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Used Kef Reference 3 Meta with reduced warranty

Flexecutioner

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Based on your picture and the size of the Ref 3 Metas, I'm assuming the front baffle of the speakers is ~95 cm from the front wall. This would result in a SBIR null at ~90 Hz which is a pretty crucial area for perceived bass response. I'd try moving the speakers closer to the front wall to get more boundary loading and to move that SBIR frequency higher.
 
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soerenssen

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Based on your picture and the size of the Ref 3 Metas, I'm assuming the front baffle of the speakers is ~95 cm from the front wall. This would result in a SBIR null at ~90 Hz which is a pretty crucial area for perceived bass response. I'd try moving the speakers closer to the front wall to get more boundary loading and to move that SBIR frequency higher.
I haven't measured it yet, but I've been playing around with the placement in the last few hours. The best position is the middle of the carpet: good imaging / soundstage, not overwhelming but nice bass, so I kept pulling them away from the front wall, closer to the counch. Now the baffle-to-front wall distance is 105cm. The deepest bass is behind the couch, but it's overwhelming and everything else is worse compared to the "middle of the carpet" position. I think I'll will pull them even further away from the wall (or pull the couch closer to increase the distance from the rear wall), but my listening distance will be below 3m. I don't know if that's ideal.
If I push them closer (30 to 40 cm) to the front wall, they sound off, not so lively, I don't like it, even if brings some compansation in the low frequencies.

The idea is now to find the best possible position before I measure and do only minimal correction in Dirac.
 
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soerenssen

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I changed the bottom port on both speakers from long tube to short tube. Bass sounds a bit nicer now.
Their current distance is 2.90m, listening distance is 2.60-2.80m, the shorter the better (more impactful) the bass is.
 
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soerenssen

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How did you calculate that SBIR 90Hz null value?
I tried to put the values into an SBIR calculator, although the distance to the side wall in my case it's not the same for the front and the left speaker. FL is 84cm from the left wall (glass) so it would have an immediate reflection, I used this value in the calculator. FR is 230cm from the kitchen furniture on the right side.

Screenshot 2023-08-22 at 15.27.54.png


What kind of acoustic materials do you suggest for such a room?
 

fineMen

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Based on your picture and the size of the Ref 3 Metas, I'm assuming the front baffle of the speakers is ~95 cm from the front wall. This would result in a SBIR null at ~90 Hz which is a pretty crucial area for perceived bass response. I'd try moving the speakers closer to the front wall to get more boundary loading and to move that SBIR frequency higher.
I could only rarely confirm the predictions for so called boundary loading and 'nulls'. Times I was lucky but then that 'null' originated in something else. I think the ray tracing approach (mirror sources at best) cannot substitute a full (numerical) integration of the differential equation.
 

Flexecutioner

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The first "Front wall" x "Null" is the number I was referencing if you are using that calculator. It is based on the 1/4 wavelength since it reflects off the back wall and arrives 180 degrees out of phase with the wave from the front of the driver. The formula boils down to 85.75/(distance in meters from front baffle to rear wall) = first SBIR null.

I'd see how far speaker position and EQ get you before worrying about acoustic treatment honestly. Bass traps for low frequencies need to be quite large.
 
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soerenssen

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The first "Front wall" x "Null" is the number I was referencing if you are using that calculator. It is based on the 1/4 wavelength since it reflects off the back wall and arrives 180 degrees out of phase with the wave from the front of the driver. The formula boils down to 85.75/(distance in meters from front baffle to rear wall) = first SBIR null.

I'd see how far speaker position and EQ get you before worrying about acoustic treatment honestly. Bass traps for low frequencies need to be quite large.
What is 85.75?
What if the speakers are toed in slightly? (Do you measure the shortest or longest baffle distance?)
Will that cancellation at 90Hz be effective everywhere in the room or only in the listening position?
 
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soerenssen

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Can it be bass suckout caused by the rear wall?

From http://arqen.com/acoustics-101/speaker-placement-boundary-interference/:
"Small rooms typically have several nulls below 300 Hz. Nulls of 30dB are typical! Ideally, your listening position should be at least 10 feet (3 meters) from the rear wall behind you, placing the quarter wavelength cancellation frequency below 30 Hz. If you don’t have that kind of space in your room, place low frequency absorption (bass traps) on the rear wall to reduce the energy of rear wall reflections."
 

Flexecutioner

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85.75 is 1/4 of the speed of sound in m/s (343). I'd measure to the center of the baffle, but the difference will be minimal. Your listening position will certainly have a large impact. Like others have suggested, taking measurements and experimenting with your setup will be the most valuable feedback.

You can mess around with the Room Sim in REW to get a general idea of how speaker placement and listening position impact bass response. I wouldn't use it to try to optimize speaker placement or seating location in a real room, but it's a great way to visualize the theory of these effects and interactions.
 
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soerenssen

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I talked to Tibor from Apollon Audio, he recommended replacing the stereo NCx500 with two mono blocks or - for even more bass control and better musicality / warmer sound - with a Purifi 7040SA in dual mono config. Does such an upgrade have the potential to overcome the room issue that I have (40A instead of 27-28A)?
 
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bodhi

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I talked to Tibor from Apollon Audio, he recommended replacing the stereo NCx500 with two mono blocks or - for even more bass control and better musicality / warmer sound - with a Purifi 7040SA in dual mono config. Does such an upgrade have the potential to overcome the room issue that I have (40A instead of 27-28A)?
So you are still doing everything else but taking the measurements? It takes 5 minutes.
 

fineMen

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So you are still doing everything else but taking the measurements? It takes 5 minutes.
The KEF Rs and Refs are optimized to be equalized at least in the bass--as every decent speaker should be. They sound at least o/k-ish without, but to get to the top needs this step to be taken. In case that is too high of a threshold, I'm not sure what to recommend. It's like driving a fully competitive Tour De France bicycle but never switching gears.
 

MarkS

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I talked to Tibor from Apollon Audio, he recommended replacing the stereo NCx500 with two mono blocks or - for even more bass control and better musicality / warmer sound - with a Purifi 7040SA in dual mono config. Does such an upgrade have the potential to overcome the room issue that I have (40A instead of 27-28A)?
No. This has to do with speaker placement and room effects, nothing at all to do with the amps.

I would try putting the couch against the back wall. This is how my listening room (similar size) is set up. You will still need to equalize the bass, but since all the front-to-back modes are maximized at the wall, equalization can be done with mostly cuts.

Listening at the back wall supposed to be a bad idea, but it sounds good to me (after equalization by Room Perfect), and at least one speaker manufacturer, Audio Physic, recommends it (or at least once did, I'm not sure if they still do).
 
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soerenssen

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The KEF Rs and Refs are optimized to be equalized at least in the bass--as every decent speaker should be. They sound at least o/k-ish without, but to get to the top needs this step to be taken. In case that is too high of a threshold, I'm not sure what to recommend. It's like driving a fully competitive Tour De France bicycle but never switching gears.
What do you mean by switching gears: using EQ / proper placement or upgrading pre-amp/amp?
 
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soerenssen

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No. This has to do with speaker placement and room effects, nothing at all to do with the amps.

I would try putting the couch against the back wall. This is how my listening room (similar size) is set up. You will still need to equalize the bass, but since all the front-to-back modes are maximized at the wall, equalization can be done with mostly cuts.

Listening at the back wall supposed to be a bad idea, but it sounds good to me (after equalization by Room Perfect), and at least one speaker manufacturer, Audio Physic, recommends it (or at least once did, I'm not sure if they still do).
I will definitely try this. It's either (1) pulling the speakers away from the front wall and at the same time bringing the couch more to the center, away from the rear wall, or (2) pushing the speakers to the front wall and at the same time pushing the couch closer to the rear wall. I prefer (1) because it looks weird if the couch is pushed all the way to the rear walls, it's too far from the TV and my workplace / desktop is in the rear left corner so the couch would block the path.
Anyways, today I'll measure and report back.
Thanks for all the help so far!
 
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phoenixdogfan

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Thank you!
Is the MiniDSP Flex + Audiophonics NCX500 combo good enough to pair with these Kefs or am I missing something? Btw, I was told by the salesman in that local hifi shop where I auditioned that R11 and Ref5, that pairing an analytical class D amp with analytical speakers like the Kefs is a bad idea and I should use something more musical like Marantz or Denon.
Let's put it this way: pairing an accurate, correctly designed speaker, with accurate correctly designed electonics is always a great idea. All the stuff audio store cowboys lay on you about mixing and matching colorations of components is driven by what they need to clear out of inventory that month and/or what kind of markup they can charge on the respective products. It's nothing more than that.

The NCX 500 will work perhaps as well as any amp could work, and ditto for the Flex. I use a Purifi Class D Eigentact to drive my LS 50 metas, and no problem with anything being "too analytical". Unless you consider electronics with no audible distortion or noise whatsoever too analytical!

Btw, I've been an audiophile for 48 years, owned at least ten different speaker systems, and never had a single speaker fail in the field unless I accidentally caused a pointed object to go through a cone while drunk. And only once.
 
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