Using CS400i as Binaural Deriver

W4HBM

Sirs, (and ladies, of course),

Have any of you experience with modifying the POLK CS400i
crossover network so as to allow the drivers to be amplified
separately by the left and right audio channels?

In addition, have any of you experience with connecting the crossover, once modified to allow binaural amplification, to be driven by the Positive Speaker Leads from the left and right
inputs?

Doing so would seem to introduce speaker energy only when there is a phase angle difference between the right and left Positive speaker leads, but that is acceptable under the following circumstance:

The speaker is to be used as a monitor for a shortwave receiver that employs Main and Diversity receive channels. These separate channels have individual antennae that are polarized 90 degrees apart, so as to capture distant signals subject to atmospheric disturbances that often result in phase angle differences. The object is to use a speaker that can truthfully reproduce the wide dynamic range of shortwave communications yet remain a point source rather than a stereo image, allowing the receive operator's mind to assemble the phase angle errors and form a cohesive binaural image.

Thank you for your comments and suggestions.

Hal
W4HBM

amulford

Somehow I doubt any experience will be found.

You'd better talk to Ken or one of the engineering geeks about this one.

hoosier21

I had no idea what you were talking about until I saw the image you attached, now it's clear lol

good luck, I would think the CS400i's crossover would need major mods. for that.

RuSsMaN

Sounds to me like a project that would be better starting from scratch, vs modding as mentioned above.

I'm probably talking out of my arse, but would two nice, full range drivers in the correct box not take care of this?

Cheers,
Russ

brettw22

I can't see the pic, so I'll have to give a WTF?!?!?!?!

Tour2ma

Originally posted by RuSsMaN
I'm probably talking out of my arse, but would two nice, full range drivers in the correct box not take care of this?

Agree, but I am thinking voice transmissions so I wonder if a full range would be required???

And next time, Russ, please use a mint suppository...

W4HBM

You are correct in thinking "voice transmissions," and that IS the mode that will be used by the binaural speaker to impart the greatest intelligence.

Let's say between 300 and 3,000 Hertz.

But "voice" in shortwave comprises a few different sub modes
too. There is Single Sideband (Upper and Lower) where the carrier of the disdtant transmitting station is suppressed and just the voice information is sent.

There's AM, and FM and PM, too.

And then there is Morse Code. This is where the ear and brain
act as an input mechanism for the listener to decode,

What gets in the way mostly are two different phenomena: Atmospheric Noise, like lightning crashes heard 'round the world, solar disturbances caused when charged particles hit the Van Allen belts, man-made pulse noises from all sorts of spark-generating discharges like autos, sewing machines, elevators, etc.

And then there is interference from stations around the world exactly on the specific frequency listened to or slightly different, from a few Hertz to a few thousand Hertz.

The radio has filters and digital sound processing to deal with much of the interference, but the real skill and effort takes place through the ear of the listener. The POLK CS400i has a 91dB dynamic range, and believe me, every bit of it will be used.

The parts shipment from POLK came yesterday and there's more coming in the next few days: A complete bill of material for a '400i,
and I wonder if the project would be interesting to y'all?

Hal

sowen010599

Absolutely!

Tour2ma

You bet...

So you want to listen to the tuning "squeals" as well, eh? Then the tweeter's incorporation makes sense...

For just voice, a pair of MW's would have it "wired"...

The voiced speech of a typical adult male with have a fundamental frequency of from 85 to 155 Hz, and that of a typical adult female from 165 to 255 Hz.

Taken from: http://encyclopedia.thefreedictionary.com/Voice%20frequency

One question:
Why only one tweeter when 2 MW's are needed for detecting the phase angle differences?

LittleCar_w/12s

Well, first we'll assume that your positive is the signal source... (I have a system that the 'positive' is the common) You'd be correct in assuming that the differences will be heard through the tweeter. Now, I am wondering if your tuning differences are in that range? If not, a small full-range would be better there, and, given it has a resistance equal that of the mains, it wouldn't need the crossover. (Your source could possibly see half the resistance of each channel if there is a 180* inversion.)

You are, of course, designing it to be a single-source-point, so unless you need the higher frequencies, or your tuning squeal tends to be higher than voice, you could follow Tour2ma and ignore the tweeter.
-Jerry

W4HBM

The mods are complete and the CS400i is hooked up to a solid state 180 watt shielded amp, but other "honeydo" chores somehow got in the way before the live test.

I will report back on the results.

Hal

Tour2ma

Originally posted by LittleCar_w/12s
You'd be correct in assuming that the differences will be heard through the tweeter.

So I was guessing along the right lines.. thanks...

Hal,
Will look forward to your "review" and comments on the other questions Jerry put forth...

VR3

That is the first time i have seen someone 'chain up' their speaker on the ceiling...

I am sure it definetely had a cool effect...

Do you have bird cages (like in dungeons) chained up in the corners of the room too?

This sounds like an interesting mod and I am definetely interested in hearing about it!

Tour2ma

Lil bro... Chaining speakers is real old school stuff from the 60's and 70's... Very common with vintage Bose 901's among others, if fact you see a fair percentage of early 901's on ebay that have holes in them from being installed this way... Somewhat a product of small dorm rooms in college, and very inventive baby-boomers. (Also quite common to use cinder blocks and planks to make a cheapo equipment rack.... I had a couple of those...)

Also, if you notice the rear bottom edge of Hal's 400 is pinned against the wall and at least a couple of the chains are angled to produce the force to pin it there... Free swingin' is no good, so even in ceiling hang set-ups where the speaker ends up not touching any wall surface, the chains were never perfectly vertical, but were flared out with an offset 10 deg's or more to induce some lateral stability...

Now don't go grabbing a drill and Dad's tire chains, or Mom will get upset...

VR3

You dont have to worry about me chaining my speakers up...

Not because it would look bad, not at all...

But, because my speakers use a removeable TOP CAP...

I'd hang it then...PLUNK!

Tour2ma

... but then maybe you'd come back into the light....

VR3

Don't think so!

W4HBM

Some one mentioned something about the speaker being pinned. The cabinet is suspended from four springs with safety chains and hangs roughly one half inch above some other equipment and the only connection to the wall behind are the two SO cords for the speaker lines. This way the speaker is directly above the operating position and won't affect the audio spectrum analyzer or RMS level meters with induced mechanical vibrations through the operating bench.

The first thing to note is that the solid state amplifier, a Radio Shack 180 watt, 12 volt D.C. automobile amp, does not have an input attenuator to lower the output to zero. The speakers are always making noise if the radio is on, and the only way to quiet either the Main or Diversity channel is to attenuate the receiver front end. New amplifier time, and suggestions are welcome. The Polk '400 can stand 200 watts, and I think the best idea is a fully shielded solid-state amp, a step up in quality than the RS, though, might be in order.

Secondly, the amplifier is not as shielded as I thought. The computer microprocessor can be heard even with the volume at minimum. I might need to change the speaker wires and install 14AWG shielded cable witht he amp end of the shield grounded and .01uF disk caps as RF bypassers at the speaker terminals.

So the listening test.

As seen on the picture below, the Main Receive channel (TRx1) and the Diversity (Rx2) are picking up a signal at around -10dB,
so the two antennae are reasonably performing. The signal is a radio teletype station heard on an ionospheric bounce, so the Main receiver's response is to a wave that is phased just a bit differently than the Diversity receiver's.

The CS400i is not a speaker I would use in an apartment in this circumstance. Witht he cheap amplifier set at minimum volume the '400 is putting out around a 75dB SPL, and that's just fine in the radio shack. As some of you might know, the Radio teletype signal sort of goes, "Deedle-deedle." The signal is a mixture of two tones that are 170 hertz apart, and their alternation pattern provides the letters or numbers. The trouble comes with atmospheric interference and delay. Tuning the radio to just the right point that provides the low and high tones with 170 Hertz separation is difficult to do with a signal that's "5 by 9," and a real chore when lightning crashes and the boiling ionosphere change the tones.

However, the effort was well worth it. Sitting under the '400 my ears are presented with an image, a binaural image, and this image moves around, seemingly, as the atmosphere changes the wave phase throught the different antennae. Since the radio can tune to within 10 Hertz on main and diversity, separately, I can adjust for the Doppler Effect loss on one channel with a slight mistuning on the other.

Just as my brain resolves this image, the audio mixers in the receiver follow my directions to the tuning, and the computer is presented with a composite signal that now ends up with fewer error characters and a faster intelligence capture time.

By the way, the tweeter does emit. Even slight phase angle changes produce a voltage variation to allow a potential difference.

Not Bach, like most uses for fine speakers, but an application where POLK Audio was suggested as a winner and found to be so, hands down.

Respectfully,

Hal Mandel

Tour2ma

Whad he say???

Glad it is working for you HAL... (BTW, loved you in "2001: ...")

My bad on the speaker suspension... closer examination of the posted pic does show a small gap between the lower rear edge and the wall. Obviously fine for your application... not a suspension I would recommend for a speaker in music or HT service...

What is it about the 400 that makes it so right for your application?

Enjoy your "Ionospheric" journeys...

W4HBM

In a recent web discussion in a High-Frequency radio reflector net someone was talking about how to take full advantage of shortwave receivers with Main and Diversity channels, and instead of using the 3-watt el-cheapo speaker and the blend control to mix the two audios, to take the unattenuated audio appearing as -10 in the rear aprons and amplifying them with a stereo amp and having a binaural image deriver.

Someone else said they did that and went through six or seven kinds of speakers, trying for that unique "image" that a true binaural system will create, and they tried a CS400i and the results were like night and day compared with other brands in the same practical category.

So since then, all these geeks have been searching for '400's.

By the way, I ordered a Marantz PM7200 integrated amp to replace the RS junk. The word is that the chassis is super-shielded and not prone to extraneous hum in the overhead.

Thanks for your kind words.

Hal

LittleCar_w/12s

I'm glad to hear that Polk came through with flying colors.
I was wondering if you used the crossover at all or simply direct-wired them?
Additionally, do those receive/diversity receivers come as a single unit, or are those a hobbyist's venture?
Enjoy... There's nothing more interesting than receiving some weird message from the other side of the planet... it's almost kinda alien in a sense. It's amazing how the atmosphere works like that.

W4HBM

Sir,

There is no tailoring of the audio as in a equalization manner. The audio portion of the signal, once stripped from its high frequency radio wave, can be filtered in any number of ways: The audio can be stripped from the sides of the channel, the audio can be notched, either in a positive fashion, to highlight a segment of the spectrum, or can be attenuated. The audio can be processed to change phases so that an interference nearby has its carrier wave nullified by a 180 degree-difference (or adjustable) simulated wave.

The idea behind using a Polk '400 is to have both receivers speaking simultaneously, from a point source, without a stereophonic image. The listener's brain forms a three dimensional image of the signal then. I cannot describe something that is a chimera. If you look down a hot, dry road in the desert you may see a heat mirage. That is what happens when the two radios are put through the Polk '400, at least in a sound sense. The chimera, or mirage, if you prefer, is the composite image generated by the binaural action of the '400's two speakers when their sound reaches the processing facility in the brain.

The image below shows the two radios tuned to a differencein frequency of ten Hertz. Even this paltry amount of difference is amazingly obvious.

respectfully,

Hal

HBombToo

have the ability to sweep across a 20k band and make pictures:D

all that aside;) the 400 is crossed around 2k so how about a picture at 2.5k?

Great thread so far.

Henry

HBombToo

Originally posted by W4HBM

Let's say between 300 and 3,000 Hertz.

I learned 350 to 4Kc....

with a crossover at 2Kc you really should consider bi-amping:p

Twin

Tour2ma

Look.. lights and dials... :cool:

OK, everybody who had to look up "Chimera", raise your hand...


Actually, that's not the Chimera I remember from mythology... more like Lions head, goat body and dragon tail...

W4HBM

I didn't understand what you meant by a "picture."

One word, "image," was that of what my mind sees when the binaural effect happens, and that's not a "visual" picture.

Forgive my ignorance. I am at a loss as to how to describe the sensation or perception of depth that the '400 helps create.

If you allow the most literal interpretation of "perception," it's an object in a field. The "object" in this case is formed by the arrival of two different, yet very much alike signals, varying in their arrival times and wave phase angles. My mind, and other minds, from what I've learned in reading about this phenomenon, is tricked into formulating the "object," (like the mirage), by the point source of the speakers operation.

Aha! I just thought of a good analogy: Laser holography. The hologram is based on the interference pattern two or more beams of coherent light create when one is disturbed by vibration.

The interference pattern is a Moire, and is related, but not the same as either of the two sources of light. Exactly.

Another thought when you asked for a picture is a display from the audio spectrum analyzer. The image below is a summed display from the Main and Diversity channels. Is that what you meant?

A third thought was that of the radio conveying imagery. This can happen in the shortwave spectrum via slow facsimile or slow-scan television. A composite image that fills a computer screen may very well take a few minutes to complete, and those modes are not sought out at this time.

Hal

P.S: No F#%@ing Pod Bay doors, Dave.:mad:

Tour2ma

Originally posted by W4HBM
P.S: No F#%@ing Pod Bay doors, Dave.:mad:

That's the spirit...

And Henry, loved the bi-amp crack... LOL.

HBombToo

Well written imo.

I thought I was the only goof that enjoys spacing on light.

Whats the min/max range of your spl scale in dB?

twin:D

BTW I figured you'd get that Tour;)

W4HBM

The SPL range is -77dB to +126dB.

That's the meter. My ears are a completely different story however, and that is quite a bit more attenuated......

The Marantz PM7200 amp came last week and I hooked it up, replacing the rad/shack 12-1967A brick. A wise choice.

The operational results:
1. The '7200 has two pushbuttons to select monitoring the tape playback or a CD-R/MD playback. The record selector choses either SOURCE, OFF or Tape>CD-R or CD-R>Tape. I can hear relays clunking when I push buttons or turn dials. No wafer switch contacts to corrode.:p

2. The amp has a cap-charge timeout that picks the speaker output relays after the amp powers up. No thumps.:p

3. The amp has a remote control (just what I needed, another remote control) and the amp can go into Mute or Standby only with the remote, not by the front panel. That sucks. I'm too busy to play with the buttons on a remote, holding it in the right place so the IR diodes see one another, choosing the right buttons, blah, blah. The Standby condition keeps the main power supply energized and opens up the various relays, and touching any of the controls OR pushing the remote button brings it out of STBY.

4. The Mute feature opens the input and output relays and leaves the amp cooking. There are LED's for STBY and Mute.

5. The Input Selector is a round knob that can go 'round and 'round and its contacts select the right set of input relays and panel LED's. The remote just operates the relays and the knob doesn't turn by motor like the volume knob, when the Volume button(s) are depressed on the remote. From product literature I see that even the $7500 Marantz products have Input Selectors like this.

I would more appreciate dual volume controls and input buttons, just like the Tape and CD-R/MD buttons. There's plenty of space.

6. There's a Source Direct button that bypasses the Balance, Bass and Treble controls. It also shuts off the Tape/CD-R outputs. What are they aiming for, a parametric amp? Another useless feature.

7. The Class A/ Class AB button. From what I gather, the amp can go into Class A, which means the drivers and PA's are all pushed at max tilt and the volume control just attenuates the signal. In AB mode, the voltage to the devices vary with the signal. With all the monitoring stuff around here I did an A/B test with a bunch of different inputs, like single tone, dual tone, speech, music, etc., and could see no difference in the output waveforms measured with the audio spec, dual RMS voltmeters or the 'scope. Maybe I'm not sophisticated enough to detect the difference. Oh, yeah, the cabinet gets a lot hotter on top in Class A, witht he power supply humming along at full tilt boogie 100% of the wave.

8. The connectors are all gold plated. There's a "processor" input and output set o'jacks. I guess that's where the equalizer or other goodie box can go. The Marantz specs say there's no equalizer port at "Pre-Out, Main-In," so without a road map I can't tell where the "Processor" jacks break the circuit. Your guesses are as good as mine.

9. The speaker terminals are a real **** on wheels to get wire into. You all know how Polk Audio speaker jacks have the gold-plated banana/screw terminals with a big area to get a spade lug, banana plug, wire tip, etc., into? Well the Marantz terminals, when unscrewed, uncover a small port at two o'clock, and the consumer has to squeeze past other posts to get speaker set One wires into the posts. (Why not put SPKR1 on top, and not on the bottom row?) No metal shows at all. No banana sockets, and the speaker terminals are round, with some knurling to allow fingers, greasy with No-Ox or the equivalent, a sort of grip. No using the 7/16ths. nut-driver there. (Fehh!).

10. The amp has a magnetic cartridge input with a shell ground terminal post alongside. You listen to LP's, huh? (Look in MusicDirect.com for their $29,000 turntable selection, sans tone arms...) The phono input is gauged at 2.5mV@ 47K ohm impedance with a .5dB response curve and an 85dB S/N ratio. Looks like if you buy this kludge for listening to LP's you better have a good idea what your cartridge specs are or you're gonna have to buy a phono preamp box to tailor the tone arm.

11. The headphone jack in front is gold-plated.

12. The volume control has a dimple, but you need to look very carefully for it, and the escutcheon panel does not have a scale, just a "MIN" and "MAX" I might be painting something later today.

13. The Balance, Bass and Treble knobs have center detents. For the similarly-dimpled knobs that are hard to spot.

Listening:

1. The power supply doesn't rattle the chassis when operating. It's right in front of my face, so I could hear it if it did.

2. The amp has virtually no overhead hum even with the volume knob cranked with no signal input. I grounded the chassis with a 8AWG stranded cable to the RF Ground Buss Bar to lose any chassis "hand" capacitance when the station is transmitting and the inclusion or exclusion of that doesn't change the overhead, like introducing a 120Hz hum like other amps with two bladed power plugs sometimes do.

3. At a flat setting the amp doesn't change the waveform appearance. I guss that means it's just an amplifier and not an amp/equalizer. I had a Marantz back in the early 'Seventies and liked that box a lot, and that's why I chose this piece. At 500 bucks I could have had a 1,000 watt Peavey, but those are meant for stage/performance and they tend to have horrendous overhead noises. The RMS output is rated at 95 watts, which is just a reference figure for me. In Class A, the manufacturer says "25 Watts RMS, 28Watts DIN." Considering the shortwave set pumps out a mighty 3 Watts in its speaker terminals, a power factor increase of thirty is just fine.

I apologize for all the bandwidth. Figuring that some would be interested in the progress of the binaural experiment, and using pieces of equipment in the experiment we might all encounter was worth examining and reporting on, these words appear.

And Dave, stop noodging me about them g*dd#mned pod bay doors or I'll turn off the heat-
Hal

Tour2ma

Hal,
No need to apologize for bandwidth. Those interested will lap it up; those not... well, not like they are locked in a room with you...

Just, please, don't start singing "Bicycle Built for Two"....

VR3

I still dont understand (big surprise eh?)

What is the exact point of doing something like this??