SY said:
But the dispersion of the array is directly derivable form the driver's dispersion. The narrowing of dispersion /decrease in wavelength as frequency goes up is exactly what cause the comb filtering. As the wavelength becomes comparable to the width of the driver, tha driver acts more and more like a point source.
dave
slinco said:
He uses $3400 worth of 3 1/2" VIFA drivers ($68 each). He gives driver specs, but, it seems, nowhere in the some 10 page article does he actually tell you what model. I can make out something like TG3FSD10-?? off the picture.
From Al Wooley's trial of one of the little VIFAs, IIRC there were 2 possible VIFAs that could fill this roll, and VIFA calls them midranges (making them harder to find). I did get a chance to hear a set in the little K+T TL with the filter they recommended. Smooth sounding, if a little congested & very low efficiency.
dave
amt said:
Yes, very interesting question indeed - Roger is certainly a very clever engineer who has been working with EQ'd drivers for over 30yrs, and precise details of how this is achieved in the commerical product would understandably be considered a proprietary matter.
Perhaps there's a combination of "10dB acoustic gain" due to the proximity of the drivers, customized T/S driver parameters, and roll-off above the baffle step frequency of the array at play.
It would also be interesting to see the impedance characteristics of the combined array - while the rated sensitivity of 92.5dB would suggest compatability with even low powered tubed amps, there could be some issues with VC reactance for the more sensitive SE types.
The drivers used by Russell in his July 2006 Audioexpress article and in the IDS25 commercial array appear to be from the discontinued Vifa TG line--either the TG9FD10-08 or the shielded version which is TG9FSD10-08. Data sheets are at:
http://www.tymphany.com/datasheet/pdf/vf/TG9FD-10-08.pdf
and
http://www.tymphany.com/datasheet/pdf/vf/TG9FSD10-08.pdf
These are not really full range drivers--note the rapid response off axis in the 10-20 kHz range.
I wouldn't recommend these drivers used full range.
In his 2005 Audioexpxress article Russell uses the Parts Express buyout driver #269-469 (long since sold out) which was the 69 cent special that was available 3-4 years ago. This driver is a decent Pioneer made TV speaker but hardly a star in its full range driver capability.
Jim
http://www.tymphany.com/datasheet/pdf/vf/TG9FD-10-08.pdf
and
http://www.tymphany.com/datasheet/pdf/vf/TG9FSD10-08.pdf
These are not really full range drivers--note the rapid response off axis in the 10-20 kHz range.
I wouldn't recommend these drivers used full range.
In his 2005 Audioexpxress article Russell uses the Parts Express buyout driver #269-469 (long since sold out) which was the 69 cent special that was available 3-4 years ago. This driver is a decent Pioneer made TV speaker but hardly a star in its full range driver capability.
Jim
You got it. I'm interested in how the combing changes with constant center-to-center, but increasing driver diameter. I'm very uncomfortable with the idea that c-t-c is sufficient to determine combing.
rdf's suggestion of doing an FEA calculation occured to me, but that's actual work (and I don't have FEA software). It seems to me that this could be modeled in a one dimensional case and solved directly. If I had a couple hours...
rdf's suggestion of doing an FEA calculation occured to me, but that's actual work (and I don't have FEA software). It seems to me that this could be modeled in a one dimensional case and solved directly. If I had a couple hours...
On full range line array design:
1. Ask yourself whether you would like to be listening to a speaker which has a decent sized woofer vs. a heavily EQ'ed 3.5" driver to produce the low frequencies?
2. Now ask yourself if you wish to hear your highs from that same EQ'ed 3.5" driver vs. a good quality planar or ribbon?
My point do not assume that the Russell design is the ultimate speaker by any means.
If one wants a serious line array, consider the following unit at half the price of the Roger Russell IDS25 arrays:
http://www.selahaudio.com/id89.html
With the Selah Audio arrays you could have the arrays then add a pair of serious stereo subwoofers and a DEQX PDC-2.6 DSP Calibration Processsor and still have change to spare vs. the IDS25 arrays. So configurated the Selah Audio arrays would seriously kick the back sides of any other array on the market regardless of price.
Jim
1. Ask yourself whether you would like to be listening to a speaker which has a decent sized woofer vs. a heavily EQ'ed 3.5" driver to produce the low frequencies?
2. Now ask yourself if you wish to hear your highs from that same EQ'ed 3.5" driver vs. a good quality planar or ribbon?
My point do not assume that the Russell design is the ultimate speaker by any means.
If one wants a serious line array, consider the following unit at half the price of the Roger Russell IDS25 arrays:
http://www.selahaudio.com/id89.html
With the Selah Audio arrays you could have the arrays then add a pair of serious stereo subwoofers and a DEQX PDC-2.6 DSP Calibration Processsor and still have change to spare vs. the IDS25 arrays. So configurated the Selah Audio arrays would seriously kick the back sides of any other array on the market regardless of price.
Jim
What would stop someone from taking the cones off of all of the nsbs in an array, and mounting the magnets back to back and having one single long driver cone that is connected to all of the drivers at the same time? How would that behave any differently than the row of square drivers all lined up with zero space between the flanges?
Chrisb no call....
in fact I am with you on this one. I don't see any big problem with Roger's pricing though, 5-6 times actual cost is about the norm in marketing these kind of products so there is no surprise there. You just need to decide who's product you want to support and decide if the speaker makes you happy and fits your budget. I agree that the same kind of results (or even better) could be achieved for less especially for the diy builder. It will be interesting to hear the results of Roger's presentation at Denver this fall. I would love to go as it is a wonderful drive from Calgary but I don't see that happening this fall. Best regards Moray James.
in fact I am with you on this one. I don't see any big problem with Roger's pricing though, 5-6 times actual cost is about the norm in marketing these kind of products so there is no surprise there. You just need to decide who's product you want to support and decide if the speaker makes you happy and fits your budget. I agree that the same kind of results (or even better) could be achieved for less especially for the diy builder. It will be interesting to hear the results of Roger's presentation at Denver this fall. I would love to go as it is a wonderful drive from Calgary but I don't see that happening this fall. Best regards Moray James.
Consider that the Selah Array has 16 low distortion Seas Excel W18 woofers at $160 each and 16 Fountek ribbon tweeters at $126 each for a total driver cost of $4576. The finished speakers are priced at $8150 per pair (assumes upgraded crossovers) assembled in furniture quality cabinets. That makes the IDS 25 at $16500+ for a pair of arrays with a custom equalizer and $3400 in drivers seem way over priced.
As built, the Selah arrays will significantly out perform the IDS25 in every way.
Like I said you can add a state of the art $3750 DEQX which could EQ time, phase, and amplitude at 4096 points across the band plus provide room corrections to boot. Then you could add a couple of $2000 subs and still be cheaper than Russell's IDS25.
I can assure you that the Selah array has more inherent design engineering than the Russell array.
Jim Griffin said:
And i can assure you that Chris' tongue was firmly in his cheek when he made that comment.
My earlier comment about pricing was ade when i was unaware of the coercial assembled product.
That & the Selah are an illutration why diy (and close to diy) is booming & the traditional high-end is suffering.
dave
While we've got this line array thread going, I'd love to hear from Jim or someone else who's lived with a large LA speaker system about placement issues. Their unique dispersion pattern is what makes me wonder. I'd be using them in a living room situation and because of their large size I'd need to have them no more than three feet from the front wall (to the baffle). Two feet would be even better. Could I get away with this with a large array like the Alexandrite?
That's actualy one of the things that attracted me to Russell's array - they are very slim columns, and he even mentions (if I remember correctly) being able to place them nearly against the wall.
That's actualy one of the things that attracted me to Russell's array - they are very slim columns, and he even mentions (if I remember correctly) being able to place them nearly against the wall.
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