Rob41
Don't stop believin'
I think I need to first disclose that this is my very first speaker build. I have modified prebuilt speakers before, but have never done a complete build from the ground up.
I have recently gone the way of using an active crossover/dsp using a Minidsp. This has opened up a whole world of possibilities to me allowing me to have abilities as a novice that would have been impossible 30 years ago.
I use vintage amps like those in my signature, I listen primarily to various styles of rock but desire a system capable of critical listening. While I tend to appreciate healthy, yet accurate bass, I generally listen at moderate levels.
Choosing a type of speaker
I wanted to try building a line array for some time but got a bit side tracked by the concept of an open baffle. Thanks a lot Poultrygeist! That's when I thought about combining the two types of speaker designs.
From the offset I hadn't really seen this before but after doing a bit more research I discovered although not particularly common, others have been down this road so O.B.L.A. it is.
One of the advantages that drew me to line array's was the fact that distortion is greatly reduced due to the sheer number of drivers and how little each of them is pushed.
My listening space is very live and untreated and line arrays lend themselves well to this kind of environment due to interacting less with the floor and ceiling.
The O.B. type of speaker interested me because it's free of the resonances associated with a typical enclosure and I've been told they interact well with ribbon or planar type drivers. I'll find out if I like the dipole effect of the mid-bass drivers, but if I don't I can always add treatments to the rear wall.
Which type of Line Array to choose
This is where a lot of research cam into play as well as reading many white papers on the topic. Let me just say, at this point, I feel very comfortable having an in depth conversation on the science behind Line Array's as long as the other person in the conversation is doing all of the talking.
For my room of 8' tall and approximately 20'x30', I decided a straight and essentially floor to ceiling array would suit my application best. There are other designs such as CBT where the array has a convex shape like the kit Parts Express sells. I've read some very excellent reviews of this design but all of the research I've done points me in a different direction. IMO, the CBT is akin to pro type line arrays where a vast area in an open environment needs to be covered, i.e. farfield listening environment. Perhaps it is also a good choice where the cost of the additional drivers to achieve a floor to ceiling array is too great. Lot's of enthusiasts and designers are very pleased with a CBT style array, it's just not the direction I want to take.
In the end, I decided to go with a straight, floor to ceiling array where the floor and ceiling reinforce the cylindrical wavefront.
Driver selection, layout and frequency coverage
Midranges:
I knew I wanted to build some line arrays so when Parts Express had some 6 1/2" mid/mid woofer buyouts with the specs I was looking for I got them, 48 of them.
http://www.parts-express.com/6-1-2-poly-cone-midbass-woofer-4-ohm--299-609
With a Qts of 0.95 they should work well in an open baffle arrangement and go as low as I need them to without putting up too much of a fight. I plan to cross them from 75Hz to 3300Hz if the combing of a 6 1/2" driver at these high of frequencies isn't too noticable. I'll have to see what happens on the bottom end as well since they have an Fs of 52Hz and should actually be crossed two octaves above the resonant frequency which would be 208Hz. I guess I'll find out about combing givin the size and high frequencies I want to use.
Tweeters:
I thought of keeping it budget minded but it seemed the choices I had that would work in a line array would either sound like the cheap tweeters they are or would be cost prohibitive. I ultimately decided to go with Dayton PT2C Planar tweeters. I've used these as substitutes in a couple pairs of speakers once I ditched the passive crossovers and used them with a MiniDSP active crossover.
http://www.parts-express.com/dayton-audio-pt2c-8-planar-tweeter--275-085
I like the way these planar tweeters have an effortless, airy quality to them and have been told when used in multiples i.e. an array, their qualities improve appreciably.
Augmented bass:
Eventually I would like to get dedicated subwoofers in a distributed bass set-up but for the time being I'm going to use a pair of Dayton PA drivers that I've come to appreciate.
http://www.parts-express.com/dayton-audio-pa380-8-15-pro-woofer--295-034
Although they have an Fs of 28.3Hz and modeling indicates significantly higher Hz, I have used them successfully below 20Hz with dsp while still allowing the necessary spl's. I've found the output to be very tight and clean for my taste. Unfortunately, their low Qts doesn't allow me to go O.B. for my woofers which will have to come later.
Final (preliminary) design:
I started out wanting to build a single array of mid/mid bass drivers with an outboard array of the planar tweeters. Fortunately the flaws of doing this were quickly pointed out to me so I settled on mounting all of the drivers in a single baffle.
Dave Smith, (former designer who has worked for JBL, KEF, Meridian, McIntosh, Snell and PSB etc.) suggested to me to go in a slightly different direction than I had originally planned. He pointed out to me that I would experience some serious lobing, but if I went with an MTM approach, the lobing would then be symmetrical which would be much better. Thank you Dave!
So my cast in stone.....or yet to evolve design will consist of a line of 9 Dayton Planar drivers flanked on each side by an array of 12 6 1/2" drivers on each of two baffles. O.B. line array MTM. I'm going to call tham OBLA-33 due to the number of drivers on each baffle.
Here is crude drawing of the basic layout:
[URL=http://s1223.photobucket.com/user/Rob41/media/O.B.L.A.%2033_1.png.html][/URL]
The material I'm using for the baffles are maple work surfaces measuring 1 1/2" thick x 2' x 8' long.
http://www.sears.com/craftsman-8%27-butcher-block-work-surface/p-00914965000P
I'll be giving my router and circle jig a workout for sure. Maybe the 132+ solder connections will be the most fun.
Once completed they will be approximately 20" wide by 7 1/2' tall. I will be tri-amping and using my MiniDSP to control most aspects of the driver behavior....I hope.
The fun will begin in ernest tomorrow when I put together some mock ups and I'll do my best to provide some measurements during testing. I only have REW but I am using a calibrated mic.
I'd just like to say, if not for the wealth of information fellow AKer's share here my project wouln't even be possible. Thank you! :thmbsp:
The pictures will begin flowing tomorrow. This is my first build thread so I apolagize as I'm sure there is a lot of information missing. I'll be happy to answer any questions if anyone is interested.
I have recently gone the way of using an active crossover/dsp using a Minidsp. This has opened up a whole world of possibilities to me allowing me to have abilities as a novice that would have been impossible 30 years ago.
I use vintage amps like those in my signature, I listen primarily to various styles of rock but desire a system capable of critical listening. While I tend to appreciate healthy, yet accurate bass, I generally listen at moderate levels.
Choosing a type of speaker
I wanted to try building a line array for some time but got a bit side tracked by the concept of an open baffle. Thanks a lot Poultrygeist! That's when I thought about combining the two types of speaker designs.
From the offset I hadn't really seen this before but after doing a bit more research I discovered although not particularly common, others have been down this road so O.B.L.A. it is.
One of the advantages that drew me to line array's was the fact that distortion is greatly reduced due to the sheer number of drivers and how little each of them is pushed.
My listening space is very live and untreated and line arrays lend themselves well to this kind of environment due to interacting less with the floor and ceiling.
The O.B. type of speaker interested me because it's free of the resonances associated with a typical enclosure and I've been told they interact well with ribbon or planar type drivers. I'll find out if I like the dipole effect of the mid-bass drivers, but if I don't I can always add treatments to the rear wall.
Which type of Line Array to choose
This is where a lot of research cam into play as well as reading many white papers on the topic. Let me just say, at this point, I feel very comfortable having an in depth conversation on the science behind Line Array's as long as the other person in the conversation is doing all of the talking.
For my room of 8' tall and approximately 20'x30', I decided a straight and essentially floor to ceiling array would suit my application best. There are other designs such as CBT where the array has a convex shape like the kit Parts Express sells. I've read some very excellent reviews of this design but all of the research I've done points me in a different direction. IMO, the CBT is akin to pro type line arrays where a vast area in an open environment needs to be covered, i.e. farfield listening environment. Perhaps it is also a good choice where the cost of the additional drivers to achieve a floor to ceiling array is too great. Lot's of enthusiasts and designers are very pleased with a CBT style array, it's just not the direction I want to take.
In the end, I decided to go with a straight, floor to ceiling array where the floor and ceiling reinforce the cylindrical wavefront.
Driver selection, layout and frequency coverage
Midranges:
I knew I wanted to build some line arrays so when Parts Express had some 6 1/2" mid/mid woofer buyouts with the specs I was looking for I got them, 48 of them.
http://www.parts-express.com/6-1-2-poly-cone-midbass-woofer-4-ohm--299-609
With a Qts of 0.95 they should work well in an open baffle arrangement and go as low as I need them to without putting up too much of a fight. I plan to cross them from 75Hz to 3300Hz if the combing of a 6 1/2" driver at these high of frequencies isn't too noticable. I'll have to see what happens on the bottom end as well since they have an Fs of 52Hz and should actually be crossed two octaves above the resonant frequency which would be 208Hz. I guess I'll find out about combing givin the size and high frequencies I want to use.
Tweeters:
I thought of keeping it budget minded but it seemed the choices I had that would work in a line array would either sound like the cheap tweeters they are or would be cost prohibitive. I ultimately decided to go with Dayton PT2C Planar tweeters. I've used these as substitutes in a couple pairs of speakers once I ditched the passive crossovers and used them with a MiniDSP active crossover.
http://www.parts-express.com/dayton-audio-pt2c-8-planar-tweeter--275-085
I like the way these planar tweeters have an effortless, airy quality to them and have been told when used in multiples i.e. an array, their qualities improve appreciably.
Augmented bass:
Eventually I would like to get dedicated subwoofers in a distributed bass set-up but for the time being I'm going to use a pair of Dayton PA drivers that I've come to appreciate.
http://www.parts-express.com/dayton-audio-pa380-8-15-pro-woofer--295-034
Although they have an Fs of 28.3Hz and modeling indicates significantly higher Hz, I have used them successfully below 20Hz with dsp while still allowing the necessary spl's. I've found the output to be very tight and clean for my taste. Unfortunately, their low Qts doesn't allow me to go O.B. for my woofers which will have to come later.
Final (preliminary) design:
I started out wanting to build a single array of mid/mid bass drivers with an outboard array of the planar tweeters. Fortunately the flaws of doing this were quickly pointed out to me so I settled on mounting all of the drivers in a single baffle.
Dave Smith, (former designer who has worked for JBL, KEF, Meridian, McIntosh, Snell and PSB etc.) suggested to me to go in a slightly different direction than I had originally planned. He pointed out to me that I would experience some serious lobing, but if I went with an MTM approach, the lobing would then be symmetrical which would be much better. Thank you Dave!
So my cast in stone.....or yet to evolve design will consist of a line of 9 Dayton Planar drivers flanked on each side by an array of 12 6 1/2" drivers on each of two baffles. O.B. line array MTM. I'm going to call tham OBLA-33 due to the number of drivers on each baffle.
Here is crude drawing of the basic layout:
[URL=http://s1223.photobucket.com/user/Rob41/media/O.B.L.A.%2033_1.png.html][/URL]
The material I'm using for the baffles are maple work surfaces measuring 1 1/2" thick x 2' x 8' long.
http://www.sears.com/craftsman-8%27-butcher-block-work-surface/p-00914965000P
I'll be giving my router and circle jig a workout for sure. Maybe the 132+ solder connections will be the most fun.
Once completed they will be approximately 20" wide by 7 1/2' tall. I will be tri-amping and using my MiniDSP to control most aspects of the driver behavior....I hope.
The fun will begin in ernest tomorrow when I put together some mock ups and I'll do my best to provide some measurements during testing. I only have REW but I am using a calibrated mic.
I'd just like to say, if not for the wealth of information fellow AKer's share here my project wouln't even be possible. Thank you! :thmbsp:
The pictures will begin flowing tomorrow. This is my first build thread so I apolagize as I'm sure there is a lot of information missing. I'll be happy to answer any questions if anyone is interested.
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