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Is this how a Subwoofer Crossover is supposed to work?

I bought two Starke SW12 subwoofers that I installed.  So far I'm not particularly happy with them.  They are way too loud even with the volume set almost to off.  More importantly, I'm having trouble integrating them into my system and I'm wondering if that is because their crossover setting is really functioning as I understand a crossover should. Attached please find measurements from Room Equalization Wizard with SPL graphs of the two subs (no speakers) taken at my listening position with the crossover set at 50 Hz, 90 Hz, and 130 Hz. Ignore the peaks and dips which I assume are due to room nodes.  All of those settings appear to actually have the same crossover point of 50 Hz. All that changes is the slope of the rolloff in sound levels. This isn't how I thought a properly designed crossover was supposed to work.  I thought the frequency the levels would start to roll off would change, i.e. flat to 50 hz then a sharp drop, flat to 90 hz then a sharp drop, etc. etc..  But Starke says this is how a subwoofer crossover is supposed to work.

https://www.dropbox.com/s/8x4cr32pagwg48i/Two%20Subs%20Different%20Crossover%20Points%20No%20Speaker...
Any experts on here with an opinion about this?  Is it possible to buy an inexpensive active crossover that I could use in place of what is built into these subs?
pinwa
pinwa OP
238 posts
 
kenjit "Why would anybody design an electronic lowpass filter with a variable slope and a fixed crossover point? Thats useless. What you want is a variable crossover point and fixed slope." 

That is what I thought also and that is what started this whole thread.  But Starke says the subwoofer is designed properly.  And I haven't been able to find any charts that show how other subwoofers respond with changes in the crossover.

Surely some enterprising soul on Audiogon has performed similar measurements on their sub and can post them or knows of a source showing how a "quality" subwoofer works?
erik_squires
15,877 posts
 
You can make anti-modes, or dips controllable with bass traps like GIK Soffit traps, however as Duke would surely advocate, the point of the 2 subs is that the second sub should fill in the big dips, and it doesn't seem like it's happening.  This usually requires non-symmetrical placement.

I suggest you plug your main speaker ports, and re-measure. See if that helps control the peak at ~38 Hz.

Not sure how REW works, but if you are using Roon what I normally do is rip my test signals to my music library, and play the test signals in Roon. This allows me to adjust the Roon PEQ’s accurately.

All of this however is made much harder due to not having a good crossover in place already. This feels like using gum and duct tape and I really think the miniDSP on your sub, plus plugging your mains is your way to glory. Everything else is merely better than before.

pinwa OP
238 posts
 
erik_squires  How would you plug the speaker ports?  There are two of them, each about 4 1/4" in diameter.  The peak at 36 Hz is easy to tame with the parametric equalizer in Roon.  No real need for a miniDSP for that.  But the holes at 61, 77, and 99 Hz are too high for the subs to do much to.  The speakers are in my main living space so I'm limited as to what I can do with bass traps or positioning.  But the truth is the system sounds great. Could it sound better with more treatment?  Probably, but there are limits to what I can and would want to do

There is some trick with REW to measure a signal that REW isn't generating, i.e. played through Roon,  but I haven't figured it out yet..
erik_squires
15,877 posts
 
erik_squires How would you plug the speaker ports? There are two of them, each about 4 1/4" in diameter.

An old clean T-shirt will work. :)  Just make sure you can pull them out.  This will reduce the main bass, but also reduce cone excursion. Will let the subs work with less interference.

But the holes at 61, 77, and 99 Hz are too high for the subs to do much to.


Au contraire, mon ami!!

Look at your sub's output.  You have plenty of output at 80 Hz for sure. And here we get into, gee, if your crossover was working really well, you'd have a 4th order low pass at 80, 2nd high at 80, and you'd be able to get your two subs to provide overlapping coverage.

Come on @audiokinesis, back me up here.  :) 


The peak at 36 Hz is easy to tame with the parametric equalizer in Roon. No real need for a miniDSP for that.

Yeah, I guess you could fix this peak with Roon, and it will sound good, but honestly it rubs me the wrong way. :) This may very well be snobbery on my part, but I like to equalize the individual components separately, then gently cozy them up to each other until they are spliced together as smoothly as a Han dynasty curved back chair.  Using major global EQ often tells me I've messed something up in a speaker configuration.

I recently did integrate my subwoofer with my speakers, but it seems I threw away most of the charts.  Still, you may find this post I wrote useful.  What you are doing is much of the same:

https://speakermakersjourney.blogspot.com/2016/12/crossover-basics-driver-response.html


Best,

E
audiokinesis
2,724 posts
 
Pinwa, in the spirit of plowing with the horses you’ve got, I like Erik’s idea of plugging the port(s) on the mains and then overlapping the mains and subs. If the Moabs have multiple ports, you might leave one open.

This might work as a plug: https://www.zoro.com/test-tite-t-cone-combination-cleanout-test-plug-4-86400/i/G3337302/

Its maximum diameter is less than 4 1/4" but you could expand it to the maximum and then wrap the perimeter with duct tape until it fits snug. To remove the installed plug, unscrew the orange piece to relieve the expansion pressure and it should come out easily.

But try Erik’s T-shirt suggestion before ordering the plugs because a rolled-up T-shirt will work just fine.

The Moabs will still be low-bass sources even after port pluggage, but not as loud. So now you can turn up the subs a bit louder. And you can use different crossover settings on each of the two subs to smoothe the blend. I’m under the impression that repositioning the subs is not practical, but I glanced at the specs and apparently they have phase controls. Use them, and they can have dissimilar settings and still work well.

Duke
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