Aura NS3-193-8A bipole build

[BoomieMCT]

I just bought four of the Aura NS3's on sale at PE and intend to make two ported full-range bipole speakers.

I can easily model a ported box in Unibox or WinISD however I'm having trouble deciding on a tune. Since only one driver will fire forward but both driver's port output will be coming out the front I'm not sure how to guesstimate the combined output. Does anyone have any tips?

Unibox shows output from the port and from the driver. I tried graphing the output in the same box using one and two drivers and interpolating what I might get by using a driver output halfway between the two. Is this valid?

[planet10]

As far as bass from the drivers are concernec they don't care what side of the box they are on, The wavelengths are so long they don't "see' the box.

dave

[Timn8ter]

This doesn't address your question but I'd like to offer my opinion about the driver you're considering.
The driver shown on the PE page appears to be a bit different than the NS3-193-8A in respect to the T/S parameters.
I have used the NS3 in a few applications, however.
I think it has a wonderful sound and surprising bass response for a 3 inch driver but found it to be easily over-driven in vented boxes.
Having built a vented bipole with this driver I find that, unless you're planning to keep volume levels low, it is better suited for use in small sealed enclosures using a bass module for the lows.
You may want to consider a sealed bipole for these.

[squib]

Timn8ter,
I also just ordered the PE Aura drivers and was planning on putting them in your PC speaker design (here: http://www.timn8er.com/Aurasound%20NS3.htm). Has something changed your opinion of this speaker's performance? Your original write-up seemed pretty positive concerning the sound from this vented design. Thanks for any additional thoughts and thanks for all the helpful info you've already posted to this forum.

[Timn8ter]

No, I've not changed my mind at all about these drivers.
When someone says "PC speaker" I assume the speakers will be used on a desk with the listener seated only a few feet away, typically 3 feet or less.
At this distance I also assume the listener will not be driving the speakers into the 100db+ range.
Used this way the vented applications are very nice, with excellent detail and imaging and will deliver a respectable amount of bass sounding much fuller than "typical" PC speakers.
Put those same speakers on a couple of stands, hook them up to a higher powered amp and try to play them at room filling volume levels and you're likely to over-drive them.
If Boomie is planning to use his speakers as typical stand-mount units for more than background music he will be better served with sealed enclosures.

[BoomieMCT]

We'll see! I intend to use these speakers in my living room for 90% ambient sound (why I went bipole). Right now I have two T-B W4-656's (the PPM cone ones) driven by a 30 watt/channel PsAudio Model 2 amp doing the job and they are more then loud enough. I'm hoping four of these 3" drivers will be able to keep up.

I have no listening reports yet but I figured I'd post a pic to show how things are coming along. I made the front baffle double thick (so I could cut big chamfers in it) and now it is a PITA getting the rear of the driver holes chamferd out. I should have prototypes running in a week or so.

BTW, the ugly grey spots are slop from a two part wood filler I tried out. It got very messy so I think I'll stick with my traditional wood filler or stuff I make myself. After sanding / painting you'll never see those spots!

[BoomieMCT]

So I have the prototypes for these done and I'm breaking them in. No FRs yet (as I haven't tuned the port, stuffing or decided if the rear driver will have a lowpass filter) but I can give some listening impressions. Very diffuse sound, great for ambient / party music (with a sub). These fill the house very very well. I'll give more info in a few days after break-in and some tuning work.

[BoomieMCT]

These should be somewhat broken in now. Here is a quick FR. Since the amp in my testing room can't take a 4 ohm load I actually have both speakers in series stacked so their drivers are as close as possible. I'm not expert at reading these graphs but is the spike at 190 Hz possibly from driver resonance? The Fs should be lower - maybe I didn't chamfer the back enough (I thought I did). Any thoughts?

Please note this is with no stuffing in the box. I'll post a FR with stuffing in a second.

[BoomieMCT]

Here is an FR with some stuffing. My ear says this sounds much better.

[BoomieMCT]

So after playing these for a while I was getting a very overly enegetic mid-bass that was causing electric guitars to be quite painful. I played around with changing stuffing and some notch filters but nothing seemed to fix this. So I took the whole thing apart and went crazy-go-nuts with a wood rasp to open up the chamfer behind the drivers as much as was physically possible. I also changed the tune of the box to something closer to the Fs of the driver (from 55Hz to 68Hz or a 4.5" port to 3").

I don't have a FR yet for these changes but these sound immensly better to my ear. I think that even with the chamfering I had done before that these drivers were still way too constrained. Considering the small form factor of the motor it is too bad they couldn't have opened up the basket more to breathe better.

After another day of listening with a moderate BSC (L = 0.7 mH, R = 2 ohms) I think I've just about got this where I want it. I'll try adding a little stuffing to remove any possible high frequency coming out of the port.

BTW, someone had concerns over the excursion of this driver in a vented enclosure. I can say that with my 30 watt per channel PsAudio Number 2 this doesn't seem to be a problem. I've been running these speakers with a sub and it easily fills my living room, dining room and kitchen.