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Old 9th April 2009, 10:12   #76
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Bhgwan's enclosure is made of concrete. Bhagwan and I follow slightly different lines of thinking.

1. Bhagwans boxes are so heavy and inert that there is no possiblity of flex. This works well becuase of the sheer rigidity and mass of the material.

2. My theory is that heavy boxes will only store that much more energy which (because energy cannot be destryoed) will have to be released at some time even if the time-constant of the box is very long. So the object I believe (and I can be wrong) is to make the box stiff and non resonant without adding mass. Since most resonance damping materials have some mass these boxes are not 'featherweight' but becuase there is no granite, concrete or such materials involved they are not as heavy either.

MDF is a great option as it is by nature reasonably non resonant. Fiberglass (resin bonded) offers a better stiffness to mass ratio that most materials even steel without being overly resonant (more resonant than wood, less resonant than steel) and finally one can use void free (good ISI brands are void free) marine grade ply. Becuase the speed of sound changes based onthe desnity of the material it has to pass though using materials of vrying densities can also help. So one option is to create a sandwich starting with (from the outside to the inside) marine grade ply, loose fiberlgass used in insulation, resin bonded fiberlgass, foam or other soft material, and MDF. The 5 layers each of an average of 4-6mm each will give you a stiff non resonant structure about 25-30mm thick that is stiffer and more inert than a similar gradeof MDF. This is only something a DIYer can do. The baffle however cannot be constructed this way. You have to delete the loose fiberglass and soft foam layers for the baffle. One option is to build a floating baffle.
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Old 9th April 2009, 10:18   #77
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Quote:
Originally Posted by low_bass_makker View Post
Care to link the thread. We can view it even if it is locked.

And I cannot find the Feb 2005 issue on the site given by you Care to help in that department too.
Abhi care to help here I cannot not find the thread
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Old 9th April 2009, 10:26   #78
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Originally Posted by low_bass_makker View Post
I cannot not find the thread
Duck guys the sky is going to fall. LBM cant find something using Google!

LBM if you cant find something what hope do the rest of us have.
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Old 9th April 2009, 15:47   #79
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Quote:
Originally Posted by navin View Post
Duck guys the sky is going to fall. LBM cant find something using Google!

LBM if you cant find something what hope do the rest of us have.
Quote:
Originally Posted by low_bass_makker View Post
Abhi care to help here I cannot not find the thread
Paaji you are getting old now.

Here is the thread:
http://www.team-bhp.com/forum/sound-...ss_makker.html

Go through the whole thread it will bring some long lost memories
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Old 9th April 2009, 19:52   #80
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Quote:
Originally Posted by navin View Post
Duck guys the sky is going to fall. LBM cant find something using Google!

LBM if you cant find something what hope do the rest of us have.
Quote:
Originally Posted by abhibh View Post
Paaji you are getting old now.

Here is the thread:
http://www.team-bhp.com/forum/sound-...ss_makker.html

Go through the whole thread it will bring some long lost memories
Navin Ji I am not getting old but try to motivate the younger ones so that they can become experts. But I think Abhi still needs training as he can give us the link but cannot point out there it is....Here Abhi some thing for you...


http://www.team-bhp.com/forum/663239-post1244.html

And it was taken from this woofertest_autohifi_02_05.pdf which was given to me by Ajay Bhai....

If we go to the site mentioned by you AUTOHIFI..we arrive to this page...

autohifi-magazin.de - La Boom

And to download the article we need to pay as it is not a direct download. Hope it clears some doubts...


Now about the cabin gain of a hatch and a SUV. In the chart posted below we can see that...

Name:  111023.jpg
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The cabin gain for 40 hz in a hatch it is +17db and +19 db for the van/bus (it would be more for a SUV as it is smaller than a van/bus). And at 50 hz it is +18 db and +14 db respectively.

Why I am taking 40 and 50 hz because the peaks occurring in the car were at these freq as you can see in the pics below...

Which Subwoofer and Amplifier-dscn0401.jpg
Which Subwoofer and Amplifier-untitled1.jpg

But if we observe the same we see the opposite as mentioned in the above chart. The peak in the hatch is 45 hz and the peak in the suv is 50 hz.

The spectrum analyzer gives us the peak at which the cabin and the sub makes the maximum output.

A little more coming up very soon.......going out for a dinner.
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Old 9th April 2009, 20:02   #81
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Till then here is something...

Which Subwoofer and Amplifier-img_2777-large.jpg

Which Subwoofer and Amplifier-img_2790-large.jpg

Which Subwoofer and Amplifier-bhbkj.jpg

Which Subwoofer and Amplifier-img_2793-large.jpg

Which Subwoofer and Amplifier-156.6.jpg

Which Subwoofer and Amplifier-img_2796-large.jpg
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Old 9th April 2009, 21:57   #82
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Quote:
Originally Posted by low_bass_makker View Post
But I think Abhi still needs training as he can give us the link but cannot point out there it is....Here Abhi some thing for you...

http://www.team-bhp.com/forum/663239-post1244.html

And it was taken from this Attachment 123236 which was given to me by Ajay Bhai....

If we go to the site mentioned by you AUTOHIFI..we arrive to this page...

autohifi-magazin.de - La Boom

And to download the article we need to pay as it is not a direct download. Hope it clears some doubts...
Training on what ? huh ?

You asked for Thread URL and i gave you the URL. There was nothing asked about specific POST link.

And here is the direct download URL for the file i read regarding subwoofer test!
http://www.bluesound24.com/artikel_d...r6000_test.pdf

Its the same file, but atleast its a direct download and you don't have to pay for it

Just some more off topic stuff. I am amazed you don't remember you posted it on your thread. It was one of the most active threads at 1 time.

And AFAIK you are quiet famous for googling as Navin Ji pointed out and well versed with almost every thread / post at ICE section.

Quote:
Navin Ji I am not getting old but try to motivate the younger ones so that they can become experts.
If i would have posted the specific link to the post or direct download earlier, would that make me an expert ? I don't really think so.
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Old 10th April 2009, 11:17   #83
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@abhibh.. dont get personal yaar! chill!

any theories to rule out the findings as pointed out by LBM? i was about to post those but LBM did.

healthy comments please. :-)
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Old 10th April 2009, 13:09   #84
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Quote:
Originally Posted by low_bass_makker View Post
Now about the cabin gain of a hatch and a SUV. In the chart posted below we can see that...
The cabin gain for 40 hz in a hatch it is +17db and +19 db for the van/bus (it would be more for a SUV as it is smaller than a van/bus). And at 50 hz it is +18 db and +14 db respectively.

Why I am taking 40 and 50 hz because the peaks occurring in the car were at these freq as you can see in the pics below...
Oh my sweet mad sardar.

The charts dictated transfer function. Your measurements showed peak.

Transfer function does affect the peak but is still different from peak SPL readings.

1. The peak SPL reading is a mix of the music played, transfer function, capabilities of the speaker under test, dampiing factor of amp, etc..
2. The transfer function is a average of many cars usually at 1W or 90db or at some far lower levels than peak levels.

That said if you notice your reading showed a peak at about 45-50Hz. The transfer fuction also showed that there was a 17-19db boost in this area so it does co-realte to my earlier said thoery that the transfer function does affect the peak readings however given that
a) the transfer fucntion graphs show a rise above 40Hz in most cases (other thant he van)
b) there is a more information at about 90+Hz in one of your loudest readings
http://www.team-bhp.com/forum/attach...fier-bhbkj.jpg

I suspect that my later contention - that SPL peak readings are dependant on many factors - has some weight. The 90+Hz info might well be a harmonic of the 45Hz peak info which might mean that the 45hz peak reading might have been due to some other panels vibrating in the car (excited by the very high SPLs) and not direct sound from the loudspeaker under test.

Since I have not been witness to these tests I cant be sure. You can since I assume you have taken these measurements yourself. BTW please get some good ear plugs you gonna go deaf soon if you keep subjecting yourself to these SPLs.
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Old 10th April 2009, 13:24   #85
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Quote:
Originally Posted by navin View Post
I suspect that my later contention - that SPL peak readings are dependant on many factors - has some weight. The 90+Hz info might well be a harmonic of the 45Hz peak info which might mean that the 45hz peak reading might have been due to some other panels vibrating in the car (excited by the very high SPLs) and not direct sound from the loudspeaker under test.
A little more on this...The 90hz is produce by the speaker itself since in the 166 db screen the sensor was in the port. And in the enclosure there would be a wide spread of freq which would not be in the car cabin due to the transfer function. And if there is a peak it will be in a very small freq range like in all the pics shown above. It is not possible in a car environment to produce a very large band of freq (like from 40-55 hz) is not possible to play at a near/equal db level.

Last edited by low_bass_makker : 10th April 2009 at 13:29.
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Old 14th April 2009, 04:04   #86
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Quote:
Originally Posted by low_bass_makker View Post
The 90hz is produce by the speaker itself since in the 166 db screen the sensor was in the port
And now i wonder about all those DB figures which you have posted on TBHP. I seriously hope the sensor was not in port when those were recorded, because if they were i will seriously be disappointed.

Last edited by abhibh : 14th April 2009 at 04:06.
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Old 14th April 2009, 12:06   #87
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And now i wonder about all those DB figures which you have posted on TBHP. I seriously hope the sensor was not in port when those were recorded, because if they were i will seriously be disappointed.
ah so you noticed. If you check all the photos you will see only two pictures that are the odd one out. One is 166 db which is taken by me and the sensor was inside the port and the other one is the 151 db in which again the spread is wide maybe due to the sensor in the port else such a wide spread in not possible in car. Also I have taken the 166 db pic because I wanted to show I was not bluffing and the reading I was taking were real. Rest people here are quite knowledgeable to understand things.

Forgot to add the 152.7 db picture.
Which Subwoofer and Amplifier-98001.jpg

You again can see the spread it is peaking around 55 hz
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