Variac said:
not a bad suggestion... and also something I've considered... I noticed those some time ago
the only hold up is their very very low efficency...
My ideal dream would be to go with PHL 8's for the midrange solution... but I can not afford them so I have to go with their low power audio cousin the PR17....
though I might be scaling this back to basic TMWW or MMTWW or something... so the PHL is a possiblity...
but sry the CSS looks great and I'm sure it sounds awesome... but too inefficent
I don't get the efficiency thing. I agree that when considering a speaker with one mid/bass driver I would be pretty unlikely to go with them for exactly that reason. I believe that they are about 87 db efficient at one watt one meter. Now people argue exactly how much efficiency goes up when you double the number of drivers, but I think everyone pretty much agrees that doubling the number of drivers adds 3 dB efficiency. So 2 drivers 90 dB, 4 drivers 93 db 8 drivers 96 db 16 drivers 99 db for one watt input.
If you are using 8 amp channels per side at say 40 watts/amp channel Thats 320 watts or say you get an amp with 300 watts/ch
Now doubling the power adds 3 dB: 2 watts 102 dB 4= 105dB 8=108dB, 16=111 dB 32=114dB, 64watts= 117dB, 128watts=120dB That's half power, That is very very loud!!! Deafening in fact!
However I have heard great things about the Phl's. If you use 2 Phl's they are about as efficient as the line source of CSS drivers I believe. So it comes out about the same. The Phls would be cheaper but no longer a line source.
32 drivers is a lot of money- over $1500 I'd guess. So I can see why that might be a reason to reconsider. 4 Phls is over $500 though.
If you are using 8 amp channels per side at say 40 watts/amp channel Thats 320 watts or say you get an amp with 300 watts/ch
Now doubling the power adds 3 dB: 2 watts 102 dB 4= 105dB 8=108dB, 16=111 dB 32=114dB, 64watts= 117dB, 128watts=120dB That's half power, That is very very loud!!! Deafening in fact!
However I have heard great things about the Phl's. If you use 2 Phl's they are about as efficient as the line source of CSS drivers I believe. So it comes out about the same. The Phls would be cheaper but no longer a line source.
32 drivers is a lot of money- over $1500 I'd guess. So I can see why that might be a reason to reconsider. 4 Phls is over $500 though.
Variac said:
This driver is great
Highest useable XO constrained by the WR125 centre-to-centre distance.
When i heard them there was 2 problems... 1st. The room was WAY to small to let them sing , and 2nd. the XO was still pretty much a prototype.
I'm sure we'll get another chance to listen to them (i wonder if Al will let us haul them outside) this Sat. Room will be the same size but the XO has had 6 months of development.
dave
I suppose there is also about a 3 dB loss for baffle step, but any wide range mid will require this I think. Also any equalizing of lower frequencies will lose some efficiency. However this is a benefit of the large excursion of the driver. More efficient drivers won't have as much excursion, so the can't be boosted in the lower range. Thes drivers have enough x-max to allow this- but it burns up power.
So Dave, what IS the max crossover to the tweeter if there is 5" center to center?
So Dave, what IS the max crossover to the tweeter if there is 5" center to center?
Variac said:
A question comprehansively answered in Jim Griffins's Line Source White Paper.... wavelength to wavelength/2 ... ~ 1.4-2.7 kHz (~1-2k for the PR17 -- time to look ar the Newform ribbons.)
dave
Jim Griffin's White Paper:
http://www.audiodiycentral.com/resource/pdf/nflawp.pdf
He seems to say less that one wavelength spacing, but references others that say 1/2 wavelength.
So I guess thats why you show a range. So the 125's could possibly go up to 2700, but that would excessive as the crossover is a slope rather than a precipitous cutoff I guess Seems like 2k would be about max.
I assume this would apply to MTM's also? Obviously most of them don't meet the 1/2 wavelength criteria, but some seem to work quite well.
Power shaping is also mentioned.
http://www.audiodiycentral.com/resource/pdf/nflawp.pdf
He seems to say less that one wavelength spacing, but references others that say 1/2 wavelength.
So I guess thats why you show a range. So the 125's could possibly go up to 2700, but that would excessive as the crossover is a slope rather than a precipitous cutoff I guess Seems like 2k would be about max.
I assume this would apply to MTM's also? Obviously most of them don't meet the 1/2 wavelength criteria, but some seem to work quite well.
Power shaping is also mentioned.
Variac said:
xover isn't really the problem.... 2k is good for the PHL or PR17
the ribbon should play flat to 1khz... (it's wide)
thy has both the PHL and PR17... he likes the PR17 more (in fact it's his favorite) only thing is the PHL has higher power handling...
I think the CSS is still a contender... so I'm thinking about doing the simple approach and ordering a PR17, PHL, and CSS to see which one I like...
I find that the center to center spacing issue is really beaten to death here on the forum, as if the effects need to be avoided like the plague. While I don't doubt the theory, the real world effects are small, just like horizontal lobing from line sources in our small rooms is a non-issue. At concerts the pro sound arrays are unlikely to have CTC spacing in their HF sections that are less than what we talk about using for our mids.
I believe 2 factors help mitigate the effects. First, the center of the cone is not the point source on any driver otherwise you couldn't use phase plugs. In the low frequencies the entire cone is the source because it is funtioning as a piston. Second, while at some point the sound source starts to be closer to the center of the cone, it also stops radiating into half space and starts to beam the high frequencies.
With an array, I believe the negative effects of comb filtering are minimal. For example 2 wide range drivers run full range sounds bad in the nearfield. The comb filtering effects are obvious. Yet if you stack 5 of them into an array they don't sound bad. I believe this is because the combing effects are averaged together. eg the center of driver #1 is 4" from driver #2, but it is 8" from #3 and so on.
As an example, my first array had 4" drivers with CTC spacing of 5" run full range with no tweeter. Their FR is reasonably flat from 150hz-10khz , sure some ripples but no objectionable spikes or nulls. The only noticeable difference in FR between the array and a single driver was a slight attentuation of the top end. Moving around both vertically and horizontally within the array plane even within 1m of the array didn't make any sonic difference unlike it does with only 2 drivers.
My suggestion to anyone building an array is to listen to it before choosing your crossover. If you are using wide range drivers, to me it is much more advantageous to have them cover as wide a range as possible than to plop a crossover point right in the middle of where our hearing is the most sensitive.
I believe 2 factors help mitigate the effects. First, the center of the cone is not the point source on any driver otherwise you couldn't use phase plugs. In the low frequencies the entire cone is the source because it is funtioning as a piston. Second, while at some point the sound source starts to be closer to the center of the cone, it also stops radiating into half space and starts to beam the high frequencies.
With an array, I believe the negative effects of comb filtering are minimal. For example 2 wide range drivers run full range sounds bad in the nearfield. The comb filtering effects are obvious. Yet if you stack 5 of them into an array they don't sound bad. I believe this is because the combing effects are averaged together. eg the center of driver #1 is 4" from driver #2, but it is 8" from #3 and so on.
As an example, my first array had 4" drivers with CTC spacing of 5" run full range with no tweeter. Their FR is reasonably flat from 150hz-10khz , sure some ripples but no objectionable spikes or nulls. The only noticeable difference in FR between the array and a single driver was a slight attentuation of the top end. Moving around both vertically and horizontally within the array plane even within 1m of the array didn't make any sonic difference unlike it does with only 2 drivers.
My suggestion to anyone building an array is to listen to it before choosing your crossover. If you are using wide range drivers, to me it is much more advantageous to have them cover as wide a range as possible than to plop a crossover point right in the middle of where our hearing is the most sensitive.
johninCR said:
luckily I have full xover selectiablity going active... but I do agree with you... Jim made that point many times... that even though a 7" driver line shouldn't be crossed at 2khz... it sounds the same to do so (if not better cause you're extending the playing range of the midranges)...
the thing that is really making me question the CSS is also that 1 PHL 3450 would be just as loud especially in the dedicated midrange area as 16 CSS's
I think what you really need to decide is whether you want an array or not. Achieving only 100db in room with reasonably efficient speakers is pretty easy. You really need to hear an array if you haven't already. It's a big sound with a big image and a much larger prime listening area because the effect of distance to listening position is so much less. Another advantage is one room mode is eliminated due to the lack of ceiling and floor reflections. The downside is more driver expense, a very tall speaker in your room, and holographic imaging can't equal the potential of a great point source speaker because you have sound sources that are different distances from your ears. The driver expense can be partially offset because less expensive drivers can be used to good effect, since each is handles a small portion of the workload they stay within a range of very low distortion.
I guess the question is whether you want a line source.
If you want the advantages and disadvantages of a line source then you are going to have the 16 drivers no matter what. So if they are efficient enough as a group then they will do the job.
I believe that there is a general situation that large excursion drivers have to be LESS efficient. Usually large excursion drivers have more distortion, but the CSS drivers claim that they fix this problem. DO they? I don't think we know for sure yet , but reports are that they are pretty good. But , I would think that you should only use the CSS if you are going to take advantage of their wide range. Generally around here there is a bias towards low excursion, efficient drivers, so I
When you say that the PHL 3450 would be just as loud in the midrange, you are saying "just as loud for a given input"
BUT, if the 16 drivers can take more power, then with a larger amp (or the string of chip amps which would have the advantages of smaller amps ) the 16 will be louder. Another factor is, as you say, that the extreme end drivers of the array are getting less signal, so are not "helping" the efficiency as much as I said.
If you go for the PHL midrange, then I guess you would use a much shorter and cheaper tweeter also? Might be a safer bet, considering that you are designing the ribbon from scratch. It might not work very well....
I guess the tweeter COULD be long still. There ARE speakers like this such as the Newforms.
If you want the advantages and disadvantages of a line source then you are going to have the 16 drivers no matter what. So if they are efficient enough as a group then they will do the job.
I believe that there is a general situation that large excursion drivers have to be LESS efficient. Usually large excursion drivers have more distortion, but the CSS drivers claim that they fix this problem. DO they? I don't think we know for sure yet , but reports are that they are pretty good. But , I would think that you should only use the CSS if you are going to take advantage of their wide range. Generally around here there is a bias towards low excursion, efficient drivers, so I
When you say that the PHL 3450 would be just as loud in the midrange, you are saying "just as loud for a given input"
BUT, if the 16 drivers can take more power, then with a larger amp (or the string of chip amps which would have the advantages of smaller amps ) the 16 will be louder. Another factor is, as you say, that the extreme end drivers of the array are getting less signal, so are not "helping" the efficiency as much as I said.
If you go for the PHL midrange, then I guess you would use a much shorter and cheaper tweeter also? Might be a safer bet, considering that you are designing the ribbon from scratch. It might not work very well....
I guess the tweeter COULD be long still. There ARE speakers like this such as the Newforms.
When it comes to loudspeaker design feel free to break the rules,
in the case of line source;
http://www.seventh-veil.com/
People like the sound.
No tweeters, no crossover. Simple.
in the case of line source;
http://www.seventh-veil.com/
People like the sound.
No tweeters, no crossover. Simple.
Those 7th veil speakers could only be called a line array in the broadest definition. With only a 1ft length of 4 2" drivers it would only behave as a line source in the extreme nearfield where I'd bet it sounds terrible. It's just 4 small drivers acting like a point source at normal listening distances. If you are going to go for an array you have to go all out and get as much line length as possible. Otherwise you'll end up with speakers that change tonality based on listening distance because you will be in the nearfield at some frequencies and farfield at others.
Variac said:
I have heard arrays and I do very much like them...
every design has it's shortcomings.... ESL's can't play well, Arrays may or may not have sub par near fields... etc
using PR17's or PHL 2520's like this
M T
M T <<< 32" long ribbon
M T
M T
W
W
or like this
M
M
T <<<<< 16" long ribbon
W
W
either one would yield nice sonics... the top one being more expensive but actually it probably would sound best...
a line of PHL's would be undoubtably superior to a line of those CSS's... 4 PHL's would have an efficency of 106 db and also a power handling of 1200 watts but that would jack up the price some (not enough to matter though)
the
M
M
T
W
W
Would be nice... 2 8" PHL's there would yield nice results and 103 db efficency and 600 watt power handling... so per watt the PHL's would sound both cleaner and louder than the CSS's (if what everyone says about the PHL's proves true, especially thy)
a 16" long ribbon would also give quite a nice "sweet spot" as far as that is concerned... though no where near the near infinite sweet spot of an array
I don't think 4 PHLs are a line source but might sound fine. If you aren't going to have a line source, then why not just have 2?
From the little I know, a 16" tall ribbon would certainly have a sweet spot. Like you couldn't move your head vertically at all.
The principal is that wide drivers have narrower dispersion -not wider.
So the tweet is wide vertically, so there is no vertical dispersion. Line sources get around this by having such a tall driver stack that you are always getting sound beamed directly at you.
I could be wrong, but this is my undrstanding.
From the little I know, a 16" tall ribbon would certainly have a sweet spot. Like you couldn't move your head vertically at all.
The principal is that wide drivers have narrower dispersion -not wider.
So the tweet is wide vertically, so there is no vertical dispersion. Line sources get around this by having such a tall driver stack that you are always getting sound beamed directly at you.
I could be wrong, but this is my undrstanding.
Variac said:
it would have roughly 20 degrees vertical dispersion... but it would be far better than a 6" ribbon as far as area covered by the sound
I know the 32" line wouldn't techinally qualify as a linesource but it would offer a large sweet spot enough that from any normal distance the sound would be the same standing up or sitting down
You're going to get yourself into no man's land with those partial arrays. You really need to read Dr Griffin's paper a few times if you want to use lots of drivers. A line length of 32" for a tweeter may be sufficient because shorter line lengths are OK for high frequencies and still retain line source characteristics at your listening position. If you want a line array that sounds great standing up and moving around too, then you need sufficient length so your ears are within the array plane standing up or sitting down. For the mids and woofers, a 32" line length will be totally inadequate because the lower the frequency the longer the line needs to be to act like a line source.
You're talking about spending a lot of money, so you should expect outstanding results. If you want to use a 32" ribbon, then I think you need at least a 60" line of mids and even longer line of woofers. You want your listening position to be in the nearfield operation of the line sources across the frequency spectrum.
You're talking about spending a lot of money, so you should expect outstanding results. If you want to use a 32" ribbon, then I think you need at least a 60" line of mids and even longer line of woofers. You want your listening position to be in the nearfield operation of the line sources across the frequency spectrum.
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