Re: Surround Sound Question

st10r wrote:
> After doing 2 days of reading on how to get my surround sound to work on
> my Zalman 5.1 surround sound headset, I finally got something out of it.
> After doing multiple installs and uninstalls of different version of the
> card, I get sound all around my headset when I do a sound test on the
> Sound Effect Manager. My card is a Realtek AC97 onboard.. the only
> problem is, when I do the test, anything I hear behind me is reeeeeally
> quiet, barely hearable.. this is a SS of my volume control settings
> http://i38.photobucket.com/albums/e1...-/asdasd-1.jpg
> When I set my "Front" volume to low, I can barely hear anything.. also,
> my Center does not seem to work at all.. My Zalman headset has 4 wires,
> 1 for mic, 1 for Rear, 1 for Side and 1 for Center.. Help much
> appreciated! :normal:
>

I looked at a couple reviews. One mentioned the use of non-standard colors
for the plugs on the cable. The plugs have a letter on each one, labeling
what jack it is for.

http://reviews.pcapex.com/audio_hard...headphones.php

The front and back are four 16 ohm channels. The center speakers, in order
to have a centered image, are wired in series. So, they present a load of
32 ohms, and less power will come from the center speakers as a result.

+ - + -
Center ---------- center_left ------- center_right --------+ My best guess
16 ohms 16 ohms | on how the
Sub ---/ | Center/Sub
| plug is
GND ----------------------------------------------------+ wired

The center/sub plug, on a 5.1 card, would have the center signal on one contact,
and the sub-woofer signal on the second contact (the third is ground). The
headphones have no "sub", and strictly speaking, that means the headphones
are not 5.1. It makes them "5.0". That will screw up the sound distribution,
in the sense that the sound driver is going to send more of the sub-bass
signal content, to the contact that isn't connected to anything. There will
be a mismatch between the acoustic model the sound driver for the RealTek uses,
versus the actuality of the headphones. (To work correctly, more of the
sub-bass energy, would have to be redistributed to the other five
channels.)

OK, so the other issue is the nature of headphones. Headphones are non-amplified
devices, versus "computer speakers" which have their own built-in amplifier.
The headphones are connecting a 16 ohm load to four of the channels, and a
32 ohm load to the fifth (center) channel.

Now, it turns out, that the earlier AC'97 5.1 motherboard audio chips, tended
to have "strong" drive (suitable for 32 ohm headphones) on the front channels
only. The other four channels had "weak" drive. If you examine a datasheet and
application note, that choice helps keep the chip cool, and allows the
motherboard designer to use a puny 5V regulator to make clean analog
power for the chip. It also means, if you were to take three ordinary
stereo headphones, and plug them into front, rear, and center/sub jacks,
that only one set of headphones would be loud, while the other two would
be almost inaudible.

It is possible, that other sound devices, like a PCI sound card, may have
strong drive on all channels, but you'd really want to check the specs
carefully, to avoid wasting money. I think that some of the more recent
motherboard HDaudio chips, may have amplifier capability per channel
(although the stinking drivers may prevent you from turning six of them
on at the same time - and the HDaudio datasheets now are virtually unreadable,
so I don't know if they're concerned about using six of them at once or not).

This is the product page at Zalman for ZM-RS6F. The ZM-RS6F-M version includes
a microphone, but I suspect would be otherwise identical. Power level is
listed as "0.02W" with max at "0.15W". If the computer front (strong)
output could deliver 1.0 volt into 16 ohms, that would be (1.0*1.0)/16 = 0.0625W
of power. Roughly the geometric mean, between 0.02 and 0.15W, meaning
the headphones should not need a lot more drive than a 1 volt level.

http://www.zalman.co.kr/ENG/product/...ad.asp?idx=213

If only your "front" output signal is strong, you'll need an amplifier,
to present a lower output impedance to the load for the weak channels.
Naturally, Zalman makes such a product. An amplifier like this, will change
the output impedance on the weak channels, making them into strong ones.
To get the specs, you can download the manual on this page.

http://www.zalman.co.kr/ENG/product/...ad.asp?idx=212

What that amplifier will do, is not change the volume level of your
loudest channel. But it should fix the weak channels. If you don't
think the loudest current channel is loud enough, then that amplifier
may not be good enough. And maybe a sound card is cheaper than the
amplifier anyway.

This is an example of headphones that include an in-line amplifier.
So these guys had half a clue as to how to interface to an average computer.
The in-line amplifier is powered from a wall wart (so no batteries to
deal with).

http://www.turtlebeach.com/products/...hatdoiget.aspx

Also, Zalman has a USB version of their headphones - that would
solve the volume problem (as the USB chip in the Zalman USB headphones,
would be responsible for driving the loads), but then you'd have
to deal with the USB driver. For example, would a USB sound
driver support EAX1 or EAX2 for gaming ? I don't know the
answer to that.

Loads of fun, and the odd pitfall.

HTH,
Paul

st10r wrote:
> I tried messing around with the cording and plugging it in in different
> holes to get a better sound but it did not help at all. So what your
> sayin is my 2 options are a new sound card or the amplifier?
>

That is my best guess.

What I'd try, is first take the "front" plug of the Zalman headset, and
try it in the "front", "rear", and "center/sub" jacks. I'm assuming the
sound control panel will allow you to stay in 5.1 mode while doing that.
Listen to the volume level of each jack. Using the same volume slider
settings for all three tests, is the "front" jack the only one with an
acceptable level ? If so, you need an amplifier of some sort, for the
rear and center signals.

You can also test the headset itself. Use the green audio jack on the
computer. Now, in turn, try the "front" plug, the "rear" plug, and the
"center/sub" plug in the green jack. Does each one give decent
levels ? I would expect the response of the center to be reduced, due
to its series wiring. If all three give good levels, then the headphones
are functional.

I'm not certain at this point, that finding a sound card with strong output
on all three jacks, will be that easy. The reason a sound card won't
include that kind of amplification, is it degrades noise performance,
and can also increase product cost.

The Zalman ZM-RSA amplifier, is in the $100 range. And anything
that involves sound, always has a nice profit margin, so I
don't know if you'll be able to do much better than that on
six channels of amplification that can drive 16 ohm loads.
A Walkman amplifier I was looking at, was about $25 for two
channels, and you'd need three of those (and that thing didn't
include a power source).

For $55, you can get the Zalman ZM-RSSC USB 5.1 sound device. It
uses a Sonix.com.tw chip, and based on the figure here, appears
to be able to drive their headphones. Apparently, for the
Zalman 5.1 headphones that have a USB interface, they used a
different chip for that one (a CMedia chip). So this is a little
bit cheaper than the amp (but I still might want to find a review
or something).

http://www.zalman.co.kr/ENG/product/...ad.asp?idx=211

HTH,
Paul