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8351 not sounding good, acoustic issues in treated room

nordskog, modified 1 Year ago.

8351 not sounding good, acoustic issues in treated room

Youngling Posts: 3 Join Date: 8/16/19 Recent Posts

Dear Genelec community,

 

I just finished making acoustic treatment for my new studio, and bought a new set of 8351s that I’ve been very eager to test. I’m having issues with the acoustics in my room and the sound I’m receiving from the 8351s that I need help to fix. 

Sorry, I might have written way too much! I tried structuring it to improve reading experience. 

 

QUESTIONS

How can I improve my room and listening situation to get the flattest and best sound that I can get out of my new 8351s? How can my treated room sound this bad? 

 

My room is approximately 4.2m * 4m with 2.4m to the ceiling. 

The treatment includes four big bass traps with dimensions 220cm*57cm*20cm. One trap @ 120*57*20 (15cm glasswool, 5cm air). Nine traps including two ceiling clouds @ 120*57*15 (10cm glasswool, 5cm air). The desktop is tilted slightly towards me to avoid flat reflection towards ceiling. 

8351 current placement is in width on the desktop with coax 120cm above ground and below ceiling, 110cm apart from each other and listening position, tilted slightly upwards. 40cm from front wall, with 5~cm air space between contact point and the front wall treatment. 

8020 placement is on stands 160cm from the floor, tilted downwards. 38~cm from front wall with sufficient space around them. 

 

See attached pictures for GLM readings and pictures of the room layout. 

 

CONTEXT

The 8351s gave me a really good first impression when casually testing them in the room in a very roughly acoustically treated state on the desktop with approximate symmetrical positioning. However, after finishing the treatment of my room and setting them up together with my trusty old 8020Bs for A/B listening, and spending some hours with active listening, I’ve been discovering a lot of grave issues with the listening situation that I need help with. The current sound is not good, even with GLM. 

I did as best as I could researching room acoustics, acoustic treatment and speaker positioning, which I suspect is where the issues are coming from. I do not have speaker stands for the 8351s, so my options for positioning are limited right now, as they temporarily need to be on the desktop. 

 

TREATMENT PLACEMENT

I prematurely mounted all my acoustic treatment before doing proper research on the topic or listening to my setup due to practical reasons. There’s mounted ceiling clouds and a bass trap on the left side for the early reflections for the future predicted speaker/listening positions (we used the mirror method to determine early reflection spots), not for the current speaker/listening triangle. I have four 20cm bass traps that covers the corners, but they do not go all the way to the ceiling. On the early reflection for the right side I mounted shelfs for practical reasons for using the space in the room, not sure how problematic it is (I was telling myself it would work as some kind of diffusion). The “monster” bass trap is mounted horizontally above the couch, while the rest of the traps are spaced out in available spaces in the room without much thought. 

 

HOW 8351 SOUNDS TO ME (in this room)

Comb filter ish effect around mid/high frequencies, extremely noticeable with guitar based metal music. Frequencies of issue changes when I’m tilting my head downwards and upwards, seems to be an issue with the reflection from the desktop. Not nearly as noticeable on the elevated 8020s, which sound more “open” in the mid to high register. 

Huge dips in bass registers, around 60hz and 100-120hz. 

In general very uneven bass response at listening position and the room in general, with enormous peaks at several spots often including 40hz and 80hz. 

8351 seem way more impressive and convincing at high SPL (95+)

In the position they are currently in, the 8020 actually sometimes feel flatter in the response than the 8351, and easier to tell the different elements in the mix apart. Bass feels rounder and bigger in the 8020s in a lot of mixes, but when playing electronic sub frequency dominated music they (naturally) can’t compare to the 8351 in regards to bass response. 8020 also seems to have some phase issues in the lower registers that is apparent with electronic music.

 

Thanks in advance, and sorry again for the amount of text. 

jani-oksanen, modified 1 Year ago.

RE: 8351 not sounding good, acoustic issues in treated room

Jedi Master Posts: 431 Join Date: 3/30/17 Recent Posts

Hello, and I'm sorry for late reply.

Thank you for the good background information. Could you please be kind and send few pictures of your room where the listening position and monitors are visible, and also the GLM calibration setup. If you can't attach the pictures to this forum, please send them to support@genelec.com 

You can get the GLM calibration setup by opening GLM|Help|Export Setup to Desktop| attach the .zip file from the desktop to this forum or send it to the e-mail mentioned before.

I will get back to you with any suggestions possible after that, thank you!

Best Regards,
Jani Oksanen
Customer Support Team

nordskog, modified 1 Year ago.

RE: 8351 not sounding good, acoustic issues in treated room

Youngling Posts: 3 Join Date: 8/16/19 Recent Posts

Hey jani, thank you for the reply. 

I didn't notice that my initial uploads never appeared. I updated my post with pictures of the room and the GLM EQ curves now, as well as the GLM calibration setup zip. I suppose it's pretty obvious that I need to combat my 1k dips by getting stands for my monitors and elevating them up and away from my desktop, but regarding the rest of the problems I'm quite puzzled. Working on borrowing stands for them. Looking forward to hearing more.

Best, 

Jonas Magnussen

jani-oksanen, modified 1 Year ago.

RE: 8351 not sounding good, acoustic issues in treated room

Jedi Master Posts: 431 Join Date: 3/30/17 Recent Posts

Hi Jonas,

Thank you for the great pictures and the setup file. There indeed something that could be improved on the freq. response, and the higher frequencies should be quite easily to be solved with the stands. We also have available table stands for 8351A's, that could be also good option. The table stand part number is 8000-325B. With the table stands you could also bring the monitors closer to yourself, to have more direct sound coming to your ears and less room effects. 8351A can be listened from quite short distance (50cm).

I would first solve the position of the monitors first, and then start to dig more deeply what else could be done to improve overall frequency response. Subwoofer would of course help on the low frequencies, but first, lets not hurry, and please try the stands/table stands and let us know the results! 

https://www.genelec.com/sites/default/files/media/Studio%20monitors/Accessories/23276_tischstativ_genelec.pdf 

 

Best Regards,
Jani Oksanen
Customer Support Team

costakis, modified 1 Year ago.

RE: 8351 not sounding good, acoustic issues in treated room

Padawan Posts: 38 Join Date: 2/13/19 Recent Posts

The treatment was not succesful at all. The room modes at 40 & 80 Hz are there, evident in the plot that you uploaded. With the 8351 are more evident since these speakers are better than the 8020 in low frequency response. If you had the 8020 with a sub then you would realize the same problems. The 8351 is by far a better monitor. 

To my view these are the steps for better sound:

- Better position of the 8351 (as already mentioned), this will require to move also the desk away from the front wall. See what Genelec recomends about the placement.

- Better treatment from a specialized professional with better sound material. 

- A subwoofer (close to the wall) will help to best position the 8351 (away from walls)  

 

nordskog, modified 1 Year ago.

RE: 8351 not sounding good, acoustic issues in treated room

Youngling Posts: 3 Join Date: 8/16/19 Recent Posts

Thanks for the answers, guys. I’ve been working slowly on getting to the source of this, and have managed to get ahold of König & Meyer stands. 

The bass response is flatter after putting them on stands! The node on 40hz is peaking high as always, but GLM calmly takes care of that. The right speaker has more low frequency cancellation than the left one. The comb filtering on 1000hz is gone, but it has simply moved down to about 500hz. Still very annoying. Can I do something with the desktop to remove this? 

I also talked to a professional acoustician about my situation, as it was before I got the stands. The first he was worried about was the symmetry of the room, and suggested using either concave diffusing absorbers or tilting the walls 10 degrees to break the symmetry, and fight the nodes. When I mentioned the roof height he also stressed that I should consider tilting my roof. This is not an option for me, but I figured I have some options to improve the room. 

— I can make some big standing plates made of “kryssfiner” and place them towards my front wall behind my corner traps to break the reflections somewhat. 

— I can possibly modify some of my bass traps with perforated metal plates bowed for a concave surface. (Is this appropriate for diffusion, will it break up my nodes, and how many do I need?) 

— I can add more absorbing ceiling clouds above my listening position. 

— I’m not able to buy a dedicated subwoofer, but I do have a 7050 from my previous setup still. Can I use this with some clever positioning and tuning to improve my bass? Will this be a big waste with my GLM and 8351? 

What do you think guys? What is the way moving forward? I'm attaching some new pictures of the setup and calibration. 

costakis, modified 1 Year ago.

RE: 8351 not sounding good, acoustic issues in treated room

Padawan Posts: 38 Join Date: 2/13/19 Recent Posts

Hello

Symmetrical placement is a good thing :) Using diffusing absorbers is also a good thing :) Please see what Genelec suggests about treatment and speakers positioning. This is the best that you can do. You can ask the acoustician to give you his proposal and expected results. Treating also the ceiling is a good thing but in your case, by using the 8351 it becomes less neccesary. If you also use mutliple subs elevated from the ground then it is also less neccesary. 

In the end of the day, you cannot work miracles in a small room. The standing waves cannot dissapear. The GLM is a nice solution but, as all DSPs, it cannot turn a small room into a perfect one. 

If I was in your position I would buy two 7350 subs (in case that 2 7360s are not affordable). This would help you to control the standing waves (see about mutli-sub placement). I would also increase the distance of the 8351 from the back walls. 

gus, modified 8 Months ago.

RE: 8351 not sounding good, acoustic issues in treated room

Youngling Posts: 6 Join Date: 5/28/18 Recent Posts

Don't go off generic acoustic treatment advice alone. Get rew and a measurement mic. Test where it's actually best to put treatment and position speakers not just what the textbook says. Then use glm.