Opinions on driver arrangement of four ND90-8s plus tweeter please.

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

I was playing with a .5 crossover today and it looks like that would be the only filter required. However my sim used a damped second order to get the baffle step flat so that is not going to be cheaper than Paul's notch filter.

John,

Tell me more about that .5 filter you've been working on please.

Thanks,
Matthew

[jhollander]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Here's a pic of the .5 filter using my ND90 file. You can pull the FRD file from Parts Express and with Response Modeler or Response Blender, add the baffle and box to the speaker response to create an on baffle FRD file. With the FRD file you can model the x-o in PCD, Win PCD, or XSim.

Of course you can measure and skip some of the FRD creation steps, but the computer exercise helps you to avoid some expensive mistakes.

[DanP]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

That doesn't look half bad, John.

Matthew, that picture from the Edge program was a little deceiving because there is some cancellation present in that graph that is hiding some of the pure baffle effect. The cancellation is due to each of the 4 woofers being a different distance from the "mic location".

Play with the program with a single driver and you should be able to see exactly what the baffle is contributing. Then you'd have a decent idea of where to roll off the .5 woofers. The thing is, though, maybe the drivers have frequency response anomalies that would change the location and/or severity of the rolloff. The best thing to do is what John did, which is measure the drivers on-baffle, then model the interaction for a flat response, not really worrying about exactly where the rolloff starts.

Dan

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Hey Dan,

Hope your day was swell. I'm having fun playing with new programs this evening. In Edge, what does speaker source density mean? Also when you say measure the speakers on baffle, you do mean in Edge and not with a measurement mic right?

[Chris Roemer]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

If you set "source density" to "1", you'll see just one "dot" on each driver (that would be OK for a TRUE "point source", but our drivers - at least today, are "pistons" with a certain diameter, even a small 3/4" dome). I think I use about "17" (for some reason I like a prime number) for source density. Play w/it and you'll see what it does.

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Thanks Chris,

I've been using 4; probably not enough. Is there such thing as too many?

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Thanks Chris,

I've been using 4; probably not enough. Is there such thing as too many?

Answer: yes, program has massive hesitation with 171

[Chris Roemer]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

I'll bet.

[Mayhem13]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

http://www.dnaudio.com/DNA-Sequence-Speakers.html

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Hello folks,

This evening I noticed mattp's Measured T/S Parameter Thread Sticky http://techtalk.parts-express.com/sh...-Thread-Sticky

Here are the results from the sticky: Dayton Audio ND90-8 3-1/2" Aluminum Cone Full-Range Driver 8 ohm (290-210)
Re: 7.38 ohms, Fs: 101.6 Hz, Qts: .9255, Qes: 1.078, Qms: 6.525, Le (1kHz): 0.517 mH, Vas: .0381 cuft, Effective Diameter: 2.5"

His measurements are quite different than PE's T/S Parameters on the product listing page, and I have no idea if the drivers used in either test were broken in. So, I guess I'll be breaking mine in soon, and I'm thinking of breaking in all eight at once.

Any wisdom from you guys as far as what kind of "stretchy exercise waves" to subject this octet to, and for how long would be great.

Thanks,
Matthew

[Chris Roemer]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

I usually break 'em in by hand, i.e. you (gently - making sure NOT to push or load them "off center") push them close to Xmax w/your fingers. In - out, in - out, get it? Basically, what you're doing is exercising the spider (letting whatever "coating" or set, or whatnot) putting tiny "cracks" in it, like breaking in a brand new pair of shoes.

Some people play a sine wave near Fs, driven to near Xmax, for hours.

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Interesting Method Chris,

Now that's an exercise routine with which I'm not familiar. Is there a workout video for this? On a serious note though, I wonder if I could make something like a bellows to exercise them with nice even air pressure changes, without having to risk me pushing my thumbs through the cones. Operating it could be good exercise for me too.

I think my wife and our cat would both prefer your quieter method or something similar over me playing a sine wave through eight drivers at once for hours on end.

[Chris Roemer]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

These have Al cones, so your fingers won't go through.
Also, in free air (no box) they'll hardly make a sound. You can even try 20Hz, which is below Fs. Might not hear a thing.

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Very true about the Al Chris,

But I'm more worried about pushing on them out of alignment.

If I were to break them in with a sine wave at near xmax, do you think I should mount them on something to keep them from dancing around? With neo magnets, they're pretty light. I have plenty of cheap thin board lying around.

Thanks,
Matthew

[crunchhardtack]

Re: Opinions on driver arrangement of four ND90-8s plus tweeter please.

Salutations fellow animals,

So I ran a 25 hz sine wave at near xmax for about 3hrs until it was bedtime for my wife.
Do you guys think that was enough time to be ready for some DATS testing?

Here is my break in rig.

Cheers,
Matthew