60 or 80 Xover

[moreira85]

Here is the response for EQ'd SVS in pink without mains.
My current Xover is set at 80. Based on what we are looking at here should I drop the Xover to 60? Mains are VR3s.

 

[MDS]

What do the specs say is the low extension point? The graph looks like it starts to really drop off around 60 Hz, so I assume that is why you might want to use 60 Hz for the xover.

Remember though that the xover has a slope and does not cut off exactly at the chosen frequency. The general rule of thumb is 1/2 to 1 octave above the -3 dB point of the speaker. If the -3 dB point of the speaker is indeed around 60 hz, then 80 Hz would likely still be the best xover (it's a tad less than 1/2 octave away).

Still...try it and see if you notice a difference you like.

 

[moreira85]

Help Understanding

So I am trying to understand the crossover. I originally had it set to 80. Like I said when I measured the FR for the sub only it looks as if it starts to dip around 60HZ. I then figured I would drop my crossover down to 60HZ so that my mains could play down to 60 Hz. Here is what I found: As I drop my crossover down to 60 and even 40hz I get less bass that is being playied. As I increase my crossover to say 160 HZ I get more bass playing????
I thought that by dropping it down to 60Hz that the mains would play all the way down to 60Hz and the sub would play below 60Hz.
Am I looking at this the wrong way?
Either way it sounded better at 80 than 60.
Why am I getting more bass at 160hz?

 

[Warpdrv]

I would set your xover at 100hz and see how that works for you, but also you need to lower the gain on your sub, right now its 15db high compared to your mains if your looking to achieve a flat response...

Then you should see what the response looks like when your flat with the mains. From there you should approach EQ to get it as flat as possible. Then after that, adjust your gain to where you feel most comfortable, if its +10db, so be it, what ever makes your experience the best for you... Its all personal pref....

Keep in mind that the LFE channel supports material that runs up to 120hz.

I cross my subs at 120hz for the one behind the mains, 80hz for the two left and right of the LP and 60hz for the rear, but having 4 subs reduces localization to nothing...

Give the 100hz a shot and then take some measurements, should be not too bad for localization with a single sub... EQ to flat...

 

[MDS]

The crossover has a slope and is typically very steep like 24 dB/Octave. An Octave is a doubling or halving of frequency so for example 40 Hz is one octave below 80 Hz and 160 Hz is one octave above 80 Hz.

The crossover will start attenuating the signal around one octave above its setting so that frequencies right around the crossover point will be roughly unchanged. So with a xover of 80 Hz the sub will still see some content between 80 Hz and 160 Hz but it will be greatly attenuated.

So if the xover is set very high, like 160 Hz, it's seeing frequencies as high as 320 Hz (although greatly attenuated) and that is well into the range of human voice and can result in your ability to 'localize' the bass; ie know where it is coming from instead of it just sounding like it is everywhere.

It may sound like there is more bass with a higher crossover because of the distribution of frequencies in audio, meaning there will be more content at those higher frequencies than at the lower frequencies. You're sending the sub more 'mid-bass' and there is more mid-bass than low bass, but that is not the content you want the sub to play. With the lower xover, the sub is only playing what it should be playing - the low bass that the other speakers can't reproduce well.

 

[Warpdrv]

The thing is, you sub is more proficient at producing those upper bass freq's then your speakers, and its far more noticeable to you because you have the sub 15db's higher then your speakers are outputting that same freq, so yes your going to notice at a higher xover that the bass or upper bass seems more powerful.....

 

[sholling]

What do the specs say is the low extension point? The graph looks like it starts to really drop off around 60 Hz, so I assume that is why you might want to use 60 Hz for the xover.

Remember though that the xover has a slope and does not cut off exactly at the chosen frequency. The general rule of thumb is 1/2 to 1 octave above the -3 dB point of the speaker. If the -3 dB point of the speaker is indeed around 60 hz, then 80 Hz would likely still be the best xover (it's a tad less than 1/2 octave away).

Per the manual the frequency response of the VR3 is 41Hz-20kHz ±3db. If memory serves they are -6db at 35hz. Assuming that Boston is as good as their word the only reason to crossover over above 50hz is to ease the load on the receiver, however with a sensitivity rating of 92db it's not much of a load on the receiver. The dual 7" woofers play deep with authority. I would turn off the sub and play with speaker placement. The VR3s are rear ported and distance from the wall is going to play a big roll in bass. Only after you have the speakers dialed in would I bring the subwoofer into the equation, cross it over at 50 or 60hz and then level match.

 

[moreira85]

The thing is, you sub is more proficient at producing those upper bass freq's then your speakers, and its far more noticeable to you because you have the sub 15db's higher then your speakers are outputting that same freq, so yes your going to notice at a higher xover that the bass or upper bass seems more powerful.....

How do you know my sub is 15 db higher than mains? I leveled all with sports.

 

[sholling]

I leveled all with sports.

Please explain.

 

[moreira85]

Please explain.

woops, sorry meant I matched them with SPL meter.

 

[sholling]

woops, sorry meant I matched them with SPL meter.

The graph makes it look like the sub is running way hot. Again I'd 1) get the speakers dialed in (placement) without the sub. They make great gobs of bass down to ~40hz. Play with placement 18-24" from the wall behind them and make sure they aren't tight into a corner. 2) set the crossover to 60hz, and 3) the using the meter lower the sub's volume level to equal the mains. Is your meter set to A or C weighting?

 

[moreira85]

The graph makes it look like the sub is running way hot. Again I'd 1) get the speakers dialed in (placement) without the sub. 2) set the crossover to 60hz, and 3) lower the sub's volume level to equal the mains.

Thanks for all the input.
Sub is set to 2 db higher than the mains. Can someone just walk me through how the graph makes it look like sub is running way hot?

 

[sholling]

Thanks for all the input.
Sub is set to 2 db higher than the mains. Can someone just walk me through how the graph makes it look like sub is running way hot?

On your meter are you using A or C weighting?

 

[sholling]

Can someone just walk me through how the graph makes it look like sub is running way hot?

Everything to the left of the 80hz crossover point get's progressively louder until it flattens out at the end of the crossover slope.

 

[Warpdrv]

On your meter are you using A or C weighting?

+1

Agreed, what is the meter you are using set to...

A weighting or C weighting.... ?

 

[moreira85]

Rat shack C weighting. I will try measurements crossed at 100. Keep in mind the measurements I posted are sub only. I never graphed n plotted the mains.

 

[Warpdrv]

Look at your graphs....

You entered those measurement points manually into that program.

Your inputs at 20hz are 85db all the way up to 40hz, and it starts diving downward until you get to about 80hz where your input is roughly 70db......

Thats a 15db difference in measurements...

 

[sholling]

Rat shack C weighting. I will try measurements crossed at 100. Keep in mind the measurements I posted are sub only. I never graphed n plotted the mains.

Now it's starting to make sense. You're seeing the crossover transition from the sub to where the mains should be taking over - but you have them off. Set for crossover for 60hz and plot with the mains and sub.

 

[Warpdrv]

Rat shack C weighting. I will try measurements crossed at 100. Keep in mind the measurements I posted are sub only. I never graphed n plotted the mains.

Ahhh.... yes - thats the reason...



Otherwise it looks pretty good...

 

[moreira85]

Now it's starting to make sense. You're seeing the crossover transition from the sub to where the mains should be taking over - but you have them off. Set for crossover for 60hz and plot with the mains and sub.

correct! The mains are off. We should be focusing on the pink line. The pink is the sub EQ'd. Blue is not EQ'd. I will measure at 60 80 90 100 crossed with mains n sub on n report back? Is that correct