[keroo1099]

Originally Posted by sandeepmohan

I am not so sure if porting a box fitted with a car loudspeaker will add any gains at all. You generally port the box to increase bass. That driver is hardly ever going to move. My idea of filling the box up with acoustic material was to tighten bass, which is limited from a driver of that size. In its current state, its going to ring, produce a hollow bass response.

+1 to this.

Enclosure design is an art and you need to know a lot of parameters to get it right. Just cutting a hole and sticking a port is going to be playing Russian roulette speaker style unless one knows the size and the length of the port required for the frequencies you want to reinforce. Damping and bracing the inside of the box will help tighten up the sound, but without any data its the good old trial and error method.

Putting spikes or feet under the box might also help clean up the sound.

[IP_Man]

Originally Posted by sandeepmohan

I am not so sure if porting a box fitted with a car loudspeaker will add any gains at all. You generally port the box to increase bass. That driver is hardly ever going to move. My idea of filling the box up with acoustic material was to tighten bass, which is limited from a driver of that size. In its current state, its going to ring, produce a hollow bass response.

Originally Posted by keroo1099

+1 to this.

Enclosure design is an art and you need to know a lot of parameters to get it right.

I agree to both you. Adding an acoustic material to the box will reduce internal reflections and unwanted resonance that will surely 'tighten up' base. Bass reflect port was a general idea may not suitable to this box but there are pre calculated box dimensions on net should work fine for the hobby projects. Bose has shown size don't matter for the base response. Bose sound link mini has amazing base response from the speaker that fits on your palm.

For the box shown, IMO, OP may try rear bass reflex tube as an experiment. If result is not satisfactory, it can be sealed easily.

Also, instead of filling (because it will reduce volume of the box), I suggest sticking up acoustic material on the internal walls. How about felt cloth?

[sandeepmohan]

Originally Posted by IP_Man

Bass reflect port was a general idea may not suitable to this box but there are pre calculated box dimensions on net should work fine for the hobby projects.How about felt cloth?

Yes, the port needs to be designed based on internal cabinet volume and driver specifications. It won't work with just about any driver or design. The driver needs to generate (or move) a certain volume of air inside the cabinet. In this case, a little mid range loudspeaker won't really do much, nor will adding a port help. A better way to approach a driver like this is to fabricate a port tube from directly behind the driver, with an exit in the front or back.

Its not just Bose. Sonos, Sony and several brands use bass reflex or ports as a technic to get more bass out of a compact loudspeaker enclosure. It works though it tends to exaggerate bass. Most folks like that sound and it works for selling a product.

Another design is the use of a passive radiator. Its a undriven loudspeaker pushed using the forces of the driven loudspeaker. This is mostly sealed box design. JBL's Charge series work like this. Not as much bass as ported applications. Quality bass though.

I've seen felt clot being used. I don't know if its superior (I doubt it) to acoustic Polyfill. The latter is common is loudspeaker design.

Here's an example of a Bose Wave Radio CD that I stripped apart to change the CD lens. The design dates back to 1998. It has a driver for each channel but most of the bass is handled by only the left channel. The left channel also does mid range. The driver for the left channel has a large cabinet that extends right behind the driver and further extends to the middle of the chassis, the plastic section sitting below the CD spindle. The port you see for the right speaker is the bass duct or port after it goes through their proprietary Waveguide system. The bass this thing generates is astounding for its size and age. It still works. However, you'll notice that the chambers are small, not oversized for the said driver. It obviously needs to stay compact for this design and application.

[IP_Man]

Originally Posted by sandeepmohan

Here's an example of a Bose Wave Radio CD that I stripped apart to change the CD lens. The design dates back to 1998. It has a driver for each channel but most of the bass is handled by only the left channel.

I think Bose subwoofer uses 'Transmission Line' principle and to some extend it is used in 'wave radio' and 'sound link mini'. It is different than bass reflex port and can amplify deep bass response using compact dimensions. To get same bass response from bass reflex design would require much greater volume of the speaker cabinet.

https://youtu.be/Q2VL_FHu9AY

[jkrkrish]

Originally Posted by sandeepmohan

I am not so sure if porting a box fitted with a car loudspeaker will add any gains at all. You generally port the box to increase bass. That driver is hardly ever going to move. My idea of filling the box up with acoustic material was to tighten bass, which is limited from a driver of that size. In its current state, its going to ring, produce a hollow bass response.

Sandeep I have few questions!

1. The dual speakers (photo below), how do they work?. Is there a cross-over embedded inside, nothing is visible from outside (there is a capacitor in series to the negative terminal). I could not find the design details anywhere.

2. I noticed few days ago, the smaller speaker at centre, has become loose & rotating slightly (I am afraid it might come out). And upon connecting to amplifier, the central small speaker responds, and the outer bigger one doesn't vibrate. What might have happened. Is this speaker, is it beyond repair?.

[sandeepmohan]

Originally Posted by jkrkrish

I have few questions!

This is dual concentric driver design of sorts. A common design across most loudspeakers for automobiles. You have the outer driver for bass & midrange and the center speaker mounted on a plastic housing for high frequencies. That little capacitor is pretty much the cross over, basically to separate the high and low frequency signal to each driver. It is in its basic form. Its usually a more elaborate circuit. This is done this way to keep the cost of the speaker low.

The little center speaker should not rotate or move at all. Sounds like glue has dried up due to age and its come off. Hard to say from pictures.

Its possible the wiring to the larger outer loudspeaker has come off. Could be a dry solder. Check for that. There is little that can go wrong with a speaker. Worse case, the internal speaker coil has blown and that is not so easy to fix. If you are familiar with dismantling a speaker, you can try it. Easier to replace with something from SP Road.

[keroo1099]

Originally Posted by jkrkrish

1.Is there a cross-over embedded inside, nothing is visible from outside (there is a capacitor in series to the negative terminal).

The capacitor just cuts off low frequencies from going to the tweeter which is the small unit at the center. As Sandeep has mentioned this is the most basic form of a crossover

Originally Posted by jkrkrish

2. I noticed few days ago, the smaller speaker at centre, has become loose & rotating slightly (I am afraid it might come out). And upon connecting to amplifier, the central small speaker responds, and the outer bigger one doesn't vibrate. What might have happened. Is this speaker, is it beyond repair?.

You can try contacting Mr.Murthy at Tools and Trade at the far end of Commercial Street and see if his technician can fix the speaker.

[jkrkrish]

Originally Posted by sandeepmohan

That little capacitor is pretty much the cross over, basically to separate the high and low frequency signal to each driver. It is in its basic form.

Thanks Sandeep,
When I checked with a multimeter, the capacitor reads 10microFarad in the good rear speaker, it reads few nanoFarads for this speaker. I plan to replace the capacitor & check.

[jkrkrish]

Placing a fresh capacitor for the tweeter part of the speaker didn't improve the output, and after isolating the two parts of the dual speaker, found that the outer (mid-range) is working fine, but with some static at higher volume. Giving up on this speaker.

Next project will be to use the two old Bush speakers (shown below & sound quality is okay), and connect them with a suitable (!) amplifier with bluetooth.

Thanks to all my fellow PHPians, for the comments

[jkrkrish]

Originally Posted by IP_Man

Also, please check that metal body of the car stereo is connected to DC negative.
.

I have not connected the stereo chasis to DC negative. Should there be a connection or not?. How this will help?

The AC input to the AC/DC converter I used, has three terminals (I e. with ground)

[dwarika]

I have been holding onto the head unit of an Ertiga 2020 as the OEM was upgraded to a larger unit right at the showroom when my brother purchased the car. We tried installing this to the Alto K10 but this was too large for it. The next mission was to DIY install it at home and use it as a stereo. But the challenge has been the external casing and the cabling. We could not find proper cabling for the device and its still sitting idle.

[IP_Man]

Originally Posted by jkrkrish

I have not connected the stereo chasis to DC negative. Should there be a connection or not?. How this will help?

The AC input to the AC/DC converter I used, has three terminals (I e. with ground)

As an experiment try connecting it. By doing that car stereo metal body becomes shield that stops noise reaching to sensitive pre amp circuit.

[jkrkrish]

Originally Posted by dwarika

The next mission was to DIY install it at home and use it as a stereo. But the challenge has been the external casing and the cabling. We could not find proper cabling for the device and its still sitting idle.

Not as difficult as you may be imagining. There are thousands of you tube videos on this topic. The head unit will have its rear connector with wires intact. The wire colour codes are universal. Don't worry about enclosure for the stereo, make the connections and drive the speaker.

[dwarika]

Originally Posted by jkrkrish

Not as difficult as you may be imagining. There are thousands of you tube videos on this topic. The head unit will have its rear connector with wires intact. The wire colour codes are universal. Don't worry about enclosure for the stereo, make the connections and drive the speaker.

Thanks for the heads up . I will give it a try and share my experience in here.

[jkrkrish]

Originally Posted by jkrkrish

Next project will be to use the two old Bush speakers (shown below & sound quality is okay), and connect them with a suitable (!) amplifier with bluetooth.

This project is compete. Connected a, TPA3116 2.1 50Wx2+100W Bluetooth CSR4.0 Class D Power Amplifier with Acrylic Case, purchased from site robu.in.

A good amplifier, clear sound, the only drawback being absence of auxiliary input port, and maybe shorter bluetooth range. All these boards need a ac to DC converter.