Helium - a true micromonitor

[CZ Eddie]

In any case, my order has been placed @ PE.
Would really like to get answers to my above questions though.

The parts I ordered if anyone cares...

[Chris Roemer]

PE's decided to no longer produce a "full line" (paper) catalog, so there's that. These will already have "BSC" incorporated. Pointing "straight up", you'll probably end up needing to "unpad" the tweeter a bit (maybe a lot).

[scottsehlin]

Chris is correct that these will already have BSC incorporated. As small as they are, they often get put on a desk or mounted close to a rear wall, and the tonal balance seems to work reasonably well for that purpose.

I think a 60 watt amp is reasonable for this application. The Heliums can take more power than most micro speakers due to the excursion capabilities of the ND91 and how the drivers parameters match with the small box, but it's still a 3" woofer...

[CZ Eddie]

Thanks, guys!
An ~80-100W amp will be a possible upgrade option in the near future.

[CZ Eddie]

Folks, what size circle saw are you using to rear mount the ND91's?
Need to find out if I already have the correct size or if I need to order a new hole saw!

[Chris Roemer]

It's been a while, but I THINK a 3" will do?
If you have one, do a test cut on a piece of scrap and see.

[CZ Eddie]

It's been a while, but I THINK a 3" will do?
If you have one, do a test cut on a piece of scrap and see.

Thank you.
I didn't even think of it before but I just looked at the spec drawings:
http://www.parts-express.com/pedocs/...tions-8418.pdf

Looks like 3", which I have, may be too small?
A 3.25" may be required. Please do confirm if you get a chance, and thank you!

I won't have my driver delivered until Wednesday.
Was hoping to have all tools by then too.

EDIT: I'm good to go.
I've got a 3 1/8" hole saw which should be perfect!

[Chris Roemer]

I've front-mounted the ND90/91 and AURA NS3 drivers (which PE does NOW sell) using a 3.0" hole saw. With the tooth "set", and a small "wobble", the hole ends up being perfect.
You MUST relieve the back side (if front mounting - which I know you're not) in order for the driver to breathe.

[CZ Eddie]

I've got my wood all cut and partially assembled. Still have a ton of sanding to do.
Amplifier should be arriving in a couple days.

So, here's something I didn't consider beforehand.
Rear mounting the woofer requires a super thin baffle.
Doh.
Not an issue. Just,,, something I'm surprised I didn't think of.
I may go with front mount since off-axis response is so important.
That or sand down my baffle with some 36 grit till it's thin enough.

[CZ Eddie]

Oh and I'm a little annoyed at how small the mounting lip on this tweeter is.
Could it not have been at least 1/8" of an inch?
It's like a 1/16" lip. lol
Should have just left it without a lip if they were going to make it that small. sheesh!

[Chris Roemer]

I've not used that little guy, but I think in general it's just "press fit" in (from the front or rear), flush w/the baffle front (maybe a little RTV silicone to seal it - or a touch of masking tape around the back edge just to center it and make it "snug").

As far as the woofers go, you really need to either chamfer or roundover the baffle / opposite the side you mount from. The 90/91s are a LOT easier to work with than the ND65s!

[Wolf]

The ND16 has a lip on the front edge, that is supposed to be tapped into the enclosure. It provides the seal that is required.
Wolf

[CZ Eddie]

Ahh, okay that makes sense!
I was getting frustrated because with the test fit, it seemed one side kept going deeper than the other side.
Assumed it was supposed to sit on top. Great, I'm glad I complained about this because now I know I was doing it wrong.

[Wolf]

I used a rubber mallet and a block of wood to gently tap the tweeter in place flush with the baffle. You just have to be able to hit it squarely.

Later,
Wolf

[CZ Eddie]

Hmm, I added 1/2" Sonic Barrier but now I'm thinking I shouldn't because the enclosure is so small and it may actually make the enclosure "smaller".
What say you folks?

http://www.parts-express.com/sonic-barrier-1-2-acoustic-sound-damping-foam-with-psa-18-x-24--260-520B

Build is not complete yet, was almost done and then I broke the very last piece of wood just as I was assembling it. After it was all stained & sanded. ugh