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Old 24th February 2017, 03:13 AM   #11
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Quote:
Originally Posted by wreckingball View Post
...This set of panels will be in my basement HT, and I have a height restriction of around 60", but I'd also like to produce as much SPL as possible...
I see I'm a little late to the party and pretty much all your questions have been addressed.
But, I have a few of my own.

What is the floor-to-ceiling distance?
You mention a height restriction of around 60", is that because of the floor-to-ceiling distance?

If you want to maximum SPL for a given ESL size, you move the crossover frequency up as high as possible. If you do that, the best ESL to woofer matching is had with a line source of mid-woofers like Calvin does. Is this something you might consider? do you have the room? or do you want to stick with the T-line woofer you mentioned.
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Old 24th February 2017, 08:32 PM   #12
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Hi Steve and Rod,
No worries on being late to the party, this is going to be a slow build anyway, I'm just grateful to have you folks with lots of experience and knowledge replying

Rod, thanks for expanding on Calvin's response, this is indeed going to be a hybrid panel, so I can use my existing bias supply and transformers, (and tweaks if needed).
The panel cannot extend from floor to ceiling because my basement has HVAC plus the main 8"x8" support beam running across (full length, L to R) the ceiling that would limit my height to around 6 feet, that's why I wanted to limit the panel itself to around 5 (60"). (more on that later)

Steve, I had not considered using a tower of mids, as my t-line seems to blend pretty well with the panel. BUT, You and Calvin both have mentioned this before, so if the benefits outweigh the cost/time, I may think about it.. put it that way.
From the floor to ceiling joists measures 7' on the nose, but like I said, the HVAC and that beam bring it to roughly 6' for line of sight/sound.

A question:
I'm assuming the panel should not be in the path of the obstructions, but could I make it a full 6'? Or does the sound travel upwards a bit on an angle? (I'm not sure/forgot about dispersion on the vertical plane)

SPL and x-over point decision: The reason I want the panel to cover down to around 200-220Hz, is simply that hearing is the most critical from around 300 (general conclusion) and want a little leeway for the x-over to roll off. That and I want the majority of sound to emanate from the ESL (within my constraints) due to the low THD etc. ..who wouldn't?
This is why I asked about a wider panel producing more SPL, and had not considered a mid-tower.
Now I guess I'm asking about height also producing more SPL, but big SPL is not the main goal or anything, maybe I should de-emphasize that. I hope worded that right (?)

As usual, correct me if I'm wrong/off track, thanks much..

Cheers
-Steve
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Last edited by wreckingball; 24th February 2017 at 08:56 PM.
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Old 24th February 2017, 09:31 PM   #13
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Ran out of time on editing.
As far as the obstructions, I just don't want there to be any nasty reflection that could negatively affect the sound.

I'm assuming the mid tower was mentioned to be able to set ESL x-over higher, concurrently facilitating higher SPL along with such a setup.


But let's back up for a minute about SPL expectations.
I'd like to be able to achieve the SPL of a rock concert at my listening position when watching a concert DVD.
I'd also like a movie to be able to hit IMAX theater levels when watching a movie, or maybe a bit louder if the mood strikes.
(I was able to get to these levels with my flat and with my curved panels, but didn't have much headroom left, {I don't think/just a hunch})

What are we talking, dB wise, to achieve this?
Let's just start there and see where this goes...
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Last edited by wreckingball; 24th February 2017 at 09:43 PM.
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Old 24th February 2017, 09:56 PM   #14
golfnut is offline golfnut  New Zealand
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Hi

As I may have mentioned earlier, the ideal line source is infinitely long and produces a cylindrical wavefront. (Conventional speakers mimic point sources - which produce a spherical wavefront.)

We mimic this behaviour with a finite linesource by exploiting reflections from the floor and ceiling. You could also think of the ESL producing a cylindrical wave that is not allowed to disperse in the vertical direction because it is trapped by the floor and ceiling.

So, ideally, the ESL should occupy the full height, and the floors and ceilings should be good acoustic mirrors.

In one of the other threads (DIY planar magnetic + open baffle woofer array around post # 172) there was a bit of discussion about the effects of a speaker that is not full height. Fair to say that its complicated, but the taller the better.

I also wonder about the obstructions on the ceiling that you describe. The effects are probably not significant, but you might find that it sounds slightly better facing the direction where the reflections are least obstructed.

Because (i) the source is a line rather than a point, and (ii) it has a dipole radiation pattern - not much out the sides, a lot of the potential problems with room reflections are reduced. My lounge is two rooms of different sizes with the wall removed - and has a terrible resonance with conventional speakers - disappears with ESLs. This may be a bi mitigating factor in your awkward space.
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Old 24th February 2017, 10:35 PM   #15
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Hmm, so it may not be a problem? Interesting.

However take a look at these pictures, two are my HT showing the floor and ceiling, plus the obstructions. The one doesn't show the beam, second one does.
Also, the ceiling pic is deceiving, the HVAC looks a lot lower than the beam that runs the length, but it's only 3 inches lower. (don't mind the mess or the speaker mismatch, theater under upheaval)

As far as moving ESLs, I cannot, as the posts that support the beam would be in the middle of the screen, this setup orientation is pretty much set in stone.

Just for fun, the 3rd pic is my new IB sub I'll be using once I mount it to the ceiling.
4 1200w-rms 18's driven with an iNuke DSP-6000, should be massive sounding (probably for movies only)

Cheers
-Steve
Attached Images
File Type: jpg Obstruction 1.jpg (638.5 KB, 15 views)
File Type: jpg Obstruction 2.jpg (488.8 KB, 210 views)
File Type: jpg Infinite Baffle.jpg (719.6 KB, 206 views)
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Last edited by wreckingball; 24th February 2017 at 10:41 PM.
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Old 24th February 2017, 11:39 PM   #16
golfnut is offline golfnut  New Zealand
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Hmmm, does not too bad at all. I did notice a couple of things conspicuous by their absence though - a lazy boy and a beer fridge
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Old 25th February 2017, 12:08 AM   #17
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Originally Posted by golfnut View Post
Hmmm, does not too bad at all. I did notice a couple of things conspicuous by their absence though - a lazy boy and a beer fridge
LOL...Lazy Boy to the right, beer fridge to the left of pic.
What? ..you think I'd really do without the essentials?

Meanwhile, back at the design table,
So you think I could benefit from a full, floor-to-ceiling ESL here, without any sonic concerns introduced by the obstructions?
Seems problematic from an inexperienced point of view, but what do I know?

Only thing I'm recalling is your post about needing different transformers for this type of setup, am I not recalling correctly?

-Steve
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Last edited by wreckingball; 25th February 2017 at 12:19 AM.
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Old 25th February 2017, 12:36 AM   #18
golfnut is offline golfnut  New Zealand
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HI - I assumed you were still talking about a hybrid.

The problems with transformers are with the full range ESL. Getting good voltage rating at 50 Hz + good step-up ratio + bandwidth ~20 kHz requires some care. If you take the heatoff by chasing 200 Hz bottom end instead of 50 Hz, then transformer is very much easier.

A line-source will reproduce good SPL down to f =c.r/h^2, where c is speed of sound, 340 m/s, r is listening distance, and h is height of speaker

To get to 200 Hz at 3 m listening distance requires a 2.2m high speaker, so reflections will still help the hybrid. No need to go all the way to ceiling, just a good fraction of the distance in a normal room I guess curtain height or a touch more is probably sufficient. The WAF gets rapidly worse, and they can be a pain in the butt to move about if they are too tall.
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Old 25th February 2017, 03:29 AM   #19
Calvin is offline Calvin  Germany
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Hi,

there are circumstances that apply to theory ... and only theory ... and there are circumstances that apply for praxis.
From my experience I'd say that the Q of panel height almost vanishes when a height of 1m is passed.
I'd rather concentrate on more practical aspects.
The higher and wider the panel builds the more difficult will it be to build precise.
A good and precise build will gain You more on SPLmax. and stable performance than the Q of 50" or 60" height.
Keep things practical and handy.
Just by perfecting the whole building process and improved application process of a new membrane coating the efficiency of my newest panels increased by almost 6dB (had been >90dB@4m already, at a bias of only 2.2-2.5kV)
Couldn't believe it at first, but measurements prooved the figures.
Actually the bass tower with its 8pcs of 6.5" long stroke drivers limits a tad earlier than the panel.
I'd suggest a panel slightly higher than the one to the left of Your pic and certainly not higher than the one on the right side.
I'd make it slightly shorter and fit a heavy base beneath that'd contain the electronics.
Provide for a as small as possible but very stiff mounting frame.
You'll need some means to prevent the top end of the panel/frame to move ... kind of stiffening beam from top to base plate ... or maybe even fixing to the ceiling.
Add a mid-bass tower -Dipole if possible- covering the range from ~200Hz down to 60-50Hz ... driver size 5"-7" ... capable of at least +-4mm linear stroke.
If Dipole tower -that guarantees for a seamless transition to the panel- but also as CB tower I wouldn't recommend a xover from mid-bass to panel higher than 250Hz, as comb filter effects will spoil the horizontal distribution.
Even at 200Hz the listeners off of the axis will recognize the effect .... going higher in xover frequency the effect becomes more and more obvious and disturbing.
If done right amplifiers delivering stable 100W will fully suffice to drive the panel as well as the bass.

jauu
Calvin
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Old 2nd March 2017, 12:10 AM   #20
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@ Rod: No no, I was just thinking/typing out loud, still going with hybrid for SPL and other reasons.. (many)

Calvin is right, no need to further complicate things when a simple design is far from perfected, not to mention construction issues that could arise from biting off more than I can chew...

Hopefully, by the end of the weekend, I'll have a solid plan.
If not I'll have more questions ...still mulling things over..

Thanks for your indulgence..
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