Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Corner Floor-to-Ceiling Line Array Using Vifa TC9
Corner Floor-to-Ceiling Line Array Using Vifa TC9
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th December 2015, 05:26 AM   #1
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Corner Floor-to-Ceiling Line Array Using Vifa TC9
Default Corner Floor-to-Ceiling Line Array Using Vifa TC9

Short story: Corner line arrays can save space, can eliminate ceiling and front wall reflections, and can be fairly efficient. Using 24 Vifa TC9s, a 3.5" full range driver, a corner floor to ceiling line array was created. The array measures and sounds pretty awesome and achieves the design goals.

Corner Floor-to-Ceiling Line Array Using Vifa TC9-img_1794-jpg

Long story: If you read Toole and other research, it says that the reflections that color the sound the most are the ceiling and front wall (the wall behind speakers). Reflections from side walls can add a sense of spaciousness but reflections from the ceiling and floor are perceived as modifying the frequency response.

Horns can be used to prevent ceiling and front wall reflections, but to control reflections at mid frequencies (sub 500 Hz) requires large horns. There are some active threads with folks trying to solve this problem by using cardoid cabinets for woofers, which is a pretty cool way of doing things, but there are problems.

I played with horns for a while and I could get good sound using Altec VOTT mid horns and constant directivity SEOS horns, but the sound was never quite of the peerless variety. The balance of the HF with the rest of the spectrum was never quite right. Horn speakers also tend to be big and occupy a lot of space and this annoyed me. And thus were born some design requirements. The new speaker should:
1. occupy less space,
2. control ceiling and front wall reflections, especially in the lower frequencies (below 500 Hz),
3. have a smooth on-axis response and uniform off-axis response and,
4. be fairly efficient, have low distortion, and have the dynamic headroom to hit 110 db peaks.

Toole kind of gives it away in his book that an ideal floor-to-ceiling line array would solve some of the key issues in sound reproduction in the home (figure 18.3). He describes the Keele CBT array as a practical implementation of an ideal floor-to-ceiling array with perfect drivers.

From here, putting the arrays in the corner was a no-brainer. It would completely get rid of the front wall reflection, and the floor-to-ceiling nature of the array would avoid ceiling reflections also. And I had a room that allowed a corner design.

The next question was the choice of drivers. Keele’s CBT uses a cone and a dome. But his arrays are relatively short. The floor-to-ceiling array would need a lot more drivers, meaning more cost, more wiring, and more worrying about unit to unit consistency.

If a smallish full range driver was to be used, the Vifa TC9 was an obvious choice. It has one of the smoothest frequency responses amongst full range drivers, a low distortion motor, and with Vifa manufacturing it, you could be relatively assured that there would be good unit to unit consistency. There are many designs here on diyAudio that use this driver. The Manzanita OB uses this driver. And many others have used it in their design. Seeing it used in Wesayso’s heroic tower build and other line array builds sealed the deal. Plus the TC9s are relatively cheap and I love cheap .

The construction is relatively straight forward. It’s a three-sided cabinet. The front baffle is as narrow as possible so that the drivers can be as close to the corner as possible. The drivers are flush with the front baffle. I had this design in my mind for at least a year but never got around to building it. Finally, after months of frustration at never finding the time to build the cabinets, I asked my friend John (carpenter) to build the cabinets and wire up the drivers.

John completed the build and the arrays are playing music. They occupy very little space, can go plenty loud, are pretty efficient and very low distortion (each driver is barely moving even at loud levels). Using a single 3.5” driver ensures a uniform off-axis response up to a high frequency, above which the Vifa does start to beam, but it is relatively well controlled. The on-axis response is flattened using DRC software, i.e., automatic room correction. The final result is quite good. Measurements coming up shortly. There is still a long way to go. The EQ is doing a pretty good job, but I think it can be better.
Attached Images
File Type: jpg IMG_1794.JPG (77.3 KB, 6002 views)
File Type: jpg IMG_1797.JPG (93.8 KB, 2905 views)
File Type: jpg IMG_1798.JPG (100.0 KB, 2733 views)
File Type: jpg IMG_1800.JPG (112.6 KB, 2700 views)
  Reply With Quote
Old 27th December 2015, 05:48 AM   #2
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Corner Floor-to-Ceiling Line Array Using Vifa TC9
Default Measurements

I wanted the drivers to be as close to the wall corner as possible and so that limited how wide the cabinet could be. And it was always going to be 7'-0" tall, the height of the ceiling. The cabinet dimensions sort of limit the bass extension. I can throw power at it and get it flat, but I am not doing that because I use a separate sub and am building two more at the moment. Besides, the resonant frequency of the TC9 is 125 Hz and it may not be a good idea to push it much below that region.

The measurement is made at the couch, just below and behind the projector. It is more than 12 feet away from the speaker. The HF has a 6 db boost past 4 kHz in all the uncorrected measurements. The uncorrected measurements show a pretty impressive impulse response. It is almost the perfect Dirac pulse. But one would expect that given the even frequency and nearly flat phase.

The uncorrected measurements are fed to DRC and the corrected response is convolved through JRiver. The corrected impulse does show some ringing. I suspect it is related to the measurement setup, or it could be that the subwoofer kicks in much before the array. Needs some investigating.

Uncorrected Left FR and phase:
Corner Floor-to-Ceiling Line Array Using Vifa TC9-left_spl_phase-jpg

Uncorrected Right FR and phase:

Corner Floor-to-Ceiling Line Array Using Vifa TC9-right_spl_phase-jpg

Uncorrected impulse response:
Corner Floor-to-Ceiling Line Array Using Vifa TC9-impulse_response_uncorr-jpg

Corrected impulse response:
Corner Floor-to-Ceiling Line Array Using Vifa TC9-impulse_response_corr-jpg

Corrected FR with sub 1/48th Octave smoothing:
Corner Floor-to-Ceiling Line Array Using Vifa TC9-impulse_response_corr_unsmoothed-jpg

Corrected FR with sub ERB smoothing in REW:
Corner Floor-to-Ceiling Line Array Using Vifa TC9-l_r_corr_response-jpg
Attached Images
File Type: jpg Left_SPL_Phase.jpg (89.7 KB, 2996 views)
File Type: jpg Right_SPL_Phase.jpg (91.7 KB, 2976 views)
File Type: jpg Impulse_Response_Uncorr.jpg (68.6 KB, 2978 views)
File Type: jpg Impulse_Response_Corr.jpg (69.0 KB, 2969 views)
File Type: jpg Impulse_Response_Corr_UnSmoothed.jpg (95.9 KB, 3198 views)
File Type: jpg L_R_Corr_Response.jpg (72.1 KB, 2938 views)
  Reply With Quote
Old 27th December 2015, 06:02 AM   #3
thunk303 is offline thunk303  Australia
diyAudio Member
 
thunk303's Avatar
 
Join Date: Mar 2005
Location: Eltham, Melbourne, Australia
Well done mate.

Although they need more eq work, what's your initial impressions compared to the horn system.?

Dean
__________________
http://nomadessentials.com.au
  Reply With Quote
Old 27th December 2015, 06:11 AM   #4
bwaslo is offline bwaslo  United States
Old guy with soldering iron
diyAudio Member
 
bwaslo's Avatar
 
Join Date: May 2006
Location: Portland, Oregon!
Corner Floor-to-Ceiling Line Array Using Vifa TC9
Looks pretty impressive. But is the corrected IR response graphic right? L and R look a lot different from each other, like the L is actually the uncorrected maybe?

What DRC are you using? FIR based or IIR? And is it auto, or are you doing it manually with something like RePhase?

I've always seen best result from manual, but no experience with more modern setups like Dirac, maybe they do better. If you aren't already, I'd recommend eqing from relatively near to the speakers (so you are acting on the speakers, not on position sensitive room effects). You do not want to try to eq out reflections coming from behind you, particularly at above 400Hz or so.
__________________
[W9MJE] Horn spreadsheet SynergyCalc/; SmallSyns SmallSyns;
Crossover design Xsim; Depot diffusor super-easy diffusors
  Reply With Quote
Old 27th December 2015, 06:15 AM   #5
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Corner Floor-to-Ceiling Line Array Using Vifa TC9
@thunk303, Thanks. I know it looks bad (sort of) but it sounds fantastic. The response at the listening position is so smooth and "liquidy" and they do the "you are there" thing very well. DRC does a fantastic job at EQ.

Apart from the audiophile qualities, the one thing this speaker does that no other has done before is that it relaxes me. The music just draws me in and makes me pay less attention to all the nonsense we like to worry about.
  Reply With Quote
Old 27th December 2015, 06:24 AM   #6
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Corner Floor-to-Ceiling Line Array Using Vifa TC9
Quote:
Originally Posted by bwaslo View Post
Looks pretty impressive. But is the corrected IR response graphic right? L and R look a lot different from each other, like the L is actually the uncorrected maybe?

What DRC are you using? FIR based or IIR? And is it auto, or are you doing it manually with something like RePhase?

I've always seen best result from manual, but no experience with more modern setups like Dirac, maybe they do better. If you aren't already, I'd recommend eqing from relatively near to the speakers (so you are acting on the speakers, not on position sensitive room effects). You do not want to try to eq out reflections coming from behind you, particularly at above 400Hz or so.
Yes, it's correct. I know it looks bad and I do need to investigate. It is either the loop through (i.e., my convoluted measurement setup) or it is the subwoofer that does not have the right delay. But the proof is in the pudding, and the pudding tastes quite good I'll measure the arrays only (no sub) tomorrow and see what I get. The uncorrected measurement does not have the sub in it.

I am using DRC (DRC: Digital Room Correction), which is a free, auto correction software. It is quite brilliant. It uses a variable window for calculating the response to be corrected, i.e., short for HF, long for LF and smoothly varying in between. It also allows to change the windowing. It is kind of arcane, relatively speaking, but you (Bill) shouldn't have a problem with it. There is also a user guide on diyaudio with custom scripts to get you started (A convolution based alternative to electrical loudspeaker correction networks). I use the original ERB setting, which the software designer (Dennis) says matches the ear's response the best. REW has also recently introduced variable filtering. It also has psychoacoustic and ERB filters.

I used to think about EQ'ing the direct sound only, but DRC recommends measuring at the listening position. Dennis uses something called the spectral envelope to do the correction (DRC: Digital Room Correction). All I can say is that it sounds pretty fantastic. I have used rePhase to do manual correction and DRC is leagues ahead.

Last edited by ra7; 27th December 2015 at 06:28 AM.
  Reply With Quote
Old 27th December 2015, 10:11 AM   #7
wesayso is offline wesayso  Netherlands
diyAudio Member
 
wesayso's Avatar
 
Join Date: Jul 2007
Quote:
Originally Posted by ra7 View Post
Apart from the audiophile qualities, the one thing this speaker does that no other has done before is that it relaxes me. The music just draws me in and makes me pay less attention to all the nonsense we like to worry about.
Lol! Exactly mimicking my original response to my arrays. I listened and thought: Should I really worry about woofers, tweeters and crossovers? Forget about it, just listen to the music!

I'm sure you'll be able to evolve them like I did. I'm jealous about your symmetrical setup though. What is the volume for each separate driver?

I do push the tiny drivers trough the impedance peak, which is still passively corrected with a conjugate network, even though I could not find definitive answers if that helped or not. Listening to it seemed to win me over but that may very well be a mind game. No answer from me there yet. But the cones still only move a small amount. Unless you play something like "A Perfect Circle - Lullaby". But even then they cope and bring unbelievable pressure from such tiny cones. My amp runs out of steam before the arrays do.

Try "Rodrigo y Gabriella - Hanuman" or other songs from the album 11-11 and play it loud. It's all midrange and very convincing. You will be there, listening to them play.

Kind of worried here (lol) not listening to flat on axis? Me neither .
  Reply With Quote
Old 27th December 2015, 12:32 PM   #8
wesayso is offline wesayso  Netherlands
diyAudio Member
 
wesayso's Avatar
 
Join Date: Jul 2007
A couple more questions if I may. What does the phase of the corrected signal look like?

Maybe you're up for showing a 4 cycle frequency dependant window for me to compare to? And I'd like to see a spectrum plot. I bet your setup has advantages to mine. That corner placement has to have advantages.

When listening to "Jenifer Warnes - Bird on a Wire, what imaging do you get, something like this:
Click the image to open in full size.

Or closer to this one:
Click the image to open in full size.

From: B&O Tech: What is “Beam Width Control”? earfluff and eyecandy

Personally I have to listen again, at one point you hear Jenifer herself next to the central placed voice but moved a little back. Too bad it doesn't display on the graph. Unless it's the "bk" which makes sense. My cow bell and triangle (on left side) were more forward in the room. Have to listen again for the choir.

Had a lot of fun comparing maps...

Last edited by wesayso; 27th December 2015 at 12:36 PM.
  Reply With Quote
Old 27th December 2015, 01:44 PM   #9
Juhazi is offline Juhazi  Finland
diyAudio Member
 
Juhazi's Avatar
 
Join Date: Mar 2007
Location: Jyväskylä, Finland
Congratulations, ra7!
You have the benefit of having a dedicated AV room with symmetrical cornered loudspeakers - many acoustic problems avoided. DRC is doing the job well and you can easily adjust response to your taste. Your descending response is "standard" and gives fuul-bodied sound without chestiness/boominess etc. Obviously also room modes are minimal at your measuring point.

About construction - does each driver have it's own airspace?
I am dreaming of having same construcion in my HT room some day. I would have to tear down a bit of bookshelves though and there is no room for contents... (my vintage LPs and photo slides, remember those?)

Obviously you have read this classic https://www.trueaudio.com/array/
__________________
AINOgradient speaker project
  Reply With Quote
Old 27th December 2015, 05:40 PM   #10
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
Quote:
Originally Posted by ra7 View Post
I wanted the drivers to be as close to the wall
Uncorrected Left FR and phase:

Uncorrected impulse response:
Corner Floor-to-Ceiling Line Array Using Vifa TC9-impulse_response_uncorr-jpg

Corrected impulse response:
Corner Floor-to-Ceiling Line Array Using Vifa TC9-impulse_response_corr-jpg
Very nice, but are you sure you are measuring the right speakers?

I thought I read somewhere that one constant criticism of line arrays made up of multiple transducers was the inability to have a clean impulse response. It seems you have solved it rather nicely by picking larger drivers.

Best,


Erik
  Reply With Quote

Reply


Corner Floor-to-Ceiling Line Array Using Vifa TC9Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Floor-to-ceiling array vs CBT jeno Multi-Way 293 17th April 2018 04:16 PM
MCLA (Murphy Corner Line Array) project Dmontella Full Range 12 27th March 2012 03:47 PM
Line array corner sub Hezz Subwoofers 76 1st May 2006 05:37 AM
Line array behavior with corner placement johninCR Multi-Way 8 19th August 2005 02:52 PM
Line Array Corner Horn for any 4" driver johninCR Multi-Way 42 1st December 2004 05:13 PM


New To Site? Need Help?

All times are GMT. The time now is 05:18 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki