DIY HT system design recomendations

Discussion in 'Home Theater Projects' started by PasqualeF, May 6, 2003.

  1. PasqualeF

    PasqualeF Auditioning

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    I am planning a 5.1 system that will be used 50/50 music/HT but if I had to compromise I would prefer the music to sound better. Due to budget I think I will be using all vifa drivers. I have decided on 3 way mains with dual woofers and have been recommended the D27 tweeter, the P13M mid, and dual P21W's. Do you think the dual 21's are just too much speaker? I was thinking more along the lines of dual 17's. Note that I will also be using a tempest.

    For the rears the distributor of the speakers has recommended 2 ways with dual P21W's and a D27. This is far from my intended single P17 and D27. The box for the dual 21's would have to be at least 60 liters! Again is this too much?

    What do you guys think? The room is 5m x 7m with high ceilings and carpet.

    Also just on the drivers, do you think you can get really good sound from vifa's? I have used them before but never really tried to optimize them. And last thing do you think the P13M mids will be loud enough for music in my large room?

    Thanks for any help.
    Pat.
     
  2. If you have built some speakers in a reagular 2-way and found it a little difficult, you'll find that the 3-way is an order of magnitude harder!!!

    What is your budget for all 5 speakers for the drivers and XO parts?
     
  3. PasqualeF

    PasqualeF Auditioning

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    I don't find speaker building difficult, in fact I am quite confident with it, and I have built 3 ways. I have lots of experience with custom/high end car audio, which is I think more detailed than HT. The car interior has to be the worst place to reproduce music, and the fabrication side, to finish things off with vinyl/fabric/paint so they look like they were meant to be there is quite a skill.

    I was just saying that the speakers I have built with vifas sounded ok with average enclosures and simple crossovers, but I was wondering could they sound almost audiophile like with well built enclosures and optimized crossovers.

    My budget, well I don't really have one, just not to spend too much. Originally I thought about using all scan-speak components but when I calculated the cost of the drivers only I got a fright. An all vifa system will be well within reason.
     
  4. Dave Crigna

    Dave Crigna Stunt Coordinator

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    Yes, you can have a very audiophile like system with those vifa drivers. Vifa is used in some high end speakers lines starting from 2000.00 plus range. But, be prepared to spend some money on the crossovers. In one thread anthony managed to explain the use of the crossover very well. Think of drivers as the computer with the crossover being the brains that runs it. With that in mind, that is where it can be very expensive or inexpensive depending on the parts you use and the quality you are after. There is also something to be said for box design and location of the drivers in the box.
     
  5. Do you want the challenge of designing your own speaker from scratch or do you not mind using an existing well reguarded design and build your own cab?
     
  6. RichardHOS

    RichardHOS Second Unit

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    It is possible that bi-amping each speaker and using active crossovers could be cheaper. And, possibly better sounding. For example, you can often find a 50Wx2 amp for half the price of a 100Wx2 amp (and, actually, the 50Wx2 would be twice as powerful with active crossovers due to the way superposition of signals works). So instead of 7 channels X 100W (estimate), you might have 14 channels x 50W (or 25W for equivalent power to the 7 X 100W).

    As for crossovers, active 2-ways can be built for around $15 per channel - and that's for fairly high quality components.

    At least something to think about.
     
  7. PasqualeF

    PasqualeF Auditioning

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    Anthony, I suppose I do like a challenge but I don't at all mind using an existing proven design. Actually the cabinets are of an existing design (the swans M3) but because I have changed the drivers the dimensions and crossover will be completely different. Why, do you know of any designs in this configuration?

    Dave, yeah thats what I thought. It's just that I have heard some people rubbish vifa in a major way. I'm sure if you wanted the utmost sound quality then you get what you pay for but I've always found vifa to be very good quality for the price. Just to let you all know I am going to have the crossovers professional modeled for the drivers.
     
  8. Jonathan M

    Jonathan M Second Unit

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    Why are you going 3-way on the fronts? I would personally go with twin P17SJ's and the D27 in a 2-way MTM or maybe a 2.5way at the most. The twin P17s will correct for the efficiency loss due to baffle step. As for the P13, it's got 4mm of Xmax, so will be fine in a midrange only role - just don't expect it to perform to high levels down low.

    Coupled with the Tempest, you'll have plenty of low-end with just the 2 P17s.

    I would personally go for sealed enclosures with an F3 of 80Hz or whatever the xover frequency of your receiver is. Most receivers have 2nd order (Butterworth) highpass filters, and 4th order Linkwitz-Riley lowpasses, which means a sealed speaker with an F3 of 80Hz fits real nice. If you're receivers xover goes lower to say 60Hz then you could go sealed at 60Hz or whatever. Just be careful of having too many sources of deep base, as room effects can be hazardous even with a single source.

    I personally suggest 2 ways if you can get away with it. Whilst I agree that building a 3-way isn't TOO complex, a 2-way is certainly much easier. What sort of measurement system will you be using?

    A single P17/D27 combo will probably be fine for the surrounds. I'd focus quite a bit of effort on the centre (Identical to the mains would be ideal).

    Just some suggestions.
     
  9. PasqualeF

    PasqualeF Auditioning

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    Richard, that is possible and I may think about it when I have time (I'm supposed to be working now!).

    Jonathan, Thanks for answering my question completely. 2 or 2.5 ways would probably be suitable. There's no reason for going with 3 ways other than I have always liked them and always wanted to build a really nice set. Until someone can give good reasons why I should NOT go with 3 ways then my design will stick with them. What do you mean by measurement system? Yeah I think I will stick to P17/D27 for the surrounds. The center will be P13's and a D27 in a MTM setup (same midrange and tweeter as mains). So back to my question, you think 2 P17s will match up nicely with the sub? If they can play clean and strong down to 50 I would be very happy. I don't really want the sub to go to far over 60-70 if I can help it.
     
  10. Jonathan M

    Jonathan M Second Unit

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    One reason to NOT go 3-way:

    If you are planning on using the P17, then one good reason not to do a 3-way is because the P17 has a very good mid-range response anyway. IMO you'll be wasting this ability. I would go for a larger driver (8" at least) if I was going 3-way.

    As for the low end, remember that the xover that you use in your receiver will effect what the speakers will end up doing. There's no point designing mains that go to 50Hz if you then highpass them at 80Hz. If you're receiver can highpass at 60Hz or whatever, then you might be OK. I personally use the receiver's active xover to my advantage - it reduces power usage by the main amps (You are effectively bi-amping) and means the mains have less of a hard time. With that said, however, a 5x7 room is fairly large, so will need decent low-end output to fill it. It may be better to remedy this situation with another sub, rather than trying to get a lot of low-end out of your mains. If I was in your situation I'd probably go 2-ways all round with 2 P17's in each of the fronts, and either 1 or 2 P17s in the rears too. They'd be sealed with F3 either 80Hz or 60Hz - depending on what I'm using. Note that if you use 60Hz you'll probably be losing some of the LFE channel's content. This isn't too much of an issue IMO though, as it is often present in the other channels as well.

    As for going completely active, it's only really doable well if you account for the acoustic response of the drivers in the active xover. Not many people do this, and thus a well designed passive is often better than a standard active xover as far as the driver's integration goes.
     
  11. Chris Tsutsui

    Chris Tsutsui Screenwriter

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  12. PasqualeF

    PasqualeF Auditioning

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    Jonathan makes some good points on why to go for dual 21s rather than 17s (which was the original question) but hopefully answering your questions will help me more.

    I like to drive a speaker as low as it can go while remaining linear. Like I said, if I can get the mains to do an honest and strong 50Hz I would be happy to go down from there with the tempest.

    Thanks for your detailed questions.
     
  13. PasqualeF

    PasqualeF Auditioning

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    Chris?...CHRIS???.............CHRIIIIIIIIIIIIIIIIIIIIIIS!!!!!!!!!
     
  14. PasqualeF

    PasqualeF Auditioning

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    Has this thread reached the point of diminishing returns?
     

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