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DIY Cinder Block Speaker

somebodyelse

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A cinder block speaker is a great idea, thanks for passing it on. But how the heck does that example work? The woofer is in the lower volume and the port is in the upper volume, with no apparent path from one to the other. Am I missing something?
Looking at the assembly animation there seems to be a routed recess in the back panel that would couple the two volumes, probably acting as a slot port.
 

Martin

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Cram

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Ok So I have dug deeper based on some of the comments. Super appreciate the help here.
Here is the mock of a standard cinder block from Lowes (there are lots of different sizes but I found this to be the biggest that is semi-standard)

Couple Questions and Facts

The ~sealed volume of each cavity is .217 ft cubed. Based on some of the feedback here, I'm a little confused if I should try and seal each cavity or cut out the divider somewhat to create a larger volume. Looking at the animation again, it looks like it would be rather hard to truly seal each cavity but I'm not sure which is better.

Second Question is about sealed volume. Based on the size of the cavities, I think it makes sense to have a 4" driver. The Dayton Audio one I have looked at have a sealed vol of .18ft cubed which means (if i understand) that this cavity is actually WAY too big for those drivers? It would be even more mismatched if you added both cavities to the sealed volume.

Crossovers: I have tried to understand the ideal crossover point but I really am missing something here and could use some advice. I need a crossover for each driver right?

For tweeter, this is the one that looks best for this but any advice would be welcome

For additional parts,
Speaker Terminal
Already have speaker cable (14 gauge monoprice)
Gasketing Tape to make seals
Glue to conect wood to cement when complete.
Am I missing anything here?

IMG_0302.jpg
 

hex168

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If you look closely at the animation on that site you can see the rear panel is made in such a way that it connects the top and bottom chambers of the cinder block allowing the port in the top chamber and the woofer in the bottom one.

Martin

looks like @somebodyelse beat me to it
OK, so this is a double tuned reflex. Vituixcad, and probably other loudspeaker design software, can calculate the enclosure. I would not use a random slot in the back panel - it needs to be tuned! See:
https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html#Driver_configuration
 

puppet

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Save the .gif to your machine and open it w/a media player. Now you can pause it.
 
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Cram

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Save the .gif to your machine and open it w/a media player. Now you can pause it.
You can do it on a mac in preview. Great idea. The two chambers are connected!
Screen Shot 2021-08-31 at 3.45.33 PM.png
 

hex168

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THIS SCARES ME A LOT. Is there a beginner version of this.
Sorry about that. I am not aware of any beginner-level calculator for a dual tuned bass reflex. Perhaps someone else can chime in if they know of one. Unibox is good but as far as I know won't do a dual bass reflex:
http://audio.claub.net/software/kougaard/ubmodel.html
This page has a lot of good, free loudspeaker software:
http://audio.claub.net/software.html
And a beginner's guide:
http://audio.claub.net/software/DaveDalFarra/Simple Loudspeaker Design ver2.pdf
Poking through this thread will give you some background information on speaker design:
https://www.diyaudio.com/forums/multi-way/332688-design-own-speaker-scratch.html

But this all requires climbing a learning curve. So, here's a work-around: A ported dual-chamber is too complex. Use a woofer that will work in a sealed box of 0.4 cubic feet. Put some stuffing in the cinder block, and do not port the speaker. Try to find an already-designed kit with a similarly-sized front panel and copy the crossover. I couldn't find such a kit quickly, so here is another suggestion:

An example woofer that could work:
https://www.parts-express.com/Peerless-830657-6-1-2-Paper-Cone-SDS-Woofer-264-1088

And an example tweeter:
https://www.parts-express.com/Peerless-DA25BG08-06-1-Aluminum-Dome-Tweeter-6-Ohm-264-1460

Among the nice folks at the Parts Express Tech Talk forum, there are people who will often model a crossover for a beginner. If I were you, I'd post there and ask for suggestions.
https://techtalk.parts-express.com/forum/tech-talk-forum
 

ernestcarl

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I saw this video where they filled the hollow front baffle shell of some ADAM T8V monitor with concrete:


The resulting playback sample demonstrated less coloration after the mod. It's not immediately obvious how the unmodded version is "bad" since it (w/out mod) apparently also increased the volume due to harmonic distortion adding a bit more "character" to the sound. However, studio monitors should be as neutral as possible so we can conclude the concrete reinforced baffle is the winner.

I also found similar deficiency in my cheaper JBL LSR monitors having this issue, but I already made a similar mod using different material.

I checked my Sceptre S8 monitors, and behind the thin front plastic fascia the MDF was already 2.75 cm thick around the concentric driver -- though not the entire height -- and with absolutely no spacing/air gap like in the cheaper Adam.

Out of curiosity, I filled the plastic trim and front fascia of the Sceptres with heavy duct sealant -- just happened to have a whole big tub around -- and did measurements afterwards. Result was very little change/improvement, if any at all. Well, I'm rather relieved they didn't skimp on the physical construction of these monitors!

I still have some of that grey sludge left in that duct sealant tub... hmmmn. might do my old Mackie (cheaper MR8 MK3) monitors next.
 

Ericglo

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While a really neat and cool idea, I think it would be easier to cast a concrete box for an off the shelf kit. One of the most difficult parts of DIY is routing the driver holes. You still have to do this with this design.
 

dasdoing

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I saw this video where they filled the hollow front baffle shell of some ADAM T8V monitor with concrete:


The resulting playback sample demonstrated less coloration after the mod. It's not immediately obvious how the unmodded version is "bad" since it (w/out mod) apparently also increased the volume due to harmonic distortion adding a bit more "character" to the sound. However, studio monitors should be as neutral as possible so we can conclude the concrete reinforced baffle is the winner.

I also found similar deficiency in my cheaper JBL LSR monitors having this issue, but I already made a similar mod using different material.

I checked my Sceptre S8 monitors, and behind the thin front plastic fascia the MDF was already 2.75 cm thick around the concentric driver -- though not the entire height -- and with absolutely no spacing/air gap like in the cheaper Adam.

Out of curiosity, I filled the plastic trim and front fascia of the Sceptres with heavy duct sealant -- just happened to have a whole big tub around -- and did measurements afterwards. Result was very little change/improvement, if any at all. Well, I'm rather relieved they didn't skimp on the physical construction of these monitors!

I still have some of that grey sludge left in that duct sealant tub... hmmmn. might do my old Mackie (cheaper MR8 MK3) monitors next.

wtf? why does the woofer resonate like this? here you see that waterfalls are usefull for speakers, too
 
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