The making of: The Two Towers (a 25 driver Full Range line array) - Page 27 - diyAudio
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Old 27th January 2014, 10:24 AM   #261
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by wesayso View Post
True, that's why I looked into the radius backside mount solution. Did you compare the plots on that German site? There is less of a difference in the on axis / off axis plots with the back side mount plus radius compared to the flush mounted driver. The part that needs EQ is the slight boost the horn/waveguide shape gives.
That little 6mm waveguide gives a 3dB boost to the top end. This actually would change the op amp based analog EQ circuit that Bob Richards and I worked on but would not be an issue with the DSP that you plan to use. Ever since I got the miniDSP, I am not sure if I would ever go the analog circuit route anymore. I wonder if the phase changes that the EQ intrduces in the DSP implementation is better or worse than the analog implementation - or is it necessarily the same given the exact two same curves?
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Old 27th January 2014, 11:01 AM   #262
wesayso is offline wesayso  Netherlands
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Not sure I am competent enough to answer that (yet). That's one of the reasons I am working on two paths. One is with the Behringer DEQ as base, with upgraded analog input section and a proper DAC and the other path is using the PC as EQ from within JRiver Media Player.
That last option can use plugin EQ programs and has the advantage to play with minimum phase parametric EQ and phase linear EQ if the plugin is setup for that.
A plugin like PLParEQ comes to mind as well as other solutions like Audiolense and Acourate.
The advantage of both these solutions compared to the analog EQ circuit Bob and you worked on is the separate left/right EQ available to tailor the in room response (up to a point of coarse).
As no room is the same you would have to have some leverage left to tailor the response to the room. It will never be a one size fits all kind of solution I guess.
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Old 27th January 2014, 12:38 PM   #263
xrk971 is offline xrk971  United States
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The miniDSP has an option for a digital input via a USB to I2C daughter board. I wonder if keeping the signal all digital and applying EQ in digital domain removes the whole phase issue? Seems like it would because the EQ is a simple linear-phase 'chop off the bits' that don't fit prior to the DAC.

I might have to look into the USB-I2C option... hmmm...
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Old 27th January 2014, 02:15 PM   #264
kessito is offline kessito  Netherlands
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Hi guys,
Unless you use special fir filter, filters with the same gain curve Will always have the Same phase curve. This is because they are minimum phase, it doesnt matte rif they are analog or digital.
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Old 27th January 2014, 02:23 PM   #265
wesayso is offline wesayso  Netherlands
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That was my understanding as well. However a solution like PLParEQ does provide a phase linear phase EQ solution, right?

Quote:
Originally Posted by PLParEQ website:
PLParEQ™ Pro Series’s phase-linear operation is achieved by processing sound in both forward-time and reverse-time directions through classic filters—all in real time. This completely removes the phase warping caused by IIR filtering and applies their roll-off twice. Each filter type thus becomes two: one for classic IIR filtering and another for phase-linear operation.
PLParEQ website

I read about that plugin on StigErik's long and impressive thread on his OB setup...
The Behringer solution would be minimum phase, but my PC solution could be either one depending on the processing. Fir filters or a product like PLParEQ etc. do provide that linear phase option or so it seems.

Last edited by wesayso; 27th January 2014 at 02:36 PM.
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Old 27th January 2014, 02:39 PM   #266
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Hi,

Personally going with USB > miniSharc > DAC setup, so as I get more experience I can try out different PEQ, FIR filters etc... Note, USB > miniDSP via I2S, the playback sample rate would be set to that of the DSP unit [48 or 96KHz]... it's recommended to connect the USB boards via S/PDIF to the miniDigi first.

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Old 27th January 2014, 11:25 PM   #267
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Quote:
Originally Posted by kessito View Post
Hi guys,
Unless you use special fir filter, filters with the same gain curve Will always have the Same phase curve. This is because they are minimum phase, it doesnt matte rif they are analog or digital.
You are assuming that the filters are minimum phase. There's no reason for this to be true (Eg. see Linkwitz's ASP crossover)

There's a whole bunch of discussion on this in the thread over here
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Old 2nd February 2014, 06:35 PM   #268
Halair is offline Halair  Norway
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Wesayso - thank you for the inspiration, my interest i SLA have peaked!
Estethically speaking LA look extremely nice and apparently they do not lack fidelity... I have spent the better part of this weekend reading myself up on LA and it is starting to sink in

So my idea is similar to yours, vifa TC9's, in a single line array. Undecided about power tapering and such but realise EQ is in order. Probably wont do 25 per side so wont have floor-ceiling coverage but that rely on supply/cost of drivers. Vifa TC9will cost me about 25$ per speaker due to shipping cost and import/VAT rules. (Norway is expensive)...

Main application will be front speakers in my home theatre and the array itself be of same height as the screen (160cm). From what I've read SLA fair well in HT-applications.

My idea of construction in physically similar to yours except I intend to create a XPS-foam &plywood sandwich structure with MDF front baffle. Speakers might be rear mounted and MDF routed to form wave guide. Curved exteriors like you created are simply sexy

Haldor,
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Old 3rd February 2014, 11:21 AM   #269
wesayso is offline wesayso  Netherlands
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Hello Haldor,

Don't give up on the floor to ceiling extension just yet! Couldn't you import from Germany? I did! I wrote to several firms in Germany, the Netherlands and the US to get attractive pricing, you should be able to do better than that price.
A search for Vifa 9bn 119/8 should give more hits, also Peerless FR35/8. Those names are more commonly used in Europe. I bought the Peerless FR35/8 and when I received them they had a sticker on the back reading: TC9FD18-08 . Buying them in numbers (50+) should effect pricing as well.

If you do go shorter than ~ 70% of floor-ceiling power tapering should be considered.
Seeing you are building them for HT makes me assume the lower spectrum is going to be separate from the arrays. At least that's what I would do for HT.

Are you going to cover the XPS-foam and ply sandwich? What do you have in mind exactly?
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Old 3rd February 2014, 12:19 PM   #270
Halair is offline Halair  Norway
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wesayso - thanks for the reply

I have asked for a quote from Madisound and with shipping and VAT price will equal about 18$ (€12) per speaker - if I go for 50 units. I will source Germany or other EU-sided options aswell to see if I can find them any cheaper over there.

My use will be mainly HT but I properly enjoy listening to music also so they need to fit both uses. The overall ceiling height in my HT is 210cm but I also have a 40cm deep, 20cm high soffit running the full circumference of the room. That mean I have 190cm floor-soffit height available while the room itself is 210. With a 160cm high array I have about 75% coverage, but if I go for 50units adding the extra height is a trivial addition. With 190cm arrays I will achieve 90% coverage = 20 speakers per side.

Pic of the room before it was completed:
Click the image to open in full size.
(B&W 603's replaced with B&W DM604 which I use today, screen size is 270x160cm and viewing/listening distance is 3-3,2m )


I do intend to add subs to cover the lower spectrum but that will take a while, an DIY array is a lot of work already

As far as the sandwich construction goes I plan on the following sequence, from outside to inside:
Outer finish Laquer or staining / Veneer / XPS / Epoxy & Fiberglass or veneer. Front baffle MDF. The veneer will add a stiff outer surface providing some ding resistance plus texture. I have quite a lot of experience with this construction method from my RC-planes background. The horisontal layer of stained wood on yours look exceptionally great, I would consider something similar for mine if I can source suitable veneer. If horisontal layers are available I will need an extra layer (epoxy & cloth) under the veneer to control vertical stress of the array. Still absorbing as much info about arrays as possible, things might change during this process but as far as I can tell this could work well

Last edited by Halair; 3rd February 2014 at 12:22 PM.
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