Head Start On The Maelstrom (1 Viewer)

[Scott Simonian]

Hey all you cool DIYers.

Most of you know about Adires new driver on preorder, the Maelstrom. A kickass 18" behemoth! I know a lot of you allready got the new LspCAD so you can tinker with it. I myself have started doing the same tonight.
Now, some of you who know of me here, Im new to the DIY arena and would like to become one of the elite too. I have never made a speaker of ANY kind but plan to do so in the near future.
Right now in my life, I am often not pleased with my low frequency production at home. I own a Def Tech pf15tl. It is a great sub and I have been loving it since I bought it in the 8th grade almost 3 years ago. Its time for me to move on now and I want, nay I MUST get something that WILL blow me away for good. (well, for a few more years )
The BIG problem is, that I am very very broke. *sigh*
I would like to sell my sub for a good chunk of what it is worth. It is in perfect condition, just used really. Now, Im not asking someone to buy this off me, no. This is not a trading post here.
(almost done, bare with me)
I dont know HOW, really, to sell it(or who to). There is absolutly no way to sell it to a friend or family. Tried that. Everyones got one.

I cant really sell it on eBay or something like that because my dad doesnt trust it and honestly, I am not sure about it either. Another problem is the selling price. It IS in perfect condition, just used. I really think it is worth no less than $500. (I bought it for $700) But when I say something over that, I feel guilty becuase it is not the best anymore and may not nessesaryly be worth it.
Ok ok. Get to it BOY!!!
This whole post is about making a new DIY maelstrom. But since Im broke, and am sure by what ALL this DIY commosion ive been hearing since I got hear, I would like to sell my current sub and use the money toward this new DIY.
Im looking for a somewhat small cabinet, sealed or ported. I want GREAT articulation but GREAT midbass slam for the movies. (yeah, not possible) When I was playing with LspCAD, I got (in a sealed cabinet) less than 10ms group-delay @20hz. (!) That sounds what Im looking for.

But, like I read, Jack Gilvey had the same problem I had saw, excursion problems. Yeesh. Unfortunatly

(of course), I dont really know how to use the program. (yeah, dumb kid)
It would be cool if someone could design one for me. Something not too big. I plan on using the AVA250, runing 4ohm parallel. So its a nice 250w.
I guess a good way to summerize this whole dillema is if someone knows a great, reliable place, that is garunteed (woops) to buy my sub for a good ~$500. I would like the $$$ quick so I could pick up the maelstrom discount form Adire.

ANd then, If someone could be a gent and design me a sub like what I have summed up. Or just point me in the direction where I could get allready made up schematics.

GIMME GIMME GIMME !!!!!!
[Edited last by Scott Simonian on August 12, 2001 at 02:58 AM]

 

[Jack Gilvey]

Hi Scott,
I'm still playing around with it myself, but I wanted to note that the excursion issues I ran into were when using a Linkwitz transform spreadsheet, and I certainly wouldn't take or present those results as definitive, given the strong possibilty for input error.

David from Adire mentioned on a Bass-list post about the suitability of the driver for the LT, and the possibilty of presenting some circuit designs for it, so I'll await those.
Putting the driver in a 3-4 ft^3 sealed box driven by an AVA250 led to no such problems. Remember, LspCAD is reporting the peak-to-peak excursion which, for Maelstrom, is 26mm.

 

[Scott Simonian]

So its like that eh?
Leave me to the wolves. *sigh*

 

[Jack Gilvey]

When the wolves show up, they'll probably ask you what you mean by "somewhat small", so they'll have something to work with. Wolves feel that "vented box" and "small" don't really go together, whatever the definition.
They might also point you toward http://www.hometheatertalk.com/ubb/Forum7/HTML/000869.html
[Edited last by Jack Gilvey on August 14, 2001 at 09:52 PM]

 

[Scott Simonian]

Ok ok Im sorry.
When I said somewhat small, I just meant I cant have a "water-heater" and I dont want to make it a sonotube-based sub. I want to make it MDF based so I can have my friends dad build it and it wont be too hard. Im afraid that building the endcap would be a burden on him.
I have decided that I dont want it to be vented or ported. (some say differnt

) I definetly want it sealed. For sound quality and design simplicities sake.
A nice box would be not too much more than 25"/3.
What else you think you need?

 

[Jack Gilvey]

Just bustin' chops, Scott.
Well, for a sealed, Adire mentions good performance on the Maelstrom page from a 22" cube. Made from 1" stock, this would net about 5 ft.^3. A quick run with LspCAD indicates very good in-room SPL from an AVA250, and an in-room f3 below 20Hz. The Qtc of 0.6 should sound very good indeed.
I'm exceeding Xmax with this box/amp @ 20Hz/107db, though. Since Adire indicates that 20Hz at 115db is attainable, I think I must be doing something wrong.

 

[Scott Simonian]

Thats cool man.
Hmmmm....all that sounds good to me. But the Qtc sounds a bit iffy. Should I expect it not to sound better than my Def Tech that I had mentioned.
Ever since I was at the home theater expo in Oct 99, where I got to hear the Genesis 200, Ive been adicted to tight articulate bass. Im not sure what kind of difference to expect between a Qtc of .5 to .6.
Do you know?
I think it is time for me to know how to use LspCAD. Do you know where I could go (on the internet anyway) for reference on how to use LspCAD? I could use some tutorials.

 

[Patrick Sun]

You could start with the help file... Just play with it, pick a driver, pick an enclosure size (sealed or the various vented options), porting options, and you'll start to see the relationship between the variables.
The main caveat is for the input power, it's for each coil, so if you are pushing 400W into a 4 ohm (parallelled dual voice coil hookup), then put 200W for the input power when simulating max power input for the excursion graphs, air speed, etc.
------------------
PatCave ; HT Pix ; Gear ; DIY Mains ; DIY CC ; Sunosub I + II + III ; DVDs ; Link Removed
[Edited last by Patrick Sun on August 15, 2001 at 05:34 AM]

 

[Jack Gilvey]

Hmmmm....all that sounds good to me. But the Qtc sounds a bit iffy. Should I expect it not to sound better than my Def Tech that I had mentioned.

Iffy? Why? What does it have to do with the Def Tech (are you aware of its Qtc)? There is a difference between .5 and .6, but either is extremely tight (and will embarrass the DefTech, in quality and output). You could always do a bigger box. Of course, there's the Linkwitz transform circuit, which allows you to get just about any f3 and Qtc you'd like from just about any size box at the expense of power.
http://sound.westhost.com/linkwitz-transform.htm
The readme file with LspCAD is huge and explains all. Like Pat says, though, you just gotta play with it.

 

[Scott Simonian]

So does anyone know about where I could sell my current sub (Def Tech PF15TL) easily and for a good amount of $$$?
I just need money so I could get started.

 

[JohnA]

Scott
Look for a friend or relative or friend of a friend to sell the PFTL to.
Don't expect too much money. Used consumer electronics do not have high resale.
I recently decided to build a ported Tempest but, have now switched gears and will be building a sealed Maelstrom.
Having completed the design, and parts list, the Maelstrom will cost me less than the Tempest. One sheet less of plywood, no ports, no legs etc.
You can get started right now by getting on the pre-order list for the Maelstrom and buying a sheet of Void free plywood, some screws and adhesive. This will get your box built (excluding tools) for $75.
As for my Definitive Technology Powerfield PF1500, It will be used in the front of the room to enhance the main channels. It is worth far more to me than it is to someone else.
The Maelstrom will be exclusively used for LFE.
-JohnA

 

[Dustin B]

If there is a University near by. Find out about their policies on posting fliers. The one I attend you have to go to the help desk and get it stamped (which will allow it to be up for a couple weeks). Then place a few in high traffic areas of the campus and see what happens. I've gotten a lot more than I should of for a bunch of stuff this way (70-85% of what I payed for it).

 

[Scott Simonian]

Hmmm...