Thursday, March 27, 2008

What the heck are HDMI Amplified/Equalized Cables

HDMI "Amplified/Equalized" Cables
Here's one question that initially was a head scratcher. What's an HDMI "Amplified" cable? It is not "snake oil" unless the amplifier or equalizer is using "electro-static-intermagnetic-resonance amplification" or anything having to do with pyramids.
Well first off, there are really two types of "amplified" cables; Repeaters and equalized cables. A repeater recieves the cables signals, (which are actually split up for proper transmission over HDMI cable) re-combines them, and if its function is simply as a repeater, it splits them up again for transmission over HDMI cables again. It does help clean up signals and allows for longer combined cable runs, but that's not really its purpose. An equalizer cable is similar to the equalizers used in Pro Analog gear to correct for high frequency loss over long cable runs. It takes the signal and digitally equalizes the signal to correct for high frequency losses over long HDMI cable runs. The equalization is matched to the cable, so for best results, cables with built-in proprietary equalization will be more capable than adding a seperate booster/equalizer, or a receiving Switcher with built-in equaliztion. The difference between "designed for the cable" (built-in) and external (seperate booster/equalizers or integrated into switchers) varies widely, it can be marginal, or enough to make a large difference in bit errors, depending on the cables and associated equipment.

Note1: An Equalizer should be used at the end of the cable run, or close to it.
Note: There are those that claim that since digital cables just send 1's and 0's that means that if the cable "works" it is perfect. This is a bit off-base. The closer you get to the "digital cliff" where the signal goes out completely, the more bit errors are likely to occur in a complex "system" like the transmitter-cable-receiver system. This results in video artifacts like "sparkles" where various pixels in the display are of random color values. If bit errors are infrequent enough, they may not be noticed, but large amounts will render the video outcome unwatchable.

So do you need one of these things? It depends. How long is your cable run? If it is long, such as for a projector, or in-wall cabling an above fireplace plasma from across the room, it is likely. If it is not so long, such as for a normal receiver or Cable/Satellite/DVD/Blu Ray player to HDTV connection then you don't.
Bad - image with lots of "sparkles"

Good - No "sparkles"

These images are just resized photographs (ok, not very good photos) of actual bit error artifacts caused by long cable runs. The second image is with the addition of a simple external booster/equalizer with the same cables, and an additional cable for the EQ device to the display.

Wednesday, March 26, 2008

Stupid weeny nerd complaints about speaker manufacturer choices

A Ground Breaking Investigative series! *

Dispersion of speaker drivers and crossover frequencies in speakers is bothering me a lot lately. It really bugs me that in expensive speakers 6 inch drivers and a growing number of larger drivers are very often crossed over in the 2.5KHz range. It's a general rule that a drivers dispersion pattern narrows to about 90 degrees at the frequency where the diameter is equal to one wavelength. For 2.5KHz , that means 5.4 inches. Sure, if you sit in an anechoic chamber, with the speakers facing you, who cares? In a normal room, dispersion patterns play a large role in how you hear those esoterically named things like "soundstage" or "space" around instruments. With uneven responses to dispersion over the drivers spectrum the instruments will seem to "displace" within the space depending on the instruments frequency output. With regard to center cones, waveguides and alternative materials with different breakup modes - while they may help, a quick look at the in depth measurements from Stereophile among other sources will show you that with oversize drivers there is, in the end, a bad dispersion range. Same trouble for all of those 1" dome tweeters, no matter how fancy the waveguide or materials, etc, once past 10KHz things are going to get lossy on the sides real quick. If you're living in a anechoic chamber, who cares? I'm not living in one. Having some frequencies dispersed at 120 degrees or more and others at radically different dispersion angles equals overall room disparities. So, don't just blame your room for "room" problems, your speaker is often just as much to blame.
So why the big move towards two way speakers with even larger mid/woofers, real big midranges, and no super tweeters?? Dynamics is the quick answer. Louder. Cheaper is the second answer, two drivers, instead of three or four. Cheaper. Don't get me wrong, there are many great speakers out there with just such disparities that sound fantastic. They need just the right room.

*Well, just a silly rant actually.

Monday, March 24, 2008


We get questions all the time about connecting older HDTV's with no DVI HDMI inputs to up-converting DVD, Blu Ray player or Cable/Satellite Boxes. It's a bit of a tricky question as we mentioned when first posting about the HD Fury device back in June, 2007. You basically need two devices. The first device (HD Fury) , and this is the "key" device since the other one has a lot of options out there, but this one is very rare if not currently unique. It is also not sold in the U.S. and is seemingly not legal to do so. It converts HDMI video signals at standard HD resolutions up to 1080p into RGB analog video signal of the same resolution as the input. The tricky bit is it seems to remove any problems usually caused by HDCP with similar converters . Is that legal? Well maybe not, but if you bought an early HDTV, before the motion picture industry decided they should screw all early adopters, then it is the only way you can get the highest possible resolution video from many video sources.
The second tricky bit is that for many of these HDTV's you still have to convert from RGB to Y-Pr-Pb (Component Video). For that you'll need a RGB to Component video transcoder like the Audioauthority 9A60.

The bad part of all this is not so much the whole ordering equipment of questionable legality from overseas as it is the overall cost for both items is over $250 before shipping. This makes it a very tough decision indeed for older HDTV owners. Then again, for owners of expensive CRT Front projectors it is a very worthwhile device.