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Huge dip between 150 and 300 Hz

youvebeenserged, modified 7 Years ago.

Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hello,

We are talking about a living room, not a studio...

After calibrating my 8351A monitors a see a huge dip (-10 dB) between 150 and 300 Hz. I tried moving the monitors closer and further away from the front wall but this doesn't change much.

Room dimensions: 5m wide, 4m deep, 2,5m high. The front wall is the longest (5m). I sit about 3m from the front of the speakers.

Can anyone tell me how I can find the cause for this dip and eventually how to solve it? It is a living room, so excessive treatment is not an option except for some 6 cm thick acoustic panels on critical places.

Thanks a lot,

Serge
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
Try lifting them up, how far off the floor are they? and where is the microphone in relation to the wall behind the listening position??

We usually try to get the base of the speaker above 1 meter from the floor, don't worry if the tweeter is above the ear, just tilt them down, all the big acoustic problems in rooms are LF and as you have measured usually well over 10dB...

The rear wall will typically affect much lower frequencies, if you have a solid wall.... Brick, Concrete, multiple layers of drywall then you will have big cancellations, if the baffle is 1 m from the wall you can expect to see a 80Hz cancellation, as you move the speaker further out, the cancellation will move down, 2 m will be a 40Hz cancellation, the depth of the cancellation is determined by the density of your wall.
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hello Steve,

The front wall (the one I am looking at) and the side walls are 18 mm OSB covered with 12 mm plasterboard.
The rear wall (behind my back) is natural stone, very uneven and should be a good diffuser. There is also an opening to another room without door. See picture.


The back of the monitors is about 10 cm from the front wall, the bottom at 57 cm.
My ears are about 60 cm from the back wall.

Why do you suggest lifting the monitors up? Reflection from the floor or ceiling? I tried to put two very thick and big cushions on the floor between me and the monitors but this has no effect. The ceiling then? By lifting the monitors, reflections from the ceiling will reach the listening position above my head. Correct?

Acoustic treatment is no option I think, because I've read somewhere the thickness of damping material should be ¼ of the wave length, and the wave lenght of 170Hz is about 2m!

B.t.w., how bad is a 10 dB dip between 170 and 300 Hz? If you think this is acceptable it might not be worth trying different positions of the monitors.

Thanks a lot for your help,

Serge
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
Hi Serge,

nice looking room. The reason to raise the speakers is typically to reduce the reflection from the floor, the floor is typically the densest surface in the room.

The great thing about GLM is that you can quickly and efficiently try various options. It is always worth trying various positioning, it costs you nothing but maybe an hour or two. The two things i'd play with are height of the speakers, try them at over 1 meter (you can sit them on anything sturdy, when i'm in studios and clients homes i use such things as phone books and even the speakers empty carcboard boxes, think of this time as exploritory, it is important to name your measurements accurately so you can later refer back to the results, i usually play a favourite music track to gather my subjective impression of each location)...... I'd also move your listening position about 1 meter closer to the speakers and see how that measures. You are sitting very close to the back wall so that will dominate..

Your cancellation is close to an octave wide, so it is a substantial cancellation, how it manifests in your listening and how negative it is, is a personal observation, you may find that vocals sound a little thinner than they should sound.

The problem when you measure your room is to balance all your requirements, alot of people panic and then obsess about solving all the problems, you'll never achieve that unless you have the space and budget to build a dedicated space... So, take a few measurements with different speaker/listener positions, listen to some music then make an informed decision and enjoy your new 8351's, they are a very special speaker :)
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hello Steve,

Thanks a lot for your help!

I tried different positions of the mic (left, right, up, down, backwards, to the front) nothing helps. I then took an SPL meter, generated a 170 Hz test tone and walked around in the room. Inside the potentional listening positions, the dip remains almost constant. But, when I walk more than 1,5m to the right of the listening position the tone becomes much, much stronger (from -10dB to +6dB). The height of the mic or SPL meter has almost no influence, so I think it comes from the side wall(s). Since the wave lenght is about 2m, I don't believe I will be able to do something about it.

I finally tried your suggestion of putting the speakers higher (although this generates a WAF problem), just out of curiosity. The dip is less pronounced. If I had no wife, I would put them it that position, but...

I'll try to listen to music in the zone where the 170Hz is the loudest and compare it with the sound at the real listening position. If I hardly hear any difference, or if it doesn't bother me I'll just enjoy the fanstatic speakers (they go to 25Hz in my listening room!). They sound very relaxed, even at high volume.

Regards,

Serge
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
Good work Serge,

just remember there is always a but..... I hope you enjoyed the measuring procedure and learned something about your room.

25Hz, is about where i'm at in our demo room aswell. Did you have other speakers in this room before? How do you find the 8351's in comparison??
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hi Steve,

> Did you have other speakers in this room before?
Yes, but the room has been transformed so I can't compare.

> How do you find the 8351's in comparison??
Amazing!

Most Hifi speakers I had had no problems with high and medium. Some sounded a bit harsh, others smooth, but no real problems. I had (still have) Wharfedale Opus speakers and I liked them a lot for their warm (and thus inaccurate) sound.

The highs and medium of the Genelecs are very detailed but not harsh, not as warm as the Wharfedales. No listening fatigue and I can play loud without hearing distortion (bad for my ears and neighbours).

The lows now...
Simply amazing! I have never heard lows so clean! I am amazed how low they go, but I'm more amazed by how effortless they do it. All (I say again ALL) speakers I had before had to work hard to reach low frequencies and they distorted al lot. Not the Genelecs, it's like they ask for more, more, more.

The Genelec dealer told me a customer who owned B&W Nautulus speakers (25.000 € each) sold them after he heard the 8351A's!

And now something I never expected (I was't even thinking about it when looking for new speakers)...
With previous speakers I could easily find the sweetspot blindfolded. Then moving my head only a few inches to the left or right already made a difference. Not with the Genelecs! Moving my head a foot to the left or right makes almost no difference. Great!

And last but not least: auto calibration. Works great, especially in flattening huge peaks in the lows (because my speakers are close to the walls with no acoustic treatment).

In short. The 8351A speakers are by FAR the best speakers I ever had. Good WAF too because the are so small and I don't need a 2 x 200 W amp. Cheaper and even more WAF.

I just don't understand people still buy Hifi junk, often much more expensive.

But (indeed there is always a but :-)) they are not the most beautiful speakers. I solved this by giving my back wall an industrial look: concrete print on the wall, speaker stands and turntable wall mount in rusted steel.

See: https://www.dropbox.com/s/g7oa0sagmau6wda/IMG_0298.jpg?dl=0

Serge
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hi Steve,

Another 'but'...

Some music (mastered for mp3 players ?) is so bass heavy it becomes annoying on the Genelecs. This happened never before with previous speakers.

Serge
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
One of the great things about GLM is that you can store multiple calibrations, what i'd do is save your current calibration with a new name... eg LF filter, then go in to each speakers calibration settings.... Double click each speaker, and you could simply add an LF shelf filter, say -6dB at 60Hz... You must save the file with the new name before you start editing, this way your correct calibration file remains untouched. I have setup files for clients called something like 80's music, where there is NO bass, i'll go in and remove some of the LF calibration to increase the LF level.

Is there any particular track that you can name? The track i use to listen to LF performance is a Stockfisch track by Chris Jones Track 1 from the album Moonstruck.... Long after you're gone.. It has subterranean bass.. I use foobar to identify fq issues as it has the option of displaying a spectrum analyser so you can identify the problem fq.
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hi Steve,

OK, I'll try it out.

The track I'm referring to is 'J'ai demandé à la lune' of 'Indochine'.

Have you seen my previous post regarding my evaluation of the 8351's ?

Kind regards,

Serge
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
Hi Serge,

no i don't remember seeing your evaluation...
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Just above my last post...
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hi Steve,

You asked about my experience with the 8351's... It took me some time to think about it and to write it. Would you be so kind to have a look at it? Maybe you have been very busy these days and didn't have the time to look at my post.

Kind regards and again thanks for your help,

Serge

BTW I listened to the Chris Jones track. It isn't that bad at all. The bass on the Indochine track is much worse.
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
Hi Serge,

i have read your reply, it mirrors most of my experience. The HiFi industry is simply too entrenched in selling fashion and snake oil. They have built a circular belief system that all the players are complicit in

There are many great HiFi products on the market, i have been very lucky, in the 1980's i was representing some great products, built by small specialist manufacturers, unfortunately as is still the case today, none of them talked about acoustics, there was no engineering focus, it was primarily fashion, or audio jewelry as i call it.

I remember reading a review of Genelec's S30's in "The Absolute Sound" they loved them, but criticised the fact that the amplifier was not able to be swapped... They didn't get the idea of an engineered solution...

I feel very fortunate that i was exposed to Genelec when i did, honestly i can't think of a more focused manufacturer, their belief systems are visible in every product they make, which these days is a very very rare thing.
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
Hi Steve,

It seems you have a LOT of experience in the audio/Hifi world...

One last question: can you recommend a good, no nonsense turntable and cartridge.

The Clearaudio turntables LOOK very nice, but I'm afraid I would pay a lot for 'jewelry'.
I have doubts about Clearaudio because I have the Marantz TT-15s1 (build by Clearaudio and resembling its Emotion turntable) and it sucks. Antiskating unreliable, armlift really bad, silicone belt coming of after only one month, ... When I postion the tonearm at the end of a record and lower/rise the tonearm 10 times, the tonearm moves more than an inch to the outside!

Thanks,

Serge
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
What time frame are you looking at for a new table?

There might be something very interesting coming out in about 12 months.... PM me your budget and i'll let you know if it will be suitable

My experience in turntables was from the 80's, i still own a SOTA sapphire with Zeta arm, but in that period there were some stunning turntables available. My favorites were SOTA, Oracle & The Source. I sold lots of Thorens, Logic etc..

I can't believe the current adoration of some of these mid level 80's turntables, they were OK back then but these days they are heralded as something very special...!!
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
2000 USD with tonearm. If it is worth it, I can wait 12 months :-)

Any experience with Clearaudio?

Serge
1038, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Jedi Master Posts: 340 Join Date: 4/6/09 Recent Posts
It's going to be magnitudes of order more than $2,000, so no need to wait....

For around $2,000 i'd be seriously considering second hand tables....
youvebeenserged, modified 7 Years ago.

Re: Huge dip between 150 and 300 Hz

Padawan Posts: 39 Join Date: 7/22/14 Recent Posts
:o