Concrete Speaker boxes

[depoquery]

Hi (new here)

I have some very old concrete flush troughs that went above the urinals in old pubs or establishments needing most probably 4 or 6 toilets.

These concrete boxes are made well, with 2cm thick walls.

http://img148.imageshack.us/my.php?image=speakerboxes.jpg

Dimensions (inside measurements):
50 cm wide x 23 cm high (top is curved 18cm high, lowest point at side)
25.5 cm deep to face of concrete.
volumes = 26 L
__


My main question is what type of speaker would suit a sealed concrete box?

And could it offer what I am looking for in frequency response and sound?

The exsisting speakers are about 60 watt (just for guidance)

If I make these speakers they would be used in conjunction with my existing speakers and I will perhaps latter look at a second 2 channels or 4 channel amp to suit the 4 speakers.

#######

At present I have a pioneer amp with original 9L base reflex speakers, after a few decades of punishment the Sansui speakers died so I replaced them with:
6.5in parabolic pp/paper (89 db, 44hz-7khz) 60rms/120max
& Titanium dome tweeter (91db, 2-20khz)
There were no crossovers in the original boxes, only a cap for the tweeter.
I put in standard 60w two way crossovers and placed 1uf polyester in parallel with the 4uf cap in the crossover for the tweeter.

The existing speakers are tuned, or enhanced to my ear for fidelity, clear vocals and sharp bass through the reflex design.

Trumpet and guitar are a bit dull, so without changing my existing speakers that took considerable time to get right for their particular merits, any ideas or thoughts as to suitable speaker with good mid range properties? the range were perhaps Trumpet and guitar might lie.

Just work with me, not to literal in my explaination!

Could they go in the concrete box from a respose standpoint?
("not" can they be mounted physically, I can work that out easy enought)

Also what do you think in the way of dense coating on the inside walls?

It is all subjective and I am the one that would be listening to the sound!

Cheers, any discussion welcome


Note: I cannot afford it but perhaps a second identical unconnected passive speaker arrangement would work? Similar to the bass reflex logic!

 

[lsiberian]

Wow. That speaker might be a bit stinky?

Concrete is an excellent material for a speakers interior layer. Built a constraint layer and an MDF box around it. Brace it with steel, and line it with mineral wool and you have a great box.

Finding a driver to fit the box is probably the greatest challenge.

 

[depoquery]

Very interesting

Wow. That speaker might be a bit stinky?

Concrete is an excellent material for a speakers interior layer. Built a constraint layer and an MDF box around it. Brace it with steel, and line it with mineral wool and you have a great box.

Finding a driver to fit the box is probably the greatest challenge.

Giday lsiberian

Very interesting and fitting in with something I read on the near endless dead end search for me on the subject.

So by constraint layer you are referring to a gap between the concrete inner and a second wooden enclosure? What width gap do you think?

By brace it with steel I am not following!
Brace the outer wooden box with steel, like strapping (But heavier steel?)
Like how wooden barrels are strapped.

Or brace wooden box on inside, lie steel strips on the outside of concrete enclosures and screw down wood sheets?


Please go in to detail if you will as I am very interested

Mineral wool, I have only rockwool block for growing.
What type do they use for speaker box lining?


I recon being a little adventurous in the design will not hurt in this case, considering the contoured top!
I am starting to get a few ideas as concepts such as pre stressing some timber to the right shape first but there might be other materials to consider at least for the arch area!


Thanks from the depo

PS. not used for decade or more and being outside the smell is gone, but yes, I will call them Stinkies B1

 

[jwenthold99]

I don't know if I have anything to add, but can you post pics? I am very interested to see what these boxes look like, and I love DIY projects

 

[depoquery]

The link to the pictures is in the first post. Re h(tt)p

Done

 

[depoquery]

Re: DIY interest

Re: DIY interest, in case you would like to see I include some pic’s.

Pioneer Speaker Replacement

 

[depoquery]

Concrete Boxes

Concrete Boxes

 

[Loren42]

You are going about this all wrong.

You need to determine what speaker drivers you have now that you want to use (you only mentioned size, but not make and model), then determine what a good woofer would be to match the drivers.

Then, design a cabinet that works with the woofers.

Once you have that, then you can see what use these concrete coffins are for you. It is pretty easy to add something inside to reduce the internal volume.

Then you need to design a proper crossover for the system. I can pretty well assure you that you can just dump the existing crossovers into the trash and start with a clean sheet of paper.

Finally, you need to consider the quality of the drivers you are using. Concrete is very nice, but not the biggest advantage for a system. If you have crappy drivers, concrete will not make crap sound like gold.

A reasonably built and braced wood cabinet will perform extremely well, so don't get hung up with concrete and try to put the cart before the horse.

If you really want to design and build your own speakers do the following 12-Step program:

1. Get a good book (or two) on speaker design.
2. Set a budget.
3. Determine your design goals.
4. Select and match your drivers for the desired system. You may find what you have is not what you want.
5. Get some PC speaker design software and start modeling.
6. Once your box is modeled, design your crossover. Store bought pre-made crossovers are useless. Don't skimp on this step, deign a good crossover and pay the cost. This is where you get the biggest bang for the buck. I would budget $100 - $200 just for the crossovers.
7. Peer review. Let others see what you are proposing to do and listen to the experienced people here. Heed their advice.
8. Go back and amend your design based on the peer review.
9. Build your boxes.
10. Build your crossovers.
11. Test and adjust you system and listening environment.
12. Beer-Thirty!!!

 

[depoquery]

welcome

Thankyou Loren42

Certainly I will take on board what you have said to try and get a good outcome.

Keep in mind it is all a bit of fun, and a way of demonstrating what sound is achievable for myself. Speakers are another whole story but I expect to be around a while to learn more!

It will be fun and Project continues.


Cheers



Just an extra note about the concrete box

I previously placed one of my pioneer boxes in one of the concrete boxes, with no front to separate the back information I do not consider it much of a test but it does notable change the sound, filling an uncovered spectrum quite well in conjecture with the other box not in a concrete house.


PS: 1 to 12, mostly put a tick as how to build it. I have various software for sealed and vented etc, but this is the discussion bit.

 

[Loren42]

You are welcome. However, how you begin your journey has a lot to do with whether that journey will be a fun one or a frustrating one.

This is why I outlined a structure to the process. If you shortcut the process or reverse the order, undoubtedly you will be returning to an earlier step to repeat the process in the correct order. This will waste time, money, and nerves. It is also a recipe for quitting when frustration overcomes joy.

Yes, it should be fun and I won't give you the answers so much as point out the path so you can enjoy the trek.

 

[depoquery]

The Trek

2. Redesign enclosures for a more practical size, remembering volume can be reduced by several methods but you cannot easily make the box bigger.

5. Start modeling and repeat step 1 in practice.
6. Once your box is modeled, design your crossover. Store bought pre-made crossovers are useless. Don't skimp on this step, deign a good crossover and pay the cost. This is where you get the biggest bang for the buck. I would budget $100 - $200 just for the crossovers.
7. Peer review. Let others see what you are proposing to do and listen to the experienced people here. Heed their advice.
8. Go back and amend your design based on the peer review.
9. Build your boxes.
10. Build your crossovers.
11. Test and adjust you system and listening environment.
12. Beer-Thirty!!!




Halving box size

My thought is to cut the right hand box strait down the center; these cuts would then be the mounting faces for speakers.

If you visualize this the top and rear wall will have a slope, a side wall is missing; now turn the box over making the missing wall the base instead. Now the rear wall is sloped a little horizontally and one wall is narrowing in towards the back.

____________

I have a few types/variations of these concrete boxes, concrete pavers for the box floors and tiles to experiment with latter down the track.

Have not got enough in the way of cutting blade for this job, I will need to go to town in the next week so no pics for a while. The next step I can take is some basic maths on the volumes and speaker types.

I am starting from scratch when it comes to speaker types for enclosure volumes, which ever direction you start from.

##### ADDED

The speakers I owned previously, 20 years ago were digital acoustics strait out the shop, 2 main drivers one above the other plus mid and tweeter in enclosures 4 foot high, I remade the cabinets with heavier wood and the sound was very good but it was 20 years ago so I need to look around the net and see what people are using now.

When you consider that rear speaker information is 190 degrees that of front the speaker type, cloth angle vs. enclosure shape are considerable factors.

Going back to my prehistoric speakers, the sound was very good and I ended up porting them, no design in mind I just got a few lengths of pvc pipe and played around to find what I liked. I then, 20years ago heard a set of flat speakers (honey comb or something), first I had ever seen and such a speaker.
Anyway I bought a set and put them in small boxes that complemented my stereo.

This time I will put a little more science into it, but not too much.


Let us know your thoughts step 2-ish, one step at a time.

Cheers


http://picasaweb.google.com/garylooney/NewFolder?feat=directlink

 

[depoquery]

180 not 190 degree, cane back to late when I realized the mistake.

 

[tom67]

Ceramic and Marble the only way to go...

http://www.norh.com/Welcome/Home.html

 

[depoquery]

Ceramic and Marble the only way to go

Ceramic and Marble the only way to go...

http://www.norh.com/Welcome/Home.html

This was plan A, to cast shapes like these in concrete.
I had read of this concept but was not sure of the proportions of such design.

I now have a very good template, thank you for your link.

After finding out they use ceramic it has me thinking what could be used other than concrete or what if anything could be added to concrete for a DIY affordable solution.
I have seen various materials added to concrete such as pins that strengthen and stiro beds for weight reduction, plating an enclosure with ceramic insulator plates used in ceilings was mentioned somewhere. No idea if it has any merit or if there is an affordable product?

Glass? I wonder what sound you would get cutting a hole out of glass flagon and putting in a Proportion speaker?
Or would you mix it with the cement, might be a bit hazardous!


If anyone finds more pics of cone shape enclosures showing detail or speaker specs I am very interested.


Cheers

 

[WmAx]

This was plan A, to cast shapes like these in concrete.
I had read of this concept but was not sure of the proportions of such design.

I now have a very good template, thank you for your link.

After finding out they use ceramic it has me thinking what could be used other than concrete or what if anything could be added to concrete for a DIY affordable solution.
I have seen various materials added to concrete such as pins that strengthen and stiro beds for weight reduction, plating an enclosure with ceramic insulator plates used in ceilings was mentioned somewhere. No idea if it has any merit or if there is an affordable product?

Glass? I wonder what sound you would get cutting a hole out of glass flagon and putting in a Proportion speaker?
Or would you mix it with the cement, might be a bit hazardous!


If anyone finds more pics of cone shape enclosures showing detail or speaker specs I am very interested.


Cheers

Actually, the Norh shape in the front baffle is very poor choice, overall. The cylinder profile(front baffle shape of the Norh) will cause substantial diffractive errors. Ideal is a spherical (or similar shape) front baffle or at least very large radius on the sides to allow a gradual/smooth de-pressurization along the edges.

The actual side profile shape with the gradual profile is good for internal acoustic resonances, but again, using proper internal acoustic absorption makes the interior shape irrelevant. However, most companies and DIYers do NOT use the proper internal acoustic absorption materials.

-Chris

 

[lsiberian]

Giday lsiberian

Very interesting and fitting in with something I read on the near endless dead end search for me on the subject.

So by constraint layer you are referring to a gap between the concrete inner and a second wooden enclosure? What width gap do you think?

By brace it with steel I am not following!
Brace the outer wooden box with steel, like strapping (But heavier steel?)
Like how wooden barrels are strapped.

Or brace wooden box on inside, lie steel strips on the outside of concrete enclosures and screw down wood sheets?


Please go in to detail if you will as I am very interested

Mineral wool, I have only rockwool block for growing.
What type do they use for speaker box lining?


I recon being a little adventurous in the design will not hurt in this case, considering the contoured top!
I am starting to get a few ideas as concepts such as pre stressing some timber to the right shape first but there might be other materials to consider at least for the arch area!


Thanks from the depo

PS. not used for decade or more and being outside the smell is gone, but yes, I will call them Stinkies B1

1/4 Dynamat in between the exterior layer and the interior layer is suggested. I've never personally use concrete. I just do a particle board interior brace it with a dense wood. Line it with rockwool. Line the wool with fabric.

If you can get 4" in you will have a truly dead speaker. I put 4" on the back and 2" on every other side. I don't see the need for 4" on every side. Since the back wall is where you get the 1st order reflection on the interior of the speaker from.

 

[depoquery]

Just thinking out loud

Thinking about deflection and box shape, do some boxes have internal plates?

I know they do have for bracing purposes and I am interested to know the best bracing philosophy to least impact open flow?


I recently found the wiki showing the gradually reducing tube shape inside a square box to reduce the overall size for practicality, one of the obvious physical aspects is a controlled graduating of volume and flow dynamics.

I am thinking that it might be possible to put in a plate at low angle to the speaker rear information, steering to a port. A simple plate system might work in some instances given the right maths and perhaps a little molding.


Thanks for everybody’s input