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DIY the device of US Patent 4,899,387
DIY the device of US Patent 4,899,387
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Old 1st March 2018, 06:33 PM   #91
Antoinel is offline Antoinel  United States
diyAudio Member
Join Date: Jan 2012
Location: Pennsylvania
DIY the device of US Patent 4,899,387
Default What's going on?

It appears that this sound system behaves like the device described in the Pass patent under study. It cleanses the room from resonances, and/or removes some bass energy from it . Here's a plausible explanation for the time being. Please refer to the attached and same schematic.

1. Let the voltage source amp [VSA] energize coil #1 so as to enable the woofer cone to [say] move out or travel towards me.

2. DEFcg is a current bootstrap. It simultaneously reacts by fully energizing coil #2. Thus it helps VSA to push the same cone out; because the currents through both coils, and the two coils are in phase.

3. Here's the important connection. A slight vacuum from a standing wave in front of the cone can also pull/move it out towards me. Thus, coil# 1 [and/or #2] become a microphone with a current flowing through it. This simultaneously causes the DEFcg current bootstrap to inject a similar current in coil #2, and thus help/move the cone out. This resultant forward motion of the woofer generates a slight positive pressure which minimizes or wipes out [meaning counteracts] the vacuum as taught by the Pass patent. Essentially absorbing the standing wave per this invention.

4. Let the VSA energize coil # 1 so as to enable the woofer cone to move back or away from me.

5. The resultant reaction of DEFcg current bootstrap is to help the cone continue to move back; meaning in the same direction which was initiated by VSA.

6. Here is the second important connection. A slight pressure at the face of the woofer from a standing wave pushes it back or away from me. The cone and its coils become a microphone. The consequent current bootstrap action of DEFcg pulls the cone back; meaning it keeps it moving in the same direction away from me. This motion of the cone creates a slight vacuum which minimizes or wipes [counteracts] the slight positive pressure from the standing wave and/or resonance. Thus absorbing the standing wave and/or resonances as taught by Pass in his patent.

7. Here is a third important connection. The resonances above are clearly external to the woofer cone from standing waves in the room. But; they might as well be inside the box housing it. This suggests that the combined operation of the loudspeaker [as box microphone too] and the Overall Power Amp [OPA; special!] cleanse/improve the performance of the loudspeaker itself.

Notes left over from previous posts:

1. I am a Bass Trap when I sit in the corner and listen to music. My muscles, some adipose tissues, and the garments I wear are naturally absorbing of base energy. Push comes to shove I may even consider cloaking myself with additional approved bass trap materials to augment the performance of " yours truly" bass trap. I'd say I'll be one funny sight to behold, but absolutely no itchy fiberglass stuff!

2. An error on my part. The longest dimension in my test room is the diagonal from a ceiling corner to the opposite floor corner, and not that on the floor only. The new wavelength of the most offending room resonance [per Pass patent] is ~36 Hz instead of 40 Hz.

Are you ready for a stereo system?

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File Type: png DEFcGRA.png (50.4 KB, 92 views)
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Old 13th March 2018, 05:19 PM   #92
Antoinel is offline Antoinel  United States
diyAudio Member
Join Date: Jan 2012
Location: Pennsylvania
DIY the device of US Patent 4,899,387
The prototype amp/loudspeaker system which I listened to and mentioned in the previous post was modified and improved. The new schematic is attached. Additional info is found in the last two posts of the "DEF" thread. Please note the following relevant changes:

1. The location and circuit arrangement of the encircled two voice coils 1 and 2 of the dual voice coil [DVC] subwoofer. The indicated relative phase of the voice coils enables Positive Feedback. Positive feedback is preferred in this application

2. The previous voltage source amp [VSA] which has a possible voltage gain = 21 X [say that of SONY MHC 1750 amp] was replaced with a power buffer/follower [see post in DEF thread].

3. The bias or current idle of the FETs was increased to +/-0.6A. The ideal and future bias will best be at ~+/-1.3 A at +/- 23 Vdc . Because it is the primary source of power to the load.

4. The power buffer/follower delivers a small amount of music power to the voice coil #1 of the subwoofer and thus to its satellite loudspeaker. Little output emanates from this satellite loudspeaker. Consequently, this satellite loudspeaker can be replaced with an 8 Ohm non-inductive power resistor [so as to load the internal high pass crossover network]; but without an effect on sound.

What has not changed?

1. The loudspeaker system is the same and is in the same corner of the room.
2. My listening position is in the opposite corner along the floor diagonal [~28 feet away].

Subjective observations:

1. The bass is thunderous, clean and tight.
2. The rest of the audio spectrum is highly detailed. Vocals are intelligible and crystal clear.
3. Could not detect standing waves by walking towards the walls of the room.
4. Listening to this system for an hour+ was a satisfying experience. And that is my objective
5. This music system is stable against oscillation; provided the power buffer to its input is connected [see the last 2 posts in the DEF thread].

More to post on absorbing acoustic trash in the listening room...

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