View Full Version : Jmac, if you will...again....

01-19-2003, 09:23 PM
Jmac, you've given me dimensions on this before, but I lost the printout so I need you help again... was hoping that you could help me out here...

I was about to purchase some HX2's with RF amps, but due to circumstances, I can't afford any parts except sheets of MDF...so please, help me out here, k? :D

I previously had a sealed box, 1.509Cu.Ft. for two RFP1810 and now want to have a slot port box...

I have an underpowered amp pushing the two 8 ohm 10"subs, so I'd need something that don't need a bucketload of power ot push the cones... oh, and I'm more for SQ than SPL...

Erm, the shape might, again, look funny (i.e., not rectangular) so I'm just gonna have to tell you the biggest size I can manage after 2 sub displacements as well as the ports... about 1.8~2.0Cu.Ft... the specs for the subs are as follows:


Nominal Diameter 10" (254mm)
Magnet Weight 30oz (850.5g)
Frequency Range 25-500Hz
Nom Imppedance 8ohms
DC resistance(RE) 7.2ohms
fs 26Hz
Qms 4.7
Qes 0.29
Qts 0.27
Sd 54.26"Sq. (0.035sq.M)
Vas 2.72Cu.Ft (77L)
Cms 4.97E-04
Mms 3.1394oz (89g)
VC Dia 2" (50.6mm)
VC Winding height 1" (25.4mm)
VC Former Material 5 mil aluminium
VC Inductance 4mH
Bl 18.2Tm
Xmax 0.31" (8mm)
Sensitivity (SPL) 88dB

rec box vol 0.75Cu.Ft
Speaker Displacement 0.06Cu.Ft

powered by
Amp: RF 60.2

Dynamic power rating @4ohm mono 14.4v 270watts (Dynamic meaning PMPO?)
RMS @4ohm mono 13.8v 120watts

yes, I've heard from at least 1394861526587 people that my amps are underpowered...I also get drastically underpaid...

Jmac, please help me out..I'm in a terrible mood these days (from the disappoint of not being able to get the pair of HX2's...):( i wanna make a box to comfort myself...:p

01-20-2003, 12:46 AM
jmac, don't tell me you've fallen asleep already...:(

01-20-2003, 01:47 AM
Originally posted by Jmac
Oh ****, sorry buddy ... didn't see this ...

What dimensions are we working with here ?

Phew~ hope i didn't wake ya...but I'm glad you're not sleeping...kkk

anyway, the shape of the box is gonna look somewhat funny, you know, trapeziod kinda thing... and the box will be shaped according to slot port length you'll recommend...so the whole chamber will be 1.8~2 Cu.Ft after sub and port displacement... I know you don't have a lot to work with here, and you'll recommend a bigger box, but I want to be able to take out my spare....:D

thanks so much, my friend:) :) :)

01-20-2003, 02:14 AM
Thanks so much, Jmac, I know I can count on ya...

oh, and what's the acceptable amount of vent velocity? You told me before, but I forgot..

I can only get up to about 45 in winISD pro...

01-20-2003, 02:17 AM
Originally posted by Jmac
You're supposed to keep it below 30 m/s ...

I get 29.368 m/s @ 400 watts with 16 square inches of port area, 2 ft^3 internal space, and a 37.1 Hz tuning frequency ;)

Well, the largest height possible for the slot would be 26.9cm and it wouldn't look good at all if I made the port any bigger than 8cm..or 10 max...

01-20-2003, 02:24 AM
Originally posted by Jmac
26.9/2.54 = 10.6"

16/10.6 = 1.5"

1.5*2.54 = 3.8 cm :)

So make the port 26.9 cm x 3.8 cm :D

erm, but at 1.5", the velocity will be at 60m/s...:(

01-20-2003, 02:40 AM
Originally posted by Jmac
Are you sure you have it on m/s ?

I'm getting 29.552 with 10.6" x 1.5" ...

Maybe you have it 10.6 cm x 1.5 cm ?

How much power are you putting into WinISD ?

Whoops, I'm so sorry, Jmac..I had it on Ft/s...:( my bad, mine all along...darn...

yeah, now it's showing me something good...

oh, and i put 200 on power, i thought that my amp can't really reach over 250watts, never mind 300...you think my small, ol' RF CAN manage an honest 250 at peak?

01-20-2003, 02:50 AM
Originally posted by Jmac
It has a 270 watt dynamic power rating, so I'm guessing that's pretty close to what it actually puts out ;)

If you want, you can drop it down to 10.6" x 1.25" ;) You'd under 31 m/s peak with 300 watts with that size with a 10" long port.

After that, all you would have to do would be to find a way to get 2 ft^3, which is the hard way to do things ;)

It's much easier to pick the dimensions and adjust them to get the outcome rather than to get the outcome and then try to figure out the dimensions ;)

Well, it'd be really easy tomake a box, jsut like everyone else, but I would like to make it special...

i know my box isn't anything you'd call fancy, but to me, it looks so much better than a rectangular box, especially that tunnel I made (no one willsee it, but I know it's there and I like it) and this time, I'm thinking of new creative ideas to make a box, so I needed the volume and see if my ideas work and hpefully, they'll match...

wouldn't be too bad if i exceeded volume by about 0.2~3 CU.Ft, would it? Wouldn't it sound better? Or am I in dreamland?:confused:

01-20-2003, 03:00 AM
Originally posted by Jmac
You can go smaller if you're concerned ... Remember that you have to compensate for port volume, speaker displacement, the MDF inside the box used to make the port, and anything else inside the box ;)

How about 1.5 ft^3 tuned to 38.5 Hz ?

nah, i think after displacement, I can still get 2cubes... man thanks so much man...always my box guru...

I'll probably finish off the design this week and order the pre-cut MDF next week...

hopefully I'll finish teaching myself autoCAD and get an exact drawing in here...;)

01-20-2003, 03:04 AM
Originally posted by Jmac
Just remember, you're going to need a subsonic filter set at 30 Hz ... ;)

Part Number 266-248 @ http://www.partsexpress.com/index.cfm

Oh ****... jsut realised that I don't have a subsonic filter in my amp....

er....er.... and I can't order from the states, the shipment costs a whole lot more than the parts itself....****, ****, dman!!!!!!

er, but just for the record though... what kind of subsonic filter do i have to get? a bass stopper? my amps low-pass cutoff is at 80Hz... how would i "set" to 30Hz with that inline xover module?

01-20-2003, 03:20 AM
Originally posted by Jmac
1.4 ft^3 tuned to 25 Hz ?

10" by 1" port ...

whoa, now THAT I know won't give me good low-end and my amps might not have enough power to push the subs to full potential, right? or am I wrong again, like i always am? :P