Need help building a box for subwoofer without Specifications

[The enD 467]

So I got this 30$ subwoofer which I bought 3 year ago and it still plays good and I like it. But the box what it has now I was told is too small and tuned very high(indeed it does not hit the lows very good).

I have no information about its xmas, vas, FS ... etc. It says 900W max (maybe 150w real ) 12 inch Thunder. Model BC1250RD

I want something to listen to my music till I get money for NSv2 ( rap and some bass tests... so low tuning around 34Hz).

Here are some pics.

My fail box. Yes I know I don't need polyfill for a ported box.

Port is 4.7 inches radius , long around 5-6 inches.

So help me forum. I was told by a pro I should go with 2 - 2.25 cub ft , 15 sq inch round port(around 4 inch radius), 12 inches long? A sketch-up will be very nice.

[SpeakerBoy 64]

Shiny! Do you know what company makes it?

[///M5 2,833]

Guessing won't help. You need to tell us what acoustically is wrong with the current box.

*that isn't stuffing, that is lining and IS appropriate for a ported box

[The enD 467]

Shiny! Do you know what company makes it?

You can see in my post - Thunder.

Guessing won't help. You need to tell us what acoustically is wrong with the current box.

*that isn't stuffing, that is lining and IS appropriate for a ported box

It does not hit the lows very good. It sound loud at high freqs like in the song - bia bia ( Lil Jon ) and in my car By The pack.... very high tuning with this port. I wast told if I want to tune this box lower, the port have to be reaaaaaaly long.

Edited January 22, 2010 by The enD

[The enD 467]

No replies ?

Come on guy.

[jcarter1885 995]

Shiny! Do you know what company makes it?

It tells you on the sub and he stated it in the post, reading is fundamental.

OP I couldnt find any information on this sub except for the thread you made in a forum from your country, you dont have any more information than that I would say try a standard box sized for a 12'' and tune lower than where you are at.

[///M5 2,833]

To start out with I'd just extend the port externally and see if it helps. If you get the port up so the tuning is lower (35Hz) range and it still won't play low you know you'll have to increase the box size. This will reduce the power handling though (inc box size) so beware.

[The enD 467]

Shiny! Do you know what company makes it?

It tells you on the sub and he stated it in the post, reading is fundamental.

OP I couldnt find any information on this sub except for the thread you made in a forum from your country, you dont have any more information than that I would say try a standard box sized for a 12'' and tune lower than where you are at.

The first thing looking at the sub is, its shiny and red, screaming "buy me". But it actually handles a lot of abuse and still plays very good.

I couldn't find any info too. Don't think I haven't tried. How big is a standard box for a 12" ?

To start out with I'd just extend the port externally and see if it helps. If you get the port up so the tuning is lower (35Hz) range and it still won't play low you know you'll have to increase the box size. This will reduce the power handling though (inc box size) so beware.

Ok I will try longer port. Should I remove the white thing inside (it is actually used for the clothes warming, my parents own a clothes shop) ? Doesn't it reduce air flow a lil bit ?

Edit : What do you mean "externally".... port Lenght or Diameter? And does externally mean port should stick outside the box ?

Edit 2 : And how long does the port have to be? It's 4.7 diameter.

Edit 3 : I made a mistake in the first post. The round port is 4.7 diameter. If someone can fix it, do it.

Edited January 22, 2010 by The enD

[jcarter1885 995]

Standard box size varies but anywhere from 1.25-2.5ft^3 give or take some ft^3, what size box is the one you currently have it in.

[The enD 467]

Standard box size varies but anywhere from 1.25-2.5ft^3 give or take some ft^3, what size box is the one you currently have it in.

I am not in town to measure the exact dimension, sorry. Around 1.8 cub ft maybe, don't know?

[The enD 467]

So ... box turns out to be 1.9 cub ft. Net volume. I've been playing around with it for some days and it sounds way better.

Found some sewage pipes and chimney pipe (the corner) and put them right back. It sounded better right away, but because the pipes were not connected very good to each other there was some port noise.

I removed all the batting that was inside and change the port length with lil too much but I was experimenting

Old tuning was horrible - 50Hz... I got a headache every time I listened for a lil longer period.

More testing... port still too long.

Well why not put a 1.2 meter port just to see what happens ... of course it sounded like shit

This is going to be my port. I need to cut it cause it is 4 inches longer than I calculated it has to be. Sound way better in the lows.

It's not in the box because the hole is too small. I'll make it bigger and paint the port black so it is not too catchy for the eye.

I'll appreciate some post but don't expect many to be impressed with my n00b shit

[altoncustomtech 773]

Actually I must commend you on ACTUALLY EXPERIMENTING. 9 out of 10 times people are asked to try something they simply whine and ask on another forum and get bogus information. It's good to see someone trying so hard to figure out for themselves how/why/what really helps or hurts. While the methods left a little to be desired it still did what it needed to do and you learned from it. I think that you deserve a pat on the back for that.

[ryan s 12]

Hey man, you did well not knowing anything about the sub's parameters! I'll give you a thumbs up for experimenting and finding what sounds good

[jcarter1885 995]

Hey man, you did well not knowing anything about the sub's parameters! I'll give you a thumbs up for experimenting and finding what sounds good

x2, and it shows you what car audio is all about testing to get where you want to be or it to sound how you want it to sound.

[The enD 467]

Actually I must commend you on ACTUALLY EXPERIMENTING. 9 out of 10 times people are asked to try something they simply whine and ask on another forum and get bogus information. It's good to see someone trying so hard to figure out for themselves how/why/what really helps or hurts. While the methods left a little to be desired it still did what it needed to do and you learned from it. I think that you deserve a pat on the back for that.

Thanks. I don't like to know something without actually knowing it. If someone tells me "your port has to be 4 inches in diameter, 12 inches long" the first question I as is why? "Why does it have to be 4? " - because of the subwoofer. It needs to "breath" depending on its Xmax. " Why does it have to be 12 inches long? " Because if it's longer or shorter, you are setting the tuning not what you desire at.

And this kind of things.

Hey man, you did well not knowing anything about the sub's parameters! I'll give you a thumbs up for experimenting and finding what sounds good

Thank you.

Hey man, you did well not knowing anything about the sub's parameters! I'll give you a thumbs up for experimenting and finding what sounds good

x2, and it shows you what car audio is all about testing to get where you want to be or it to sound how you want it to sound.

x3 on that. Not even the most experience guys on the forum can replace some real life testing. They just give me the basics and some things I (we) have to learn by myself.

Edited February 23, 2010 by The enD

[Impious 1,476]

I actually chuckled when I saw the pictures. I've seen a lot of things on the forums over the past 8 years....can't say I've ever seen anyone use chimney and sewer pipes as a makeshift port before.

No harm, no foul when it comes to testing though.....hopefully you'll learn a little something in the process.

[The enD 467]

I have no explanation for this. It is supposed to be tuned at 35Hz but it sounds louder at 64

Box is 1.9 net , port is 4.3 inch diamеter, 15 inches long... which is 34-35Hz

I was told that it is because I am playing it full range through my home audio amplifier, without a Xover?

Would it sound normal with a car amp? And what about the problem above?

[Impious 1,476]

I have no explanation for this. It is supposed to be tuned at 35Hz but it sounds louder at 64

Box is 1.9 net , port is 4.3 inch diamеter, 15 inches long... which is 34-35Hz

Really nothing unusual there. There are a few possible explanations.

First, your ear is more sensitive to sound at ~65hz than it is at ~35hz. A sound or tone at ~65hz may be perceived as louder to your ear than a sound or tone at ~35hz even though the actual SPL (as would be measured by a microphone) of the ~65hz tone is lower than the ~35hz tone. SPL competitors are well accustomed to this, and is the reason the experienced competitors will tell you that what is louder to the ear won't necessarily be louder on the mic. This effect has been studied and is known as the Equal Loudness Contour. As you can see from the graph, a 35hz tone requires approximately 10db higher SPL to sound equally loud as a 65hz tone to the ear.

Second, just because the enclosure is tuned to 35hz doesn't necessarily indicate there will be a peak in the output at that frequency. Depending on the parameters of the sub and how it responds in the enclosure you have it in, it's possible the output is actually lower at 35hz than it is at 65hz. It's also possible that the output from the subwoofer is pretty equivalent at 35hz and 65hz and you are simply experiencing effects of #1 above and #3 below.

Third, I'm not sure where you have the enclosure located or the specifics of the room, but you may be experiencing the effects of some room nodes which will affect the frequency response from various listening positions. While rooms in a house don't have the "cabin gain" that we experience in car audio, there will be locations in the room where the sound waves have constructive and destructive interference which will affect the frequency response.

I was told that it is because I am playing it full range through my home audio amplifier, without a Xover?

Well, yes, if you lowpassed the subwoofer and that lowpass filter attenuated 64hz you could of course make it sound less loud than 35hz. However, that's not the mechanism(s) causing what you are experiencing.

[The enD 467]

...

Thanks for the good explanation Impious. I really learned something new today.

So if I don't run a xover for my home use I won't loose the loudness at 65. Even though I listen to lots of rap, some songs hit pretty high and I'll just leave the box this way... peaking at lower and higher notes. Sounds good?

Then when I put in a car I'll just set the LPF and SS on the amp cutting above 80 or so.

[rodneydude23 5]

Thanks for the good explanation Impious. I really learned something new today.

x2 I think A lot of people who read this thread will learn something new

[The enD 467]

Third, I'm not sure where you have the enclosure located or the specifics of the room, but you may be experiencing the effects of some room nodes which will affect the frequency response from various listening positions. While rooms in a house don't have the "cabin gain" that we experience in car audio, there will be locations in the room where the sound waves have constructive and destructive interference which will affect the frequency response.

I have moved the woofa all around the room and walking around every corner with hours testing where it sounds louder.

I change it's placement again after I change the port. Sounds even better/louder.

Hell I even changed the placement of my computer just to be in the "sweet" spot when I listen to music.

x2 I think A lot of people who read this thread will learn something new

Yeah... I thought we are more sensitive to lower notes and the mic is going to show greater results at higher notes.

Edited February 25, 2010 by The enD

[The enD 467]

... and some more pics of the port work.

Old port and hole.

New port in

Not having the right tools, I made the hole a little bigger so I had to seal it up. Took some scrap wood, cut it with the table saw and made a raw hole(no tools again). Then I took my file and made a nice round hole.

So this is how it looks on the box. I have to seal it up nice, cover it with carpet and paint the port black.

Too bad I don't have the time cause my semester just started. Will finish when I'm back home.

Meanwhile... here are some pics of my "homemade" machines which I am planing to build a wall with.

Table saw

BIG ASS sander

Band saw

Remember, these were not bought. My father and I assembled them at home.

Feel free to add some comments