@vthokie83To clarify, my 3 ft (now 33 inches) is measured from the tweeter. So, the distance between my PR (passive radiator) and the front wall is also 20 inches. I find this to be a good compromise between the bass and the soundstage depth. How about yours?
What happened to my room acoustics
I measured the spectrogram for my room at my MLP, and the FFT results are as follows:
- There is a roll-off before 20kHz.
- A dip is present around 12kHz.
- There is a noticeable boost between 50Hz and 1.5kHz.
- The bass rolls off around 33Hz at -3dB, consistent with the factory rating.
Comparing these measurements to the Burchardt measurements, there are some differences:
- It doesn’t exhibit a roll-off before 20kHz.
- The dip is around 15kHz.
- The boost between 50Hz and 1.5kHz is not as pronounced as in my room.
I’m curious about what might be happening with my room acoustics. If a fix is possible, what would it entail?
Spectrogram from my zoom
My room / speakers setup
Measurements from Burchardt
45 responses Add your response
Lanx0003, I also have a pair of Buchardt Audio S400 MkIIs, and just a couple of recommendations based on experience.....though I have never measured the room. I am building a new audio room, and have a DSPeaker Anti-Mode to install at that time. (1) In my experience, 3 feet into the room for the Buchardts is too much, I found the cleanest and most accurate bass at about 20 inches from the front wall; Buchardt recommends closer placement to the front wall. (2) I'd reach out to Mads Buchardt for his opinion, I have found him (along with Don Sachs and Alvin Chee at Vinshine) to be most generous with his time and help. He frequently posts and answers questions on the Buchardt Audio Worldwide Owners Group.....or just email them, you will definitely get a response. |
Helmholtz resonators are the basis of mechanical acoustics... As you know i used them in my first room a lot ... Distribution and location matter ... Now in my second room with smaller speakers , i designed a new porthole for them using different straws tuned for this goal exactly as when we compute the right size of the neck volume and diameter of the resonator body ...
Then you understand my perspective ... My goal was first learning acoustics then improve my sound without cost ... Thanks for the information... My best to you ...
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Then you would know every bass guitar sounds different. This issue is not up for contention. It is an easily measurable phenomenon and not a matter of my opinion. Porting woofers is a design principle destined for the bowels of some museum. It is an antiquated method of pushing the frequency response of a woofer lower and then cutting it off abruptly in the context of a wooden box which in all respects is a musical instrument masquerading as a pipe organ. Only tightly sealed boxes need apply. Edgar Villchur knew this in the late 50's. Today, given enough power and within the physical constraints of the driver, we can tailor the amplitude response of a woofer or subwoofer to do anything we want without any added limitations or distortion. The quality of the sound depends primarily on the construction of the enclosure, how to not make a musical instrument, and that folks is a trade secret. In the late 70's Randy Hooker aka RH Labs. Made a subwoofer that was a helmholtz resonator. It was a passive subwoofer down firing into a slot. It was huge in comparison to modern subwoofers, about 3 feet by 2 feet by 2 feet. They made beautiful if somewhat colored bass. Inside the enclosure the driver was housed in a larger compartment which was slot loaded into a smaller compartment. It resonated at 20 Hz forcing the driver to go down low. It was a pleated 12" paper driver, nothing special. There were no subwoofer drivers back then. |
It cannot be patented... It is a basic concept of acoustic and the volume and diameter of the straws their lenght must be computed but with many straws it is a bit complex computation for me with the speakers volume but its is easier to tune it by ears ... The numbers of straws and their dimension parameters will differ for each speakers with a porthole ... Put in simple term: instead of a single inefficient porthole it is a complex designed more efficient porthole ... The concept if you search for it is : Helmholtz resonator ... Any speakers with a hole in particular is an actual Helmholtz resonator ...
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Interesting idea! Perhaps you could develop this concept into a customized tube and commercialize it. Whether or not it's an original idea of yours, being the first to own the commercial product could lead to significant success. Thank you for sharing it. For bass reflex or dipole passive radiator (PR) type (like Burchardt S400) of good design speakers, at resonant frequency of the box, the port / PR does most of (If not all) the hard work and the speaker barely moves. The woofer has less excursion and therefore less distortion. It really does not need to rely on couplers to transfer the energy to a big mass for reducing the resonance of the speakers as long as the quality of internal bracing is good. The problem might be with below resonant frequency of the box, the effect of the port becomes less effective and, when driver reaches large excursions, the port itself does introduce some distortion to some degree. Introducing couplers imo may help reduce that impact but, at the mean time, the modern software design tools and available port shapes could be used and optimized to minimize distortion as well. Dipole PR is more efficient rending more precise control for those impact to the box below resonant frequency. I own seal-box, rear port and dipole PR design bookshelfs. The bass performance out of good dipole PR designed like S400 is very impressive. The bass is articulate even at low volume.
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i own little speakers with a 4 inches woofer which i modified and i had clean bass at 50 hertz no boominess ...😊 How ? saying that we are in the obligation to use dsp and subwoofers as only one solution for little speakers is ignorance ... I used four solutions : --One mechanical which is damping with a heavy load on top of speakers when possible ... --Isolating/decoupling with granite blocs /shungite plate/sorbothane plate /cork plate/bamboo plate sandwich which is very efficient ... ( springs can be effective by the way but ONLY used in a certain way with PRECISE tuning control of the compressive load on the springs but i dont need springs with these light smaller speakers with my other bigger speakers i used two set of springs under and over the speakers under tuned load with a precision around 100 grams this method of using springs though is not practical for all especially in a living room ) --Using my porthole speakers for what they are acoustically : Helmholtz resonators...Then i put bundle of straws of dfferent diameter and lenght in the rear porthole, all mechanically tuned then to increase bass depth and clarity going from the 85 hertz specs to 50 with great clarity and impact ...I dont need costly pair of subwoofers to listen jazz and classical ... --Using adequate room treatment and if necessary room distributed Helmholtz resonators ( i had many in me first acoustic room with bigger speakers but in this acoustic smaller room i use the speaker itself as a resonator which i control ...) Cost: peanuts ... Results : amazing ... and a complete transformation of these well reviewed low cost speakers which now punch way over their price and beat all the headphones i listened to ...
Then proposing general recipe for all case and for all people situations as some mandatory subwoofers when anyway they are not needed and present hard problems of their own, and some DSP equalization for bass problems presented as ONLY solution is ridiculously narrow perspective ... Tools are tools not exclusive solutions ... To solve a room problem anyway we MUST BE THERE LISTENING and adressing the room mechanically and not only electronically especially with bass problems .. ... Small room acoustic is very complex...General recipe means little each case of specific speakers and specific room is a problem of its own asking for a specific tuning of the couple room speakers ...
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@mijostyn I cannot speak for Mr. McGowan, but I respectfully disagree with you regarding the distortion you have proclaimed. I believe, as a bass guitar player in a college band, I can discern between distortion and natural bass. Overly tight bass can become unnatural. Two-channel system listening experiences are subjective, and it's essential to learn to agree to disagree. I am on board with DSP and I hope it works to resolve the issues I was having. Subwoofer is another contentious topic for tomorrow. |
@digsmithd @mijostyn I found myself repeating an experiment I had conducted before concerning the decoupler/coupler between bookshelves and stands. This might turn into he says she says situation. Among springs, Moon gel, and rubber (by 3M), once again, Moon gel outperforms rubber and springs in terms of bass note weight and articulation. Springs are the least effective yielding soft bass. Rubber does have some degree of coupling effect. I agree with what you and others have mentioned about spikes being couplers. While spikes may tighten up the bass, they can also make it sound lean. I recall Paul McGowan attesting to this before. Sorry, I just need to trust my ears in this case. |
Sorry for having strong feelings on this...but it was what saved my system/and my speakers from the chopping block.I read an article in galen carol website..."everything matters".This was after searching for some answers on setup.Turned out just some loose spikes under sound anchor stands...Tightened them down/re setup speakers....Totally transforming.Sound stage snapped in,had tight bass,ect.I had to redo setup a skosh... but the work was worth the effort.Sorry for add butt... https://www.usaudiomart.com/details/650038696-isoacoustics-gaia-ii-carpet-spikes-2-sets-of-4/ |
It is always best to use three spikes. They should be driven clean through any carpet and padding into the plywood. Three spikes on tile is OK as long as you lower the speaker gently. The best digital signal processing units sound like whatever you make them sound like. You can create any target curve you like within certain limits. After 25 years of doing this I can look at a curve and tell in a general way what the system will sound like. You can not determine imaging this way. I have to see measurements on each channel separately to get an idea, again in a general way. The best units are now using 64 bit floating point systems with powerful processors. They run at a minimum of 24/192. There is no characteristic sound. It all depends how you program it. Most system like Dirac Live run on their own algorithms leaving you little room to play. You have to accept whatever they do with minor adjustments. With my old Tact and the new DEQX units you can let them do their thing and walk away or you can grab the bull by the horns and program the unit yourself which IMHO produces the best results once you learn what you are doing. |
@mijostyn It seems I need to re-investigate the speaker decoupling subject. I have used the factory spikes under the stands on the tiles for my Wharfdale Linton and it works fine. Bass is agile/nimble to my satisfaction. But I have never try spikes under my Burchardts. I guess these non-intrusive spikes below won't break my bank and worth trying. For the room correction (RC), I do prefer the RC resided in the streamer rather than preamp section so it is processed digitally before the analog conversion. I believe the digital EQ / dsp is more precise than the analog counterpart. Moreoever, I have a pretty decent preamp that I do not wish to be swapped. However, at the mean time, the digital EQ/DSP may sound more clinical / harsh due to its precision. It is sort of double edged sword. Your thoughts? I guess, for the time being, since I have ordered Unison, I may just keep my finger crossed and hope the best. Based on all the good reviews I have read so far, I have no doubt that Unison will do a decent job in RC but just worry about its preamp section may not be up to par.
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If you have a good floor the last thing you want to do is decouple the speaker from the floor. Ideally you would bolt it down to the floor. Spikes are the usual option. Why? Newton's 3rd law. You need a very massive, fixed mass (the floor) to control the reactive forces or the speaker shakes. Play a 20 Hz test tone and put your hand on the speaker. What you feel = distortion. Now spike the speaker to the floor and you will feel less shaking. You might also notice more aggressive bass. I'm afraid this whole speaker decoupling gig is an example of lay intuition. If a floor is so bad that it resonates in the audio band then fix the floor. Most floors dampened by carpet might only resonate in the 5 to 10 Hz range, great for causing footfall problems with turntables but not a problem for loudspeakers. You might want to consider a MiniDSP SHD Studio. This assumes you have your own DACs. It uses Dirac Live which is similar to ARC. This unit is $1,300 and includes streaming. Benchmark Media Systems uses a Studio with their own DACs and is super pleased with the results. It also includes subwoofer crossovers and bass management. |
Thanks, but that isn't the cause of the issue. As I explained, the treble dip at 12kHz is most likely inherent to the speakers, while the boosted midrange and mid-bass are likely due to reflections. I do not use spikes under stands or speakers. Spikes are not ideal decouplers. Instead, I use Moon gels, which are drum dampers, under the speakers. In my opinion, they are far more effective decouplers than spikes, and they also help keep stand-mount or bookshelf speakers level and stabilized on the stands. Based on my A/B listening tests, the bass performance is as good as the SVS SoundPath Isolator, which costs $99 for a pair of speakers. |
@erik_squires @newbee @mijostyn @rhljazz @hilde45 @audiokinesis @ervikingo @jamesw767 @aewarren @ronboco Again, thank you all for the insights and great suggestions. I think I may have found a potential solution for issues I am having. The Anthem Room Correction (ARC) system seems promising. A gentleman had the same 12kHz dip issue in his Buchardt S400 II speakers (so I guess it's inherent to the speakers) and he was able to correct it with the ARC built into his Anthem STR preamp (>$3k). I don't plan to purchase that expensive preamp, but MartinLogan has a Unison preamp ($199) with ARC built in. I hope it will do the same trick to address my issues. Fingers crossed for it.
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@ervikingo The almost full-range Aerial 8 is reviewed favorably with impressive specs. It could be an endgame choice. Good luck with them. The Poang chair is a bit too upright for my liking as well. But if I sit further tilted back (on other chairs), I found that the sound perception changes drastically. I am getting used to it now. |
@lanx0003 No worries, those are suggestions. They have worked well on my 4 prior rooms and speaker setups. The most challenging were the Aerial 8b with the side firing woofers and the Betas since you have further flexibility but I had already placed a huge projection screen which can't be blocked. BTW, like the Poang but its a bit too upright for my back. |
Thanks @aewarren & @ervikingo. I experimented with that a while ago. If you take a look at my second sketch, you’ll notice the ’golden ratio triangle’ where 0.448W and 0.276W align exactly with your numbers. Unfortunately, I’m not fond of this arrangement. Firstly, it utilizes only 6% (17 square feet) of my entire room space (280 square feet) for the listening area within the equilateral triangle. If I place my Poang chair with an ottoman in that listening position, my feet would almost touch the speaker plane. It feels quite cramped. Secondly, I found the speakers and stands to be extremely intimidating. I didn’t enjoy the setup at all, and I couldn’t sense a spacious soundstage in such a small space. I must admit it’s a setup that I find rather impractical. I apologize for the strong language, but that’s my honest feeling about it. |
A suggestion, I start with math for positioning my woofers (Cardas formula) which in your case will be approximately 6.25' from front wall and 3.8' from side walls. I would then start sitting (on a chair on casters) at a perfect equilateral triangle and roll back (away) from the speakers slowly which will help you find several "semi sweet" spots which you can focus on later on when fine tuning.
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Thank you, @newbee. I did experiment with varying toe-in angles, ranging from straight to pointing towards my shoulder, to find a trade-off between the width of the soundstage and imaging. I ultimately settled on a slight toe-in that points slightly outside my shoulder without realizing that what I perceived as an 'augmented' soundstage was, in fact, the out-of-phase reflective wave. Surprisingly, I found that I actually prefer a wider and more three-dimensional soundstage, even though it doesn't come with the benefit of deepening the soundstage that I've always wanted. Dr. Toole has asserted that these reflections, including the first lateral reflection, should not necessarily be absorbed. I did measure the right channel at 3 ft but didn't post it. The response appears flatter, but it has more humps and dips. I'm beginning to doubt the accuracy of the measurement tool I was using...
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As I look at your latest graph readings, and I do not know how your unit operates, my initial concern is not so much about the rise of the upper bass thru the mid range, as a unevenness of the ’curve’ which shows alternating +/- readings of up to 10 db’s (between 100hz and 200hz and 1khz and 2khz. This suggests to me, and seems to support your conclusions re needing to tame your room with acoustic materials of some sort. But, before you go there, if you do, try running your tests with your speakers axis in different positions. FWIW, one of the benefits (and to others detriments’) of minimal to no toe in is that the 1st reflection points to the sides of the speakers can give a sense of greater width, however in reality in a recording an in-phase sound can only appear between the speakers. What you hear on the outside of your speakers is out of phase sound put there in the recording process or reflections off the side walls. I think you have pretty much identified the differences in set up and realize it’s a choice that affects what you want to hear. I’m almost out of wind now, but FWIW, you might try measuring the FR of each speaker separately with your mic about 6ft from your speaker and see how flat the speakers FR really is and determine how much its unevenness, or lack thereof is contributing to your in-room response at your listening position. Just for kicks you might try measuring the FR from your listening position with it in an equilateral triangle and your speakers on axis. Probably won’t resolve anything but it might just be interesting. It will/should give you results which reduce the effect of the room in your sound. Hope this helps a bit. |
Thank you all for the advice. It appears that the consensus here is that I am sitting too far from the speakers. I've adjusted the seating position, bringing it closer to the speaker plane (11 ft), with the speakers now placed 9 ft apart. My room has a 10 ft high ceiling. At the new MLP, I measured the spectrogram again on both channels, both together and separately. The FFT results are as follows: The high-frequency dip has shifted to a slightly lower frequency and appears to be more pronounced. The left and right channels exhibit similar profiles. On paper, it appears that sitting closer is not resulting in improved sonic performance in my room. Basically, I agree with @audiokinesis who commented on the in-room energy below crossover frequency (=1.8khz). I probably need a lot of panels on the sides, which may not receive WAF certification.
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In my opinion: "There is a roll-off before 20kHz.." This is the shortest wavelengths being absorbed by surfaces in the room. "A dip is present around 12kHz.." There will be a on-axis cancellation dip in the response with a round horn or round waveguide, centered on the frequency where the mouth reflection arrives 180 degrees out-of-phase a the listening position. The center frequency of this dip changes with listening distance or microphone distance. Off-axis the arrival time of the horn mouth reflection is smeared, and the cancellation dippage is correspondingly reduced. "There is a noticeable boost between 50Hz and 1.5kHz." The midwoofer's pattern is wider than the waveguide's pattern below the crossover frequency resulting in more in-room energy below the crossover frequency. Duke |
A few comments: Yes, move the seat forward. You’re probably hearing a lot from the rear wall you could eliminate by moving forward. My speakers are 8 feet apart and I sit 10 feet away. My back wall is another 9 feet behind me. Worth a try. Did I miss comments about ceiling height? Some of the worst reflections come from floor or ceiling. They may be interfering. It's very helpful to measure impulse responses to see how the reflections are, or you won’t get a handle on imaging and soundstage. Get those as many reflections between 4 and 12 ms down below -20db if you can. Viz. - There is a roll-off before 20kHz. COMMENT: These are very high and likely won’t matter much. (In my view.) COMMENT: Much more important.
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Your room doesn't look that bad to me, many are much worse. Of interest is that you mapped out the "golden triangle" and then didn't adhere to it. As others have suggested, your listening chair is too far away from your speakers. I suggest you pull your speakers another foot into the room and move your seating position at least two feet farther into the room. Try listening to music instead of measurements. |
First of all, your listening position need to be 5 feet closer. Things are actually worse then they seem. The Y axis is in 20 dB increments. Most systems I have seen use 5 dB increments. This is a very shouty curve with the bass lagging 10 to 15 dB behind the midrange. From 200 Hz up things are actually quite good except for that dip at 12KHz. You need to measure each channel separately and compare. The ideal in room curve starting at 20 Hz which should be 5 to 10 dB above baseline sloping down and reaching baseline at 100 to 120 Hz, then flat out to 1 kHz then a steady slope downwards to 6 to 12 dB under baseline at 20 kHz. Bothe channels should mirror each other directly. I would like to see if that 12 kHz dip is in both channels. Any difference between the two channels will screw up your imaging. You need to deaden the front and side walls at the first reflection point which may calm your midrange and I would remove the bass traps. After that your best option is a digital preamp with EQ and room control. Subwoofers and digital bass management would give you much more control over the bass. Don't feel bad. I have measured many systems worse than this. I just measured a system with Magico S7 loudspeakers. The imaging was pitiful for speakers of that caliber. Low and behold one channel had a 10 dB dip centered on 300 Hz. He is ordering a DEQX Pre 4 which will fix the problem. This is like a photograph out of focus. You use digital EQ to focus the system and you can see the results with your measurement system.
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The room measures fine to me. Many are much worse. People just don’t measure and they have no idea. two things stood out to me. #1 the seating distance with the speakers 8’ apart my max seating distance would be 10’ and for me I would try closer to 8’ as it would maximize soundstage width at the cost of center focus (personal taste). Then I would toe in until the center focus is back. The down side of what I described is you shrink the sweet spot but you get a better sweet spot imo. Being so far away also pulls in a lot more room reflections. Closer will be more direct sound. #2 the equal distance from the side wall to back wall from the driver face should be avoided. This will increase the null created by the wave length that has a 1/4 wave of 3’. Which is right around 90hz. It will also result in a peak but I am not sure where that peak will be, but higher like 180hz for example. I would move them closer to the back wall (I know this sounds wrong but try it) to avoid equal distances.
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Thank you both for the suggestions. Before I made the following adjustments for the speaker/listening positions, I tried treating the first reflection point, but the HF dip is still present with the same magnitude. I’m not sure why the dip shifts to a different frequency in my room as compared to the factory measurements though. 1. I separated the speakers a bit further, placing them at 9 ft apart, and pulled my listening position closer to 12.5 ft from the speakers. Previously, I had a long-to-short side ratio of 1.7, and now it’s 1.4. This adjustment seems to enhance the sense of soundstage depth somewhat, but it still doesn’t meet my expectations. Achieving the desired soundstage depth appears to be the most challenging aspect. 2. The S400 has a passive radiator in the back. I noticed that if I move the speaker further away from the front wall, the bass becomes noticeably less weighty. 3. I experimented with a sharp toe-in angle before because a few audiophiles here advocated it. It did improve the imaging, but the width of the soundstage suffered a bit. When the on-axis lines cross in front of you, it can sort of create a "crosstalk" effect. The crosstalk effect degrades the image but simultaneously enlarges the soundstage width. In both cases, I’ve sensed that soundstage width resulting from a sharp toe-in is typically confined within the boundaries of the speakers, whereas with a slight toe-in (approximately 6 degrees), I can achieve a soundstage wider than the speakers in my room. 4. I didn’t remove the bass trap because I found that the bass trap effectively addresses the standing wave around the corner, reduces unwanted excessive reverb, and, as such, improves the imaging. |
I agree with newbee. Your chair is too far away. You are hearing more of the room and less of the direct sound from the speakers. Setup is critical. Forget adhering to a specific formula. They can be useful for sure but are not absolute. In additional, the equal distance measurement from the front wall and side wall usually doesn’t produce the best balance. I suggest you continue to experiment with your setup insofar as speaker position and listening position. IME bass traps located in the front corners suck the life out of the sound with the exception of ASC tube traps which have variable reflectivity. You might try what you have at the back corners if possible. |
FWIW, my room is about the same size as yours (19.5x13.5x9), but my set up is a tad different. I use the triangulated set up with my speakers 4' off the wall behind them, 9' apart, sharply toed in (axis crossing slightly in front of my head). My chair is about 4.5' off the back wall and placed to avoid a bass node at about 60hz. I have no special room treatments but I do have window coverings (heavy drapes), book cases, and soft furniture. 1st reflection points have been dealt with. My sound stage is excellent in that it allows very specific instrument placement over the entire wall behind the speakers. I measured my room, speakers etc endlessly (it seems) but ultimately it was tuned by ear. The point of my saying all of that is to suggest that your chair might be too far back from the plane of your speakers which might just be a bit too close to the wall behind them and your low and midrange node may be the result of a room node which will change with moving your speakers forward. The HF dip could be the result of the off axis output of your speakers (but not so much reflections, I think). BTW, FWIW, I know nothing special about your speakers. Also, for the most part, the measurement that really matter are those made with the mic at the listening position. Measuring your room or trying to duplicate the speakers spec's is really meaningless, interesting perhaps. Regarding sound stage, with my present system, the difference between my present system set up and one with the chair further back toward the rear wall was that the sense of depth diminished and there was some loss in specificity. Those issues disappeared when I moved my chair forward (towards the speakers) to something closer to an equilateral triangle. |
I really do not know what are you talking about. I am addressing my message to the Audiogon forum. My speakers are Burchardt S400 II as said in the chart. Thank you for the clue about the 12khz dip being possibly due to reflection. I will investigate this furhter.
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Is this even the right forum? It seems like you are replying to a thread from a different web site. You might want to clue us in on what speakers you are even talking about. Measure 1 speaker at a time. That dip you see around 12 kHz can very possibly be a reflection issue. If ithe frequency response dips change frequency as you move the microphone closer to the speaker that’s your clue. Generally speaking, if all you have for room treatments is the bass traps and single curtains you are not going to have enough. Treating the room to be more absorbent in the mid to treble regions (including the ceiling) will let the bass emerge from underneath. Another approach, of course is to move the speakers closer to the rear wall until you get the balance you are seeking, or just use tone controls. :) |
