# Help with crossover between sub and front speakers



## sdy101 (Feb 22, 2014)

I have corner-located HSU STF-2 subwoofer with a 10" down-firing driver that is rated at 25-100 Hz (+/- 3dB). I also have Definitive Technology PM1000 satellite front speakers (5-1/4" driver with 1" tweeter) in a family room that approx. 16'W x 15'L x 9'H (but is the room open in the back behind the MLP to the kitchen area which is another 16'W x 15'L).

Below is a measurement of my frequency response at the MLP. I am trying to optimize the crossover point between the sub and front speakers. I used the V-Aux input on my Denon receiver with Audyssey MultEQ off. The Denon set the crossover for the front speakers at 100 Hz when I initially ran Audyssey. I overlayed the sub only response (at 100 Hz crossover set by Denon) with the response of the front-right speaker only with the Denon crossover set at 40, 80, and 100 Hz (red, black, and blue curves respectively). The sub is connected to the Denon using the RCA sub out connection. The sub's crossover has been defeated.









It looks like my STF-2 sub is drastically falling off on the upper end after the peak at 70 Hz (more than 10 dB down at 100 Hz). Is this due to room modes or an inefficiency of the subwoofer? Would setting the subwoofer to LFE+Main do anything? Any advise of what the best crossover frequency should be? Thanks!!


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## tonyvdb (Sep 5, 2007)

Your STF-2 does not go any higher than 90Hz according to the data I found on the HSU site. There seems to be no way to bypass the Crossover setting on the sub. You will have to lower the crossover on the mains and find the best fit.


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## willis7469 (Jan 31, 2014)

Do you have any room to experiment with placement? I would try to cross those st 80-100hz. My hunch is that the 70hz peak is a mode issue. If you have any way to knock that down, I think you'll find a smoother transition to the mains. How does it sound to your ears? Do you notice the transition with material?


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## sdy101 (Feb 22, 2014)

tonyvdb said:


> Your STF-2 does not go any higher than 90Hz according to the data I found on the HSU site. There seems to be no way to bypass the Crossover setting on the sub. You will have to lower the crossover on the mains and find the best fit.


The STF-2's internal crossover does not go any higher than 90 Hz, but the spec on the HSU website says the frequency response should be 25 to 100 Hz (+/- 2dB); I assume this is in a non-reverberant environment. Even with a room mode at 70 Hz, I guess I didn't expect the sub to drop 20+ dB from 70 to 95 Hz, right around the crossover point for my mains. Maybe I have a huge null at 90ish Hz that isn't helping....


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## sdy101 (Feb 22, 2014)

willis7469 said:


> Do you have any room to experiment with placement? I would try to cross those st 80-100hz. My hunch is that the 70hz peak is a mode issue. If you have any way to knock that down, I think you'll find a smoother transition to the mains. How does it sound to your ears? Do you notice the transition with material?


I actually recently moved the sub from the front-left corner to the front-right corner of the room. This was based on the REW measurements that showed a huge null at 35 Hz when in the front-left corner. Also the peak at 70 Hz was even higher in the front-left corner. 

Unfortunately along the front wall is my only option for sub placement. If I move the sub under the front or right main speakers (about 3 ft in from the corners), the responses looks very similar to their respective corner responses.

When I measure the sub FR with one of the front speakers, it doesn't look as bad, and Audyssey seems to help improve the crossover area even more. I just wasn't expecting such a drop in output level from the sub in the 80-100 Hz region based on the spec. I do not have any PEQ equipment for the sub.

I feel there is a noticeable transition between the sub and front speakers. My center speaker has two 5-1/4" drivers with a 1" tweeter, I wonder if putting it in the place of one of the main L/R speakers would help fill the gap more around 80-100 Hz with a higher output level and lower crossover setting (maybe 80 vs 100 Hz)? Or maybe a second subwoofer in the opposing front corner would help the high end....


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## willis7469 (Jan 31, 2014)

sdy101 said:


> I actually recently moved the sub from the front-left corner to the front-right corner of the room. This was based on the REW measurements that showed a huge null at 35 Hz when in the front-left corner. Also the peak at 70 Hz was even higher in the front-left corner. Unfortunately along the front wall is my only option for sub placement. If I move the sub under the front or right main speakers (about 3 ft in from the corners), the responses looks very similar to their respective corner responses. When I measure the sub FR with one of the front speakers, it doesn't look as bad, and Audyssey seems to help improve the crossover area even more. I just wasn't expecting such a drop in output level from the sub in the 80-100 Hz region based on the spec. I do not have any PEQ equipment for the sub. I feel there is a noticeable transition between the sub and front speakers. My center speaker has two 5-1/4" drivers with a 1" tweeter, I wonder if putting it in the place of one of the main L/R speakers would help fill the gap more around 80-100 Hz with a higher output level and lower crossover setting (maybe 80 vs 100 Hz)? Or maybe a second subwoofer in the opposing front corner would help the high end....


well, I do know first hand that a 2nd sub can help smooth out the in room response. Do you have a chart with the mains and sub? A collective graph might be a better representation of what you see at the MLP. Have you experimented with phase? That was a good fix for one of my issues. As far as moving the center, it might work as an experiment, but I would guess that even though it has the same sized drivers, due to cabinet size, and most likely a different crossover, the information won't be valuable. I also think that most sub crossovers start to roll off before the crossover point, as opposed to playing flat up to 100hz, it start to roll off at around 70. Or if it's set to 80hz, it will start to roll at 50hz, etc. Also, your main speakers location to the walls might be responsible, because even though you changed the crossover, they might be fighting their location for extension. I'd start with phase, and look at the graphs as a whole. ...sorry for the broken, windy response. I'm trying to multitask. Lol


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## sdy101 (Feb 22, 2014)

All good suggestions, thank you for your response. I didn't think about what the AVR might be doing to roll-off the sub response before reaching the set crossover at 100 Hz, good point! I figured maybe 100 Hz would be the 3-dB down point at most.

My L/R main speakers are mounted on the walls about 2 ft from the ceiling and 3 feet from the side walls. They have a planar pressure-coupled mid/bass radiators on their tops (which supposedly works with the front drivers for reinforcement of the mid-range/bass).

Although I did not take a measurement with the mains and sub this time around, below is a measurement I made several weeks ago when determining the optimal sub phase after moving it to its current position. However, this older measurement was taken before I reran Audyssey MultEQ which moved my crossover up from 80 Hz to 100 Hz. Now I want to go back and run RTA with Pink Noise to make sure the phase is set properly at the new crossover.

I don't know, maybe my initial curve with the sub and mains separately just has me chasing or worrying about something that really isn't a problem....


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## willis7469 (Jan 31, 2014)

sdy101 said:


> All good suggestions, thank you for your response. I didn't think about what the AVR might be doing to roll-off the sub response before reaching the set crossover at 100 Hz, good point! I figured maybe 100 Hz would be the 3-dB down point at most. My L/R main speakers are mounted on the walls about 2 ft from the ceiling and 3 feet from the side walls. They have a planar pressure-coupled mid/bass radiators on their tops (which supposedly works with the front drivers for reinforcement of the mid-range/bass). Although I did not take a measurement with the mains and sub this time around, below is a measurement I made several weeks ago when determining the optimal sub phase after moving it to its current position. However, this older measurement was taken before I reran Audyssey MultEQ which moved my crossover up from 80 Hz to 100 Hz. Now I want to go back and run RTA with Pink Noise to make sure the phase is set properly at the new crossover. I don't know, maybe my initial curve with the sub and mains separately just has me chasing or worrying about something that really isn't a problem....


I just hope you can find some of my observations useful! I would say that goin 180 helped in the (loosely) 70-110hz range, without changing much else. That's a plus! In my mind it seems that the information from running REW sweeps with all speakers would be more like what you'd see with media too. I have a null at my MLP, and I (like you possibly lol) was focused mostly on my subs (2) contributions. Then the epiphany! ...I listen to them all together. That's obviously not to say individual graphs don't matter. Only that it's a bigger picture thing, and I think when you plot the whole system, you'll be looking more closely at the target. I just wish I could get more than 45 min at a time to put my time into it! Please post your future findings. I'd really like to see your progress!
Will


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