Question about x-over frequency on "small" channels

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PhysicsCoder
PhysicsCoder Posts: 40
edited July 2003 in Electronics
Hello, all...I gots me a question:

When setting a channel to "small" on my receiver, I have the option to adjust the crossover frequency (40 to 250 Hz). Is this frequency akin to the crossover frequency in a speaker, i.e. the mid-point (more or less) of some 3 dB per 8ve rolloff? Or, since it is a digital processor, is this a harder cutoff frequency?

In other words, if I set the crossover frequency to 100 Hz, how much power will get through to the speaker below 100 Hz?

Is this standard on all receivers, or is this one of those things I should ask the manufacturer about?

(yes, yes, I could borrow a noise generator and a digital scope from work and find out for myself, but that's a lot of equipment to be loading into my car...especially under the security cameras :D )

Thanks!

===========

Sony STR-DA2ES 6.1
Front : rt55i
Center : cs400i
Surround : JBL HLS 610 (soon to be f/xi 50)
Surround back : csi30
Post edited by PhysicsCoder on
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  • dorokusai
    dorokusai Posts: 25,576
    edited July 2003
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    PC - I had the same question and Sony told me that it is a digital cutover, with a 3db rolloff. This coming from the same people that cannot in any way shape or form, send me more specific specs on our line of receivers, but oh well.

    I havn't put my meter on it to check, since it hasn't worried me since, but I will and get back to you.

    I set all mine to 80hz cutoff, to match the sub.

    I believe this is a pretty standard way of using a digital filter in a receiver.

    You should get your Mission Impossible gang together and pick one up, :P
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • PhysicsCoder
    PhysicsCoder Posts: 40
    edited July 2003
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    I see...what, exactly, did they mean by "3 dB rolloff"...three decibels per what?

    Anyway, I may just have to do the mission impossible thing (begin theme music in 5/4). I'll see if I can borrow some equipment and find out for myself what's going on. White noise in and an FFT on the scope, baby! (my god, am I that much of a geek?)

    I'll let you know what I find. 'course, it's the weekend, so I'll have to wait 'till Monday at the earliest. :rolleyes:
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  • dorokusai
    dorokusai Posts: 25,576
    edited July 2003
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    That would be great, let me know what you find. You will be able to analyze the freq's better than I with my RS meter.

    Geek? Nah, just inquisitive ;) Like a monkey... just kidding

    They were not forthcoming with those specifics. I will check some other sources for some more specific information, and relay it to you. I found some pictures of a STR-DA4ES and 2ES with the tops removed for comparison, big difference visually.
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • HBombToo
    HBombToo Posts: 5,256
    edited July 2003
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    My guess would be ~12 dB loss per octive below the crossover point. I played a little bit with this when Doc sent me the freq sweep cd just to see what my h/k was doing and thats about what I saw.

    I have also seen nubers up to 18 dB per octive but thats pretty sharp.

    HBomb
    ***WAREMTAE***
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  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited July 2003
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    The standard high pass filter rate is 12 dB/octave. Ths affects all high passed speakers set to small. This relatively mild slope allows the high passed speaks to gently roll-off and still play bass well below the selected crossover frequency. This improves the transition to the subwoofer.

    The standard low pass filter rate is 24 dB/ocatve. This affects the subwoofer. The filter rate is very steep here to prevent the sub from playing above its effective range and also to prevent it from being localized.

    If you have larger bass-capable mains and center/surrounds with a rated -3 dB point of around 50-55 Hz, use 80 Hz as your crossover frequency. That will allow all the high passed speaks to play pretty strong down to about 60 Hz.

    If you have smaller speaks, I advise a 100 Hz crossover. If you have tiny sats, then you need 120-140 Hz.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
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  • PhysicsCoder
    PhysicsCoder Posts: 40
    edited July 2003
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    :cool: My Results :cool:


    Well, I borrowed the equipment from work. The good oscilloscopes were all, unfortunately, in use...connected to stuff...I had to grab one of the ancient analog 'scopes. So I could not, unfortunately, do a broadband test using Fourier transforms; I had to use single-frequency signals.

    The high-pass filters in the Sony STR-DA2ES do appear to be 12 dB per octave. It's tough to tell on that old friggin' scope (damn triggering circuit is shot to hell, too), but I guessed that it was about 10 to 15 dB. And since other people here have said that 12 is fairly standard, I think it's safe to assume that these HPFs are, in fact, 12 dB per 8ve.

    However, I found that the rollover actually starts about 10 to 20 Hz above the selected crossover point. (That is, 10 to 20 Hz at a crossover frequency of 100 Hz. I imagine the actual number is expressed as a fraction of an octave). The crossover frequency itself is, therefore, attenuated by a few dB.

    Again, it's hard to be precise with the equipment I had, but those numbers are at least a good estimate. (Now I remember why I use the good scopes at work!)

    Anyway, that's that. Maybe now I can go back to simply enjoying my music! :p
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  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited July 2003
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    Yep, 12 dB/octave is the THX standard and that's what most AVRs use as a default. The best pre/pro's can actually alter the high pass filter rate (6, 12, 18, 24).

    What speaks are you using? We can recommend the best crossover point if you want.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
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  • Loud & Clear
    Loud & Clear Posts: 1,538
    edited July 2003
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    Associated equipment...

    Sony STR-DA2ES 6.1
    Front : rt55i
    Center : cs400i
    Surround : JBL HLS 610 (soon to be f/xi 50)
    Surround back : csi30

    Two Channel Setup:

    Speakers: Wharfedale Opus 2-3
    Integrated Amp: Krell S-300i
    DAC: Arcam irDac
    Source: iMac
    Remote Control: iPad Mini

    3.2 Home Theater Setup:

    Fronts: Klipsch RP-160M
    Center: Klipsch RP-160M
    Subwoofer: SVS PB12NSD (X 2)
    AVR: Yamaha Aventage RX-A2030
    Blu Ray: Sony BDP-S790
    TV Source: DirecTV Genie
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  • PhysicsCoder
    PhysicsCoder Posts: 40
    edited July 2003
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    wow...for one really dumb moment, I thought "whoa! This guy has exactly the same setup as I do, right down to the JBL surrounds!"

    But then I realized it was a cut-and-paste. ...duuhhh...

    Anyway, I was just curious about the behavior of the crossovers. I've got them set to a pretty good spot right now by ear. But thanks for the offer. :)
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  • dorokusai
    dorokusai Posts: 25,576
    edited July 2003
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    PC - Here is some information I received on Agoraquest on our receivers....well the version before ours, but they should be pretty similar. It also clears up the semi-bogus Home Cinema review about output power tests done on receivers.

    http://www.agoraquest.com/viewtopic.php?topic=8253&forum=51
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited July 2003
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    Originally posted by PhysicsCoder
    I've got them set to a pretty good spot right now by ear.

    Looking at your speaks (and soon to be surrounds), I'd pick 80 Hz. I certainly wouldn't go any lower.

    You didn't list a subwoofer, so if you are not using one, you really shouldn't set your mains to small.

    With no sub, set your 55's to large, the sub to off/no, and the rest of the speaks to small.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
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  • PhysicsCoder
    PhysicsCoder Posts: 40
    edited July 2003
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    No worries, Spec. The mains are set to nice-and-large.

    Thanks for the link, dorokusai!
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