Dynamic 4T kit build

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Dynamic 4T kit build

Post  Admin on Wed Jul 30, 2008 1:56 am

After all the cuts are made, here are the panels for a the towers. I used a pencil to outline where all the bracing will go.


Make sure you measure and remeasure a few times to get everything where it needs to be.


The front, bracing, back, top, and bottom are all the same width. I do this so that when I cut the wood on the table saw, I can do it all with the same setting on my table saw. The result is perfectly flush sides when they are ready to be glued down. The front and back are cut exactly the the correct height as well. And the top, braces, and bottom depth is also cut at the same time for accuracy.


Next I clamp everything together. I used a brad nailer to keep the bracing from sliding around and to keep it firmly in place. I'll never build a cabinet without it ever again. It makes cabinet building easy and fun because you don't have to worry about things slipping off square. Speaking of square, make sure the tops and bottoms are square using a T-square before you use the brad nailer! Then, the sides are clamped down. You'll notice that the sides are oversized a bit and overlap. I did that on purpose. I will later take a flush trim bit and go around the sides to square it all up. Then sand it smooth for a perfectly flush transition from front to side to back.


Here you can see the cabinet is all nicely trimmed with the sides perfectly flush. I used an orbital sander to do the finishing touches, so when I ran my hand over the edges I didn't feel anything that was out of level. Next I cut some holes in the first layer of the baffle. These holes were cut such that the outside diameter is the same size as the flange of the driver. So, for the RS180s, the diameter of the hole was cut at 7 1/8", and the TB W4 was cut at 4 15/16", but the tweeter was cut at 3 1/4" (smaller than the flange diameter). Note also that the midrange is offset 3/4" one direction and the tweeter is offset the opposite direction 3/4" from center. For Left and Right cabinets they are mirror imaged and I label each speaker "left" and "right" so I won't make a mistake later. I also label the "top" of each cabinet so when I go to cut ports, I won't put it in the wrong place!

To make the cuts for the driver cutouts, make sure you don't cut into the sides or dividing partitions that separate the mdirange chamber from the rest of the cabinet. I used my jasper circle cutting jig and only went so far, so I didn't cut into the sides or the partitions. I drew lines so that I wouldn't go past the line. Then, I cut the rest with a jig saw. Finally, I took a flush trim bit and smoothed everything out agains the side wall and partition walls.


Here you can see what I mean about the routing flush to the side wall and partition.


This cabinet is not done yet, but it shows you what it will look like after the first part of the baffle is attached and completed. Next I have to put the second part of the baffles on and flush trim that, like I did for the sides.


Last edited by Admin on Tue Aug 26, 2008 12:58 am; edited 8 times in total

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Re: Dynamic 4T kit build

Post  Admin on Wed Jul 30, 2008 7:56 am

Well I finished veneering the Dynamic 4T mains and 4CC center channel. I took me about 12-15hrs of glueing, ironing, trimming etc. Not too bad. Here are some pics of the process. I'll finish cutting out the holes for the drivers in the removeable front baffles tomorrow.

First I flush trimmed the front baffles after attaching them temporarily with brad nails. Make sure you label each Left and Right and where the top is located. I drove pilot holes so that I can line them up later.


I used a brayer to roll the HeatLock Veneer glue on the back of my Cherry veneer.


Since my baffles are going to have veneer, I trimmed them to the same width as the unfinished boxes. Here you see the Heatlock applied to the baffle.


The iron on process begins.




Front baffle all nicely trimmed. I'll cut the driver holes out later and open up the back of the baffle to allow airflow around the back of the driver.





Here's the CC getting veneer. I oversize the veneer a good 1" or so and use the veneer saw to trim it down flush. Then I sand it perfectly flat. Then roll the glue on the next side- rolling glue one side at a time until it's all done in this order: Bottom, back, sides, front, top. I roll the brayer towards the edge and start lifting it right before it gets close to the edge so glue doesn't get on the face of the veneer. If you are a slob, just use painter's tape to mask the veneer where you are rolling veneer glue.

So, to sum up the process I use: roll glue on MDF and back of veneer, hair dry it or sun dry it to the touch. Place veneer down with it 1" oversized or so, then iron it down with cotton Tshirt between the iron and the veneer. Trim the venner flush with the veneer saw. Sand the remainder flush. Repeat process for the next side.



About 4hrs to veneer one box. It would have been about an hour less if I didn't make the front baffle removeable.


More to come. I hope to get all the drivers holes cut out and chamfered tomorrow and apply the first coat of stain.

Should be on schedule for measurements early next week.

Jed


Last edited by Admin on Wed Aug 20, 2008 8:05 am; edited 2 times in total

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Re: Dynamic 4T kit build

Post  Admin on Wed Jul 30, 2008 7:56 am

Today I applied 2-3 coats of Watco Danish Oil in Cherry color. I have the option of going over it with a poly clear coat, which I will probably do in 3 days after it dries. This stuff went on really smoothly.

Here's the before and after shot with the far left cabinet showing the cherry before the first coat of finish.


Another shot of that:


Here's the front baffles:


And the cabinets with the baffles sitting in front not attached yet. I'll attach the baffles after I get the dampening materials in place.




After 2 coats of the Watco Cherry Danish Oil, I used 5 coats of Arm R Seal High Gloss wipe on poly. I sanded between coats with 320grit sandpaper.

In the kits I'm using 1/2 and 3/4" Sonic Barrier in strategic places. The 1/2" is used for the first 3" around the drivers, and the 3/4" is used for the rest (unless otherwise noted).


Here you can see the "steps" from 1/2" to 3/4" Sonic Barrier I used for the Center Channel chamber. The midrange chambers will later be filled with Acousta Stuff, with 3" of breathing room around the midranges.


The woofer chamber of the CC gets 1/2" Sonic Barriers on the left and right ends.





The towers get 1/2" Sonic barrier on the top and the bass doens't get any because that is where the crossover is going to be placed.


Here are some pics of the cabinets ready for driver testing.








Last edited by Admin on Tue Aug 26, 2008 4:19 am; edited 3 times in total

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Re: Dynamic 4T kit build

Post  Admin on Wed Jul 30, 2008 7:57 am









Last edited by Admin on Mon Sep 01, 2008 7:31 am; edited 1 time in total

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Re: Dynamic 4T kit build

Post  Admin on Wed Jul 30, 2008 7:57 am

Well I've spent a lot of time tweaking this design, and I'd have to say it exceeds my expectations. I much prefer the Dynamic 4T speakers to just about any box speaker I've heard.

The crossover topology is very elegant (proprietary) and the slopes result in flat transition form woofers, mids, to tweeter. I can't hear where one driver picks up or where one slopes away. The summed frequency response is incredible flat, among the flattest I've ever measured or designed. The thing that is nice is that the crossover doesn't use that many parts. I took a lot of time simulating the ideal baffle layout so that there wouldn't be many peaks and dips in the FR. Therefore, the response of each driver was flat before I began designing the acoustic slope transfer functions. The time I invested in the baffle research and development was well worth it, considering the final response I was able to get pictured below. Note this is smoothed but IN ROOM!!! Also, I didn't splice in the port response so take that into consideration. These speakers easily will play down into the 30s.



I tried several different topologies to get a flat response, but let us not forget the importance of an amplifier friendly impedance. The Dynamic 4T could have easily had a crossover that yeilded an impedance with dips into the 2.5-3ohm range, but with a few tricks I was able to get the impedance nice and flat, with a minimum never reaching much below 5ohms, and a fairly benign phase angle throughout.



The crossover slopes are unique. In the past I've been a bit of a techie while trying to get every little response variation taken care of with an electrical filter to smooth things out- usually resulting in LR4 slopes. That is not the case here. The crossover, even though minimal, effectily notches the cone breakup well below audibility. In the case for the RS180s, it is -60dbs down from the summed response. I measured the drivers outside, which minimized any room interference from original measurements. I also took measurements in room to compare with the outdoor measurements. Honestly, they matched up pretty well after I spliced the nearfield and farfield data, and only a resistor level change was necessary to adjust the final responses to be exactly the same, but it is always good to measure every driver in multiple ways, comparing data before finalizing a crossover design (Not to mention the countless hours of listening and tweaking the design to fine tune the response). I also measure the drivers after the crossover is in place to see if the crossover is doing its job for each individual driver, as well final system response. The below response is with the measurments that I did outdoors. There is NO SMOOTHING shown. I think it's important to see what's going on with the drivers' true responses. The slight 200hz peak is a measuring artifact and doesn't really exist in most rooms.



The power response is flat as well. Below are the predicted on and off axis responses:



Last edited by Admin on Sun Sep 07, 2008 10:54 am; edited 5 times in total

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Re: Dynamic 4T kit build

Post  TetraGrammaton on Thu Aug 21, 2008 2:36 pm

Looking good Jed. Once I create some space in the garage I'll be able to get started on mine. Where did you get the veneer from?

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Re: Dynamic 4T kit build

Post  Admin on Thu Aug 21, 2008 11:09 pm

TetraGrammaton wrote:Looking good Jed. Once I create some space in the garage I'll be able to get started on mine. Where did you get the veneer from?

Hey thanks! I hope to get the poly done or at least a good start on it today. It just depends how fast it dries in the sun, so I can get 5 coats on it. The veneer is from www.tapeease.com. They have the best prices and the quality is great. The glue is HeatLock that I get from www.veneersupplies.com, while you are there pick up a roller and veneer saw. Works great.

Jed

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Re: Dynamic 4T kit build

Post  TetraGrammaton on Sat Aug 23, 2008 2:08 pm

Wow those are looking awesome. I'll have to give it a try. Are you using the paperbacked stuff or something else?

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Re: Dynamic 4T kit build

Post  Admin on Sun Aug 24, 2008 1:22 am

TetraGrammaton wrote:Wow those are looking awesome. I'll have to give it a try. Are you using the paperbacked stuff or something else?

Yeah, the 10mil paperback from tapeease is what I'm using.

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