PPI Pro 12 Vented Sub Build - AVS Forum
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post #1 of 27 Old 09-20-2011, 01:45 PM - Thread Starter
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I couldn't resist buying one of the Precision Power flat piston car-audio subs when they came out like 10 years ago. I used my PPI Pro12 for a few years in my Integra and then it sat in storage for a really long time. It's taken me forever to start a build to use it in my home theater - but i finally got going after snagging a Dayton plate amp on sale recently.

I'm partial to sealed sub boxes in general, but the vented design in WinISD just looked so much better. I couldn't resist. About 3.5cuft tuned to 33hz.



Cut wood and glue up double baffle
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post #2 of 27 Old 09-20-2011, 01:47 PM - Thread Starter
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some assembly shots. the box isn't that big so i didn't go crazy with the bracing. i wanted to make a window brace but didn't have a big enough piece of MDF on hand
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post #3 of 27 Old 09-20-2011, 01:53 PM - Thread Starter
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the jasper jig is now officially one of my favorite tools. i was also pretty psyched to recently discover that my router had an adapter to hook up a vacuum to it. helped a ton to keep the MDF dust down.

i routed the countersink area first, then cut out the woofer hole. for some reason i decided NOT to bother checking if the sub fit in the countersink before cutting the mounting hole... once the hole was cut i realized the sub wouldn't slide into the countersink. i had to re-center the hole cutout with some shims, fasten everything to a piece of wood, and make another pass with the same centerpoint to enlarge the countersink. it all worked out in the end.
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post #4 of 27 Old 09-20-2011, 01:55 PM - Thread Starter
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must have had a bowl of stupid flakes for breakfast because i did not account for the woofer mounting when i put the bracing in place. a little surgery was in order. that harbor freight multi-tool really comes in handy sometimes.
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post #5 of 27 Old 09-20-2011, 02:01 PM - Thread Starter
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time for the ports. i was going to use PVC piping but ended up going all out and buying 2 flared kits from parts express. they look a lot nicer. unfortunately, the way they assemble i can't use the internal flare adapter because it would make the port longer than i need.

i could have laid out the location of the woofer and the ports a bit better... looks funny as i have it. the sub should be higher. i'm considering making another baffle.... but i'll probably just leave it because i'm going to make a grille that covers the entire front anyway.
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post #6 of 27 Old 09-20-2011, 02:06 PM - Thread Starter
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the only jigsaw i have is a crappy battery powered one. i hate using it. i decided to use my router and the edge-guide that came with it to cut the plate-amp mounting hole. so much smoother and straighter than a jigsaw.

on the last side of the cutout, the edge adapter wouldn't reach. then i remembered that i bought a router-jig kit (prior to the jasper jig) to cut circles and it came with a longer edge guide. i guess that's one advantage to being too lazy to return stuff - i think this was only the 2nd time i've ever used this thing.
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post #7 of 27 Old 09-20-2011, 02:09 PM - Thread Starter
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make that 2 bowls of stupid flakes. the plate amp hole had the same issue with the braces, though just barely. HF multi-tool to the rescue again. then it fit nice and snug
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post #8 of 27 Old 09-20-2011, 02:18 PM - Thread Starter
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every time i use bondo i use too much hardner. it gums up before i have a chance to spread it. i always tell myself - "not too much" - but it never fails. I was super determined this time, and used almost none at all turns out that's much much worse than using too much

a day and a half later, it still wasn't fully cured. I thought i might get lucky if i mixed an aggressive batch and laid a thin coat on top - maybe some chemical magic would firm up the first coat.

didn't quite work out. a day later, when i sanded it all off (i used WAY too much, as i obvious from the pics) it was a big mess. the bottom coat never really firmed up on one side and was all sticky. it sort of peeled off like silly putty. nasty. so next time, i'll just use too much hardener instead
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post #9 of 27 Old 09-20-2011, 02:27 PM - Thread Starter
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are you supposed to use stuffing in vented enclosures? i think you're supposed to line the walls with acoustic foam or insulation but leave the center of the enclosure open? i can't remember. i didn't have enough foam to line the walls, so i threw in a few pillows for now. i still have to take the baffle off and fiddle with the ports and a few other things so i'll see what the difference is with and without the pillows.

i was NOT happy that the Dayton plate amp provided about 15" of wire out the back of it. would have been nice if they made that a little longer so i didn't have to splice in an extension piece.

i ran some old school hip hop through the sub in my garage. it was pretty damn loud and lower than i expected. i was not looking foward to moving it. i don't know how you guys move those giant tuba's, horns and monster multi-sub boxes.
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post #10 of 27 Old 09-20-2011, 02:35 PM - Thread Starter
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the next day i manned up and carried the thing upstairs. it was not as impressive as i hoped as far as SPL goes. and it has no midbase at all. hits very low (in my opinion) but no punch and not that loud.

I don't blast anything so it doesn't matter - i essentially spent $100 on this adventure since i had the wood and the sub and the amp was on sale. i will still play around and see how to get the most out of it. Attached are some Omnimic measurements. One at ~1M, and one at my listening position on the sofa about 15ft away (the lower SPL graph). I have some tweaking to do with the ports, the stuffing and the amp settings. After i play with that for a while i'll move on to veneering it to match the rest of my living room.
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post #11 of 27 Old 09-21-2011, 06:34 AM
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Quote:


unfortunately, the way they assemble i can't use the internal flare adapter because it would make the port longer than i need.

Shorten the tube and use the internal flare. It helps.

Quote:


a little surgery was in order. that harbor freight multi-tool really comes in handy sometimes.

I didn't have any idea when I would use that tool but I grab it all the time now. With the widely available coupon, it's a great tool for under $20.
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post #12 of 27 Old 09-21-2011, 10:28 AM - Thread Starter
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Thanks rlj5242 - I'll take another look at the inner port flares given your recommendation. My issue is that i need a very short length - just under 3" i think. Just putting on the connecting ring to add the internal flare puts me at about the required length... Adding the flare itself puts me over by maybe an inch? But like i said, i plan on playing around a bit. Thanks for the feedback, i wasn't sure it would make any difference.


I'm bummed to discover that i get a good amount of hum from the sub when i have the crossover point above halfway (anything above ~80 or 100 hz). The amp docs recommend keeping the xover point on the amp set to max frequency when running off the sub-out of a receiver (which i am).

The amp is one of those Dayon 240watt (i think?) models that was on sale from PE a few weeks back for ~$100. I'm worried that it was on sale because of a tendency to this sort of problem anyone else comment on this? I don't recall ever having hum from my cheap plastic Sony active sub using this same connection path.
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post #13 of 27 Old 09-21-2011, 10:48 AM
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Most likely a ground loop issue and nothing due to the Dayton amp itself. The most common culprit is the cable tv coax. Do a search here for 'ground loop' and you will find a number debugging steps and solutions people used.
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post #14 of 27 Old 09-21-2011, 11:30 AM - Thread Starter
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Originally Posted by smbsocal View Post

Most likely a ground loop issue and nothing due to the Dayton amp itself. The most common culprit is the cable tv coax. Do a search here for 'ground loop' and you will find a number debugging steps and solutions people used.

interesting. i haven't noticed hum in anything in my house ever before. but after your comments and some reading it brings my whole house into question.

i've been having cable tv signal problems pretty much as long as i've been in my house (~4yrs). the past year it seems to have gotten much worse - or my tolerance has gone way down. my cable always stutters and my cable boxes reboot A LOT (several times a week probably). i threatened to leave my cable provider so they sent someone to my house last week and he did a bunch of stuff - added a booster and replaced every single splitter, coupler and coax fitting currently being used in the house. i thought for sure that would fix things, but it hasn't my cable is AT LEAST as bad now as before the work was done. the cable guy mentioned that anyone on my street in my local cable loop with a wiring problem could effect me. that bummed me out even more since i have no control over that at all. not sure what to do. might have to go the satallite tv route since fios is not available in my area. i'm currently on cablevision, which presents several other reasons to leave besides the signal problems.

well - that's clearly off topic from the original thread but i couldn't help ranting.

i will definitely try some ground-loop fixes as recommended. thanks
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post #15 of 27 Old 09-21-2011, 02:18 PM
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It is a very common issue so don't worry about it. Coax cables, dimmers, IR receivers can be culprits. You can locate the fix the issue or put in a good filter if you can't seem the resolve the issue at the source.

You can run without a ground, which can be dangerous, with either a cheater plug or if you have a bunch of spare power cables clip the ground off one to use for testing. (Had to put in the legal disclaimer if not a lot of people will harp of this, just don't plan on bringing the amp into the shower with you ) If this resolves the issue then you know for sure that the ground loop is the issue.
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post #16 of 27 Old 09-21-2011, 02:37 PM
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"The amp is one of those Dayon 240watt (i think?) models that was on sale from PE a few weeks back for ~$100."

A number of individuals have had problems with the Dayton 240w. Usually the difficulty can be solved with a ground loop isolator (~$20 Radio Shack, ~$10 monoprice.com).

I have had no problems with my Dayton 240w (but I do not have cable).
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post #17 of 27 Old 09-22-2011, 07:34 AM
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Quote:


Thanks rlj5242 - I'll take another look at the inner port flares given your recommendation. My issue is that i need a very short length - just under 3" i think. Just putting on the connecting ring to add the internal flare puts me at about the required length... Adding the flare itself puts me over by maybe an inch? But like i said, i plan on playing around a bit. Thanks for the feedback, i wasn't sure it would make any difference.

What is your Fb (box tuning frequency)? What diameter ports are those? What is your enclosure volume?
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post #18 of 27 Old 09-22-2011, 09:16 AM - Thread Starter
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Quote:
Originally Posted by rlj5242 View Post

What is your Fb (box tuning frequency)? What diameter ports are those? What is your enclosure volume?

I'm looking at an old WinISB project because i'm at work, not home, but i think it's pretty close to the final design -

Box volume is ~3.588cuft
Fb = 33.16Hz
Port Diameter = 2"
Port Count = 2
Port Length = 2.74"
Vent Mach = 0.10


In other news, i disconnected my cable wire last night and the hum went away. I'm going to try disconnecting all coax paths in my house except a single straight run from the street directly to my main tv's cablebox. if there is still hum, can i assume the cable grounding issue is somewhere else on my local cable loop (outside my house) ?

thanks,
joe
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post #19 of 27 Old 09-22-2011, 10:40 AM
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Fb = 33.

Why are you tuned so high? Is this a music only sub? Did you change the SSF on the plate amp?
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post #20 of 27 Old 09-22-2011, 11:16 AM - Thread Starter
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Originally Posted by rlj5242 View Post

Why are you tuned so high? Is this a music only sub? Did you change the SSF on the plate amp?

i had a relatively confined space to work with so i didn't play with design params all that much. with that volume enclosure, tuning lower seems to increase the F3 an unacceptable amount given the amount of low end i get out of it.

this was my first from-scratch vented enclosure design, so perhaps i'm just being foolish due to inexperience. advice is welcome. i'm not sure if i'll rebuild or not... i have a JL Audio 10" sub that i might also convert to a home-theatre sub. i should see what this box would do with that sub and consider another build for this 12" PPI and find a new location for it with more space.

primary use of this sub is tv/movies and gaming. very little music. i did not do anything wrt the sub sonic filter. being a sealed-box kind of guy, i never really worried about that before. i suppose i should have taken that into consideration with this build. in a quick search i see that my amp has a highpass at about 18hz. that's a big gap from 18 to 33 for over excursion risks.
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post #21 of 27 Old 09-22-2011, 11:30 AM
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Tune to 20hz and see how it sounds. It will take putting the full ports into the sub and that is it.
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post #22 of 27 Old 09-22-2011, 08:41 PM
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Agreed on lengthening the ports to lower the tuning frequency, it'll help take off a bit of the bump just under 50hz and give you more bass down low...

IIRC those subs didn't have much excursion so 20-25hz should keep things safe for movie watching.
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post #23 of 27 Old 11-10-2011, 12:22 PM - Thread Starter
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In the past month or so I spent a while trying to learn the art of hand veneering - hot hide glue and a veneer hammer. I thought this might be a better approach than constantly buying more and more clamps and producing elaborate clamping configurations for cold-press veneering.

Well.... it's not quite as easy as i expected. The technique definitely has it's advantages, but I'm not particularly good at it. I finally had to put my skills to the test and try to finish up this sub because i was sick of looking at bare MDF.

I covered the box with oak but tried to use something nicer on the baffle. The veneer was part of a sample pack so i'm not actually sure what it was - might have been some sort of maple. In any case, the baffle did not come out very good. Luckily my plan was to cover it all with a grill anyway. Attached are some pics of the result after staining to match my livingroom furniture. The stain actually hid some stuff, which was nice. I'm not thrilled with the results, but i can live with it.

I haven't sealed the box yet - i have shellack and some (oil based?) lacquer but i'm not sure i'm going to bother. Both (especially the lacquer) stink and keeping the work piece in the garage during these cold months has my wife was giving me hell about it. Can anyone comment on what will happen over time if i don't seal? Aside from missing some protection against nicks and scrapes... what i can i expect? Color fading? Veneer peeling? Stuff like that? How long before those effects kick in?

My half-assed-ness is partially due to the fact that my wife objects to bass in the livingroom. That was a big surprise to me. As soon as i turn the sub up enough to hear it, she says it's too loud. What a bummer. So as a result, this sub may actually get banished to a secondary tv-watching room where i will rarely see or hear it.


Thanks,
Joe
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post #24 of 27 Old 11-11-2011, 08:37 AM
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Originally Posted by lowpolyjoe View Post


My half-assed-ness is partially due to the fact that my wife objects to bass in the livingroom. That was a big surprise to me. As soon as i turn the sub up enough to hear it, she says it's too loud. What a bummer. So as a result, this sub may actually get banished to a secondary tv-watching room where i will rarely see or hear it.


Thanks,
Joe

That's very unfortunate. I have friends who's wives don't like "loud" sound while watching movies. Can you turn your secondary room into a primary man-cave room? Maybe set some ground rules ahead of time? My wife has been great about allowing speakers, subs, giant rear-projection tv's, and electronics in our living room. I think, though, that she's much happier having them out in the garage "theater."

Good luck, Joe!
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post #25 of 27 Old 11-11-2011, 11:20 AM
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I've seen people use pillows for sealed enclosures but never in ported. Rip open the pillows and glue/staple the stuffing to the walls.
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post #26 of 27 Old 11-14-2011, 08:56 AM - Thread Starter
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Originally Posted by RyguyOK View Post

That's very unfortunate. I have friends who's wives don't like "loud" sound while watching movies. Can you turn your secondary room into a primary man-cave room? Maybe set some ground rules ahead of time? My wife has been great about allowing speakers, subs, giant rear-projection tv's, and electronics in our living room. I think, though, that she's much happier having them out in the garage "theater."

Good luck, Joe!

Thanks man... it is indeed unfortunate. I'm impressed with how much some of you guys can get wife-approval for.

I put the sub in the livingroom the other day. Now that it has a grill and it's stained to match everything else it blends in pretty nice. I'll probably leave it where it is and use it like a coffee table to stack clutter on like everything else in my livingroom Once in a while when my wife is out i guess i can crank it up a bit.

The man-cave idea would be great except that the layout of the room is very very poor for any serious tv watching. The tv is diagonal from the sofa, which is really meant more to look out the back door into the woods than any home theater watching. Ironically, i just spent all my spare time at the end of this past summer working on redoing that room as a "wife-cave"... painting, flooring, shelving, tv mounting, new furniture.

I'm really itching to start a new build - maybe a Statements center channel - but i think my time will be limited the next few months so maybe i'll wait till next year.


take care,
joe
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post #27 of 27 Old 11-14-2011, 08:57 AM - Thread Starter
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Quote:
Originally Posted by Mrkazador View Post

I've seen people use pillows for sealed enclosures but never in ported. Rip open the pillows and glue/staple the stuffing to the walls.

that's a good idea - maybe if i ever move the sub i'll try that. for now i'm just gonna call it 'done'.

thanks,
joe
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