need to get subbed (verry newby)

[obtuce duce]

Hello all,
Total 100% bran new newbe here. I just got 5.1 surround. I am blown away! I just hate that it took me so long to do it! I now have developed a... disorder maybe? Some kind of sickness? I found this site while looking for a cure; instead I found a bunch of others with what look like the same symptoms! I love this place!
Anyway, I have a question; I want to build a sub. Done a lot of reading on this site and another one and it seems like most of the sub threads get kinda technical. On the other site they even seem to argue with each other and sometimes miss the point of the question asked. This is why I am posting here.(and the Rotel pics).
I borrowed a Velodine VRP-1200, Around here it is a $350.00 sub, It’s performance is acceptable, I would like a little more output at higher listening levels, and would like to ‘feel’ more...another symptom I guess!
So, on to the question; can I build one for that price that will sound as good? I was looking at Parts Express, they have a Dayton 12 and an amp that total around $210 parts 295-555 and 300-794. I also like the Dayton 295-404 and amp 300-806 they total $450 though. Is Parts Express good to deal with? Are they good with their warranties? Tech support?
I want to build my own, to save a few $ and for the experience.
It has to be a box, ported, and not firing down. I don’t really know how to figure the size of the box, or the port.
If you guys find the time, after reading this here novel (sorry), I would appreciate any feedback you can give me. If you tell me wat I need to get and do, I’ll go get it and do it! I have the skills and tools to build the box. I would like to use the sub for many years, if after some time I need more, I would like to add, not replace. I am planning to build my own rack also, (chromed steel and aluminum). It should boggle the mind when finished! Just godda help the wife understand, we NEED this stuff.
Thank you all for looking.
Respectfully,
Obtuce Duce

[Paul H]

Just a few comments here to get you started:

I just built (and am happy with) a tempest sub (214 litres, ported) which is described in this paper:

http://www.adireaudio.com/Files/VentedTempestApplications.PDF

Forum sponsor Parts Express also has some good subwoofers, and suggested box designs - click on the link at top/bottom of the page.

You can download and play with Unibox to see how box sizes and types affect sound frequency response - it's an excel spreadsheet based simulator.

I'd suggest whichever speaker you go with use a 15" rather than something smaller - the cost difference is virtually nothing and the larger driver will move much more air, providing lower cleaner bass.

If you can provide some info about room size, listening habits, etc you'll get some more specific recommendations.

Paul

[obtuce duce]

Thanks Paul,
I enjoyed looking at those plans. I like the SBB4 design. That is what I want, except I want it to shoot ‘out’ not down. I did not realize that they had to be so strongly braced inside. Would that box work on its side? If so, I could just build it without legs and be done. What speaker and amp did you use? Where can I find more plans?
The room is approx, 12’ x16’ with the front right and rear right corners open. The front is a hall; the rear is open into the dining room. The TV is at one end and the couch is at the other aginst the rear wall. Due to political circumstances the sub will be permanently placed beside the left front speaker. Though it has been all over the room and sounds best on the left side wall about half way between the TV and the couch.
I would say that we listen to more music than movies.
Thanks,
OD

[Paul H]

Jason,

The tempest sub I built was based on the "adire alignment". It fires horizontally, and as you suggested is just built without legs.

I made some changes. First I put 1-4" port rather than 2-3" ports, and adjusted port length accordingly (using information from unibox). Also, some dimensions were changed slightly, but the internal volume is unchanged.

The unfinished (ie unpainted/un-veneered mdf) product is in the attached thumbnail, hiding behind one of the main speakers.

I use a crown com-tech 810 amp (approx 300watts per side) which I picked up from ebay. I had an old cheap 80 watt (claimed) receiver around which I tried out of curiousity, but it didn't have enough power to drive the tempest properly. The crown is more than enough.

The whole setup has lots of "oomph" for movie-watching in our 24 x 17 room.

The tempest is just one driver by the way - there are many others. Look on this forum for a thread about new drivers from Ascendant Audio - they look exceptionally good for the price, and designs for the boxes/porting are available if you don't want/don't know how to do your own design.

Paul

[ThomasW]

Jason,

Most subwoofers don't care how they are oriented so upfiring, downfiring, or sidefiring, it really doesn't matter.

The 12" Titanic MKIII is a nice sub. IF you can swing the extra cash for the 15"MKIII, it's a better 'deal'. It will play louder with a smaller amp, and moves almost as much air as 2 of the 12" drivers.

None of these big subs are shielded, so either size MKIII will probably need to be 36" or more away from a standard TV.

The boxes need to either have very thick walls, 1.5" is standard for DIYers. Or they need a ton of bracing. If the walls of the cabinet vibrate, those vibrations cancel the sound coming out of the driver.

The 'ideal' box should sound like it's a block of solid wood, if you rap your knuckes on it.

[Andrew Pratt]

The boxes need to either have very thick walls, 1.5" is standard for DIYers. Or they need a ton of bracing.

Or better yet both

My advice is buy the biggest driver you can afford even if it means for now putting it in a smaller box then idea. You'll very likely want to upgrade any 12" you buy so you might as well start off with a 15" I've been down that road before and always ended up selling off the small driver to buy a larger one...and then sold that and then sold that etc.

[obtuce duce]

Ooo kay,
Well... I think I can see where I am going now. Thank you for the picture Paul. Your front speaker looks awesome! That would take some real talent.
Thomas, thank you for clearing that up for me about the direction of the subs firing. I think I will go along with you guys and just start out with a 15.
Andrew, your home theater is right on! Now I want one!
If yall get around to it:
If a sub says 800 watts RMS do I need at least an 800 watt amp? I ran my last sub at max volume, would a bigger amp allow me to run it at less when connected to the low out?
Does a 4 ohm sub have to have a 4 ohm amp?
Can I wire both sides of an amp to one sub?
Why did my front speakers sound like crap when I hooked up my sub @ high level? ( the sub itself sounded much better than when hooked low)
How can I connect more than one sub to my receiver with only one low out?( for later)
Sorry about all the questions fellers, (and I know that for you guys they are simple) but my little xmas holiday is almost over, time to go back to work!
Most appreciative,
OD

[Paul H]

Jason,

Thanks for the compliment. I'm not sure about the talent part - being crazy/silly enough to try it is an important factor.

Some answers to your questions:

The amp does not need to be as large as the rating - ratings for subwoofers generally indicate maximum thermal load (ie wattage that will fry your speaker). The amplifier can be substantially lesss than that - I have a bryston with 120 watts per side that will push my tempest Very loud.

A four ohm speaker of any sort will require an amp capable of driving 4 ohm loads. Most separate amps and sub amps can do this - but always check.

You can wire both sides of an amp to a sub if the sub has dual voice coils. That's what I have done to my sub.

Not sure about your front speakers or current sub ..

Paul

[Andrew Pratt]

If a sub says 800 watts RMS do I need at least an 800 watt amp? I ran my last sub at max volume, would a bigger amp allow me to run it at less when connected to the low out?

No not at all you won't need nearly that much power for the most part...though a lot depends on the design of the subwoofer. A smalled sealed sub will typically require much more power then a large ported sub.

Does a 4 ohm sub have to have a 4 ohm amp?

Yes. Ohms is a measure of resistance. The lower the number the less resistance which means the amp will try to puch more power into it...which leads to more heat and more power output. Most plate amps will be fine at 4 ohm loads as that's a common rating on drivers...a 2 ohm load on the other hand might be too much unless you add a lot of external cooling to keep the amp from over heating.

Can I wire both sides of an amp to one sub?

Sometimes. Many subwoofer drivers have two voice coils in which case yes you just connect the left and right outputs to the two inputs on the speaker. You need to make sure the signal is mono though. Also some amps allow you to run it in a "bridged" mode meaning that both channels are added together inside the amp so you have two inputs but only one output. Not all amps support bridging though so you'd want to check that before buying one if that's something you require. If you go with a plate amp for the sub they're all mono so its not an issue.

Why did my front speakers sound like crap when I hooked up my sub @ high level? ( the sub itself sounded much better than when hooked low)

Most crossovers that are built into plate amps are very low quality. You are almost always best off using the crossover in your receiver.

How can I connect more than one sub to my receiver with only one low out?( for later)

Buy a "Y" splitter from somewhere like RadioShack

Sorry about all the questions fellers, (and I know that for you guys they are simple) but my little xmas holiday is almost over, time to go back to work!

I'd much rather you asked a question then not...its what we're here for right!