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Old 11th September 2009, 12:26   #1
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Talking got more bass by mistake!

Friends,
Today i was doing the DIY interior cleaning of my car, music was on and i found that the opening through which the air is pumped out from the sub box(i guess its known as port) is making a distorted sound which is spoiling the overall sq of the system. so i tried closing the port with my hand woooosh!!! the bass became so heavy and tight!i don't know what created this change. now i plugged in a peace of cloth so that it makes the hole air tight!
I checked the model of my sub and found that its a pioneer 305f 800 watts free air type sub which in my knowledge should be kept in the rear parcel try or some place like that. but my installer was an amateur in this field like me and installed in a box with a hole!
All these days i was searching for a good subwoofer for my amplifier. now am stopping the search! my amplifier and subwoofer are at least 7 yrs old and am so happy that its started beating like this after all this yrs!
Can any seniors please explain how this gain in the bass was gained when a ported box's hole was blocked?
An airtight box gives maximum punch? if so, why people normally use ported box?
Mine is just an entry level subwoofer and amplifier
Amplifier model is gm-x374 which just pumps around 70watts rms when bridged and my sub is an old model pioneer tsw-305f which has 300 watts rms.
Ihave seen people with 2 or 3 times more powerful setup using a ported box. whats the idea behind this?
I hope my invention by mistake will be helpful for many amateur's like me. and fellow bhpians please use this post for topics regarding this
thank you.
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Old 11th September 2009, 12:33   #2
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Search for Ported sub box and sealed sub box. The advantage of IB is that it simple to install and will need less power to play.Sealed will need more power though.

And the material the box is made of, the dimensions too play a major role in SQ.
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Old 11th September 2009, 12:47   #3
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Quote:
Originally Posted by althaaf View Post
I checked the model of my sub and found that its a pioneer 305f 800 watts free air type sub which in my knowledge should be kept in the rear parcel try or some place like that. but my installer was an amateur in this field like me and installed in a box with a hole!

Mine is just an entry level subwoofer and amplifier
Amplifier model is gm-x374 which just pumps around 70watts rms when bridged and my sub is an old model pioneer tsw-305f which has 300 watts rms.
The 305F is a free air sub. What you have created is not really a sealed box but a lossy box. Both Free AIr and Lossy boxes like woofers with high Qts which is prbably what the 305F has.

A woofer designed for a ported box in a probably designed proted box can sound just as good as your 305F in it's lossy box it was just that the ported box was not the corret box for the 305F.

You might find that by varying the ammount of damping you stuffed in the hole you can vary the lossy-ness of the box and thereby tune the woofer for your taste. If you google Aperiodic tuning you will find amny such examples from companies as reputed as Dynaudio and ScanSpeak.
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Old 11th September 2009, 12:55   #4
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Read this thread you will get a better picture

http://www.team-bhp.com/forum/ask-gu...ubwoofers.html
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Old 11th September 2009, 13:04   #5
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Thumbs up nice explanation

Quote:
Originally Posted by navin View Post
The 305F is a free air sub. What you have created is not really a sealed box but a lossy box. Both Free AIr and Lossy boxes like woofers with high Qts which is prbably what the 305F has.

A woofer designed for a ported box in a probably designed proted box can sound just as good as your 305F in it's lossy box it was just that the ported box was not the corret box for the 305F.

You might find that by varying the ammount of damping you stuffed in the hole you can vary the lossy-ness of the box and thereby tune the woofer for your taste. If you google Aperiodic tuning you will find amny such examples from companies as reputed as Dynaudio and ScanSpeak.
woow.. hats off to guru.
this was a new information for me. loosy box! so you are telling that people who has a free air type sub can opt for a box design which is a loosy type. right? earlier i could only feel the punch from the subwoofer. now i can feel the air being displaced from behind. am quite happy with the setup.
if you dont mind, can you put more light on this topic?
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Old 11th September 2009, 13:20   #6
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It is quite old. Aperoidic boxes have been around for a while. There is no free lunch though. Aperiodic boxes have often been used to reduce teh Qtc of a system so that the bass is not so peaky. The trade off is efficiency you might have noticed that your lossy box needs more power than the ported box.

I do not know what the exact tuning you have achieved but it mgiht well be that you have a very narrow band over which the bass is efficient. You might find that for some genres music the bas simple rumbles and is not well defined. Still if you are happy we are too.

Google is very efficient in digging up old AES papers on this topic. I am prety poor at Google though.
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Old 11th September 2009, 13:32   #7
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To add to that try getting the some specs on the sub, like to Fs, Qts, Vas, Qe value which will help in determine whether in what way sub can be played ported, infinite baffle or sealed. Most of these subs have higher Qts but with addition to VAS value could help in determine the optimum size of the enclosure needed. Every size in a given type of enclosure can give different sound from the sub.
Aperiodic tuning vent if put in a sealed enclosure helps in making the sub play as if its in a large enclosure and will give more smoother linear bass response as Qtc will be lowered. Adding a single Aperiodic tuning can add up to 20% more volume of the enclosure size. This would also require you to add some Poly-fill or fibrefill in an enclosure. Since adding a lot polyfill can also create heat energy in an enclosure which may not be good for the sub, Aperiodic tuning vent helps in that case. Google up for articles on "Aperiodic tuning vent" to understand it better.
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Old 11th September 2009, 13:34   #8
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Quote:
Originally Posted by navin View Post
It is quite old. Aperoidic boxes have been around for a while. There is no free lunch though. Aperiodic boxes have often been used to reduce teh Qtc of a system so that the bass is not so peaky. The trade off is efficiency you might have noticed that your lossy box needs more power than the ported box.

I do not know what the exact tuning you have achieved but it mgiht well be that you have a very narrow band over which the bass is efficient. You might find that for some genres music the bas simple rumbles and is not well defined. Still if you are happy we are too.

Google is very efficient in digging up old AES papers on this topic. I am prety poor at Google though.
what is qtc? but what i found is that i had to reduce the gain control on my amp after i did this tiny modification. earlier i could see my sub moving up and down very hard, but now after closing the port, the movement is reduced and movement is accurate without any loose movt after a punch. bass is very peaky also, but lost a little bit of sql and gained a lot of spl! and bass is available at all levels. i had read a lot of articles regarding this but what i gained today is against all those articles(thats what i personally feel)
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Old 11th September 2009, 13:43   #9
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Thumbs up mods

mods, can we please modify the name of the post to "aperiodic subwoofer tuning" i guess it will be a new information for a lot of amateur's and people who have entry level system.
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Old 11th September 2009, 13:45   #10
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Quote:
Originally Posted by althaaf View Post
what is qtc? but what i found is that i had to reduce the gain control on my amp after i did this tiny modification. earlier i could see my sub moving up and down very hard, but now after closing the port, the movement is reduced and movement is accurate without any loose movt after a punch. bass is very peaky also, but lost a little bit of sql and gained a lot of spl! and bass is available at all levels. i had read a lot of articles regarding this but what i gained today is against all those articles(thats what i personally feel)
Qtc: Qtc is the total Q of the speaker in an enclosure including all system resistances or value for the damping provided for a driver in a sealed enclosure. IN the case of a tuning quality Qtc of 0.707 results a frequency response, which runs as for a long time as possible linear and then fast drops (Butterworth alignment). Most home audio subs are designed in keeping this value. Higher values of Qtc will give a peak in the output with a sharper rolloff. Every enclosure size can be determined with the help of taking the parameters of the driver such as Fs, Qts, Vas along with the Qtc point. Higher the Qtc value lower the low end extension will be from the sub and will have a peak at above 60hz. To bring the Qtc down in sealed enclsoure on can add polyfill upto certain level and if needed can also add Aperiodic vent.
You may ask what is Q? Well Q is the magnification of resonance factor of any resonant device or circuit.

Last edited by Invinsible : 11th September 2009 at 13:52.
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Old 12th September 2009, 00:08   #11
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Quote:
Originally Posted by Invinsible View Post
Qtc: Qtc is the total Q of the speaker in an enclosure including all system resistances or value for the damping provided for a driver in a sealed enclosure. IN the case of a tuning quality Qtc of 0.707 results a frequency response, which runs as for a long time as possible linear and then fast drops (Butterworth alignment). Most home audio subs are designed in keeping this value. Higher values of Qtc will give a peak in the output with a sharper rolloff. Every enclosure size can be determined with the help of taking the parameters of the driver such as Fs, Qts, Vas along with the Qtc point. Higher the Qtc value lower the low end extension will be from the sub and will have a peak at above 60hz. To bring the Qtc down in sealed enclsoure on can add polyfill upto certain level and if needed can also add Aperiodic vent.
You may ask what is Q? Well Q is the magnification of resonance factor of any resonant device or circuit.
Even though everything u told went above my head, i agree that you are a real guru, an enclosure expert.

friends whoever has any info about aperiodic subwoofer enclosure, which people like me can understand, then please post here. am sure that it will be a new info/idea for a lot of fellow bhpian's.

Last edited by althaaf : 12th September 2009 at 00:10.
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