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Old 2nd July 2008, 16:16   #16
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Looks like you want good bass at lower volume levels. If that is the case why don't you do the following. Reduce the gain on the amp for the channel powering the front speakers. This will result in you having to increase the volume level in your HU in order to get to your listening level. This in turn ensures that you get more pre out voltage in your sub preout. Now adjust the gain in he channels of the amp powering the sub to the required level as per your preference. This should provide the bass you need at lower volumes. All this is in the assumption that you are not a person who listens to music at extremely high volume levels.

Gurus, if you feel this is idiotic, please don't bash me up. Just my 2 cents
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Old 2nd July 2008, 16:34   #17
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Dinu,
From his post what we can understand is that he has only one JBL 402 amp and that is powering the JBL 12" sub. He got only HU and OEM speakers other than this. As gurus pointed out, this amp is not sufficient for that sub, less that half of the wattage rating.

Trade in that amp for a bigger amp, or keep that amp for front speakers (later you can upgrade to comps and the amp will be useful) and get another monoblock (if you have a good budget) or a 2 ch amp which gives atleast 250W range RMS output when bridged.
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Old 2nd July 2008, 16:48   #18
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Quote:
Originally Posted by redfire View Post
Dinu,
From his post what we can understand is that he has only one JBL 402 amp and that is powering the JBL 12" sub. He got only HU and OEM speakers other than this. As gurus pointed out, this amp is not sufficient for that sub, less that half of the wattage rating.

Trade in that amp for a bigger amp, or keep that amp for front speakers (later you can upgrade to comps and the amp will be useful) and get another monoblock (if you have a good budget) or a 2 ch amp which gives atleast 250W range RMS output when bridged.
Oops I'm sorry, I thought it was a 4 channel amp, 2 channels for the front speakers and the other 2 bridged for the sub. Taking back my comments, sorry

Last edited by dinu2506 : 2nd July 2008 at 16:51. Reason: Mistake
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Old 2nd July 2008, 18:49   #19
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@raajsree, a relatively simple "heeng lage na phitkari..." method you could temporarily try - for those songs ONLY - is to reduce the mid and hi in the equalizer (your sub level is anyway at max) and then turn up the volume more than your normal setting.

Your permanent solution has to be a mono block (at least 300W rms @ 4ohms) and another 12" sub (you will effectively get a 2 ohms load), or a monoblock and an 15" or 18" sub (meant for a car; your 16" is a HT sub which will not work well in the car). So get your rokda ready. Gunbir, B&T etc. will be able to tell you some good makes & models that you can get.
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Old 2nd July 2008, 22:09   #20
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yep..I tried the equalizer trick but it all sounds like dead music....Does the equalizer has control over the sub out...?
anyhow the rokda is ready...
can i trade this amp for the new one...?
if so please do suggest me on how much should I sell this for..
and also suggest me amps for the existing JBL driver...
m not investing on 15" and 18" drivers for now (may be in the future)
and since the wiring is all done can I fix the new amp myself by just replacing the existing amp...?
Got This amp (kt5-a402) with the driver, enclosure, wiring and labour for 8k.. was it a good deal or...?
can I trade with the same shop keeper...? and other tips on shopping too please...?
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Old 2nd July 2008, 22:25   #21
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raajsree,

1. PM other Chennai members for good ICE shops in your area.
2. For the 12" JBL sub you would need an amp similar to JBL's 300.1 or better. Think 250W rms as a minimum. At 150W rms your sub is just about humming along in 2nd-3rd gear.
3. The Gurus in the ICE section have taken an oath to break any budget your dedicate to the betterment of your ICE so be warned. Fix your budget.
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Old 2nd July 2008, 23:13   #22
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After reading last couple of posts I suddenly feel that I am under-nourishing my sub. Its a JBL 12" CS series Tube powered by JBL GT-5 604 (4ch) amp.

I am not happy by the way it sounds. X-bass is kept at 0, if I increase it the sound becomes too boomy to my liking. I want the thump not the boom. I know that I actually should have taken a sub in sealed box but ....... My ATM Just Refused To Deliver Anymore.

Will shifting to a mono amp (like GT-5 3001) considerably improve the sound?
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Old 3rd July 2008, 10:28   #23
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Quote:
Originally Posted by ragzv View Post
I am not happy by the way it sounds. X-bass is kept at 0, if I increase it the sound becomes too boomy to my liking. I want the thump not the boom. Will shifting to a mono amp (like GT-5 3001) considerably improve the sound?
if the subwoofer's box is well made and desinged correctly the other factors for boom are
1. inadequate damping in the car (dynamat extreme etc.. will help)
2. inadequate electrical damping of the amp (a good monoblock will help)
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Old 3rd July 2008, 10:36   #24
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Quote:
Originally Posted by navin View Post
if the subwoofer's box is well made and desinged correctly the other factors for boom are
1. inadequate damping in the car (dynamat extreme etc.. will help)
2. inadequate electrical damping of the amp (a good monoblock will help)
The tube is by JBL. So I hope it is designed and made correctly- by JBL.

Navin, can you put some more light on electrical damping. What's that?
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Old 3rd July 2008, 11:41   #25
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Quote:
Originally Posted by ragzv View Post
The tube is by JBL. So I hope it is designed and made correctly- by JBL.
Navin, can you put some more light on electrical damping. What's that?
Tubes are generlly bommier than sealed box subs.

electrical damping can be defined as the Zamp/Zspeaker where Zamp is the output impedance of the amplifier and Zspeaker is the impedance of the speaker.

Note I said impedance and not resistance. impedace is complex and includes inductive and capacitive ingredients. resistance is simple. the simpler a speaker's impedance is the easier it is to drive so much so that in some cases a speaker with a nominal impedance of 4 ohms (but a relativel simple impedance curve) has been an easier load that a speaker with a higher nominal impedance.

impedance (becuase of it's capacitive and/or inductive elements) is frequency dependant, resistance is not. so the damping factor of an amp might be 500 at 400hz but 100 at 50Hz. since the higher the damping factor, the better the control the amp can exert on the speaker, in the above example it may be noticed that the amp controls the speaker very well at 400hz but not as well at 100hz (where the damping factor is lower).

A ported box (most tubes are ported) is more efficient (than a sealed box) since the back wave of the speaker is not fully absorbed but a portion of this backwave is being re-directed into the room. But such boxes can also prove to be a bit more difficult to drive. This is becuase unlike a sealed box, a ported box has 2 impedance peaks (and a valley between these peaks) one for the resoance frequency of the box (Fb) and one for the resonance frequency of the port (Fp). The problem is partly with these impedance peaks but more so becuase the valley between these peaks can be pretty low in impedance and challenge the amp. Fortunately this valley is narrow and the human ear is not very sensitive below 200Hz (where most subwoofers operate) so all's well.
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