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Old 13th July 2005, 12:42   #76
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http://www.carsound.com/review_archi.../cda-7875.html

There are many such HU's but honestly, I've never ever seen a HU that sounded quite like even a small amplifier. I'm sure Navin will agree with me here. (for a change )

Last edited by Sam Kapasi : 13th July 2005 at 12:48.
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Old 13th July 2005, 12:46   #77
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Quote:
Originally Posted by Sam Kapasi
I think you're a little confused. 99.99% of all head units (single AND double din) have a built in 4 channel Amplifier....While the Head unit may have enough power to drive speaker,s it doesnt have enough power to drive a Subwoofer, that typically requires a lot more power.
1. Yeah and trust me to get the 0.01% HU (Alpine 7385 circa 1987) it had Dolby C (ok now that CD is in noone needs this) and NO amp. :-)

2. typical good HUs have about 10W rms per channel at about 0.1% distortion from 20-20kHz. Many have less than that.

Typical car speakers are less than 90db/1W/0.5m. in fact the few midbasses I tested (in the 80s and i dont think much has changed here) all fell below 88db/1W/1m (without any crossover connected) at 400Hz.

In addition to this larger diameter drivers (8"+) esp. free air drivers have big Mms numbers (Mms is Moving mass of Cone including the mass of air moved). This is required so that Fs is low enough and Qtc (Q of driver in install/system) stays within reasonable limits (not too high or low).

Moving this huge Mms requires a driver with big BL which means a big magnet. Moving the coil in this big BL requires more electrical current (W = R*I*I where R is 4 ohms nominal for the car) which means big amps (W = V*I where V is 12V nominal).

I hope this helps. Tried to stay out of the really technical details so there are a lot of assumptions and generalizations. There are always exceptions that prove the rule.
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Old 13th July 2005, 12:58   #78
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ntomer, 52W is probably at 10% distortion. check figures at 0.1%/20-20kHz. My guess it would be about 12W rms/ch. Even at 1% which is high it would be about 25W rms but trust me 1% THD is not what you want to hear. THD= Total Harmonic Distortion, IM is InterModulation distorion. Explanations for these here would get me thrown out of this forum.

If your 6" has a sensitivity of more than 90db/1W/0.5m and your listening tastes are not loud you HU should work.

However even a small amp like Sony's 504 (about rs. 5000) will do a better job than the amp in your HU.
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Old 13th July 2005, 13:02   #79
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[quote=Sam Kapasi I'm sure Navin will agree with me here. (for a change )[/QUOTE]

when did i disagree. :-) you are younger, stronger and got better hair. I'd better agree. right :-) he he he
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Old 13th July 2005, 13:02   #80
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The 6" triax and components he's talking about have a sensitivity of 90dB
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Old 13th July 2005, 13:06   #81
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at 90db/1W he should manage 100db at 400Hz nominal. at 50Hz thanks to Xmax limiations there might be a drop in level. what is the Xmax of the midbass? Preferably linear one way. He'd need 4mm+ linear one way or 8mm+ lineat 2 way or 16mm total max Max. 16mm is 2/3". quite a bit.

however once the seats etc. start damping the sound the real SPL will be closer to 93-95db. loud enough for some purposes. where outboard amplifers really seem to help is also in LF control. Now I am afraid to go into things such as damping factor, S/N ratio, etc.. here. These terms have to properly defined or they breed more confusion.

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Old 13th July 2005, 13:14   #82
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You know Navin, sometimes you might end up scaring people away from Audio itself.
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Old 13th July 2005, 13:33   #83
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It's either me or the mobile Boom boxes you see. I'd like to feel I am scarier.

You should be blessed tape is no more. So many topics such as S/N ratio and gap width of tape heads, Dolby tracking, etc... are invalid today. Think how scary I would be then!
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Old 13th July 2005, 13:34   #84
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BTW, I have not ever worked for any audio company nor own or have ever owned any shares in any nor am affiliated or ever was affiliated in any way with any.
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Old 13th July 2005, 14:05   #85
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A question related to amps: if you are not using a high volume, does having an external amplifier help?
As far as I understand, ext amps come in handy as the HU amps start to clip fairly early. Now for the same (moderate) volume levels, how much difference in sound quality would a system with and without the external amp have?
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Old 13th July 2005, 14:21   #86
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Thank you guys for not being so technical. but most of it was still greek to me :-( Mohit had already asked what i intended to. I will primarily be listening at lower volumes - will the amp make a diff even then.

\N
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Old 13th July 2005, 14:26   #87
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Quote:
Originally Posted by navin
BTW, I have not ever worked for any audio company nor own or have ever owned any shares in any nor am affiliated or ever was affiliated in any way with any.
I am! heh heh heh

Was, am and always will be. Give me audio or make me jobless for life!!
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Old 13th July 2005, 14:29   #88
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Quote:
Originally Posted by mohit
A question related to amps: if you are not using a high volume, does having an external amplifier help?
As far as I understand, ext amps come in handy as the HU amps start to clip fairly early. Now for the same (moderate) volume levels, how much difference in sound quality would a system with and without the external amp have?
Truly speaking, at low levels there is a difference, but it's not justifiable. Navin will prolly tell you why

You are bang on about the clipping, but clipping occurs at high levels when high current drives are required.
If your system has no subwoofer, and you listen to music at fairly low levels, don't buy a amp.
There you have it.
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Old 13th July 2005, 14:59   #89
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ntomer, mohit,
before i start let me know know if this gets too technical. If it does please accept my appologies and scream so Sam can re-word things.

1. in a HU you got the laser, the DAC, and a host of other components. many of these components are low signal and hence very senstive to noise and may even generate some small ammount of noise.

2. in a HU the designed has very limited space for an amplifer. Even further there is limited space for the heat generated by the amplifer to dissappate and to compound all this the laser and DAC are sensitive to this heat.

3. Amplifers in HUs are often asked to share the same power supply as the DAC, laser, etc... in fact I have not yet come across an HU that has multiple dedicated power supplies. There is no room.

Given these constraints amplifiers in HUs need to be insensitive, must generate heat (low power), must be rugged, and occupy almost no space. The best of these amps are from the STK series of single chip amps. These amps while offering a solution are limited in many other factors (damping factor, S/N ratio, distortion particularly IM (which is why few car audio HUs state IM figures), linearity).

A dedicated power amp which can use it's entire casing as a heat sink, have it's own dedicated SMPS (switched mode power supply), can incorporate filters and protection circuits etc.. will offer better coupling between the amplifer and the speaker.

These amplifers are better able to control the speaker at ANY level and hence you should notice the difference. What you will notice is tighter bass (which meght feel like less bass but please dont confuse quality with quantity) and sort of unrestrained quality to the sound. I would urge you to ABX this so you are convinced. Remember since 1986 I have not used an HU with an amp.

Current Alpine HUs allow you to swtich the internal amp off and hence the HUs power supply can dedicate itself to the laser, DAC, etc...

Lastly, most of us want cars with 100bhp+ yet living in Mumbai, Delhi, Calcutta and Bangalore do we really need this power all the time except maybe to get from 0-30kmph a bit faster. Same analogy.
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Old 13th July 2005, 20:59   #90
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Hi Guys, I have some more questions... as always. I am trying to buy a system for my Swift. As far as my understanding is now, that in order to run the front and rear speakers through an amplifier (4ch) we need a head unit with 3 pre outs (3 pairs). Now I have a choice between Sony HU CDX-F7700 for 10.5k without bill and Pioneer 6700M for 7.8 k. Now I really like the Sony HU but it has only 2 pre outs of 4 v each as opposed to pioneer which has 3 pre outs with 2.2v each. Since I am going in for an amplifier should I go for a Pioneer with 3 preouts?

Secondaly I have some questions about the speakers. I have decided to go for 6" components at the front, and 6" JBL triaxials at the back. Now for the component system I have a choice between Sony XS-GS160 4.5k with bill or JBL that Sam recommended from Elegant Car Accesories in Lajpat Nagar for 5-6k. However I dont get a bill for the JBL. On the other hand the Sony components dont even have a crossover, and the high end ones are expensive, more than 10k. So which Component should I go for?

Lastly, if using a 4 channel amplifier for my 4 speakers, where will I plug my subwoofer? Will it be parallely connected to the rear speakers like we do in 2 channel amps to drive the rear speakers and the woofer? Please help clear my doubts.

Also is there a nice head unit with DVD or VCD capabilities and good display as well under 12k?

Last edited by aseem : 13th July 2005 at 21:01.
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