wrote in message
oups.com...

jamulc wrote:

What I'd like to know is if there's a DSP audio filter that really
makes any difference in making speech (on AM signals) more
intelligible
through DSP reduction of noise.

Best & 73,

jamulc

If greater speech intelligibility is what you want, then you should
consider one of the Clearspeech filters, especially the Clearspeech
"base unit". These aren't available new anymore, but you can find them
on ebay. In fact, one is up for auction right now:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

(I have nothing to do with this auction, do not know the seller, etc.)
I've been using one of these for several months now and I love it. I
hardly ever listen to SSB without it. It's great at reducing "white
noise" and making weak signals more intelligible. (You will not want to
use it on AM, except perhaps under very unusual circumstances.)

Steve


NCT Group offers a demo software for processing short sound files
http://www.nctclearspeech.com/cspc.htm. NCT is the developer of the Clear
Speech algorithms used in the Am-Com unit listed above and in the newer Heil
Sound NCT Group Clear Speech Speaker listed at $210 at
http://www.heilsound.com/amateur/cle...ch_speaker.htm. The latter might
have more recent algorithms than the Am-Com.

The GAP http://www.gapantenna.com/hearit.htm HEAR IT Speaker for US$149 from
W4RT http://www.w4rt.com/ is the rebranded bhi NES10-2 Noise Eliminating
Extension Speaker
(£99.95)http://www.bhinstrumentation.co.uk/h...10-2_mkii.html. The SGC
ADSP2 DSP speaker http://sgcworld.com/shopsite_sc/store/html/page4.html is
priced at $129.95, claims 26 dB noise reduction versus bhi's claim of 35 dB
and appears to have auto notch filtering.

The noise reduction numbers may be misleading if the reduction algorithms
are different. Intelligible speech is the real objective - not noise
reduction per se - and all systems will have processing artefacts that
contribute their own unique distortions. The real story can only be found
out by subjective listening tests to the same material of wide variety.

Both bhi and SGC offer before and after sound files. It's possible to
process the bhi/SGC 'before' files though the ClearSpeech-PC software and
compare the results to their 'after' files. I tried that - it's pretty messy
but I thought the bhi/GAP came out on top. Their in-line module provides
more controls than their speaker so is more 'tunable'. A ham I know says he
prefers the bhi/GAP in-line module after having tried all the DSP boxes out
there.

Tom

Les wrote:
The Timewave 599ZX is the best out there, period! Plus it has a 5000 hz
(5 khz) bandwidth. The notch, noise reduction etc . is superb. It isn't
cheap, but you get what you pay for. I have owned the various JPS, MFJ,
etc. They don't come close to the 599ZX.

I disagree about the noise reduction. The other features are nice, in particular
you get an actual frequency readout of what you're setting, but the noise reduction
is pretty old-fashioned, and makes it sound muffled.

ClearSpeech has the best noise reduction I've heard, but no other features, and
often the other features are what you want.

The Am-com ClearSpeech has no settings at all other than on-off but I use it a lot.
The Heil version I haven't figured out. It has several steps of Clear Speech
NR, which is nice, but the audio levels are all wrong, and (fatally) it cuts out
low frequencies and high frequencies whether it's bypassed or not. (The unit returned
by Heil works better than the way I got it the first time, but still is susceptible
to feedback and strange lack of line-out output. The former is undoubtedly a ground
loop in audio path via the power supply, which is an engineering mistake. The latter
may be an impedance problem but there's not enough in the manual (?) to tell. I
haven't tried to experiment with matching transformers, being discouraged by the
audio frequency loss and the feedback. So, in short, if you're not willing to fuss
with it a lot, you're not likely to be real happy except perhaps using it as a speaker
rather than a filter box.)

My solution is to get every filter and wire them in series (hence my need for a
functioning bypass). Turn on the ones you need.

--
Ron Hardin


On the internet, nobody knows you're a jerk.

Ron Hardin wrote:

Les wrote:
The Timewave 599ZX is the best out there, period! Plus it has a 5000 hz
(5 khz) bandwidth. The notch, noise reduction etc . is superb. It isn't
cheap, but you get what you pay for. I have owned the various JPS, MFJ,
etc. They don't come close to the 599ZX.

I disagree about the noise reduction. The other features are nice, in particular
you get an actual frequency readout of what you're setting, but the noise reduction
is pretty old-fashioned, and makes it sound muffled.

ClearSpeech has the best noise reduction I've heard, but no other features, and
often the other features are what you want.

The Am-com ClearSpeech has no settings at all other than on-off but I use it a lot.
The Heil version I haven't figured out. It has several steps of Clear Speech
NR, which is nice, but the audio levels are all wrong, and (fatally) it cuts out
low frequencies and high frequencies whether it's bypassed or not. (The unit returned
by Heil works better than the way I got it the first time, but still is susceptible
to feedback and strange lack of line-out output. The former is undoubtedly a ground
loop in audio path via the power supply, which is an engineering mistake. The latter
may be an impedance problem but there's not enough in the manual (?) to tell. I
haven't tried to experiment with matching transformers, being discouraged by the
audio frequency loss and the feedback. So, in short, if you're not willing to fuss
with it a lot, you're not likely to be real happy except perhaps using it as a speaker
rather than a filter box.)

My solution is to get every filter and wire them in series (hence my need for a
functioning bypass). Turn on the ones you need.

If I recall correctly at one time I used a Daiwa audio filter briefly. Since then I have
been happy and audio filter free. As far as I'm concerned they are a needless expense.

dxAce
Michigan
USA

http://www.iserv.net/~n8kdv/dxpage.htm

Thanks to everyone for the input thus far. Some interesting
suggestions/points made. Actually, it was in hearing some of these
audio samples online a few years back that I started wondering about
DSP audio filters again (after the NTR-1 had basically put the idea out
of my mind a decade or so back). In fact, I believe it was the before
and after samples of the Am-Com ClearSpeech speaker that replanted this
idea in my head (although I'm a bit skeptical of whether or not these
sorts of pleasant sounding results are what I would really expect to
hear if I put this sort of a unit to work, say, dxing AM broadcasters
in the tropical bands).
One thing I don't particularly care for with regard to many of these
audio filters is the manner in which they so often provide limited
audio bandwidth. Is this the case with the ClearSpeech Base filter?
From what I've read, it seems that the Timewave 599zx has about the
widest bandwidth one might expect with these filters. How would the
bandwidth on the ClearSpeech Base filter compare? Is it of a narrower
range (e.g., would I suffer from the loss of bass frequencies in a way
that I might not with the Timewave)?
I'm reasonably satisfied with the notch filters I'm utilizing and
the audio low pass and hi freq cutoff provided by the VRC; so my
current interest in DSP audio filters has generally focused on
improving the intelligibility of signals that are mired in noise (and I
realize that there's generally a trade-off where this sort of thing
is concerned). Ron had mentioned that with regard to the Timewave
model, though, that "often the other features are what you want."
While I realize that the Timewave model is supposed to be a pretty
versatile piece of equipment, I must ask, with regard to SW BC
listening, what are some of these other features that might be
desirable that I'm lacking at present (aside from the fact that the
DSP filtration is perhaps more effective than the analog VRC)?
Thanks again to all...

J A Mulc...

Shouldn't Timewave be making a 599zx Mark II pretty soon? Haven't DSP
chips advanced greatly since the 599zx came on the market seven years
ago?

In 1997-1998, I was buying computers with Pentium II 266 Mhz processors
and Windows 95 OEM2. Now I'm buying laptops with 1.7 Mhz Pentium M and
Windows XP Pro. I'd never invest in a "new" 1997-1998 computer.

Why hasn't DSP advanced since the 599zx was released?

I've got a two month old R8B with a Par EF-SWL and I really like it,
but the NB of the R8B is nothing compared to my TS-2000. I'm looking
for a DSP companion also, and this thread is perfect for me.

Barry
WT7T