A new Baby in the house.

[masterjr33]

I'm working on my first subwoofer for home use and I just bought the guienni pig.
Here are a few specs.

15 Inch.
2ohm DVC
Frequency response 16-300hz
300W rms/coil, 700 dynamic
RE 3,2
QMS 6,37
Qes ,531
Qts ,49
Fs 20hz
Vas 157
Sensitivity Watt (90db/1m) 1.6
Mounting depth 167mm/6.6inch
Installation size 348mm/13.7inch
External diameter' 388mm/15.2inch

Basket: Cast alloy basket
Cone Material: Treated paper diaphragm / Poly parabolic dustcap
Voice Coil: Dual 2-ohm voice coil
Former: Kapton®
Terminals: Gold binding posts

Recommended Box 1 (Vb): 1.50 cu. ft. sealed.


I would actually like to build a large ported box with a square port on the bottom wrapping around the inside and around the back of it to get the correct length.

If anyone can take a stab at the rest of the parameters it would be nice. I would like to plug this into WinISD and get to work on a box design. I'll post a few pictures when it finally shows up. Looks like fun for 38$.

[Nanook]

what driver is it?
Guessing sux. A port, based on info provided won't do anything good for it or the sound. Essentially the same response, with less good impulse response will be the result. Why not follow the recommended sealed enclosure?

[ocool_15]

From the specs it works better in a sealed box. I tried ported and it works ok but requires at at least double the volume excluding the port.
You really can't guess at the other parameters. You can derive some from others through formulas. What other parameter do you think you require to get a start?

This appears to be a subwoofer optimized for in car in a relatively small sealed box.

[richie00boy]

With a Qts of 0.49 that's going to need a biiiig box if you go vented. Again what parameters do you think you need now? You can measure D and calculate Sd from that. Xmax you probably have to conservatively guess.

[masterjr33]

Well I was hopping for a bit more extention from it with a ported box, and size doesn't matter. I would like to get enough numbers to plug it into WinISD and the company doesnt have any electro-mechanical figures for it. I know the mms would have to be a guess since it has a add-on parabolic cone and I am going to have to use a conservative xmax guess. I just have no idea on most of the other figures and I assumed a few of you fellows might have seen some drivers like this and may have a decent ball park figure. If I do go sealed with guessed figures it wont be as easily screwed up.

It's a MB quart Reference sub contracted through Rockford. Model RWE 352 parabolic cone with an inverted surround. I thought it looked nice and for 35$ plus tax for a NIB unit I don't have alot in it.

This will mostly be used at home for watching TV and movies. My little 8 inch cerwin vega just doesn't have the depth I would like. It really starts to drop off under 40hz. I'm looking at either a Bash or Apex Sr. to do the job. Also I sourced around for any info on sono-tube locally and I found a place almost willing to give me a few 24 inch tubes. Either that or a larger square port as mentioned before. A sealed box just seems a bit to simple and I wanted to try something different, with your expertise and my boredom I'm sure something can be put together. Thanks Again.
Justin F.

[ocool_15]

I was having problems finding that spec. Rockford used to own mb quart but looks like maxxsonics might now. Not sure who you would contact then but I'm sure its available.

I would expect it to be higher then 350g more like 745g but you can't really guess at mms. Can you look at the model that replaced it?

[masterjr33]

Well i contacted Mb quart and got nothing. So I tried Rockford. They said to call the tech line. The tech line said called Maxxis and Maxxis said to call rockford.

I'm trying to put some of the figures into WinISd and it throws some other figures off. It keeps on insisting a 192 MMs and a VAS of 338.07. I plugged in a mms of 550g but I till try higher. Also I used 16mm as the Xmax with 17mm for Xlim, I hope these are conservative. For some reason I keep getting a 12ohm curve.. I guess the figures I put in for the nom and Re are off :-)
But playing with it so far I get something decent looking with a 8Ft box with a tuning of 14 Hz. with 300W the cone excursion doesnt go crazy and I'm over 3Db better at 40hz and over 7db better at 20 Hz than using it in a 3.5ft sealed box. 3.5F is as large as I can go and keep the cone in limits, but even that produced a 60hz bump and alot of roll-off after 40 hz the recommened 1.5 box is much to boomy witha HUGe peak at 60hz.

The sealed box is +1.14 at 63 and down 3db at 35.
The vented is +.59 at 60hz and down 3 at at 24hz.
At 20hz the sealed is -13db and the vented is down 5.5.

So far I dont mind the graph at all for the vented. I still need to hunt for more specs but unless some is very very off that will be the way I go.
I ballparked some based on the Pheonix gold Xmax15 and the JL 15W6.

Thanks
Justin F

[ocool_15]

You can always provide active equalization. I run a single 10 in 1 cu ft with 10dB active gain at 18Hz(Its different then just a equalizer). Of course my maximium output spl is less due to thermal limits.

Active boost like that makes smaller boxes much more practical. It would be nice to know if this is a linear(Very likely) or a progressive spider.

[masterjr33]

Well. its a linear spider. BUT! it does have a fully vented spider above the magnet. To bad I dont have 2 of these. witha .49 QTS 20Hz FS and a 21mm Xmax it would almost make a decent diapole..
ATM I'm considering a box as described in the attachment.
If not that , then I'm going through some thoughts in my head as how to make a sealed/ported box. A large ported box with a baffle and cut off plate towards the middle to make it sealed when I want music and ported when I watch a movie. A 3.5C/F box looks good on winISD and so does an 8Cu/ft box. I already have a build design in my mind of a 3.5Cu/ft box with a baffle opening into a 4.5 open area with ports. I have a sealing baffle design I want to try. Just trying to figure out a way to move the sealer about 6-8 inch in a linear motion easily from the out side of a box and if I want to go mechanical or electrical.
I will try and stay posted on any progress. Right now my cash flow is slowed up while im looking for a replacment turntable.

[francis varkey]

Well I was hopping for a bit more extention from it with a ported box, and size doesn't matter.

May I suggest a wave cannon aka B%$&.
It is a two tube set up. The tube internal area should be around the same as the driver's cone area. I would prefer the tubes to be unstuffed.
One tube(length a quarter wavelength of Fs) which loads the rear of the driver and the second tube(1/3 rd the length of first tube) loads the front of the driver.
You could fold the rear tube into three equal parts.
Attached is a beautiful sketch...