Re: Discussion on speaker upgrades on DCS (and similar) machines

On Feb 13, 5:29 pm, tbanth...@xxxxxxxxx wrote:
On Feb 13, 5:05 pm, RJBAudio <ro...@xxxxxxxxxxxx> wrote:





On Feb 13, 4:10 pm, tbanth...@xxxxxxxxx wrote:

On Feb 13, 3:41 pm, RJBAudio <ro...@xxxxxxxxxxxx> wrote:

I've read quite a few posts recently regarding speaker upgrades on
different DMD machines and I would like to discuss a few things.  I'll
first note that my other hobby involves designing high-endspeakers
(www.rjbaudio.com) so I have a bit of experience on the speaker side
of things to some degree.

I recently upgraded thespeakersin my Demo Man machine but did some
tests prior to choosing replacement drivers.  This machine uses the
DCSsound system which basically means that it has an active crossover
at around 300 Hz which splits the signal prior to amplification and
then uses one amp for the lower cabinet subwoofer driver for
frequencies below 300 Hz and another amp for the higher frequencies
that drives the backboxspeakers.  The original configuration for the
backboxspeakersuses a full range driver on the left side and a
smaller high frequency driver (filtered using a series 10uF capacitor)
on the right side (which means that there is an emphasis on high
frequencies in general because this range, approximately above 4 kHz,
is produced by bothspeakers).  So one complaint about this type of
backbox speaker configuration is that the imaging is poor due to the
fact that sounds below 4kHz only come from the left speaker.

The first thing that I did prior to ordering newspeakerswas to
disconnect the originalspeakersand run those wires to a few sets of
high-endspeakers(for the backbox speaker lines I used a pair of 2-
way bookshelfspeakersand for the subwoofer line I used a ported 6.5"
driver tuned to have an f3 of around 40 Hz).  I actually found that
the backboxspeakerswhen run to a set of fairly neutral high-end
speakerssounded a bit muffled due to a prominence in the lower
midrange.  Also, it seemed like extreme high frequencies weren't
present in the original signal.  The subwoofer speaker didn't reveal
that much more bass than the original lower cabinet woofer which made
me think that it would be a waste of time to use a driver capable of
producing very deep bass based on the assumption that the raw signal
doesn't even produce frequencies that low.

What I gathered from this experiment was that the backboxspeakers
didn't need full frequency extension all the way to 20kHz like home
stereospeakersdo, but what was most important was the frequency
balance of the drivers used so that the sound from the machine was
reproduced with a level of clarity and neutrality.  I also thought
that there would be a point of diminishing returns with going with a
subwoofer driver capable of producing very deep tones due to the
limitations of the signal sent to it.

Based on this information I learned that it is not so important to get
the highest "quality" drivers, but to choose drivers best suited to
the application to provide the right synergy.  This means choosing
backboxspeakersthat cover the 300Hz to 10kHz range well yet have a
tonal balance that reproduces the signal sent to them in a way that
preserves clarity and presents neutrality.  It can be important to
find a subwoofer driver/backbox driver combination that provides a
good balance between the levels of those drivers and this is
determined by looking at the sensitivity of the drivers involved but a
good alternative is to use an L-pad on the backbox drivers so that you
can lower their volume level relative to the subwoofer to get a bit
more impact in the bass region.  Choosing a very high sensitivity
subwoofer driver can sometimes result in a sacrifice in bass response
due to the trend that higher sensitivity drivers "tend" to have higher
resonance frequencies due to lighter cones.

Anyway, what I ended up doing with my Demo Man machine was first using
the Dayton 6.5" shielded 4 ohm woofer as a replacement for the
original subwoofer driver because I liked the fact that it fit
perfectly without any screw modifications and the Dayton drivers are a
pretty good value.  I went with a pair of HiVi B3N 3" fullrange
drivers for the back boxspeakers.  I didn't want to have to cut a
hole in my speaker mounting panel but instead made a "reducer" panel
for the left speaker.  I had used these drivers before in another
project so I knew that they sounded decent for the price and based on
distortion and frequency response tests I knew that they could cover
the 300-10kHz range well. I added a simple filter to them so that I
could adjust the tonal balance (a common baffle step filter consisitng
of an inductor in parallel with a resistor, with this configuration in
series with the drivers and adjusting the resistor allowed me to tweak
the amount of high frequency attenuation that I desired).  I liked the
fact of using two fullrange drivers which improved the imaging
significantly (all of the sounds seem like they are coming from the
middle of the machine now).  I didn't have to add an L-pad to the HiVi
drivers because they are a very low sensitivity set of drivers which
made the Dayton 6.5" woofer more prominent (but if I had just replaced
the subwoofer and used the original backboxspeakersI probably would
have found the subwoofer driver to be too quiet).

So, that's my experience with drivers in aDCSmachine.  One thing
that I would like to know for sure is the actual frequency content of
the signals sent to each driver.  I made estimates based on using
drivers that could cover frequency ranges well beyond that of the
signals but it would be nice to know based on real data, for example,
how low in frequency the bass sent to the subwoofer driver actually
goes.  I'm sure this may vary from game to game, and that would be
another neat topic regarding which machines have sound that goes the
deepest in frequency.   On a side note, I thought that it might be
interesting to use a subharmonic generator (a processor that takes
bass frequencies and generates duplicate ones an octave lower in
frequency) to artificially deepen the bass of a machine.

I'll wrap it up there but please comment.

Just so I understand your specific solution and being more of novice,
what standard filter would I buy --- got an example to point to on
Parts Express?- Hide quoted text -

- Show quoted text -

I'm assuming that you are asking about the custom baffle step
compensation filter that I designed.  This filter is not really a
requirement but I added it to tailor the sound to my liking a bit and
in hindsight, perhaps no filter at all would have provided a sound
more like the original with a bit more crispness and clarity.  There
is no prebuilt filter at Parts Express for this purpose but my filter
just used an air core inductor (I think I used 0.4mH which is a bit
low for a BSC filter but the drivers are wired in parallel which
provides a lower impedance hence a smaller inductor.... sorry if this
is confusing) and a resistor (I forget which value).  There is an
example of a design using the same drivers (HiVi B3_) at this link...http://www.zaphaudio.com/audio-speaker18.html but I didn't implement
the notch filter that he used in his design.

Anyway, I don't really think that it is that necessary to go as far as
I did with the design but the problem with picking out replacementspeakersis that it is very difficult to tell how well they are going
to work until actually installing them and listening.  But if the
sound isn't to your liking then crossover filter design knowledge can
be helpful as a means to further adjust the sound.

With all of that said, I'm assuming that you are talking about aDCS
based machine which really requires no additional filtering.  However,
earlier machines only have one full range amp and the subwoofer should
be low pass filtered (but you have to be careful how you do it because
sometimes all of the drivers are wired in series and certain types of
filters will filter more than the subwoofer driver... this is why they
usually use a capacitor in parallel with the subwoofer in this series
configuration).

So much for the short answer but let me know if you have any other
questions.- Hide quoted text -

- Show quoted text -

I have an STTNG and I want to upgrade the speakers.

For the STTNG I want to replace the woofer and utilize some extra
Onkyo SKSHT750 7.1-Channel Home Theater Speakers that I have on
speaker stands.   The height is perfect, I already own them anyway, &
they sound great on my home theater system --- so I was going to give
it a go.   They are 8 ohm speakers, so I was trying to figure out if
that would work out ok or what I else I would need to do.   I was
going to order a woofer from Parts Express.- Hide quoted text -

- Show quoted text -

In order to hook up a pair of home speakers to the DCS based machine
you'll need to desolder the wires that attach to the left speaker an
run them out of the cabinet somehow (and make sure that you don't
short them together while the machine is on because it may blow the
power amp chip). Then run that pair to the left Onkyo speaker and
then run a separate speaker wire pair to the other speaker (which puts
the two speakers in parallel, in a mono configuration). Like I said,
you may or may not hear an improvement because a lot depends on how
well the frequency response of your Onkyo speakers works with the
digital sound from the roms. The only other thing that you'll have to
worry about is the relative levels between the top speakers and the
bottom cabinet sub.
.

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