Is this how a Subwoofer Crossover is supposed to work?
It may help you to think of crossovers if your realize that the are not independent of the sub's own natural rolling off of higher frequencies. The low pass filter in the sub ADDs to the natural low pass filter. To figure out what you are starting with, set the HP filter as high as you can and measure there. |
Not an
expert, just my 2 cents. 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..Yes, but depend on the crossover, usually subwoofer low pass filter slope is 12 dB/octave instead of a sharp drop. But Starke says this is how a subwoofer crossover is supposed to work.I think this is how a Starke subwoofer crossover supposed to work. Is it possible to buy an inexpensive active crossover that I could use in place of what is built into these subs?Look like you can't bypass the built-in crossover! Any chance to return it? |
erik_squires I can remeasure with one sub and set the crossover to its 200 Hz high point but I'm not sure the results will show much difference but you can never tell. I am using a Willsenton R8 tube amp to drive Moabs. If I want to add subs to level out the room nodes they either have to be connected at the DAC which is why the SW12's looked ideal because they have a balanced input so I use the balanced outs from the DAC to the Sub and the RCA out to the R8. From their web page I can't figure out how the MiniDSP would fit into that setup. |
imhififan1 Shipping costs returning the subs would be a significant portion of the purchase price. I would rather figure out a way to make them work for me if possible. |
From their web page I can’t figure out how the MiniDSP would fit into that setup.https://www.minidsp.com/images/documents/miniDSP%202x4%20Balanced%20and%20Kit%20-%20User%20Manual.pd... Look at page 12 |
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It is NOT setting the roll off.. It is setting the POINT of the roll off. @ 12 db and 50hz, there is STILL a lot of BASS (ability) in that room. Set all tone controls FLAT, if you have them. (Preamp) Turn one sub off. Turn ALL the knobs CCW. Use only (SUB) one at a time. Split the XLR or the RCAs. Don’t mix the two for now.. If you do, swap the sub XLRs for the RCAs on the mains, that alone could be a problem.. Higher gain...for the subs less gain for the mains. REVERSE it.. or just use one or the other XLR or RCAs, for now.. 0 phase 50 hz XO 0 gain.. The roll off is gonna be 12-24 db, probably 12. 12 db per Oct.. Turn it on AND... Add in the GAIN only to about the 11 or 12:00 position.. No phase shift...YET... No higher than 50hz on the cross over, YET. Flip on the second Sub unit. Same thing. ALL 0, and 50 hz on the XO. Now turn up the gain to the 10-11:00 position.. Smile.... Now better location, placement and very tiny adjustments... The further apart the speakers are, the more likely they will need a "Phase" adjustment, BECAUSE of the Moabs... AND or Limit the Moabs to START at 40-60 hz. If you can do that, I know I would be happy. Then and ONLY then would I measure for placement, and placement ONLY... that will smooth the hot spots. A quick way to limit the Moabs is an inline (cuts below 40-60 hz) simple pro audio way of doing a sound check adjustment. (tip from my little brother) I don’t use inline filters... Option, though.. Setting up corner to corner is a great option too.. A lot less room treatment is needed... Like ZERO.... Regards |
erik_squires I can remeasure with one sub and set the crossover to its 200 Hz high point but I’m not sure the results will show much difference but you can never tell. Depending on the delay and the frequency, you can cause destructive interference. For sure, if you can’t integrate 1 sub, you can’t do 2. Measuring with one sub with the crossover wide open tells you what your sub is like alone. It’s an important baseline. For instance, if the FR looks like you posted, that’s pretty bad, and you are definitely going to have to do a lot of EQ. On the other hand, if it smooths out, and looks nice and flat-ish to 150Hz or so, you know you have a good starting point. Integrate your closest sub, so you know what is possible, then blend in your second so your result is as good, if not better than your first sub. If your overall FR with 1 sub still looks that bad, then you have other issues, and will need serious EQ. Putting in both subs and attempting to hammer the EQ into place though is madness. :) Trust me. :) |
In my opinion a good starting point would include seeing what the sub itself is doing without the room’s effects. Since this is a sealed-box sub, this will be fairly straightforward. Measure the sub’s output with the microphone about 1/2" from the center of the cone. This is called "close-micing". The output from the cone will much louder than the room’s reflections at the microphone location, and will essentially overwhelm the room’s effects. The difference in shape between that curve and your normal in-room curve is what the room is doing to the sub’s response. Speaking of differences, the differences between your 50 Hz, 90 Hz, and 130 Hz curves look to me like they are "in the ballpark" for a 12 dB per octave crossover. The 50-Hz feature you are identifying as the "crossover point" is probably either a room interaction effect, a frequency response anomaly native to the subwoofer, or both. Having the close-miced curves in addition to your in-room curves will give you valuable insight into what is native to your subwoofer and what is caused by room interaction. Pinwa, you mentioned that you are using two subs. Two subs can work together to give smoother in-room response than either one alone. How much freedom do you have to re-position your subs? I disagree with Erik’s statement that "if you can’t integrate 1 sub, you can’t do2. " As the number of intelligently-distributed subwoofers goes up, not only does the in-room response become smoother, but the specific location of any one sub becomes less critical. Duke subwoofer designer and manufacturer |
Kenjit, We are all still waiting on you to post a blog post with details on anything you've bought, built or improved. You are able to attack me only because I publish excessive details on what I've made. Your only contributions to this forums have been random and self-contradictory theories with ZERO factual information. Is this the week you believe in engineering, or the week you don't? Does that change hourly for you? Best, E |
I disagree with Erik’s assertion that "if you can’t integrate 1 sub, you can’t do 2. " As the number of intelligently-distributed subwoofers goes up, not only does the in-room response become smoother, but the specific location of any one sub becomes less critical. Hi Duke, I don’t disagree that things get smoother, but if you don’t know what 1 sub will behave like, you have no idea of the second is making things better or worse. Attempting to set crossover points, and delays for both subs at the same time is a lot of work. Far easier to do after you’ve gauged the overall response of a single sub. The FR response of the OP using two subs was, I think you’d agree, pretty awful. Seeing a single sub’s FR would clarify much. However, it is clear to you, and other experts that 2 subs are better than 1. :) Best, E |
pinwa, First, congratulations on the Moabs. How long you had em? Should sound real nice with that Willsenton. KT88 or EL34? How's it sound? Aside from the subs I mean. Sounds like your problem is the line level from the DAC is high enough you're not able to attenuate it down to where you want it. If the Willsenton had RCA pre-outs that would be ideal. Doesn't look like it does. So your solution would be to do like I did with mine and create a pre-out by using what is called a Line Out Converter or LOC. An LOC is nothing more than two resistors that serve to drop your amps speaker voltage down to line level. Here is the circuit https://www.epanorama.net/circuits/speaker_to_line.html If you remember my Melody amp didn't have pre-out either. What I did was modify one of my extra unused RCA inputs by adding the two resistors to turn them into a pre-out. You can see a photo of the mod on my System page https://systems.audiogon.com/systems/8367 Its not much, very simple. Total cost for the 4 resistors was just under $2. If you don't want to mod your amp (its easily reversible btw) then you can make your own LOC for $2, connect it to ordinary speaker wire, put an RCA on the end and plug it in. Or buy the cheap one from Parts Express. Same result either way. This should totally solve your problem. |
Gah, can’t type today. Or any day. I wrote: However, it is clear to you, and other experts that 2 subs are better than 1. :) I meant to say: Duke, Toole and other experts agree that 2 subs are better than one, and I agree. I’m just offering up a simple way to get to done from where the OP is, so I am suggesting to measure the single sub FR first. It can’t really be as awful as the first measurement was, can it ? Of course, a final 2 sub install should be equal or better than 1. |
"Attempting to set crossover points, and delays for both subs at the same time is a lot of work. Far easier to do after you’ve gauged the overall response of a single sub." Hi Erik, My experience, and the experiences of many customers who are using four subwoofers intelligently distributed, has apparently been different from yours. To the best of my knowledge most if not all of my customers have previous and often extensive experience with subwoofers (no newbies as far as I can recall), and instead of integration being far more difficult than when they were using a single sub, many report it to be far easier and faster. Not a single one has reported setup to be more difficult than when they were using fewer subs. And is seems reasonable to me that two subs (intelligently distributed) would fall in between one and four in difficulty of integration. I don’t dispute your experience, but I do disagree with your generalized conclusion that "if you can’t integrate 1 sub, you can’t do 2", though a different setup paradigm may be called for. Duke |
I missed the Willstentin reference For the MOA Beast Save yourself a headache, take a break from the subwoofer conundrum, and get some solid state. Try https://renohifi.com Money back trial period |
I appreciate all the input here although I am less enthusiastic about how this thread has devolved into the kind of digressions and name calling that seems typical of Audiogon. Also, since these forums don't support true threading it is challenging to actually respond to each of you. Most importantly though, is my starting question, at its simplest, is really just whether or not subwoofer crossovers are supposed to behave the way the Starke crossover is behaving. I'll measure an individual sub later this evening and add a setting for 200 Hz. But assuming that still shows the rolloff starting from the same place, i.e. roughly 50 Hz, regardless of the crossover setting is that normal? millercarbon Moabs are great but with caveats. That discussion deserves a separate topic. |
Hi OP No, the measurements do not look like very good representations of crossover behavior when changing the crossover point. However, since there are two subs involved, I can’t tell what is going on. I completely agree with Duke that 2 subs are better than one, but I think for the sake of your sanity, you should measure one first. :) See if that doesn’t work as you’d expect. You know, you might want to try out XSim crossover simulator. It is free, and you can draw several ideal speakers, and use different crossovers on each, and plot their behavior. Best, E |
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@pinwa I don’t see anything that tells where your sub placement is. To start, make sure that your subs are at least 3ft from any wall and make sure that your subs are not near each other. Starting here will help reduce any room boundry reinforcement from the corners. In fact stack some things in the corner to help break up standing wave.. Pulling them out in the room normally helps reduce peaks. Next, turn your subs all the way down, bring one up a hair and measure. See where the peaks are. Turn this one down and check the other, measure and see where the peaks are.... Move them around checking independently trying to remove frequency peaks. Once you see that the peaks are down, bring them up together just slightly, measure and adjust as needed. This will all take some time and this is only a starting point. I hope this helps, Tim |
Erik asked: "Then let me ask this question another way. Looking at the OP’s original data, have you ever seen 2 subs start out that poorly in a room?" I’ve never measured two subs in a room. There may be significant room for improvement, but do not know how much of what we see in his curves is room interaction and how much is the subwoofers’ native response. Pinwa asked, "my starting question, at its simplest, is really just whether or not subwoofer crossovers are supposed to behave the way the Starke crossover is behaving." Your measurements look to me like they are in the ballpark for a variable-frequency second-order lowpass filter. I can elaborate if you’d like. Duke |
Erik asked: "Then let me ask this question another way. Looking at the OP’s original data, have you ever seen 2 subs start out that poorly in a room?" To my eyes, they should look a lot better than that, if configured well, but since I can't tell what is by design, and what is interference I think the OP would be well served by eliminating 1 major variable in his measurements. Plus, it’s fast, and cheap to do. |
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audiokinesis "Your measurements look to me like they are in the ballpark for a variable-frequency second-order lowpass filter. I can elaborate if you’d like" Please do since I don't know what that is. |
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"Please do [elaborate]..." "First order" means "6 dB per octave". "Second order" means "12 dB per octave. "Third order" means "18 dB per octave". And so forth. I made a mistake and mis-read the vertical scale. Upon closer inspection, the slopes I’m seeing are closer to 6 dB per octave than to 12 dB per octave. For the moment let’s focus on the SPACING between the the lines on the 50 Hz setting, the 90 Hz setting, and the 130 Hz setting. The change in the spacing between the curves will tell us what the different crossover settings are doing. Over the octave from 50 Hz to 100 Hz, the spacing between the 50 Hz and 90 Hz curves grows by about 4-5 dB. This is about what we’d expect from two 6 dB per octave ("first order") filters that are less than an octave apart (90 Hz is less than one octave above 50 Hz). Over the octave from 50 Hz to 100 Hz, the spacing between the 50 Hz and 130 Hz curves grow by about 7-8 dB. This is about what we’d expect from two first order filters that are a little more than one octave apart (130 Hz is more than one octave above 50 Hz). Okay, now let’s stop overlooking the ups and downs in your measurements. The rolloff certainly LOOKS LIKE it begins at 50 Hz regardless of the filter settings. What we don’t know is, what the response of the subwoofer is WITHOUT the room. For instance, that EXTREMELY steep rolloff between 50 and 55 Hz looks to me like a room interaction effect. But the general trend over the two octaves from 50 Hz to 200 Hz is a significant amount of rolloff, so I SUSPECT that’s in the subwoofer’s native response. Mentally subtracting out the crossover filters, it LOOKS to me like the native response of the subwoofer is rolling off at ballpark 12 dB per octave north of 50 Hz. ONE possibility is that the subwoofer’s voice coil has very high inductance which results in significant peaking in the 40-50 Hz region, followed by a lot of rolloff above that region, due to inductance or cone mass or both. (A very high voice coil inductance can easily happen in a subwoofer driver, resulting in a response peak like what we MAY be seeing in the 40-50 Hz region, followed by an inherent rolloff like what we MAY be seeing north of 50 Hz, but without a close-mic’d response curve we cannot reliably say what is room effect and what is not.) So I THINK your subwoofer’s crossover is working as designed. I THINK that the response curves you are getting are a combination of the native frequency response of the subwoofer, the effects of the crossover, and room interaction. Duke |
LImited knowledge but I have used subs and feel I get some reward. I have used successfully small cheap ones for computer, kitchen and better one's (REL) for main. Some main speakers do better than others with sub. My old KEF's are a bit slow in the bass and the sub can accentuate it. Most of the time I find keeping the role of the sub subtle is better. A touch of bottom, warmth, fullness but not a lot. My new speakers (Sonus Faber) are cleaner down to where they stop and I find that easier to get the bass in there improved without drawing attention to itself Images again are bigger, deeper, fuller. But the key for me is a light touch. I agree with those that suggest one at a time. Placement and settings very key And in the end one setting might not give best results on ALL music I settle for the settings that provide SOME benefit but least annoyances. |
Sorry for all the conjecture. I see a decent amount of room interaction so I would do what Duke and Eric recommended. Measure close to the driver and just one sub at a time. I would put it in the middle of the room, as space permits, and measure with everything set to flat. The web page mentions a bass boost or "punch" setting? Make sure that is not engaged. And lastly, as has been mentioned, the XLR output is much hotter. Get a cheap 1-2 RCA splitter for both channels and start over. Best of luck and keep us updated. |
Sub Setup......One of the greatest challenges in audio. Some very good suggestions here. So many I can't imagine one trying all of them. Since your post asks about the crossover function of the subs I would address that first. Given your setup I have another suggestion......An active crossover. With that the sub's crossover is set to it's highest value. Then the active crossover selects the actual crossover. There are several brands. JL Audio makes an excellent one but a bit pricey. You may search for an Outlaw ICBM in the used market, since it's not in production anymore. Original cost was $250 so a used one can be had for a reasonable price. Offers hookup for 2 subs (and other speakers) with 2 different slope settings. Maybe worth a try? |
Cheeg wrote: "There is some great information here, but this thread REALLY has me wondering if I want to mess with subwoofers!" Well said. This thread would be an extremely discouraging introduction to subwoofers. There are some very successful schools of thought when it comes to subwoofers and integration with the mains, and that fact is not at all obvious from this thread. REL, Rhythmik, Vandersteen, Hsu, JL Audio, and others embrace various different approaches which have worked very well for many people. Yes these subs are more expensive than the ones in this thread but imo they are worth it. Erik has a blog post about his approach, and while I’ve been known to gripe about parts of it, I’m going to post the link because imo it offers a well thought-out roadmap to success: https://speakermakersjourney.blogspot.com/2020/04/how-to-not-buy-subwoofer.html Erik and I may disagree on some of the finer points of subwoofers, but we both think they can be well worth messing with. Duke |
audiokinesis Duke, Thank you for that elaboration. Very helpful and informative. I'll make some measurements of a single Starke SW12 this evening as well as a very cheap Klipsch R-12SW that I have lying around and post those results. |
There is some great information here, but this thread REALLY has me wondering if I want to mess with subwoofers! Cheeg, To be fair, it isn't the sub, it's the lowest octaves. There be dragons there. Sometimes you are lucky and they don't notice you, but if you are going to take them on, a sub is the best way to go. Having said that, for the single and dual sub use case I've stopped trying to advise anyone to integrate their subs, but rely on built in systems like JL Audio or automatic room correction. And like Duke, I think the depths are worth having. |
Erik and I may disagree on some of the finer points of subwoofers, but we both think they can be well worth messing with.The disagreements are not on finer points. They are on the basic facts. It's no secret that Duke is a proponent of the so called DBA bass technology. Erik however is an opponent of this. Here is what Erik has to say about it: I am no longer a fan of this idea due to the fan boys and how cultish they have become. Please read details directly from the vendor as I am not a fan and therefore won't do it justice. In this thread, here is what Duke had to say about the measurements OP posted up: Your measurements look to me like they are in the ballpark for a variable-frequency second-order lowpass filter.Here is what Erik said No, the measurements do not look like very good representations of crossover behavior when changing the crossover point. However, since there are two subs involved, I can’t tell what is going on.In conclusion these are diametrically opposed views. They are the worst of enemies and any suggestion otherwise is disingenuous. |
Don’t get buyers remorse.. GET EVEN. Make it work.. K quit stirring the pot.... You make me sad... Were gonna have a big break up if you keep it up... :-) I think the issue is NOT a problem. I say if the bass boxes, WERE treated like SUBS you would be just fine. 200 hz Man oh Man.. Nothing to do with SUBs ok. 50hz at a 6 db roll off would put the SUBS still making bass way over 100 hz..... Does that make better sense OP... It’s a LONG sloppy slope to BASS BOOM HEAVEN (this case hell)... You’d fit right in with some of the kids around here (BIG SMILE) At 12db, @ 90 hz or so, 18db @ 80, 24db @ 70-75. Do you see the correlation. Here is a real nugget.. Break in the subs FIRST... They usually are pretty tights for 100 hour or so.. IBs take longer to break in... Give stuff a chance ONE sub at a time.... Turn the knobs CCW, like I said, and make sure the XLR, RCA issue is fixed FIRST... There is a HUGE difference between XLR input and RCA... READ... This cost NOTHING.. Measure AFTER it sounds BETTER, not worse.. man oh man... You’re way ahead of yourself.. 1. let the things break in a bit, cables settle, and use XLRs or RCAs not both (FOR NOW). Split with simple Ys. Mains and subs... 2. turn the XO, GAIN and PHASE, CCW 3. get one right first (including break in) Read my second post for tuning... I use a simple SPL, with tone burst where I know they have problems, 50 80 and around 1-130. Its a ceiling height thing... Folks forgot the basics.. An SPL Meter.. REW. I have all that stuff.. LOL. BIGGER LOL So you know REW, always will tell you to TURN IT DOWN....HUGE LOL.... Learn your room... Break in your new gear.. be patient... Enjoy.. OP... Oh and happy bumpin New Year, Steam plunk, caplunk... Hat on the floor...... Olay.... Tap Tap, Cha Cha Cha.... Regards |
Those plots of FR dont look right at all. Those 12" drivers should produce good output to at least 500 Hz. Looks there is a hardwired inductor blocking output at 50 Hz. Is there? You should see good output up to the chosen cutoff frequency. Yes, dips and peaks, but should be good output, even with room effects. Something is definitely WRONG here. |
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 |
