chrisb said:
How is running an second pair of speakers on the side any different than using phantom mode? Its the same thing.
"acoustically perforated screen to allow placement of the entire audio front row out of sight" - you mean a bed sheet of course, but why is that not an option? I built a friend an 8 foot screen with a project (720p) for less than $1000. Thats less than a cheap small LCD. Forget about the "pro" projectors. Just get an Optoma in your price range and go to the linens goods store for a $20 screen. AND STAY AWAY FROM SALESMEN!
chrisb said:
I don't get it. Your wife doesn't like movies? She likes small screens? My wife uses the theater just as much as I do. How is a TV any better looking than a screen? What am I missing here? My friends wife loved the theater, and most of all she loved the price.
If looking at small screens with poor sound is your idea of entertainment then I guess thats up to you. The money that I save NOT going to a theater for good viewing easily paid for all the equipment in a year or two. Movies on a small TV just don't do it for me. Sorry.
I mean if you live in a very small appartment with only one room or two then you do have a problem - you have the wrong hobby, but other than that I just can't see how my approach is not possible. Its worked well for everyone that I've done it for. One guy even did it in his one bedroom apartment.
gedlee said:
There is of course no "correct" reply to any of this, nor if I may say so without petulance, is there the need for any of us to justify the degree to which we pursue the goals of our entertainment.
Like many forum posters, I've played in this sandbox for most of my life (over 40yrs), and have had the opportunity to own an experience a wide range of gear, name dropping from the list is totally pointless.
Are my expectations different from those of yourself and your clients? Apparently - but never have I had as much fun listening or tinkering as in the past 5yrs. So, no this hobby is not wrong for me - indeed it has never been more right.
If it matters, I don't reside in an apartment. There are a couple of TV's in the house, the most recent upgrade was a 42" HD Plasma - just the right size for the room decor, and good enough for me -and no we don't watch a lot of movies. Indeed since installing the HD cable box over a year ago, the DVD player hasn't even been plugged in. My wife has a very stressful job, and would far rather be in the garden or doing yoga in her personal time than investing the emotional energy required to fully enjoy the home theatrical experience. For her TV is mostly pre-bedtime hypnotherapy, and I've certainly learned to give her that time & space.
gedlee said:
um, isn't that exactly where it should be? Perhaps you missed that we were talking specifically about creating a phantom with the Center Channel of the front 3 - the L&R mains are still used as well * (so there are indeed 4 speakers on the front row, plus as many subs as the room requires, plus the surrounds, et al)
Every conversation I've ever heard on the subject of location of a CC enclosure relates to the compromises derived from placement on a different vertical plane than the main L&R channels.
Of course, after about 5yrs of trying to tolerate a 5.1system, I trashed it all in favor of HT2.0 (i.e. vanilla stereo) - with teeny little FR drivers to boot, so we're obviously talking a different language.
* edited for "clarification" - at least I thought it was
gedlee said:
My setup has the centre channel going to the centre channel speaker. This is currently on a 5 gallon paint bucket, in front of the equipment unit that has the TV on top.
I wouldn't even consider sending centre channel to the left and right mains.
With 2 centre channel speakers, one on either side of the screen, the image is projected to the centre of the screen. Beautiful!
gedlee said:
The words out of my first wifes mouth would be: "not in my room you don't, Fokker. What's next? Confederate flags as window curtains??"
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chrisb said:
That sounds like a really bad solution to me, on sonic, aesthetic, and budgetary grounds. Sonically, two speakers doing the same thing in close proximity can only lead to comb filtering and an attendant narrowing of the sweet spot. Sure, it might sound better than a toppled-MTM center, but realistically, what doesn't sound better than a toppled-MTM center?
Aesthetically, it means yet another big box in front. Who wants that?
Budget-wise, there's that whole superfluous speaker to build.
So I wouldn't do double-centers under any circumstances I can conceive.
I don't know if it'll work as well with Dr. Geddes' kits as it does with the speakers I use - 12" Tannoy Dual Concentrics, though I wouldn't be using those if the Nathan10 kit had come out ~18mos ago! - and I'll leave that to people who have measured and heard the design to answer, but what I do is to have all three front speakers up high. The midpoint of my Duals is roughly 60" off the ground, and the TV* fits nicely just under and slightly behind the bottom of my center channel's baffle. The image doesn't sound like it's way above my head, and as an added bonus the highs sound just as good when I'm standing as when I'm sitting.
But I also have a question for Dr. Geddes. Admittedly, this thread might not be the right place to ask, but it has the virtue of having your attention. I'm curious about your use of bandpass subs. Assuming your subs are as big as the AI ones, that makes each of them larger than my sealed ULF sub, which uses an 18" driver in a closed 24" cube. Moreover, one of AA bandpass subs is bigger than all three of the 12" + 12" passive radiator subs I am planning to build (I have the parts on hand from a previous project) to smooth out room response in my room, to be placed per your guidance on a couple threads here. (Big one in the corner, others placed randomly, as far apart from each other as possible with one above the floor-ceiling centerline.) Are there audible benefits to using bandpass subs thusly (as opposed to sealed/vented), beyond the built-in top end rolloff and possibly the efficiency gain? Moreover, were I to make my "BB" subs bandpass designs, it seems they would be much bigger than the PR designs, with lesser extension and only a little bit more efficiency. (At least 4th order; I don't know of a Mac-compatible program that will model 6th order bandpasses.) In addition to the receiver's crossover, the amps I use have a DSP built in that provides flexible crossovers, shelf-filters, and 5 or 6 bands of parametric EQ for each driver, so shaping the top end of the "BB" subs' response is pretty easy. The drivers themselves (Peerless's XLS12, aka 830500) are low-inductance and have clean measured performance to ~500Hz, so I'm not convinced that distortion would be much reduced with a bandpass enclosure, either. (Though I could be wrong.) Still, is there an important part of the picture I'm missing that makes bandpass enclosures a superior choice for a multichannel music system that occasionally is used to watch movies and such?
*Said TV is a 46" Sony LCD. The right-side wall of my living/listening room of my condo has a double-door to a balcony that's usually only partially draped. I borrowed a decent projector from a friend and tried it with with a sheet before buying it but even in daylight CNN viewing. Maybe something coarser than the Frette I ripped from atop my bed would've done better, but it was really washed out. The LCD does fine day or night, and though it's 2+ feet smaller than the THX screen size recommendation it seems sufficient to me.
chrisb said:
I meant no disrespect to your lifestyle decisions, but then your original comment "Earl, not all of us have domestic partners understanding enough to tolerate the bedsheet screen" wasn't really the point, was it? You aren't interested in Home Theater, thats the issue. If you and your wife were interested then there are very practical solutions as I pointed out. If your not interested thats fine too. But MY wife has nothing to do with it either way.
Pallas said:
At what frequencies would drivers separated by the width of a "big" screen start to develop these issues?
no argument there
Perhaps since the CC doesn't have the same spectral power requirements as the mains, they wouldn't have to be as large, and since this is a DIY forum, as John said earlier, I personally never overlook an excuse to build another enclosure.
but enough OT prattling from me
chrisb said:
That would depend, of course, on the width by which the drivers reproducing the same spectrum are separated. But generally, probably starting in the lower mids.
chrisb said:
The center, if anything, has greater demands placed on it than the left and right speakers. And I don't see why one would possibly want to build non-identical speakers up front, assuming a coherent sonic image is the goal. Should the left and right speakers be of different designs, too?
And the way I see it, the more building one does the less listening one can do.
Pallas said:
I agree, but I'm done arguing this point.
I would think those attributes sufficient, but its LF extension that is more my reason for using them.
I have not found it possible to make a smaller sub than bandpass that operates over the same bandwidth - assuming a given driver of course. Remember that a bandpass designs response is symmetrical about the drivers Fs in its rear box, but a ported or PR system has the drivers Fs at the lower edge. Thus the bandpass will virtually always go further down in frequency than the ported solution for the same total volume. This is what I have found. The bandpass in this configuraton tends to be less efficient than the ported, but its -6dB point is lower. Its the bandwidth extension that I am looking for not the efficiency. I use several subs so efficiency is not a big deal. Wide bandwidth with a low HP in a small box is where these designs work well.
An 8 ft^3 sub is pretty big. One of our BB subs is a 15 and is larger (about 2 ft^3), but the 12" sub is pretty small (maybe 1 ft^3). My recollection of the sizes and what you are saying don't seem to jib
gedlee said:
It also seems to me, though, that the port resonances are a big reason not to go that route. As I understand it, you use multiple ports of varying lengths to spread out the port resonances
gedlee said:
Hmm. Using the drivers I have on hand (Peerless's XLS12) the best 4th order BP design Unibox comes up with has a total volume of about 32.5L, F6's of about 25Hz and 90Hz, but exceeds xmax with 250W below 26Hz.
My passive radiator design (which, to be sure, is basically Peerless's design from their application note for this driver, but tuned a little lower) is 35L with an Fb of 20Hz. has a natively higher F6 (35Hz) but roughly the same modeled output with 250W at 30Hz (~104dB) and overall more area under the curve down to 20Hz, with the driver not reaching xmax until 16Hz with 250W and the PR hitting xmax at 24Hz. So, with the same power and an amp that provides shelf filters and parametric EQ bands, it would seem that the PR system could both go lower and get louder at LF before hitting xmax. Maybe I need to play with the BP parameters more, but it seems to me that, for this woofer at least, a PR might be the better option. (At least assuming one already has the PR's on hand, because with the dollar collapse and such Danish drivers have gotten pretty pricey.)
gedlee said:
The AI website list all of the BB and ULF subs as measuring 31.5"H x 23.6" W x 23.6" D, though looking at the pictures that does not make any sense and on further reflection those specs are probably erroneously cut-and-pasted from the ULF18's dimensions. But those are the numbers I was using. If your 12" is about a cube, than each one would be smaller than what I was planning (1.25 ft^3).
MJL21193 said:
I know. The further apart the speakers are, the lower negative effects start. Look at the size of the wavelengths of different frequencies. Think about a toppled-MTM. They sound awful because two points are playing the same signal from different points. A typical 7" toppled-MTM probably has those two sources about a foot apart, and the power response starts to fall apart above ~1.5kHz. Put the sources closer together, and that point will go up. Spread them out, and it will go down. Fundamentally, there's no difference between having the two sources playing the exact same signal in one box (the toppled-MTM we both agree sucks) and putting them in different boxes.
MJL21193 said:
All speakers need to be especially good in the vocal range, and well-placed! From my experience, even the better "matched" prefab home theater LCR sets (Paradigm, Revel, KEF, Tannoy, etc.) sound like incoherent mush compared to simply using three of the same speakers across the front. Even if the center is "better" than the mains.
Pallas said:
They can be in the ULF subs, but never in the BB subs.
The Ai website has a lot of typos. Its not in my control. The polar plots are correct because I did those, but the numbers have all kinds of errors.
I can't say what your simulation program does, mine doesn't show that for the drivers that I use. I would never use a PR because of the cost - ports are cheap and the PR doesn't get you anything but low loss, which a large port can do also. Maybe I'll run a sim and post it. Not much time for that these days.
When I was at Ai I looked at lots of options and the bandpass came out the best. I do prefer monopoles because of their ability to produce output well below thier tuning and they overlap better too. Ported enclosures do all kinds of things when overlaped because the phases of the ports and drivers are changing so fast.
I think that you can push X-max a lot farther with a bandpass for the obvious reason that its LP filtered AFTER the driver.
Pallas said:
My TV is ~50 inches wide. Even with the speakers tight to the sides, that is a distance 5 feet or more. Lobing will not be an issue.
Pallas said:
My point is that the centre is mainly for dialog. It doesn't need strong bass response.
I'm sure results are excellent from using three identical speakers for the front, but I don't think this is strictly necessary. For my own use, I went with a design that would excel in the vocal range. It uses a different driver ( 18mm coax) than my mains and the combination doesn't sound incoherently mushy at all.
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