Build Advice

[a1161979]

Hi all

I was wondering if you guys can help me with my next little project, i currently have one driver in a vented 150L box tuned to around 27hz which is a one note wonder that sounds bad for music and i can bottom with ease on movies such as War of the Worlds and Transformers But i was 17 when i build it buy my self and in reality it still out performed the Klipsh 10 that came before it. Ill post pictures and a REW graph this weekend (and you'll see nothing really bellow 20HZ)

Now onto the guts... i currently have two of these drivers http://www.subwoofer-builder.com/driver-CS-2345.htm
Here are the specs

Znom Nominal Impedance 4 ohm
Pmax Power Handling 250 watts
SPL Sensitivity 88.48 dB/watt@1m
Re Voice coil resistance 3.5 ohm
Fs Resonant frequency 25.65 hz
Qms Mechanical Q 3.552
Qes Electrical Q 0.578
Qts Total Q 0.497
Vas Equivalent volume 150.7 litre
Xmax Maximum excursion 15 mm
Sd Cone Area 750 sq cm

Nothing special really but the budget doesnt really extend anyhigher not to mention that currently the 8inch sub i built is pushing the MAF (mum acceptance factor) to the limit

Anyway after a few hours mucking arround i have come up with two options, the first is both drivers in a 320L sealed box while the second is one (with the other spare) in a 320L box tuned around 15hz. Some questions are
1) Tuning far bellow FS ie 15hz tune for 25hz FS is this ok, if not why?
2) When i tune to 15Hz in order to get a reasonable port velocity the resonance is around 130/140, although i understand this is not ok why not... what are the auidable effects?
3) With a sealed box with twin drivers should i give each sub its own airspace?

I was thinking along the lines of both sealed with a qtc of .7 stuffed (aka 320L which is in reality the largest i can go) I was also thinking if i run into more funds the Tempest X drivers that are available downunder would perform well in that enclosure meaning i can upgrade in the future without having to build another box

The sub will be used for 80% movies with 20% music... i have a BFD, REW etc so fire away Ill post a build thread here when i have decided

Thanks in advance guys

[hddummy]

Looks pretty good. I think I would go for the dual sealed design. I'm a firm believer that more radiative area is almost always a better solution. You can always boost the low end a little (3dB or so) if you want a little more punch.

If you do go with the ported option I would raise your tuning to about 18Hz for a more reasonable port length.

[Ricci]

I 2nd the dual sealed option. Why not try to use both drivers if you already have them?

[Mike P.]

Not much room for boosting the low end with this subs limited power handling of 250 watts. A 3 db boost would require twice the power.

[Warmon]

a1161979 wrote:

3) With a sealed box with twin drivers should i give each sub its own airspace?

There are two main thoughts on this; one is sharing the same space can equalize any slight manufacturing differences in TS parameters and result in a better sounding sub. The second is give it's own airspace - should one driver fail suddenly, the other can keep going with no damage by finding itself in a box twice the size. Most folks recommend the latter...then again, many sealed combinations such as push pull share the same space. YMMV.

[a1161979]

Ricci wrote:

I 2nd the dual sealed option. Why not try to use both drivers if you already have them?

The sealed option is with both Drivers, 300L total or a Q of 7 which i will then stuff with polyfill

I dont really have the space, i could build a 600L box for both vented but that isnt really on option. Currently the TV resides on an old antique chest that measures 500mm by 650mm by 1100mm which gives a volume of around 300L, now mother insists it not be any larger than this I tried to model both in a 300L box but it begin to look like a boom box with a large hump around 30-70hz and little bottom end, besides i currently have one in a 150L box (although tuned much higher at 27hz) and i dont like it... For vented these subs really need volume of 300 to 400L each for home theater use

Sounds like the sealed subs are the go then... Just thinking but currently there is a DIY 8inch sub which does quiet well for HT despite its tiny volume and 37hz tune, the room has LOTS of room gain, ill try to find the graph of the 8 in there but i dont think the highish rolloff of the sealed sub will pose too much of a problem

[hddummy]

If you have a lot of room gain, that will definately help your low end response and make up for the roll off of a sealed sub.

Am I reading you right, that you are planning on putting your TV on top of your sub? I hope you don't have a CRT.
Regardless of TV type, you should try to put the drivers on opposite sides of the box to reduce vibration as much as possible.

[a1161979]

Nah its LCD, it will be on spike and heavy, well braced and stuffed so im hopeing it wong be too bad