[navin]

Originally Posted by DerAlte

Clip-ji, have a look at this YouTube - How To Fiberglass #4 * Mold Making * Ed Norris.

There are more such videos on YouTube. Navin had already talked about the resin stuff. We only have to figure out where to get the preparatory gels and sprays. (You might need permission from your wife to use the electric beater, though )

actually somewhere on dynamat's website there is a step by step instruction of making a woofer box. the PVA step is an important step if you want to use detact the fiberglass from the mould.

[RAC]

Hi. I am a little confused on the pre-outs on a HU. Can you please clarify.

What can 2 or 3 pre-outs do? Not the definition but if you can also mention the use in a simple setup:

2 pre-out > 2/4 channel amp > can 2 amps be connected > how many pairs of speakers/sub can be powered

3 pre-out > 2/4 channel amp > can 2 amps be connected > I assume 2 pairs of speakers and a sub can be powered

[navin]

Originally Posted by RAC

Hi. I am a little confused on the pre-outs on a HU. Can you please clarify.

What can 2 or 3 pre-outs do? Not the definition but if you can also mention the use in a simple setup:

2 pre-out > 2/4 channel amp > can 2 amps be connected > how many pairs of speakers/sub can be powered

3 pre-out > 2/4 channel amp > can 2 amps be connected > I assume 2 pairs of speakers and a sub can be powered

2 pre out - front and rear, and often one pre out can be used for a sub (via a LPF).

3 pre out - front, rear and sub controls.

[montyguru]

Originally Posted by RAC

Hi. I am a little confused on the pre-outs on a HU. Can you please clarify.

What can 2 or 3 pre-outs do? Not the definition but if you can also mention the use in a simple setup:

2 pre-out > 2/4 channel amp > can 2 amps be connected > how many pairs of speakers/sub can be powered

3 pre-out > 2/4 channel amp > can 2 amps be connected > I assume 2 pairs of speakers and a sub can be powered

stereo sound outputs are in two channels - left and right. one pre-out has one L and one R output. these are basically line outputs which through RC wires directly go to the external amp. a line output is a clean output that doesn't go through the HUs internal amp circuitry.

2 pre-outs allow you to separately control the front speakers and the rear speakers, or the front speakers and subwoofer (where subwoofer is connected to the rear) (you can use the hi-pass low-pass settings on the external amp and get good results with this HU)

in a 3 pre-out head unit, the 3rd pre-out is usually a dedicated subwoofer output. this is better if you want to have a four speaker amplified setup with speakers in front and rear, and a separate subwoofer. it allows you more flexibility with a direct control of the subwoofer volume and in many good HUs will have a low pass crossover in the head unit itself.

you can use one pre-out for one amp. you can use two pre-outs for one 4 channel amp for front and rear speakers, or any one pair of speakers and one subwoofer. you can use 3 pre-outs on a 6 channel amp or a 4 channel amp and one mono amp. or even directly use the 3rd pre-out for subwoofer in a 4 channel amp and one of the any other two pre-outs for front or rear speakers.

regards number of amps being able to use... there are advanced setups which use one mono amp for one channel - say left, another mono amp for another channel - right - so 2 amps for only one pre-out. and two more for the 2nd pre-out for subwoofers. :-)

hope this helped.

[nishantgandhi]

I have a couple of questions:
1. What does an MDF board look like? Can someone please post a pic?

2. Is it wooden/fibre/plastic?

3. What are its advantages over factory fitted rear parcel tray?

4. An installer once told me that MDF (wooden) tray is not good because if it is not hinged properly, it makes terrible rattling noises when going over potholes/speedbreakes. Is that true?

5. When fitting the front speakers in doors, is it advisable to retain the speaker grill? I know some installers prefer to do away with grill and instead utilize the factory provided door speaker grill. Isnt that prone to catching more dust and/or letting in water etc in the speaker?

6. What difference do cables make in installation and listening?

Thanks in advance.

- N

[DerAlte]

Originally Posted by nishantgandhi

1. What does an MDF board look like? Can someone please post a pic?

Plenty of pics around - look at the install pics in the Sound off and Show off section. Light brownish pink in color. Look at the pics of subwoofer boxes being made.

Originally Posted by nishantgandhi

2. Is it wooden/fibre/plastic?

It is reconstituted wood held together with phenolic resin.

Originally Posted by nishantgandhi

3. What are its advantages over factory fitted rear parcel tray?

MDF is higher density and much heavier, so it does not resonate or vibrate along with the speaker. OE FRP parcel trays are lighter and thinner.

Originally Posted by nishantgandhi

4. An installer once told me that MDF (wooden) tray is not good because if it is not hinged properly, it makes terrible rattling noises when going over potholes/speedbreakes. Is that true?

Sure, can happen, but only if it is not seated and fixed properly. It is not because of hinging, but not fastening down properly.

Originally Posted by nishantgandhi

5. When fitting the front speakers in doors, is it advisable to retain the speaker grill? I know some installers prefer to do away with grill and instead utilize the factory provided door speaker grill. Isnt that prone to catching more dust and/or letting in water etc in the speaker?

Not really. The new speaker grill is purely cosmetic as compared to the OE grill. Some like the OE look, some the bling of the one that comes with the speaker. OE grill is a bit better for protection against water. Your choice.

Originally Posted by nishantgandhi

6. What difference do cables make in installation and listening?

A LOT! Read what Gunbir and others have written on the subject in the forum. Signal (RCA) and speaker cables can make or mar a good system.

[s0uljah]

Originally Posted by nishantgandhi

What does an MDF board look like? Can someone please post a pic?

Originally Posted by nishantgandhi

What difference do cables make in installation and listening?

The difference of a 30RS Battery Acid and a Single Malt.

See what the yeti has to say :
http://www.team-bhp.com/forum/produc...tml#post384355
http://www.team-bhp.com/forum/diy-do...ick-wires.html

[madbullram]

What is a HLCD speaker? and What the advantage compared to regular ones?

I hear that they are good in SQ and staging is brillant with this type but are not quite natural sounding....

Are these expensive?

[low_bass_makker]

Originally Posted by madbullram

What is a HLCD speaker? and What the advantage compared to regular ones?

I hear that they are good in SQ and staging is brillant with this type but are not quite natural sounding....

Are these expensive?

HLCD are Horn Loaded Compression Driver.

I have in my car will try posting pics of the same. The advantage is that they need very little power to play loud enough. Also they have very fast transients. One would need very powerful and fast midbass to accompany them. They give very good stage with a perfect center but the stage would not be wide enough. Few horns have a peak at some freq but not all are similar sounding. And yes they are expensive affair. About 50k a pair.

A more detail write up...

EliteCarAudio.com : Your one stop resource for mobile audio and electronics on the net.

[madbullram]

Thanks LBM. So will this sound more brighter?

[low_bass_makker]

Originally Posted by madbullram

Thanks LBM. So will this sound more brighter?

It depends a lot on the tunning. One might fiddle a lot with EQ to get the result. And it is bright or not totally depends on user taste.

[BaCkSeAtDrIVeR]

Question 1.

actually, an HU can be described to be having 8 small amps internally bridged to make 4 channels. so each channel can be described as a bridged amp.

The above was posted on http://www.team-bhp.com/forum/ask-gu...r-works-2.html

What I want to know is, what is the concept of "bridging" in the above quote?

Question 2.

Crossover - the concept of separating output from a HU / amp into bass, midrange, etc, is done by a filtering mechanism, right? And this filtering mechanism is usually a copper coil, right?

Question 3.

How does a HU/ Amp drive a speaker? Constant voltage with varying output current? Or constant current, varying voltage?

Question 4.

Why is nobody speaking of "impedance matching" here? I am absolutely noobie to theoretical electronics; but I have read that devices / circuits should have matching "impedances" - like a 4 ohm impedance output should be connected to speakers with 4ohm impedeance, etc. Hence, my understanding was that we need to look at output power of the sound source (HU/amp), and also its impedance, and find speaker(s) of matching power AND impedance.

PS:- Off for a couple of days - so please do not any responses from me till saturday.

[greenhorn]

Originally Posted by BaCkSeAtDrIVeR

Question 1.



The above was posted on http://www.team-bhp.com/forum/ask-gu...r-works-2.html

What I want to know is, what is the concept of "bridging" in the above quote?

normally, in an amp, the amplified signal comes on one of the the terminals , and the other terminals remains at 0V ( ground). so at a supply voltage of 12V, the peak of the sine wave will be at the maximum, + or - 6V (other terminal being at 0V. when you bridge an amplifier, you take a second amplifier , and give it the inverted signal ( so when amp # 1 is at +6v, amp # 2 is at -6V, and since the speaker is connected between these 2 outputs , total difference is +6 - (-6) = 12V, so you get more power

this picture should explain it better

picture taken from here Lenard Audio - Education - Amplifiers. go through it if you have lots of time and are curious. Link courtesy Navin

Question 2.

Crossover - the concept of separating output from a HU / amp into bass, midrange, etc, is done by a filtering mechanism, right? And this filtering mechanism is usually a copper coil, right?

in the HU, the filtering can be done electronically. In the crossovers of speakers , copper coils(inductors) , as well as resistors and capacitors are used.
very simply put , the coils block high frequencies , and pass low frequencies
so usually you will find them in series with the mid bass to remove the high frequencies. You might also find them in parallel with a tweeter because it makes the low frequency signals pass through it instead of the tweeter.

a capacitor does the exact opposite, they pass HF , and block LF. so you'll find them in series with tweeters , and in parallel with woofers.

Resistors are used to attenuate the signal, and sometimes in conjunction with the inductors /capacitors to set the cutoff frequency of the filter

Question 3.

How does a HU/ Amp drive a speaker? Constant voltage with varying output current? Or constant current, varying voltage?

neither. the output voltage will vary according to the input signal, and assuming the load to be resistive, the current will also vary the same way according to the formula I = V/R , where I = current , V= voltage, R = resistance.

Question 4.

Why is nobody speaking of "impedance matching" here? I am absolutely noobie to theoretical electronics; but I have read that devices / circuits should have matching "impedances" - like a 4 ohm impedance output should be connected to speakers with 4ohm impedeance, etc. Hence, my understanding was that we need to look at output power of the sound source (HU/amp), and also its impedance, and find speaker(s) of matching power AND impedance.

impedance matching is critical only for things like transmission lines. according to the basic circuit theory, maximum power is transferred when load impedance = source impedance. But we're not interested in maximum power transfer. we want faithful reproduction of music. so what we need is the output impedance of the amplifier to be as low as possible . the lower the better( an internal resistance of 4 ohms could play havoc with speaker crossovers designed with the speaker impedance alone in mind) usually the output impedance is in the region of a fraction of an ohm, as opposed to 4 ohms for the speakers.

[mithun]

In Pioneer HUs, I've came across an setting called COMP(compression) that helps to adjust the playback quality. What's the utility of this setting ?

[raj_5004]

Originally Posted by jkdas

What is compo?
Shrt form for component. A component set is a set of speakers where you get 2 mid woofers (generally 5.25" or 6"), a crossover network and a pair of tweeters. These sound very nice in the front of your car.
What is co-ax?
sounds like co-axial, but again, co-axial what.. cable?
Co-Axial means speakers with a common axis. For example, regular car speakers have a woofer, midrange and tweeter built all on the same axis.

this thread is the best in T-BHP.
here are my few doubts:

1) in the component set, as explained by das, you get two set of speakers- the woofers are installed in the door panels and the tweeters are installed near the A pillar... am i right?

2) co axial houses all these in a single unit, that is in the door panel itself. so which are better, component or co-axial?

3) also, it is mentioned that component speakers are the best for front, so are co-axials for rear?