Concrete DIY Line Arrays and Subs

[bigjacko]

No but.......the original line array with the ribbons was with MDF cabinets from Newform Research. I wanted a semi elipse x-section, concrete is very easy to shape with a mold And dead quite for resonance. The concrete is post tensioned with 7 rods that run their length keeping the entire structure in permanent compression so they will never crack. The front outer baffle is 6061 aluminum 1/2” thick. They weigh 660 lb each and have very bad WAF but are perfect for my man cave. I cross the ribbons at 1K with a 1st order and the mid/bass at 1200 with 2nd order all passive. The plan is to get another amp and go all digital but I have not been overly excited to try this mainly because of the requirements to go to a multi channel DAC.......frankly, they sound so darn good that you question sanity on spending more money to try and make them questionably “better”. Then again as my member name suggests I am “afflicted”. Cheers

Forgot to mention last time, have you tried bendy ply for mold like this? Cutting that much mdf is time consuming and expensive. How did you do the post tension? You use nuts to squash from the top and bottom? One picture shows nuts sticking out of concrete, did you put another metal plate on that? The reason to go all digital for me is I don't have to design crossover, get deep filters and timing drivers. In your case if you only got tweeter and woofer, it is not hard and expensive to get higher order filters. You said your ribbon can crossover at 1k, that is very low for a ribbon, maybe because they are huge!! You can try higher order filters to get better using range for both woofer and tweeter, I think it is worth it for this project. Did you use power taper (this term?) for this line array?

 

[Afflicted]

Forgot to mention last time, have you tried bendy ply for mold like this? Cutting that much mdf is time consuming and expensive. How did you do the post tension? You use nuts to squash from the top and bottom? One picture shows nuts sticking out of concrete, did you put another metal plate on that? The reason to go all digital for me is I don't have to design crossover, get deep filters and timing drivers. In your case if you only got tweeter and woofer, it is not hard and expensive to get higher order filters. You said your ribbon can crossover at 1k, that is very low for a ribbon, maybe because they are huge!! You can try higher order filters to get better using range for both woofer and tweeter, I think it is worth it for this project. Did you use power taper (this term?) for this line array?

The mold pieces were made using 2” thick styrofoam, it took about 40 outer shape and 40 inner shape moods cut on a scroll saw. Hopefully it’s more apparent in these photos

 

[Afflicted]

The mold pieces were made using 2” thick styrofoam, it took about 40 outer shape and 40 inner shape moods cut on a scroll saw. Hopefully it’s more apparent in these photos

The top plate is steel ( see attached photo) note vertical pipes with rubber washers where the pipes butt up against the steel top plate. As mentioned previously there are 1/2” threaded rods inside the pipes which run all the way down and are threaded into the 1/2” thick steel support base. The top plate has a large fill hole in the center and smaller holes around the periphery to allow insertion of a vibrator when filling the mold

 

[Afflicted]

Forgot to mention last time, have you tried bendy ply for mold like this? Cutting that much mdf is time consuming and expensive. How did you do the post tension? You use nuts to squash from the top and bottom? One picture shows nuts sticking out of concrete, did you put another metal plate on that? The reason to go all digital for me is I don't have to design crossover, get deep filters and timing drivers. In your case if you only got tweeter and woofer, it is not hard and expensive to get higher order filters. You said your ribbon can crossover at 1k, that is very low for a ribbon, maybe because they are huge!! You can try higher order filters to get better using range for both woofer and tweeter, I think it is worth it for this project. Did you use power taper (this term?) for this line array?

Yes, I do want to pursue the digital filter realm but I have to wait a year before I start spending more money and sneaking more audio equipment into the house......my better half does not appreciate an audiohaulic “relentless pursuit” of perfection and learning. I did not use “power tapering” which by that I think you mean vertical attenuation from the centerline up and down......not that smart (yet). The 1K was recommended by the ribbon designer and manufacturer as was the 1st order.....I agree some playing and perfecting with digital XO and timing would be a great pursuit but pricy as I am powered with Bryston and use a Matrix Element X DAC. I have been eyeing the Okto Research dac8 PRO

 

[Vini darko]

Proper stuff. Reinforced concrete subs and speakers is the best kind of audio madness.

 

[Harmonie]

there are 1/2” sch 80 pipe running full length with 1/2” threaded rod inside fo both reinforcement but most importantly post tensioning ....as described in previous comment above

Coming back on the metal rods, are these epoxy coated ?
Or not afraid of rusting ?
Ever considered carbon rods, or better, aramid rods in particular Technora® ? (pre-tensioned)

 

[bigjacko]

Yes, I do want to pursue the digital filter realm but I have to wait a year before I start spending more money and sneaking more audio equipment into the house......my better half does not appreciate an audiohaulic “relentless pursuit” of perfection and learning. I did not use “power tapering” which by that I think you mean vertical attenuation from the centerline up and down......not that smart (yet). The 1K was recommended by the ribbon designer and manufacturer as was the 1st order.....I agree some playing and perfecting with digital XO and timing would be a great pursuit but pricy as I am powered with Bryston and use a Matrix Element X DAC. I have been eyeing the Okto Research dac8 PRO

Yes power tapering is the one you mentioned, you can do it by arranging the drivers some prallel some in series to get the power tapering effect. Hypex DSP plate amps can do active crossover and are pretty cheap, but the fans spin when they are too hot. You got a lot of gear shown in the photo, they look so expensive. If you don't mind the price there are better measuring stuff, although no one can hear the difference haha. Remember to use protecting capacitor for the ribbon if you want to go active crossover.

 

[Afflicted]

Yes power tapering is the one you mentioned, you can do it by arranging the drivers some prallel some in series to get the power tapering effect. Hypex DSP plate amps can do active crossover and are pretty cheap, but the fans spin when they are too hot. You got a lot of gear shown in the photo, they look so expensive. If you don't mind the price there are better measuring stuff, although no one can hear the difference haha. Remember to use protecting capacitor for the ribbon if you want to go active crossover.

Yes, mostly bought used but good gear - Torus power supply, Bryston 1000w mono’s, esoteric pre and matrix element x dac, to name a few

 

[Afflicted]

Yes, mostly bought used but good gear - Torus power supply, Bryston 1000w mono’s, esoteric pre and matrix element x dac, to name a few

Also the subs are run by 2000w to each voice coil (8000watt) total with a Chinese SPS AMP. The Peerless drivers in the subs (sealed) like lots of power but sound incredible

 

[egellings]

You need a crane to install those!

 

[Afflicted]

You need a crane to install those!

Yes actually I did. They came in through the basement window horizontally on rails. A hydraulic scissor table then lowered them to the floor.

 

[RealityCheck18]

Thank you so much for posting this!

If you felt a few thumps, that was me throwing you under the bus. Back 8 years ago, I got bit by the array bug so built my arrays much to the horror of my wife. No worries, they will be garage speakers--and my wife made sure they were. Basically, I made them 6 feet 2 inches tall, a foot wide and around 10 inches deep with 12 five inch woofers, 20 three inch "full ranges" for mids and 48 ten millimeter tweeters crossing my mess over at 350 Hz and 5.5 KHz. Built a pair of dual 15" push-pull slot loaded subs 20 inches tall to place those coffins. Total height was 7 feet 10 inches (239cm tall) so it would fit in the living room when I convinced my wife they look great and was positive I could win her over with my amazing stud abilities. Alas, this was not so as she caught me one weekend with them in the living room.

My subs only weigh 175 pounds each and each array cabinet is only 100 pounds. Heck, I'm a light weight with a total system weight of only 550 pounds! That is less than ONE of your speakers! It did take me three revisions and 16 months to get them to sound right--had to go with a three way because those 10mm dome tweeters needed to be crossed over at 5.5KHz. A few bands of EQ later, I get around 27Hz to 16 KHz reasonably flat out in the garage. Can't get too anal about it, smooth cement floors, metal everywhere and that big metal door at the other end eliminated any audio records being set. At least those piles of drivers do give a very step vertical dispersion and when stacked on subs, no floor/ceiling bounce until past my listening position.

Since they are garage speakers, plenty of people have seen them and they always make comments--along the lines of "insanity" or "arena sound in a garage?" or "compensating for something?". Most people remark how they have a "big sound" and I installed one of my subwoofer drivers wrong. Glad I built them, line arrays are odd ducks but make great party speakers and work well in poor acoustic environments like garages.

Soooooo, you going to ship one to ASR for measurements? I ponder how the measuring gear would deal with attempting line array measurements, if it needed to measure each driver it might take awhile.

If you get around to measuring your coffins---err, arrays--it would be cool to see how it all plays out.

 

[Afflicted]

Thank you so much for posting this!

If you felt a few thumps, that was me throwing you under the bus. Back 8 years ago, I got bit by the array bug so built my arrays much to the horror of my wife. No worries, they will be garage speakers--and my wife made sure they were. Basically, I made them 6 feet 2 inches tall, a foot wide and around 10 inches deep with 12 five inch woofers, 20 three inch "full ranges" for mids and 48 ten millimeter tweeters crossing my mess over at 350 Hz and 5.5 KHz. Built a pair of dual 15" push-pull slot loaded subs 20 inches tall to place those coffins. Total height was 7 feet 10 inches (239cm tall) so it would fit in the living room when I convinced my wife they look great and was positive I could win her over with my amazing stud abilities. Alas, this was not so as she caught me one weekend with them in the living room.

My subs only weigh 175 pounds each and each array cabinet is only 100 pounds. Heck, I'm a light weight with a total system weight of only 550 pounds! That is less than ONE of your speakers! It did take me three revisions and 16 months to get them to sound right--had to go with a three way because those 10mm dome tweeters needed to be crossed over at 5.5KHz. A few bands of EQ later, I get around 27Hz to 16 KHz reasonably flat out in the garage. Can't get too anal about it, smooth cement floors, metal everywhere and that big metal door at the other end eliminated any audio records being set. At least those piles of drivers do give a very step vertical dispersion and when stacked on subs, no floor/ceiling bounce until past my listening position.

Since they are garage speakers, plenty of people have seen them and they always make comments--along the lines of "insanity" or "arena sound in a garage?" or "compensating for something?". Most people remark how they have a "big sound" and I installed one of my subwoofer drivers wrong. Glad I built them, line arrays are odd ducks but make great party speakers and work well in poor acoustic environments like garages.

Soooooo, you going to ship one to ASR for measurements? I ponder how the measuring gear would deal with attempting line array measurements, if it needed to measure each driver it might take awhile.

If you get around to measuring your coffins---err, arrays--it would be cool to see how it all plays out.

Oh my, the trials and tribulations of a DIY speaker builder, wonderful story. I do plan to measure them so stay tuned.........