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

lanx0003

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 ...

 

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.

@lanx0003 ,

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. 

@mahgister 

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. 

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 ...

 

@mahgister

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.

the simplest solution is usually the best.

I would pull the speakers forward 1 foot and move closer 3-4 feet.

What are your speaker stands and height? To me the gel seems an ok solution

The stand is 32-inch high, placing the tweeter below ear level, but the 5-degree tilt of the front baffle on the S400 compensates for this gap.