IDS25
Well guys, I actually went out and built a set of these!!! I adhered to the published design for the VIFA model and actually bought a MacIntosh EQ unit from Roger.
Firstly "comb filtering". Having previously built other line arrays I wasn't frightened of this. It may be there and measurable but to these 60 year old ears it doesnt seem to present a problem.
I must admit mine are not fully run in yet and I think the EQ may need to be tweaked for each individual room as no room correction is included in the design.
My initial listening has been underwhelming. If some one walked in and wanted them I'd be quite happy to part with them.
For mine the most ovbious feature is lack of low bass punch and SPL capability. I use up to 20db boost and have 140 tube watts. Maybe I need 200 SS watts???
The next obvious thing is lack of ultimate "air" on the top. But I dont have the top end EQ fully sorted yet.
The thing that worries me the most is the need for all the questiuonable quality EQ electronics in the signal path - perhaps this will destroy ultimate subtelty??
I peservere but I am not confident.
But get off "comb filtering"!!!
Cheers,
Well guys, I actually went out and built a set of these!!! I adhered to the published design for the VIFA model and actually bought a MacIntosh EQ unit from Roger.
Firstly "comb filtering". Having previously built other line arrays I wasn't frightened of this. It may be there and measurable but to these 60 year old ears it doesnt seem to present a problem.
I must admit mine are not fully run in yet and I think the EQ may need to be tweaked for each individual room as no room correction is included in the design.
My initial listening has been underwhelming. If some one walked in and wanted them I'd be quite happy to part with them.
For mine the most ovbious feature is lack of low bass punch and SPL capability. I use up to 20db boost and have 140 tube watts. Maybe I need 200 SS watts???
The next obvious thing is lack of ultimate "air" on the top. But I dont have the top end EQ fully sorted yet.
The thing that worries me the most is the need for all the questiuonable quality EQ electronics in the signal path - perhaps this will destroy ultimate subtelty??
I peservere but I am not confident.
But get off "comb filtering"!!!
Cheers,
But your description perfectly describes the consequences of severe comb-filtering at the top end. That's why we keep talking about it. Off-axis response is likely to have phase problems, but more importantly, you note a lack of 'air' which is caused by treble SPLs falling away due to the driver's response combing, despite heavy correction.
IDS-25
Scottmoose, I'm not sure you are correct. I have yet to fully implement the top end EQ and what I think I hear is related to the cone drivers' natural rolloff.
I hear little difference in response off axis.
Also, don't assume you can successfully experiment with 69c drivers. The qualities of the driver are what you hear!! Roger noticed a big improvement moving to the VIFA's from the previous cheaper ones he was using. In buying 50 of them I got 40% off retail.
Cheers
Scottmoose, I'm not sure you are correct. I have yet to fully implement the top end EQ and what I think I hear is related to the cone drivers' natural rolloff.
I hear little difference in response off axis.
Also, don't assume you can successfully experiment with 69c drivers. The qualities of the driver are what you hear!! Roger noticed a big improvement moving to the VIFA's from the previous cheaper ones he was using. In buying 50 of them I got 40% off retail.
Cheers
To hifryer:
It's not off the horizontal axis that you're seeing combing effects: they're readily apparent when you sit in the sweet spot.
Here's an exercise: get some graph paper, draw to scale a side view of the line array pointing at the listening position. Now, draw lines from each driver to the ear position and measure them. You'll find they will vary in length from a) the distance between listener and center speaker to b) a larger distance between listener and the top/bottom speakers.
These path length differences will produce cancellations at various frequencies. You can fix this by either sitting very far away so differences are minimal, or tapering the array.
Francois.
It's not off the horizontal axis that you're seeing combing effects: they're readily apparent when you sit in the sweet spot.
Here's an exercise: get some graph paper, draw to scale a side view of the line array pointing at the listening position. Now, draw lines from each driver to the ear position and measure them. You'll find they will vary in length from a) the distance between listener and center speaker to b) a larger distance between listener and the top/bottom speakers.
These path length differences will produce cancellations at various frequencies. You can fix this by either sitting very far away so differences are minimal, or tapering the array.
Francois.
And where things cancel & add changes with frequency... Paul Taylor's 1961 paper uses exactly his kind of graphical aid to explore the issues in line arrays.
http://p10hifi.net/planet10/TLS/downloads/taylor-line-array.pdf
Here is one of the more dramatic illustrations.
dave
http://p10hifi.net/planet10/TLS/downloads/taylor-line-array.pdf
Here is one of the more dramatic illustrations.
dave
DSP_Geek said:
Oh Boy, another line array thread!
Every time I post on this I get to hear what "a plenty dumb idea" I have. Well maybe it is, but the problem is that it works and, more importantly, sounds good as well.
The only way to get around comb filtering, other than a full length membrane is to just eliminate comb filtering at the listening position. How do I do this? Well in my profound ignorance, I just went ahead an constructed a Focused Array. I used (12) 1.5 inch drivers and the baffle is built to a 10.5 foot radius. I used my personal listening habits and room dimensions to calculate the amount of curvature. Sitting 8 feet away from the speaker with the radius focused at ear level you're going to have a 6-7 inch high envelope of sound. Not particularly pretty, practical or aesthetically endearing, it does produce a linear phase, absolutely cohearent wave front with no time smear, comb filter effects or other nasties. Ther are people that have heard them and the general concensus was that they sound very good. One "Doubting Thomas", Dr. David Hyre of Adire Audio, listened to them and discribed them as "the World's Biggest Headphones".
I'll just add that they were voted "Best Midrange" at one of Al Wooly's RAW Fest meets and was awarded the much coveted "Kowtow" Award at the last VSAC.
They have some fairly pronounced limitations, mainly the fact that you must stay within the "envelope" or the sound field collapses. However, if you do most of your listening alone and don't need party speakers this might work for you.
A picture of the speaker can be found at this URL, about half way down the page.
http://www.timn8er.com/pictures_from_nwwa_diy_audio_mee.htm
Best Regards,
TerryO
TerryO said:
Someone said that was a dumb idea? Hmmmmm. I guess Wilson and Focal are also dumb because they focus their drivers on the sweet spot.
Curving a baffle with an array of small drivers isn't how I'd do it, but it's a perfectly valid solution if, as you mentioned, you don't mind listening to very large headphones. Then again, the large Dunlavys are described in the same way, and nobody slams them as being "dumb".
By the way, a full length membrane still shows interference effects. It's not quite as obnoxious as the comb filtering produced by discrete drivers, but you still get a high frequency rolloff in the near field.
my line array
i know this thread has a little age on it, but, i will add this. i have built the roger russell line array with 20 3.5 inch drivers per cabinet and can say they sound fantastic. i only used 20 drivers to cut back on the series wiring issue. i will post a picture of the finished units. the overall character of the spearker is lifelike, deep, accurate and stunning. the voice and trumpet projection is like nothing else i have heard. building a set is not too difficult and i believe you will be quite satisfied. i had read all of the comb filtering, eq stuff and built them anyway.
i know this thread has a little age on it, but, i will add this. i have built the roger russell line array with 20 3.5 inch drivers per cabinet and can say they sound fantastic. i only used 20 drivers to cut back on the series wiring issue. i will post a picture of the finished units. the overall character of the spearker is lifelike, deep, accurate and stunning. the voice and trumpet projection is like nothing else i have heard. building a set is not too difficult and i believe you will be quite satisfied. i had read all of the comb filtering, eq stuff and built them anyway.
Attachments
have you ever thought about what these would sound like with a 60 watt chip amp mounted at each driver and all hooked to a nice active eq. no speaker cable transconductance issues or losses. full control and over 1000 watts reserve. that would be quite a project. think about it. by the way did the original ids25 have any porting or was it completely inclosed.
i had to take almost all of the batting out of the cabinets to get the sound right. in fact before i put the backs on i tested the wiring and the speakers sounded better to me opened up. i had thought of adding a directional cone at the back to deflect the sound from the rear. like using the entire column as the center piece for a huge long speaker. i am not super critical of my projects and do not take specs and graphs to heart. if it sounds good that is all i care about. also, these units do not like super rock music. they kind of get confused. vocals and jazz and piano are the best sounds reproduced to my ears on these columns. though i like pink floyd if it is loud. the whole project for both columns was less than 700.00 using magnesium/aluminum cones.
tryonziess said:
Yeah....
see this: http://pub48.bravenet.com/photocenter/album.php?usernum=4095425731&album=48032
Each speaker has 1 12 inch 15 mm Xmax woofer, 17 3 inch SAMMI wide ranges, and 30 Dayton Neo ND20A's. The crossover is electronic analog L/R 24 db at 165 and 2500. The tweeters have 60 w/ch, the mids have 150 w/ch, and the woofers have 350 w/ch.
There is no comb filter distortion in the mids and the tweeter combing starts above about 15Khz, above my audibility.
Each midrange is in its own 23.5 x 4 inch tube stuffed to 4lb cu foot with fiberglass, sealed.
Sound is out of this world or the most life like I've ever experienced. Sound stage is fantastic. Dynamic range is astounding. Distortion is simply non-existent.
Zarathu
zaranthu, is it not nice to build something and find out it works fantastic regardless of all the techno babble that it will sound bad. i like my line array. it sounds great to me and all those who listen to it. how do you like the way voice and trumpet music jumps out at you. it is unnerving at times. i also have a big 12 inch woofer hooked into my system x over at around 180. nice project.
line arrays
cant remember what specs i might have been refering to.
the only specs I have a all in Rogers 2 articles for Audio Xpress.
none are relevant or important to me.
I can only conclude that maybe I need to fiddle with stuffing and that for somepeople's bass expections and requirements the load should be shared with at least 1 12" sub.
cant remember what specs i might have been refering to.
the only specs I have a all in Rogers 2 articles for Audio Xpress.
none are relevant or important to me.
I can only conclude that maybe I need to fiddle with stuffing and that for somepeople's bass expections and requirements the load should be shared with at least 1 12" sub.
hifryer, as my line array stands with 20 drivers per side the bass is good. there is no boominess, or rattle. i only added the bass woofer to remove some of the stress from the small drivers. the 3.54 inch aluminum/magnesium cones have an xmax of 1 mm. this gives a very fast bass response but implies excess cone movement. by adding the woofer i hope i am extending the life of the array.
i would like to see the original article by roger russell. i do not have that issue of the magazine with the article in it.
i would like to see the original article by roger russell. i do not have that issue of the magazine with the article in it.
line array
tryonziess, send me an email and I will send one to you introducing you to Roger.
He may be happy to email you scanned copies of the articles.
I am not comfortable supplying direct as too many people want stuff without the committment to pay for mag subs etc. The material is also copyright.
cheers
Hifryer
tryonziess, send me an email and I will send one to you introducing you to Roger.
He may be happy to email you scanned copies of the articles.
I am not comfortable supplying direct as too many people want stuff without the committment to pay for mag subs etc. The material is also copyright.
cheers
Hifryer
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