My sub made my speakers sound worse... - AVS Forum
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post #1 of 10 Old 01-09-2013, 05:21 PM - Thread Starter
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And not in the bass range where a poorly tuned sub could make a big bass hump. It was the vocals. They sort of faded into the background. Without the sub, I hear Christina singing, with the sub, I hear a speaker that's playing Christina. Could it be a bad crossover in the sub?

Speakers: Polk RT25i
Sub: Velodyne VA1215X II
Receiver: Onkyo TX-8511 (100w x 2)

The Receiver doesn't have any pre-amp outs so I'm running speaker level to the sub and then running from the sub to the speakers. Highpass crossover set to 80Hz, lowpass set to 110Hz.

Ideas?

I actually feel bad because I've owned these speakers for 10 years and never thought much of them. Now that I've hooked them up without the sub I'm much, much more impressed. And they produce pretty respectable bass on their own anyway. Oh well, live and learn.
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post #2 of 10 Old 01-10-2013, 09:29 AM
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I'm not sure what you mean by "highpass crossover" and "lowpass crossover'.

Are you talking about your subwoofer controls or receiver software menu settings? I am assuming you mean the controls on the sub'

In any case, your main speakers and sub are probably interfering with each other and working poorly with those settings and connections. In any case, any female voice is well above 200 Hz so there is some kind of indirect or "masking" effect going on.

The Polk RT25i is rated by Polk to go down to 50 Hz, but that is a GROSS misrepresentation.

According to the tests performend by Stereophile in their lab, That speaker is actually nearly 5 DB down at 80Hz , so it is only going to operate at 100 Hz and higher. It is pretty much worthless below 100 hz. Any "bass" you are hearing from them is going to be above 100 Hz.

This means that your subwoofer needs to be set to operate up to 100 Hz, BUT NO HIGHER!!!!!

The worst thing you can do is to have an OVERLAP in frequency operation between the two. I am sure that is what was causing your problem.

Set the filter on the sub itself so it operates ONLY below 100 Hz.

The main thing is this; you should run 14 gauge or 12 gauge speaker wires DIRECTLY from the receiver to the main pair of speakers, THEN run smaller wires (16 or 18 gauge) from the speakers to the sub input terminals. The wires from the speakers to the sub can be much smaller because they carry only a very small signal current when hooked up in this manner.

This way the main speakers will not be compromised and will operate directly off of the receiver without interference (all receiver software should be turned OFF).
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post #3 of 10 Old 01-10-2013, 10:30 AM
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Quote:
Originally Posted by alwayssummer View Post

And not in the bass range where a poorly tuned sub could make a big bass hump. It was the vocals. They sort of faded into the background. Without the sub, I hear Christina singing, with the sub, I hear a speaker that's playing Christina. Could it be a bad crossover in the sub?

Speakers: Polk RT25i
Sub: Velodyne VA1215X II
Receiver: Onkyo TX-8511 (100w x 2)

The Receiver doesn't have any pre-amp outs so I'm running speaker level to the sub and then running from the sub to the speakers. Highpass crossover set to 80Hz, lowpass set to 110Hz.

Ideas?

Get an 5.1 AVR with bass management which implies a line level output for the sub. You can get such a thing for about half the price of the sub, so view it as protecting your investment in the sub.

Things are good, even near the bottom of Denon's line, they tell me.

5.1 AVRs do 2.1 spendidly if you tell them that there are only fronts and a sub.
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post #4 of 10 Old 01-10-2013, 03:52 PM
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If I've found the correct manual for that sub (http://velodyne.com/pdf/va/va-1215xii_manual.pdf), its got separate HP and LP controls but they are only 6db/octave filters (yuck)

You can probably make it work, first thing I would do is set the high pass and low pass to the same frequency then get an SPL meter and make sure the levels match and your not getting any phase cancellation (correct with the phase knob). You can sorta do the phase test with just your ears if you have to. Use your computer to generate a test tone at your crossover frequency, sit in your listing position, have someone man the phase knob on the subwoofer and mess with it till you find the place where the tone sounds the loudest.
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post #5 of 10 Old 01-11-2013, 07:21 AM
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Quote:
Originally Posted by arnyk View Post

Get an 5.1 AVR with bass management which implies a line level output for the sub. You can get such a thing for about half the price of the sub, so view it as protecting your investment in the sub.

Things are good, even near the bottom of Denon's line, they tell me.

5.1 AVRs do 2.1 spendidly if you tell them that there are only fronts and a sub.

This is the best advice in this thread. You will have an uncomplicated set-up that will work perfectly.

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post #6 of 10 Old 01-11-2013, 09:37 AM - Thread Starter
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Thanks for the great suggestions and also for the manual link. The front pages of the manual say the crossover is 12dB/octave, but the back page says 6dB/octave. WTF.
Quote:
Originally Posted by arnyk View Post

Get an 5.1 AVR with bass management which implies a line level output for the sub. You can get such a thing for about half the price of the sub, so view it as protecting your investment in the sub.

This seems like the way to go as soon as I have a few bucks to spare.

But in the meantime I think another wiring setup might be worth a try. The sub, on the back panel has speaker level ins and outs. When you use those, it runs the speaker signal through both a highpass (for the signal returning to the speakers) and a lowpass (for the signal to the sub) filter. The overlap I set up didn't seem to cause any problems, don't forget that even without a crossover the speakers drop off dramatically below 80Hz, so all we really need to do is make sure that the sub is not trying to make bass above 80 Hz. I didn't use an SPL meter, but I used test tones at 10 Hz intervals to get my crossovers where they are now. I didn't set the phase. I will do that when I rewire.

Now, on to the immediate (and free) fix. commsysman susggests I wire the speakers and sub in series. My amp also has two speaker outs. I could run one set of wires from amp to speakers and another from amp to sub. Based on the fact that the amp manual recommends 8Ohm minimum load when running two sets of speakers (4 otherwise) I deduce that using both sets is actually wiring them in parallel. I also assume that the sub, since it is active, probably presents very high impedance. If we assume infinite impedance, it means the other speakers and the amp see no difference in signal at all. Of course that's just theoretical. But anyway, I'm naturally inclined to trust parallel rather than series wiring.

What's the effective difference between series and parallel in this case?
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post #7 of 10 Old 01-21-2013, 06:11 PM - Thread Starter
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Nothing on the series vs parallel issue?
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post #8 of 10 Old 01-22-2013, 08:12 AM
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THe sub's input impedance, for the sub 's own crossover/amp, is going to be in the range of 1000 ohms so you are not creating an issue for the amp either way. Other than eliminating the high pass for the left and right speakers, there's really no difference between the two approaches. Both put the speakers in parallel with the sub.
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post #9 of 10 Old 01-25-2013, 06:58 AM - Thread Starter
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That helped enormously, even without tuning with an SPL meter. The midrange is clean and clear again. I lowered the LP on the sub to 80hz. Sounds great. Plus now it has the advantage of still sounding right when the sub is off. With the old setup the HP filter was always in effect, even with the sub off. Thanks! smile.gif
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post #10 of 10 Old 01-25-2013, 07:51 AM
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The passive crossover in the sub was likely wreaking havoc on the signal going to your mains. Good that you have now bypassed it. Play with sub crossover point and level setting to squeeze out as much as possible, but this is likely the best you'll get until you can afford a new avr with modern bass management as arny suggests.

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