Official Rythmik Audio DIY Subwoofer Kit thread - Page 4

Masking tape, that's a nice tip! Thank's

Short update. I'm done cutting the panels and they are all put under pressure to be glued together to panels of 24 mm and 36 mm.


A short question about internal bracing. The cabinet needs two internal bracings. Can I use spare 12 mm panels or should the bracing be of thicker material?

In my buildlog at avforum.no, a couple of DIY'ers have replied to my Q about the bracing. Because the energy trying to move the outer panels is working 90 degrees on the panels, we (actually the other gyus) concluded that 12 mm panels for bracing is sufficient, and there will be rather small amounts of energy setting the bracings in movement. Even so, I think will add some kind of crossbracing between the bracing panels.

Anyway. Here's some pictures from todays work.





Testing to see how things will look and if they fit together. It looks ok.




As you might see, there's some inaccuracy on the panel edges, mainly because I have not been able to cut them absolutly perfect size, there's 1 or 2 difference between two of the panels. So I'm concidering cutting ~2 mm off each edge to adjust them. On my next project, I will cut the panels in rough sizes and cut them with more precision after they've been laminated.

Looking good! Are you using a table saw? When I cut a project, I'll generally have my supplier do the rough cuts, and then I cut to size on my table saw. I cut all panels that are going to be the same size at the same time, that way I only have to set up once, and they are all exactly the same. I would think the 12mm will be sufficient for the bracing. I'm no expert though

Thank's


I'm using a handheld circle saw as seen a couple of posts earlier. I would love to have my supplier do the rough cuts, but as I live in a small place I can't choose by many suppliers, there are only two and they don't have the equipment, nor the competance to do the job right, I'm sorry to say. Cutting many at the same time is a good trick, but again, because my saw is so small, it won't cut many panels at the same time. On the other hand, it might cut two panels (~48 mm) at once, I'll look into that tomorrow.

And in fact, this is my first real DIY speaker project, so it's more or less an experiment. So far I think I'm doing all right, all things concidered.

Yeh, cutting 2 at a time will help, and yep, you're doing fine. I always learn several new things on every project. That's half the fun

Another day of labour and learning in the garage

I decided not to adjust all the panels. If I adjusted one side, I'd have to accuratly measure and adjust the the adjacent panel, and the next, and so on, this would probably take quite a lot of time. Instead I test-assembled the panels and adjusted only the pieces that needed to be corrected. There were only three edges that actually needed some adjustment, and in fact only a couple of millimeters at most.

So parts of the cab is assembled with wooden plugs to keep the panels in the right posision and glued with polyurethane glue. I don't have big clamps and were not able to get some nearby, so I used straps and extra weight. So far it seems to do the job, the glue is foamed up and all joints look tight. The pictures were taken a few hours ago.





This is the rear panel. As you can see the panel is placed few millimeters into the box. I will use a flush trim router bit to ... well flush trim the edges.

Been doing some gardenwork the past couple of days, but some work has been done on the sub as well.

First I made a routerjig for the smaller circles.


The centertap is a small bolt fastened with a nut. When I drill the hole for the tap, I also drill a bigger hole for the nut.



Holes for the ports finished.




The ports are a tad bit wider than the original design of 3 - 1/2", mine is 100 mm (~4"). I'm considering altering the length og the tubes to match the original tuning frequency. In that case I'll have to add about 10 cm (4"), and I'll have to make a 90 degree bend at the back of the cabinet. If I use max length of 45 cm in this cab, the tuning frequency will be 19-20 Hz with one port closed. Will this affect the overall preformance of this sub? I'll might loose a couple og Hz in the low end?

I think I'd like to build something like that. Where did you get the pipe?

Tols1, I appreciate you sharing your build with us. Thank you.

I found mine for sale on Ebay locally, but you can source it from commercial plumbing supply houses. From what I found, it is btw $35-40 per foot which is why I looked around on ebay. Look for schedule 80 PVC pipe.

Greg

A word of warning for anyone who might like to try the PVC. I find that larger sizes of this stuff are not always perfectly round, so you want to cut the end caps large on the first pass, temporarily fasten them to the pipe and trim with a flush cut bit.

Greg

Minimum lengths of 10ft. Ouch! Maybe I'll stick with the sonotube.

You're welcome I have posted quite a bit of measurements in my "home"-thread at avforum.no. Right now our ISP is down so I'm browsing through my iphones wifi. As soon as I'm online again I'll post some here.

Ok, back online again. As mentioned I've done quite a lot of measurements, and posts some here. First of all I wanted to determine the difference in port tuning with 45 cm vs. 55 cm vents.








First I measured the port resonance frequency with one port stuffed and both open and 45 cm vent tubes. One port stuffed gives about 17 Hz, both open it's about 22 Hz. I'm a bit confused over this because theese are the figures I got when simulating 55 cm vents.


Measuring the driver gives this picture. Blue curve: both open, red: one stuffed and grey: both stuffed.


This is the driver and port measurements in one picture, 45 cm vents, one port stuffed. I have not adjusted the magnitude of the two signals.


So, what about the 55 cm vents? Well, I expect something is wrong, there's a leakage or something disturbing the resonance of the tube, because I did not expect anything like this. Here we compare 55 vs 45 cm vents, both open. Black is 45 cm, purple 55 cm. As we see, when both are open, the resonance of 55 cm is lower than 45 cm vents.


This is one port stuffed. Green line is 55 cm, blue 45.


I'm not sure what causes the difference in magnitude in these measurement, but I might have posisioned the mike differently or something. They are taken som time apart because I had to disassemble the side panel. I did have some trouble attaching the bends, because they don't actually fit the vent tubes outer diameter. Event though the tuning is not lower with 55 cm vents, they give more output at the lower frequencies At 12 Hz the 45 cm vents is down by 5,5 dB from it's peak at 17 Hz, but the 55 cm vents is down only 3 dB at 12 Hz from it's peak at 17,5 Hz.

Any comments?

Ok, last post from me for a while, as the sub is finished, exept for the finish of course. I'll be back with an update of that later.

All bits and peices are glues and screwd.


The internal flares are glued with PVC-glue.




Installed in the HT. The media rack is 50 cm deep and 50 cm high, for comparison.




This is in-room response after calibration, no smoothing applied. I have a nasty dip at 100 and 200 Hz and I assume this is caused by room nodes. Red is both ports open, green one port stuffed.


And the sound is of course magnificent. I assumed, before building that I had to sacrifice some of the quickness and transient response from the sealed cab, but I was wrong. In my HT this is as transient and musical as the selaed box. I've listened to some bass heavy tracks I know quite well: Infected Mushroom, Chris Jones - No Sanctuary Here, Yello - JuniorB, Pete Belasco - Deeper, and a few others. Especially the bass guitar on Chris Jones, it's easy to follow every fingermovement on the fretboard. On the Belasco-track, even the low-low notes are played with ease and undistorted at volumes I have not had in this room ever. Compared to it's closed brother, it seems this one's got a lot mote headroom. As expected of course.

So if you are considering building one of theese badboys, it's both thumbs up from me

Looks great! Congrats! I'm looking forward to seeing the finish.

Thanks. I'll keep you posted

@ tols1. Bow that you experienced an F15 and now have a FV15 clone then it would be good the difference in sound. How it compares musically and in movies as well. I was thinking in buying the F15HP but if the FV15HP can gives me the same sound quality in music as the sealed version then the ported is the way to go.

Javy-

Go up 3 posts

Best,
C.

As I posted earlier, I cannot not detect any difference in musicality and quickness in my setup. But I haven't had the time to analyze in detail, so this is my first impression after an hour or so of listening.

Of course others might experience otherwise in their setup, so I can't guarantee that you wouldent either. I suppose if you have front speakers with very tight and quick bass, OB, Magnepan or horns, the FV15 might intergrate different and the difference may be bigger. My front speakers are almost 20 years old Focal/JmLab DB26, and the bass is not very good on these. They have a slight boominess around tuningfrequency at 40-45 Hz, and this causes them to be a bit unarticulated and "one-note-bass"-ish.

I completly forgot to update you guys on the finishing job.

Here's some pics.







Still some sanding before it's acceptable.




First coat of the black stuff.





Finished.










Hope you like it. I'm absolutely satisfied with the result.

That is just awesome!
If you don't mind me asking...how much do you think you spent on materials? And would you mind too terribly listing what tools you used?

Also if I recall and understand correctly, Rythmik states that their servo technology would help or basically compensate for any build dimension differences from one build to another. Do you think that helped in your case?
I appreciate you letting us follow along in your build. Do you plan on doing another one?

Brian,

I'm considering the GR/370PEQ combo in a custom box. I want to know if the "fixed" 80Hz 12dB/Oct LPF is at all modifiable? My mains are relatively small (due to WAF) I need some mid-bass up to around 120Hz. I see that your F12G you quote upper response to 100Hz. Can I expect the same?

Also, I'd like to share my design with you at some point.

Thanks for your thoughts.

-KC

Sorry about the delay, I didnt notice your reply.

Materials: in norwegian kroner I think it totalled around 1000,- I'm not sure about the exchange rates but around 160-180 US$?

Tools: a handheld router and sirclesaw. For assembly I used woodplugs, polyurethane glue and straps, the kind you use to secure cargo. I thinks theres some pics of this earlier in the thread.

About different build dimensions, I wouldn know, I followed the instrucions supplied by Rythmik.

As for a second build? Im not sure. It really preformes great but in my current setup and room layout, they don't really fit in sizewise. So we'll see.

Brian,

Awhile back you suggested I add 2 inches to the depth of my F15 DIY enclosure compared to the ones you ship (19x19x22 vs. 19x19x20). I found a plan by luma Shackster on hometheatershack.com that looks to be 21x21x21.75. He says it is 4 CF after deducting bracing, driver and amp.

If I build an F15HP instead of F15, do you still recommend 2" deeper than the ones you sell or would the larger 4 CF be much better than the 2" deeper one? I'm guessing it is about 3.5 CF.

I'm considering doing some changes to my HT. Basically I'll build a acoustically transparent front wall and screen and hide the sub(s) and center behind this wall/screen. I have the space and material required for an LLT-designed sub based on the design goals presented here http://www.hometheatershack.com/foru...explained.html

Is there any reasons why the Rythmik servo would'nt work in an LLT-design?

The website states that for the hp version 3-4 cu.ft. sealed will work.

I'm looking at building a downward firing sub in a sandbox as an end table. I have room for either a 12 or a 15 but a 12 would be preferable as it would fit better. I know the 15 will get louder which I'm not concerned with. Will the 15 also go notably lower? Is there any reason to go with the 15 besides more sound? The table will be located behind my sectional at the corner with a lamp on it. So my main seating positions are about 6-8 ft away. Is there an issue with downward firing sub in this instance? Would the 12 or 15 be more suitable? Would a drawing of my room be beneficial?

So I made a drawing of my Living Room/kitchen/dining area. It's one large room with vaulted ceilings. I estimate the size to be 640sqft with vaulted ceilings making it hard to estimate the total volume. I didn't know when making it they would water mark it. There is an 11' false wall separating the living room from the kitchen where my couch is located. I put in the couch with an oval as the primary listening positions. The square with rounded edges is my proposed sub location. The TV and fronts are across from the couch in the sketch as well (circles and rectangle). The living room area is 18x13. The 3ft section on the left of the TV is a doorway. Hopefully this will help get some suggestions.

Congrats man! Perfect DIY job