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My first 3 way speaker build

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  • mattsk8
    replied
    Re: My first 3 way speaker build

    Originally posted by Sydney View Post
    So nothing is running hot?
    Not abnormally. Those Adcom amps are tough to monitor though because just sitting idle with the power on the thing gets pretty hot anyhow. It does have thermal protection, and "distortion" LEDs. But it isn't doing anything out of the ordinary, and I ran it pretty hard last night

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  • Sydney
    replied
    Re: My first 3 way speaker build

    Originally posted by mattsk8 View Post
    ...My amp didn't seem to mind this at all yesterday, and I had it playing for about 4 hours....
    ...But,I'm glad that's sorted out now!!!
    So nothing is running hot?

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  • mattsk8
    replied
    Re: My first 3 way speaker build

    Originally posted by rpb View Post
    What's your high pass on the mid? Does it use a rather large coil, or a small one? Playing with PCD on a different driver, it looks like a big coil helps get the impedance up. I mean something around 4mH when I say big.
    Originally posted by chrisn View Post
    I noticed there are different advertised specs for that woofer, such as vas between 66-102: http://www.sbacoustics.com/index.php...29swnrx-s75-6/ Have you tried modeling your box with the various listed numbers? It's not unusual to pad the tweeter and the mid, and depending where and how you pad them can change the impedance and phase angle your amp sees. Split resistors for larger values, like 4 ohms on the amp side, and a similar amount the driver side, or a resistor in parallel (across the terminals of the driver) are different ways to match the drivers relative levels, Crossing to the mid higher could help too, and going second order electrical on the mid high pass if it isn't already. Rpb's advice above is right on.
    I did model the box and it showed a 2.25 box would give me f3 of 25 Hz using SB's specs. The box I have now is 2 cf and should have f3 of 27 Hz using a 3"x12" port. The mid to tweeter is around 2.2k, the woofer to mid was 225, but I need to measure it again to see what the 4.0 inductor did.

    But... I made very positive advancements last night . I put a 4.0mh in place of the 3.0 on the woofer, used a 200 rather than the 250uf, and still used the 2.4 resistor and the bass sprung to life (thanks again... and again Craig K for finding this out). I have the mid padded a bit, and the tweeter quite a bit (but a lot less than yesterday), now the bass is almost perfect (is the bass ever totally perfect in anything?). I'm super happy with where these are now, I think I need to just listen for a week or so at this point and digest what's there before I move into playing with the high frequencies. They're a tad thin in the upper midrange, but they're also new speakers and I imagine that 7" Scanspeak mid will take a while to break in when it isn't playing much bass at all. My amp didn't seem to mind this at all yesterday, and I had it playing for about 4 hours.

    I really appreciate all the tips and suggestions, I love this forum. I've made a lot of good friends and met some really cool people . Now I see why people like a good TM or MTM, 3 ways take a LONG time and a lot of work :eek:. I was a tad nervous when I fired these up that I'd lit about $1000 on fire, glad it's starting to come together :D.

    From what I hear so far, the really nice thing is that these drivers all seem to have plenty to offer. As much as I've practically damned that SB29 woofer here because of my lack of understanding, it really is a good driver. It doesn't miss any of the bass frequencies, it has a very smooth and consistent sound all the way into the 20s. Some drivers will be exaggerated in the bass frequencies somewhere, but then they'll be lacking somewhere else; but that isn't the case with these, they're smooth all the way through.

    Now that I have the bass sorted out, I'm honing in on that SS HDS tweeter; not sure where I stand on that yet. It has detail like crazy, but I'm not sure yet if I'd like a tad more body in the lower end. I'll listen for a week, then go back to playing with it.

    Originally posted by Sydney View Post
    That's not good - from a personal perspective, post amplification attenuation is like riding the brakes.
    That's a good analogy, it's like putting a 200 HP restrictor plate on a 500 HP engine. But,I'm glad that's sorted out now!!!

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  • Sydney
    replied
    Re: My first 3 way speaker build

    Originally posted by isaeagle4031 View Post
    ...or go active. ...
    :D

    Leave a comment:


  • isaeagle4031
    replied
    Re: My first 3 way speaker build

    Originally posted by Sydney View Post
    That's not good - from a personal perspective, post amplification attenuation is like riding the brakes.
    The only way you would not have post amplification is if you can either find drivers that "perfectly match" spl wise (not going to happen, particularly in a 3way) or go active. Using resistors to level match and/or response shaping is quite common and really the best way from a passive crossover standpoint.

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  • Sydney
    replied
    Re: My first 3 way speaker build

    Originally posted by mattsk8 View Post
    ...To make these really sound good, I had to pad the mid with 7.7 ohms of resistance, and the tweeter with 11 ohms. Now they sound perfectly magical, but I don't think my amp can handle what I'm doing. These are terribly inefficient, after I listened to them for about 2 hours last night I could fry eggs on the amp I'm using to voice these (Adcom GFA-5500), it was almost too hot to touch....
    That's not good - from a personal perspective, post amplification attenuation is like riding the brakes.

    Leave a comment:


  • chrisn
    replied
    Re: My first 3 way speaker build

    I noticed there are different advertised specs for that woofer, such as vas between 66-102: http://www.sbacoustics.com/index.php...29swnrx-s75-6/ Have you tried modeling your box with the various listed numbers? It's not unusual to pad the tweeter and the mid, and depending where and how you pad them can change the impedance and phase angle your amp sees. Split resistors for larger values, like 4 ohms on the amp side, and a similar amount the driver side, or a resistor in parallel (across the terminals of the driver) are different ways to match the drivers relative levels, Crossing to the mid higher could help too, and going second order electrical on the mid high pass if it isn't already. Rpb's advice above is right on.

    Leave a comment:


  • rpb
    replied
    Re: My first 3 way speaker build

    What's your high pass on the mid? Does it use a rather large coil, or a small one? Playing with PCD on a different driver, it looks like a big coil helps get the impedance up. I mean something around 4mH when I say big.

    Leave a comment:


  • mattsk8
    replied
    Re: My first 3 way speaker build

    Originally posted by chrisn View Post
    A 2mh inductor seems rather small for a 200~hz crossover, 4-6mh is more "normal". 250uf cap could be too big, try a lower value (68-200) if you can. Are you listening to just one woofer or both? Sometimes just one will sound a little weak, if two, one could be wired out of phase from the other woofer. You have a nice selection of drivers, a little fine tuning and you'll have a very nice set of speakers.
    Thank you very much for the suggestions. I started with a 3mh inductor, I swapped that to the 2 just to see what would happen and it didn't really have much effect on the bass (it did pull the lower mid up a tad, as you would expect). I haven't tried going higher than 3.0 yet though, maybe that should be my next move. I did try a 200uf cap in place of the 250, and that didn't help. What did make a difference was putting a 50watt, 2.4 ohm resistor on the negative wire side of that 250uf cap, that pulled the slope down even more. I will try a higher inductor and see what happens, but here's what I think is going on...

    I've been playing with these a lot, and short of going higher than 3.0mh on the inductor I've tried everything I can think of. The thing with speakers is, you can always pad to make them quieter, but you can't make them play louder. I think the issue is that even though the SB29 woofer is rated at 88 db sensitivity and the SS 18w mid is rated for 90 (these should technically work together), they aren't even close. I think in the frequency range I'm using this woofer, the sensitivity is just plain awful, I'd say 86 db is a stretch.

    To make these really sound good, I had to pad the mid with 7.7 ohms of resistance, and the tweeter with 11 ohms. Now they sound perfectly magical, but I don't think my amp can handle what I'm doing. These are terribly inefficient, after I listened to them for about 2 hours last night I could fry eggs on the amp I'm using to voice these (Adcom GFA-5500), it was almost too hot to touch. I wasn't listening at insane volume levels either, it wasn't quiet but it definitely wasn't overly loud. I think I might be in the market for a different pair of 10" woofers, only I'm going to use something that has a good history this time, rather than being a guinea pig.

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  • chrisn
    replied
    Re: My first 3 way speaker build

    A 2mh inductor seems rather small for a 200~hz crossover, 4-6mh is more "normal". 250uf cap could be too big, try a lower value (68-200) if you can. Are you listening to just one woofer or both? Sometimes just one will sound a little weak, if two, one could be wired out of phase from the other woofer. You have a nice selection of drivers, a little fine tuning and you'll have a very nice set of speakers.

    Leave a comment:


  • mattsk8
    replied
    Re: My first 3 way speaker build

    Originally posted by augerpro View Post
    I just thought there would be something to learn here by understanding what "went wrong"? Just the OCD troubleshooter in me
    That I understand completely! I was hoping you'd say something along the lines of "just bump this value and move that piece, then they'll pound like a pair of 12" subs in the back of a station wagon" .

    There was another guy on the forum here that tried using these woofers too and had the same issue, he ended up going active (don't remember his name, something Dunn?). What I have now is very respectable, but still not what you'd expect from a 10" woofer from a SPL perspective. They're very musical, the sound is exceptional. They don't miss anything, the bass is very smooth and accurate. I just wish I could pull a db or 2 more out of them.

    I'm at the point now where I think I need to step back from tweaking and just listen for a week or so.

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  • augerpro
    replied
    Re: My first 3 way speaker build

    I just thought there would be something to learn here by understanding what "went wrong"? Just the OCD troubleshooter in me

    Leave a comment:


  • mattsk8
    replied
    Re: My first 3 way speaker build

    Originally posted by augerpro View Post
    This was all measured and modeled? Could you post the predicted response and filter transfer functions of the active and passive versions?
    I'm not sure what you mean by "transfer functions" regarding the active xover; you just dial the preamp to 200 Hz (as high as mine would go), I set the slope at 24, then attenuated it with the subwoofer volume setting in the preamp. The only transfer function is the dial on the preamp. I didn't spend any time measuring, because I don't want active. The only reason I did that was to see if the woofer was capable all by itself, which it definitely is, so that told me something in the xover is stifling the bass.

    As far as modeling the xover goes, I basically pick the points based on the measurements, and I have someone that understands these a lot more than I do model the rough xover for me. I know how they work, but don't want to spend the time learning the design software, it's a lot easier to things this way. I'd post, but they'd rather stay anonymous. Once I get the parts he tells me to use roughed in, I tweak everything.

    I guess I'm not really sure what you're looking for, or more, why you're wondering. The TM is crossed at 2.3, and the mid/woofer is crossed at about 225. I have also measured them done, and they're very flat now, thanks to Chuck Morris helping me understand reverse null. I had a decent bump at 1.8k, Chuck helped me figure that out.

    That said, if you have something I should try different on the woofer, I'm all ears.

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  • augerpro
    replied
    Re: My first 3 way speaker build

    This was all measured and modeled? Could you post the predicted response and filter transfer functions of the active and passive versions?

    Leave a comment:


  • mattsk8
    replied
    Re: My first 3 way speaker build

    The biggest difference in bass was adding a resistor in the woofer shunt. But they still sounded kind of thin and shouty, so I swapped the 3.0 inductor with a 2.0 and it filled it in amazingly, w/out having an effect on the bottom end.

    As far as the second part, yes and no. The end goal is ideally the same, but crossing active changes the signal before the amp sees it so you aren't necessarily manipulating electrical current. Changing things in the passive xover always opens a new can of worms. For example, swapping an inductor to try to pull midrange up could effect the bass too. With active xover, you can essentially just shut off whatever you don't want to hear.

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