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Help out your exhaust fans

By red1776 ยท 35 replies
Oct 11, 2010
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  1. captaincranky

    captaincranky TechSpot Addict Posts: 12,514   +2,308

    My Hero.......

    I would ask this existential question of you, "If a tree isn't killed in the forest, but an eco-freak is there to save it, does this still count as a rescue"?

    Point being we were having such fun, vintage loudspeakers are so much more of an interesting topic, than crap-a** Chinese plastic fans, no matter how many you stack together.

    The external fan could be dangerous without a guard! Consider this, you're watching porn on your computer, and a connector on the rear of the computer comes loose. So, you rush around to the back, trying to determine the problem. But, your screwdriver, (the Phillips head, silly), is in front. Absent mindedly, you lean over the case, that's when it hits you. As the rush of pain envelopes you, you think, "why me, I was already circumcised".

    Oh shoot, I suppose we should go back to reinventing the multi- stage supercharger.
    The "RIAA roll off curve", is the only thing that the RIAA ever did that didn't involve litigation. What it amounts to is this, when recording an actual "record", the high frequencies are expanded, onto the disc, then reduced on playback. This is because if the HF was put on the disc at its normal volume, the grooves would be so tiny, the first pass of the stylus would wipe them clean. It's a lousy primitive process at best. I'm guessing that the "sounded awful", was just growing pains. Two inch tape in an 8 track studio recorder @15 ips, really sounds pretty good, there's not an awful of tape hiss, believe it or not. (Given the same magnetic particle size, every time you double the tape speed, the center frequency of the noise goes up one octave. At some point, the hiss wil go ultrasonic, and therefore invisible to the year. (Yes, that was an oxymoron). The net result is this; the master tapes had a much wider dynamic range then the records ever could. Absolute dynamic range of a medium is determined by its noise "floor". You can only reduce the signal so far, then you hit the SN ratio's limitations.

    Every speaker cabinet you have this notice on it, "the buck stops here". Correct stereo imaging has less to do with the amplifier than it has to do with the speakers. Precision in manufacture yields identical products. Two identical drivers will be reproducing the common portion of a stereo signal identically, and with that, the "stereo image" will be correctly positioned. Asymetrical driver movement nets phase shift, and time distortion.

    The fact of the matter is, the transient response of a correctly manufactured loudspeaker, is the last stage of the reproduction process. Beings as it's mechanical, and not electrical, the laws of physics take over at this point. It's all about precision tolerances, and a massive magnetic motor, that causes 15" cones to move like the diaphragms of a head set. Good drivers accurately trace the signal path, cheap drivers plow out their own impression of it. JBL used to flatly state, "the transient response of our loudspeakers, is unparalleled"? That's about the last time I've seen truth in advertising.

    And then there's Enya. As someone who listens avidly to Loreena McKennitt, I don't have the right to snicker at somebody who listens to Enya. I reserve the right to be puzzled though, she has the talent, that's a given, but I just don't get her. Loreena has a better instinct for storyline, along with a better flair for traditional instrumentation. (IMHO)
  2. captaincranky

    captaincranky TechSpot Addict Posts: 12,514   +2,308

    See Above.....

    See above....
  3. EXCellR8

    EXCellR8 The Conservative Posts: 1,835

    my fans were actually made in Taiwan... and they are just riveting.

    besides all that stereo talk would make for great discussion... in the audio section :)
  4. captaincranky

    captaincranky TechSpot Addict Posts: 12,514   +2,308

    Depending on who you talk to, "Taiwan" is China, but that would be a discussion for our "political section".

    We have an audio section?
  5. Adhmuz

    Adhmuz TechSpot Paladin Posts: 1,769   +598

    We do have an Audio section, its just shared with the Video section so its kinda overwhelmed by "My video card is XX hot, is that bad?" or "If I'm seeing weird colors and shapes on my screen does that mean my graphics card is dead?"... No one really talks about proper Audio either, hijacking threads is just that much more fun. AND for the record I have fans made in Austria, at least I think thats where they come from.
  6. captaincranky

    captaincranky TechSpot Addict Posts: 12,514   +2,308

    Ah yes, the "Kaiser Blitzkreig" models, I know them well.

    For the record, as a topic, stacking exhaust fans, has a fairly short shelf life. I'm guessing that Red just put it up as a tech tip. "Hey, this is pretty cool, it worked for me", like that.

    The concept of moving air in and out of a rectangular box, really isn't that deep. I'm sure there are those here that think is is, but trust me, it's not. I was also involved with radio controlled aircraft at one time, lift, drag, incidence, center of gravity, airfoil cross section, wing planform, decalage, and so forth.

    If this thread were started by a noob, then I would concern myself about maintaining topic. It wasn't, and I'm fairly sure that Red himself appreciates the audio discussion, at least as much as the original issue.

    Beyond that, this forum has been fairly dead recently. Business as usual, "I think I'll join so I can get some free computer counseling, and if I don't, no problem, I knew it all already". Or better still, I can keep asking the same question over and over, until I get the answer I want to hear.

    So here's the deal, the fan outside the back of the case creates a partial vacuum, thereby allowing the fan inside to revolve faster, which in turn creates a deeper vacuum behind it, than would normally be present, inducing an exaggerated inrush of air from the case proper. It would either work for you, or it wouldn't, but that boys and girls. is the extent of the issue. Going much beyond that would just be running our mouth(s) anyway, whether on topic or not.

    Here, go join this payaso's third "2" thread; https://www.techspot.com/vb/topic154813.html , and make sure you stay on topic.
  7. red1776

    red1776 Omnipotent Ruler of the Universe Topic Starter Posts: 5,223   +163

    This is my thread!...I started it, and if y'all don't stop it, I'm taking my thread and going home.....:p:rolleyes:Now then.
    ** not to mention I have about quadrupled my knowledge of things audio in the last 7 post's.

    So somewhere in here is where the damping ability of the Amp comes into play? does it not take an amp with very good 'damping' rating to reproduce accurate low frequencies? not to mention that it becomes more important the larger the physical size of the woofer?

    I purchased that Loreena McKennit disc you linked me to last year during another "train wreck" of a thread you and I had going. ;)

    @ Adhmuz, I provided you with the requested explanation of the 1000 CFM situation you asked for https://www.techspot.com/gallery/member-galleries/p4037-here-ya-go-supersmashbrada-21.html
  8. captaincranky

    captaincranky TechSpot Addict Posts: 12,514   +2,308

    A loudspeaker, is an electric motor....! And as an electric motor, it adheres to the rules of all other electric motors. If you put electricity into into it, it produces motion, However, if you put motion into it, it produces electricity!

    Transistors are basically current amplifying devices, where tube amps are voltage amplifiers. In a transistor amp, the loudspeaker voice coil, is actually a direct part of the output circuit. This is why the loudspeaker impedance is very important, since it is the mechanism by which current flow is limited

    Then we have a Newtonian issue at work, "a body in motion tends to remain in motion". The larger (more massive) the "body", (cone in this case), the more kinetic energy it possesses, and the more aggressively it wants to remain in motion. The "surround" of the speaker, (as it's also known "compliance") centers the cone and voice coil in the flux field, and damps out excessive, uncontrolled motion of the cone. It acts as a spring, pushing against the movement of the cone, ever harder as the cone moves further away from its neutral, (center) position. Speakers also fall victim to the Newtonian principle, " body at rest, tends to remain at rest". The massier the cone, the more it's affected by these factors.

    Damping factor:

    A transistor is basically a triad of diodes. A diode will only allow electricity to flow in one direction. When the polarity is reversed, current flow is shut down. After a signal ceases, the loudspeaker changes from a motor to a generator, the output transistors clamp off the reverse polarity, and cone movement ceases. So basically, the output transistors act as electronic brakes, taming the cones tendency to "overshoot". In a tube amp, the B+ voltage is in the area of 400+ (VDC). The voice coil needs to be protected from this, so an output transformer is a necessity. The transformer only transmits the AC differential signal, and also decreases the voltage, which ramps up the current (amps) in the process. When the speaker transitions from motor to generator, the voltage produced simply back flows through the output transformer, and no electronic braking is present, or no damping factor exists. The circuit is simply two coils wired in a loop, there's nothing to stop the unwanted cone movement, and it mostly rings with only the compliance of the speaker to account for the braking.

    It's a pity that your Altecs are not with you. High C or above from Ms McKennitt, would be a full body, tingly event. Ear scorching, at minimum.
  9. red1776

    red1776 Omnipotent Ruler of the Universe Topic Starter Posts: 5,223   +163

    They are with me, just in storage in the basement. We have not even got fully unpacked yet from the move. Setting up my 'Audio room' is one of the last priorities.....according to the Mrs.

    That was my general understanding of why I need an amp with such a high damping factor/capability. 15-18" woofers will flop around and not return to 'starting position' in time for the next signal.
  10. captaincranky

    captaincranky TechSpot Addict Posts: 12,514   +2,308

    You just won my, "why I'm not married in twenty five words or less", essay contest.
  11. red1776

    red1776 Omnipotent Ruler of the Universe Topic Starter Posts: 5,223   +163


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