Build: DC Gold N7R Steel Enclosure

[Chester]

Hey, this is a project I started on ... well ever since I was 12 years old and really got into sound... I am 20 now so along the way I have learned tons. I actually began buying things for this project around 2 months ago however this is the culmination of 8 years of research. There is a reason behind nearly every feature of these speakers (and my entire system for that matter).

Here are the pictures of the build! http://picasaweb.google.com/Chesteta/N7RBuild#
-more pictures will be coming soon, I have misplaced the pre-plasma cutting and pre-Line-X photos, the pictures in the thread are some of the pictures from the Picasa web album.

The speakers are DC Gold Audio N7R's, ~93db/w/m, full range speakers; what I believe are some of the best full-range speakers out there, Neodymium magnets, ferro-fluid, no spider, aluminum and beryllium cone (with a coating), the grills also act as phase plugs. If you have heard of "Babb" speakers, these are made by the guy who bought out Babb... http://www.dcgoldaudio.com/



The encosures are steel Flotec well pressure tanks, model FP7105 (6 gallons per tank), pressure tested to 100 psi http://www.flotecpump.com/

The tanks are coated with Line-X (polyurethane) http://www.linex.com/


The insides are coated with 3M Undercoating (to dampen the steel)


Then I added 2" thick rock-wool 'tightly' which REALLY deadens the steel, knocking on them sounds like hitting on a board of MDF but with a bit higher resonance frequency.


I used microfiber cloths to keep any rock-wool 'dust' out of the ferro-fluid used by the speakers.


8 AWG wire with soldered connections, and my 'signature' bolt terminals.



The speakers are decoupled from the enclosures with silicone 'gaskets' (Mounted from the back)



I'd love to hear your thoughts

[StereoClarity]

What exactly is going on in this picture? What is that on the back of the speaker?

[Chester]

It is a bracket... I don't think it is shown, but in the finished speaker, there is a hole drilled in the center of the back of the enclosure, a bolt and washer then go on the rod that is sticking up. Basically it pulls the speaker onto the front from the back, part of the decoupling system.

EDIT: the 'frame' is made of aluminum and superglue (for magnetic reasons), the 'rod' is just steel rod... check out the picasa web album for some better pics of that stuff http://picasaweb.google.com/Chesteta/N7RBuild#

[Ricci]

Interesting. I'm not so sure about the effects of the rod mounting system decoupling it from the enclosure, but who knows. How do you like the sound? I assume that you'll be building a pair of stands for them, or maybe already did since the enclosures are round?

[Chester]

Thanks for the feedback, the rod system is loosely modeled after B&W speakers' decoupling system: the sound is incredible, they are very clear even at loud volumes I am currently using cinder blocks as stands with rags (soon to be nice towels) help hold them centered on the blocks, I'll get some more pics up soon to show you...

EDIT/ADDITION: I have been considering using green glue instead of silicone as the decoupling material, it is a viscoelastic material which converts energy into heat, the only 'issue' is that it never completely sets, stays in a sticky tacky consistency, so I am not sure if I can keep it from oozing out around the speaker... in any case, the green glue company uses a thickness of .5 mm in their tests so it may be possible... Probably going to order a tube and test the consistency out
http://www.greengluecompany.com/

EDIT2: looking around a bit more, I may use a product called "sorbothane", it appears to be a better option because I can get a gasket made to a spec instead of trying to mold one I would definitely appreciate any advice/experience regarding sorbothane
http://www.sorbothane.com/

[Owen Bartley]

Looks like a very unique project Matt, and I bet they would look really nice on some custom stands. Are you just building the pair, or do you have any plans for a surround setup? A sonosub would seem to go nicely with these too.

[Chester]

Thanks OJ, I may go the 'custom stand' route someday but for now the cinder blocks are working quite nicely, they make good shelves also I also am just rockin' a pair of speakers... It is my belief that a pair of *properly positioned* speakers is all you really need... I have things set up quite well where I can hear sounds to my sides and 'behind' me (if they were recorded to produce that effect). Maybe someday I will run 5.1 but right now this is all in my bedroom so 2 channels is just fine. I am currently running a JL 13w7 sub with dual passive radiators: the -3db mark is at ~14 hz I built the sub a while ago however I will probably post some of my build pics soon. Everything is powered by (2) crown K2 amps running through a USM-810 processor/mixer; the amps are 'separated' on a per channel basis, so one amp does all the left channel (bass and high) and the other does the same; this seems to run much cooler temperature wise and also alleviates issues with the power saving feature (it can take a 1/10 of a sec for the amp to engage so if there is no bass for a while there is a delay before the sub kicks in if the amps are separated by highs and lows)

EDIT/addition: I also run all the audio 'balanced' from my computer to the speakers, even with the amp gains all the way up there is just a slight hiss with your ear near the speaker
-this is all hooked up to my computer btw; using an audigy 2 zs with kx drivers to get a balanced output; i have 2 + weeks of music on my network drive

[harleyhualer-sc02]

Nice build. I thought I was the only one who knew about DC Gold on here. I plan to build a 7.1 system withe the n7r's soon,have to get my subs done 1st.

[Chester]

just got the sorbothane cutting it now (to replace the silicone)

[Chester]

I redesigned the rear mounting system; I could not 'wrench' down on the sorbothane as much as I wanted without the silicone failing around the magnet so I decided to do a steel approach using what the home depot calls clothing line hooks:

The black ring around the magnet is a vacuum belt cut in half (half the width) which helps keep the clothing line hooks aligned and also aids in aligning the aluminum ring; I used electrical tape to cover the hooks so there would not be metal on metal with the basket, also to keep from shorting anything around the electrical terminals.


One change I may make would be a better decoupling on the back side; since there is so much more sorbothane surface area on the front of the speakers, the back side 'squashes' quite a bit (not shown well in this pic, I have since tightened them more)





My computer and USM-810 processor in the closet, the only moving part on this system is the one fan on the computer, soon to be changed to a better solution; the buzzing of the cold cathode tube on my screen is all I can hear at my desk though I hope to get an LED backlit LCD TV which should produce no noise...


Here is the cut sorbothane sheet I used; since this project I have used the sorbothane to decouple my RTA-M mic from a stand I made out of a broken clothing rack... thats for another post though


Sometime soon I will post the near-field measurements of the speakers...