I need help with building a 7.1 system!

Discussion in 'Speakers' started by Langotriel, Feb 18, 2014.

  1. Langotriel

    Langotriel Extra

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    Right... i have been given a huge task. I need to design a 7.1 system for a small private cinema for the budget of about $10000. I will be making the speakers out of MDF because i can get that for free. I already have an idea about how i am going to design the speakers but i need help with parts.SO, here is the plan.all the speaker points (7 places) will have 2 sets of speakers. 1 bottom set point to the middle of the bottom row and one pointing to the top row. This means that the top row will usually be a little further away from the centre and pointing more in towards the middle (if that makes sense). I will try to do a diagram below :P0............|SCREEN|............./0/..|O|..........|SCREEN|..........|O|____|O|__FLOOR_________The front speakers will be laid out like that for example.. with the top speakers being a little further out and pointing at more of an angle towards the centre so that it hits the middle of the top row.I plan to have 2 midwoofers, 2 high mids and 2 tweeters per speaker point except maybe the centre speaker at the front. So i need to know about what parts go well together and will fill the room with sound (which will have sound dampening all over btw). I also need to know how to put them together... The box design i get, but i have never used crossovers or make Active speakers before. My experience is limited to subwoofers for cars.The room size is about 23 deep x 29.5 wide x 10 tall in Feet. It will have about 30 seats on 3 rows. The rows will start at 8 feet from the front wall and go to about 14.5 feet from the front wall meaning that there is about 8.5 feet of space for the rear speakers. From the sides there is less space... There will be about 2 feet each side maybe for the L/R back speakers.The screen size is about 85 inches (i think) so with that all in mind, anyone got any suggestions? any tips or tutorials on how to make crossovers and make active speakers properly?All the sound equipment has to cost no more than about $10000 (including receiver, amp or whatever else i need)HELP
     
  2. Dougofthenorth

    Dougofthenorth Stunt Coordinator

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    RE: "all the speaker points (7 places) will have 2 sets of speakers."

    1) What AVR (or components) are going to drive the 2 separate sets of speakers in each position?
    - you may need a special control unit to allow settings for the extra sets
    - Equalizing that setup would be a logistical challenge for sure.
    Essentially you are not bi-amping, but bi-speakering ;)

    2) You would have to use speakers that mate with the ohm output of the AVR 4,8,16 or whatever
    - Since you are making the speakers you could use that draw 1/2 the ohms per channel of the AVR
    - The AVR will have to double up on the watts per channel also speakers you could use that draw 1/2 the watts .
    - Driving 2 sets of 8 ohm speakers with an 8 ohms per channel AVR will set it's own issues.
    - You might solve your issue by getting an AVR with 2 or 4 presence/effect channels & not need to double up on speakers.
    Yamaha for one, makes several solutions. 9.1 or .2 , 11.1 or .2

    3) That MDF had better be very high density (almost all glue :D ) to make decent speaker enclosures.
    - Then there is the construction methods that must be employed (mitred corners, internal baffles etc etc etc )
    - I would go & audition various speaker brands that you like, spec the cabinets, see if you can get similar drivers/tweeters &
    duplicate the enclosures accordingly
    - There should be a shop somewhere that makes/repairs/sells speaker/cabinet supplies - including grill cloth, crossovers etc

    I would first handle the AVR speaker driving & equalizing first - before building anything!
     
  3. schan1269

    schan1269 HTF Expert
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    I'm trying to figure out why you think you need to aim speakers at different parts of the room. Unless you are building narrow angle horns. Most tweeters will accommodate a 30° dispersion...meaning, doubling is nowhere near necessary.To top it off, you could purchase drivers intended for horizontal mounting like Ohm Walsh and Mirage do. And like BIC used to do with the TPR Sound Span.
     
  4. Langotriel

    Langotriel Extra

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    You are right when you say equalizing could be a problem. The thing is i want there to be good sound for the people sitting and the front as well as back.. there will be several feet between their heads is distance and the people at the back will be elevated slightly so i figured 2 sets of speakers directed at 2 points would solve that problem. the MDF will work fine.. the inside will be covered with fibreglass resin to make it hard and smooth. I simply don't have the budget to buy huge amounts of plywood other than what we are already buying for soundproofing/dampening. The room itself will have plywood walls that are covered in sound dampening material and felt and then there will be a nice carpet on the floor.tell me more about these presence/effect channel receivers. How can they help me?
    Like i said above, there will be 3 rows of seats so people at the back will be higher and several feet back compared to the front.. pointing speakers at the middle front and middle back would give them equal sound hopefully.. but there might be problems with that .. @anyoneDoes anyone know of parts that go well together? like tweeters and woofers that just match well and that don't break the bank?
     
  5. Robert_J

    Robert_J Lead Actor

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    Pick a proven design or buy a kit. Without the experience or the testing equipment, designing a crossover almost impossible. Going active just adds additional complexity to your system. I suggest a kit from They provide the drivers, crossover parts and even the front baffle. You build the other 5 sides of the box.

    Being that they are wave guides, the sensitivity it much more than other speakers so you may not need 2 per location. Here's a great write up on the least expensive model http://www.diysoundgroup.com/forum/index.php?topic=53.0

    As far as the subs go, how much space are you willing to give up? How deep do you want these to play?
    MDF is medium density hence the name. HDF is complete overkill for a speaker. I use MDF. Egglestonworks uses MDF in speakers they sell for $100k.

    Butt joints are completely acceptable. Bracing depends on the size of the speaker/sub.

    You can duplicate and enclosure and drivers but if you don't have the crossover then your speaker will probably sound like crap.

    Parts Express has been the go to company for me since the early 1990's. My current front 3 were sourced completely from PE. http://www.parts-express.com/project-gallery-speaker-project-the-d-iii
     
  6. Robert_J

    Robert_J Lead Actor

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    That's a waste of fiberglass and time.
     
  7. Langotriel

    Langotriel Extra

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    I want to be able to pick drivers.. getting crossover kits or ready made ones is fine by me... i just need to know what i need. The plan is to have 4 different speaker types.. low mid, high mid and highs.. and then the sub takes care of the rest. I am willing to not have 2 speakers for each point if single speakers will achieve good results.. i was just a little unsure about it. For the sub, space is no real issue. The box just has to be carried through a door so if it fits through a door (regardless of length) it's all good. I want it to be able to hit 20-25 hz really.. dual 15'' maybe with a box tuned to 25hz ?? Subwoofers are something i have made before so i know how to build them well enough.Also.. I used dollars because people know that better but i am located in the UK so parts express might not be an option. I just need to know what i am looking for. I have used SB acoustics drivers before and i like them.. they make this: SB Acoustics Satori MW16P-8 MidwooferIt looks pretty decent.. decent numbers and charts and the price is right if I go with single speakers for each point. What else would i need to go with something like that?
    How so? if the box is ported the sound will flow better.. sound waves are physical.. with less friction inside the box it will come out without trouble.. it is a cheap little extra thing that is a small step to better sound that i can't really mess up :P.
     
  8. Robert_J

    Robert_J Lead Actor

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    You can't do that. It's all part of a system. You enclosure is dependent on the drivers you choose. The crossover is dependent on the drivers you choose and the enclosure they are installed in. You can't work backwards. If you choose the drivers, you have to design your own enclosure and design your own crossover. The software and testing equipment would eat up about half of your budget.
    That's a large room. If you want to reach reference levels, then look into something like this - http://www.billfitzmaurice.com/THT.html
    That's why there is a location field in your profile. It allows us to tailor our responses to you.
    discussed this a few years ago. Check out that thread and the links in it to other sites. There may be a published design that you could use. That does look like a great driver but for less than the price of the driver, you can buy an entire kit in the link I gave.
    So we are getting into fluid dynamics of air? In the main volume of the box, there are just sound waves bouncing around. In the port, if you are using something like PVC pipe, it is already smooth. If you use a slot port made out of MDF, then it is also smooth. If you compare the friction between the two you could only tell a difference if you had some type of measuring equipment available to NASA. In the sub building world if you get within 10% of the computer model then you are OK. You can't tell the difference with your ears. So I will say it again, that is a waste of time, money and product.
     
  9. Langotriel

    Langotriel Extra

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    Well it is valuable experience.. What about hiring the equipment? Or hell, there must be some guidelines that will help me just wing it? I can build enclosures for drivers based on numbers.. why can't numbers be used for crossovers?
    Well yeah the room is pretty big. 23 deep x 29.5 wide x 10 tall in Feet as said earlier in the thread.
    What thread? .. I can get a kit for less but when i have a bit of cash to spend i might as well spend it.. It is a sizeable room and I want quality as good as i can get for my budget. Diminishing returns and all that, i know.. but it is valuable experience that can be used for myself at a later date.
    fine. It would also help seal the boxes though.. and that is important, especially for subs... Speaking of which.. what is the best way to seal enclosures ?
     
  10. schan1269

    schan1269 HTF Expert
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    I think Robert "erased" a line of his post(or the link didn't port over).When I build subs, I just use screws and glue. Never heard of fiberglass inside either. But, if you stuff it...isn't the effect of the fiberglass a moot point?.If this room is that big, I'd do infinite baffle or transmission line. Using my phone, so adding links is not going to happen, but...There is an easy to find web-page of a guy's twin transmission line subwoofers using 2 10" each...the TL is 12" piece of sewer pipe, 6 feet each(bought 13', cut it in two).So yeah, two boxes built to contain two 10", with a 12" 6 foot long pipe...I should add...I haven't built many subs. I've built 3 making, essentially, a perfectly square box to hold a driver. I have nodded many subs where their original bits died...Biggest changeover being a JBL DPS-12. The craptitude of the DPS amps is legendary. Bought it dead...Have since bought a Krell mono-block to run the Infinity driver that now resides in the original box. So...no design on my part...on this one.
     
  11. Dougofthenorth

    Dougofthenorth Stunt Coordinator

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  12. schan1269

    schan1269 HTF Expert
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    Adding to Doug...I'm a big proponent of Presence*/IIz/DSX/Neo X.I run a 9.1 with height in my main theatre(Onkyo NR1008) and 7.1 with width in my living room(NR 807).My living room is 40x40(never measured, but it is the same size as the garage below that holds a Subaru Forester, F250 extended cab long bed and an AH Sprite...sideways in front of the Subaru...with enough room for snow blower, power washer and generator...and you aren't stumbling around...anyway, big room).The Onkyo 807 with a pair of DCM TF 600, TF350, SurroundScape and a pair of KX6(look all those up...doubt any of it were ever sold outside the US/Canada) has no problems with filling the entire room.*Yamaha started this ages ago with Presence. And they, so far, are the only ones with rear Presence. There is a forum member doing it with a 3020(Or 3030???).Properly positioned Aud DSX or Pioneer wide would probably be a major hit. So would setting up for DTS Neo X.Any of these 9/11.1 arrangements would eliminate any issue with sound dispersion.
     
  13. Robert_J

    Robert_J Lead Actor

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    The missing link - http://techtalk.parts-express.com/showthread.php?228195-Best-new-midwoofer

    Madisound will design something for you for a few hundred dollars. Not only do you get a quality design, you get years and years of experience. Designing a speaker may be a science but fine tuning one is an art. Buying the equipment for a one-time design is a waste. You have to have a drive to make this into a hobby. A very few go on to make it a career.

    As far as subs go, a few of these - http://www.danmarx.org/audioinnovation/tcsounds.html (almost any quality 15" sub will work in it) mated to a Behringer iNuke amp will crush any retail sub. The horn sub I linked to is truely over the top. It only plays to into the low 20hz region but it takes very little power to push it to reference levels. You are trading multiple, conventional boxes, some pricey drivers and a monster amp for a more complicated build, drivers that are easily obtained world wide and a small amp.
     
  14. Dougofthenorth

    Dougofthenorth Stunt Coordinator

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  15. Langotriel

    Langotriel Extra

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    I am a sound technician so even if it does not become my career specifically, it will be useful experience as i have said .. and it is fun XD. It is not every day you get to play around with $10000 at 20 years old :PI found this : http://www.audioexcite.com/?p=4301 They use the midwoofer i mentioned... would that be suitable you think? also: http://www.audioexcite.com/?page_id=4219 @Doug and Schan .. so if i understand it right.. the effects channels help fill in the space that the speakers leave? What other than the receiver would i need to achieve the desired results?
     
  16. schan1269

    schan1269 HTF Expert
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    Sound dispersion isn't a laser beam.Technically, what you are attempting to describe is called a bi-pole speaker.Bi-pole has been around since the 50s. They create their own challenges in design. Cause, in turn, they create a null in the center of themselves(bi-pole is never made where the dispersion patterns can mix. As in, your tweeters are aimed at sufficient angles the right side dispersion of the left one, does not mix with the left dispersion of the right one).Everybody makes bi-pole surround speakers.Di-pole is an out of phase variant.Simply aiming speakers "to a spot" only works for the sweet spot. Pick a spot in the room, everywhere else is a compromise.Bi/Di-pole is intended to diffuse sound...which will create the opposite of what you originally thought you'd get.
     
  17. Robert_J

    Robert_J Lead Actor

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    That published design is exactly what I was talking about. Someone has done the heavy lifting for you. All 3 enclosure designs look good. Pick the one that fits your space the best.Try speaker design on your own time and money. I started around age 16 back in the mid 1980s.
     
  18. Dougofthenorth

    Dougofthenorth Stunt Coordinator

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    @ Ben-Robert

    & in line with Sam

    1) Yes effect/presence speakers will add to & enhance the whole room's sound field - they would add to what your are trying to do.
    - I have not experienced them put at lower levels in front
    - I have only experienced them up high.

    2) "Sound dispersion isn't a laser beam." - it's more like a hose spraying water in a wide spray, not a narrow beam. & remember,
    all these streams are hitting each other & everything else in the room.
    "Any of these 9/11.1 arrangements would eliminate any issue with sound dispersion." -These will aid in solving your multi row issues. A single pair of 2 angled 2 speaker Side surrounds should serve well. Bi/Di switchable would be nice.

    3a) "What other than the receiver would i need to achieve the desired results?"
    - A receiver that is very capable of EQing the room well. Various types have various results IE Yam Ypao, Denon Audyssey, Pio Mcacc Etc - Higher level Yams have a rep for larger rooms. Any one with THX Ultra2 would be a plus.
    3b)Speakers that perform properly.

    4) other things are many - filling your 3 stepped row platform with sand. making sure the walls & ceiling don't vibrate, being able to effectively use 2 subs in the room not one, bass traps might be needed, acoustic panel wall treatments might be desirable - & on & on & on
    - building subs & placements is a whole other topic.

    But for now I will stick to speaker types & placements & the AVR & go from there
     
  19. Langotriel

    Langotriel Extra

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    Alright so we have the speakers ( http://www.audioexcite.com/?page_id=4219 ) that go around the room .. or the plans at least.. would it work to double up the same speakers for a centre speaker? wire it so it becomes 2 ohm and then it would get double power from an amp anyway.. the design would be doubled too.. like the box.. but it would be joined at the top.. so the middle of the centre speaker would have 2 tweeters with 2 woofers on the outside.. And what amp should i get for the 7 speakers? considering the tweeter is rated at 100w rms and the woofer at 60 watts rms..And for the sub.. the horn sub design looks interesting.. so i might go with that and then find some suitable drivers.Now, the receiver.. Will the A3030 do the trick? is there anything i should know? are there any true 11.1 that would be better suited for me at a similar price? Trying to get it all down so i can look at the total cost of this..
     
  20. Dougofthenorth

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