A kind hand needed

[Skoda]

Hello to all those on this great forum

I was wondering if some of you would be kind enough to help me out with box perameteurs for a subwoofer. I'am really not sure were'd I'd start...sealed,ported(bassreflex),bandpass, though most of the designs here are ported so they must be onto something unfortunitly there is a catch... its not a JBL sub...(gifts are great ) I know theres other forums out there for this stuff but I've been reading in alot on this forum and the know how of this forum as a hole, and personaly theres none other that comes close

Of course these sub's(2) built in seaperate box's will be for Home theare use, covering the low end of my HT4V's that will soon be were they belong...My Home The room they well be located it is quite large 13x25x12ft


Free Air Resonace.......................................... .....Fs 30.2Hz
Volume Acoustic Suspension.................................Vas 1.15Ft^3
Total Q................................................. ............Qts .50
Electrical Q................................................. .......Qes .55
Mechanical Q................................................. ....Qms 4.97
Dc resistance........................................ .............Re 1.84ohms
Linear Excursion (one way)...................................Xmax .49"
Effective Piston Diameter......................................D 8.634
RMS power handling.......................................... ...RMS 400watts
Recomended amplifier P........................................RMS 75-400
Sensitivity 1W/m................................................. SPLo 84.3
Reference Efficiency........................................ ....No 0.16%
Frequency Responce.......................................... .28-150Hz
Voice Coil Inductance........................................ ..Le 1.0mH
Gap Hieght............................................ ..............393"
Voice Coil Diameter.......................................... ....2.5"
Voice Coil Height............................................ .....1.246"
Magnet Weight............................................ .......102oz
Motor Force............................................. ..........BL 10.41 Tm
Compliance........................................ ................Cms .163 mm/N
Total Moving Mass.............................................. Mms 170.8g
Moving Mass of Driver..........................................Mm d 166.5g
Suspension Losses............................................ ..Rms 6.51
Effective Surface Area.........................................Sd 58.5 in^2
speaker diplacement(inside box).............................195in^2
speaker dissplacement(outside box)........................134in^2

Not sure if you guys will need all these spec's but better to have then not

Best Regards
Skoda

[Zilch]

Hiya, Skoda.

The best route to your answer is to download a freeware box design program from the internet, such as WinISD.

You can enter the parameters for your woofer if it's not already on the list that comes with, and try out various alignments for hours and hours.

Tell us what car sub that is. It may already be in one of our programs.

[Hint: EBP=55. Single-tuned bandpass looks maybe workable, though I, myself, have a particular affinity for triple-chamber in HT.... ]

[Skoda]

Hello Zilch

thanks for your responce was thinking there was no hope for these over sized magnet air pushing monsters..

The subs are mtx 8000 10". I've sent emails to mtx for product datasheets but nothing...The only reasons I have the specs I do is to a friend who was in the market for subs some time ago and wrote down specifications to the subs he was thinking of purchasing.

Zilch I'am curious as to learn more about this 3 chamber box, from what I read on this forum you have been around the block a couple times

What would be the ideal frequency responce curve for a subwoofer that is used for HT?

[Zilch]

MTX 8000 is not in the BB6P database, but it accepted your parameters as "good."

Look to HT products for FR targets. JBL's 4645C is also a high-end Synthesis HT product, for example:

http://www.jblpro.com/pages/pub/cinema/4645c.pdf

Here's the TCB:

http://audioheritage.org/vbulletin/s...ead.php?t=6782

There's links there to tell you what's going on with that design approach, which can be modeled in BB6P.

[Titanium Dome]

(snip) from what I read on this forum you have been around the block a couple times

There are few here that give as much to other members as Zilch, and his enthusiasm is endless.

As for his having been around the block... well, no, he is the block.

[Skoda]

He owns the hole block eh...Party at Zilchs place! well maybe you meant he can provide sound for the hole block either way it's gonna sound great and be a good time

On to the subwoofer box perametuers... I was looking at responce curves from a number of subs from JBL and saw most had there f3 point before the 30hz. so should I be trying to do the same?

Let me know what looks good to you guys, or reccomended tweeking?

Heres what I came up with last night, and yes you can spend hours on this stuff

[Zilch]

http://audioheritage.org/vbulletin/s...2842#post82842

Room rise and boundary effect are gonna make any of those alignments boom artificially.

With subs, you've got to pay particular attention to cone excursion limits, and even then, plan on using a highpass filter at the appropriate frequency to protect them.

In some alignments, the cone excursion is rising exponentially at the bottom end....

[Skoda]

Alright now i think I got it I plan to have a Linkwitz Riley Crossover at 20hz

Though the program doesnt show cone excursion (hope I'am wrong) is it called something else?

Well here it is...

[Zilch]

What's your vent size?

You're O.K. on cone excursion.

Check the group delay. It's off the chart below 20 Hz here, but that may not be an issue.

May be tomorrow before I can help you optimize.

Looks close....

[Skoda]

I'am posting the info you reqeusted I check for but...Ia'm not sure what to look for(its my first time using a program like this or designing a box for that matter )

In case you can't see it(looks rather blured) the port size is 3 inchs wide and 40.6inchs long

I'am geussing that big spike before 25hz is a bad thing:dont-know