effect of a sub on my front speakers

Discussion in 'Speakers' started by KyleCT, Oct 11, 2003.

  1. KyleCT

    KyleCT Stunt Coordinator

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    I just bought a cheapo sub from costco (JLH E-10FB) just to see the effect it had on my front speakers (i heard that buying a sub reduces the amount of bass put on the front speakers). I was hoping that with the sub handling all the bass i would be able to turn up my front speakers louder, as they wouldn't be doing as much. My recieiver doesn't have a sub input but i plugged my front speakers in through my sub (wires from reciever to sub, sub to fronts).

    It doesn't seem like i am able to turn it up any louder than i could without the sub without hearing distortion. As a matter of fact, it doesn't even seem like its taking any stress off of my fronts. The sub has a dial on the back ranging from 40hz to 180 or something. Does this mean that the sub outputs whatever the dial is set to, and the fronts output the rest? What is the best setting for this?

    I guess my amp just distorts the signal at a fairly low level and buying a new reciever will be the only way to turn my speakers up louder.
     
  2. Aaron Gilbert

    Aaron Gilbert Second Unit

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    You're receiver's power output may not be the problem, but it's lack of built in crossover does seem to be.

    You are running a full range signal out to the subwoofer, which is fine, because the subwoofer has it's own built in crossover. However, the speaker level outputs on the subwoofer, to which you are connecting your front L/R speakers, may or may not have a crossover. If they do have a crossover, it will be typically a 6 dB/octave, or first order, crossover, which iis not steep enough to seriously relieve the front L/R of much bass.

    What you need is a receiver with bass management that allows you to set the front L/R (or any other speakers) to small, and uses a 12 dB/octave or steeper crossover for those small channels. A receiver so equipped will have a preamp subwoofer outout, so you would just need to run a single RCA cable to your subwoofer.

    I think your meant KLH, not JLH, right? [​IMG] I couldn't find detailed specifications on your subwoofer in a quick search, sorry.


    Aaron Gilbert
     
  3. Aaron Gilbert

    Aaron Gilbert Second Unit

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    Oh, to answer your questions about the subwoofer settings, the frequency adjustment is for the subwoofer itself, only. The subwoofer will output everything below the frequency at which you set the dial. The L/R output, IF it has a crossover, will be a fixed frequency and is completely unrelated to the subwoofer frequency dial.

    Most people tend to like a crossover setting on their subwoofer of 100 Hz or below, with 80 Hz being the most common. The lower you go, the better chance your subwoofer will 'disappear' in your room. How low you should set it will depend on the bass output capabilities of your satellites, which in your case doesn't sound so great. I'd try around 80-100 Hz. Any higher, and you will more than likely be able to pinpoint your subwoofers location in the room with your eyes closed, not a good thing.


    Aaron Gilbert
     
  4. KyleCT

    KyleCT Stunt Coordinator

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    yeah i figured i would need a new reciever. mine right now is a yamaha rx-v870. It was very nice about 10 years ago but right now it is outdated. How much has the technology increased over the last couple years as far as recievers putting out lots of quality power. My reciever right now has already blown out one set of polk R30's at not a terribly high level of volume. Would a new receiver allow me to crank the ish out of my speakers (at least to a higher level that my current reciever does)?
     
  5. Steve Lucas

    Steve Lucas Stunt Coordinator

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    Blowing speakers is all about distortion Kyle. Using a sub and bass management should help you get more volume out of your fronts before encountering distortion. But I'm still not sure you have a good understanding of exactly what it is that is hurting your speakers. If you don't understand what distortion is, find someone who knows and ask them to show you/explain it to you so that you can identify it when you hear it. Your speakers will thank you.
    It doesn't matter if your receiver is 10 years or 10 days old, if you push it into distortion, you are endangering your speakers. Most receivers power ratings are a bit optimistic, but they are a good point for comparison. One thing to remember though is that it takes something like a 6 fold increase in power to double the volume. So the difference between a 100 watt receiver and a 120 watt one isn't much when it comes to volume. If you really want to make your ears bleed, why not buy a receiver with as much power as you can afford and pair it with a really efficient pair of speakers, such as Klipsch. That will make the most of the power you have.
     
  6. Aaron Gilbert

    Aaron Gilbert Second Unit

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    Steve gives lots of good advice here.

    I would like to reiterate that your current setup does not allow removal of much bass at all from your main speakers, and depending on your subwoofer, it may be none at all. Is the RX-V870 a Pro Logic receiver? If it is, I believe it should have a subwoofer level preamp outout, although in the case of Yamaha, I think it's at a silly 200 Hz and may be full range anyhow. I can't remember if that vintage of Yamaha had any crossovers for the speaker outputs when the subwoofer output is used, but I don't think so.

    Steve's right though, if you are pushing your receiver into distortion, you're just asking too much of it and you should upgrade to a beefier receiver (or at least one that does proper bass management).

    It takes 10 times as much power to make a change in volume level that humans perceive as twice as loud. This also happens to be a 10 dB increase in the sound pressure level. Doubling actual power output only gets you a 3dB increase in SPL, so as Steve says, 100w and 120w is not much different.

    Isn't the RX-V870 at least 100w/channel? Seems like that should be plenty unless you like ear-bleeding SPLs or have really inefficient speakers. When you say it blew out one of your R30's, are you talking just the tweeter, just the woofer, or the crossover too? If it's just the tweeter, I would suspect you are overdriving your receiver into clipping. If it's just the woofer, I'd suspect you are overdriving the speaker, either by overexcursion or just sending it too much power. It's easy to push a woofer past it's excursion limits in a vented box if you play high volume material below the tuning point, which is likely about 40-45Hz in this speaker. The R30's at 89dB seem fairly efficient, should get you close to 110 dB excluding the bottom two octaves (20-80Hz).

    You really have two options - get a receiver with better bass management, or get significantly more efficient speakers (say 92dB or more). Ok well a third option would be to keep the volume lower... [​IMG]


    Aaron Gilbert
     
  7. KyleCT

    KyleCT Stunt Coordinator

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    im sorry maybe you didn't understand my question. I just went through a huge thread about blowing out speakers and the genereal consensus was the my reciever was putting out bad power and clipping the signal.

    When i blew out my speakers it seemed to be just the woofer. Someone just cranked the volume to loud and didn't notice the distortion.

    My recieiver is a pro-logic unit (80 watts/channel to the fronts) but it does not have a subwoofer input. That is why when i bought this sub i was hoping the crossover in the sub would reduce the bass played through my fronts.

    My question was has the technology changed significantly within a couple of years so that the signal does not clip until much higher levels of volume.

    Im not really worried about not being able to play music loud enough, im just afraid that some retard at a party will crank the volume when i am not around and blow my speakers again.
     
  8. Steve Lucas

    Steve Lucas Stunt Coordinator

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    In that case, the only thing you can do is either never leave your stereo unattended, or find out who the @#&% was who blew your last speakers and uninvite him from future parties.
    All amps will distort when pushed past their limits.

    Steve
     
  9. KyleCT

    KyleCT Stunt Coordinator

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    how can you tell before you buy a reciever what its limit is? If i am going to buy a new reciever i definately need to make sure its "limit" is a lot higher than my current recieiver.
     
  10. Dave_Olds

    Dave_Olds Stunt Coordinator

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    well, the watts will help as a guideline for how loud it would go but unfortunately the manufacturers seem to do this differently....

    A rule of thumb I use is to *never* push any receiver/amplifier past 7 o'clock or 70% of its total available volume....

    So if a receiver has 0 to 100 for settings, never past 70, etc....I apply this to car stereos, home theater, etc....this is a "safe" zone, you can likely go higher but the reward doesnt justify the risk, IMO....
     
  11. Zack_R

    Zack_R Stunt Coordinator

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  12. KyleCT

    KyleCT Stunt Coordinator

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  13. PeterSM

    PeterSM Auditioning

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    I have an old sub with speaker level inputs and a 6 dB/octave high pass crossover for routing reduced bass signal to the mains. At a crossover of about 100 Hz, the power is approximately -3 dB at 50 Hz and -9 DB at 25. The first octave, 100-50 Hz, is not -6 because the filter's slope is not linear at the crossover point. Anyway, with this setup, the amount of bass in the mains is is not reduced very much (as stated above).

    The reduction of power through the amp and to the mains depends on the amount of bass content and (as stated above) the amount of bass that is filtered out of the mains in the high pass filter, if any. If the signal were all bass below 100 Hz, then with a 6 dB per octave filter I would expect an average of -3 dB for typical rock music so the amp would be putting out a factor of 2 less power to the mains at exactly the same volume setting. However, it is hard to judge exact on the volume control. It would be easy enough to crank it back up to the same power level as before, making the mains only slightly louder because 3 dB is quite a small change in audible level. Then you are back where you started with no relief on the amp or the main speakers.

    I agree that an 12 dB / octave would give much more protection to your main speakers.

    If you are concerned about protecting your speakers at a party, you might consider putting a fixed attenuator in the circuit -- resistors of correct value in parallel and series. Unfortunately, that is not so easy to do with a receiver because you do not have easy access to the preamp signal. Attenuating speaker level output requires high wattage resistors, but it is simple enough to do. Or you could buy adjustable L-pads and hope your guests don't find them. [​IMG]

    Here's a link for speaker level L-pads. I would use the 100 watt version.

    www!lashen!com/vendors/csispeco/Installation/L-Pads.asp

    Replace ! with periods. it won't let me post the complete link because I have less then 15 posts. [​IMG]
     
  14. Zack_R

    Zack_R Stunt Coordinator

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  15. KyleCT

    KyleCT Stunt Coordinator

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    what do the L-Pads do and how do you set them up?
     

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