enclosure design/vibration issues

I'm relatively new at this, but I designed my second enclosure thinking it was a design that no one had executed before, turned out I was wrong on the shared port idea. More or less I'm just looking for feedback for improvements, and if this push/pull scheme is possibly damaging to the drivers. Suprisingly enough though the setup yielded dramatic SPL results with these below average woofers, and only an A8000T powering them.(I know a majority of people think audiobahn sucks, but this specific amp has never wronged me, and always pounded whatever I put to it.) - Anyway any suggestions on ways to improve upon the design to achieve more SPL output before I carpet it, And what's going to be the cheapest way to stop the horrendous vibrations in the trunk would be greatly appreciated. I've used dynomat on the lid of the trunk to no avail, a small improvement but not enough. There must be a better way, also someone suggested dynomatting the inside of the port, is this practical? Thanks in advance, just trying to learn a bit here. I'll try and post a picture as well, also it's in a 1996 accord C27.



Late,
Jeremy

Ok, apparently my attempt to include the image didn't work, here's a direct link:

https://www.uniksystems.com/f2/pushpull2.JPG

Sorry about that.

If they are a shared chamber and port you should have them both wired the same...as in not a push pull...a push pull is for a sealed box am I right? (correct me if I'm wrong)

Try mounting and wiring the subs the same and see how it sounds.

Also what frequency is the port tuned to...If you want spl than tune it for spl.

Dynamatting the inside of the port will not do much as long as the box is rigid enough.

Brown Bread is a cheaper solution than Dynamat. You can put silicon caulk inbetween the trunk lid and trunk skeleton to help with rattling andvibrations. But more sound dampening material is probably what you need.

Anyone else?

Ah, I did try this first, I've tried every config(both inverted, both forward) this one yields the most SPL which is what I'm looking for, and has a tad bit more punch to the sound, I just don't want to break the drivers if this is bad for them. I suppose sealing the outer rim of the inverted one would be a good idea as well, I haven't gotten around to that yet though, still experimenting. Thanks for the reply, I read somewhere it works in ported boxes as well, not this specific type, but nonetheless I could be wrong, I'll see if I can find that website..

Jeremy

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Jeremy

powerprecision AV

Oh, and the port is tuned to 31hz if my calculations are correct.

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Jeremy

powerprecision AV

Trying to post this picture one more time... bear with me :)



there we go.. I think..

Well if your looking for mainly spl than build a new enclosure specifically for spl but that is built upon the specs of the driver.

You can use WinISD which is a free box building progam and mess around with numbers until you get what you want.

I just noticed that the port walls are doule thickness so whoever said dynamatting the inside of the ports would yield higher spl numbers is basing that statement on pure BS.

Also I noticed the speaker wire coming through the port...Why not just drill a hole in the back/side and seal it up with some caulk. Having a very good seal between drivers and box is a must if you want to get all you can out of it.

31 hz is kinda low for SPL too.

Well, this is my second attempt, so of course it's going to lack perfection, I used WinISD to the best of my abilities, along with some other calculators using the T/S params, but for all I know I completely messed up. It is extremely loud in it's current state, I cannot read street signs, etc at high volumes which is kinda annoying honestly. It almost overpowers my front stage, which consists of coaxial alpine SVS 6 1/2", 2 1" dome tweeters(factory) powered by some cheap 150RMS amp, I'd have to look at the brand. I tuned it to 31hz looking for the low response and to maintain SPL, but I think you're right it is kind of low for SPL, but I am still getting a good amount of it, heck the tuning may be higher than what I calculated, especially inverting one of the drivers causing less displacement as I designed it to have both inverted. I intend to go buy some silicone tomorrow and seal around the inverted driver, the reason the wire is running through the port is due to the fact I don't have any silicone at the moment so I don't want to drill a hole quite yet, may do that tomorrow as well. I did kinda figure the guy was BSing me, he works at this kicker shop called audio connections.. don't think I'll be going there for advice anymore. I really appreciate your advice though, you seem much more educated than the quack I talked to at that store.

take it easy.
Jeremy

Lol he was most likely wanting your money. When talking to a guy at a shop about a problem and the first thing he says is to buy something than he/she most likely wants your benjies.

Well it's late and I gotta go to work tomorrow morning.

Always enjoy helping another audio enthusiast.

Peace,
Dom

1.  Use minimum 3/4" MDF for all walls.

2.  A cross-brace should be secured from front to back in the center and also top to bottome.  You can use cross braces on each side of the port structure.

3.  Wire the inverted sub in opposite polarity than the normal one.

4.  Smooth the port opening edges if you can.

5.  The port should terminate inside the box at least about 3" from the back, or any, wall.  And it needs to terminate into the shared air volume of both subs.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Appreciate the response, when you say smooth the port, should I take sandpaper around the edges to more or less flare it out evenly?  And adding cross braces may be a pain at this point with all the wood glue, torx screws, etc, but if it will help substantially I'd be willing to do it.  The box is all 3/4" MDF btw, and out of curiosity what effect does it have on which sub I wire out of phase(inverted, or non)?  The port terminates 2.5" from the rear wall of the box also,  and what exactly do you mean by terminating into the shared air volume of both subs, just equally? - Anyway, a lot of that would probably be a pain to change, I might as well build another one opposed to all these modifications, I might just run out and get another sheet of MDF, I definitely appreciate the help, keep it coming :).

Jeremy

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Jeremy

powerprecision AV

Terminating into the shared volume as in the same chamber as both subs are in...Your good though on where your vent is.

Smooth out the edges of the vent i.e. flare out the ends a lil bit.

You could build "the wicked one" from decware.com

This box will probably yield more spl than your current box. But it is a little tricky to build at first.

Cool, about to go start sanding on that, I don't really have any port noise as the velocity is pretty low, but if it helps it's worth a shot. I like that wicked one box, heck I like a lot of those boxes decware has on display, nice site thx for the info there. Bandpass boxes from what I hear are not forgiving and difficult to build so I can understand that. And oh, a question, rather than rewiring the inverted sub to be in phase and the other not, couldn't I just use the 0-180 phase shift switch on my amp? Thx again for the help.

peace bro,
Jeremy

Oh, and one other question, will flaring the port have any effect on tuning frequency?

You can't use the 180 switch because it reverses polarity on both subs that are hooked to it.  You can change the wiring polarity on either of the two subs, just as long as one is opposite in polarity than the other one.  Once that is done, you should experiment with the 180 switch to find the best overall phase (output) with the rest of your system.  About the suggestions I made, I thought:  1.  That you were already going to build a new box, and 2.  That the pic made it look like it was built out of 1/2" stock.  Bracing would be a big pain to do in this finished box.

As for flaring the opening:  as it looks now the opening is squared and looks a little rough.  Putting a nice roundover edge on it will smooth port turbulence and lend a more professional touch to it.  Fb won't be affected.  But 2.5" is a bit close to the back wall, IMO.  There is an amount of airspace needed at each end of the port that actually functions as part of the acoustic port length.  The general rule of thumb is to leave the equivalent of the port diameter (when talking about a round port) to be sure you've allowed for ample space for true port function.  Since the equivalent round port diameter is much wider than the narrowest width of your slotted port...it would be in the neighborhood of 5 or 6" I would guess...I suggested a bare minimum of 3 or 4".  I would design it to leave 5 or 6", and that would be determined by finding the equivalent round port diameter first.

And you know you must do something about that wiring coming out of the port.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Yeah, the the wire running there is temporary, I just need to get a terminal block and get out my hole saw kit. Does this have any adverse effects on performance? And btw, I already wired them out of phase electrically so they would still be in phase mechanically, I just wasn't sure from what you said earlier if it mattered which driver was reverse polarity. So the rule you are talking about(port distance from back of the box) applies also to slot ports? Man you guys know what you're talking about, wish I would have discovered these forums sooner..

late,
jeremy

Ok, subs are already wired properly then.  And yep, a port is a port.  Here's an illustration of the acoustic port length vs. the actual physical port length:

I don't know any math to calculate the actual space needed, so I just use the rule of thumb I mentioned.  What you have may be enough and it's not something in itself to have to build a new box to change.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Well tdeath that wicked one box is not a bandpass box...it is a horn loaded enclosure. Normal bandpass box is a one not wonder. The horn wicked one has a repsonse frequency of around 20 up to 100 hertz. And it has a higher effieciency so you may get more outta your subs.

I need to get some new subs, I just don't want to lose the warranty on these...can't beat that lifetime warranty(because they're bought from walmart and all :). My friends and others tend to laugh at the speakers though until they hear the output exceeding what they have, which wasn't possible until recently as I had them in a sealed enlosure before and blew them both up frying the coil on one, and some how the spider disconnected from the cone on the other(?); never had that happen before. If I wasn't worried about wasting money(a little short on it now..) I would go get some new drivers, but until I do I will probably stick with this box, Ima go buy some sandpaper now do a little touchup here and there, and then carpet it.. I think it will look much nicer with the carpet.. How can I tell the effeciency of my enclosure? Anyway, thanks again man.

Jeremy