hz dip into account. For the next version, I was going to try the 18W4531G, I used "The Edge" diffraction simulator, and thought that the cabinet diffraction for that baffle width should line up well with the frequency response and hopefully require minimal crossover shaping.

Right now I have an active analog crossover -> Hypex amps and Rythmik Audio 350 Watt amps with the onboard crossover disabled. My pile of amplifiers and cabinets and cables is a mess, and this project is an excercise in system integration a la active speakers. I have a prototype UCD180 plate amp with one channel operational with balanced input, trigger on, soft start, and good quality speak-on connectors. I've been waiting until I have the cabinets done to make sure that the plate amp is sized correctly. I imagine lots of people would be interested in this project, but I'd like to certify safety/correctness, etc.

I enjoy these forums for their project orientation, and the large number of productive members.

Here's a cabinet drawing.

[mazurek]

I'll post my frequency test algorithm that some may find interesting, for the amusement of anyone tracking this thread. Its a brute force method that samples at a bunch of frequencies. It outputs windowed sine waves, and measures the frequency response and harmonic for each tone, each response is searched for, and only the original wave duration is analyzed to reduce spurious reflections. It uses the fourier series definition to find the magnitude of response c = sqrt(a^2+b^2), a=integral(f * sin(...) ...) .

[warnerwh]

Thank you. I really like the idea of having that low crossover for the woofer and letting a midrange handle that region without a break til 2k. It sounds like you will have a very nice speaker.

I have the Rythmik 350SE plate amp and would like to know how to disable the crossover in it. I'm not very knowledgeable with electronics but if it's easy I'll do it. I will be buying an outboard crossover so I can run both of my subs with it instead. Same with the volume, could I just connect the two wires going to it or is there more to it than that?

Thank You

[cjd]

Looks like they were well built to the provided specs. Aside from the baffles, and even they are technically - the biggest worry there is the danger routing the holes will provide 'cause of the staples. But staples can be removed.

C

[mazurek]

I have the Rythmik 350SE plate amp and would like to know how to disable the crossover in it. I'm not very knowledgeable with electronics but if it's easy I'll do it. I will be buying an outboard crossover so I can run both of my subs with it instead. Same with the volume, could I just connect the two wires going to it or is there more to it than that?

Thank You

I'll be working on getting you a picture, I didn't have time tonight. Basically, you find the input wires going to the amp board and cut them and reroute them directly to the input. The crossover board also buffers the signal, so removing it will make you less immune to the effects of interconnect length and capacitance. My view is that subwoofers have such low sensitivity, line noise affects them little. I believe the input impedence is still in an acceptable range with the modification.

[warnerwh]

Thanks, I'd appreciate that.

[JasonB]

This definetly does not look like Baltic Birch, and from what I have read Russian Birch is just a grade of Baltic Birch that does not have a clear face. The core should be identical.

That plywood looks suspiciously like plywood sourced from Asia. There are two signs that point to this. The first is your last photo, on the left side of the picture you can actually see the cores of the plywood overlapping, the seond is the fact that you mentioned one of the baffles was warped.

I have had lots of experience with this import grade plywood. Some of it has been acceptable and some has been completely garbage. I have often had times when sheets have been cut in to parts and a day later all the parts are warped and twisted, I have also had sheets that have delaminated. I deal with a couple suppliers that sell it and it's pretty cheap and available in a good selection of face veneers. The problem with it is a lot of peolple assume that just because it has a lot of layers it must be as good as Baltic Birch.

Real Baltic Birch is very strong and stable, has very few voids if any, will not have overlapping cores, and to my knowledge is only available in 5' x 5' sheets.

It sucks to be in the position that you are now, If it were me I would go to the cabinet maker and at least try and get some of your money back. I'm sure these enclosures are useable as long as there are no really large voids or delaminations. As long as you brace them well they will probably sound fine. But if you do end up routing through the staples you will chip up your carbide router bit pretty quickly and you will have to be very carefull of flying bits of metal.

Jason

[cjd]

It could be that the builder is being screwed also as far as plywood quality...

I've built with similar materials and I think you'll not have any audible issues with the ply as it is.

C