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  1. #101
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Flat baffles require asymmetrics to sum right. 2nd woofer, 3rd tweeter. You will have to tweak some values....

    Later,
    Wolf
    "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
    "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
    "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
    "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith
    "We don't just make a crossover, we make a statement!" - Lawrence Fishburne for Cadillac

    *InDIYana 2014 event*

    Photobucket pages:
    http://photobucket.com/Wolf-Speakers_and_more

    My blog/writeups/thoughts here at PE:
    http://techtalk.parts-express.com/blog.php?u=4102

  2. #102
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by Wolf View Post
    Flat baffles require asymmetrics to sum right. 2nd woofer, 3rd tweeter. You will have to tweak some values....

    Later,
    Wolf
    Ah, more good information. I suspect my crossover is OK but the model is inaccurate. But I need to be able to model accurately so I'll go back and measure again and start over. Just to be sure I want to take a nearfield sweep on axis for each driver, correct? Or do I want a 1m gated response. I think I can gate down to about 300hz in my room.

  3. #103
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by Wolf View Post
    If you extracted the phase, it's right if you measured on individual axes. If you measured on one axis, then your off-axis summations are wrong anyway.
    Wolf
    I set up and re-measured both. Woops, I need to go read more on taking measurements and phase. It's not PCD or the drivers it's my phase measurements, I can't even reproduce the same phase curve between measurements. I may have to use ARTA and my other MIC so I can use a gated impulse response with phase corrected (excess phase I think). I'll figure it out.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  4. #104
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Never mind... Figured it out.

    I went with a third order on Woof and second on the tweet. Phase lines up from about 400 to 7K or so and bass sounds much tighter and more refined. Less nasal quality and more clarity and depth. I'm getting there, a little at a time. Thank you to all who have put up with my frantic nonsense and over sharing. I thought I knew what I was doing, now I realize how little I really do know about designing a speaker.

    I still think this tweeter has a HF edge to it. It's got to be inherent in the tweet as it's been here the whole time. That or my Yamaha surround processor is the source. We'll see about the ring version.

    After listening more I definitely notice a difference in the bass and midrange. It sounds much more accurate. Voices sound strong and dynamics are better than before. I'm sitting here thinking "Majestic", that's how it sounds to me, this speaker sounds "Majestic" and I like it now. I still hear a slight rough edge to the top end though. Maybe there is a filter I can apply to clean it up a bit.

    Last edit, I'm not sure if this is a good thing or not but this incarnation sounds quieter but louder at the same time. YPAO (yamaha PEQ setup) sets the volume at -4 compared to the satellites but it doesn't sound as loud as the satellites, however, I can hear more detail. Voices are clearer and bass sounds much more defined. I can turn it up much louder without feeling like it's too loud. Weird loudness thing. Is that a symptom of better phase alignment?

    Oh and H a p p y N e w Y e a r !
    Last edited by siggma; 12-31-2012 at 10:34 PM.

  5. #105
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    Default Re: Parts Express Low cost DIY Home Theater Project

    I love to write when I find something interesting or learn something new. The topic is relative vs absolute phase and phase distortion. I just found this link http://sound.westhost.com/ptd.htm. It's an article on Phase and distortion in filters and as it applies to loudspeakers. Applying it to my design it actually looks pretty good. I'm asking this 5" driver to cover 5 octaves from 80 hz to 2.4Khz. I'm also asking the tweeter to cover another 4 octaves from 2.4Khz to 19.2Khz. That's actually a wide range for any driver so if it sounds good it attests to the reasonable quality of the drivers themselves. The woofer will be producing greater quantities of inter-modulation distortion if it's allowed to operate much higher than 2K so a crossover point of 3.3K is not a reasonable goal for this, or any other 5" driver. To really get it out of the mix it probably needs to be crossed as low as 1K. However, there aren't many small, inexpensive tweeters capable of covering the 6 octaves necessary to fill the gap from 1K to 20K or so. In any case, the article makes pretty clear that relative phase is more important than absolute phase. Absolute phase being the arrival time of a signal in it's entirety and relative phase being the arrival time of a signals harmonic components. Since I'm beginning with a tweeter that sits more than 1/2" behind the woofer it's a wonder I've been able to align it as well as I have. I just ordered enough parts to finish this project including replacing the test box baffle, so my next challenge is to try to get that 1/2" negative alignment in time between tweeter and woofer to something more manageable, if possible. I flush mounted the woofer but not the tweeter which went the wrong way. I also mounted the tweeter on the edge of the baffle, another "not so good" an idea. It reduces the area on the baffle for the tweeter to "work" against increasing baffle diffraction losses. Next baffle I will flush mount the tweeter and surface mount the woofer, reducing the 1/2" misalignment to 0, or very nearly. I suspect that will make it easier to align phase and hopefully I'll be able to align it over a wider range. In any case, phase alignment from 400 Hz to 7Khz is still pretty good so I feel better about my now lopsided single speaker.

    I'm very thankful to Wolf for taking the time to point out where i was wrong so I could dig in and begin to understand what to do about it.
    Thank you again.

  6. #106
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    Default Re: Parts Express Low cost DIY Home Theater Project

    It could be tweeter distortion from not being steep enough. I'm betting 2nd woofer, 3rd tweeter will work, you just didn't give it a chance.

    Later,
    Wolf
    "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
    "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
    "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
    "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith
    "We don't just make a crossover, we make a statement!" - Lawrence Fishburne for Cadillac

    *InDIYana 2014 event*

    Photobucket pages:
    http://photobucket.com/Wolf-Speakers_and_more

    My blog/writeups/thoughts here at PE:
    http://techtalk.parts-express.com/blog.php?u=4102

  7. #107
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by Wolf View Post
    It could be tweeter distortion from not being steep enough.
    Yea, it could and I'm thinking about that and listening but if it were tweet driven through resonance or too low it would get worse with volume and this sound I'm hearing does not. Either it's digital broadcast distortion or my Yamaha surround processor is not as clean as I think it is.
    I'm betting 2nd woofer, 3rd tweeter will work, you just didn't give it a chance.

    Later,
    Wolf
    How can you say that. I fiddled with third on tweet for 3 days?
    You could take a few minutes and show me if you have the inclination and time. I zipped up the files necessary HERE. It would be demonstrative only as I'm not going to use this baffle. Woofer offsets are H=0, V= -.1016, Z= -.0143. SPL is only really accurate to 1K, below that it fluctuates too much to be accurate.

    Second on the tweet gives me a second order Bessel slope and actual crossover is up around 3K now so it should be attenuated enough to prevent bottoming or distortion. The driver lines intersect at 3.8K but I don't think the actual crossover point is that high. I think it's more like 2.8K. That woofer does not like to roll off easily. At least not where I'm trying to get it to. It seems to like to roll at 2K and again at 4K but in between it resists.

    I fired up ARTA and took some more measurements and while the SPL data is wrong (mic calibration issue) the phase is much more correct and it works much better with a 3rd on the tweet and second on woof. Is there any way to verify the actual phase data for each driver? It makes sense that if relative phase measurement is correct then the summation should match finished product measured phase. The only way I can think of is to physically cover each driver in turn and take measurements, unless anybody knows of a better way?

    I think the root of the problem is the z axis difference between the drivers due to the way the tweeter is mounted. While I doubt 1/2" offset is uncommon, in this design it's just stupid and wholly unnecessary. To make it worse the tweeter overlaps the woofer frame creating a small pocket of air inside the frame that I'm sure is resonating in an unmusical way. I may also have a small air leak where the tweeter actually mounts. The area between the two openings is very thin. I had to build it up with glue and glob it with silicone to get it to seal. Now that I know where the drivers line up acoustically, or at least where they overlap around crossover region in terms of phase, I can re-mount the tweet so it's very near 0 offset across that region just by flush mounting the tweet and surface mounting the woof. Or make it even easier and surface mount both.

    Anyway, Happy New Year!
    May this year be as productive as all those that precede it.
    Last edited by siggma; 01-01-2013 at 11:03 AM.

  8. #108
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Well, I revamped the original enclosure and made a second one. I cut the front off the box I had and made a new baffle. This time I centered the tweet and moved it down where it should have been in the first place. I also sprayed the interior with Quiet Kote and it makes quite a difference. This baffle has tweeter 15mm in front of woof rather than 22mm as before. Phase aligns easier and should be closer together. The Quiet Kote might preclude the need for stuffing of any kind. I'll see. This project is getting better and better the more I work on it.

    Pictures below:
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ID:	32298 New baffle with round over finished. You can just see my cardboard temporary crossover in the background.

    Can't seem to get the last picture to upload. Maybe picture limit. Boxes are gluing up now. Will start taking measurements tomorrow if there isn't any strong odor from the Quiet Kote. Don't want it to melt any driver parts. Cursory modeling indicates the changes I made will cross phase aligned LR4/B2 with 4 only components and an L-Pad. Will see tomorrow.

  9. #109
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by Wolf View Post
    It could be tweeter distortion from not being steep enough. I'm betting 2nd woofer, 3rd tweeter will work, you just didn't give it a chance.

    Later,
    Wolf
    That sound I was hearing is signal distortion. I added a TOSLink cable and switched from HDMI and it sounds better. That means there were data errors occurring over HDMI, the Directtv processor sends a different version of the signal over HDMI or the TOSlink uses different conversion hardware in the Yamaha. In any case part of the problem was signal.

  10. #110
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Looking good siggma.

    The TT forum might (???) limit the number of attachments to five JPG's per post. Just continue with a new post and add the rest of the pics.

    I can't quite see the orientation of those crossover coils. Can you get a picture of it for us? I want to make sure you've got them oriented OK. It's not enough to be orthogonal, they need to be the the "right" 90 degree orientation. thanks.

    Did you experiment with the tweeter's location? It might be too late for this advice, but I've learned from previous speakers that varying the tweeter's distance to each of the three baffle edges can smooth out the diffraction a bit. Even 0.5" to the right or left of center is enough to make an improvement usually. (I typically try to make those three distances different... e.g. tw to left edge=4", tw to right edge=3", tw to top edge of baffle=5") There are some diffraction simulators online that will show you the effects of this.

    Keep up the good work!
    Last edited by ReissM; 01-10-2013 at 12:22 PM.

  11. #111
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by ReissM View Post
    Looking good siggma.

    The TT forum might (???) limit the number of attachments to five JPG's per post. Just continue with a new post and add the rest of the pics.

    I can't quite see the orientation of those crossover coils. Can you get a picture of it for us? I want to make sure you've got them oriented OK. It's not enough to be orthogonal, they need to be the the "right" 90 degree orientation. thanks.
    Click image for larger version. 

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ID:	32322 Not the best arrangement. Now that I have a place to work I can make better temporary boards. I really need to get a dual connector cup so I can do it from outside the cab.

    Did you experiment with the tweeter's location? It might be too late for this advice, but I've learned from previous speakers that varying the tweeter's distance to each of the three baffle edges can smooth out the diffraction a bit. Even 0.5" to the right or left of center is enough to make an improvement usually. (I typically try to make those three distances different... e.g. tw to left edge=4", tw to right edge=3", tw to top edge of baffle=5") There are some diffraction simulators online that will show you the effects of this.

    Keep up the good work!
    Thank you. I rented a 15'x15' storage unit directly below my kitchen and bought a reconditioned Ryobi router table for $79 with a vacuum port! YES! My Rainbow will fit nicely on that little jewel and will make routing livable in such a small space. I need some safety glasses and some ear plugs and I can get a 1 HP 10" table saw for under $100 and build my own cabs. That opens the door for much better cabinet designs at my leisure.

    As for the baffle, I modeled it in Jeff's diffraction sim before deciding where to move the tweet. The high (on edge of top) position wasn't a bad place, it reduced on axis diffraction a lot but really messed with off axis response. Huge 20db peaks and dips if I recall. After thoroughly modeling it I decided on a slightly asymmetric location in the upper third of the baffle. I want this to have symmetric off axis response and it should favor below axis response ( it will be mounted close to a wall up high) but since I don't have much experience with crossover yet I don't know what I can iron out with crossover later and what I can't so this will be a learning session. Centered L/R and 8 1/4" from bottom on 11 1/2" baffle produced the most stable response over the entire range but does produce some moderate ripples. I'm not sure how to go about dealing with diffraction ripples. They "begin" below crossover point so reducing the source peak should reduce the ripple effect.

    I was going to flush mount the woofer but I don't think that will reduce the diffraction and it will effect time alignment. In fact it might increase diffraction having the woof flush. I get very little ripple on the woofer measurement or sim but a huge 6 db peak at 1.5K that wasn't there before on the tweet. With this new tweeter position the tweet is actually 2 mm ahead of the woof when measured on tweet axis. That will definitely help how it sounds, regardless of FR ripples.

    I'm going to try to take measurements outside soon as it quits snowing. This is my porch. If I place the speaker on the corner of the railing there on the landing facing the stairs on the left in the picture and put the mic under the stairs I should be able to gate down to 150Hz, maybe lower.

    Click image for larger version. 

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    Tom

  12. #112
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by ReissM View Post
    Looking good siggma.
    Question, a little off topic but relevant.

    I got my gaggle of AC-130MK2 (Aurum Cantus AC-130MKII) woofers and set up two on my bench to begin breaking them in. I'm running them at 50hz with about 1 watt of power for a couple days. I played a little music though them and noted right away they have much, much better dynamic response. Even with a 50Hz sine running away I hear no inter modulation distortion at all. I didn't even realize it was flapping away at 50z. I also note sharp very crisp drums, a transparent sound like the speaker disappears and very clean midrange voice plus very good efficiency. So I poke a mic at one and take a measurement. They look nothing like the advertised response. There is a large wide 6db peak centered about 2K that has me thinking "crossover hell". I'm assuming different come materials have characteristic peaks and dips. This is a Carbon Fiber / Kevlar cone that, being stiff and light, most certainly has breakup modes. The second breakup mode I note right away is way up at 12-15K so it's not going to be an issue. But having a large peak right at or near crossover is worrisome to me. Could this be an actual breakup mode or is there some other reason I might see such a peak? A 2K wave is 6.6 inches so logic tells me it can't be a cone breakup mode, the cone is only 5" in diameter. What else might cause such a peak?

  13. #113
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Take a quick peek at the XO layout in the attached picture:

    Click image for larger version. 

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    You've got L1 (red) interacting with L2 (green).

    I made a version that attempts to minimize the coil interference. By laying L1 down, the arrow would be coming out of the page. In my version, L1 and L3 will not interact at all. L1 and L2 will not interact at all. L2 and L3 are physically as far apart as possible, and orthogonal to each other. L2 and L3 still have a small potential to interact, but this is about the best that you can hope for with these 3 coils on this size XO board.

    The two smallest coils are the only ones with potential to interact, and they are physically separated as much as possible. What do you think?

  14. #114
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by siggma View Post
    ... So I poke a mic at one and take a measurement. They look nothing like the advertised response. There is a large wide 6db peak centered about 2K that has me thinking "crossover hell".
    Well, maybe not. Cone breakup can be addressed with a fairly simple "tank" circuit.

    What box volume, and baffle width did you use for your acoustic measurement?

  15. #115
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by ReissM View Post
    Take a quick peek at the XO layout in the attached picture:

    Click image for larger version. 

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    You've got L1 (red) interacting with L2 (green).

    I made a version that attempts to minimize the coil interference. By laying L1 down, the arrow would be coming out of the page. In my version, L1 and L3 will not interact at all. L1 and L2 will not interact at all. L2 and L3 are physically as far apart as possible, and orthogonal to each other. L2 and L3 still have a small potential to interact, but this is about the best that you can hope for with these 3 coils on this size XO board.

    The two smallest coils are the only ones with potential to interact, and they are physically separated as much as possible. What do you think?
    When I get to a finished version I plan on using pegboard or hardboard drilled for screws with stand-offs. I'll make two separate boards, one about 2.5" wide by 5" long or so and the other about 3" long. Then I can mount them both on the bottom about 4" apart.. But this was a temporary cardboard crossover and I don't think the small coil was even part of it. Having said all that I didn't think of turning the big coil in that direction. Looks like the woof will be two components and tweeter 4 or 5 including two resistors, unless I do a zobel or add a contour network. I'm wondering if the tweet peak is resonance peak.

    Click image for larger version. 

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ID:	32324 This would be my final layout on pegboard. I don't want to make all the little holes so I made this in Openoffice Draw.

  16. #116
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by ReissM View Post
    Well, maybe not. Cone breakup can be addressed with a fairly simple "tank" circuit.
    How could it be cone breakup that low? It's probably not anything to do with actual peak. I just realized it wasn't on a baffle at all...
    Duh...

    But that brings up a good point. Is it acceptable to take measurements on the finished baffle? I would think it's preferable but I've read that it should be measured in a baffle, preferably an infinite baffle. I've been taking measurements on the box while it sits on a small ceramic pedestal. I drape a thick bath towel under it to reduce reflections and it seems to work. I can usually get a flat impulse to about 200 Hz. The first reflection is usually the wall right next to it. Is there a better way to measure for crossover?

  17. #117
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Actually, I'd like to go over the entire measurement and crossover design process and get some feedback. If this project had a strict budget I wouldn't suggest notch filters to contain FR peaks prior to applying a crossover topology but in this case I don't have a strict crossover and component budget and I really need to learn how to design various types of filters. The Carbon/Kevlar drivers I just purchased are considered some of the most "transparent" sounding drivers made. They are also known to have difficult modes to control and contain and I'll be trying to build a top notch crossover with very little practical experience. [Lynn Olsen, The Art of Speaker Design]

    My design thinking runs like this:

    1. Take a set of gated measurement that can be repeated and are accepted as accurate representations of the driverd to which the crossover will be applied.
    2. Note any peaks and dips in the overall response and, if possible, identify their source. Are they baffle diffraction? Are they cone breakup modes (internal cone resonance)? Are they electric in source?
    3. Decide which modes can and need to be corrected by a crossover in order to produce a workable finished product.
    4. Develop appropriate filters to contain resonance modes first and re-measure to be sure they are appropriate and work as expected.
    5. Apply target crossover filters and integrate and simplify existing filters if possible.
    6. Build temporary crossover and listen to speaker noting any issues that might have been missed.
    7. Concatenate any dual parts used in temporary crossover and build final crossover version using permanent components.
    8. Listen and Listen and Listen some more...


    I could use some comments on taking measurements. I know there are many different sources for varying opinions on the topic but I'd like to hear some personal experiences on where, how and why specific measurements are taken. Thank you in advance. I appreciate your time and your willingness to share what you've learned.

  18. #118
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Quote Originally Posted by siggma View Post
    Is it acceptable to take measurements on the finished baffle? I would think it's preferable but I've read that it should be measured in a baffle, preferably an infinite baffle.
    Yes, in fact your measurements will include baffle diffraction effects if you use the actual baffle/box to take all of your measurements. That's a good thing.

    It's possible to do it the other way and then simulate the baffle diffraction from your particular box... but why simulate something that you can just go ahead and measure? (Not everybody has the capability to measure, so they take the other route and simulate as best they can.)

    Both methods work... measuring is easier if you have the tools.

  19. #119
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Good morning. Following my outline I measured and noted a peak at tweeter fs. It's probably baffle diffraction but it's right at tweeter resonance. Since I can't crank it down with crossover I decided to try an LRC to invert it and it works. It allows the crossover to get that peak down to something reasonable but it requires a rather large inductor. Since it's a dual slope filter it requires three components unless I'm missing something. Is there another way to grind down such a peak?

    I've been working on this for a couple hours now and finally I got slopes that produce a deep V with inverse tweet and decent response when normal polarity. If I change any of the components more than a little bit the phase changes and It won't track plus the deep V disappears. It's very sensitive to changes. Impedance looks OK, I didn't push the phase button but nothing wild going on in system electrical phase and only 9 components (including LRC at tweet fs). I'll see if I can edit and add the system electric phase.

    I also modeled vertical off axis response and it's very good both above and below for at least 20 deg. Horizontal off axis models very flat as well. Now to find parts to make the actual crossover.

    Woof second: 1mh, 9mfd cap
    Tweet third: 8.5 ohm series, 2.64 mfd, .25 mh, 6 mfd
    Series LRC in parallel: 14 mfd, 5.16 Ohm, .97 mh

    Is this OK?


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    Electric phase:
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    Getting better I am...
    Last edited by siggma; 01-11-2013 at 01:32 PM. Reason: comment on axis response

  20. #120
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    Default Re: Parts Express Low cost DIY Home Theater Project

    Finished up the second enclosure and sealed it up with foam gasket tape. It's so airtight I can push on the cone for 5 seconds and it takes that long for the air to escape. The cone comes back out in about 2 seconds which means it barely seeps. Probably from the foam tape. I've seen speakers that are so airtight the cone over extends at high altitude.
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    I thought up a grille last night. I'm going to sand and paint the enclosure satin black then make an oval ring out of 1/4" hardboard to cover the tweet and woof only. I can mount it with rubber cup and pin anchors so it's easy to remove if desired or if it sounds different. Gray in the image is the grille, I have some nice black grille cloth. Looks like I'll get good use out of my new router table after all.

    Maybe I'll paint them white with black grille instead so the grille stands out more. That would look better and more "artistic" than just black. Then they'll be neutral in color and much more unique. Yea, the black on white will be much more distinctive.
    Click image for larger version. 

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    More shameless overshare. Note the open cup of rat food on the stove, it's for my little babies toe-less Jack Jackson (white) and Mr. Bones (black) my pet rats. They like music too and they can hear much better than I can.
    Click image for larger version. 

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    Click image for larger version. 

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    Last edited by siggma; 01-11-2013 at 06:31 PM. Reason: rats

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