Could someone suggest a line-level crossover as low as 20 to 25 hz?

Discussion in 'Archived Threads 2001-2004' started by Chris PC, Apr 5, 2002.

  1. Chris PC

    Chris PC Producer

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    I would like to hear what my system would be like with my subwoofer filling in only the bottom portion of bass that my front speakers cannot manage. My fronts go down to 32 hz -3 dB anechoic. I am guessing if I got a crossover that had a range from 20 to 35 hz, I could use it to run my subwoofer off of my receivers front left and right main pre-outs. This would allow me to run the fronts LARGE and also SOURCE DIRECT and still have my subwoofer filling in the bottom end.

    Any suggestions?

    I am avoiding a speaker-wire crossover (passive) crossover because thats another option I will consider, but my fronts are Bi-wired and really, that wouldn't work too well running bi-wires through my subwoofer!
     
  2. Saurav

    Saurav Cinematographer

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    John Pomann sells a $75 kit that you can use to build one. It comes with a breadboard, opamps, power supply, amd more caps and resistors than you'll ever need. So, you don't even need to know how to solder - if you can read English and cut wire, you can build this [​IMG] Also, you can fiddle and play with the crossover parameters all you want. People who've built a crossover using his kit say it sounds as good as $400 commercial units.
    I bought one of the kits, and I'll get round to building it soon. I just got my subwoofer amp yesterday, next step is to measure my main speakers' response in my room so that I can decide on the crossover point and slope.
    If you're interested, I can find the link to his website.
     
  3. Chris PC

    Chris PC Producer

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    I'm interested!
    So its a good unit to do what I'm talking about, right? Crossover my receivers LEFT and RIGHT front pre-outs at somewhere between 20 and 35 hz? Is this a good approach?
    The only downside to this is that I am stuck letting the receiver and speakers cope with their bottom end limit of my front speakers response. For example, if they have output down to 28 hz, but its distorted, I guess its gonna stay distorted. Ultimately, I will get an outboard amp for my front speakers and use a crossover of say 30 to 60 hz, but for now, I just want to spend the least cash and get the perfect blend[​IMG]
    Sound cool?
    By all means, please post any links.
    thanx [​IMG]
     
  4. Ellen

    Ellen Stunt Coordinator

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  5. Saurav

    Saurav Cinematographer

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    Ellen, thanks. Chris, that's the link. Read through it - it's not the best organized, but it has a *lot* of useful information, especially on what you can do with the kit. The manual that comes with it is more detailed.
     
  6. Chris PC

    Chris PC Producer

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    Ellen Thank YOU for that link [​IMG]
    Saurav,
    Thanks for the helpful info. I am endlessly tinkering with my setup. Small 12 x 14 foot room, but also weird with two concrete walls and a concrete floor, two walls made of cheap panels that may or may not really be confining the long wavelengths. You know what I mean?
    Anyways...Basically, I'm a bass junky. I LOVE bass. So when I first configured my system, I wasn't keen on the sound. I thought the Marantz crossover was the culprit. Now I'm not sure, but I want to continue to experiment. One thing I wasn't sure of, is this:
    With the receiver set to FRONT=SMALL I have a highpass crossover of around 100 hz. But what about the subwoofer? I am not sure if there is ever a lowpass filter in the subwoofer pre-out of a corresponding 100 hz even when the FRONT=SMALL. I am looking for a TEST CD in order to figure it out. I suspect this because by going into the subwoofer directly, bypassing the subwoofers crossover, I found it didn't sound so good. Recently, I decided to try putting the subwoofer input into the subs crossover and setting the xover to, you guessed it, 100 hz. I could swear that sounds better. Either that proves that my receiver in fact does not have a lowpass filter for the sub pre-outs, or it just happens to sound good that way, cascading crossovers or not. I suspect that if it sounds good with the subwoofer crossover at 100hz and I find out that the receivers output ALSO has a 100 hz crossover too, than I am cacading crossovers, which isn't desirable. But even if this is the case, perhaps the cascade is eliminating a nasty round mode.
    Anyways.....the long and short of it is, I need to determine the low pass crossover of my receivers sub pre-out, if there is infact a low pass xover at all.
    The reason I am looking for a crossover for the subwoofer alone, is because I am actually happier with my system now, than I have ever been. I think I might be happiest with it this way, despite the 100 hz crossover, so I'd rather spend the least amount of money experimenting. So a crossover only, not a crossover AND an amplifier. Perhaps for reasons of sound quality alone, I'll get a stereo amp, but for now, I want to save money. And the final reason for putting a crossover in the subs path? I have found that there is significantly better or perhaps larger quantity of bass using the receiver in Source Direct. I find this annoying because regardless of the technical reasons, I'd rather not be compromising the sound quality in any way when I am listening to music OR movies with my subwoofer. Source Direct eliminates the subwoofer output. So by setting the FRONT=LARGE and sticking a crossover on the Left and Right pre-outs to send to my subwoofer, I'll get my BASS [​IMG]
    Phew..just a huge bass management brain fart!
     
  7. Ellen

    Ellen Stunt Coordinator

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    You're welcome! If nothing else, I'm a link junkie [​IMG]
    You might also look into the Project 09 24dB/Octave LR crossover discussed at Rod Elliot's web site. If you are at all handy with a soldering iron, the PCB should make it a pretty easy project.
     
  8. brucek

    brucek Second Unit

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    Chris,
    I would suspect that your receiver also bass manages the subwoofer output if it's managing the rest of the channels. It would seem strange if not.
    It's generally accepted that speakers should be bass managed a full octave above their spec'd lower limit. So if your mains are capable to 35Hz, then certainly a 60Hz or above cross would be appropriate in your receiver. You say your receiver is managed at a fixed 100Hz. Some find that a little high, although with so many challenged rears and center channel speakers, it usually works for a lot of people.
    Your idea is to run your mains full range, and then use your extra pre amp mains line level outputs (which are then full range) fed to your sub through some crossover you've constructed. Why? The sub woofer has a variable low pass filter on its line level input, does it not? Use it. It's a no cost solution.
    Feed the full range, line level signal to the sub and adjust its low pass filter until you get a smooth transition. As I indicated already, I wouldn't cross at 35Hz because you may end up with missing key areas. But this is something you can play with.
    I know you've indicated that you want to avoid using speaker level, but it's also a no cost solution to exactly what you're trying to achieve.
    Bi-wired speakers has nothing to do with it. I won't go into the fact that bi-wiring has no effect, but you can easily run a single set of speaker wires to your subs speaker level input, hooked in parallel to the main speakers low frequency inputs binding posts without any detremental effect.
    Then run your speakers as large and play with the subs own low pass crossover to obtain a smooth transition.
    Both these solutions would allow you a test of, the sub crossed very low while using full range mains.
    You're correct, your test of using the subs low pass filter and the bass managed sub signal from your receiver at the same time is not a good test of determining if the receivers sub output is crossed at 100. It may indeed make it sound better, but you are cascading two filters.
    Why don't you do a simple frequency response test of your system below 160Hz with a Radio Shack SPL meter and get a better feel for what the problem is before you make any decisions.
    There are lots of free tone generators.
    Download this FREE tone generator listed below and save the tones in three second files and burn them on a CDR.
    http://www.nch.com.au/action/index.html
    Scroll down to Freeware and click on TONE GENERATOR......
    Your testing should be limited to sixth octaves tones...
    Enter the values into the Excel graphs found at this site.
    http://www.snapbug.ws/bfd.htm
    brucek
     
  9. Saurav

    Saurav Cinematographer

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    Bruce, I've seen contrary opinions for some of the things you said:

     
  10. Chris PC

    Chris PC Producer

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    Thanks, I'm learning alot from this bit of info exchange.
    I have tried the tone generator to make a CDRW but I need to make the tones fade in and out to avoid popping.
    Brucek and Saurav,
     
  11. Saurav

    Saurav Cinematographer

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  12. brucek

    brucek Second Unit

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    Saurav,
    I do understand and agree with the points you're offering. The standard 2nd order HPF and 4th order LPF that most processors offer assumes a speaker rolloff, and isn't everyones cup of tea. But it works for most.
    My system uses this scheme and with EQ I can fairly easily compensate for crossover anomolies.
    Anyway, I usually temper my answers to the level of equipment sophistication and how deep or empty the pockets seem to be of the individual asking the question. In this case, for no charge, Chris will be able to have fairly good sound. I suggested a couple of ways of accomplishing this and encouraged him to do some testing (which he seems eager to enjoy) before he spents money that he indicated he was trying to save....... I didn't feel his question demanded the 2nd/4th order discussion with soldering iron in hand quite yet.. [​IMG]
    Chris,
    Again, I would encourage you to first take the time to get a deeper understanding of your system as it exists, including putting the ideas I originally gave you to use, doing a low end frequency response graphing using the built in low pass filter in your subwoofer and try and blend it with your full range mains. This information will better arm you to make a decision on whether you feel the 2nd order (or whatever) low pass filter in your sub will blend with your naturally rolled off mains.
    Check into the low pass filter specs of your sub. Some drop at 18dB/octave, some at 12dB. Just because your mains are spec'd at 35Hz down 3dB, don't assume that the bottom variable frequency of your sub at 50Hz won't blend nicely - check this out first. I suspect it may be a perfect blend. Do some response curves. You may be getting slightly ahead of yourself here... [​IMG]
    brucek
     
  13. Saurav

    Saurav Cinematographer

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    Bruce,
    Good point. I thought the discussion was already into soldering iron land [​IMG]
    And I agree with your advice, the first thing to do is to measure what the speakers can do by themselves.
    Also, someone told me that I'd be better off stuffing my speaker's ports and trying to blend that with a 2nd order slope XO on the sub. That person feels this works better than blending 4th order slopes, so.... I don't know [​IMG]
     
  14. Lewis Besze

    Lewis Besze Producer

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  15. Chris PC

    Chris PC Producer

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    Lewis. Not sure I can, but do any of the links posted above give you any help? You want line level or speaker wire level xover?
    Phew. OK. So test, test and test again. Only thing is, I won't be effectively testing the slopes of the receiver, speakers and subwoofer without also testing the affects of my room, unless I rent an anechoic room [​IMG] I wish I could use a voltmeter to figure it out. I do have a cheap radioshack multi-meter I could use if I knew what I was doing, at least for the receiver xover test.
    Also, the bottom line, har har, excuse the pun [​IMG] is to ge an agreeable sound. So if the sound of my FRONT speakers as LARGE and my subwoofer crossed over at 50 hz, or whatever its lowest setting is, hopefully CLOSE to the specified 50 hz [​IMG] then I would know whether or not that would be the first item I use to try and fine tune. I could have sworn that I have tried FRONT=LARGE and SUB=YES with the crossover all the way down and it didn't sound so good. So far, it seems that FRONT=SMALL and SUB=YES with and without the subwoofer crossover are proving to be the best. Again, I must test. Test, test, test.
    I find that I really like the sound of my front speakers when set LARGE, I just want a bit more bass.
    This whole speakers and subwoofers, sealed and ported thing is a long time coming for me. Its funny, I started shopping for speakers last March. I lived with a pair of Boston Acoustics A70 II's for 12 years. Anybody ever heard these speakers before? Good sound for the money and decent bass for a little speaker. I had been powering them with a 50 watt per channel amp the whole time. All I wanted last year, was to add the fuller bottom end, and free up the Bostons to clean up the midrange, so I was thinking I'd get a subwoofer. But the more I thought about it, the more I thought about getting entirely new speakers. So I started with the idea that a pair of PSB Alpha's and a subwoofer would be the thing for me. After going to listen, I compared the Alpha's to Paradigm Atom's, then to PSB Image 1B's and then finally I listened to a Paradigm Titan and PSB Image 2B. Well, I changed my mind, I wasn't going to get PSB Alpha's, cause the other speakers sounded better. But the big thing was, I was having a struggle with accepting that speakers were no longer SEALED designs. Even Boston Acoustics line that evolved from my old A70 II's was no longer sealed. So I proceeded to audition subwoofers. Each ported subwoofer I listened to sounded like a wet paper bag. Paradigm PW2200 and PSB Sub 6. Both were weird. I didn't hear that tight bass I was used to. I put it down to the ported design. So eventually, what I ended up buying was a Mirage BPS-400 subwoofer. Yeah. Huge, powerful and SEALED. I love the sound. I went again to listen speakers and found myself go from wanting 2B's to 3LR's to 4T's and ultimately, i was left deciding between the 5T and 6T's. The store let me take the 6T's home to demo them and after that, I couldn't turn back.
    So this whole thing has been a learning experience, because my PSB Image 6T's are ported, and I actually have measured that IN ROOM, because of the ported vs sealed slopes, the old Bostons actually doo pretty good in comparison, and actually have more output from 19hz (+1dB over the 6T's) down to 14 hz (+3 to 4dB). Ridiculous, because I doubt I'd barely even feel either speakers output that far below the response curve unless I listened to nothing but naked sine waves. Not wise to do too much testing that low anyways. The speakers aren't designed to play that low, so trying to measure those sub 20 hz frequencies can equal blown amp or blown speakers or both. Believe me, I just measured the barely audible tones. I didn't let the woofers flap! I'd piss myself if I blew my newer speakers through no fault but my own.
    Anyways.....what I have ultimately found, is, that although the roll-off of the PSB 6T's is steep below their 32 hz minimum, as they nose dive, becoming inaduible below 26 hz, I find their bass over their entire range is so smooth and clean, that I have learned to enjoy ported bass on one level. I just can't learn to love a ported subwoofer. I will continue to listen to them to see, but so far, they don't do it for me.
    So thats my story for using a SEALED SUBWOOFER and PORTED speakers and I'm sticking to it.
    As I said, the only thing I am hoping for, is to avoid distortion in my 6T's bottom end, and hopefully avoid wasting power down there too. Ultimately, I imagine if I could roll them off at a few hz higher, just to totally avoid distortion, I may try that, but maybe I won't need that. I will now get down to some testing with tones and the SPL meter.
    One last question. How much will a Do It Myself line level crossover of somewhere between 20 to 40 hz cost me anyways?
    Also, what equipment do you folks have anyways ? Curious to to know what my BASS teachers spend there ear time with [​IMG]
    thanx again for the help
    [​IMG]
     
  16. Michael R Price

    Michael R Price Screenwriter

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    I'd put a crossover way above 30hz on your mains. By cutting as much bass as possible from the mains, you reduce the stress on them and help them reproduce the rest of the sound with as little distortion as possible.

    By the way, I'm sure the 6Ts are great but there's no reason your mains should sound better than a good subwoofer (even a ported one).

    I suggest you plug the ports on your mains and cascade a 2nd order highpass crossover to get a nice 4th order Linkwitz-Riley filter to work with almost any subwoofer. The frequency would probably 50-80Hz.

    What ported subwoofers did you try?
     
  17. Chris PC

    Chris PC Producer

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    I like the sound of my mains bass response, they just don't go right down to the bottom end. I am not sure I'd like to cut all their low end out, but that might be the way I'd go in the end. If I had a choice, I'd choose to cross them over at 40 or 60 hz. Maybe even 70 or 80hz. I am finding that the 100 hz crossover is growing on me, or somehow, I tweaked something to my liking, because its sounding better as time goes on.

    I would like to try my subwoofer crossed over below my mains. I will have to see by testing.
     
  18. Allen F

    Allen F Extra

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    If you are a bass freak, you might want to pick up an AudioControl PCA (phase coupled activator). These gadgets "theoretically" restore lower frequency bass and can act as an electronic crossover. I just got one today, from ebay, and haven't had time to play with it yet. It didn't come with a manual, so I'm waiting to get the manual before I do any real experimenting with it. Just an idea.
     
  19. Chris PC

    Chris PC Producer

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    What is a:

     
  20. Allen F

    Allen F Extra

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