Hi Guys, im just about to embark on my first DIY sub for my HT room. At the moment the component i am looking at using are the Exodus Tempest X2 along with the parts express 500w bash amplifier.
Currently I have got a wooden chest made out of Meranti wood which looks very similar to the photo ive attached, i have read a lot about not using hardwood for a sub box but what i was going to do is line the box with a mdf box, the sub will be downfiring.
The chest is around 6.4cubic feet, ill add the exact dimensions when i get home.
Would the best option be to have the sub downfiring and have maybe a few slot ports.
I Will try model it in winISD later on tonight, does anyone have any opinions about doing it in this manner? what thickness mdf would i have to use to line the chest?
That will depend on the thickness of the material the cabinet is made out of. Post the external dimensions of the chest and the thickness of it when you get a chance.
The Bash 500 will need the hi-pass filter changed, its default is 30 hz which is too high for a ported sub.
Depending upon the thickness of the box, if you add some bracing, it could be fine as is. You'll need feet for downfiring as Mike said, but a single slot port of adequate cross section will be fairly long, and can be a part of the bracing as well. Search here for the 'Easy Button' sub threads to see how this is implemented. Another concern not knowing the construction might be the sealing of the box (air tightness) but a coat internally with shellac or some other product should cover that, and will likely aid with wood movement with temp and humidity, which can be a problem for some hardwoods and is why they are usually not recommended.
I've seen other threads for sub construction using a similar idea, but don't seem to have them bookmarked. I'm sure at least one was here. If I can recall them, I'll post links for inspiration.
Ok here are the WinISD graphs, can all of you check to see if ive inputted the right values?
Ive used a 6.09ft^3 box @ 20Hz, that is the dimensions of the inside of the box, do i need to subtract the port or is that calculated when i enter the port dimensions? Also do i have to subtract the driver and amp volume?
Do the grpahs look good if all of my values are right? the box needs to stay the same size but the port size can change if you guys think so.
The box internal dimensions are 35.04in (w) x 20.08in (d) x 14.96in (h)
It will be closer to 5 cu.ft after you subtract the displacement of the port, sub and bracing. The sub can handle the 13.9 hz HPF from the "1 db boost table" of the amps documentation. The port air speed is 22 m/s which is good.
OK well, i cant use the parts express 500W bash amp, becuase they are only 120v, as im in Australia i need a 240V amp or an amp which is switchable. Any ideas of something similar, i was looking at the O Audio amp but i dont think the high pass filter reisitors can be changed as they can on the parts express amp.
Also from my graphs the max SPL is around 116dB, this is using a 500w amp and a 15" tempest driver, how is it that a Krix sub with a 11" driver and 220w amp can produce 122dB?
It could be creative specmanship or , but without a link to the sub you're referencing, it's very hard to tell. My educated guess is that it won't go low at 122dB.
I like the idea of th chest sub, i think it will be cool btu i'd want to hide the sub and the ports which i'm not sure if a down firing port is a good idea as i think it would be the same diffeance as putting the port near a wall'
Now that ive got the confirmation that it will outperform the Krix ill go ahead and start getting the components.
I will model the box and post what it will look like so everyone can have their opinion on if it looks ok.
The i need to decide on the amp, im guessing the behringer will be much better than a plate amp? am i correct in saying this? Im just deciding on whether to spend $300 on a plate amp or will the extra $200 for the behringer will bring a good improvement?
Very imaginative specmanship on the part of Krix for that one I think. A pair of Tempests will eat it.
The Behringer will let you drive each driver to full power using one channel/driver and will give a very worthwhile SPL increase capability over the PE BASH amp.
You'll get the most of the subs capabilities with a Pro amp due to the increased power output. While a plate amp has a hi-pass filter built in, the pro amp doesn't. You'll need to get a Reckhorn B1 for a hi-pass filter.
Don't you mean low pass? That will be needed unless John is just going to use the LPF in his AVR. A HPF can be done passive line level for the cost of 1 or 2 caps and resistors (so can a second order HPF too) soldered into the connecting RCA cable.
You'll get the most of the subs capabilities with a Pro amp due to the increased power output. While a plate amp has a hi-pass filter built in, the pro amp doesn't. You'll need to get a Reckhorn B1 for a hi-pass filter.
So I need a high pass filter, does this go between the amp and the sub? And then i guess the receiver looks after the low pass which i can set to 80hz or 100 hz from what i can remember, is that right?
It looks OK, but also looks like you have a HPF in place for just below tuning. Is this correct and what frequency and slope? And at what power were you modelling?
Whilst at Bill's site grab his Boxnotes software as you might find it of use.
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