The making of: The Two Towers (a 25 driver Full Range line array)

[wesayso]

Don't forget Maya and 3ds-max as quite capable mesh editors/modelers...

Just finished installing the first two bypass filters to finish up all filters installment on the first array. Even though they are much smaller than the big series filters, they still are a pain to install into a finished cabinet! They are in though, time for a quick break and then some measurements to see if everything still checks out.
If it does, then the first array will be ready to close back up again. Which is an enormous job by itself (lol), trying to seal it all off properly.
A few weeks ago I said: I'm just going to close them back up and be done with it...
Funny how time always changes the plans. I'll first just mount the inner baffle holding all the drivers with a few spacers, so I can re-apply the finish on the outside of the enclosure. More work, more time without speakers, but I just know if I bring them back in again I'll never do said work (and just keep on listening). I still need the weather to work with me, as it did this weekend.
Fingers crossed!

[wesayso]

Yeah! Control measurements done, all works out as expected!

5 sets of 5 driver positions tested with a straight wire instead of the driver and an 8 ohm (8.2 ohm give or take) resistor in series.
Bypass tested on the driver position with a parallel resistor (same 8.2 ohm).
This all checks out and resembles the needed curves:


All driver groups are visible, the straight line is the middle set of (5) drivers that don't have any filter at all. The one(s) with the 3.5 KHz dip are
2x bypass filter on one driver each. The rest of them are the filter blocks of each section, as figured out by Vituixcad sims.

So the next job will be to close this one up with the inner baffle and the drivers, checking to see if all drivers have sound. That will hopefully be a job for next weekend. If the weather permits... Then on to the next...

What would we do without (in no particular order):
John Mulcahy for giving us REW
Bill Waslo for bringing us X-Sim
Kimmo Saunisto for the awesome Vituixcad (which took me a while to spell right )
Denis Sbragion for creating DRC-FIR (which I will need to get it all back up again)
The DIYaudio forums and it's helpful and generous members...

Without the above, and many more which I no doubt forgot to mention I would never have got this far with my project.
A project that still is fun for me and new adventures keep coming. Keep sharing guys, I'll try and be as open as I can on
my part. Working together we can really achieve something special.

[wesayso]

Of course the above list of thank you's should also include Marcel Batík (mabat) for creating the ATH horn tools and Thomas Drugeon (pos) for handing us RePhase and many many more.
With the tools they offer (free for personal use) our community now has possibilities we could have only dreamed about having at our disposal. Combined with a wide variety of enthusiastic users, who may not always agree with each other, we do have a rather unique place here. With a wealth of information available if one cares to look for it.
Now I know I've only mentioned highly technical pieces of software and their generous creators, but its much more than that. We have all kinds of people here that have something to bring to the table. In my humble opinion that's whats needed to continue to be innovative, tickle our curiosity etc. Most of the ideas I've chased here (in this thread) were triggered by something someone wrote (most often somewhere on this forum)...
Lots of the basic concepts I've picked up just reading along on lots of different topics. And I still do read more than I type, amazing isn't it? I know I do tend to type a lot!
I'm almost as exited about this latest project (the added filters) as when I was building the arrays and firing them up for the first time.
Triggered by Jack (nc535) and his continuous curiosity into the workings of different speakers by simming the ... out of them.
Without seeing what he was doing, and finally understanding why he was doing it, I would never have gotten to this part. I've always been curious about the idea(*), but without a way of "seeing what can be done" (by sims like Vituixcad) it would have been just that... curiosity about an idea.
Anyway, to me this is a big thing. One heck of a reason for me to continue to try and participate here. You never know where it might lead us next!

No idea where this (above) all came from, you'll have to excuse me.
I do think is awesome to be part of a sharing community like we see here. And it keeps getting better...

(*) = the idea of creating a frequency dependent kind of shading, I never followed up on it before, because it was so hard to predict/envision what it would do out in the room. The continuously developing tool-set at our disposal has made all the difference.

[end of rant... I think ]

[wesayso]

There is a lot of talk about DSP in this thread of mine... if anyone is lurking this thread, thinking about using some DSP, check out this interview with Mitch: The Intellectual People Podcast - Mitch Barnett of Accurate Sound (known on this forum as member mitchba).

When I was starting my own journey into DSP, I found a thread between Mitch, Bob Katz and Audiolense creator Bernt on the use of that software. That was like a crash-course for me to get up to speed about DSP software. Even though I was to use a different package, it really helped me to get a clear picture of what to expect etc. I've linked to that discussion at the time over here: The making of: The Two Towers (a 25 driver Full Range line array) Even though a lot of time has passed, there's still some good info to be found there.

[wesayso]

So, I've got those "horns" to deal with, reflection wise...
I figured I needed to find out the travel time difference for the bounce to reach my listening spot. (done that many weeks ago actually)



The difference in travel length was about 2.076 metre. Which is about a 6 ms delay. The one thing I did not do is look at one of many measurements made to see if I could find it there! Until late last night! I figured a bounce like that...


(unshaded sample with fluid's ABEC sim results)

... would have to show up somewhere, right? I can't imagine why that didn't go on any sooner...

So late last night, I've checked some graphs, the first one I found was this:


APL_TDA plot from 2016

It was there all along... right in front of my eyes... see the bump at ~6ms? And at about 4-5 KHz? even some traces there of sooner action from the floor.



Duh.... now there's only one thing left for me to wish/hope for... I sure hope my new (renovated) ceiling won't reflect more than my previous aluminium ceiling that we removed during the last summer. The bounce was quite soft in energy, as seen in other graphs I've made trough the years, but it has always been there, right in front of my eyes... Before installing my damping panel/poster, the back wall kind of arrived at a similar timing and I've always blamed that bump to be a residu of that. (panel not being large enough or something like that)

I also looked at some other's array plots I've kept trough the years and sure enough it is there on them too.

Another view of my situation:

[wesayso]

I guess I wasn't paying enough attention to my plots when I tried this:



Back in april 2015....

[nc535]

I love that picture! Reminds me of all the time I spent doing same/similar things...

[fluid]

Also visible in outdoor measurements too when you know what you are looking at

[wesayso]

Much easier to find something if you know what to expect .

[wesayso]

No work done on the array this weekend. As stated early on in this thread, my health isn't all that. So I determined it was a little too cold for me and I'll wait for better times.
I did manage to tidy up a DRC-FIR template to make it nice and clean and minimum phase. If any phase work is needed below ~200 Hz, I'll do it manually using RePhase.
That way I get to keep a cleaner IR, less ringing at high frequencies. Not that I've heard ringing, but trying to avoid it is even better (peace of mind).
If I let DRC-FIR do that job, it will also run up to higher frequencies or it will still create more 'haze" (at low SPL) at higher frequencies. Having the correction minimum phase throughout prevents that. It is what I used on my last corrections but the template could use a little work as it wasn't meant for 100% minimum phase yet.

Basically the difference between an impulse like this:



and



(both of them are Vituixcad simulations with DRC-FIR correction)