[Invinsible]

Originally Posted by Ravi Nandrajog

Hi brother, all these details come along in the manual provided with any branded woofer.
Custom build enclosure as per the company specs dont forget your car boot space.
Practically as per what i have experienced the fibre fill and poly fill dont help much.
What matters in a sealed enclosure is volume, sturdiness and sealing .

How do you think the company decides what enclosure fits the best for a given particular sub ?
What relation does the enclosure have with the boot space ?
Poly fill/fibre fill is used even today all around the globe. Some of the high end home subs are still stuffed with either one of them. It is best suited in case one builds a touch smaller enclosure against the actual required size.

Stuffing a box with polyfill makes it seem larger and it all relates to thermodynamics. When polyfill is added to an enclosure, it changes the behaviour of the airspring in the enclosure from "adiabatic" to "isothermal". The term "adiabatic" implies that there is no heat transfer occurring. An isothermal process occurs once the polyfill has been added. As the air passes through the polyfill, the fibers wiggle and cause some of the energy created by the airspring to be dissipated as heat. This heats the surrounding air molecules warmer, causing the air to become less dense. Being that sound passes easier through a denser medium, the speaker interacts with your enclosure as if it is larger than it actually is. The effective increase in enclosure size can be as much as 40%!

This has some very obvious benefits that are inherent of a larger enclosure. Firstly, it becomes more efficient (a larger enclosure is always more efficient than a smaller one for any given driver). Second, the f3 (or the frequency at which SPL is down by 3dB) will be lower, providing a little bigger bottom end. While these are both great advantages, they decrease the effective damping of the speaker as well, meaning the speaker can be more likely to bottom out or over-excurt itself. Naturally, this is speaker, frequency, and power dependent. If used in a ported enclosure, you will also see the Fb (or the resonant frequency of your port) drop lower.

There are some additional worthy considerations. Adding polyfill to an enclosure can be a great choice. However, too much polyfill can be a bad thing. At a certain point, the stuffing becomes too dense and the fibers no longer wiggle. At this point, not only have you taken away the size benefit of adding polyfill, you have actually decreased the effective volume as the polyfill is now taking up room inside your enclosure. It is also worth mentioning that polyfill is not as effective in a large enclosure.

[DocG]

Originally Posted by Invinsible

How do you think the company decides what enclosure fits the best for a given particular sub ?
What relation does the enclosure have with the boot space ?
Poly fill/fibre fill is used even today all around the globe. Some of the high end home subs are still stuffed with either one of them. It is best suited in case one builds a touch smaller enclosure against the actual required size.

Why not just build an enclosure to the desired size, then there is no real use for polyfill. I agree with almost all of what you said.

There are newer and more modern and efficient materials that can be used. I've seen people using regular damping materials (Like DE/NK) and purpose engineered damping like Dynamat's Dynaxorb. God I love these little sheets, they're just impressive in their capabilities, and somehow I feel that it'd be more efficient than polyfill for the desired purpose. Only problem however is the cost.

[sreejeshmp]

Thank you for support and valuable information. I finished the Enclosure design and fitted in to the boot. The performance is on the mark what I expected.

[Epic]

Hi all,

Ive read through this entire thread which involves alot of technicality and makes alot of sense. So is it safe to say that, a company made enclosed subwoofers are the best bet as I am sure their enclosures are made as per specifications? If so, why are subwoofers (except for free air subwoofers) sold without a box then? Why dont all companies sell subwoofers with the box matching their specifications as standard?

Also, here's my experience. I was using the Infinity Ref1200T ported bass tube in my Swift which i purchased from a JBL Store for 12k & after almost 2 yrs, the cone fell into the tube. I was shocked & disappointed by this kind of craftsmanship by Infinity. On opening the tube, we found that there was nothing great about it as the inside of the tube was made out of a material which resembled card board. I guess the exterior was wood, but not sure as it was carpeted. We decided to scrap the tube & install the subwoofer in a sealed enclosure. I believe these enclosures are a standard size. The sound is much better than when it was in the tube. I still want to make an enclosure with the correct specifications for this sub.

Here are the specifications for the same :

Subwoofer Type - 300mm
Enclosure Design - Vented Tube
Max Power - 1200 Watts
RMS Power 300 Watts
Sensitivity - 95dB (1Watt/1m)
Nominial impedence - 4 Ohm
Frequency Response (-10dB) - 35-120 Hz

What would be the right type & dimensions of the enclosure for this sub?

[sreejeshmp]

The easy way to design your subwoofer enclosure is calculate the volume of your original tube enclosure and make a sealed enclosure with the same volume. So you can get the max performance and suitable shaped enclosure for your swift.

[Ajaybiz]

This box is quite big, if sub will get matched power from the amp even a small box does a wonder. Check this as i am using 10" DVC Infinity 1062 sub in hardly 0.5 cubic feet box which come to around 14-15 liters, it punches really hard and very tight punches.
http://www.team-bhp.com/forum/ask-gu...ml#post1536504
http://www.team-bhp.com/forum/ask-gu...ml#post1482404

[Epic]

Originally Posted by sreejeshmp

The easy way to design your subwoofer enclosure is calculate the volume of your original tube enclosure and make a sealed enclosure with the same volume. So you can get the max performance and suitable shaped enclosure for your swift.

Well Sreejesh,

Thats a very good idea but unfortunately for me, my sub is now over 3 yrs old. Also, it was originally a ported bass tube & now it is installed in a sealed box. I tried to google the specifications for this bass tube (Infinity Ref 1200T) but it is nowhere to be found. All In know is that the dimensions of the tube are apparently 370mm X 700mm. I have no idea what the volume is in litres. Hence, based on the specifications mentioned in my previous post, I hope to find out the dimensions of the sealed/ported box applicable for the same.

Does anyone know of any website which has a calculator where one can feed in the specifications of the subwoofer & get the dimensions of the required enclosure?

[Invinsible]

To determine the ideal enclosure and its size whether ported, sealed or bandbass we need some T/S parameters like the Fs, Qts, Vas, Qes.
These parameters can help in determine what enclosure size range can be worked on.
In your case we dont have these details on it which can help to determine whats the best suitable size. Just randomly picking up a size could work but in some cases could even be harmful for the sub if the sub may put out some low end response which it may not capable enough to handle, in which case on long run there could be mechanical failure.

[Epic]

Originally Posted by Invinsible

To determine the ideal enclosure and its size whether ported, sealed or bandbass we need some T/S parameters like the Fs, Qts, Vas, Qes.
These parameters can help in determine what enclosure size range can be worked on.
In your case we dont have these details on it which can help to determine whats the best suitable size. Just randomly picking up a size could work but in some cases could even be harmful for the sub if the sub may put out some low end response which it may not capable enough to handle, in which case on long run there could be mechanical failure.

Sorry Invinsble. I know you got all this through Google, but then so did I. Unfortunately for me, T/S, Fs, Qts, etc...... is all Greek to me. I dont even know what they mean or stand for. If you could be kind enough to explain these short forms, I am sure they would help me & everyone else on this forum. Besides, once I get to know what these mean, I can start finding them out & plan the enclosure accordingly

[greenh0rn]

Originally Posted by Invinsible

In a Small sealed enclosure powered close to the given rated power will have better control over the sub and the frequency will sound good tight with good low end extension.

Sorry if I have the knack of sticking my neck in and asking questions in someone else's thread- but tell me if by powering my 400wrms sub with a 2ch-bridged JBL 1004 amp (around 280wrms or so) translates to an underpowered sub?

Originally Posted by Epic

Sorry Invinsble. I know you got all this through Google, but then so did I. Unfortunately for me, T/S, Fs, Qts, etc...... is all Greek to me. I dont even know what they mean or stand for.

I don't think you even need to venture beyond Team-BHP into the deep dark world of Internet to understand who was Thiele and who was Small and why did these fellows create a set of parameters for folks like us to bang our heads with. But if Google can help Invinsible, myself and others, so it can you.

[Epic]

Originally Posted by greenh0rn

I don't think you even need to venture beyond Team-BHP into the deep dark world of Internet to understand who was Thiele and who was Small and why did these fellows create a set of parameters for folks like us to bang our heads with. But if Google can help Invinsible, myself and others, so it can you.

My dear Greenhorn,

I believe Team BHP is a forum which helps one understand technicalities of automobiles & other stuff related to them in lay man's terms. If Google was the answer to everything, we would'nt have this forum in the first place. Just like Invinsible, even I Googled it but needed someone on the forum to help with these technicalities if possible.

Anyway, please feel free to suggest otherwise which will help with my enclosure.

[sreejeshmp]

According to the dimensions (370 mm x 700mm) your tube volume is 74 liters.
(1 liter = 61 cubic inches)

So you can build a sealed enclosure with a volume of 74 liters. I am not sure about the dimensions you have given. Do a 300mm subwoofer (11.81“) need 74 liter enclosure?? So confirm the measurements and recalculate the volume.

Use this link to download the enclosure design tool.
Where you can enter the specifications of the subwoofer & get the dimensions of the required enclosure.

AJ Audio Subwoofer Box Enclosure Design Software - Sub Speaker Cabinet Building Program Downloads

[Invinsible]

Originally Posted by Epic

Sorry Invinsble. I know you got all this through Google, but then so did I. Unfortunately for me, T/S, Fs, Qts, etc...... is all Greek to me. I dont even know what they mean or stand for. If you could be kind enough to explain these short forms, I am sure they would help me & everyone else on this forum. Besides, once I get to know what these mean, I can start finding them out & plan the enclosure accordingly

Lol.. Sorry Epic if google had all the answers, I dont think many hear would have googled for the Answers. More than google the info stated comes fromm past 15 years of experience and investment in car audio and home.

Cheers!

[Epic]

Originally Posted by Invinsible

Lol.. Sorry Epic if google had all the answers, I dont think many hear would have googled for the Answers. More than google the info stated comes fromm past 15 years of experience and investment in car audio and home.

Cheers!

Hey its just that I found the same technicalities that you mentioned in your post when I was Googling for ways to find out how to make an enclosure for my sub based on its size, output & other specifications. I am not doubting your 15 years experience & investments in your car & home audio. All I am saying is that please help & explain it to me & many others on the forum who does not understand these technicalities & dont have that kind of experience in car & home audio.

Thanks!!

[Epic]

Originally Posted by sreejeshmp

According to the dimensions (370 mm x 700mm) your tube volume is 74 liters.
(1 liter = 61 cubic inches)

So you can build a sealed enclosure with a volume of 74 liters. I am not sure about the dimensions you have given. Do a 300mm subwoofer (11.81“) need 74 liter enclosure?? So confirm the measurements and recalculate the volume.

Use this link to download the enclosure design tool.
Where you can enter the specifications of the subwoofer & get the dimensions of the required enclosure.

AJ Audio Subwoofer Box Enclosure Design Software - Sub Speaker Cabinet Building Program Downloads

Oh now here's a useful reply Thanks Sreejesh. Will check out the link & see if I can manage something.