budget MT - NS6 and BC25SC

[donradick]

So for some reason, I wanted to build a budget MT, about $12 each for the woofer and tweeter. Someone somewhere suggested the Aura NS6-255-8a,
https://www.madisound.com/store/prod...oducts_id=8406 which certainly looked pretty flat and decent distortion (+1 for Aura listing that!), and I really liked the look of the Vifa BC25SC-04
https://www.madisound.com/store/prod...oducts_id=8354
So, with more than a little trepidation, and a lot of handholding from some very generous experts, I modeled them up for a .53 ft vented box with 3dB BSC. I gotta say, the PCD "work" came together very fast. At first I was perplexed looking for phase matching, but then realized that it was darn near perfect. Let me know what you think, please.

[donradick]

the crossover detail.
There was a bit of a hump in the woofer response 600-1600, that flattened out mostly when I dropped the LP from original 2700 to 2400.
Glitch at 300-400 is obviously from poor splicing, but I don't think I should be concerned.

[Brewski]

the crossover detail.
There was a bit of a hump in the woofer response 600-1600, that flattened out mostly when I dropped the LP from original 2700 to 2400.
Glitch at 300-400 is obviously from poor splicing, but I don't think I should be concerned.

Don,

It might come down a bit once you add the inductor's DCR but in the low pass I'd try to get the hump out by trying a higher DCR inductor and possibly making L2 a larger value.

In the high pass I'd experiment with making the crossover second order rather than third order and experiment with padding the tweeter a bit more so it's closer to 90.

Take it easy
Jay

[2leftthumbs]

Cool! I bought 4 of the aura drivers from pe and, inspired by Tom s thought I would try to use the acoustic reality series xo as they do have an extended range.

[donradick]

Cool! I bought 4 of the aura drivers from pe and, inspired by Tom s thought I would try to use the acoustic reality series xo as they do have an extended range.

I'm listening to the NS6 full range right now in a test box, and it really sounds very nice

[2leftthumbs]

Im just finishing up my boxes and rounding up crossover parts.

[donradick]

Don,

It might come down a bit once you add the inductor's DCR but in the low pass I'd try to get the hump out by trying a higher DCR inductor and possibly making L2 a larger value.

In the high pass I'd experiment with making the crossover second order rather than third order and experiment with padding the tweeter a bit more so it's closer to 90.

Take it easy
Jay

Thanks Jay -
I'll definitely give a listen to 2nd order on the tweeter - playing around with it, I got a really deep reverse null, but the FR was not as smooth, and the phase tracking didn't look quite as good. Still learning this stuff. Listening is what really matters.

[Wolf]

It's better with 3rd on the tweeter, as you have the asymmetric slopes to make up for the acoustic offset. However- that 46uF cap is awfully large, and can probably be reduced to a 20-25uF tops.

Later,
Wolf

[Brewski]

It's better with 3rd on the tweeter, as you have the asymmetric slopes to make up for the acoustic offset. However- that 46uF cap is awfully large, and can probably be reduced to a 20-25uF tops.

Later,
Wolf

Yeah the 46 value is what had caught my eye and had me thinking if a cap that large was really adding anything vs. not having one there.

~Jay

[donradick]

It's better with 3rd on the tweeter, as you have the asymmetric slopes to make up for the acoustic offset. However- that 46uF cap is awfully large, and can probably be reduced to a 20-25uF tops.

Later,
Wolf

Thanks Wolf - yah - that 46uF cap bothered me too, since I don't remember seeing values like that on most tweeter HP crossovers. I'll play with much smaller values, both in PCD and in listening tests.

BTW, I found crucial modeling help for Response Modeler in Vol 2 of your tips.
Good work.

[tom_s]

Don,

I'm no expert with PCD (or any other modeling program for that matter), but I see two things you might want to check. 1-You don't have the DCR entered for your inductors. 2-Your HP series resistance of 1 ohm seems pretty small. Is there a parallel resistor that makes a split L-pad down further on your screen shot that got cut off?

FWIW, I like this woofer with quite a bit of BSC. It sounds pretty good with a 2mH-2.2mH primary inductor...but part of that is my basement HT room. The upside to using values that large is that the lower midrange hump falls off a little better. The downside - it can sound a bit thick & bloated in other rooms in the house. YMMV....

[donradick]

Thanks Tom - I'll try modeling with more BSC, and that should help the upper mid bump a bit also. These are slated for bedroom use, and will be pretty close to a wall. When I first started modeling in PCD, I had both the W and the T crossed at 2700. I kept backing down the W until it's now at 2100, and the midrange looks darn near perfect. I'll probably restart the model from scratch with beveled sides and an offset tweeter and see what that does. I am VERY impressed with the sophistication of these (free) tools. Big thanks to all the contributors, expecially our own Mr Babgy.

[Wolf]

Thanks Wolf - BTW, I found crucial modeling help for Response Modeler in Vol 2 of your tips.
Good work.

I'm glad you found it useful!
Later,
Wolf

[2leftthumbs]

The ns6 sounds pretty good for the price. I doped up the frame with some rope caulk to dampen it.

[duanebro]

Has anyone completed a build with the NS6 yet? These drivers interest me for some reason. I try to watch for a finished design, but haven't seen any yet.

Duane

[tom_s]

I've been listening to a design with the BC25SC55-04 and I'm still trying to find a the right amount of BSC & correct box tuning for my room. I need to order more inductors. What I have on hand now is either too big or too little. Madisound shows 1mH for the woofer inductor in their 8 ohm design, but something that small just sounds anemic to me. It seems strange that they would be using the same sized inductor on both the 8 ohm and 4 ohm versions. Me thinks there's something fishy going on there.

[scottsehlin]

I've been listening to a design with the BC25SC55-04 and I'm still trying to find a the right amount of BSC & correct box tuning for my room. I need to order more inductors. What I have on hand now is either too big or too little. Madisound shows 1mH for the woofer inductor in their 8 ohm design, but something that small just sounds anemic to me. It seems strange that they would be using the same sized inductor on both the 8 ohm and 4 ohm versions. Me thinks there's something fishy going on there.

They are adjusting the Zobel network on the woofer, which at least makes the use of the same inductor a little more plausible. On the surface the adjustment doesn't seem large enough to make an acoustic equivalent, but without actually modeling it, I can't say for sure.

[donradick]

I am continuing to work on this project, and have been very satisfied so far. The initial test box was about .55 ft^3, with a simulated F3 of about 63 Hz. Initially I had modeled BSC with about 2-3 dB (resulted in about a 1.0 mH coil), and the bass sounded very weak. I saw a comment from Jeff Bagby that small 2 ways sounded better with full BSC, so I modeled again, and got about a 1.3 mH coil. Sounded much better!

Newly confident, I am finishing building a pair of 20 Liter boxes, which model as a 43 Hz F3. Woohoo! Original test box (internal 8.5 x 11 x 11.5) and new box (internal 8.5 x 15 x 12) images below.

For what it's worth, I am finding PCD sim looks best with a 2nd order LR on the woofer at about 1900, and a 3rd order on the tweeter at about 2300.

[2leftthumbs]

I've built a pair using the acoustic reality crossover in 20 L ported boxes after being inspired by tom s. I'm using the sb acoustics 25 mm tweeter that was on sale at madisound a while back. I wind my own coils so its fairly easy for me to play around with. I ended up( at least temporarily) with a 1.5 coil on the woofer but I may have to back off a little. Its still a little heavy on the high and low ends.

[2leftthumbs]

It seems strange that they would be using the same sized inductor on both the 8 ohm and 4 ohm versions. Me thinks there's something fishy going on there.

Yeah I noticed that too. I also noted that the 8 ohm version is 1 db more sensitive than the 4 ohm.