[Russell Dawkins]

Is anyone familiar with this NS4-194-8A 4" full range driver by Aurasound?
https://www.madisound.com/store/product_info.php?products_id=8989

It looks like it would be promising as a line array driver with 8 or 9 per side yielding 95.5 dB/W, or around 98dB/W in-room.

It would be cheap to experiment at $3.70 each!

[JohnR]

Hi Russell, from the specs magnetic gap depth 8.4mm, voice coil length 7mm, I believe that indicates an Xmax of around 0.7 mm. Which seems a bit on the low side, even for an array. I can't help feeling that the 3" would be a better bet - https://www.madisound.com/store/product_info.php?products_id=83

Were you thinking box or open baffle?

[Russell Dawkins]

It looks like the excursion through which the behaviour is linear is indeed ±0.7mm. Also nothing is said about it in the copy like what is said about the 3" inverted dome you refer to, where Madisound calls it the best sounding 3" driver that they're aware of. Perhaps this driver sounds really nasty - worse than the specs and response curve would suggest - there must be some reason for the blow-out price.

It's just that I had a revelatory experience, which is still fresh in my mind, years ago with a line array of 9 Philips drivers of very similar spec (AD5061M8s) but with lower sensitivity if I remember. They were mounted in what was called a "tapered tunnel reflex" - a short folded transmission line, from some perspectives. Imagine a TL in an "S" configuration, about 14" high and 14" deep with about 4" of internal width. The 4'1/2" driver goes in the top of the baffle. Now, flop it on its side and multiply it 9 times, vertically. This gives a line array with 9 drivers in a vertical line near one edge. I made it for a P.A. column for a small time singer as a gift. When we took it into the music shop to choose a suitable powered mixing board and the sales rep plugged a mic in and said "check, check - test, one two", he uttered an expletive and the tech came trotting out from the service department at the rear to find out what had produced that sound, they sounded that good - and unusual - on voice. It was the first time I had the experience of turning up the volume and having the speaker sound "bigger", not "louder".

Anyway, for less than $100 for the 18 drivers, I am tempted to give it a shot, but you may be right, and this may well be wrong-headed!

I just found this in a search for the driver, so maybe they were more special than I had allowed for...

..."The Rectilinear III used the Philips AD5061M8 full range driver as the midrange.This 5 1/4" cloth edged, paper coned driver had not only a whizzer but a copper cap on the magnet to improve the high frequency response.It was also used by Infinity,Genesis, and Dahlquist(among others).....They were very natural sounding in the midrange.The only speaker near their price range that sounded better on acoustic guitar was the original Quad electrostat (in the early 70's). I wish I could find a case of these midrange drivers somewhere."...

[planet10]

Tunnel Reflex was a trademark of Admirals. The line was as you described. http://t-linespeakers.org/drivers/tunnelreflex/index.html (unfortunately not a good picture with the side ripped off)

I never saw one of these with a Philips in it, but the Philips is a really good driver.

The 3" is probably better for an array.

Re the best 3" they know of, they must not have gotten a lot of exposure to the FF85K that they used to sell.

dave

[Danny Richie]

Unfortunately when you stack a bunch of full range drivers up like that you wind up with a comb filtering mess and you'll get cancellation from the top end all the way down to about 3 to 4kHz range.

You'll get added gain and output as frequency decreases but as frequency increases you'll have no added gain. By the top octave you'll have the same output as a single unit.

The only way to maintain any level of accuracy is to let only a single unit play full range and let the additional units share the load as frequency decreases.

[Russell Dawkins]

I would think that often small drivers have a rising response characteristic, so the decrease in coupling at the higher frequencies could work in your favor. It sounds like it would be a good idea to low pass the widerange drivers at around 4 kHz and use a good high efficiency horn tweeter from there on up.

As to the "comb filtering mess" I know what you mean, but there must be some important strengths at the same time for what I've heard from line arrays to sound so good.

[Danny Richie]

I would think that often small drivers have a rising response characteristic, so the decrease in coupling at the higher frequencies could work in your favor. It sounds like it would be a good idea to low pass the widerange drivers at around 4 kHz and use a good high efficiency horn tweeter from there on up.

As to the "comb filtering mess" I know what you mean, but there must be some important strengths at the same time for what I've heard from line arrays to sound so good.

You nailed it when you said cross it to a tweeter.

I have designed several arrays that cross to a single tweeter. The trick there is to just let the woofers or pairs of woofers on either side of it play up the tweeter and then let all of the other drivers help fill in or share the load in the bottom end.

One of the high school students built something similar a few years ago and it actually came out very well.

See it here: http://www.audiocircle.com/index.php?topic=54598.0

[yoaudio]

They sound better that the T.V. speakers in my Frugel-Horn Mk3, but like Russell and Danny said, they need a good high efficiency horn tweeter.