Parallel TDA2052 vs Parallel LM3886 for subwoofer

[goldyrathore]

I am thinking of parallelling 4 TDA2052 to drive an 8" sub kinda driver.
The driver has a 2 ohm nominal impedance so each chip actually 'sees' 8ohm.
The expected max power is 100 watts.
Given that ST mentions output of 28watts (@0.01 %distortion) with 25 volts supply into 8 Ohm load, total power of over 100watts is available.
http://www.st.com/stonline/products/...re/ds/1585.pdf


The following are the reasons to choose TDA2052 :-
a) I can then use a longer, slimmer (less depth) heatsink and distribute the chips along the length. This way the amps can be mounted outside, on the rear of sub cabinets without protruding much into the room.
b) 2052 is cheaper than 3886.
c) Slimmer heatsinks are cheaper than the ones required for LM3886 contributing to the cost difference even more.

What are the other pros and cons of not using proven chips like 3886 for this application?
Specifically, is it sonically inferior to a parallel LM3886.

Thanks in advance,
Goldy

[pacificblue]

a) With the same output power and the same load, you will need similar heatsink sizes. Sharing the heat across more ICs helps a bit, but the TDA is smaller, therefore can dissipate less heat per IC. You will end up with more or less the same heatsink for two LMs as for four TDAs.

The TDA2052 is sonically inferior to the LM3886, but in a subwoofer application that makes little difference. The human ear is not so sensitive in that frequency range, so the price could indeed be the decisive factor.

[goldyrathore]

Originally Posted by pacificblue

a) With the same output power and the same load, you will need similar heatsink sizes. Sharing the heat across more ICs helps a bit.

Yes, This is one of the benefits.

Originally Posted by pacificblue

but the TDA is smaller, therefore can dissipate less heat per IC. You will end up with more or less the same heatsink for two LMs as for four TDAs.

Yes, this is another benefit. With 2 LM3886 chips (for 100 watts), I guess a deep heatsink, cubish shaped one, would be required.
With 4 TDAs, each one disspates less (25 watts each for same 100 watts total output) and a slimmer heatsink would do the job. Slimmer heatsinks are easier to find and cost less for the same weight.

Originally Posted by pacificblue

The TDA2052 is sonically inferior to the LM3886, but in a subwoofer application that makes little difference. The human ear is not so sensitive in that frequency range, so the price could indeed be the decisive factor.

I will cross over to subs at about 200hz-250hz, use the system at moderate volume and have total of four 8" drivers to do the job.
Will the sonic compromise be noticable?
Thanks

[pacificblue]

Originally Posted by goldyrathore

Yes, this is another benefit. With 2 LM3886 chips (for 100 watts), I guess a deep heatsink, cubish shaped one, would be required.
With 4 TDAs, each one disspates less (25 watts each for same 100 watts total output) and a slimmer heatsink would do the job. Slimmer heatsinks are easier to find and cost less for the same weight.

It is actually the other way round. The heat dissipation is the same, but the TDA, being smaller cannot get rid of the heat as good as the LM. You will need pretty much the same heatsink for both configurations.

With four woofers it could be better to use one amplifier per woofer or one per two woofers. That way you don't need to match the feedback resistors to 0,1% and you can save the load sharing resistors, too.

Originally Posted by goldyrathore

Will the sonic compromise be noticable?
Thanks

Depends on the quality of the woofer. 200-250 Hz is quite high for a subwoofer. It will already reproduce human voices, which could reveal the shortcomings of the TDAs.
And you will be able to locate sounds coming from the subwoofer instead of from the main speakers. To avoid any locatability, the crossing frequency should be 80 Hz or less and the filter should be steep with 18 dB/octave or more. If the subwoofer is placed between the main speakers you can go up with the frequency to 120 Hz, even a bit more, if the woofer is at the exact center between the main speakers.
With frequencies as low as that, the difference between the ICs won't matter so much.

[vivmustru]

I am glad to find your site - now I know what a good one looks like.
Very good topic to share with us. Great info.

[star882]

At that power level, a hybrid or pure digital makes a lot of sense.

[sangram]

Two TDA 7294s will do the same job, and cost a lot less than the 3886. They sound acceptable, and are (were) readily available in your city at not very outrageous prices.

PB is right, the heatsink will be exactly the same for both. I use a locally available cheap extrusion (~Rs 100/6inches) for chip amps, and 6" is pretty much enough for a LM3886 parallel pair or a LM4780 running off 30V (which is about right for a driver that looks like 4 ohms). Higher voltages will mean larger heatsinks and the possibility of failure.

If you are paralleling 8 ohm drivers, it may make more sense to run individual drivers in series/parallel off single chips, you will eliminate the waste heat in the output resistor, as well as additional heat from the balancing currents. A TDA 7294 or LM3886 will run a 4 ohm load of two 8" 8 ohm drivers just fine.

If you are *not* planning an El-Pipe-O, I would just stick the money into a single large subwoofer driver. The Lab12 is available from the Chennai distributor, and is a pretty capable driver even for home use.

200Hz is too high for a sub. Even at 150Hz with the sub below my feet, it does not integrate correctly, but it's a gaming system so it's fine. I would think a maximum of 100Hz is where a sub should go to, maybe even 80Hz if the mains can take it.

[goldyrathore]

Thanks for your inputs.

Originally Posted by pacificblue

Depends on the quality of the woofer. 200-250 Hz is quite high for a subwoofer.

The woofers go quite well above 700hz. I plan to use plenty of them (2 per side, totalling four) for subwoofer duty.
They are very good designs, Xmax of 11 mm. Power handling of 100 watts RMS.

Originally Posted by pacificblue

It will already reproduce human voices, which could reveal the shortcomings of the TDAs. Does'nt fourth order crossover help to get 250 Hz crossover.

I have a line of 2" mids that cannot go lower than 200hz-250hz. I really need to do a test to figure out the exact xover frequency.

Originally Posted by pacificblue

And you will be able to locate sounds coming from the subwoofer instead of from the main speakers.

I have the woofers right next to front towers. I saw maggies being crossed to a woofer close to the ground at about 450Hz.

Originally Posted by pacificblue

With frequencies as low as that, the difference between the ICs won't matter so much.

Do you mean to say, If I cross about 200hz, then TDA must not be used. If the difference is audible then I prefer LM3886.

Originally Posted by sangram

Two TDA 7294s will do the same job, and cost a lot less than the 3886. They sound acceptable, and are (were) readily available in your city at not very outrageous prices.

My woofers are 2 ohms each. Though TDA 7294 is readily available as an assembled kit but cannot be paralleled

Originally Posted by sangram

The Lab12 is available from the Chennai distributor.

I already have the woofers in my hand.

Originally Posted by sangram

Even at 150Hz with the sub below my feet, it does not integrate correctly.
I have two boxes, each placed next to the fronts. Each box has two 8" woofers.

As mentioned above , I saw maggies being crossed to a woofer close to the ground at about 450Hz.
I added another woofer (on each side) just to negate the ground reflection problem.

[sangram]

Paralleling requires a few ballast resistors. It doesn't matter which amp it is, though for non-matched gains you will have some extra current being drawn at idle and the chips will run warmer than usual.

If you have 2 ohm woofers and 4 of them, I would run them as sets of 2 in series per channel, place the woofers near/under the mids and face them forward. This way you have a 4 ohm bass driver with a single TDA 7294/3886/xxxx. The other TDA option you are considering will also work this way.

[star882]

Originally Posted by sangram

Paralleling requires a few ballast resistors. It doesn't matter which amp it is, though for non-matched gains you will have some extra current being drawn at idle and the chips will run warmer than usual.

That is true for bipolar outputs, but MOSFET outputs self balance. You do need to synchronize the output drive signals, of course.

Here's a hybrid that would work well for your application:
http://focus.ti.com/docs/prod/folder...t/tas5630.html
You'll have to run it in single channel BTL for a 2 ohm load.