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 Topic: aperiodic concept for midrange in doors ( Topic Closed)
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teenkertoy
Joined: April 01, 2008
Location:
California,
United States
Posts: 112 |
| Posted: January 12, 2011 at 12:56 AM - IP Logged |
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For reference, this is the best page I found regarding aperiodic enclosures: AP Enclosures-The Aperiodic Cookbook (http://www.teamaudionutz.com/tutorial/1/AP_Enclosures-The_Aperiodic_Cookbook). After many hours tinkering in the garage, this design finally came to me moments from falling asleep. I will be installing 6" midrange drivers in these enclosures in my doors, with the "vent" going into the door cavity similar to the standard infinite baffle setup. So here is what I will be building over the next week or so.
The design starts with a 12" x 12" square of ABS plastic. Mount the speaker onto the panel. Take a piece of PVC pipe with an inside diameter just large enough that it can slide over the backside of the woofer. Cut it down and add an endcap to minimize the total air volume inside it. Great, now you have a very small sealed enclosure that you can mount using the large ABS sheet (which can be trimmed to any shape).
Now take another pipe slightly larger than the first pipe, and slide them together. Choose a size so that there is a decent gap between the tubes. Grab some fiberglass insulation and fill this gap. Now you have a medium inner tube with an endcap, a bunch of insulation wrapped around it, and a larger outer tube sandwiching it all together.
Now disassemble everything. Using whatever tools you can, create lots of slots longwise in both tubes. I'm aiming for a width of 1/4" to 3/8" and as long as possible. Most resources I have found recommend the surface area of the vent should be about 1/2 the surface area of your woofer. So for my 6" woofer (28 sq in.), I should have about 14 sq inches worth of vents.
Notice how if you only drill slots on half or three quarters of the circumference of each tube, you can twist them to vary the amount of air allowed to "leak". Should be a super easy way to tune the aperiodic vent. For more coarse adjustments, of course we can change the amount of fiberglass we stuff in there.
One thing not noted on the drawings is to be sure the ends of the pipes are sealed. The ONLY path from the rear of the woofer to the outside of the enclosure needs to be through the inner slots, through the fiberglass, and then finally through the outer slots. I plan to find some rubber gaskets for this in the plumbing department at the hardware store.
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Comments and critique welcome!
-J
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Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode. |
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teenkertoy
Joined: April 01, 2008
Location:
California,
United States
Posts: 112 |
| Posted: January 13, 2011 at 3:48 AM - IP Logged |
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Quick update:
Could not find both 5" dia and 6" dia ABS pipe, so changing the plans a bit. Using only 6" dia pipe now, and drilling holes into the side instead of creating slots (much easier this way). Fiberglass will be on the inside of the 6" pipe, sealed against the holes by thin rings of 6" pipe that have a slit cut in them, so they act like a C-clip pressing the fiberglass against the inside wall of the 6" pipe.
To glue the ABS together, I'm using a sweet technique I found elsewhere. Keep all the fine dust-like shavings created when cutting/sawing/sanding the abs pipe into shape. Then, mix it with a little bit of acetone to create a thick sludge. I find the bottom of a coke can works great for this. Apply the sludge (generously) to both faces you want to "weld" together, and clamp overnight. Working time once you mix the shavings and acetone is at least a few minutes, or until the acetone evaporates. I'm surprised how well this worked, it's like welding with a q-tip !
I'll post some more over the next few days.
-J
___________________________________
Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode. |
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teenkertoy
Joined: April 01, 2008
Location:
California,
United States
Posts: 112 |
| Posted: January 17, 2011 at 2:21 AM - IP Logged |
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Initial results, not installed in the doors, hanging free in the garage. The rear wave is not sealed from front wave with the AP enclosure, but then again suspending the woofer without any enclosure is the same way.
Hanging woofer without any enclosure shows an impedance peak of 15 ohms, and a valley of about 4.5 ohms.
Hanging woofer in aperiodic enclosure shows an impedance peak of 8 ohms, and the same valley of 4.5 ohms.
Reduced peak by half, which is expected. Should be interesting after installing in the doors.
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Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode. |
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z03mz03m
Joined: January 09, 2010
Location:
Delaware,
United States
Posts: 184 |
| Posted: January 17, 2011 at 11:31 AM - IP Logged |
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Wow you've done a little more research than I have so far! I need to finish reading that site and see if I want to try making something like this or just buy those pre-made ones from Scan Speak for $7.
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MAZDASPEED Protege
Eclipse - Exodus Audio - Kicker - Monster - Pioneer Premier - Precision power |
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teenkertoy
Joined: April 01, 2008
Location:
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Posts: 112 |
| Posted: January 17, 2011 at 4:52 PM - IP Logged |
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If you can build a simple enclosure and make the ones from Scan Speak work, go for it. I doubt all the effort I'm putting into this project is really needed, but I don't have much room in the doors to work with (and I really enjoy the process).
___________________________________
Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode. |
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z03mz03m
Joined: January 09, 2010
Location:
Delaware,
United States
Posts: 184 |
| Posted: January 17, 2011 at 10:47 PM - IP Logged |
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"(and I really enjoy the process)"
I kind of thought that might be the case. You seem to be a bit like myself, always doing things the hard way even though you know there is an easier way just because you like experimenting. lol
I'm building a .5cuft ported box tuned to 40 Hz that I'll try the anarchy's in my car to see what they can do like that. Then I'll probably end up buying the scan speak's and building an enclosure using them too. Then I'll know which one I think sounds better. 
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MAZDASPEED Protege
Eclipse - Exodus Audio - Kicker - Monster - Pioneer Premier - Precision power |
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teenkertoy
Joined: April 01, 2008
Location:
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United States
Posts: 112 |
| Posted: January 18, 2011 at 2:10 AM - IP Logged |
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More progress. Instead of fiberglass insulation as a leaky membrane, I'm using some fibrous carpet padding. This is the older-style stuff with many strands of fabric, not the newer plastic-foam-style stuff.
The padding is held in place by a strip of sheet metal along the top edge because the woofer basket needs the clearance. The bottom is held in place by a C-shape section of the 6" pipe that has been trimmed down to size.
Installed in the door, makes for a very tight fit. Cannot comment on performance yet, need to get some sleep first. And yes, that is Grace Water Shield roofing material on the door, don't laugh (okay maybe a little). It's 1/10'th the cost of dynamat or other "professional" products, the adhesive is a thousand times better, it weighs the same, and does not smell like asphalt. I'm using it to seal the door as air-tight as possible, not prevent sound from coming through the door.
For that, I have a sheet of Acoustiblok ready to lay over the top. If you're not familiar with it, take a look. They claim one 3mm (1/8") layer of Acoustiblok in a standard stud wall will result in more sound reduction than 12-inches of poured concrete (they have independent lab tests to prove everything they claim, and after hearing their product in action, I believe it).
-J
___________________________________
Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode. |
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z03mz03m
Joined: January 09, 2010
Location:
Delaware,
United States
Posts: 184 |
| Posted: January 18, 2011 at 10:16 AM - IP Logged |
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Holy jackhammers! That Acoustiblok is what I need for my loud ass exhaust! How much did you pay for how much? and did you just order it from their site? I'm really excited about that!
Your enclosures are looking awesome too. I hope all that work was worth it!
___________________________________
MAZDASPEED Protege
Eclipse - Exodus Audio - Kicker - Monster - Pioneer Premier - Precision power |
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z03mz03m
Joined: January 09, 2010
Location:
Delaware,
United States
Posts: 184 |
| Posted: January 18, 2011 at 3:56 PM - IP Logged |
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Do you know if a lot of water gets into your doors? you might want to make a semicircle that protects the fabric from getting wet. My doors get a lot of water in them and I would hate for you to get those vents soaked.
___________________________________
MAZDASPEED Protege
Eclipse - Exodus Audio - Kicker - Monster - Pioneer Premier - Precision power |
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teenkertoy
Joined: April 01, 2008
Location:
California,
United States
Posts: 112 |
| Posted: January 19, 2011 at 1:46 AM - IP Logged |
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z03mz03m wrote:
| Holy jackhammers! That Acoustiblok is what I need for my loud ass exhaust! How much did you pay for how much? and did you just order it from their site? I'm really excited about that! |
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I ordered two 4' x 5' sheets at $65 each, which comes out to $3.25 / sq ft. Shipping was about $25 from Florida to California, which is reasonable considering how much it weighs. You can request a demo, they sent me two 1' x 1' panels with some literature for free. If that's all you need, maybe that's the way to do it.
Regarding moisture, yeah the doors get some. I'll have check on it after the next rain and see what happens, but I'm hopeful.
-J
___________________________________
Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."
Jayne: "We're gonna explode? I don't wanna explode. |
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