Reviving the HTPC

I gave up on the HTPC because of lousy software for DVR and Over-the-Air High definition. I bought an over-the-air receiver for $40 and it is great (it still isn't a DVR, but I don't have the frustration of debugging ATI software releases).

However, there are two more reasons for HTPC

• Network storage of DVD images
  
• High-quality DVDs to my projector

I've discussed these on the forums of Home Theater Shack and when digging around for information on how I could hook up my Dreamcast (VGA), I stumbled back upon articles about upscaling.

I'm going to look in to RatDVD to store DVD images, since this format keeps the DVD menus and high quality sound, but in 1/4 the space by re-compressing the image stream in a newer format. This should be easier than swapping DVDs all the time.

The other reason has to do with upconversion. A little background: DVDs are a format stored at 480p. That means there are 480 lines of information available to be displayed. Most projectors are far higher than that, my own has 768 lines of resolution. These same projectors usually attempt to fill the full image by doing some amount of interpolation of images so you get the full size screen. This works well enough. However, when (my) projector gets this image, it is in analog format and with so much information it can only scan this signal so fast before it just gives up and punts, which means a soft image. But, DVDs are stored as a digital format- a series of scene descriptions which are converted into the analog signal. At the DVD player itself, if this interpolation was done before analog, knowing the output to 720p or other format, it would result in a much clearer picture (because it avoids 'generation loss').

Indeed, there are 'upconverting' DVD players which do just this. My Philips player does this. Except not over component- only HDMI. There must be some technical reason for this. Wait a minute, component can handle 1080p. Turns out there is no technical reason for this at all. It is a Hollywood restriction. For some inane reason, it was done to prevent piracy. Which means that the DVD that I own cannot be viewed on the equipment that I own using the better image processing of equipment that I own. Smells like a lawsuit, or a DMCA exception. Indeed, there are players outside of Hollywood's Iron Curtain which play upconverted content: Oppo, NeuNeo, etc. I don't see any reason to go buy yet another DVD player when the one I have does this same thing, but has component HD output disabled. It makes no sense at all- Hollywood doesn't benefit from me buying a new projector that accepts HDMI, and I cannot imagine a casual users (or even a hardcore one) bothering to upscale their DVD, output to analog, then somehow capture this (analog) and re-encode it to save it as high-def. They're probably targeting some fly-by-night shop in Singapore who might have this equipment, but inconveniencing millions of valid users of this technology. The MPAA sucks.

Update: some clever guys have made an HDMI converter! Sweet! In-line, and external.

Which brings me back to HTPC. It turns out that PCs can play DVDs. Out their VGA port. Oh- and by the way- the PC, with its wealth of horsepower, can upscale an improve images amazingly so. And, by the way- over VGA, which is superior to component! I can output images at 1600x1200, no problem. Oh- and if I had to, since VGA is an analog signal, I could make component cables.

I don't have to, since my projector accepts VGA (like many other do).

Therefore, the HTPC is getting revived. Stay tuned.

(BTW, Vista won't let you do this- it only allows protected content out an HDMI video port)

Sweeping up

I've learned a lot running this REW program and getting advice from the Home Theater Shack.

Here's what you want with a subwoofer: low frequencies with a 'ht' sound. This means that low bass is going to be louder than mid bass because how we hear depends on the frequency.

My 18" drivers have surprisingly good range- they seem to love the 100Hz range. Problem is- that frequency is directional. Everything over 80 is pretty much, so the subwoofer is confined to low frequencies- and you let your mains do the rest.

On advice, I set all my speakers to 'small'. This means the receiver should only send low frequencies to the subwoofer channel. I also set the crossover frequency to 100Hz- this is the point where the receiver tries to transition from the sub to the mains.

Here's what my mains only look like:


Here is what the sub by itself looks like (unfiltered):


And after a bit of fiddling, here's what the sub is by itself with several filters enabled.


I've saved my filters as 'FP6'. Heck, I'll store the file here: fp6.req

If you see, I had to really force the curve downward. This is even with the receiver allegedly trying to do its own crossover.

I try to match to a curve set for subwoofers- but with a 'house curve' thrown in. The intent is that sound at 30Hz should sound about the same as at 80. For that to happen, low frequencies needed boosting. If you look at the dark blue line above you can see that it isn't a perfect curve due to the house curve.

Now, let's see what happens when I add my mains back in.


Well, something weird has happened- with the mains added, the output is lower in some parts of the range. That's probably because of phase. Don't see it lower? Look here with all of them combined.




The black line is the combined signal. You can see it tracks the sub at low frequencies (<50) style="color: rgb(51, 102, 255); font-weight: bold;">mains at high (>100), but in that crossover region, it is lower than both.

Insulator 2

Way back when I rented an insulation machine to do parts of the climbing gym and ceiling. I left a good bit un-blown because I needed to finish up wiring and such. The flip-top gave me easy access to this area now, so... I did it. The boys loaded while I moved stuff around in the attic.

What a mess- but at least it was paper and not some nasty fiberglass.
I'm done with this for now- about the only insulation left is that of behind the bookcase and stuff, but I think it is pretty tight.

The Flip-top!

Here's the end result of my work. This is a view from in the attic space, having entered by swinging open the manifold. It is extremely heavy- especially with the drivers.

It did exactly what I wanted; I was already able to use it to get into the attic to add more insulation.

Were I to do it again; I would use the same design, but make it lighter by not using doubled 3/4 MDF. I think birch or high quality ply, and maybe just 1/2" MDF. A manifold design doesn't vibrate like an array would and just has to cancel its opposite speaker.

scREWing around again

The new version of the program is pretty, but it is still frustrating. Actually, I've got some gripes (minor, because this thing is free!) that it is still painful to send settings to the EQ. Also, the new version makes it hard to compare reading after reading, opening each one in a new tab and making me reload my filter settings from disk if I want to compare what I changed on the last run directly.

In any case, I've got my sub-only response curve to be flat (actually, it rolls off like it should). I've barely started adding in my mains, but they really screw up my graph- there seems to be a lot of holes when they get involved. Part of it is probably because of where I need to set my cutover from my receiver- I've upped it to 200Hz so it doesn't take as much effect. The second thing is that my receiver is a little too smart- it wants to know what size my other speakers are so it can decide what should go to the woofer. Right now I've set my mains to 'large', and everything else to small, but wondering if I should set everything to small so the dedicated woofer does its thing alone?

IB wiring help

Figuring out how to wire a speaker gets much more complicated once you go past one. My Tempests went up the street to a neighbor, where they were complicated enough because they had dual voice coils. I managed (check older posts) to figure out how to wire them with some consulting, but Andy wants three of them. He should have four, which is how we cut the MDF, but since it is a line array, the need for opposing drivers doesn't factor, and WAF took over.

In any case, I called my friends, asked the Cult, got advice from EEs (I forgot the formula for calculating resistance in parallel- for reference it is Rp=(R1xR2)/(R1+R2).) until I finally came across this link for wiring pro speakers. There's even a cgi speaker calculator.

REW again

One thing for any sub is that your room will have an effect on low-frequency sounds. To compensate for this, some high-end receivers can send and 'hear' sounds and do some amount of equalization.

None of them can approach the Room Equalization Wizard which is used in conjunction with a PC which plays a variety of sounds, sweeps, etc. Hook the PC output to the input of your sound system, and hook up a soundmeter to the line input. With the right cables, it can also program something like the BFD (DSP1124) with multiple filters to tune it right to your room.

As it is, I rebuilding my shuttle to do the work (it has a nice built-in soundcard), though you'd think I would use the HTPC. The HTPC is being used as the girl's PC for the moment mostly because software for HTPC is abysmal.

FiCar finish

I'm not a dissatisfied customer (no intention of sending them back) but wanted to give a head's up on the finish of my Q18s I purchased. The construction looks good, it's a solid driver, but the finish was disappointing. Where the surround was glued on was offset as it related to the basket meaning that all the holes on both drivers needed to be drilled out before installation.

I still think it is a great deal for the price, but be aware that you might need a little more install time to do that step. I've been in contact with FiCar and I get the impression they'll make sure others don't go out the door that way, but wanted to give a head's up.

I drilled them out. I have photos, but IMO, there's no excuse for it. It wasn't so much the variable radial nature, but that it was set off a few degrees so that all of them were off. It slowed down my install; if I'd have used clips, I wouldn't have even noticed.