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MisterVego

Jubes / 1502 No Bass below 30hz

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Posted (edited)

Hoping the experts can lend a hand with figuring out an issue i'm having with the 2.1 rig.

 

Here's the issue.   When running a full frequency sweep at listening position, i'm getting a steep drop-off at 30hz.

I know this subwoofer can go lower than this so not sure if its a setup issue, positioning issue or what.

 

Some basics:

Room Dimensions:

20' x 14' x 9'

 

Jubes currently positioned on the front short wall with the 1502 sub seated behind me...   My listening position is 89" from the back wall which is about 60.5 " from the face of the subwoofer.

 

System is being run with a McIntosh Preamp > Xilica > System amps..    The sub is being run with a Crown XLS-2502.

 

I'm running the Jubes full range with the 1502 crossing at 50hz.

 

Attached is a pic of a recent sweep from my listening position.

 

Thanks for the help.

 

Erik

sweep.jpg

Edited by MisterVego

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Just for clarification "Jubes full range" do you mean no hi pass filter at 50 Hz where the 1502 should be taking over? Looks like you have some output below 30HZ, its just dropping off. I think you need @Chris A. BTW I wish I had your problem:)

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I don't know but it almost looks like the sub is not even on.

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You can try something like this--which is for an 1802 centered between Jubs on the front wall (and adjusting the subwoofer channel gain to match the Jubs after getting its frequency response under control):

 

1962902423_KPT-1802-HLSEQXilica.JPG.c359b486ff704b1a08bdc5669b712131.JPG

 

I realize that this is pretty extensive attenuation, but it was necessary in order to get sub-30 Hz output out of the 1802 and also to curtail its overwhelming output above 50 Hz which just isn't needed with Jub bass bins (in fact, anything above ~40 Hz isn't really needed).  The KPT-1802-HLS is a -3 dB at 26 Hz subwoofer (in half space).  I'd imagine that the 1502 closely follows suit in that area.

 

I'd also try to find a way to move the mouths of the 1502 closer to a room corner in order to get more sub-30 Hz extension.  You might not physically have any room for it, but that is the real solution.

 

Chris

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Hey Erik

 

Run a sweep with the sub and Jubs. Then mute the sub and run the sweep again and let’s see how they compare. 

 

Also when  looking at the current plot you posted it looks to me that you show a solid 25hz. Have you run 1/3rd octave pink noise or warble tones and if so how does it actually sound regardless of in room measurements..?

 

Are you running the sub through the xilica and if so do you also have a HI-Pass activated in the xilica on the sub and if so what are the parameters ..?

 

Are you using the XLS 2502 just as an amp or are you using DSP function also?

 

miketn

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Your magnitude plots look good. There's probably not any bass below 30 Hz. in the choice of music that caused your original post.

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Posted (edited)

update with some tweaking > ive also attached the PEQ's and level increases needed to get to this point.

 

Seems like alot of boosting...  Is this okay to do, or am i sitting in a huge null point?

Final Tweak.jpg

Final Tweak 2.jpg

PEQ.jpg

Edited by MisterVego
correction

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15 hours ago, mikebse2a3 said:

Hey Erik

 

Run a sweep with the sub and Jubs. Then mute the sub and run the sweep again and let’s see how they compare. 

 

Also when  looking at the current plot you posted it looks to me that you show a solid 25hz. Have you run 1/3rd octave pink noise or warble tones and if so how does it actually sound regardless of in room measurements..?

 

Are you running the sub through the xilica and if so do you also have a HI-Pass activated in the xilica on the sub and if so what are the parameters ..?

 

Are you using the XLS 2502 just as an amp or are you using DSP function also?

 

miketn

Mike,

I have yet to run any 1/3rd Oct PN or warble tones yet....  I can try that.

Sub is running through the Xilica and it does NOT have a high pass activated.

I am using the XLS 2502 as an amp only.   NO DSP functions are activated, just running in Bridged mode.

 

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12 hours ago, MisterVego said:

update with some tweaking

Final Tweak.jpg

Final Tweak 2.jpg

 

How does this tweaking sound Erik compared to the previous setup?

 

I assume you added a PEQ around 22 Hz with a fairly sharp Q....?

 

Looking at your previous plots you might play with the delay on the sub to see if the crossover transition region around 43hz can be smoothed out some without causing an issue above or below that point.

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26 minutes ago, MisterVego said:

Mike,

I have yet to run any 1/3rd Oct PN or warble tones yet....  I can try that.

Sub is running through the Xilica and it does NOT have a high pass activated.

I am using the XLS 2502 as an amp only.   NO DSP functions are activated, just running in Bridged mode.

 

 

The reason I strongly suggest you run those test tones is to use them as a reference since their level is a know quantity.  The issue with using recordings to make level adjustments is the large variation they have and you basically can fall into a trap of your adjustment serving more as a tone control which isn’t bad in itself if you can find a happy medium. 

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Just remember that a 1/4 wavelength (90 degrees) at 40 Hz, room temperature,  is 7 feet, i.e., 6.25 ms.  So the summing of the sub/Jub bass bin at the crossover point is pretty insensitive to changes in delay values.  I'd go in steps of 3--6 ms to see changes in frequency response at 40 Hz.

 

By the way, you're going to see a fair amount of harmonic distortion growth below 30 Hz if the sub behaves like the 1802.  It seems as if the real contribution of the 1502 or 1802 is their placement mid-wall such that it's filling up the mid-wall room modes with about the same bass extension as the Jub bass bins. 

 

Chris

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20 minutes ago, mikebse2a3 said:

 

How does this tweaking sound Erik compared to the previous setup?

 

I assume you added a PEQ around 22 Hz with a fairly sharp Q....?

 

Looking at your previous plots you might play with the delay on the sub to see if the crossover transition region around 43hz can be smoothed out some without causing an issue above or below that point.

Mike,   

I did a test with some music that contained some deep notes..   Things sounded more pronounced where in the past the notes were faint.

 

Below are the PEQ's needed to smooth the response down to 20hz.  but as you can see quite a bit of boosting was needed with the PEQ's AND with the output gain to get to the output level to match the jubes.

 

Not sure if this is a good thing or a bad thing.   During my brief tests last night, i was able to get things pretty loud in the room and did not pick up any clipping or distortion.

PEQ.jpg

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Posted (edited)
2 hours ago, Chris A said:

Just remember that a 1/4 wavelength (90 degrees) at 40 Hz, room temperature,  is 7 feet, i.e., 6.25 ms.  So the summing of the sub/Jub bass bin at the crossover point is pretty insensitive to changes in delay values.  I'd go in steps of 3--6 ms to see changes in frequency response at 40 Hz.

 

By the way, you're going to see a fair amount of harmonic distortion growth below 30 Hz if the sub behaves like the 1802.  It seems as if the real contribution of the 1502 or 1802 is their placement mid-wall such that it's filling up the mid-wall room modes with about the same bass extension as the Jub bass bins. 

 

Chris

Chris,

I'll try playing with the delay again.

 

I set my current delay by playing a 50hz ( my xover freq) tone and  separately matched levels of the jubes and the sub.

I then reversed polarity of the sub and then played both the jubes and subs together increasing delay until the overall SPL was the lowest.  Once done a changed the subpolarity back to normal.

 

Perhaps there is a better way to adjust this?  

Edited by MisterVego

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Not really--in my experience.  Subs are fairly insensitive to anything but polarity reversals, and that's probably the best way to find the right delays, by polarity reversal. After inverting the polarity of one or the other, adjust the delay while listening for the greatest attenuation at the crossover center frequency between the Jub bass bins and the 1502--while sitting near the listening position(s). 

 

Chris

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17 hours ago, MisterVego said:

Seems like alot of boosting...  Is this okay to do, or am i sitting in a huge null point?

 

Some homes have that condition where the deep bass is strong in the rear upper corners of the room, but weak at the listening position. 

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5 hours ago, mikebse2a3 said:

The reason I strongly suggest you run those test tones is to use them as a reference since their level is a know quantity.  

Good point, much better than music which can all over the place when trying to measure something.

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12 minutes ago, dtel said:

Good point, much better than music which can all over the place when trying to measure something.

@mikebse2a3 & @dtel i would have to agree to, however I have been using frequency sweeps from 0-20khz to take my measurements not music.

Is this okay to do?

 

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Of course you should use test tones for tests.:) I think using music for tests will only yield what Sir Duke said " if it sounds good it is good".

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56 minutes ago, MisterVego said:

@mikebse2a3 & @dtel i would have to agree to, however I have been using frequency sweeps from 0-20khz to take my measurements not music.

Is this okay to do?

 

 

Yes for measurements.

 

The reason I’m suggesting 1/3rd pink and or 1/3 warble tones is for you to learn how it actually sounds to you with a consistent reference level that music recordings can’t really supply.  

 

Does the 20hz region sound consistent in level as you move around the room or are there significant peaks and valleys of SPL. If pretty consistent in level as you move around the room and otherwise assuming the sub is working as designed then I would suspect room leakage which would be expected in the 20hz region in most typical listening rooms IMO. If that’s the case just EQ accordingly as long as the sub has plenty of max SPL headroom as the 1502 certainly does. 

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