Anyone interested in designing some MTM's?

Discussion in 'Archived Threads 2001-2004' started by Bob Sorel, Jan 14, 2001.

  1. Bob Sorel

    Bob Sorel Stunt Coordinator

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    Hi guys,
    You know, as much as I love my Dynaudio Gemini's, I am seriously contemplating building some new mains and probably a center for my system. I am a DIY kind of guy, so I have been researching the very best drivers available at any cost, and I plan on constructing the cabinets myself. Since I have already begun building a pair of incredible subwoofers based on the HE 15 drivers, I would like to build "satellites" that would equal the quality of my subs. While investigating the possibilities, I have learned that passive crossover design is more art than science, and it takes many years to become adept at that particular aspect of speaker design, so I have been considering the "active" approach. Since enclosure design and speaker alignment are basically straight forward concepts and pretty easy to learn, I feel that using electronic crossovers and separate amps for each driver will make the system "gel" a lot easier than attempting to design passive crossovers. So I ask the people who have done extensive listening to active speaker systems, what do you think of active speakers (not necessarily digital) in comparison to passive speakers?
    Now, so far in my research, since I will only need these speakers to be good down to 80 hz, due to my HE 15 subs taking care of business below that point, my thoughts are to use a pair of mid-woofs and a tweeter in each cabinet, using the MTM approach. First of all, am I correct in assuming that the MTM design would be better than a MT (or is it TM) design in that it produces a wider soundstage and is capable of higher SPL's? The high SPL capability is important to me, as most of you already know [​IMG]
    I am tossing around the use of the Scan-Speak 15W/8530K-00 5" woofer and 15S/8530K-01 shielded woofer for the mid bass drivers and the Scan-Speak Revelator D2905/9900 tweeters, or possibly the Raven series of ribbon tweeters. What do you guys think of these choices and what others do you think I should consider?
    So any ideas and/or comments would be appreciated. If there is enough interest, maybe we can even get a group design going that might turn into the very best speaker available at any price, and since it would be a DIY project, it would only cost a fraction of the price of company manufactured units [​IMG] Anyone interested?
     
  2. ThomasW

    ThomasW Cinematographer

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    Bob
    Just to address some of the issues. You'll need baffle step compensation in the satellites. This isn't readily available in stock active XO's. Also I'd suggest looking at 6.5-7" diameter drivers. IMO for a good match @80Hz, the drivers need good output down to 40Hz. So I think the little ScanSpeaks, although great drivers, won't have adequate displacement, even in a MTM configuration down to 40Hz. It's best to design where the drivers are functioning in their most pistonic (linear)range.
     
  3. AjayM

    AjayM Screenwriter

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    Personally, there are so many excellent kits out there already that it may not be worth designing your own. Depending on what kind of sound you like, there is something already out there, http://www.speakercity.com offers a great ScanSpeak setup with the 8545 and up to the revelator tweeters if you prefer the softer sound, if you want a brighter sound you can look at the Focal Aria 5, or if you want a ribbon tweeter you can check out the Aria 5R with the Raven 1 tweeter. There's a ton of bookshelf/standmounted speakers available from http://www.zalytron.com using Seas, Focal, Cabasse, etc drivers.
    Now what I think would be intersting to see would be to build a bookshelf/standmount 3-way, use a good tweeter (Revelator, Focal, Seas Excel, Raven), a good dome midrange (ATC, Dynaudio) or maybe even a 3"-4" cone, and then throw in something like a 6.5"-7" mid bass (Scan Speak, Seas, Focal, Cabasse, PHL). Now as a starting point, you could have x-over points around 400/500Hz-6k. Just a thought...
    Andrew
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  4. Chris J R

    Chris J R Extra

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    Bob, just glancing through your post I am in a similar boat. I was intent on using the ravens, but I found out that if I wanted to use it in a center it wouldn't be wise. Well let me rephrase that, I have a normal TV ( not Big Tosh for me) and I was told taht the ravens magnets were too strong and would cause distortion in the picture of my TV. And even if I had a rear proj TV or something it still would be advised against. Just somethign I would throw out there. Good luck in your endeavors.
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    Rollo
     
  5. AjayM

    AjayM Screenwriter

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    That's true, the Ravens recommends some crazy distance from TV tubes, something like 12-18"....some people can put them real close though (like 6" away) and some can't.
    Andrew
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  6. Mark Hayenga

    Mark Hayenga Supporting Actor

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    I definitely have to agree with ThomasW on the bass extension issue, even though you might not need satellites with 40-50Hz response, it could help with integration.
    The only Scan-Speaks that I've heard are the ever-popular '9300 tweeter and a carbon paper 7" midbass. Both were very good, and I'd only expect better from the drivers you mentioned.
    Have you looked at the Seas Excel drivers? The magnesium cone midbasses and the millenium tweeter are fantastic.
    Also, have you considered line source/array type speakers? An RD-75 with paired with some nice bass drivers would be a simple and rewarding system.
    As far as active vs passive, I'd definitely go active if it was an option, though I think it's something of a misconception that it's necessarily easier than designing a passive xover. You might be able to get more help by going passive though, just because there are more people familiar with their design.
    Is there anyone in your area with the ability to measure frequency response and driver impedance (with Clio, Laud, etc)? Is there money in the budget for measurement and/or design software?
    Regarding MTMs, it is my understanding that they are harder to design than a typical MT. I might go with an MT just to keep it simple.
     
  7. Mark Hayenga

    Mark Hayenga Supporting Actor

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    BTW, is shielding an issue?
    Mark
     
  8. Greg Monfort

    Greg Monfort Supporting Actor

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    Here, ya go. http://www.e-speakers.com/hometheater.htm
    His other job is mixing movie soundtracks. Click on the studio link to see one of the best monitor walls around. I envy him.
    GM
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    Loud is beautiful, if it's clean
     
  9. Bob Sorel

    Bob Sorel Stunt Coordinator

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    Wow, I guess there is some interest in this idea [​IMG]
    Thomas, I think your advice on going with 6.5" to 7" drivers is well taken. Which drivers do you think I should consider? How about the SCAN-SPEAK 18W/8545 carbon fiber paper cone or the 18W/8646 Kevlar cone drivers? I have also heard good things about the Seas Excel drivers. Maybe something like the W17E 002 and the W17EX 002 for 6.5" drivers, or the W18E-001 and the W18EX 001 for 7" drivers? Any other contenders here?
    Andrew, yes, I've checked out the kits available everywhere, including Zalytron, but I just thought it might be more fun to do a group design [​IMG] A 3 way system would be very attractive also, but a newbie like myself wories about designing a good 2 way crossover, so a 3 way would be way out of my league at this point.
    Guys, I am not concerned with center channel shielding, as I have a front projector, though as a group design project maybe we should consider this. Other than the magnet issue, why wouldn't the Raven tweets be good choices? I haven't heard one yet, but I've been told that they are nothing short of spectacular, but then again, the $1650 R3 better be great for that kind of money. I was considering something more reasonable like the $200 R1 or the $300 R2.
    Mark, if there are people here who could help with passive crossover design, then I would be just as happy to go that route, since it would be cheaper than going active, and therefore allow some money for design software [​IMG]
    I don't have the room for arrays, and I forgot to mention that small size of the cabinet would be a consideration also, as my room has lots of constraints. Besides, there is no better feeling in the world than to have a small speaker that KICKS BUTT!
    If designing an MT would be easier than an MTM, then that would be absolutely fine, as long as the speakers can reach those high SPL's [​IMG]
    Right now I don't have anyone in my area that has the measurement equipment, but I can probably find someone in the Boston area that can help us. I'll start looking.
     
  10. Bob Sorel

    Bob Sorel Stunt Coordinator

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    Oh yeah, I forgot to mention, so far the best guy I have found in the area of crossover design seems to be George Short, over at North Creek Music. If you get a chance, read a much as you can on his site and you will understand why I believe he is tops.
     
  11. Brian Bunge

    Brian Bunge Producer

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    Bob,
    Unless you are dead set on doing a group design, which does sound fun BTW, ACI sells their Jaguar speakers in kit form for $749 (prices are about to go up, though). This speaker does use a Scan-Speak 7" driver and a 1" tweeter, although I'm unsure of the model#'s. These speakers used to sell for $5000 retail, so if you could deal with the crazy angles it would be a great speaker. A friend of mine just ordered the kit (should be here Tuesday) and I will be helping him build them.
    Also, I believe Norh is using both Revelator tweeter and the new Revelator 5.25" driver and getting great output down into the 30's! But at $200 for each driver and tweeter we're talking serious money here!
    Glad to see you looking at the Scan-Speaks!
    Brian
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  12. AjayM

    AjayM Screenwriter

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    Bob,
    I agree with most everybody else here that doing some kind of a high-end group design would be fun, although I don't think you'll ever manage to get a big enough group together that will agree on everything. [​IMG] As far as doing a 3-way, yes it will make things a little more difficult, but if the group can find somebody who can do some measuring then that design get's a little easier. Another idea would be to use the Madisound LEAP service, which will get you probably 90% there with the x-over, then do a little tweeking to go the rest of the way.
    Anyways, before all of that what kind of price point do you want to stay under? I know we would like to make the best, but the group will get smaller as the price goes up. I doubt there would be much interest in a Raven R3/Skaaning combo [​IMG]. Another option you could look at is using a Manger bending wave driver and your choice of woofer to create a nice full range system. I've had a brief experience with the Raven 1, and I was very impressed with it, except for it's narrow vertical dispersion, which could make it a problem if you can't make all the drivers (or more to the point all the tweeters) the same height. I also wouldn't specify doing an MTM vs TMM vs TM until you narrow down a driver selection.
    Andrew
     
  13. Bob Sorel

    Bob Sorel Stunt Coordinator

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    Okay, then maybe a modification of the project is in order here. In order to get as many people interested as possible, how about designing the best "bang for the buck" speaker we can? Since we are all a bunch of bassheads around here [​IMG] we can probably agree that we all will have great low ends to our systems already, right? Also, since different people will have the need to shield, while others don't, we should probably opt for drivers that are available in both shielded and unshielded versions, which would also eliminate the Raven tweets. Also, building and designing identical speakers (or a slight variation) for both the mains and center would be nice, as long as the center will sound equally good either in a vertical or horizontal orientation, as different people will have different needs here. If you guys want to do this, we can start a new thread with a title like "Let's design the best 'bang-for-the-buck' speaker anywhere!", or something like that. Does this sound like a better idea?
     
  14. MikeDG

    MikeDG Auditioning

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    I would also be interested in doing the group design. My xover skills are pretty weak, that is why I go with proven designs. As for cabinet making, I would be interested in an MTM, TMM, or 3 way design.
    I would like to use the SS 7's and 9900 tweeter or the Sea Mag., cones with any higher end tweeter. I would also like to try something with the Accutons, but they are pretty expensive.
    Mark, I am in Bulverde, Texas, about 1.5 hours from you.
    I am planning the Rick Craig STS and also have some Audax Aerogels HM170ZO's that I plan on teaming with Seas W21ex 002,s and an undecided tweeter. I am thinking of doing the Audax/Seas combo in the Wilson Watt look.
    Anyway, any idea, I would be interested in.
    Mark, I am going to place an order in the next week or so from a place that has outstanding prices on Scanspeak, Seas, Vifa, and a few others. THe more you buy, the better the deal, if you would like to get in on the order let me know.
    As for Bang for the buck, maybe we should give the Tangband tweeter a shot, it also comes in a shielded version.
     
  15. Bob Sorel

    Bob Sorel Stunt Coordinator

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  16. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Bob, a passsive crossover isn't necessarily less expensive than an active. Prices for quality heavy-gauge inductors and film-and-foil or metallized film capacitors are very high. I've seen some active crossover plans that would definitely cost less. The challenge with actives is that you have to make your own PCB's or use breadboard.
     
  17. ThomasW

    ThomasW Cinematographer

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    Bob
    Options for 6.5"-7" midwoofers are really a personal preference. I prefer the Eton Hexcone Kevlar units. These to my ears are the most neutral/transparent sounding drivers available. I've used the ScanSpeak woven kevlar drivers and I don't think they offer the midrange clarity available from the Etons. The Hexcone Kevlar's aren't currently real popular items with the "in crowd". Primarily because they don't have the bass "punch" of the carbon fiber or woven Kevlar units. This of course isn't an issue given your subs.
    Use an active XO for the sub to midbass XO point, and then build a good passive for the midbass to tweeter. It's much easier to put the baffle step compensation in a passive than to breadboard and install it in an active XO.
    Hank is certainly correct regarding the cost of a good passive XO. Also to my way of thinking I'd rather have one extremely high quality amp driving the "top module", than an active XO and 2 average amps. This is one point in the signal path where amplifier differences can easily be heard.
    As far as tweeters are concerned here too, I don't run with the pack. Soft domes are great if you want something not very revealing. My preference is the Focal 120dx2 with a properly designed XO. This tweeter is revealing to a fault. And without proper XO design can sound harsh. With proper XO design IMO nothing is better, with the exception of a great leaf.
    One final item for consideration should include your propensity for high SPL's. As we learned in the subwoofer troubleshooting thread, you like your music somewhat on the loud side [​IMG] So the mininium configuration should be an MTM. And components should also be chosen with that in mind. Many of the high end kits are truly not engineered to take a pounding, especially those with first order XO's.
     
  18. MarcS

    MarcS Stunt Coordinator

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    If you haven't already, try posting your request to the Madisound Forum--I'm sure you'll get a lot of responses there...
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  19. Mark Hayenga

    Mark Hayenga Supporting Actor

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    Oh my, this is going to be FUN! I expect there's going to be a lot of different experiences brought up in this thread [​IMG]
     
  20. Bob Sorel

    Bob Sorel Stunt Coordinator

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    Hi guys,
    Well, I guess we have have come to one agreement so far, and that will be the use of a passive crossover between mid-bass and tweeter, right? I'm sure we all have electronic crossovers already between our subs and satellites, so that part is history [​IMG]
    Well, if we are going to do this design specifically for me, I think that an MTM or TMM would be in order, as I would like to get the highest SPL's possible from these speakers [​IMG] (the higher the SPL's, the better [​IMG] )I already have MTM's in my system, and I think they are great, except for the fact that the center speaker sounds kind of "boxy" if it is used horizontally, and seems to bring down the soundstage, but it sounds great when used vertically. Is there any way to design a center that won't destroy the soundstage when mounted horizontally, as that would be the preferred mounting?
    Now, as far as tweeters are concerned, I am currently using a Dynaudio D260, and I think it is pretty darned good, but I am deinitely looking for ideas on a better one. A "revealing" and "detailed" tweeter is great news, but a "harsh" one would be bad, and wide dispersion for "airy" music (like symphonic) is a high priority also. So what are the contenders here, and for how much money?
    As far as mid-bass drivers are concerned, there seems to be a lot of opinions on these. Again, I would like to get the flattest, truest sounding mid-woof available. "I have a high end pre/pro (the TAG McLaren AV32R-EX) for my front end, and it is virtually faultless, so I would love to have drivers that would do it justice. Accuracy, crystal clarity, and high transient response are all terms that I would use to describe the TAG's strong points, and the Dynaudio's do a pretty good job now, but I would like to have better, if that's possible. Ok, here again, let's put together a list of contenders and their prices. Again, if it's for me, shielding is not an issue, but if there are others who want to join in, we may have to consider shielding as well.
    Once we get the drivers selected, then we can proceed with cabinet and crossover design. I'm sure that the enclosures will be fairly straight forward, but crossovers are another beast entirely, so we'll cross that bridge when we get to it.
    If there are others who are reading this thread that would like to have a say in what's going on here, please at least post that you are interested and what concerns you have about this project. If no one else is planning on building them, then we can just design them for me [​IMG]
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