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Old 1st July 2008, 22:05   #1
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Default Does adding one more sub make a difference?

Hi all!
I have a JBL amp (2-channel used only for SUB) and 12" JBL driver.
It works fine but when playing songs recorded at lower decibel levels I feel the need to intensify the sub. The Sub-woofer control in the head unit and the amp is set to full and still I find the need to intensify the sub for certain songs.
I know that, technically adding another subwoofer driver adds wattage in the output. But practically when heard, does it really make a sensible difference in adding another driver?
Has anybody using 2 subs (just for the low frequencies) find any reasonable difference when one of the driver is switched off...?
one more question..
How do they usually connect a single sub-woofer driver to a 2-channel amp-
whether they connect only one output channel and leave the other channel blank..?
or
they connect the driver to the 2 positive outputs leaving the ground...?
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Old 2nd July 2008, 01:29   #2
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Well, lot of factors contribute to this. What car do you have? I would check the installation first.

Having said that, I was never satisfied with the bass out of bridged 2 amp or 4 amp subs. Thats the reason I have a Monoblock Amp powering my sub. Its all about listening preference but until and unless you are heavy a bass guy a bridged 2-chn should suffice. Can you post the model?

Last edited by madbullram : 2nd July 2008 at 01:30.
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Old 2nd July 2008, 01:51   #3
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I have a tavera (though fond of innova landed with tavera as owning a GM vehicle was my father's dream and the shape !!!)

Will check the model of the amp and will post the model shortly...i remeber some screw adjustments in it. I have made the level to full and switched to bass boost and another switch to LF. I had even set the cut off frequency to wat I want in the amp and in the Head unit too!!!
The driver is a 12" JBL in a trapezoid box.

I usually listen to music that has wide range of frequencies in it (ranging from 20hz and below to 20khz and above). I am not concerned about the deeper bass as of now (as time demands I might go for a 16" or above sized driver). I m juz satisfied with the frequency (the depth as of now). I m concerned about increasing the sub level (intensity or the decibel) without increase in the other range of frequencies (only for songs that demand).

Now since I took the topic of going above 16" I just wanted to know whether the current amp will be able to drive the over sized driver (16"and above)....?

and Ram have u tried 2 sub (only for the lo-frequencies) with 2-ch amp and found any difference by switching one of them off...?
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Old 2nd July 2008, 01:58   #4
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Quote:
Originally Posted by raajsree View Post
one more question..
How do they usually connect a single sub-woofer driver to a 2-channel amp-
whether they connect only one output channel and leave the other channel blank..?
or
they connect the driver to the 2 positive outputs leaving the ground...?
I'd think none of the above, if bridging. You connect the sub-woofer +ve to the +ve of channel A and sub-woofer -ve to the -ve of channel B.

However, if one channel of the amp is powerful enough to drive the sub, then your first option should work.

Last edited by shuvc : 2nd July 2008 at 01:59.
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Old 2nd July 2008, 02:07   #5
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I dont really think that adding another woofer would add marginally to the output. I guess you should experiment with the enclosure.
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Old 2nd July 2008, 02:18   #6
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I think it will, if you need good bass through a wider frequency range.

It's like having a twin turbo engine where the small turbo provides boost at low revvs while the big turbo takes it away from where the small one left off.

Shan2nu
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Old 2nd July 2008, 02:29   #7
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Not bad idea but will it really offset the extra cost factor ?

I guess since the guy has already a 12" JBL, he should have ample bass. Had I been at his place, I would have first tried to do some modification to the enclosure.
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Old 2nd July 2008, 03:43   #8
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Whoa, back the truck up guys...

Raaj, first things first, please mention the the details of your setup. What model HU, what amp, speakers, sub etc.

It seems that your system is setup all wrong. There is no reason your gains should be set to full, your sub level set to full, your bass boost on etc

We need to take this step by step. Please let us know your system details and we can guide you further.
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Old 2nd July 2008, 09:09   #9
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To all
JBL amp=gt5-a402 amp
input level can be adjusted from 6V to 200mV (now set at 200mV)
JBL driver = csseries (it says dual magnet heavy duty but uses only 2 wires which is bridged in the amp) 1000watts max
Head unit =JVC kd-dv7406
Door and rear speakers = Kenwood OEM
I intend to use the JBL amp and driver only for the LF. The combination performs perfect for a balanced output.

Now when there is a need (say when there is a mood or when playing the songs of mid 80's or 90's) I feel the need to increase or boost the SUB.

Please note the combination works perfect for a balanced sound and can even give the extra bass I need (sometimes more than what I need) for songs that has been properly recorded. The problem is with mid 80's and 90's songs

I found the equalizer in the Head unit not boosting the SUBS (this is usual I believe)


Quote:
Originally Posted by Shan2nu View Post
I think it will, if you need good bass through a wider frequency range.

It's like having a twin turbo engine where the small turbo provides boost at low revvs while the big turbo takes it away from where the small one left off.

Shan2nu
This is what is happening now. I tuned the SUBS to below 85hz and the front and rear components to above 135hz (I hate frequencies between 60hz and 150 hz). I m enjoying it. But have plans to add a driver above 16" (dont know whether the space would accomodate and doubt whether the current amp would drive)

Quote:
Originally Posted by shuvc View Post
I'd think none of the above, if bridging. You connect the sub-woofer +ve to the +ve of channel A and sub-woofer -ve to the -ve of channel B.

However, if one channel of the amp is powerful enough to drive the sub, then your first option should work.
Bridged it is...
Checked it this morning....
I at home connect the 2 positive outputs which provides a surround sound and it misses the sounds common in the channels.
If u want a cheapest surround sound system just connect the 2 positive rear outputs of the Head unit to the rear speakers and the rear speakers should be paralleled. Though u get only a single channel in the rear the front left and right channels will aid in making u believe that there are 2 seperate channels in the rear virtually. For this u need to have fader control in the head unit since the rear will boost up in such a set up.
I have not tried this is in car Head units so I m not sure how good this would work.
The gurus can throw light on whether such a connection would induce noice (...?) or it would damage the Head unit amp (...?).
At home this works perfect - no noise or no harm to the amps... May be I should post this in a seperate thread...I will...
Now more about the subs please...
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Old 2nd July 2008, 13:26   #10
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@raajsree bhaya, please step back and re-examine what you are trying to do. This is like trying to fish in Kooum - it is a river but not the type that can sustain marine life!!!
Quote:
Originally Posted by raajsree View Post
JBL amp=gt5-a402 amp Can give only 120W rms @ 4ohm bridged
JBL driver = csseries (it says dual magnet heavy duty but uses only 2 wires which is bridged in the amp) 1000watts max 275Wrms SVC 4ohms sub, of course it will only use 2 wires. Dual magnet heavy duty has nothing to do with number of wires
...I intend to use the JBL amp and driver only for the LF.
The Great Khali being fed a weight reduction diet!!! Bechara, what strength will he have to fight?
Quote:
Originally Posted by raajsree View Post
The combination performs perfect for a balanced output.
Now when there is a need (say when there is a mood or when playing the songs of mid 80's or 90's) I feel the need to increase or boost the SUB.
Please note the combination works perfect for a balanced sound and can even give the extra bass I need (sometimes more than what I need) for songs that has been properly recorded. The problem is with mid 80's and 90's songs
Perfect, no doubt. "The problem is with mid 80's and 90's songs" - exactly. Sir, those songs (assuming your are talking of Hindi and Tamil songs) had maximum bass content in the region that you hate: 60-150Hz. You have excluded that region in your system, and you want the sub to compensate for that? Unfair, kiska joota kiska sar!!!
Quote:
Originally Posted by raajsree View Post
I found the equalizer in the Head unit not boosting the SUBS (this is usual I believe)
Your system is maxed out - will happen only under such circumstances.
Quote:
Originally Posted by raajsree View Post
... But have plans to add a driver above 16" (dont know whether the space would accomodate and doubt whether the current amp would drive)...
Sir, please take time to read what sizes of speakers and subs are available normally. A 16" you will have to make yourself - then only next size normally suitable for a car is 18", that also only 1 or 2 makes.
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Old 2nd July 2008, 13:38   #11
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Quote:
Originally Posted by DerAlte View Post
A 16" you will have to make yourself


Or he could use 2 x 8"

2 x
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Old 2nd July 2008, 13:50   #12
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Lightbulb input level adjustment knob/screw in an amp

Quote:
Originally Posted by raajsree View Post
...input level can be adjusted from 6V to 200mV (now set at 200mV)...
...
I dont think this should be used as a volume control : it should always be one position for a given pre-amp (HU), and that position should match the output level of the pre-amp (HU).

For eg, if the output signal level from your HU is 2V, then this knob in the amp should be adjusted to be at 2V : this will then result in the bass level increasing and decreasing proportionately when you increase/decrease the volume control in your head unit.

Otherwise the bass will increase/decrease not in sync with your volume control movement.
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Old 2nd July 2008, 14:52   #13
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Quote:
Originally Posted by raajsree View Post
I have a JBL amp (2-channel used only for SUB) and 12" JBL driver...The Sub-woofer control in the head unit and the amp is set to full and still I find the need to intensify the sub for certain songs...Has anybody using 2 subs
The amp you have is the bare miminum for even a single 12" sub. It wont make much sense getting a second 12" sub. You might be better off getting a bigger amp.

ref 16" subwoofers:
A few companies make 16" (better known as 40cm) subwoofers. All of them are rather expensive (I have heard the Focal Audiom 40cm woofer in a home audio system and it rather good) and demand very good amplification.

There are however cheaper 15" (38cm) subs that subs avaiable still most of these are happy only when fed with 500W rms +.
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Old 2nd July 2008, 15:04   #14
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Quote:
Originally Posted by DerAlte View Post
This is like trying to fish in Kooum - it is a river but not the type that can sustain marine life!!!
A creature is yet to evolve, that can be sustained in that beautiful fragrant river.
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Old 2nd July 2008, 15:20   #15
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Default Thanks for all that pranks

Ok..
It seems like u all had good fun...
enjoy it...!!

DERALTE bhaya thanks a tonnnnn...not for the lark but to point me out in the right direction...
I din choose this combination anyhow...but it sounds decent (if not perfect) to me.
Before buying told the shop keeper to give me a combination of SUB that would not give JARRRR at any instance...So i believe the diet is justified...Please do comment...!!!
Does this mean I need better amp to boost the SUB?

I didnt note this difference till u pointed out. I believe in wat I hear than in specs...But the spec seem to have played here...

About the LF
S I do know 80"s 90's LF ranges between 60 and 135Hz. But there are few songs in that range (Namakhalal-Hindi, agni natchathiram-tamil, Mannan-tamil and few more) that gives these low frequencies which when heard loud (only the LF) reaches direct to your heart and feet (the vibrations) and u feel like u r in heaven.... (thats how I feel). May be thats too much for the amp I have.

u are really involved in this. U got to the point. Thanks DERALTE...(wats ur name..?)
and for the senior BHPian Bass &trouble seem to be knowing a lot (2x8")
Nice to meet u guys here...

About the size...
I m not well versed with the car-audio market availability.
But I have a magnet lathe nearby and a speaker coil maker (don know what do u call them technically) they make drivers of sizes u wish and match it with a perfect coil and cone. I have a friend who got a second hand theater woofer and paired it with another made from these guys (both of size 20"+) driven by a kenwood HDMI compatible home theatre unit and u could imagine how would this sound in a 12' X 18' hall (hell in hall). If anyone wishes to thunder ur room-theatre call me I can help...
Also I do have a 16" pioneer driver (not using much) at home.


Quote:
Originally Posted by Blue Thunder View Post
I dont think this should be used as a volume control : it should always be one position for a given pre-amp (HU), and that position should match the output level of the pre-amp (HU).

For eg, if the output signal level from your HU is 2V, then this knob in the amp should be adjusted to be at 2V : this will then result in the bass level increasing and decreasing proportionately when you increase/decrease the volume control in your head unit.

Otherwise the bass will increase/decrease not in sync with your volume control movement.
M not using it as a volume control.
May be wat I did was wrong though...
I have a SUB level control in the head unit.
Since the amp level control is not accessible easily I had set it to max and I control the SUB level from the head unit.
Does doing this way harm the amp...?
I dont find any distortion in the SUB anyhow...So i thot its no harm...Please do advise...
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