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Old 28th July 2003, 12:19 AM   #11
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Join Date: Jun 2002
Location: NH, USA
Careful with designing port lengths using WinISD. My versions of WinISD all gave me incorrect port lengths.

They're are subwoofers out there that act as isobarik subs, but are only one sub. They're ususally car subs. Car subs of course are designed for small boxes. And can be obtained at better quality for less than half the price of home subs I've noticed. I was going to get a pair Credence 15" subs (same as Kicker Solobaric S15D) for $120 and still might. I bought a pair of 500 watt amps with a fix 24 or 36 db/slope at 100 Hz. I wanted to make subs but like you size is an issue and I have no room for individual subs I think. Maybe I will make an isobarik design, seems kind of though.

Also why don't you try an aperiod vent for your subs. Won't cut your box size in half, but by about 20% I've heard. Forgot you were making a vented box for a second, but a good thought I think.
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Old 28th July 2003, 04:02 AM   #12
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hmm.. you coulda gotten 1 Peerless XLS car sub....... small enough box.... alright efficiency..... hmm lol I am really just increasing my post count...
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Old 28th July 2003, 05:50 AM   #13
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most people like the idea of a small sub, but it's so much harder to get a nice response out of 'em. with those two subs and that amp i'd be playing around a lot and having fun.

whatever u do, with the high sensitivities of those things and the power u have for them, they'll make a hell of a lot of noise. have u ever heard big sub systems before? if not, you probably went all out thinking that one wasn't going to make enough noise, and you're gonna get a massive surprise from the volume they'll create.

with 'smaller' box sizes, vented wont be of all that much advantage, and i'd go sealed. i'd build two completely separate 60L sealed enslosures for them - but make them so they stack very neatly, making it difficult to tell that they're separate. maybe go to a rubber supply store (i go to clark rubber, dunno what u have near u), buy a good roll of it (it comes in use so often!) and use that to prevent vibrations.

i know the curve may not look super impressive, but room gain it will sound quite good, and to get much out of those subs vented wise you'll have to go to around 100L - per sub (that is, to get much advantage over sealed). but this is of course just an opinion
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Old 28th July 2003, 11:12 PM   #14
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Careful with designing port lengths using WinISD. My versions of WinISD all gave me incorrect port lengths.
Ditto. In my experience the tube lengths were too long.
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Old 29th July 2003, 10:25 AM   #15
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The main design concerns when i started this project where:

1: The size. The width of the area where this sub is going only allows for a box about 400mm (~16") wide and about 450 (~18") deep, that's allowing a for little bit of room eitherside for air moment. I could have gone as high as i wanted but i did not want to go higher than my tv, rack and speakers, they are all 900m ( pretty low ~36"). I guess i could have made a box about 119 litres -(amp+bracing) but i would never have made room for a 15" in this space.

2: Freq, wanted to get at least down to 25hz and if possible a hint of 20hz.

3: Wanted it to stay tight, read somewhere a group delay under 22ms was ok.

I think i did ok, but what do i know? i have never done anything like this before so??

WinIsd did calculate some port lengths for me but they did not have the right diameter port so i went and tried a few other online calculators. Most were within 5% of each other but they all showed different answers. My best bet now is start with the longest length and test it then cut a little off then test it again..ect..ect.

I have been raving on too much so here's a picture:

Click the image to open in full size.

Lucky they can go together without a spacer and don't touch when fully extended...unlucky the slits in the gasket leak, was hoping for a air tight seal. May have to gently remove the gaskets and make a hard rubber ring between them, or maybe just glue the slits up?
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Old 1st August 2003, 09:13 PM   #16
hifidan is offline hifidan  Canada
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Hi ,
I built stereo subs using a 2 Peerless 8317 10 inch in isobarick config. You can see the result at

I designed the box using WinISD 75 liters ported, 4 inch by 33 inch. I drive them with a Parasound HCA-1500A (302 wpc/4ohms). I tested the in room response (RS soundmeter) to an F3 of 23 Hz at 97 db before I can hear port noise. I located the subs on the inside of the speakers to stay away as much as possible from the corners( standing waves) in order to get the best integration with the JM Labs Integra 905. As you can see, I pout the port at the bottom, to get more Umph since i'm not using the corner of the room. Also, the Moon W-3 has been changed for an YBA 2 HC amp which is a lot more musical and satisfying. Stereo subs help reduced the strain on a single driver and help re-create the image of the stage a whole lot.
The subs are really good for music but lack the punch for HT at high volume. I'm planning an HT sub using a 10Peerless XLs and 2 Passive radiators. (See for plans)
Happy listening
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Old 1st August 2003, 11:49 PM   #17
BAM is offline BAM
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Use a rubber ring around the woofers' gaskets or something. Don't use silicone caulk to connect them, because they will never come apart intact again. I made that mistake with my first sub.
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Old 3rd August 2003, 08:01 AM   #18
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Originally posted by BAM
Use a rubber ring around the woofers' gaskets or something. Don't use silicone caulk to connect them, because they will never come apart intact again. I made that mistake with my first sub.

I decided to use a bit of silicon seal but only on the speakers sealing ring where the splits are. I let it dry and it wont glue itself to the other speaker, have not tested the seal yet but it should be ok, not sure how well i'm ment to seal isobariks anyway. Spent most of saturday down the back shed gluing and screwing the box together. I did make lots of silly mistakes but in the end it should not effect how well this thing works? i hope.

I found out when power driving in chipboard screws (about 100 of them so far) that a little drop of pva glue down the pilot hole can act like a lubricant and help the screw glide in much better, i'm sure it will help it stay in it's place also.

Inside showing the top of the inside driver:

Click the image to open in full size.

The back of the box, this lower bottom port/vent show allow the bottom driver to act as if it's in free air..i hope, it's big enough to allow a heap of air through it so it should do the job.

Click the image to open in full size.

This is a side but it will face the lounge so that's where the remote will go for the amp, notice how grubby the box got, should really have cleaned my work bench down first, I will as soon as i mow the lawn honest :

Click the image to open in full size.

The port will probably go at the top as i think that's the most effective place to put it but i don't like the idea of a grille and i could just see my car keys falling down and getting stuck to a big magnet so i will probably put it in one of the sides and use a big pvc elbow? who knows just yet.

Please let me know if these images are too big and i will just link them, i was not going to post them untill it was all finnished but after seeing skinny boy's box i was less afraid to
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