[anku94]

Originally Posted by Astleviz

# Thiele-Small-Parameter fs (Hz): 35 Thiele-Small parameters fs (Hz): 35

This is the resonant frequency, right ?

So is it the natural frequency of the speaker as a physical object, or is it the resonant frequency to AC current [1/(LC)^1/2] ?

I also read in the site, link of which was provided by LBMji (Thanks for the link BTW, it is the best place to learn audio basics : Basic Car Audio Electronics) that at the resonant frequency, impedance of the speaker increases. Could somebody explain this ?

EDIT : Oh, got it. I think...

The resonance being talked about is electrical resonance. And impedance depends on frequency. Right ?

[low_bass_makker]

Impedance increase means less power going to the driver.

[Invinsible]

Originally Posted by navin

this gives a sealed box of about 3 cu. ft. (80 liters) that is huge. A ported box would be larger ....in the region of 100 liters for a QB3 alignment.

What's the Qtc at 80lts? I guess you calculating at .707
If we look at the excursion limitation the sub will best perform in 30lts of sealed enclosure with Qtc of .85 which is good enough for in car use as there is also cabin gain that would add to the overall freq. response.

Ideally looking at the spec and freq. response the sub will be best suited for Sealed enclosure.
However 100L enclosure will make the sub go "BOOM" due to the excursion. The Fb is much lower than what the sub can handle at 23hz. ideally I would not consider below 35hz. Which would translate to the sub enclosure at 28Lts. If one looks at the the freq.response with this enclosure size, there is a peak of more than 6db above 50hz going all the way upto 100hz.
This could be one of the reason why the sub sounds boomy plus the port and enclosure resonance could add to it.
Honestly for a sub with an xmax of 8mm, higher qts I would suggest to have this sub in sealed enclosure with volume of 30lts for best smooth freq. response.

[navin]

Originally Posted by Invinsible

What's the Qtc at 80lts? I guess you calculating at .707
If we look at the excursion limitation the sub will best perform in 30lts of sealed enclosure with Qtc of .85 which is good enough for in car use as there is also cabin gain that would add to the overall freq. response.

Ideally looking at the spec and freq. response the sub will be best suited for Sealed enclosure.
However 100L enclosure will make the sub go "BOOM" due to the excursion. The Fb is much lower than what the sub can handle at 23hz. ideally I would not consider below 35hz. Which would translate to the sub enclosure at 28Lts. If one looks at the the freq.response with this enclosure size, there is a peak of more than 6db above 50hz going all the way upto 100hz.
This could be one of the reason why the sub sounds boomy plus the port and enclosure resonance could add to it.
Honestly for a sub with an xmax of 8mm, higher qts I would suggest to have this sub in sealed enclosure with volume of 30lts for best smooth freq. response.

I use Box Plot 3.0 (very old software).

I did assume a Qtc of 0.7. If one has a 30 liter box and a Qtc of 0.85 there will be a peak which can be then damped by going aperiodic.

I would NOT recommend a bass reflex box for this sub. The Qts is way to high for that.

[Vid6639]

Can someone add MS-8 to the glossary. :-)

[Invinsible]

Originally Posted by navin

I use Box Plot 3.0 (very old software).

I did assume a Qtc of 0.7. If one has a 30 liter box and a Qtc of 0.85 there will be a peak which can be then damped by going aperiodic.

I would NOT recommend a bass reflex box for this sub. The Qts is way to high for that.

Navinji The peak is not much, up by 2 db or so which can be taken by EQ. A cut off of 3db at 60hz should be fine na.
Or it could just add a little punch to it as the peak is at 50-60hz. In Some hatchbacks this adds to the sound while in sedan it could get little boomy. But I have noticed a true flat freq. curve/ response is not to everyones liking.
Winspeakerz is a better software that also gives in car response.
Aperiodic enclosure if not done right will not help much. If sealed enclosure size is not an issue it would be safer to stick to it while the peak in freq. can be taken care of with the EQ.
Apart from the qts. there could be excursion issues along with larger peaks in freq.

[Astleviz]

The ported basstube has a radius of 6 inches and a height of 18 inches, that makes the volume approx. 30+ L, right? So ideally, the sub should sound best if we seal the port completely. But stuffing the ports with socks doesn't change the sound characteristics at all, it still sounds the same, that's why the confusion.

[Invinsible]

Originally Posted by Astleviz

The ported basstube has a radius of 6 inches and a height of 18 inches, that makes the volume approx. 30+ L, right? So ideally, the sub should sound best if we seal the port completely. But stuffing the ports with socks doesn't change the sound characteristics at all, it still sounds the same, that's why the confusion.

I suggest you get a complete new MDF enclosure for the sub rather than using the bass tube. Resonance in MDF enclosure will be much lower than the bass tube. To calculate the volume of the bass tube you need to consider the diameter and length of the bass tube and not the port.

[DerAlte]

Originally Posted by vid6639

Can someone add MS-8 to the glossary. :-)

Sir, welcome sir!

Did you mean Mono Sodium glutam8 or Digital Sound Processor?

[Astleviz]

Actually the bass tube is going to be replaced by a type r sub with a custom sealed box in a couple of weeks. The only reason I was trying this out was because I found the cotton socks stuff interesting. Since I have auditioned sealed boxes (which I like) and ported boxes (which I don't like) but never next to each other, I wanted to experiment with the cotton socks stuff to see if my ears could make out the difference if I converted the same ported box to a sealed. Unfortunately, I couldn't.

BTW, I wasn't calculating the volume of the sub based on the port. The diameter of the basstube is 12 inches (radius 6 inches) and the length of the tube is 18 inches. That gives me an approx. volume of 33.3 L, right?

[anku94]

Does the following analogy accurately capture the meaning of gain settings ?

Consider a home water network with its pipes and taps. It has a main tap that controls the water sent to all the taps, and then it has tap at each outlet to control the amount of water that one receives from each outlet.

Here, the water is analogous to music, the main tap to amp gain settings, and the outlet taps to HU Volume Control.

If the main tap is not fully open, and allows only 10-15% of the water to the inner network, opening the outlet tap all the way will not allow you have the maximum water you can have.

Here the analogy starts to fail. Basically, what I mean to say next through the analogy, which I can't, is that if the amp gains are set too high, the sensitivity of the volume control will decrease, and even a little turning of knob will lead to too much of volume.

A proper gain setting will help us the balance the two situations.

Am I right ?

If I am, then I have a question :-

What if the amp gains are maximum and you start jacking up the HU volume knob too high ? Will it lead to too much of power being pushed through the components and lead to clipping etc ?

If it does lead to clipping and distortion, another question of mine is, why don't these components have some feature to not allow more power than what allows them to function at their peak ?

Thanks for answering.

[DerAlte]

Errrr... No, not the right analogy. 'Gain' is a multiplier in the mathematical equation of amplification (output = input * gain). Unity Gain leads to 0 amplification, i.e. output = input. Gain > 1 = proper amplification (output > input). If Gain < 1 (there is nothing called -ive Gain), it is call Attenuation, i.e. output is a fraction of the input. Gain = 0 leads to Output = 0.

In your analogy, the taps set Gain=0 when closed, and when open, Gain=fraction of input (max 1 when fully open). That is Attenuation, not Amplification.

[anku94]

Originally Posted by DerAlte

Errrr... No, not the right analogy. 'Gain' is a multiplier in the mathematical equation of amplification (output = input * gain). Unity Gain leads to 0 amplification, i.e. output = input. Gain > 1 = proper amplification (output > input). If Gain < 1 (there is nothing called -ive Gain), it is call Attenuation, i.e. output is a fraction of the input. Gain = 0 leads to Output = 0.

In your analogy, the taps set Gain=0 when closed, and when open, Gain=fraction of input (max 1 when fully open). That is Attenuation, not Amplification.

Oh...that's what I used to think initially, but drawing wrong inferences from a lot of reading confused me. Back to square 1.

So, what would be the difference if I used

1) Low input voltage and high gains
2) High input voltage and low gains

to achieve the same output voltage ? I get a feeling that it's the same theoretically but not practically.

[navin]

Originally Posted by Invinsible

Navinji The peak is not much, up by 2 db or so which can be taken by EQ.

Winspeakerz is a better software that also gives in car response.

Fair enough. You have better (more modern) software I should upgrade from my DOS and Win 3.11 (Windows for Workgroups) based systems.

Originally Posted by vid6639

Can someone add MS-8 to the glossary. :-)

Viddy the MS-8 is just one in-car processor. There are 100s of processors that do various things (most are equallisers) in a car audio system.

[DerAlte]

Originally Posted by anku94

... what would be the difference if I used
1) Low input voltage and high gains
2) High input voltage and low gains
to achieve the same output voltage ? ...

Yes, theoretically the same. However, practically the 2nd case - high input voltage and low gains - is preferred since less noise is transferred (proportionally) to the amp.

But, when using what is available (constraint on procurement or availability), one cannot be that picky and choosy - one pragmatically uses what is available to the best of its abilities. For example, if you have an HU that is perfect for you for your needs, and cannot get another one, AND the HU has 2V Pre-outs, it is better to accept it with high gain set at the amp - rather than fretting and fuming about it and not listening to music.

The objective is to listen to music. If one nit-picks the numbers involved, one only spends money and never gets to enjoy it, or does not spend money and spends the time miserably.