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band pass sub

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Young Croc
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    Posted: 04 June 2015 at 2:25am
Glue is drying on my 6th order band pass sub prototype. If it works I will make 4 more. Designed for extending the sub in use with my 1850s. 

My goals were economy 30hz with a decentish efficiency, and the driver needs to be reasonable and obviously sim well for me to take a chance on it. My driver for the design was the Eminence Definimax 4018LF. There are better drivers, but it simmed decently and did not cost scary amounts, and recone kits are readily available. In the past I have mostly used european drivers, and I have not blown any (yet) but recone supplies are much more difficult to obtain and the cost include a hefty import price tag so this time I tried to go domestic instead.

Secondarily, I wanted to make the access panel removable to allow the rear chamber to be used as a standard reflex box, with a slightly awkward waveguide where the front chamber would have been. I feel like it can work though, so here's me trying.

I mostly used WINisd, but tried some other programs too to verify the predictions and get more detail. I simmed it as 12 small vents per chamber, as I feel they will perform better than giant but thin sloppy unbraced slot vents. The build is rather easy (at least compared to the horns I have been making lately), but it takes a long time. There are 52 pieces per box. 

Currently waiting for the glue to dry and my drivers to arrive. I will round off the vents and test the sound before I make any more or paint. I am not sharing plans right now, as this is an experiment and I don't even really know if it will work right yet.

Internal view.

Rear. The large handle on the back is also the recess for the speakons.

Reflex mode (Sans access panel). When the access panel is removed, the front vents just become braces. With the panel on, all of the air will be channeled through the vents above and below. The rear vents are the vertical rows on the right and left.

With the access panel in BP6 mode.  Should give about 6 db extra sensitivity at 40 hz than the reflex mode. Obviously sacrificing anything above pass band. 
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Young Croc
Young Croc


Joined: 05 October 2012
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 2:32am
In Bandpass mode the F3 Passband is calculated to be 30hz to 100hz.

In Reflex mode, the lower f3 is 35 hz. 

Front chamber is 70 liters tuned to 66 hz. Rear chamber is 190 Liters tuned to 31hz.

External dimensions are 63.6 cm (to match the 1850s for stacking purposes) by 71.2 cm by 78 cm deep. It is big. Not as big as the 1850s though. Unloaded, I would guess it weighs about 100 pounds.
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Shaun View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shaun Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 3:49am
Nice design and a cracking bit of wood work there, very sharp
No, it is not a line array it is some well stacked boxes...............
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 4:26am
Thanks. :)

Drivers are here. Glue can't dry fast enough.
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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote colint Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 5:58am
despite if it works or not it's nice to see someone trying something different on here instead of the same cabs being done over and over again or will this driver work in this box threads.
Looking good hope it works for you!
To steal ideas from one person is plagiarism. To steal from many is research.
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Young Croc
Young Croc


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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 6:17am
Thanks. I hope it works out too, but even if it did not, I have vastly improved my wood woking and conceptual design skills. My biggest concern is that all of the different programs I tried seem to have different numbers for the vent lengths for the tuning I was shooting for. In the end I just went with the WinISD numbers and am hoping for the best.

Whether it is a success or failure I will be sure to post my observations.
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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote all bass Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 6:54am
Nice design work.

Do you have the equipement to measure the cabinet and adjust vent lengths if needed?
Get your free line array plans here!
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 3:04pm
I do not really have proper measuring equipment, but I can get a halfway decent spectrum using a DAW and Spectrum Analysis. If the vent needs shortening, I can get in there and make them shorter, but it will be messy, so I am hoping it performs properly. I don't think they will need to be longer. I can only remove about 3 cm of vent from the rear, but I could remove up to 12 cm from the front. Both of those changes would also change the volume as well. what would be hard is getting in there and re rounding the insides of the vents. Moving target. I really just want it to work. If the results are even close to my predictions, I will likely accept it for its shortcomings.
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 3:06pm
Then again, I could replace any volume changes caused by the vent editing with more braces equal to the difference in volume.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shaun Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 4:12pm
the other option to changing the speaker cab is alter your expectationsThumbs Up
No, it is not a line array it is some well stacked boxes...............
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2015 at 4:58pm
Honestly, that is my whole philosophy of life. If I miss a target, then I move the target to where I hit. LOL

Really though, reducing the volume of the enclosure can also raise the tuning, and since I am not right at the smallest chambers the speaker can deal with, I have some room there. So if I need to raise the tuning, I will probably just subtract volume by adding more bracing. At least I will try that before I start butchering the vents.
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote b grade Quote  Post ReplyReply Direct Link To This Post Posted: 05 June 2015 at 12:02am
Just test loaded the driver and listened to it in reflex mode. Access panel is the last bit I need to quarter round, but I had to go pick up my kid so I threw it in the back of the van and hooked it up. I had only like 150 watts to play with in the car, but it sounds clean and low. No measurements but it sounds like it is tuned at least semi competently in the rear chamber. Will get it on a proper amp later tonight and see what happens in band pass mode.
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