Is this how a Subwoofer Crossover is supposed to work?

This is how a good subwoofer low pass crossover supposed to be. However, the quality of the driver is one of the key element...

https://downloads.monoprice.com/files/images/35141_10.jpg

Amazon had this:

https://www.amazon.com/Oatey-33403-Plastic-Galvanized-4-Inch/dp/B000H5T1PI

Cheap and it comes by Monday.  More stuff to play with LOL.

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

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

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..

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.

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?

That is how adjustable sub crossovers should work, except for the volume problem.

hogwash. 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. Even better would be both variable. 

Yes! That i show adjustable sub crossovers should work, except for the volume problem.

Again, thanks to those of you that are providing constructive input.

1) I've put the system back together, moving one sub to a different location and setting phase and crossover frequencies individually for each sub.  I am still using the DAC to provide fine tuning of volume with it connected by XLR inputs to the subs and by RCA to the tube amp, but now that I have a better understanding of what is going on the volume on the tube amp is set higher and the volume on the DAC is lower which helps offset the 7 dB gain of the XLR inputs vs RCA.  You can see a chart here. NOTE this was measured before adjusting Amp volume up and DAC volume down so the low end bass response isn't actually exaggerated in the system.

https://www.dropbox.com/s/j5a418zmk99zqbu/Moabs%20with%20Starke%20Subs%20Green%2C%20without%20Orange...

Adding the subs provides significant low end extension and a slightly smoother response.  I have significant room nodes at 61, 77, and 99 Hz with steep 10-15 dB valleys that I'm not sure what to do about.  The subs don't help with that and moving the Moabs around hasn't done much either.  I don't hear them so that is good.  Any suggestions about smoothing those room nodes?  I've tried a couple of rockwool panels without much impact.

2) Active crossovers or DSP all seem like good suggestions but things that I would explore at a later time.  I do use the EQ in Roon to adjust for some things but I haven't figured out how to use REW to measure the changes Roon makes.

3) My assumption has been using the DAC to control volume is fine and that there is no change in signal quality with volume set at 100 vs 60. Anybody have any idea if that is true?

4)  mijostyn's idea of subwoofer placement on either side of the speakers is interesting but, as many people do, I have my tube amp right in the middle.  It is on springs and isolation pads etc. etc. but it seems risky to have a tube amp in between, and close to, subwoofers.  Thoughts?

In conclusion, mostly I've roundtripped to where I started.  The system sounds great, the subwoofers extend the bass and increase low end impact without sounding exaggerated or noticeable.  At some point in the future I may explore active crossovers or DSP but not now.  I would still love to see measurements for how changing the crossover frequency works on a Rel or other high end subwoofer.

I could be wrong, but it looks like you are running 2 subs in parallel with 2 mains (ie, mains are full-signal; subs are supposedly filtered out above the crossover frequency).

If I'm correct, the single most assured/competent resolution would be a good electronic crossover. I use the Marchand XM66 with variable crossover frequency. Slopes on the high- and low-pass crossovers are 24 dB/octave and the crossover "hump" (overlap) can be precisely dialed in. This is a very transparent, analog means to take a single RCA/single-ended input (from preamp) and split it into 2 output RCA pairs, one going to the subs (L goes to one powered sub, R goes to the other powered); and the other going to the amplifier that drives the main speakers.

It totally works. 

I’ve spent the last several weeks attempting to integrate 3 separate subwoofers into my listen room along with my Moab speakers. From what I understand, an external crossover unit like the JL Audio CR-1 is essential to getting accurate time alignment between subs and main speakers. This essentially is a two system where everything above 90hz, for example, goes to the main speakers, and everything below 90hz is handled exclusively by sub(s). I don’t have such a unit and simply used several practical techniques to blend subs as well I could with my Moabs. If I can add anything to this thread it’s that integrating multiple subs can be extremely beneficial. And yes adding subs with the Moab has dramatically improved my low frequency room response, bass depth, sharpness and overall system accuracy. All the best. 

Happy New Year to all.

If you are using line level input try using speaker level input if it is available on your subs.

1. At the top your list must be to deploy a single solution to control system volume you’ve been presented w/one or more to date. 

2. Either
  a. replace your existing subs or
  b. find an external XO* w/some DSP to aid in room integration 
*DBX Drive Rack PA 3 - way or PX - 2 way

I realize I committed a sin suggesting DSP in this system. I’m sure others will have better ideas. 
The “admission $”, used, is insignificant compared to what you have spent so far. If my solution sets you back instead of move you forward, you’ll have little trouble selling it.  
BTW I use 3 DRPAs and 1 DRPX to tri-amp 3/5 channels & integrate 4/5 subs into my 5.5 HT. From adding the first DRPA to the DRPX, my system moved forward every time. While your doin’ 2Ch VS HT & on a different level to boot, I’m satisfied for the moment... But that is for another day. 
Happy New Year and tweaking

Ahhh.  Of course, an XLR to RCA adapter generally does the same thing, but it also unbalances the line.

Pinwa, welcome to the contorted world of subwoofers. Audiokinesis  is very versed in this subject. I have been involved with subwoofers on a semi professional basis since 1978. 
You are quite correct, those are very bad crossover curves for what they were indicated to be. The peak at 70 Hz and the dip just above 30 Hz are room modes. Make believe they are not there. Duke is correct in that it is possible for voice coil induction to create this effect but I somehow do not think this is the problem. I've looked at a lot of woofer specs and I have never seen one roll off this low. My inclination would be to send them back as they do not meet spec. With the Moabs I would want a crossover somewhere around 80 Hz, the 3dB down point. These are obviously not going to make it up there. It is unusual to see a sub not going up. The problem is usually the sib going down! 
If you are a handy person you might want to take a look at the Sub kits offered by Dayton labs. They are really quite excellent and better performing than a lot of commercial subs.
Using a high pass filter on the main speakers is very important for two reasons. It increase the headroom of the system and lower distortion on several fronts. If the supplied cross over does not have one you can supply your own first order crossover just by putting the right value capacitor in series with the + input of you amp. The math is readily available on line. All you need to know are the crossover frequency you want to use and the input impedance of your amps. I did this for years.
Ideally what you want to do with two subs is place them between the Moabs right up against the wall. You place all the speakers and subs on a radius from the listening position so that they are all the same distance from your ears. Then as long as none of your equipment shifts phase you will be good to go. You might consider adding more subs in the future if you don't get enough thud. 
The best subwoofer management systems are digital. You might want to look at my system page and you can see this in action measurements and all. My unit is no longer available but there are similar units on the market By DEQX, Anthem, Trinnov and now McIntosh. The problem with computer run systems is that you have to have and control 4 channels of DAC simultaneously. Using two separate DACs creates issues.
Please feel free to contact me if you have issues.

Mike

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.

@ erik_squires, beside the +6dB of xlr connection I think the subwoofer amp has higher gain than the tube amp that OP set to. Another solution is set the volume control on the tube amp higher, but OP have to lower the volume control on the DAC it might degrade the sound quality.

I'm not understanding, why not use the gain on the sub to attenuate the output?

I wish they came in 5 or 7 db attenuation. -10 starts taking the problem in the other direction LOL.

10dB attenuation is not a problem at all, it give the volume control on the subwoofer more freedom for adjustment! 

Sell thoses beasts and get a stereo pair of REL 812's.  You will find they integrate seamlessly with your mains and the sound is superb.  I also own JL's.  They sound great after a few weeks of tuning the gain, crossover and room position  but not even close to the disappearing act of the REL's.  With the REL's you will forget there are subs and yo will think the drums and bass are right in front of you.

imhififan Interesting suggestion.  I wish they came in 5 or 7 db attenuation.  -10 starts taking the problem in the other direction LOL.

I need to do some further investigation about the pros and cons of a) leaving things as they are with the tube amp connected to the DAC’s RCA output and the Subs connected by XLR cables.

A pair of in-line xlr attenuator may help.
https://www.parts-express.com/Search.aspx?keyword=In-Line%20XLR%20Attenuator&sitesearch=true

Hi OP,
Really nice work on the main’s. Is this in a relatively narrow room? I ask from looking at the peak around 370 Hz.  Consider bass traps in the corners behind the mains. GIK Soffit Traps are super nice, but also look at ATS Acoustics for even less expensive options.

If I was a reactionary jerk I’d say something about @audiokinesis post, but since he’s being a super nice guy and 100% based in science I can’t. :0)

Imo the close-miced curve of the Starke provides a lot of useful information.

Which is why I was suggesting a single sub as a starting point, though honestly I did not think to do close mic’d, but at least we can see that this sub is in fact performing a lot better than the original plot. :)  Now as we start adding complications like distance and 2 subs we'll better understand what is contributing to what.


Best,
E

Sorry in advance for not answering the OP's question.

I just received my microphone and downloaded REW.  All this discussion is causing me to consider returning the mike.  In the meantime I repositioned my REL subs into the far left and right corners, allowing them to project the longest way possible, vs project right at me and a wall behind me. My room is open to the sides...think basement with center utility room.   I use the high level inputs and have the crossover and volume turned quite low.  Sounds great to me now with no EQ.  Still would love to measure it all but giving me a headache.

MySet Up:  one at a time.  Turn the xover and volume all the way down.  Turn up the volume till it just sounds good.  Now play with the phase (switch or dial) until loudest bass.  Then turn the xover up slowly by ear until it sounds best.  Try to keep it to where it just blends and you can not localize the sub.
Now do the second sub (I do it with and without the first playing).
Finally, listen to a lot of music and turn each subs volume down a smidge probably.  Works for me.  

OP, it is all good from now. Your signal for the Subs is important, but the super duper SQ won't be...  Ys or a simple passive preamp, with XLRs and  RCA's will take care of 10 of those thing (SUBS) if you want .
You will lose nothing in SQ.. 100hz and below.. You need good (control) dampening...for the bass or servos.. Either will help with overshoot and or distortion... 

Breaking in will help a LOT.. Give them 200 hour (with no ports) They will sound a lot better.. 100 hours with ports.. Set um fire.. that will loosen them up YUK YUK YUK.. No I'm kidding.. NO I'm NOT... Yes I am...

Excuse please, inner conflict going on...:-)

Happy new year, everyone...Enjoy... Hat on the floor....OLAY....

Regards

1) So I’m not an idiot. Of course I’m setting the volume of the amplifier at a fixed level that approximates my 75 dB listening level and fine tuning volumes with the DAC that then controls what both the amp and the subs see.

2) If I wanted to spend $2-4K on subwoofers I would have, so all the suggestions about buying "audiophile" quality subs will be respectfully ignored.

3) The bass response on the Moabs is great which is absolutely not the same thing as saying the system wouldn’t benefit from well integrated subs. Here is a chart of the Moabs with and without a very old Velodyne CHT10 subwoofer with a speaker level input. As you can see that sub improves the measurements of the system as well as improving how it sounds. I wanted to see if the Starke’s improved things further although so far I’m not sure that is true.

https://www.dropbox.com/s/bf83tvl57i9l0qw/Moab%20with%20and%20without%20Subwoofer%2050Hz%20Crossover...

That REW graph of the Moabs shows a lot of weird stuff in the response above 200 Hz and that was because the Moabs weren't well positioned in the room when that measurement was taken. Where I have the Moabs now the frequency response is +- 5 dB from 100 Hz to 10 KHz except for a little bump around 325 Hz that might be the crossover.
   
All comments about how subwoofers don’t belong in my system will be respectfully ignored.

4) I didn’t think about the fact that the Klipsch was ported so I guess I’ll reserve judgement. Not planning on using that sub with the Moabs anyhow so I will do no further investigation there. And I’m not going to mess around with the Moab’s ports.

5) I need to do some further investigation about the pros and cons of a) leaving things as they are with the tube amp connected to the DAC’s RCA output and the Subs connected by XLR cables. b) using an RCA Y Splitter to connect subs and amp to the same RCA input. c) Millercarbon’s suggestion to adapt subs to a speaker level input. d) when I bought the subs Starke said you could connect one sub to RCA and use the subs balanced out to connect the second sub with an XLR cable. That sounds weird but I may give it a try rather than having multiple Y splitters.

I will note that there doesn’t seem to be any difference in the curve in the subs response when you switch from RCA to Balanced inputs so it isn’t clear to me why so many of you seem to think it is imperative the subs and the amp use the same input as long as volume is controlled further upstream, i.e. at the DAC level.

6) miniDSP looks interesting and perhaps I’ll get one later but not something I want to play around with right now.

Thanks to all of you who are providing detailed constructive comments.

" Bingo! And I already provided the simple $2 solution to getting exactly that from his existing amp.

https://www.epanorama.net/circuits/speaker_to_line.html "   

Good call!!

Duke

The volume control that turns the sound to your speakers up and down must also be the one turning the sound to your subs up and down.

Bingo! And I already provided the simple $2 solution to getting exactly that from his existing amp.
https://www.epanorama.net/circuits/speaker_to_line.html

Hello Pinwa,

Imo the close-miced curve of the Starke provides a lot of useful information. Now you can tell what was room interaction and what was native to the subwoofer, and it is much easier to tell what the crossover is doing. Good job!!

I think the close-miced curve on the Klipsh is giving you an incomplete and therefore misleading picture. From that curve I’d assume it has a port or passive radiator tuned to about 26 Hz.

If so, getting a representative frequency response curve becomes vastly more complicated. You ALSO need to close-mic the port or passive radiator and SPLICE that curve with the woofer’s curve, adjusting for the relative RADIATING AREAS of the woofer cone and the port or passive radiator. You also have to take into account the relative phase rotation between the two and I don’t know how to do that math - I’d have to use a computer program.

In other words, close-micing ONLY the woofer of a vented box DOES NOT give a complete and accurate representation of what the system is doing.

I suggest simply assuming that the Klipsch is competently designed, rather than doing more measurements plus a ton of math.

Also, pay attention to what geared4life is telling you. If his analysis is correct (and I think it is), your system configuration is not allowing you to adjust the level of the subwoofers with the same volume control that you are using for your main speakers.

Duke

kenjit, I sincerely hope to meet you one day.

You can not send a fixed level signal from your dac to the subs while adjusting the speaker volume from your integrated amp and ever expect them to be at the proper level to blend.

yes you can. you just adjust the sub every time you adjust the volume. 

Pinwa, I will put this to you straight. You have a fundamental misunderstanding of how your system works and how to incorporate a subwoofer into it. You can take a million measurements but you will not achieve your goal with the way you are trying to set this up. The volume control that turns the sound to your speakers up and down must also be the one turning the sound to your subs up and down. You can not send a fixed level signal from your dac to the subs while adjusting the speaker volume from your integrated amp and ever expect them to be at the proper level to blend. Due to the kind of integrated amp you are using you have bought the wrong subwoofers.

Hi 8th-note

I have to take some issue with your statements, as I don't think they are in evidence yet:

2. You purchased two subwoofers which cost $350 each and weigh 40 lbs. to supplement the bass of a pair of full size, full range, highly regarded $4500 speakers that reportedly compete with speakers costing 10 times their price.

I think you are far too focused on cost here. Admittedly, I'd have bought a Hsu or SVS, but integration is going to be a much more important step here than worrying about not spending enough money.

3. If the Moabs go anywhere near 20 hz you don't need subwoofers. If pipe organ is your favorite type of music and you are missing the 16hz notes then you could spend several thousand dollars on a sub that would not only go that deep but was equipped with a high quality crossover that included a very low cutoff point. Wilson makes a sub for $40,000 that accomplishes this purpose.

Woah, nope, totally disagree with this entire statement.  Subs bring a lot more to the table than a spec. The ability to relocate them, to equalize them, and to limit the bass required by your main amp and speakers are big deals.  Done perfectly, you bring a lot more power and dynamic range to the system than you would have otherwise, and reduction in distortion.  Also, this is a giant PITA to do well, as this thread will attest to.

4. The subwoofers you bought are accentuating the frequencies that your Moabs are already putting out. They are doing nothing constructive.

We have not seen evidence of this, yet. So far all we have see is the sub response, and that the sub is too loud.  However, yes, the future of this system should be correctly integrating the sub with the main speakers.  One step at a time.

OP:  I just noticed that your main speakers are ported.  I am going to suggest you plug them before attempting to integrate with the subs.

For some reason I am not sure the make and model of both your main speakers and your subwoofers?  Can't imagine you can buy an audiophile subwoofer for that price range?

This is why I purchased two REL S2 SHO subwoofers.  They use a high level connection to make their subwoofers act as lower end subwoofers to extend the bass on the main speakers.  If you set things up correctly, you won't hear their subwoofers over take your main speakers.  I have the volume on my REL's set at about 40%.  They are smooth and seamless.  I wonder if REL has a patent on this technology?  If not, can't understand why other subwoofer manufactures aren't using this as well.  If you have not auditioned REL subwoofers you need to do so.  As with everything else, main speakers and subwoofers need to positioned correctly to receive the best sound. Be curious to hear what others in this group feel. 

Except for the name calling this has been an interesting thread. I've learned several things.

I realize that I'm not answering your question but I would like to take a step back and look at this from another angle.

1. Your Moabs are spec'd to 20 hz. I've never heard these speakers but they have great reviews and I've never heard anybody say they are shy in the bass.

2. You purchased two subwoofers which cost $350 each and weigh 40 lbs. to supplement the bass of a pair of full size, full range, highly regarded $4500 speakers that reportedly compete with speakers costing 10 times their price.

3. If the Moabs go anywhere near 20 hz you don't need subwoofers. If pipe organ is your favorite type of music and you are missing the 16hz notes then you could spend several thousand dollars on a sub that would not only go that deep but was equipped with a high quality crossover that included a very low cutoff point. Wilson makes a sub for $40,000 that accomplishes this purpose.

4. The subwoofers you bought are accentuating the frequencies that your Moabs are already putting out. They are doing nothing constructive.

5. If I understand correctly, the subs have no speaker input and no speaker output. In my experience cheap subs are usually designed so that you hook your speaker wires to the sub and the sub crossover sends the main speakers the high pass signal. That prevents the sub and the main speakers from doubling the bass frequencies. It looks like these subs are designed for folks who have small stand mounted speakers that have their own natural rolloff at 60 hz or higher. It's pretty obvious to me that they were never intended to integrate with a pair of full range speakers like the Moabs.

The lesson here is that your subwoofers are doing more harm than good. You are just adding low frequencies that your Moabs are already supplying. If they sound bass shy then it's likely that your room is the problem, not the speakers. It's probably not feasible to return the Sparkes but you should have devoted that money to room treatment instead of subs.

I can provide an example of a subwoofer/full range speaker setup that is working well. I have a pair of Thiel CS6 speakers that are rated to 28 hz on the low end. The bass is great but it is lacking in the lowest octave. I also have a 15" Velodyne subwoofer that incorporates a pretty steep crossover. It is adjustable down to 40 hz. I use the Velodyne with the crossover at its lowest setting. About 80% of the time the subwoofer just sits there looking impressive but not making any sound at all. But when I put on something that has low bass it gracefully adds the gut jiggling frequencies that the Thiels just can't reproduce. But this didn't just happen. I've spent a lot of hours on speakers placement to get there.

Sorry to be sarcastic, but if you think your Moabs need a pair of $350 subwoofers to sound good than you should seriously consider returning the Moabs, not the subs.

@ OP
Check out ieLogical SubterraneanHomesickBlues for a little information on setting up subs and how their controls work.

Definitely characterize you subs individually at close range and in the same position.

Visit hunecke.de | Loudspeakers Calculator and input your room. Do the same in REW.

Sadly Starke doesn’t give any sensitivity for Bal/UnBal, or much of anything else. I couldn’t find a Willsenton R8 manual.

Using BAL to the Sub and RCA to the R8 will have about 14db more gain to the subs, assuming the DAC uses industry standard levels. If the DAC does not have a level control, the subs are being driven an unattenuated signal.

Note that the SW12 has an insufficient control set to integrate well except in possibly a single location.

Hey OP,

Don’t be so upset about the Klipsch yet! See the dip around 28 Hz? This is a typical close mic measurement of a ported speaker. This is normal. Ideally you also close-mic the port, and sum the two together which is somewhat complicated math to do right. For more on this, see D’Appolito’s work, Testing Loudspeakers. 

As you move the mic away from the sub, the rear port contributions will come into play, but so will the room. Unfortunately this is how we have to do it to get quasi-anechoic measurements of ported speakers.

Next, you are right, the Starke is pretty flat, but the crossover is not doing what normally you’d expect. The THX standard, which many try to match, is a 4th order low pass filter for the sub. This helps match with a main sealed speaker that has a 2nd order high pass applied. As Duke has previously noted (and looked through the messy data) this looks somewhere between a 1st and 2nd order low pass filter.

Instead of changing the crossover frequency, you are changing the slope, and in all cases you are left with a rather low Q factor for the filter. A bad thing, meaning the filter’s effects are visible almost down to 20 Hz no matter what the setting is.

So while I like the speaker curves overall, the built-in crossover is a coarse beast. Definitely get a miniDSP and leave the sub’s crossover "wide open." You’ll be able to not only execute a 4th order low pass filter at any Hz, but you’ll be able to clean up some of the anomalies and add millisecond level delay to the sub, allowing you to perfectly phase match with your mains.

Also, please note how much better this is than your original measurements. Now that you can see how well it does, you know what to shoot for. :)




Best,

E

Pinwa 

I think that the biggest problem could be how you are running the setup control wise. If you are sending the dac signal directly to the subs and controlling the speaker volume with the amp. I suggest you try setting the amp to one set level maybe a bit over 50% and leaving it there all the time. Then dialbin the subs and use the volume control on the dac exclusively. Yoy will need to split the rca output of the dac to send to the subs and amp so the are both seeing the same output voltage. 

This will save you possible headaches. It seems like how you are currently running them, you are basically trying to set them up everything you change the volume level on the amp. 

Looking at the initial graphs it also seems like some of the issue is room gain below 50hz too. What was the spl you did the measurements at? I am asking as I have a room gain of about 10db @30hz in my space.

geared4me I use the volume controls on the R8 to get the rough level and then the volume control on the DAC to fine tune.  The DAC doesn't have any amplification.  The DAC Volume Control only reduces volume.  BUT it turns out having the Subs hooked up with the DAC's Balanced Outputs runs about 7 dB hotter than if you hook them up via RCA.  So that is where the problem with the sub running too loud probably starts since the R8 only accepts RCA inputs and only has speaker level outputs.

OK. I have taken the suggestions to measure a single Starke SW12 subwoofer near miked in the middle of the room sitting on a padded footrest which is about the best I can do to take out any factors other than the subwoofer. Just for yucks I also measured a Klipsch R12SW with similar settings.

You can see the measurements for the Starke SW12 alone here:

https://www.dropbox.com/s/dwpnt5ndcstr3gu/Starke%20SW12%20Crossover%20Settings%20Near%20Field%20Mic....

And here you can see the Klipsch R12SW alone:

https://www.dropbox.com/s/b5qb4r9f8xsasiv/Klipsch%20R12SW%20Near%20Field%20Crossover%20Measurements....

These were measured with the Sub hooked up to the DAC with an RCA cable. I did also measure using a balanced/XLR cable which provided exactly the same curves but with 7 dB of gain which explains why I was having trouble getting the volumes low enough with the Starke when I had it running on a balanced XLR input. So oldhvymec nailed that one. Getting subs and main speakers aligned seems to require using the same inputs which sucks because I have to believe all those Y splitters degrade the signal quality?

Some observations

1) Boy that Klipsch R12SW is a piece of crap! I didn’t expect it to be good but I certainly didn’t think it was that bad.

2) It is kind of impressive that the Starke is only loses 5 dB from 26 Hz to 17 Hz and has such a flat response out to about 60 Hz depending on the crossover setting.

3) Even though the Klipsch curves are so much worse the crossover seems to be functioning in a fundamentally similar way to the Starke so it could be how I thought crossovers ought to work simply aren’t how subwoofer crossovers are designed.

4) It would be nice to see similar curves for a truly high end Rel sub just to be sure.

5) It looks like the Starke SW12 will be very useful for extending the bass response lower and smoothing any room nodes if I play around with positioning them in the room but only below 60-70 hz. I have crazy peaks and valleys with my Moabs between 50-85 Hz that I’ll have to fix some other way.

Seeing as how the Willsenton R8 has no pre-amp output and the Starke SW12 has no speaker level input you are going straight from your dac to the subs, correct? Are you controlling the volume level with the dac and just using the R8 as an amp only? What you describe sounds an awful lot like you are using a fixed volume output from your dac. "They are way too loud even with the volume set almost to off". I am willing to bet you are sending a full power signal to the subs and over driving their amps. This will cause all of the problems you are having. 

Wolfie62 wrote: "Looks there is a hardwired inductor blocking output at 50 Hz. Is there?"

I speculate that the inductor is the woofer’s voice coil. In general the longer the voice coil (the more turns of wire in it), the higher the inductance. There are construction techniques which minimize voice coil inductance, but they are expensive, and may not be practical at some price points.

Duke

@kenjit wrote:

"They [Erik and Duke] are the worst of enemies and any suggestion otherwise is disingenuous."

This is a lie.

Stop stalking us both.

Duke