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



What you are listening to is distortion, bass resonance. Little loudspeakers do this all the time intentionally to give the impression of bass. I can understand wanting more bass power and weight. The best ways to do this are Digital Signal Processing and subwoofers. 


@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.  

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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@mahgister ...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...

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.