# bookshelf speakers



## sp408 (Sep 30, 2012)

Hello;

I am getting ready to make some bookshelf speakers here very shortly. I am currently drawing up the plans and measurements, however I want to try and fins an alternative to the 45 degreee box cut and go with something a little more sturdy. I know some boxes ive torn apart use some sort of double "L" locking or something. I was wondering what recommendations you would have. I am also looking for some new bits as I am just starting out and would love the help

Thank you very much
-Steve:sarcastic:


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## mgmine (Jan 16, 2012)

The easiest joint and one that is very strong would be a butt joint with pocket hole screws. The joint that you are speaking of takes a lot of fiddling to get it set up. It also requires a special bit. If you are going to make a lot of joints then this might be the way to go however a pocket hole jig will be a lot more useful over the years. You can get one for as little as $10 dollars but you may want to consider paying more for a Kreg model.


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## harrysin (Jan 15, 2007)

sp408 said:


> Hello;
> 
> I am getting ready to make some bookshelf speakers here very shortly. I am currently drawing up the plans and measurements, however I want to try and fins an alternative to the 45 degreee box cut and go with something a little more sturdy. I know some boxes ive torn apart use some sort of double "L" locking or something. I was wondering what recommendations you would have. I am also looking for some new bits as I am just starting out and would love the help
> 
> ...


Steve, because you haven't completed your public profile we don't know what level of experience you have or what tools are at your disposal. Mitres with or without splines are not only the norm for speaker enclosures but are also strong, having plenty of glue area. It is also not unusual to add glue blocks inside. These shots show how I make mitres on the router table using a 45° bit. The last three shots show how I make splines for boxes with mitred corners.


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## JOAT (Apr 9, 2010)

harrysin said:


> It is also not unusual to add glue blocks inside.


Yep, very simple, adds loads of strength. About 15 years or so ago I made a large toy box, no metal fasteners, all butt joints with glue blocks, still in use today, and just as strong as ever.


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## giradman (Jul 23, 2012)

Hi *Steve* - welcome to the forum! 

A few years ago, my brother asked me to make him an amp cabinet for his guitar(s) - had some old pine shelving which I had dismantled; put the carcass together w/ rabbets (as seen in the photo below left) reinforced w/ birch Miller dowels.

Covered the joints w/ molding (second photo right); the circle was cut w/ a router + circle trammel - he added all of the innards and claims it is one of his best amps - don't know? But I'm sure that you'll receive a LOT of joinery opinions; many will work depending on your tools & skills - good luck! Dave


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## Marco (Feb 21, 2009)

Again Harry, thanks for answering with attached pics


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## GulfcoastGuy (Feb 27, 2012)

To me the more important thing is the material. Dense and dead is better. A speaker enclosure should sound dead when rapped on, like knocking on the concrete slab of a garage as you would knock on a door. The reason is that any resonance you allow will will be added to the sound created by the drivers in some way. MDF is the material of choice for this reason. I consider 3/4" front, sides, bottom and top and 1-1/2" on the front baffle where the drivers are mounted to be a minimum. Internally the sides should be physically cross braced to the opposite sides, three ways; top to bottom, side to side, and front to back. Once constructed the enclosures may be veneered or painted as desired. In such a case the joint can be any joint that is strong. It should be an air tight seal except where you intend to pass air as in a port or vent. 

This all assumes a desire for the highest quality sound reproduction and if that desire is not an issue just ignore everything above and make a nice looking box from lumber of the species of your choice.

GCG


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## rich6467 (Mar 30, 2010)

3/4 inch or thicker MDF (unlike wood it has a constant density) is the only way to go. Are you working from plans? Just an enclosure will not give you the best sound.


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## GulfcoastGuy (Feb 27, 2012)

Here's a good website for DIY speaker building. Grab a tasty beverage. You may have some reading to do.

DIY Audio & Video - FAQs, Tutorials, and Calculators for Speaker Boxes, Crossovers, Filters, Wiring and more

GCG


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## sp408 (Sep 30, 2012)

I appreciate all the advice and will keep it in mind. I will be buying the material here later this week(hopefully). I was intending on using MDF and finishing it with something, still not to sure on what finish to go for. I want a really dark cherry wood coloring.

Sound quality is of the utmost concern for me, that and size. I will be using a set of speakesr from the polk Rti and tsi series. So far the set up will contain one 7" woofer with a 5 1/4 mid and one tweeter. Im planning on using one uni body set up, but the mid and tweeter will be housed separately within the enclosure and the woofer will be ported most likely with a 3" front facing circle port.
I was also debating on whether I should use fiberglass resign to smooth everything on the interior and use egg carton style foam for the mid/tweeter partition.

Thank you for all the great feedback


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## Cherryville Chuck (Sep 28, 2010)

Steve, the joint you described was a double rabbet. It is simple and fairly strong. It can be made with straight router bits. It is best done on a router table but could be done handheld with an edge guide. It can also be done on a table saw. A single rabbet joint also works and is simpler. My son has made many speaker boxes. He always uses mdf and uses PL 400 or 500 in caulking tubes to hold them together along with drywall screws. He has never had one come apart. Fibreglass resin also makes excellent glue but is nasty to use. You shouldn't need to smooth the inside. MDF is already very smooth.


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## GulfcoastGuy (Feb 27, 2012)

I did a quick search on the Rti series and didn't find the Thiele/Small parameters for the 7" driver. Do you have them? It'll be tough optimizing the box volume and the port length without them.

GCG


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## sp408 (Sep 30, 2012)

@Gulfcoastguy

Here is the link that gives some info on the woofer. I am not to speaker savvy so I am not to sure what it all means. I was just going off of my target range using a box calculator. The polk series speakers are RTI 12 

7" woofer
>>>>>mavin.com/pictures/polk-rd7225-1.jpg<<<<<

5 1/4 mids
>>>>>>mavin.com/pictures/polk-rd0514-12.jpg<<<<<


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## sp408 (Sep 30, 2012)

@GulfCoastGuy

Here are the only charts I can find on the speakers. I have been trying to find a box calculator for a circular port. So as of right now I was just going to use the original port diameter(3") and cut the length in half, as I am cutting the space in half of the woofers housing. I would like to find a calculator though so I can get the exact frequency I want to enhance. I am not very educated in dealing with speakers, I am mostly a computer guy. So any additional help is much appreciated!


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## GulfcoastGuy (Feb 27, 2012)

Since you seem to want a smaller box I'd go sealed instead of ported. Ported boxes need more volume to reach the extended bass you may be looking for. You'll get a truer sound with a sealed box anyway. I showed a F3 (3db roll off point) in the mid 50's with a 1.99 cubic ft volume. That may sound big but the ported box was above 3 cubic ft. As you reduce the size the bass will suffer. 

Gotta go right now. I try a little more detail later.

GCG


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## sp408 (Sep 30, 2012)

*Thanks*

I really appreciate all the advice from everyone so far. Thought I would show some of my progress. These are two of the coats I ahve done so far with staining mdf. After the black stain settles I have to sand and redo it as my brush left a few strands on it >_< , but I was planning on doing about 4 coats anyhow to make sure to get the right design grooves. The finished with be black, I just have not decided if I should go flat or semi gloss yet.


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