My N3s build

django11 · « **on:** 14 Nov 2010, 02:28 pm »

The kit is still in transit

so to keep me occupied I'll do a build thread. There have been many of these and the only reason I am doing one is that my build is a little different and might interest someone for a future build.The materials are not necessarily those that would get the highest recommendation from Danny.

I decided on using Baltic birch plywood for the enclosure. The plies will be exposed in the front for a "look". Corners are mitered.

The obvious advantage of doing the enclosure this way is that you have a finished box right away, no veneer, no paint. If you are new to woodworking there are few pitfalls to doing a box like this. You need pretty good equipment to cut the miters to make them look nice and so you don't end up with a too out of square box. If the miter is off too much the front and rear baffles become trapezoidal shapes and hard to cut for a nice clean fit. Of the two baffles, choose the worst fit and call it the "back"

.

Glue up is a bit more challenging because of the 45s on the corners. I have a 23 gauge pin nailer pin nailer that I use just to keep things from moving while I clamped and measured for square. 23 gauge leaves a really small hole (.028125 inch).

I want to have the drivers on hand before doing the holes in the baffles so on to

Damping

Here is the plan:

With shipping, duty, brokerage fees and taxes, getting 2 sheets of No rez to Canada would cost be 155.13$

.. Even though I like No Rez I couldn't bring myself to spend that much for it so I decided to try a constrained layer where the damping layer will be four thicknesses of ice and water shield. Here is the text for the constrained layer damping idea: Panel Vibration Damping Experiments. (The author is actually a retired rocket scientist

.) I am hoping that adding the 1/4 masonite will deal with some of the resonance issues of the BB plywood. I'm going to mechanical fasteners and also stick the masonite to the ice and water shield with this : Blue seal.
So I don't know if the enclosures will be well damped but they will be waterproof

. BTW I have all these materials laying around as leftovers from jobs so this is 155$ vs 0$ so I will take a chance on it.

More to come as I progress...

HT cOz · « **Reply #1 on:** 14 Nov 2010, 03:04 pm »

Nice Pics. Where do you think you will put the xover network?

django11 · « **Reply #2 on:** 14 Nov 2010, 03:59 pm »

Quote from: HT cOz on 14 Nov 2010, 03:04 pm

Nice Pics. Where do you think you will put the xover network?

It seems people put them on the braces...

Ron · « **Reply #3 on:** 14 Nov 2010, 04:15 pm »

Your cabinets look very nice so far. Please post pictures as your progress continues. I mounted the high pass crossover on top of the upper brace and the low pass crossover on the bottom side of the lower brace.

nickd · « **Reply #4 on:** 14 Nov 2010, 06:28 pm »

Thats some fine cabinet building!!!

With boxes built to that high level of quality, I would just use some open cell foam (K22) to line them. They will sound very natural. If you like that "dead" sound in a box you can go to the local car parts store and buy a couple of cans of spray on "undercoat" for the inside walls of the box. It is soft and rubbery when dry and will add some dampening to the box with little effort. They use it to dampen sheet metal and it works great.

I would not put "masonite" on the inside of a speaker box, it's too hard (IMOP). The sound can bounce off of it and come through the the mid woofer cones out of phase causing coloration.

django11 · « **Reply #5 on:** 14 Nov 2010, 07:18 pm »

Quote from: nickd on 14 Nov 2010, 06:28 pm

Thats some fine cabinet building!!!

With boxes built to that high level of quality, I would just use some open cell foam (K22) to line them. They will sound very natural. If you like that "dead" sound in a box you can go to the local car parts store and buy a couple of cans of spray on "undercoat" for the inside walls of the box. It is soft and rubbery when dry and will add some dampening to the box with little effort. They use it to dampen sheet metal and it works great.

I would not put "masonite" on the inside of a speaker box, it's too hard (IMOP). The sound can bounce off of it and come through the the mid woofer cones out of phase causing coloration.

I forgot to mention that I will be adding a layer of Roxul over the masonite and then filling the rest loosely with fiberglass. Danny and others seemed to be of the opinion that mdf is superior to the plywood for speaker building because it is so inert. When I rap the sides of my boxes I definitely get tones that differ depending on where I rap. I am assuming that these tones are the resonances that damping gets rid of?

Here are the juicy parts of the link I gave before to the Panel Damping Experiments:

"A graph of the responses (50 kb) from five of my experiments reveals several interesting results. The horizontal axis in the graph is frequency, in Hz. The vertical scale is the output from the acoustic guitar pickup, in dB. (The curves have smoothed a bit using a running average in frequency). I have no idea what the frequency response of the guitar pickup is, and we are mainly interested in relative levels anyway, but it was a real surprise to me that the vibrations appear to peak at 2000 Hz, and are significant to 4000 Hz and higher. I had expected the response would be highest at low frequencies and essentially disappear above a few hundred Hz. The red curve was the first test, where the inside of the large enclosure was empty (except for the old loudspeaker), and the top was 3/4" MDF. The blue curve represents the same configuration except that the interior was filled about 50% with fiberglass (the garden-variety type used to insulate houses). The fiberglass filling reduces the panel vibration by about 20 dB across the entire frequency range. This corresponds to absorbing 99% of the sound energy, at a very low cost, and with very little effort. And it kills internal standing waves. The lesson here is real clear: stuff the enclosure with fiberglass. All remaining tests included the fiberglass filling. The black curve is for 3/4" MDF plus a layer of 1/4" tempered Masonite, but no damping layer. I was again surprised that adding this layer didn't improve things more than it did, but this was probably because the two layers were only attached at the edges by the array of bolts. If the two layers had been glued together I think there would be more improvement. The final two curves are for the full sandwich with the damping layer. The damping layer for the cyan curve is 1/8" loaded vinyl that costs $2.00 per square foot. The damping layer for the green curve is 2 layers of 30# roofing felt that costs $0.17 per square foot (thanks to Dickason for mentioning this stuff). The constrained layer of roofing felt reduces the peak vibration by almost 20 dB, and the average by about 10 dB, relative to the blue curve without a damping layer. In most regions it is better than the hi-tech pricey vinyl. Needless to say, I chose the roofing felt sandwich for my enclosure construction."

Here is the graph

django11 · « **Reply #6 on:** 14 Nov 2010, 07:27 pm »

Quote from: Ron on 14 Nov 2010, 04:15 pm

Your cabinets look very nice so far.

Thanks Ron, but you know I'm not taking close ups of any of my mistakes

. If they come out half as nice as yours I'll be happy.

dvenardos · « **Reply #7 on:** 15 Nov 2010, 01:04 am »

As usual, nice job!

django11 · « **Reply #8 on:** 15 Nov 2010, 01:24 am »

It took me about 3 hours to do the 3 layers of rain/ice shield + blue seal+masonite

I have some temporary braces in there until everything dries. The tone of the enclosure has definitely changed when I rap on it. Sounds less musical.

Now: C'mon Canada Post bring me my stuff!!

Guy 13 · « **Reply #9 on:** 15 Nov 2010, 02:15 am »

Quote from: django11 on 15 Nov 2010, 01:24 am

It took me about 3 hours to do the 3 layers of rain/ice shield + blue seal+masonite I have some temporary braces in there until everything dries. The tone of the enclosure has definitely changed when I rap on it. Sounds less musical.

Now: C'mon Canada Post bring me my stuff!!

Hi django11.
I don't get it? What's the idea of doing it that way? First time I see that. You still have no absorbtion material inside the enclosure?
Will you add some NoRez later on?
Guy 13

django11 · « **Reply #10 on:** 15 Nov 2010, 03:08 am »

There is a first for everything! I'll add Roxul. The whys, whats and wherefores are explained at some length above...

django11 · « **Reply #11 on:** 18 Nov 2010, 02:32 am »

The kit is here so I'll be doing the crossovers soon. I can't really follow schematics so are there any really detailed pictures of the N3 crossovers? Ron's are pretty good but there is some stuff I can't quite make out.

Zerogravity · « **Reply #12 on:** 18 Nov 2010, 04:21 pm »

Looks awesome! I will look forward to final results and it should make for
some interesting measurements.

django11 · « **Reply #13 on:** 18 Nov 2010, 09:59 pm »

Quote from: Zerogravity on 18 Nov 2010, 04:21 pm

Looks awesome! I will look forward to final results and it should make for
some interesting measurements.

Measurements? From me?

django11 · « **Reply #14 on:** 19 Nov 2010, 12:27 am »

Quote from: django11 on 18 Nov 2010, 02:32 am

The kit is here so I'll be doing the crossovers soon. I can't really follow schematics so are there any really detailed pictures of the N3 crossovers? Ron's are pretty good but there is some stuff I can't quite make out.

Ron very kindly e-mailed me some close ups of the ones he just made. Thanks Ron!

django11 · « **Reply #15 on:** 20 Nov 2010, 06:27 pm »

Some progress. I should have used a down cutting spiral bit for the holes. I got a bit of tear out, though nothing major. I almost had to do one baffle over but managed to seize victory from the jaws of defeat :. Luckily I make a lot of mistakes so I know how to cover them

... I'll start the crossovers just as soon as I slap on a coat of finish...

django11 · « **Reply #16 on:** 20 Nov 2010, 09:05 pm »

This part is more trying. How am I doing?

dvenardos · « **Reply #17 on:** 20 Nov 2010, 10:11 pm »

Dang Stephen, you kick ass. You get stuff done so fast!

Are there any bypass caps in the kit? I can mail you some Gen II bypass caps if not.You can easily add them after you are done with the crossover.

eclein · « **Reply #18 on:** 20 Nov 2010, 11:20 pm »

Are the instructions easy?? I have never read schematics, I'm in the Crossover Kindergarten. And they look great by the way!!!!

django11 · « **Reply #19 on:** 21 Nov 2010, 12:13 am »

Quote from: dvenardos on 20 Nov 2010, 10:11 pm

Dang Stephen, you kick ass. You get stuff done so fast!

Are there any bypass caps in the kit? I can mail you some Gen II bypass caps if not.You can easily add them after you are done with the crossover.

This is more work than I thought. No bypass caps came with the kit. I mistakenly thought that Platinum's where part of the kit. Didn't know you could bypass with Gen II. Getting information on some of this stuff seems to be a matter of chance more than anything else... Are the Gen II expensive and do they compare well to the Platinums?

With any luck I should be listening to the N3s tomorrow...