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Old 30th November 2012, 01:59 AM   #131
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Wow! Nice job Cal.
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Old 30th November 2012, 05:18 AM   #132
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Its annoying me that i cant post pics but im very much enjoying watching u guys progress nicely. I havent sealed my lid yet coz i wan to put an amp inside but so far im not happy with the response down low. Its a pretty steep cutoff bass wise. I pretty much haelve to eq 100hz right out to get it sounding like it has anything below that.

Now in saying this what im aiming for seems to be breaking the rule of speakers. Its small and loud. If i want bass it wont be loud... And ive proven this today...
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Old 30th November 2012, 09:57 AM   #133
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Originally Posted by klampykixx View Post
Its annoying me that i cant post pics but im very much enjoying watching u guys progress nicely. I havent sealed my lid yet coz i wan to put an amp inside but so far im not happy with the response down low. Its a pretty steep cutoff bass wise. I pretty much haelve to eq 100hz right out to get it sounding like it has anything below that.

Now in saying this what im aiming for seems to be breaking the rule of speakers. Its small and loud. If i want bass it wont be loud... And ive proven this today...
Describe in words what your box is, dimensions, placement of drivers, location of terminus, etc. Stuffing 4 drivers in same box may be the biggest problem, you may be getting phase cancellation issues. Some browsers upload pics better than others. Chrome on Android doesn't work, but Firefox does. Make sure you use advanced post reply and not quick reply.
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Old 30th November 2012, 10:19 AM   #134
xrk971 is online now xrk971  United States
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Originally Posted by Cal Weldon View Post
Second spiral done.

I've been thinking of the rough edge on the foam. It was easy to deal with it with the hot glue but not so easy when add the fronts so I have an experiment I am trying. I am gluing the top edge with yellow glue then adding a thin strip of regular writing paper over that to act as a surface tensioner to hold the glue. Then I turn the whole thing over on a flat surface and weight it. I am hoping this will give me a flat surface to glue to. I am trying the same experiment with masking tape in place of paper. I realize this sets me back a day but what the heck, a week ago I wasn't going to be doing a build until the new year so...
Cal,
I forgot to say what a fantastic job you did with regards to accuracy - the design looks spot on. Your idea of reprographics worked out really well. I noticed that you mirrored the geometry for left and right. I actually did the same thing to make sure the sound was balanced coming from periphery. I am not sure if it matters but I am aligning the longer path channels up/down to get the bass enhancement from the ceiling/floor for the deepest bass notes. Great job! Can't wait to see these babies capped off!
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Old 30th November 2012, 10:21 AM   #135
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Its not that i cant or dont know how to upload im on very limited cap on my phone. Here is the best pic i have for the moment.
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Old 30th November 2012, 11:57 AM   #136
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Originally Posted by klampykixx View Post
Its not that i cant or dont know how to upload im on very limited cap on my phone. Here is the best pic i have for the moment.
Klampykixx,
Interesting design, glad you were able to get us a picture. Am I correct in assuming that this picture shows 1/2 of the box only with the two drivers loading a pre-chamber that has a channel that leads to the mouth which then goes past the faces of the drivers? You mentioned that you tested it prior to capping it with the lid using glue since you wanted to put the amp inside. Until you glue or seal the channels air-tight, the performance will be very poor - not even close to what it could be. The reason is that the smallest leaks will collapse the establishment of the fundamental standing quarter-wave which is where you get your bass boost from. If your path length is 73 cm, this gives an approximate fundamental tuning frequency of 117 Hz (assuming speed of sound is 342 m/s). If you cap the lid off properly with glue, you should get a good amount of bass at 117 Hz or close to 100 Hz.
A couple of design considerations to think about: (1) what is the effective piston area (Sd) of your two drivers combined and does that area equal the throat area leading from the pre-chamber? You can trim the foam-core board to make this so if it is too small, this will let the horn "breathe" better and increase the bass; (2) make a cutout panel on the side to install the amp and have access to it after the lid is on (inevitably, you will need to access your amp for connections or to debug); (3) Use lots of stuffing in the pre-chamber and some loose stuffing on the snaking channels to absorb the reflections and higher harmonics otherwise you may end up with lots of distortion junk coming from the horn besides the bass; (4) add some bracing in your pre-chamber to keep it from flexing under the pressure of the two-drivers. If you haven't already, download and read MJK's papers on horn theory and back loaded horn design (htpp://www.quarter-wave.com) - very helpful info.
Good luck and keep us posted.
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Old 30th November 2012, 12:56 PM   #137
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This thread is awesome! Inspiring and interesting.

Please, more photos !
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Old 30th November 2012, 01:38 PM   #138
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Originally Posted by xrk971 View Post
I like the Pentagon, how does that sound? Must be great for parties.
I use it at home. So handy to be able to move it around. If I need an all in one for a party, I use the red 'Toolbox'. It has much more gusto.
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So you are building a glue fillet on paper
Changed my mind again. While I was counting sheep, I got distracted. I am thinking if lay a bead of glue on the foam, place the baffle over that and then remove, I will have an outline of the glue on the baffle. I can turn that face up, lay a heavy bead right on the baffle and place the spiral face down into it. That way I may end up gap free.
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Originally Posted by cochleus View Post
Wow! Nice job Cal.
Thank you, it's been fun.
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Cal,
I forgot to say what a fantastic job you did with regards to accuracy - the design looks spot on. Your idea of reprographics worked out really well.
Thanks for the complement. I've found it really helps to learn from the experience of others and then take the time to see how it all works before getting started. Sometimes this means using up time and materials while you are testing or getting comfortable but it sure cuts down on the oh-uh's. One thing that comes to mind is the kerfing on the inside of the curve. I have done that with wood where you are removing enough material to create a bend but with a knife, I would think you would want the cuts on the outside. Not the case at all. Also using the rounded edge of the kitchen counter to form the curves was really handy. Just like rolling flat stock, a little at a time and after a few passes, you have a nice smooth curve.
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Old 30th November 2012, 03:48 PM   #139
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Originally Posted by Cal Weldon View Post
Changed my mind again. While I was counting sheep, I got distracted. I am thinking if lay a bead of glue on the foam, place the baffle over that and then remove, I will have an outline of the glue on the baffle. I can turn that face up, lay a heavy bead right on the baffle and place the spiral face down into it. That way I may end up gap free.
That is a good idea, saves you time too. This got me to thinking why not use some really thick glue to really seal those gaps - would industrial floor board cement from big caulk guns, etc. work (ideal since you are using floorboards for the faces)? What about RTV?

I read somewhere that there is a pre-scored masonite or MDF sheeting that allows bends called 'Bendyboard'. It may work well too but doesn't look so nice with all those slots. Yes, it is counter-intuitive which side to put the cuts on. It would work of course on the other side but you would expose the foam cracks rather than compress the foam where you need it and keep everything tight.
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Old 30th November 2012, 04:02 PM   #140
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Originally Posted by 6L6 View Post
This thread is awesome! Inspiring and interesting.

Please, more photos !
I just noticed the thread got moved to Full Range Speakers - I guess that is more appropriate.

I'm glad you like it, it has been a lot of fun and the encouragement from others has been great. I urge you to try the foam core builds for yourself. They are very easy, quick, clean (no sawdust), and can work satisfyingly well. A great benefit is you can do it on the kitchen table and don't need a workshop full of tools. If you have an X-acto, a ruler, a pencil, hot melt, some cheap foamcore boards, spare drivers lying around, and some imagination, the possibilities are endless. Jump in like Cal did - he is loving it I think. Then post pictures please.
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