# A twist on outdoor speakers...



## johnnystephenson (Sep 11, 2010)

I know someone will tell me this is an impossible task, but I dearly love a challenge. I want to create a set of outdoor speakers that will blend in with my brick patio and some of the pillars that surround it. Quite simply I want to fabricate a speaker that is constructed using concrete bricks mortared together. Similar in function to the Bose freespace 51 outdoor speakers. Except of course made with concrete rather than plastic/PVC.

It will be made using a marine grade plywood box with downward firing woofers and two tweeters facing opposite each other. The brick pillar that it will be set in will have enough clearance between the bricks so that sound will escape. I plan on using 2-Dayton DA135-8 5-1/4" Aluminum Cone Woofers for the driver but am unsure as what to use for a tweeter and crossover. I am also wondering what if any type of damping method I should use for the inside of the brick pillars to prevent echoing. I have googled this topic a hundred different ways so I know I am in uncharted waters with this. Any assistance with this is appreciated and once done if they sound any good I will publish the results along with plans in case anyone else wants to do the same.


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## bambino (Feb 21, 2010)

First off welcome to the shack.
I don't see why it wouldn't work, all you can do is try, my main concern is will they be protected from the elements? You should try to post a sketch up of your design so we have a better understanding of what your plan is.
Be sure to keep us posted as you came to the right place to get info about DIY projects.:T


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## robbo266317 (Sep 22, 2008)

You could have the tweeters down firing off a hard surface at 45°, this would provide some protection from the elements.

[_] <---Tweeter
\
.\ 
..\ 
...\


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## johnnystephenson (Sep 11, 2010)

I am not going to worry too much about the elements as I was going to wrap the box in screen and there would be a concrete cap on top, but would I get better sound if the tweeters fired downwards? My home speakers -KEF, have downward firing woofers and forward firing mids and tweeters and they sound amazing. So I guess I am ripping off their design in a sense. Robbo, about the angling to drive the sound outwards my plan is to try using a coarser grain of sand which will maintain an angle of approx 35-40 degrees. If that won't hold its shape at high volume I will fabricate a cone shaped piece of concrete. I would like to try the sand first using different grains and weights, that will allow me to vary the angle of the cone to get the best shape and sound. I am going to do an autocad sketch of this. If I do this will anyone be able to read it? I believe there are autocad readers that can be downloaded for free. The design of the box itself will be the limiting factor, so I am wondering what kind of crossover I should use and what, if any port and also placement. I know absolutely nothing about speaker design and have been looking at different speaker designs to try to understand a little more about the physics.


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## johnnystephenson (Sep 11, 2010)

After a bit of research, I have settled on the the following speaker configuration:

1. 1-Vifa NE25VTT-04 1" Titanium Dome Tweeter

and for the woofer

2. 2-Dayton DA135-8 5-1/4" Aluminum Cone Woofers

This is similar to a speaker kit (Tri-Trix) offered on parts-express that has received very good reviews. They are not the identical pieces because I need something more outdoor friendly but, rather are similar in specifications. The one problem I have though is the selection of a crossover (The description of the kit on parts-express leaves out its specs.) I am ordering everything from parts-express and there are several different crossovers to choose from so any input would be appreciated. The more I read about crossovers the more confused I become, must go head hurt aaaaaggghhhh......


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## fbov (Aug 28, 2008)

I won't tell you it's impossible, just that you're diving into the deep end....

My first thought is that you should try to use weatherproof drivers unless you live someplace like Arizona. A simple full-range weatherproof speaker will be a lot easier and may sound better. 

Then you mention crossovers, and I realize you've jumped into the "design a speaker from scratch" (aka "deep") end. This is not trivial. I'm not sure what outdoor-friendly choices are driving you away from the Tritrix, but any that prevent you from using a pre-designed crossover (note, I did not say pre-built...) is making your job a lot harder. 

If you buy a pre-built XO, you will get sound. However, it's likely that there will be significant linear distortion, as well as harmonic distortion if the drivers are used outside their comfort zone, as well as unknown impedence loading your amp. Crossover design is non-trivial, requiring either a bunch of simulation software and known-good speaker data, or a measurement system to characterize your drivers in the intended application. Then you need XO sim software to take your native frequency response (FRD) and impedence (ZMA) files and synthesize a combined response based on your crossover component choices. There are books written about crossover component choices... an EE degree is helpful. 

Please understand that geometry matters, too. You can aim your woofer down, but that changes its FR tremendously above 1KHz (Your KEFs are 3-ways and cross the woofer out before it becomes directional). You can aim tweeters in opposite directions, but that causes an absence of sound in one axis; useful in some applications but hard to deal with in general. If you brick-over the drivers, the gaps become waveguides with unpredictable results. 

It all depends on your ears and how sensitive you are to various forms of coloration. 

Here's an idea. Build a fairly conventional speaker in a weather-resistant box, encase 5 sides in the column. Find some brick-color, acoustically-transparent cloth, treat it with water repellent and put it at surface level in front of the drivers. If nothing else, the cloth should take the beating, not the drivers. You'll still have some bass issues, as encasing the box in brick alters the amount of baffle step compensation (BSC) required. 

If acronyms line ZMA, FRD and BSC aren't familiar to you, you have a steep learing curve between you and a good-sounding speaker design. Then again, you may be drawn to the speaker design hobby, and that's a good thing as long as you have reasonable expectations. If that's the case, start here:
http://sites.google.com/site/undefinition/diy-gettingstarted

Have fun,
Frank


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## johnnystephenson (Sep 11, 2010)

Frank, thanks for all your advice. In deciding to start this project I knew that there was going to be a lot of groundwork necessary if I was to pull this off successfully. I am also aware that by using a wooden box surrounded with a brick pillar that it may just physically impossible to make a decent sound due to the characteristics of the materials used. I am also prepared to go through several different box designs with different tweeter placement (sideways vs. downwards etc.) But, I am not prepared to make several different crossovers to see what works best. Everything I have read on crossovers says that it is one of, if not the most overlooked aspect of speaker design. I understand what one does and how one works, but I do not want to let it become the reason I decide to pack it in and for this reason I am choosing to go with a crossover similar to the one that comes with the tritrix. I choose that one because the speakers that I am using are the most similar, most outdoor friendly(BTW I live in Canada -read COLD) to the ones that come with the tritrix. So if anyone can point me to what crossover that is you have my thanks.

It is probably pretty obvious that I have never built a speaker before and I am slowly coming to the conclusion that if I do pull this off it will probably be because of luck rather than ability (certainly not experience.) Because of the uniqueness of this project, and understanding that there is nothing to reference against to make this work I am forced to see what works with other speaker designs and borrow bits from them and with any luck it just may work out. But I am determined to have fun and hopefully learn something from this.

Thanks again for your help, I am going to take some photos of the pillars, the base and the box and enclose them in an upcoming post.

But I really need help with crossover selection.

John


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## fbov (Aug 28, 2008)

johnnystephenson said:


> .... I do not want to let it become the reason I decide to pack it in and for this reason I am choosing to go with a crossover similar to the one that comes with the tritrix. ...But I really need help with crossover selection....


As you move forwrard, I'll suggest posing your questions on the PE forum. Some posters there have offered to do XO designs for others, and cjd is a regular poster as well. 

I like your attitude, and was thinking of the same weather issues you see... but we get mor esnow on this side of the lake.

Have fun,
Frank


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## bearberry (Apr 7, 2010)

Johnny,
Hi from Ottawa.
Rather than picking drivers that are more likely to stand up outdoors and winging the crossover, may I suggest looking through successful designs here and on other diy boards such as diyaudio and Parts Express's Techtalk to find one with drivers that will be suitable. Then the crossover is already designed and won't be an issue.


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## GranteedEV (Aug 8, 2010)

Why not just buy a pair of these and rip the drivers out?

That'll save you time finding drivers that work together, and also give you a frame-of-reference crossover to look at.


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## WmAx (Jan 26, 2008)

While costly, JL Audio has some marine grade tweeters, mids and subwoofer drivers(suitable for your application) of good quality available in various sets/combinations. You would ideally invest in these so that the speakers will last a very long time exposed to weather. I would not use the stock xovers though; it would be ideal to design your own xovers to integrate the drivers. I do not believe the surrounds on non-weather designed speakers will even last the long term. The marine drivers use materials specifically suited to very harsh exterior elements.

BTW, for the treble, I would recommend going for an omnipolar type configuration where the tweeter is pointed up or down and fires into a specially shaped waveguide to distribute the energy in all directions. An outdoor speaker will be typically demanded to be heard at very extreme angles, and this will ensure best sound similarity at all positions. A very specific waveguide shape is required for this to work well; trial and error, starting with emulating the waveguide on known speakers of this type will be required. Refer to Beolab's highest end speaker for example of this type of waveguide. Also, Mirage has a similar example to emulate, as well as a few other not so common speakers.

Chris


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