Need advice on attenuating a Samsung home cinema system

[moog10538]

I've got a Samsung HT-C5500 blu-ray 5.1 system. The subwoofer is excessively loud, even at full contrast (sub at -6 dB, others at +6 dB -- the maximum settings the firmware will allow). It's an all-in-one player/amp so my only access to the sub signal is at its speaker connection.

I am considering fitting a passive power attenuator to the subwoofer speaker to reduce the problem. However, I did my elecronics training 20 years ago but specialised in microprocessor systems -- my analogue electronics knowledge is very poor.

I've looked into a couple of bridged-T and resistor matrix circuits but I'm feeling out of my depth.

I'd be grateful for any advice on choice of circuit designs, or on cheap ready-built solutions. Can anybody help?

Amplifier subwoofer output: 170W (3R)
Subwoofer: impedance 3R, range 40-160Hz; 80 dB/W/M; rated 170W, max 340W.

[Cokewithlime]

My immediate thought would be that the issue is more the placement of the actual sub within your room. For instance if the sub is located in a corner of the room you will get a lot of LF "room gain" or that the current position of the sub is exciting a resonant room mode.

The no cost and simple thing is to just move the sub to a couple of different positions in the room and listen for a while at each location, pick the location that sound the best to you.

You may find that this approach solves the issue for you.

[NEO Dan]

Check for "loudness or dynamic range enhancement" type crap to turn off...

[MarcelvdG]

If the suggestions of Cokewithlime and NEO Dan don't help enough, you could do the following:

-Connect a 1 ohm resistor in parallel with the subwoofer

-Connect a 2.2 ohm resistor in series with the parallel connection of 1 ohm and subwoofer

This will reduce the subwoofer level by about 11.9 dB.

There are two problems with this: you need very high power rating resistors if you ever drive the subwoofer amplifier anywhere near its maximum power and the damping of the subwoofer resonances will be reduced because it is driven from a 2.2 ohm//1 ohm=0.6875 ohm resistance rather than nearly 0 ohm.

The required power for the 2.2 ohm resistor is 129 W if you drive the amplifier to its maximum for a prolonged period of time, and for the 1 ohm it is 33 W. Wirewound resistors such high power ratings are hard to get.

One way around this is to connect a number of resistors in parallel and an equal number of parallel connections in series. For example, if you have 16 resistors of 2.2 ohm, 10 W, you can make four groups of four parallel resistors and connect those in series. The whole thing is then a 2.2 ohm, 160 W resistor.

[ßart West-VL.]

MarcelvdG,

I once read that, with such an arrangement, the sub would play lower because of the added series resistance, can you comment on that please?

[epa]

or use this ,wich does the same as marcelvdg sugested but with adjusteble attenuation.
its called "l-pad"

[MarcelvdG]

Originally Posted by ßart West-VL.

MarcelvdG,

I once read that, with such an arrangement, the sub would play lower because of the added series resistance, can you comment on that please?

In the circuit I suggested both the series and the parallel resistor help to reduce the sound level that comes from the subwoofer. The amplifier delivers the same power as it normally does, but 93.5 % of it is turned into heat by the resistors and only the remaining 6.5 % goes into the subwoofer.

The advantage of using both series and parallel resistors rather than only a series resistor is that it keeps the resistance that drives the subwoofer as low as possible, which minimises the response peaks you get due to subwoofer impedance peaks.

By the way, using only a parallel resistor is not possible, this would only overload the amplifier.

[moog10538]

Wow -- thanks for the responses! Much appreciated.

The SW is currently located in a corner, so I'll try out Cokewithlime's suggestion first. (I'd presumed too much on the directionless nature of bass; resonance hadn't even occurred to me.)

Many thanks for the tips, MarcelvdG & epa. I had imagined that tapping off a voltage divider would involve hefty resistors, but I'm not driving it anywhere near maximum so I should be able to compromise if re-positioning fails.

(NEO Dan -- I had tried toggling the dynamic range control option but it didn't alter the overall bass problem. I've also disabled the DSP function. For some bizarre reason Samsung also offer an option to listen to everything with church hall reverb if I wish -- why anybody would want this I'll never know!)

Once again, many thanks.