Rookie subwoofer project- Avalanche 18

Hi,

I have an Avalanche 18, and the Adire 1,200 watt plate amplifier. I have looked at Ascendant's recommendations for enclosure volumes for both designs, and well, the ported requires a huge box . The application is HT of course, so what is the prudent design approach? Sealed gives "tighter" bass, right? and ported is deeper. I like the idea of low bass for movies, but 13 cubic feet is a bit of an aesthetics stretch... To protect the driver, I thought perhaps around 7.5 cubic feet sealed box would be ok..


Thanks very much for any advice...
 
You have the ADA1200... right? That amplifier has a Linkwitz Transform built in, and with the displacement of the Avalanch 18 (no need to port to get SPL... the raw driver can deliver plenty of displacement) I would take advantage of that LT and build a smallish sealed enclosure. You may need to contact Adire about the proper implementation of the LT circuit (I believe you have to make a few connections or perhaps fill in a couple of resistors yourself).

I'm sure we can help you model up a decently sized enclosure and the proper LT values to use for your desired response, but as a start... what would your desired response be? :) As in, what Q would you like to aim for, and what anechoic F3, or would you prefer to match the expected room gain for a particular room?
 
7.5 cu.ft sealed will be nice, you can use some stuffing too.

Your driver will be protected down to 26 Hz with 1200W imput.

With a driver like this, the bass will be quite deep anyway hehe!

EDIT: Follow what this guy said, if you really have a LT circuit, use it because you'll have deeper bass, like a ported enclosure.
 
Sealed/Ported help for Avalanche 18

Thank you all VERY MUCH for the responses. I know I am just another novice, so I really do appreciate the help. The amp is the ADA1200, yes. My ability with electronics is virtually zero, so changing a few components in the amp could be tricky for me.

If one of you could do a little modeling for me (ported especially- that would be wonderful. Is there one "correct" displacment for a sealed design, or do you simply gain lower end response the bigger you go?? :xeye:

Thanks again,

Bruce
 
Just a quick note, you can go as small as 4.6 ft^3 if you like, Chad (the Ascendant guy) uses a pair of 18's in enclosures that small (or big...to look at at the other way) for his home theater. I'm following his lead this time round, after I built a 12 cubic foot ported box tuned to roughly 16 Hz. Sounded pretty amazing for rap, but 1. i can only listen to that crap for so long, and 2. I didn't like the way the driver seemed uncontrolled through some fast rock beats. That and i like tighter bass...
Putting it in a smaller box will also help increase power handling, which may (or may not) come into play since you have 1200 watts at your disposal and the sub is 'rated' at 800. I'm sure you won't have a problem, but go easy on it the first few times you use it. Last note, and Chad mentioned this to me after I blew my first 18...These subs play really loud, but may not sound all that loud because they are so distortion free (supposedly) so again, be careful for both the sub and any breakables :devilr:
 
I think it would be wise for you to begin with your goals and specifics about your room and work for there.

If you shoot for flat anechoic and have a small room, the response in room could be quite elevated as the frequency drops. Some like that, many don't.

How large is your room? Are you a basshead, or do you just want tight, accurate, and musical bass? What kind of music or movies do you most enjoy?

Those types of questions will help determine the best alignment for you.
 
Re: Sealed/Ported help for Avalanche 18

HTRookie said:
The amp is the ADA1200, yes. My ability with electronics is virtually zero, so changing a few components in the amp could be tricky for me.

If one of you could do a little modeling for me (ported especially- that would be wonderful. Is there one "correct" displacment for a sealed design, or do you simply gain lower end response the bigger you go?

Do you know someone who could replace the components for you?

Ported with one Avalanche 18 in a 7.5 cu.ft box is not worth it IMHO. Unless you buy another one to go isobaric hehe!

By going bigger with a sealed box, you just gain lower end response. There's no correct displacement.
 
Avalanche 18 project cont'd

RHosch and all of you kind enough to help me :>)

My room is 14'4" wide x 18'9" long, std. 8' ceiling. This is my first subwoofer ever, and my first home theatre experience as well. If I had to summarize my goal here, it would be to have a sub that produces tight clean bass, low enough to enjoy the low frequency effects in many movies-but not do the "boom boom" thing I hear in the kids cars driving to work..:(. Some months ago I also bought a Peerless XLS and 2 12" PR's. I was told that that sub would be better for music, although it is not clear if I will have room for a second sub until the HT project is further along.. I was not sure myself about the amplifier; I did not want to under power the Avalanche 18, but since I am 50 and do NOT listen at ear bleed volume levels any more (Led Zeppelin induced permament hearing loss from being a dumbass as a kid) I thought I would never drive the sub close to the level where damage would even be possible..

As I understand it, ported designs extend the low frequency response of the driver, but the driver is "unloaded" below Fs, and the cone movement can be excessive -yes??

My woodworking skills are good, so I can build a good box, I just can't, at this point, design a speaker to save my life :bawling:

Bruce..
 
Look at the page 11 of this manual.
You need to find someone to do this for you.

http://www.acoustic-visions.com/~acoustic/products/subwoofer_amplifiers/adire_ada/ADAManual.pdf

This is a Linkwitz Transform circuit, you'll be able to have deep bass without a huge box. The sound will be a bit better too! You'll lose some SPL, but you don't seem to need insane SPL hehe!

The problem with a ported Avalanche 18 is that you need a very very big box to have a nice frequency response curve.

It's true that ported enclosures unload the driver below the tuning frequency of the box (Fc), not the Fs of the driver. If you tune the box low, this is not a big problem. The Avalanche 18 have alot of excursion, so it's also hard to unload it.