Buyout Vifas for line array?

[D, Rose]

Hey guys. How would the Vifa TC9FD-05-16 3.5 inch full range drivers do in a line array? I was thinking about building them to fit in the front left and right corners of my church. Have about 24 per side. At 6 bucks a piece, even I could afford these!

[AMC]

Sensitivity is fairly low, and that's a 1 watt rating in a 16 ohm speaker (not 2.83v) . Even with 24, could be a stretch depending on how large a space it is. Power handling is low, but with 24 it would come up to 240 watts a side, seems acceptable to me. And then there is the matter of wither they will go low enough to cross to something larger (fs = 115hz), and the fact that they include a cap to X-over at 200Hz suggests something. Perhaps 100Hz in doable with 3rd order. That being said, I bet they would do a great job of vocals. Question would be, for $288, is there something better? How would the $16.00 Dayton Audio PA165-8 6" PA Driver work? your could put 9 per side at the same cost, and I bet they would work better, have good sensitivity, and would drop to that 100Hz mark.

[Sydney]

If the idea was to run 24 per side w a 3 5/16" driver spacing w/o shading:
That would be a 2M line and could be wired to 6 ohms.
Without tweeters: The driver spacing limits HF coherence to below 4Khz.
The nearest audience member should be no nearer than 50'

[bbtk]

I've thought along similar lines and bought 4 of the Vifa's for testing when they were a little more expensive.

I have 3 of them wired in parallel for a 6 ohm load and in a cardboard test box in front of my computer. The 3 of them are together are about as loud (by ear) as a single JVC 3X5 speaker that was on closeout at PE. I bought the JVC's in the classified sections, after already purchasing the Vifa's and considering how much work there would be making roughly 3 times the number of holes of Vifa's than for the JVC's for about the same sensitivity.

My former church used 4 of the Bose L1 line arrays and I thought they sounded pretty good for vocals and moderate volumes -- though I normally think of Bose as very overpriced and mediocre. Vocals and acoustic guitar sound very good through the Bose, better than many PA speakers I've heard at churches -- but I still think the L1's are way overpriced.

On the plus side, I some research on line arrays and former McIntosh designer Roger Russell is supposed to make some very good line arrays for home use. His speakers are supposed to use Vifa full rangers as well, see below for a link. So I think the Vifa's on closeout have potential. But no matter what, you'll need separate woofers to produce the midbass for a PA, let alone the deep bass.

http://www.ids25.com/
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-1064

[AMC]

former McIntosh designer Roger Russell is supposed to make some very good line arrays for home use.


sort of makes me wonder what he did about the comb filtering, as his seem to be 4 or 5inch drivers. He says there is NO crossovers...

[Sydney]

From http://www.roger-russell.com/equalizers/equalizers.htm
"The IDS-25 system is also equalized and the curve is unique to complement the specific drivers used in the system...The wide-range drivers are all connected in series parallel...the equalizer smooths response and extends both low and high ends of the spectrum...The system is based on my patents and earlier work with equalizers and column systems"

Roger Russell has written numerous articles in AudioAmateur mag. and his systems and EQ are not simple - reflected by $18K+ price.

[Jmillerdoc]

I think you would do better with some of the buyout Aurasound drivers over at www.madisound.com for a line array....

[Jmillerdoc]

https://www.madisound.com/store/manuals/ns525-255-8a.pdf
These are 5.25 and run $3.60 each. They have two others there ranging from $2.50 - $4.50 with very similar TS to the Vifas you're looking at.
Just food for thought. I have played around with several of the NRT small drivers from Madisound and they are quite good.

[AMC]

From http://www.roger-russell.com/equalizers/equalizers.htm
"The IDS-25 system is also equalized and the curve is unique to complement the specific drivers used in the system...The wide-range drivers are all connected in series parallel...the equalizer smooths response and extends both low and high ends of the spectrum...The system is based on my patents and earlier work with equalizers and column systems"

Roger Russell has written numerous articles in AudioAmateur mag. and his systems and EQ are not simple - reflected by $18K+ price.

I understand the concept, first used in the Bose 901 for the same reasons, but I don't see how that would help with the comb filtering. And considering what a quality DSP unit costs, it hardly would justify that kind of price.

[Taterworks]

How would the $16.00 Dayton Audio PA165-8 6" PA Driver work? your could put 9 per side at the same cost, and I bet they would work better, have good sensitivity, and would drop to that 100Hz mark.

The 6" drivers would not be a good solution unless separate smaller HF drivers are used. The 6" drivers by themselves will have center-to-center spacing that is too great to function as a line array in the upper midrange and treble.

I'm not sure why people are naysaying the 3" drivers, when that seems to be the preferred solution among pro audio manufacturers who are actually manufacturing line arrays. To fill in the midbass range, either run stereo subwoofers with a high crossover point (200 Hz or so) or provide midbass modules with something like four beefy 6" woofers, like these: Goldwood heavy-duty 6" (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-306)

In a midbass module, a couple of these (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-100) would be an even better solution.

[wg_ski]

I'm not sure why people are naysaying the 3" drivers, when that seems to be the preferred solution among pro audio manufacturers who are actually manufacturing line arrays.


Even the big ones with 12" woofers will have a couple of 3" (or four) per element (plus a tweeter). The one in the JBL pro units might even be 2".....



In a midbass module, a couple of these (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-100) would be an even better solution.

For 60Hz-up bass, four of those might be preferred to a single fifteen. And if you really wanted to get crazy, that particular 8" would work very well as the bottom end of a 3-way line array.

[Sydney]

Not naysaying, just acknowledging the compromises: driver size/spacing sets the HF limit and directivity, displacement limits of drivers.
There is not a lot of internal detail on the IDS-25s array, only very simple FAQ and sales oriented type.
I suspect that while no crossovers are used: that the internal series/parallel wiring could be similar to concepts employed in Bessel arrays to perform amplitude shading ( Keele's paper details numerous passive wiring schemes that include resistors. )


I don't see how that would help with the comb filtering. If however the drivers are treated uniformly: then I'm of the same opinion.
Smaller transducers raise the HF limit, but not to upper limit of audibility ( w/o tweeters ), and require large numbers be used for excursion and power handling requirements; and can create wiring challenges or require high impedance drivers or an autotransformer be used to maintain an amp friendly stable load.
In general in professional arrays ( as used in Rock concerts ) use larger drivers than lines for smaller areas.
The "throw" is greater and SPL is higher. One example is a Versarray which uses a 12" w (2) horn loaded ribbons per array segment.
However larger segments have different coverage limitations and these limits are frequency dependent.
http://www.qscaudio.com/support/education/designing_line_arrays/index.php?b=part1&p=2

[AMC]

The 6" drivers would not be a good solution unless separate smaller HF drivers are used. The 6" drivers by themselves will have center-to-center spacing that is too great to function as a line array in the upper midrange and treble.

Of course you would need a HF driver, but I think you would need that with the 3" drivers as well. As pointed out by someone else, the "combing" will come in fairly low.


I'm not sure why people are naysaying the 3" drivers, when that seems to be the preferred solution among pro audio manufacturers who are actually manufacturing line arrays. To fill in the midbass range, either run stereo subwoofers with a high crossover point (200 Hz or so) or provide midbass modules with something like four beefy 6" woofers, like these: Goldwood heavy-duty 6" (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-306)

In a midbass module, a couple of these (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-100) would be an even better solution.

I don't have a problem with 3" drivers, I'm just not sure this is the best choice, or perhaps even a good choice of a 3 incher, for the reasons stated above.

Those series II woofers might work in this situation, were we already have very low efficiency drivers, but that 90db SPL is going to limit the real pro duty application.

There is a reason line arrays are not a commonly used system short of large venues.

[Sydney]

There is a reason line arrays are not a commonly used system short of large venues. There are dozens of line array manufacturers and most of them reference the same near/field far field graphs that Ureda details in his AES line array papers.
It shows how line arrays are intended to trade wide dispersion for controlled directivity over distance.
Historically Unshaded arrays where originally used for speech reinforcement only at large distance. Human speech does not require extended HF, so the HF limit placed by large drivers was not a concern, until music reproduction with HF content is desired.

[Taterworks]

For a speech-range line array (and limited music), the 3" drivers would have plenty of top end. They can probably even be run without a contouring filter (though they will still need a HPF and maybe a pair of small subs). In pro sound, if your design can reach up to 16-18kHz, you can call it a day, because propagation losses really kill extended HF energy in the far field (we don't notice that problem with our hi-fi setups because most hi-fi listening is done in the mid to near field, and most dynamic live sound mics also begin to roll off in the highs.) If you're listening from a distance that is further away than the room's critical distance, the HF rolloff becomes more severe.

I think we may be thinking about two completely different product categories. The multi-box line arrays used in pro audio have a lot of non-ideal behavior that goes on with them, to the extent that the decay rate is closer to 4 or 5 dB per doubling of distance than the claimed 6 dB, and their throw characteristics are really related more to the pattern control that's going on, and coming into the pattern of more boxes as you move further away from the array. I'm thinking of the compact line-array columns (Bose MA12, Community Entasys, and others) that use smaller drivers spaced closer together in a single chassis. To achieve line array behavior, your sources must have a maximum spacing of 1/4th the wavelength of the highest frequency they will reproduce.

[AMC]

In pro sound, if your design can reach up to 16-18kHz, you can call it a day,

Couldn't agree more. I would challenge anyone to hear a difference between a prosound system that rolled off at 15K vs 20K. If you did, you would probably like the 15K better. for some reason (sales literature) we have the 20K number stuck in our head, A: there is just not that much up there, and B: most of us over the age of 12 can't hear much in that register anyway.


I think we may be thinking about two completely different product categories.
you hit it AGAIN! In this case the OP was clear on his intentions. And for a speech only system, it might just work, but I and still a bit concerned over their efficiency.

[Sydney]

...To achieve line array behavior, your sources must have a maximum spacing of 1/4th the wavelength of the highest frequency they will reproduce.
Indeed - The 1/4 wavelength relationship is fundamental to mutual coupling: The HF coherency is limited by inter-driver spacing, and the bandwidth of low frequency drivers is reduced as the line gets longer - again due to same spatial relationship.
Before vocal columns were called line arrays; they were used extensively by the bands of the 60's. The tall column form was easy to haul and when restricted to vocal only - were adequate. Unfortunately placed on the floor ( instead of flown ) they suffered from the interactions of the boundary reflections, in addition to frequency dependent dispersion.
A common variation/upgrade of a simple column was a center or top mounted Horn HF to overcome the driver spacing issue.
( FWIW I'd plan on adding a HF section to regain the tops octaves if HF content is to be reproduced. )

[ewetho]

I have 4" woofed 6 driver lines on a 4.5" spacing and 9 - 3/8"tweets on 2.5" spacing crossed at 4K. They are simply spectacular. Comb filtering, not an issue. Simply one of the most articulate setups I have ever heard.

Based on that design I make a 6 woof 12 tweet line for PA use with 6" woofs and the same tweets also crossed at 4K. These sound identical to my 3 lines based on 4" speakers but just increased volume. The also suffer no comb filtering issues and have been VERY WELL received for dances and other uses in a PA.

Lines are very cool.

Actually working on a modular array now too. One cab is done and is very nice and will be working on second one to demo at least a pair.

[Sydney]

There is a misunderstanding about constructive and destructive interference and combing

"While combing has traditionally been considered undesirable, line arrays use combing to work: without combing, there would be no directivity."
from the section How Do Line Arrays Work?
http://www.meyersound.com/products/mseries/m3d/line_array_theory.htm

[billfitzmaurice]

There is a misunderstanding about constructive and destructive interference and combing

There's also a major misunderstanding about combing versus lobed response. Combing is a shifting of the frequency of response peaks and valleys as one moves horizontally across the soundfield. It does not occur with vertically aligned sources, irrespective of spacing. Spacing does affect lobed response, but lobing doesn't change the response as one moves across the soundfield. Most of the references I've seen in this thread with respect to combing actually refer to lobing.

[Sydney]

Combing is a shifting of the frequency of response peaks and valleys as one moves horizontally across the soundfield. It does not occur with vertically aligned sources, There is no treatise on Acoustics or Physics that support this.
No demonstration of pattern interference draws a distinction in a x,y,z. context.
Human ears being oriented on a horizontal axis are much more sensitive to aspects of sound in the horizontal plane - a practical arrangement.
That does not mean constructive and destructive interference is plane specific.

[billfitzmaurice]

There is no treatise on Acoustics or Physics that support this.
No demonstration of pattern interference draws a distinction in a x,y,z. context.
Human ears being oriented on a horizontal axis are much more sensitive to aspects of sound in the horizontal plane - a practical arrangement.
That does not mean constructive and destructive interference is plane specific.
http://www.jblpro.com/pub/technote/tn_v1n07.pdf
Admittedly being dated 1984 makes this a johnny come lately, as Olson et al quantified all of this four decades earlier. But the JBL artwork is much easier to understand than Olson's hand drawn plots.
Sorry, that I didn't clarify that combing only occurs on the horizontal plane if the listeners position shifts on the horizontal plane. That being the case there is no combing from a vertical source with respect to the listener, and it's only with respect to the listener that matters. If the listening position is on a moving elevator that's a different can of worms entirely. And yes, both constructive and destructive interference are very much plane specific. Were that not the case line sources wouldn't work the way that they do.

[Sydney]

yes, both constructive and destructive interference are very much plane specific. Were that not the case line sources wouldn't work the way that they do. Of course the pattern of constructive and destructive interference is along the line of sources. If the line was floating in space and rotated: the pattern also rotates. A pair of microphones rotated or a pair of ears rotated along the center of the source will record/perceive the difference based upon their orientation.
If a reflective boundary were rotated around a line source it would also create interference.
If one were to measure ( a typical TLA or SLA for example ) at various points in space and at increasing distance the patterns would convey the relationship that a single on-axis SPL chart ( at unspecified fixed distance ) does not.
Bob McCarthy does an outstanding job of distilling integral calculus to Euclidean Geometry to show how the spatial relationship of sources ( real or reflected ) produces the pattern of summation and cancellation that can be calculated mathematically.
His use of a phase wheel shows angularly: the repeating peaks and nulls that are euphemistically called combing.
Yesterday I heard examples of the interference from a variety of points in 3 dimensional space: A Band on a stage with a curved quarter sphere shell behind them.
Call it combing but it's the patterns created from source interference.