RMS Question - Page 3

Bigshot44 · 12-09-2010, 10:47 PM

Quote:

Originally Posted by Afugy

Nothing wrong with a box thats tuned to 55hz, as long as its tuned with a flat response. Really I don't like to knock a box until its properly metered, by smaart or even term.

Are you building a box so you can do comps or you just want to be loud?

The size of the box has nothing to do with it bottoming out.

Haven't you heard my car? Tuned to 40hz, sounds great to untrained ear but missing out on 60hz to 125hz sucks. Thinking that a 6.5" or a 6x9" will produce that range efficiently without allot of work is madding.

Just think how shity this song would be with out 60 to 125hz http://www.youtube.com/watch?v=auDv6cf2PBM.

And I hope Ryan corrects me on this but for some reason building a box that fires into a trunk should be NO bigger then half the air space in the trunk, because having your subs firing into the trunk turns the trunk into a 6th order bandpass.

Just want to be SPL

Bigshot44 · 12-09-2010, 10:55 PM

Quote:

Originally Posted by Afugy

Why? I'd really like to hear why a box tuned to 55hz should not play music!

Just forget about ALL of those misleading box diagrams. Just tell us what sub it is and the specs or do your own math http://www.carstereo.com/help/Articles.cfm and tell us what you come up with.

So im trying to calculate but im not sure how to find a few things so ill just post specs

Diameter: 15"
Sensitivity (2.83V @ 1M): 92dB
Power Handling: 800w rms, 5000w pk
Frequency Response: 20Hz - 1kHz
Nominal Impedance: 6 Ohms (Per coil(2))
Voice-Coil Diameter: 3.0"
Basket Displacement: 0.130 FT3

REVC (Ohms)*...2.95
LEVC (MH)*......1.06
SD (FT2)........0.839
SD (M2)..........0.078
BL (TM)*.........15.39
VAS (FT3).......4.67
CMS (um/N).....153.02
MMS (g).........260.67
MMD (g).........248.15
FS (Hz)..........25.20
QMS..............7.20
QES..............0.51
QTS..............0.48
HAG (IN).........1.00
HAG (mm).......25.40
HVC (IN).........2.60
HVC (mm)........66.04
XMAX (IN).......0.80
XMAX (mm).....20.32

*Voice Coils connected in Parallel

Afugy · 12-09-2010, 10:58 PM

Quote:

Originally Posted by Bigshot44

Just want to be SPL

Okay but do you just want SQ spl or competition spl, just saying SPL doesn't help, SPL = sound pressure level and is not specific to anything that makes sound.

AND
Who makes the sub?

Bigshot44 · 12-09-2010, 11:35 PM

Quote:

Originally Posted by Afugy

Okay but do you just want SQ spl or competition spl, just saying SPL doesn't help, SPL = sound pressure level and is not specific to anything that makes sound.

AND
Who makes the sub?

well i want it to be loud with sound quality, im not going to be entering any competitions, so i just want it to be loud for listening to music.

its JBL and part of the GTi series

JBL W15GTi MKII

Afugy · 12-10-2010, 12:09 AM

Aaaaaaaa very good, NOW we can build a box.

Just one sub, right?

http://www.carstereo.com/help/Articles.cfm?id=17

http://www.carstereo.com/help/Articles.cfm?id=31

Bigshot44 · 12-10-2010, 12:36 AM

Quote:

Originally Posted by Afugy

Aaaaaaaa very good, NOW we can build a box.

Just one sub, right?

http://www.carstereo.com/help/Articles.cfm?id=17

http://www.carstereo.com/help/Articles.cfm?id=31

yes it is.

Cashdollar2009 · 12-10-2010, 05:16 AM

Quote:

Originally Posted by Afugy

The size of the box has nothing to do with it bottoming out.

I just see potential loading issues with a 6.5ft^3 box with this subwoofer and the music he wants to listen to. Playing 20Hz below tuning frequency is a no-no.

He said he listened to hip-hop, rap, and C&S. He would be VERY disappointed tuning to 55Hz and trying to play some Jeezy or something.

I just put some numbers into my box calculator and got you a quick box design.

Height: 16"
Width: 33"
Depth: 20"

Port Height: 14.5"
Port Width: 3"
Port Depth: 19"

This gives you a net volume of 3.88ft^3, which will be great for this driver off of the 1000wrms you plan to give it. Being close to 4ft^3 for this single 15" driver it will be rather efficient and would be able to handle more power down the road without any issues if you so wished to.

A port tuning of 34.11Hz and 11.21in^2 of port area per ft^3. This will sound great for that rap, hip-hop, and c&s music you listen to. Think Young Jeezy, Gorilla Zoe, Lil Wayne, Slim Thug, T.I., Ludacris. Those artists are notorious for having some "heavy-hitters." A 30-35Hz tuning is what you would be looking for here.

Cashdollar2009 · 12-10-2010, 05:18 AM

Quote:

Originally Posted by Bigshot44

I have an above average understanding of car audio, but ive never had a dual vc sub. its a dual 6 ohm that can be wired in parallel to 3 ohms or series to 12. im going to wire to 3 ohms and my question is does the rms change at all depending on how you wire it?

its a JBL W15GTi MKII
800rms, 5000w peak.

Quote:

Originally Posted by Afugy

Okay but do you just want SQ spl or competition spl, just saying SPL doesn't help, SPL = sound pressure level and is not specific to anything that makes sound.

AND
Who makes the sub?

Reading > Joo

Ryan from Ohio · 12-10-2010, 02:02 PM

Quote:

Originally Posted by Afugy

What took you so long?

Im semi retired. Tired of the BS. However some things never change... Facts are still the facts.

Quote:

Originally Posted by Afugy

Nothing wrong with a box thats tuned to 55hz, as long as its tuned with a flat response. Really I don't like to knock a box until its properly metered, by smaart or even term.

Are you building a box so you can do comps or you just want to be loud?

The size of the box has nothing to do with it bottoming out.

Haven't you heard my car? Tuned to 40hz, sounds great to untrained ear but missing out on 60hz to 125hz sucks. Thinking that a 6.5" or a 6x9" will produce that range efficiently without allot of work is madding.

Just think how shity this song would be with out 60 to 125hz http://www.youtube.com/watch?v=auDv6cf2PBM.

And I hope Ryan corrects me on this but for some reason building a box that fires into a trunk should be NO bigger then half the air space in the trunk, because having your subs firing into the trunk turns the trunk into a 6th order bandpass.

Everything is wrong with a box tuned to 55Hz. You forget about the F3 roll off... With a high tuning like 55 Hz I would estimate and F3 of like 48 Hz... Thats a horrible tune for rap music... Might be ok for rock music... Will give you more mid bass... Less of a subwoofer and more of a woofer function.

Dont over complicate systems. Sure its like a bandpass. A car itself is a "box" and doing various things will always have some effect.

Ryan from Ohio · 12-10-2010, 02:04 PM

I would say 3.75 cubes tuned to 36 Hz, F3 (subsonic filter setting) of 26 Hz.

Bigshot44 · 12-10-2010, 10:38 PM

Quote:

Originally Posted by Cashdollar2009

Height: 16"
Width: 33"
Depth: 20"

Port Height: 14.5"
Port Width: 3"
Port Depth: 19"

Are these inner or outer dimensions. also 3/4 MDF?
And thanks for helping.

Ryan from Ohio · 12-11-2010, 01:24 PM

3.75 cubes

Port 2.5" x 15" x 11 7/8" lg.

34 Hz Tuning
28 Hz F3 (set subsonic to 28 Hz)

4.5 dB gain @ 46 Hz

Going larger on the box will help- upto 6 ft cubed max. Nothing jaw dropping.

See attached for graph.

Cashdollar2009 · 12-11-2010, 01:37 PM

Quote:

Originally Posted by Bigshot44

Are these inner or outer dimensions. also 3/4 MDF?
And thanks for helping.

Outer and yes. No problem man.

Bigshot44 · 12-23-2010, 01:31 AM

What do you think of my paint sketch? (3/4 mdf)

Ryan from Ohio · 12-24-2010, 10:51 AM

Not bad for paint.

Design wont work.

If you have a 3" port then you need your port1 wall to be 3" off the back wall.

I have had best luck with the port on the same plane as the sub.

Cashdollar2009 · 12-25-2010, 02:49 AM

It looks as if you are trying to use the dimensions I gave you. If so, there are a few minor things you would have to change. As Ryan mentioned, he has had better experience with the subwoofer on the same plane as the port. In my suggestions before I had mentioned a height of 16". With this height, that leaves you with enough room of the 14" cutout and 15" sub on the face, where I have it relocated.

As for the port depth issue. As the port runs back into the box, the port area must ALWAYS remain the same. In order to do so, you must keep the port width equal at all times. In your case, you want to leave a 3" width/gap. Therefore, your port will need to bend. (see diagram.)

I did my best in a quick paint fix-up trying to show a few things graphically. lol

Bigshot44 · 12-29-2010, 12:38 AM

would this be right then?

Ryan from Ohio · 12-29-2010, 07:38 AM

When you bend ports the port length is measured from the center of the port, not a port wall side.

So it would start in the center of the port at the front of the box. Not 3/4" in...

Im gonna guess neither of you realized this.

Sure you can build it as shown, but the tuning would be off. Depends on how accurate you want to get...

Bigshot44 · 12-29-2010, 08:56 PM

Quote:

Originally Posted by Ryan from Ohio

When you bend ports the port length is measured from the center of the port, not a port wall side.

So it would start in the center of the port at the front of the box. Not 3/4" in...

Im gonna guess neither of you realized this.

Sure you can build it as shown, but the tuning would be off. Depends on how accurate you want to get...

I'm not concerned about exact tuning, just enough to sound good for hip hop/rap

Ryan from Ohio · 12-29-2010, 11:28 PM

To get down right technical, as drawn.

4.02 cubes

23.5" port length.

That gives you a tuning of 31.7 Hz

F3 of 27.4 Hz

3.8 dB gain @ 44 Hz

That includes removing the basket displacement. So this is the true figures at the end of the day.

I would shorten the port up a bit to get closer to 20" and to get that simply remove that extra piece in the rear (the 3.5" piece).

That will move the tuning up to....

4.14 cubes

20" lg port

33.3 Hz tuning

28 Hz F3

4.5 dB gain @ 44 hz

Up to you, I would opt for the extra gain and less work, lol.

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