Home Theater

Saturday, December 26, 2009

Some upgrades

The need to watch A Christmas Story in High Def made me dust off the HTPC again.  Somehow in its dormancy it lost the ability to do 5.1 and it broke the bracket for the heat sink.  I have no idea how either one happened, but the heat sink issue shows how far good brands have fallen with their migration of components to China.   The mobo is an Asus M2NPV-VM, which had a good set of features, but something as simple as the plastic bracket the heatsink mounts to being of poor quality sidelined movie night.  We tried watching Ralphie and friends- and had just gotten past when Flick sticks his tongue to the flagpole when the screen went blue.  Not the BSOD, but the projector showing no image.  I restarted the PC and it happened again.    Whenever something wacky like this happens, I suspect heat, and when I popped open the case, the heatsink on the CPU was loose- because of cheap plastic.  I'm not sure what the proper repair is- probably finding a new CPU heatsink bracket and mounting it.  But the mobo would have to come out, and I"m not sure where you find just a bracket for an AM2 socket, so I got out my racing safety wire and pliers and that sucker is on there well now.

Speaking of heat- while poking around my EP2500 was hot- too hot to the touch.  That can't be good.  I had done a trick of putting in a very quiet fan, and reversing it- so it pulled in cool air from the room and vented it out the back.  What it seemed to do was clog the front filter with dust.  I assume the hot case for the amp was due to lack of airflow.  After cracking it open, I'm not so sure.  I went ahead and restored the direction of the fan flow (pulls behind the amp, and vents out front), but I didn't feel any flow.  I crack open the amp case again, and I suspect my 2 year old had been doing modifications as he is apt to do.  I found a twist-tie stuck in the fan shroud, preventing it from moving.  I thought for sure the fan would be burned out, but it spun right up when I cleared the obstruction.

When testing out the sound, I noticed some drops during speech of the movie.  I wasn't sure if it was the receiver or the PC that was not processing the signal correctly, but the receiver certainly did over the SPDIF port of the HD DVD player.  I started playing with the PC and got stumped.  I finally had to revert the PC to do 2-channel sound to get decent playback.  Tonight I found some updated drivers for the onboard soundcard and have 5.1 again.

I still have one more issue to chase down- that of the input to the sub.  My Behringer BFD shows the input as being maxxed out.   I assume as I was pulling and reinstalling the amp that something got knocked loose for the inputs.  I'm using balanced cables between the BFD and the EP2500, but the subwoofer output on the receiver is just mono and I need to chase down that cabling.  Should be easy enough to do.

But the big news of the day (Christmas) is that a buddy of mine bought me a Blu-Ray player.  He's a theatreophile as well (many of my ideas for my home theater came from his excellent setup). Having recently moved, he's without theater and we've had him over for movies all the time.  He decided to upgrade me to BR since I'm still angry from the loss of HD DVD, so this was going to be the only way he got to see high-def again.  I need to reprogram the remote to handle the new device, and need to figure out how to get additional component inputs, but we watched our first movie on it tonight. Very nice.  Thanks Brian!

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Wednesday, October 10, 2007

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.

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Monday, October 08, 2007

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.

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Saturday, October 06, 2007

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?

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Friday, October 05, 2007

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.

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Tuesday, October 02, 2007

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.

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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.

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Sunday, September 30, 2007

The headshot

Mid-way through the driver installation, we took a break to do the IB tradition of the headshot. Think 'money-shot', and you'll understand the importance of this step for any IB installation. Three heads are better than one, and two Q18s are better than four Tempests (according to my calculations, anyway).

Ever the rebel, Griff had to do an alternate IB photo opportunity, though I don't quite think it'll catch on like the traditional headshot.

In the spirit of the innie-outie IB, here's an innie-outie headshot of Griff.

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Innie-outie

Hard to describe, but easier when seen. I needed compactness for my IB, and I needed a certain width (fit between rafters), and I wanted the ability to 'flip' it open to gain access above the HT.

Hence, the Innie-Outie. One driver faces 'in' (the top one above), while the other faces 'out'. Defying traditional views, but making perfect sense (and the reason we of the IB cult do our thing), the back of the speaker moves as much air as the front. The innie-outie takes advantage of this by simply reversing the polarity of the outie driver. I used banana plugs and just rotated one. A quick test with the 9V battery showed that when the innie move in (to the center of the manifold), the outtie moved 'out' (which also means toward the center of the manifold).

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Driver loading


Ha! You can't measure it in Ohms. The kids measured it in grunts. I think it ended up being about 7! The flip-top IB is already paying off. I would have had to drag this through the attic gauntlet!

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Adventures in manifold moving

As described somewhere along the way, getting above the HT is a pain. I actually have to climb a wooden ladder to access the area.

Now imagine climbing a wooden ladder... lifting a huge MDF manifold above your head.

I managed to get it up there... but due to the tightness of the passageway, I had to drag the Tempest manifold out (btw, it is free to whoever wants it, come pick it up). Once that was done, I had to haul the huge Q18 manifold over some HVAC vents and into the place I have to crawl for a bit. I decide to go first and drag the manifold behind me... and it gets hung.

No WAY! I tried putting it on its side, at an angle, etc. I was seriously considering how I could disassemble it and reassemble it, when I- out of frustration- pulled up a 2x4 I had installed a while ago to make it easier to crawl on. The manifold got banged up, but somehow I got it through the passage. Which then brought me to a real horror thought. What if my intricately-designed manifold would be too tall for the space?! I drag it to the spot, thinking I'd end up having to cut off the frame where the hinges would attach. But it fits- swings into place with a good 20mm of room to spare. *Whew*

This thing is going to be cool!

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Friday, September 28, 2007

Latch look


Google Sketchup is cool- all kinds of models you can import. (No, not Russian ones, no.. not ... nevermind).

Here's a view from the bottom. I've actually got two trunk type latches ready to go. The 2x6 rafters will be faced with MDF and the latches will be on that surface, hooking to the inner layer of MDF on the manifold. Thomas of Cult fame suggests a wide gasket surface which I need to pick up.

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Life imitating Art

Art? Hardly, but it really is cool to take something from a conceptual drawing and turn it into a finished product.

This is the bracket for the Neutrik connector, one wire going inside for the reversed driver, with the other going to the forward-facing one.

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Thursday, September 27, 2007

Hinging on a decision

I really want a way up to the attic above the HT. There is one, which from the HT involves going downstairs. Through the kitchen. Up the stairs to the second floor. Down the hall into the walk-in attic. Up the ladder to the second level of attic. Then avoiding the AC and water heater units to the end of that level, taking a left and crawling to the bonus room attic space. Believe me, when I'm up there and find I'm missing a screwdriver for what I need to do, I pretty much give up for the day.

Enter the HingedIBManifold (tm). I've asked the Cult and got no response on if it is feasable. The idea is that the manifold will sit in a frame on top of the existing rafters. This frame will be hinged to the rafter on one side. With corresponding latches on the underside- and a clever reversed driver on the hinge side, I should be able to get on a ladder, undo the latches and use the manifold as a trap door (can trap doors go up?).

Here's the latest SketchUp with hinges.

Click on it to get a bigger view. Also note the Neutrik panel with wires going to both inside the manifold and to the second driver.

The 'hinging on a decision' part is that I can install the manifold as is, without the frame. The dimensions are the same and it would fit within the rafters- and be somewhat more solid. However, I've pretty much decided that the hinge will happen (translation: I've already bought hinges and latches).

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Neutrik bracket

I love the solid feel of the Neutrik connector. I've built a bracket for the connector and will be attaching it to my manifold. I've already wired the end of my speaker wire going to the EP2500 with a Neutrik plug and tested it into the receptacle on the amp. The EP2500 sends both channels on the upper connector so I only need a single one for the 4 wires going to the sub. I'll be setting it up as parallel again (single input, dual outputs).

Here's the latest sketchup of how it will be wired and mounted.

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Your friendly neighborhood speaker store

These guys are so old-school, I don't think they even have a website. Despite the low-tech, I love going to Creative Acoustics in Raleigh, NC. I first met them when I had some speakers rebaffled. These guys *love* sound. The back of the shop is a workshop with templates of huge speaker boxes- most of their business is pro-sound. The front is a retail store for car stereo and such. And inbetween is the service area, that gives me a thrill when I get to walk back there.

Sure enough, they had both neutrik connectors I needed and t-nuts to secure the woofers to the manifold. I also got advice on how to wire the connectors, how to run the wire into the manifold and how to gasket my trap door. Find that for free on some cut-rate internet outfit. Oh, and the prices were about the same I'd have paid on the internet- and I have it in hand. Right now.

Off to make a neutrik bracket!

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In a bind

The manifold is done (well, except for the top plate, but that'll be glued on today). I've cut the 2x4 base which will mount to the existing rafters, but haven't attached it yet. I'm wondering if I should spread the load across more than two rafters? We're talking 80# of drivers plus 50# in the manifold itself... I think I'll just tie the rafters together with some 2x4 to help balance the load.


I've decided to do a reversed and standard speakermount to make the manifold more compact up in the attic space. What this means is that one of the speakers will have its (+) and (-) the opposite of the other, so that when one moves 'forward', the other moves 'back'. The net result is that both move 'in' to the center of the manifold.

Because of the large power needs for drivers this size, I'm really considering having a speakon connector bringing the power up to it. The EP2500 already has a speakon output which can send up both channels. I could install a speakon jack at the manifold and wire from there.NL4FXNL4MD-H
At the manifold, there's a second issue, which is that I need to get one pair of wires to the inside of the carefully-sealed box. I was thinking of using speaker binding posts, but they need to go through 1.5" of MDF, so I may just drill a tight hole and thread the wires through it.

I'll head to the speaker store today to see if they have the neutrik connectors.

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Thursday, September 20, 2007

Construction Pics


Not too far off from the google sketch. Notice how it was done so that the bottom could fit into a 2x4 frame. And the top is made to have two layers as well, with one over the other.

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Magnififold

The cuts have been made, even though I seem to be a bit lacking in my measur(twice, cut once)ing ability. I've got it quasi-assembled, but I need to get it cobbled together because I have to cut out the speaker holes for mounting. The Jasper Jig that I have is fantastic (we already used it for Andy's), but can only cut about 3/4" due to the router clamp hitting the wood if I set it deeper. So, I have to drill the pilot hole through both pieces of MDF, then do them separately (or they could be glued, but have to flip it over.

Here's another sketchup of it:

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Tuesday, September 18, 2007

Big Speaker


Yes, they are! The Ficaraudio Q18s are here and they're huge! I need to work on the manifold. The clever hinged design is having me really work at making it large enough to be a big enough output so there aren't compression artificats. The speaker area is about 375 square inches, so I need at least that in my manifold output to the room. The current cutout is 15x22, which falls short. I don't want to screw with cutting joists, so the 15" is fixed as that is the distance between them, so I'll have to get wider- which doesn't help the issue.
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Monday, September 17, 2007

IB excited

Pardon the pun... my Q18s have arrived. They're huge! And heavy. I'm working on the box design right now. I'm going to use doubled MDF. Here's a quick google sketchup...

What is going to be interesting about this is that I'm going to mount the box on hinges to give me attic access. It's proving to be challenging, but fun at the same time. Stay tuned.

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Saturday, September 01, 2007

This one goes to 18!

I'm paraphrasing Nigel, but it is really Derek Smalls who would appreciate the new bass. I've ordered a pair of Ficaraudio Q18s.

They're beautiful.


I'm getting them custom-built for HT, which means that it'll have a single voice coil, 4Ohms. This monster has 27mm of Xmax. I've sold the Tempests to my neighbor who is inspired
by my HT and is building his own. Fortunately, we've found a place where he can put them in a line array- which will be very cool. Though I think he needs even more of them- a line array needs to be like 4!

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Monday, June 11, 2007

IB upgrade

My tempests went belly-up. Maybe because they were being over-driven, but I never heard the "you'll know when you hear!" sounds of impending doom.

One thing would be to replace them with 4x15s instead of the pair of them. Thing about that- my manifold location- the proper location of being centered and in the front of the room- is limited for room. For me to crawl past the speakers, I would have to move it to a non-ideal location.

So, the other option is to go bigger. I like the sound of that. Using a spreadsheet listed on the Cult's website, there is a rating of cost-per-liter of air. I'm leaning towards the Ficaraudio.com Q18s, because the winner- the Chinese-made Mach5s are still unproven (and not much better priced).

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Friday, May 19, 2006

IB Sub and The WAF




One of the obstacles to true enlightenment in the audio-visual realm is the WAF. The Wife Acceptance Factor. All guys know that the correct-sized speaker is actually floor to ceiling. This ideal speaker should also have spikes and razor sharp edges to keep people from getting to close (for their own safety). A well-designed speaker will also have lots of LED lights which blink depending on which of 17 different crossovers are activated (floor to ceiling, remember- you think it'll just be a 3-way?). Even the audio purist wants these LEDs because he'll just close his eyes when listening to music. These speakers, since they'll last a lifetime, should cost the equivalent of a college education.


But, that's when the WAF comes in. The Wife will often talk about insignificant topics like decor, and style- they'll even go so far as to complain that the spikes and razor edges on the speaker are a (get this) hazard to guests, children and pets (when you very well know, it is the speakers that are at risk!). Then we hear about budget and that the equivalent money of a college education should actually pay for college!

This 'WAF' is the reason most guys end up with a pair of bookshelf speakers meant to look like a potted plant or other such nonsense.

Which brings us to the IB sub. This is one place that you can do what you want... since the speakers are outside the actual viewing area- the Wife doesn't know that there's actually 12 drivers in the basement. Or that one of you speakers is bigger than a CRT projector. As far as cost- you can start for pretty cheap- just build your manifold to hold the number of drivers you want and then add on. The cost is better than a lot of box subs- which *violate* WAF because they take up space in the room. And, when building it, you're doing stuff around the house. Oh, and you can put all the LEDs on it you want. But, as shown above, it'll probably have a cover over it.

In my case, the whole WAF thing is false. Stefanie wanted *bigger* speakers in the living room. I was going to move the speakers that were there into the home theater, but they weren't big enough so we had to get new ones. Here she is making the grill cover for the IB opening.

What we did is just put up some trim around the outside of the manifold. Then we took some rounded trim and made it slightly smaller than the outside diameter. To keep it stiff we glued small strips of wood behind the corners. I picked up some aucousticly-transparent speaker cloth from a local shop. Steff is shown stretching and stapling it to the frame. Start from the center and work to the corners to keep it taut. We're going to finish by putting velco on the frame and cover just in case I do want to install and see LED lights.

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Thursday, April 27, 2006

Infinitely Baffled wiring

When you build your own sub, there's a lot to it. Phase delays, sound pressure levels, cabinet volume and construction are just the start of it. When you get into multiple drivers, it gets even more complicated.

In my case, I'm trying to figure out how to wire my speakers. I have two of them. But.. each of them have two voice coils each of which is 8Ohms. I can wire them in series, which would make them 16 total. I can wire them in parallel, which makes them 4. But- I have two speakers to wire, so the choices continue- I can make them parallel or series too- so depending on how I wired the voice coils, that could make them as low as 2 Ohms, or as high as 32.

Throw into the mix that my amp has three modes- stereo (two inputs, two outputs), parallel (one input, two outputs), or mono (one input, one output) and can delivery scary amounts of current, I need to make sure it is done right.

And finally, I may add two more drivers later which add into the conundrum. I've been consulting with two of my friends whom I consider experts, and they've given two different answers as to how to meet my needs.

The good news is that my amp is flexible enough to drive 8 down to 2 ohms, so I have a lot of choices.

Mr. Stocks sent me this diagram, which is the way I'm headed. I only want to climb into the attic once more to wire it (kind of unpleasant to be up there with a soldering iron).


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Monday, April 24, 2006

IB Sub

After reading the prose from "The Cult of the Infintely Baffled", I decided to drink the KoolAid and go this route. What you see here is the manifold that will hold two Adire Tempest 15D8 subwoofers. The box is made of MDF and will be braced and painted. Steff wants a speaker cloth to cover it so it isn't seen from the main room. The speakers are dual-voice coil, 8 Ohm high-excursion speakers. I'm going to wire the voice coils in parallel, which takes the resistance down to 4 Ohms. At this point, I could then series the two speakers to drive them back to 8 Ohms with a monoblock amplifier, but Mr. Stocks recommended I use parallel outputs of my amplifier and send 4Ohms to each. I still need to order the amp, but I'm going to go ahead and wire the speakers up and get everything ready.

-frederick

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