Line array with coaxial drivers

[tryonziess]

Here is a picture of the ones I made some years ago.

 

[graaf]

post your line array graaf

I haven't built any yet. In another thread I have posted a picture of the cabinets of the loudpeakers I now use

But I am tempted to build an array therefore I am looking for information and I ask questions 🙂
I am a follower of an old maxim of cabinet-builders: "think thrice, measure twice, cut once" 😀

especially as I am not tempted by typical two- or three-way array of 8-16 ohm
I am interested in building a one-way and a high impedance array
plenty of information available WRT the former, no information WRT the latter

therefore I ask questions 🙂
I hope You don't mind? 🙂

best,
graaf

 

[graaf]

another side

VERY nice 🙂

can You answer my questions?

best,
graaf

 

[adason]

Does the amplifier "see" those 160 ohm or rather only 40 ohm or so? I don't know

amplifier see particular impedance for particular frequency

if the speakers impedance changes with fr response, which it does, the output changes

for instange increasing impedance of woofer due to increasing inductance of the coil (which can be compensated for by zobel)

if the impedance for particular speaker dips to 1 ohm for some frequency, than 20 drivers in series will present as 20 ohms, but only at this frequency, which will most likely sound louder than rest of response

however, if speaker is quoted 8 ohms, its impedance should stay at or above 8 ohms

for both extremes of the fr response its impedance actualy might be tens of ohms...hence the lower output

if for low frequencies driver presents 20 ohms, than 20 drivers in series will present 400 ohms

you have to either trust the manufactures impedance curve or measure it for yourself, which is quite easy

it may play a big role in high impedance line array...but not my problem

 

[graaf]

you have to either trust the manufactures impedance curve or measure it for yourself, which is quite easy

how can I measure this "dynamical impedance" with a square wave? what do I need?

it may play a big role in high impedance line array...but not my problem

not mine either 🙂
it is rather one of the many problems of quality of sound reproduction at home 🙂

I am very interested in those problems

best,
graaf

 

[graaf]

ps.

amplifier see particular impedance for particular frequency

but with musical signal an amplifier sees many frequencies at the same time?
that "dynamical impedance" measurement seems to take it into consideration

 

[graaf]

Here is a picture of the ones I made some years ago.

this is exactly what I am thinking of! 😀

thanks for posting! 🙂

can You do something for me please? 🙂

can You tell me what are those drivers? can You post any measurements of them and of the whole array?
can You try positioning them against opposite walls (like Beveridge)?
and my last request - can You wire them in series and see what happens? 🙂

best,
graaf

 

[adason]

but with musical signal an amplifier sees many frequencies at the same time?

sure, musical signal is composed of many frequencies
each instrument has fundamental and upper and lower harmonics
any waveform can be decomposed to series of sine waves by fourier transform
this compex signal is amplified by an amplifier (lets assume perfect amplifier) which will amplify all the frequencies equaly
this musical signal than drives the voice coil, which presents changing impedance for each frequency hence the acoustical power for each frequency will be changing and the resulting fr response will not be flat
which is not good
one of the most important criteria in loudspeaker design is flat fr response
there are many ways to equalize fr response as flattest as possible...crossoved design, cabinet design, L-pads, driver modification, active equalization...you name it

 

[tryonziess]

Graaf

The 40 drivers in my line array's are Tang/Band 315d with aluminum/magnesium cones. The full specs are on the Parts Express website or Tang Band site. I am by no means a guru in this area, however when researching the drivers I looked at a few things I do know. One of course was price -- which Parts Express will adjust depending on quantity purchased. I also wanted a decent cone excursion which I think is about 3.5mm. There response curve is adequate and rather flat. They also are sold as full range drivers. I hope that is helpful.

On another note I have noticed that the entire Tang/Band line has increased dramatically in price. Maybe they are better speakers than I originally thought -- hence the price increase. Go figure!!!

If I had it to do over I would offset space the drivers side to side at about 45 degree angle to help out with combing --- which I do not notice. i usually run them bi-amped with the bass cutoff around 350-400 give or take a few. They will handle the full lowend and sound O.K. I just do not want to push it.

To all a good Memorial day weekend -- A U.S. thing -- Tad

 

[xlr8]

I read Dr. Griffin's white paper on line arrays this morning and have come to some conclusions:

1. I definately will try this build

2. I will give full range a shot before adding any type of tweeter.

3. I will use the 3" peerless drivers I mentioned earlier in this thread.

4. I will try power tapering

5. I will be asking you guys LOTS of questions 🙂

I do have a question about power tapering. I calculated a load of 3.87 ohm using 20 8ohm drivers and tapering from 2 to 3 to 5 drivers on top, then 2 to 3 to 5 drivers on the bottom. My question is: Will jumping from 3 to 5 drivers instead of 3 to 4 have a detrimental effect on the overall sound, or am I just being paranoid? If I understand this correctly, I should taper from ear level to the floor and then ear level the the ceiling...correct?

 

[norman bates]

I've read of people still having a barry white type of sound even in a bessel wiring arangement.

I go beserk with the "tall sound" from a line of tweeters, full rangers, or even tall planar......................

I vote for a focused array.............

assuming you don't want room filling sound and don't mind a sweet spot an exact distance from the speaker.................


"Here's a thread about one of our meets, my focused arrays are at #12."
http://av123forum.com/showthread.php?s=&threadid=10817
by terryO from audioasylum.com post

 

[graaf]

I've read of people still having a barry white type of sound even in a bessel wiring arangement.

I go beserk with the "tall sound" from a line of tweeters, full rangers, or even tall planar......................

>Tryonziess

Have You noticed "barry white type of sound" with Your array?
And what about "tall sound"? What is it?

best,
graaf

 

[norman bates]

nope, I don't have one, heard a few though....................

art array I believe, line of ribbons, line of 6's I think...........
owner in iowa mentioned trying powertapering to remove "barry white syndrome". Better than non tapered but lost driver clarity due to lack of all of them driven at the same time.

http://www.diyaudio.com/forums/showthread/t-49316.html
johninCR
"I'd suggest going with some power tapering of the array to avoid some larger than life audio images that can happen with arrays. For example deep male voices (Barry White or James Earl Jones) can sound like their head is 4ft accross using a normally wired array."

"Power tapering is where you send more power to the center drivers and less to the ends. With a normally wired arrays you can hear the drivers at the top and bottom of the array along with the rest, but they are delayed slightly in time because they are farther from your ears. This results in a "stretched" audio image. By essentially turning the volume down on the drivers at the end of the array, you get better imaging with giving up the benefits of a line array. You do it using a special series/parallel wiring configuration."

http://www.diyaudio.com/forums/showthread/t-39464.html
mazeroth
"Took (2) 2x6s that are 8 feet long and mounted 12 of the $0.69 cent Pioneer drivers from Parts Express between them. Ran them 3 in series and then the 4 series in parallel to get a 6 ohm load for the woofers. Hooked up (6) of the closeout Onkyo $0.48 tweeters, 2 in series then the 3 series parallel to achieve a 2.66 ohm load to the tweeters............The sound is HUGE!...............Listening to rock I am overwhelmed by the sound, but the quality can't touch my Polk LSis. When listening to my fiancee's Norah Jones the sound was just awesome. Less stress on the speakers compared to rock made them sound a lot better."

http://www.audiocircle.com/circles/index.php?topic=45051.msg404008
JohninCR
"With all that I have heard, I could clearly pick out sound coming from the topmost and bottommost drivers, with the result only being problematic with some recordings. The image distortion it caused was most prevalent with deeper male vocals. eg Barry White sounded like his head was at least a meter in diameter. Even so I still highly recommend arrays."

johnincr (cost rica) did the flat line array then curved it and seemingly never went back.

I saw a post by linkwitz talking on speakers at a show. I latched onto what he wrote because it identifies so strongly what i hear.

http://www.linkwitzlab.com/design_of_loudspeakers.htm
"What interested me most was the sound presentation of these nearly floor to ceiling speakers. Their sound is big and close up. Like watching Patricia Barber's lips move on a large movie screen. It's very impressive in its detail, if that is what you like. As an illusion of the real thing it did not pull me in. It seems to me these types of speakers will be at their best in very large venues when listened to from some distance. Conversely, I liked the Pipedreams best when I sat really close and heard only to a section of the tall line, as if they were giant headphones, but then a much smaller speaker could do the same. My conclusion is that uniform line source speakers are not what I would pursue for accurate sound reproduction in typical size domestic rooms. Tall speakers would be best configured with drivers in symmetrical W-M-T-M-W layout, which approximates a source of more constant acoustic size."

Norman

 

[Scottmoose]

As noted above, a line array (sans power-tapering) will basically sound the same irrespective of listening height. Because they lack any real vertical dispersion (within the fresnel zone at any rate) they therefore cannot generate an especially accurate illusion of height to the soundstage. The 'big headphones' analogy mentioned is quite a popular one, as it's a pretty accurate assessment of the kind of sound arrays of this type provide.

 

[graaf]

Because they lack any real vertical dispersion (within the fresnel zone at any rate) they therefore cannot generate an especially accurate illusion of height to the soundstage.

You mean that the "point source" speakers can generate illusion of height because of their vertical dispersion?
How is this illusion generated?
And how does the ear perceive height in general? What are the spatial cues for the perception of height of the sound source, of its vertical position?
In the case of "point source speakers" are the spatial cues in the recording being reproduced faithfully by the speakers? Or is the perceived height totally artificial and simply created by positioning of the loudspeakers at a certain height?

best,
graaf

 

[graaf]

I saw a post by linkwitz talking on speakers at a show. I latched onto what he wrote because it identifies so strongly what i hear.

http://www.linkwitzlab.com/design_of_loudspeakers.htm
"What interested me most was the sound presentation of these nearly floor to ceiling speakers. Their sound is big and close up. Like watching Patricia Barber's lips move on a large movie screen. It's very impressive in its detail, if that is what you like. As an illusion of the real thing it did not pull me in. It seems to me these types of speakers will be at their best in very large venues when listened to from some distance. Conversely, I liked the Pipedreams best when I sat really close and heard only to a section of the tall line, as if they were giant headphones, but then a much smaller speaker could do the same. My conclusion is that uniform line source speakers are not what I would pursue for accurate sound reproduction in typical size domestic rooms. Tall speakers would be best configured with drivers in symmetrical W-M-T-M-W layout, which approximates a source of more constant acoustic size."

acoustic size of a sound source?
what is the hearing mechanism for perception of acoustic size of a sound source?
what is the mechanism of this alleged deformation of acoustic size of a sound source by a tall line source in general and specifically by a line array?
Is this "image deformation" something reported by all listenerers or just by some of them?

best,
graaf

 

[norman bates]

"acoustic size of a sound source?
what is the hearing mechanism for perception of acoustic size of a sound source?"

ever hear someone playing an acoustic guitar ?
ever hear it played back on some 6' tall panel speakers?
Now play it back on a full range flat array with eq.
(eq doesn't really help phase problems, but it can help a microphone measure flatter).
To me the image size really is off compared the real thing.
There it gets tricky.
A concert recording would be something entirely different.
I've read reviews of small full rangers and refering to the sound as if all of it is coming from a circle the size of a flashlight.
Does it bother everyone ?
nope
It does me, it does some others.
Line arrays should have less floor/ceiling reflections, sound similar 3' off the ground and 6' off the ground, and have wide dispersion.
Combine that with many drivers so each driver is doing hardly the work it was when it was by himself.
Arrays can make dynamics.
But a bunch of cheap drivers sound like a better driver.
Not an incredibly better driver, but cleaner.


Will image hieght bother you ?
I doubt it.
Most love the "big top" sound from arrays.
Not my cup of tea.
To me the verticle row of tweeters just isn't right.
The brain smooshes it all together.
I know better and this is an area I am extra sensitive to.
Others are more sensitive to freq balance, distortion, etc.

People like the midrange of the large tannoys.
The are not time aligned, just concentric source.
The jbl urei 8111, 813a, those are time aligned coaxes.
http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/UREI-811A.pdf

People like a poorly implemented coax.
Perhaps it is due to a similar wavelaunch as a person's head.
Or even the concentric souce.
Or similar radiation patterns at crossover point.

Makes me want to build a demonstrator to show at local audio show, focused array vs flat with eq array.

Norman
Norman

 

[rjbond3rd]

...How is this illusion generated? ...are the spatial cues in the recording being reproduced faithfully by the speakers? Or is the perceived height totally artificial...

I like the single driver approach because it is the reverse of a microphone. A microphone is just a diaphram that moves in response to sound pressure, and if you do all that backwards, you get a single-driver speaker (simplistically speaking).

But is it faithful, or artificial? Faithful to what? If you made a recording with just a stereo mike, then yes, the speakers could be faithful to that. But how often does that happen? It's usually a dozen or more mikes pumped through all sorts of outboard gear (noise gates, compression, EQ) mixed down to stereo -- is that what the audience heard? I don't think so.

And what part of that recording is the hall's ambience? How could you really reproduce the original hall's ambience when you're listening in a room with its own ambience?

Still, that's the quest. It's 100% artificial but within all that, some things are accurate, some things are pleasing, some things are explained by physics, and some things remain a mystery.

 

[graaf]

But is it faithful, or artificial? Faithful to what?

I am saying "faithful" in a minimal sense of "not distorting what is encoded in the recording"

And what part of that recording is the hall's ambience? How could you really reproduce the original hall's ambience when you're listening in a room with its own ambience?

in this case the answer is quite easy, here You have an explanation: http://www.moultonlabs.com/more/nick_batzdorf_interview/

I think You should really try speaker positioning I recommend after Beveridge

It's 100% artificial but within all that, some things are accurate, some things are pleasing, some things are explained by physics, and some things remain a mystery.

and some are "explained" by numerous audiophile myths 😉

and what about accurate? what is it? isn't it the same as not distorting what is in the recording?

best,
graaf

 

[Scottmoose]

You mean that the "point source" speakers can generate illusion of height because of their vertical dispersion?
How is this illusion generated?
And how does the ear perceive height in general? What are the spatial cues for the perception of height of the sound source, of its vertical position?
In the case of "point source speakers" are the spatial cues in the recording being reproduced faithfully by the speakers? Or is the perceived height totally artificial and simply created by positioning of the loudspeakers at a certain height?

Correct. Best illustrated by a diagram, so I've attached one below. It shows the ~cylindrical wavefront a line-source will present within the fresnel zone, and the equivalent point-source. Note that the former is effectively devoid of vertical dispersion, compared to the latter.

Generating an impression of height in a stereo soundstage is not entirely a phantom; it can be helped by clever mixing & engineering etc. Depends on the recording, mic. placement & the quantity of direct to reflected information contained in the recording. Removing vertical dispersion thus reduces the accuracy of the soundstage in this plane.

Of course, arrays do sound very impressive because of their sheer scale, although whether or not the latter is actually an accurate representation of the soundstage is far more questionable. Horizontal imaging is superb. The rest? YMMV. I find them a bit superficial.