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Multiple Amp Questions

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BoredErica

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Let me start off by saying I have an Ultralite Mk5 and multiple NC252MPs and I love them, so personally I think you have good taste in gear. The Mk5 in particular is an incredible deal and nothing comes close for the price. I also think you are unlikely to have noise issues with most conventional speakers.

Michael
Since you are a Motu owner I figure it'd be good to ask you. There's an auction going on for KEF LS50 Metas right now that ends in 15 hours. My choice to buy better looking speakers like the Metas vs say Neumann KH80 rests in part on price. That price will go up if I need a pre-amp.

I can just use the volume control knob on the dac apparently. The problem is the subs (Rythmic f12) are powered and the speakers are not. If I turn down the volume knob on the dac, then speakers are no longer too loud but the subwoofer will now be too quiet, right? Is there a way on the Motu to get the sub and speakers to the same volume without buying a pre-amp?

edit: Friend looked at the manual and seems it's possible.
 
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mdsimon2

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I do not think a preamp is necessary.

The volume knob on the MOTU can control all 10 channels of analog output so you can easily use it as a master volume control for both the subs and speakers. The only issue with the MOTU is that it does not have a remote so you need to locally turn the knob.

I am curious about your planned setup because you mention you have 3 (and maybe 4) channels of analog sources. If so why do you need the MOTU as a DAC if they are already analog? You had mentioned a crossover so maybe you are planning on implementing a crossover in a computer attached to the MOTU?

Michael
 
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BoredErica

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I do not think a preamp is necessary.

The volume knob on the MOTU can control all 10 channels of analog output so you can easily use it as a master volume control for both the subs and speakers. The only issue with the MOTU is that it does not have a remote so you need to locally turn the knob.

I am curious about your planned setup because you mention you have 3 (and maybe 4) channels of analog sources. If so why do you need the MOTU as a DAC if they are already analog? You had mentioned a crossover so maybe you are planning on implementing a crossover in a computer attached to the MOTU?

Michael
unknown.png
This is the current plan.
Honestly I feel like my knowledge of what is going on is too low and I feel like I'm always 2 steps away from finding out I lack critical information about what I'm doing despite spending so many days reading. This is so much more complicated than plugging in a headphone into a dac/amp unit and usb to computer and calling it a day.

Yeah, the plan is to use the Motu to do the crossover.

For room EQ the solution we came up with is using the iSEMcon EMX-7150 measurement mic hooked into the the Motu I believe. Software would be Audiolense XO for $524 because apparently Dirac doesn't have a module for the sub?

So this would be the entire setup:
unknown.png

I'd probably type a thread out asking to double check my setup write after typing this post to get its own dedicated thread, or I could heavily edit the thread title and OP I guess.

Lemme know if I'm doing something incredibly stupid in my hypothetical setup.
 
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BoredErica

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The rule of thumb is to put a much of the gain as possible to the front of the chain, and therefore as little gain as possible in the speaker amp (just enough to reach your desired listening level).

You can solve the problem by placing an analog volume control (can be a passive "pre-amp" or one of the headphone/pre amps) between the speaker amp and source. The combination effectively gives you adjustable gain for the speaker amp, so you don't have to run it at full gain all the time.

However, I don't think this is necessary with your proposed setup.
Preamps can decrease a signal rather than amplify it? The Motu has a knob for volume. My understanding is ideally I'd just decrease the gain of the amp. Short of that, even if the preamp can decrease the output coming out of the dac, how would that be different from simply using the volume knob on the preamp?

I think a preamp would be a 'nice to have'. The Topping Pre90 comes with a max volume setting so I don't ever run the risk of permanently damaging my speakers and my ears. It also comes with a remote to control volume. But Pre90 only has stereo inputs... L and R... and I have 2.1 or later on 2.2 so I don't where to plug into the Pre90 from the Motu.

Zara Trench.jpg


You can still use digital volume control. Just set the analog volume so that full scale digital volume is the loudest you want to listen to.
I'm trying to Google what is digital volume control and what is analog volume control and honestly I have no idea what I'm reading anymore. Dac volume control can be digital or analog, it depends on the dac I guess? Or maybe you meant Windows volume control?

I am so confused and it's crazy how complicated speakers are vs headphones.
 
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NTK

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Preamps can decrease a signal rather than amplify it?
Sure. As an extreme example, set the volume knob to zero and you get zero output from the preamp regardless of how strong the input signal is.

I'm trying to Google what is digital volume control and what is analog volume control and honestly I have no idea what I'm reading anymore. Dac volume control can be digital or analog, it depends on the dac I guess? Or maybe you meant Windows volume control?

I am so confused and it's crazy how complicated speakers are vs headphones.
Digital volume control (including software such as the Windows volume control) works by manipulating the digital samples. To reduce the volume by 6 dB (=0.5x), multiply the values of the samples by 0.5, then send the modified samples to the DAC have it output the modified samples. This reduces the level of the signal, but not the noise, thus a volume reduction of 6 dB will result in a 6 dB drop in the SNR.

Analog volume works after the DAC by reducing the analog voltage of the DAC output. It attenuates both the signal and noise, thus does not degrade the SNR (by much). Some DACs have variable gain analog outputs that are digitally controlled. They also do not degrade SNR (by much).

However, 110+ dB SNR DAC are plentiful these days. They offer a lot of room for digital volume to work before noise becomes a real issue. Compressed music helps lessen the problem too :facepalm:.

It isn't that complicated. Once you get the few basic concepts, things will become clearer. Headphone amps are subjected to the same issues. Headphones are much easier loads than speakers. A headphone amp can be built with a few chips and powered with batteries (e.g. CMoy and O2). Speaker amps are more difficult to get right.

I highly doubt hiss will be a problem with your system. If in the unlikely event that it is, add preamp (or fixed attenuation) between the Motu and Buckeye. You can still hook up your subs to the Motu, they only reproduce low bass and not the higher frequency contents. Broadband noise from the source shouldn't be an issue. And yes, you won't be able control the volume with the pre-amp. You'll have to control the volume using your computer or Motu. The preamp only acts as a fixed attenuation to reduce the gain of the Buckeye.
 
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BoredErica

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I do not think a preamp is necessary.

The volume knob on the MOTU can control all 10 channels of analog output so you can easily use it as a master volume control for both the subs and speakers. The only issue with the MOTU is that it does not have a remote so you need to locally turn the knob.
2 questions:
1. I am aware the knob can control subwoofer or speakers. Can it control both at the same time with 1 turn of the knob?
2. If it could, would that make any sense? I just finished responding to a post in another thread about how loud subwoofers need to be a ton louder in db compared to what I measured my speakers to play at when playing music with my db meter (a-weighted). What I'm worried is if I turn the volume up or down, the bass will be louder or quieter relative to the rest of the track. Plus, sub is powered and speakers are not.
 

NTK

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1. Yes, you can. See Motu manual.
motu.PNG


2. What you (may) need is loudness compensation/correction. EqualizerAPO provides this functionality. But it only works if you adjust volume via the Windows volume control. Below is the screen shot of the loudness correction calibration screen.

EAPO.PNG
 
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BoredErica

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1. Yes, you can. See Motu manual.

2. What you (may) need is loudness compensation/correction. EqualizerAPO provides this functionality. But it only works if you adjust volume via the Windows volume control. Below is the screen shot of the loudness correction calibration screen.
An article my Sigberg Audio got me curious:
If you have a surround receiver, connecting a subwoofer is easy. In a 2-channel setup, it's often not. High-end audiophiles are a conservative crowd. Unfortunately, that means they are sceptical to "new" ideas like subwoofers and DSP / room correction - despite the fact that both can genuinely improve the sound in a 2-channel setup. Both features are a given on surround receivers regardless of price class. On stereo amplifiers, subwoofer output and active crossover support are often missing.
It's frustrating Googling these topics because the large majority of resources online assume a receiver, which cost a lot and perform relatively poorly. Sub out on a receiver is there so the receiver doesn't send any high frequency signals to the sub.

Buckeye doesn't have a sub out, but I'm connecting the sub to the Motu dac so I'm assuming I just bypassed the problem entirely.
unknown.png
So if I use Motu or some computer software for crossover, I don't use crossover on back of the sub. Therefore, signal sent to sub already needs to only have low frequency content. So, I need sub to have LFE XLR input. XLR2 does not have that, rather it has HPF out, intended for people who want to use the sub's crossover instead? So, get XLR3?
You can still use digital volume control. Just set the analog volume so that full scale digital volume is the loudest you want to listen to.
Analog volume works after the DAC by reducing the analog voltage of the DAC output. It attenuates both the signal and noise, thus does not degrade the SNR (by much). Some DACs have variable gain analog outputs that are digitally controlled. They also do not degrade SNR (by much).

I highly doubt hiss will be a problem with your system. If in the unlikely event that it is, add preamp (or fixed attenuation) between the Motu and Buckeye. You can still hook up your subs to the Motu, they only reproduce low bass and not the higher frequency contents. Broadband noise from the source shouldn't be an issue. And yes, you won't be able control the volume with the pre-amp. You'll have to control the volume using your computer or Motu. The preamp only acts as a fixed attenuation to reduce the gain of the Buckeye.
To my understanding, both Motu's volume adjustment and a preamp's volume adjustment are the same, correct? They are both analogue.

The Motu's volume knob would work for the sub and the speakers, though whether they're matched well enough is up in the air. Would a preamp also be able to adjust the sub and the speakers at the same time? I would configure Motu to do it, but will that ability transfer to the preamp or will it just be a LS50 Meta volume adjuster?

The upside of a preamp would be aesthetics, remote, and max volume control (in case of derping and blowing my ears). Motu is not super ugly but it's definitely not pretty. Something like Pre90 is way prettier. If I plug a XLR mic into the Motu it'd have to plug in the front and that's going to be super cluttered on my desk if I still need it there for the volume knob. Of course that assumes a preamp wouldn't just be a glorified LS50 Meta volume adjuster.

I suppose a keyboard with a volume knob that changes Windows volume would also work. So I use the volume knob for volume and take the Motu off my desk. There should be *some* way of having a seperate volume knob whose sole purpose is to change Windows volume if my keyboard won't have such a knob.

As always, thank you very much for your insight thus far. I really appreciate it. :)
 
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NTK

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:)
An article my Sigberg Audio got me curious:

It's frustrating Googling these topics because the large majority of resources online assume a receiver, which cost a lot and perform relatively poorly. Sub out on a receiver is there so the receiver doesn't send any high frequency signals to the sub.

Buckeye doesn't have a sub out, but I'm connecting the sub to the Motu dac so I'm assuming I just bypassed the problem entirely.

So if I use Motu or some computer software for crossover, I don't use crossover on back of the sub. Therefore, signal sent to sub already needs to only have low frequency content. So, I need sub to have LFE XLR input. XLR2 does not have that, rather it has HPF out, intended for people who want to use the sub's crossover instead? So, get XLR3?
Unless it is because of availability, in your case I see little reason for not getting the XLR3. However, the XLR2 with its non-bypassable cross-over filter shouldn't be a big issue either. Just set the cross-over (LPF) frequency to max, and let room EQ take over to resolve any cross-over slope issues.

To my understanding, both Motu's volume adjustment and a preamp's volume adjustment are the same, correct? They are both analogue.

The Motu's volume knob would work for the sub and the speakers, though whether they're matched well enough is up in the air. Would a preamp also be able to adjust the sub and the speakers at the same time? I would configure Motu to do it, but will that ability transfer to the preamp or will it just be a LS50 Meta volume adjuster?

The upside of a preamp would be aesthetics, remote, and max volume control (in case of derping and blowing my ears). Motu is not super ugly but it's definitely not pretty. Something like Pre90 is way prettier. If I plug a XLR mic into the Motu it'd have to plug in the front and that's going to be super cluttered on my desk if I still need it there for the volume knob. Of course that assumes a preamp wouldn't just be a glorified LS50 Meta volume adjuster.

I suppose a keyboard with a volume knob that changes Windows volume would also work. So I use the volume knob for volume and take the Motu off my desk. There should be *some* way of having a seperate volume knob whose sole purpose is to change Windows volume if my keyboard won't have such a knob.
It depends on how the Motu implement its main volume control. Since we know it is software configurable to which outputs it includes in its control, my guess is that the knob isn't directly connected to a volume pot that controls the signals. If it controls by adjusting analog gains, then it will work just like an analog preamp.

Since the subs are connected directly to the Motu and the mains to the preamp, the preamp is not going to adjust both the mains and the subs. The preamp will only function as a fixed attenuator to lower the effective gain of the Buckeye, thereby not amplifying the noise from the Motu as much. The (perceived) problem we are trying to solve is that the Buckeye's gain is too high, thereby magnifying the noise from the Motu to an audible level. The attenuator reduce the overall output signal of the Motu, including the Motu noise, to the Buckeye. Again, I seriously doubt this is a real problem or a preamp is needed. No need to loose sleep over this.

For convenient volume control, you can also get a usb or bluetooth volume knob (e.g. MS Surface Dial).
usb vol.jpg


As always, thank you very much for your insight thus far. I really appreciate it. :)
You are very welcome :)
 
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BoredErica

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For convenient volume control, you can also get a usb or bluetooth volume knob (e.g. MS Surface Dial).
12. I remember for headphone amps, the type of volume knob mattered (pot vs step attenuator). For a simple digital volume control I'm assuming this is irrelevant.

--

I can put a subwoofer in a few spots:

1637755089024.png

13. Do you think there's a decent chance a single sub will be enough for a flat bass response in my listening position? People talk about having two subs for seat to seat consistency but I only care about accurate bass in only one spot in the entire room. I heard a subwoofer in the corner is risky because the bass can be uneven. Maybe I could put a sub on the left wall or the right wall. There are guides to subwoofer placement but they almost always assume a home theater setup and optimize for multiple seats.

There's a lot of info in forums but there are all kinds of contradictory anecdotes/opinions. Some people claim they can always localize a subwoofer no matter what.

14. Crossover frequency: Is there any consensus on when bass can be localized? I heard somewhere if the sub is closer to the listener it's easier to localize, but I can't find the source anymore.

15. I'd like to crossover at 100hz because people say coaxial drivers suffer more from IMD, particularly if they have to play a lot of bass. I don't listen that loudly though (65db average with dba meter) so I guess this isn't even that relevant. AFAIK there is no way to measure IMD, so the most I can say is say a speaker has less IMD than the THD shown in Amir's graphs because I'm assuming IMD is part of THD.

16. If I had to get 2 subs for 1 listening position I'd assume a sub in position 1 and 2 would be best (purple numbers in the picture). At least in theory.

17. Do you think there's any real world benefit of getting the wireless version of the Metas? FR is very similar (0.1 preference score apart). I'm thinking passive crossover with adjustment via Audiolense is the best option. I'm not willing to open up the speaker to jury rig something better. The wireless Metas cost $1200 more. Subtract $500 for the amp for $700. I don't use streaming options, so it's just down to the benefits of active crossover. With Metas costing a whopping $2800 and warranty on electronics lasting only 2 years, I feel like it's a risky investment. Kef isn't Genelec who is repair 2 decade old equipment. And that's if there are no noise issues. Wireless gets benefit of active crossover, but I guess I'm managing it with their app at that point?

index.php

18. A part of me worries one day a beefy amp will blow my ears or transducers out with ridiculous volumes, be it from speakers or headphones. Is there an easy to way reliably limit how loud my speakers or headphones can get, even if say, a toddler walked over somehow and cranked the volume on the Motu or my headphone amp?
 
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NTK

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12. I remember for headphone amps, the type of volume knob mattered (pot vs step attenuator). For a simple digital volume control I'm assuming this is irrelevant.
Yes. It is irrelevant to software/digital volume control.

13. Do you think there's a decent chance a single sub will be enough for a flat bass response in my listening position? People talk about having two subs for seat to seat consistency but I only care about accurate bass in only one spot in the entire room. I heard a subwoofer in the corner is risky because the bass can be uneven. Maybe I could put a sub on the left wall or the right wall. There are guides to subwoofer placement but they almost always assume a home theater setup and optimize for multiple seats.

There's a lot of info in forums but there are all kinds of contradictory anecdotes/opinions. Some people claim they can always localize a subwoofer no matter what.

14. Crossover frequency: Is there any consensus on when bass can be localized? I heard somewhere if the sub is closer to the listener it's easier to localize, but I can't find the source anymore.

15. I'd like to crossover at 100hz because people say coaxial drivers suffer more from IMD, particularly if they have to play a lot of bass. I don't listen that loudly though (65db average with dba meter) so I guess this isn't even that relevant. AFAIK there is no way to measure IMD, so the most I can say is say a speaker has less IMD than the THD shown in Amir's graphs because I'm assuming IMD is part of THD.

16. If I had to get 2 subs for 1 listening position I'd assume a sub in position 1 and 2 would be best (purple numbers in the picture). At least in theory.
If you are only optimizing for a single listening position, 1 sub is often enough. Primary benefit of multiple subs is to help making the bass response more even across a larger area for multiple listeners. Multiple subs can also help with filling nulls which can't be done with EQ.

Placing the sub in a corner gives you the most boundary gains, i.e. highest output, but it also excites all room modes. Dr. Toole's recommendation (link below, page 1 & 2) is to try the sub in a corner first. Move it only when it doesn't work.
(You may want to read parts 1 & 2 too.)

There are different opinions on mono bass vs stereo bass. My understanding is that bass cannot be localized below a certain frequency, and 80 Hz is the "safe" (very conservative) choice -- provided that, of course, the sub is not misbehaving, e.g. generating port noise, rattling, etc.

However, stereo bass, especially when the speakers/subs are placed directly to the left and to the right, can help providing low frequency envelopment and externalization (the bass doesn't sound like coming from inside the head). The problem is that the recording must contain this stereo information. It is probably more relevant to (multi-channel) classical music (properly) recorded in concert halls. For more info on low frequency envelopment and externalization, here is one of the papers by Dr. David Griesinger.

I think crossing your LS50 Metas at 100 Hz shouldn't be a problem. Multiple ASR forum members are doing that. It is something easy enough to experiment. @mitchco has a review comparing LS50's backed by subs to monster JBL 4722's also backed by subs. He also provided binaural recordings at his listening position for comparisons.

17. Do you think there's any real world benefit of getting the wireless version of the Metas? FR is very similar (0.1 preference score apart). I'm thinking passive crossover with adjustment via Audiolense is the best option. I'm not willing to open up the speaker to jury rig something better. The wireless Metas cost $1200 more. Subtract $500 for the amp for $700. I don't use streaming options, so it's just down to the benefits of active crossover. With Metas costing a whopping $2800 and warranty on electronics lasting only 2 years, I feel like it's a risky investment. Kef isn't Genelec who is repair 2 decade old equipment. And that's if there are no noise issues. Wireless gets benefit of active crossover, but I guess I'm managing it with their app at that point?
I believe after you've EQ/highpass your LS50 Metas and backed them with subs, they will not be inferior to the LS50 wireless. The software EQ (AudioLense) in your "passive" system will give your much higher flexibility, and is more scalable if/when you upgrade your system. The LS50 wireless is great for convenience and simplicity, if that's what you are after.

18. A part of me worries one day a beefy amp will blow my ears or transducers out with ridiculous volumes, be it from speakers or headphones. Is there an easy to way reliably limit how loud my speakers or headphones can get, even if say, a toddler walked over somehow and cranked the volume on the Motu or my headphone amp?
You'll just have to exercise some restraint :)
I think there are volume limiter software available.
 
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BoredErica

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I think crossing your LS50 Metas at 100 Hz shouldn't be a problem. Multiple ASR forum members are doing that. It is something easy enough to experiment.

I believe after you've EQ/highpass your LS50 Metas and backed them with subs, they will not be inferior to the LS50 wireless. The software EQ (AudioLense) in your "passive" system will give your much higher flexibility, and is more scalable if/when you upgrade your system. The LS50 wireless is great for convenience and simplicity, if that's what you are after.
I'm open to reading material if it's several pages but these are like 33 pages. xD
1637824342208.png
I'm looking at the FR graph for f12. Each dotted line is 3.75db, so this is ~3db falloff from "normal bass volume" going from 80hz to 100hz and the F12 should have enough headroom for that. So I don't think crossing over at 100 will have any effect on real world listening. Everything goes to hell at 110 though.
1637825242614.png

Some people are very down on the LS50 Metas, saying they can't go loud and talking about dynamic range and A weighted hearing. I think listening nearfield at 65db with dba meter makes amp power, max loudness of speaker/subs really easy to manage. Plus Amir's 86db measurements were at 1M away. That's double the distance I listen at so that's how the graph would look like if I listened at 92db. I'd rather be really strict on noise rather than power.

How is normal THD tested with the Klippel? Does the speaker play a single tone at a time? Tone sweep? Noise? In real world a speaker doesn't just play a constant tone at 1 particular frequency. If it's tested with a tone sweep I think I can just discard measurements to the left of the green line. The speaker would perform 92db @ 0.5m as shown to the right of the green line, no worse or better, correct? At that point I just mentally tune out of any speaker review when on the left part of the chart below 100hz. A crossover would habe a -6 to -12db slope, so I guess performance at 90db could matter too.

You'll just have to exercise some restraint :)
I think there are volume limiter software available.
Ahh, I meant more if someone accidentally changes the volume knob on the Motu for example, and if windows volume doesn't change the next sound playing will be ultra loud. Guess it doesn't happen often enough to worry about. One day I'd like some kind of system like the Pre90 that limits the amount of power/voltage being sent from the dac before the speakers or the sub touches it. (Except the preamp won't affect the sub as already previously discussed of course so that solution would be very half baked.) It's not a big deal though and it can wait.

Such a device I suppose would be a preamplifer that can send some signals to the Buckeye while sending some signals to the sub.

--

Are you familiar with multiple measurement mics for room EQ w/ Audiolense? The UMIK-1 is $80 while the iSEMcon EMX-7150 is $350 (and out of stock). Earthworks M23 is $500. Somebody said with the calibration file given by isemcon, it's already identical to the Earthworks except for a higher noise floor that won't do anything for me since I'm measuring regular listening volumes.

Thanks
 

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I'm open to reading material if it's several pages but these are like 33 pages. xD
You don't need to finish reading them :) Take your time. For the Griesinger paper, don't even read pass the introduction section (section 1). That's enough to give an idea what low frequency envelopment and externalization are. It gets technical after that. If you can understand the paper in a single reading (I couldn't and I only read less than half of this paper myself. I gave up after section 4.), you'd already have professional level knowledge on this subject.

I'm looking at the FR graph for f12. Each dotted line is 3.75db, so this is ~3db falloff from "normal bass volume" going from 80hz to 100hz and the F12 should have enough headroom for that. So I don't think crossing over at 100 will have any effect on real world listening. Everything goes to hell at 110 though.

Some people are very down on the LS50 Metas, saying they can't go loud and talking about dynamic range and A weighted hearing. I think listening nearfield at 65db with dba meter makes amp power, max loudness of speaker/subs really easy to manage. Plus Amir's 86db measurements were at 1M away. That's double the distance I listen at so that's how the graph would look like if I listened at 92db. I'd rather be really strict on noise rather than power.
The graph is the response with the "AVR12" low-pass filter setting. I guess it means the curve is the response with a low pass filter cutting off the frequencies above 80 Hz at 12 dB/oct. If you use the LFE input, the roll off is much gentler. The should be no problem for the F12 to cross-over at up to 120 Hz. Since you'll be using AudioLense for EQ and cross-over, I'd suggest using the LFE input, and let AudioLense take care of correcting the FR.
[Edit] Forgot to attach the Rythmik F12 LFE FR curve.
f12lfe.jpg


Go read Mitcho's LS50 review and download and listen to his binaural recordings. You'll see what this little speaker can do. (Link in my previous post.)

How is normal THD tested with the Klippel? Does the speaker play a single tone at a time? Tone sweep? Noise? In real world a speaker doesn't just play a constant tone at 1 particular frequency. If it's tested with a tone sweep I think I can just discard measurements to the left of the green line. The speaker would perform 92db @ 0.5m as shown to the right of the green line, no worse or better, correct? At that point I just mentally tune out of any speaker review when on the left part of the chart below 100hz. A crossover would habe a -6 to -12db slope, so I guess performance at 90db could matter too.
Klippel measures THD using the "exponential sine sweep" (a type of frequency sweep). Professor Farina came up with this method, which let us measure THD and FR simultaneously using one test signal. See post:
The problem with the current THD measurements is that what we really want to know is at which SPL threshold distortions start to take off -- similar to the amplifier clipping point. The current method of showing distortions at 86 dB and 96 dB is OK, but not quite granular enough.

Are you familiar with multiple measurement mics for room EQ w/ Audiolense? The UMIK-1 is $80 while the iSEMcon EMX-7150 is $350 (and out of stock). Earthworks M23 is $500. Somebody said with the calibration file given by isemcon, it's already identical to the Earthworks except for a higher noise floor that won't do anything for me since I'm measuring regular listening volumes.
No. I don't have any practical experience with measurement mics. However, I think UMIK-1 should be more than sufficient from room EQ measurements. Cross-spectrum Labs offers calibrated UMIK-1. Unless you are an avid speaker builder, I don't think you need to invest in higher performance measurement mics.
 
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The graph is the response with the "AVR12" low-pass filter setting. I guess it means the curve is the response with a low pass filter cutting off the frequencies above 80 Hz at 12 dB/oct. If you use the LFE input, the roll off is much gentler. The should be no problem for the F12 to cross-over at up to 120 Hz. Since you'll be using AudioLense for EQ and cross-over, I'd suggest using the LFE input, and let AudioLense take care of correcting the FR.
Ahh. I ask because Rythmik suggests buying the 12g for crossing at above 80hz, but it costs more and is far less good looking. Looking at your FR graph though it seems like the subs can crossover all the way up to 150, maybe even 200hz if one doesn't listen loud.

Go read Mitcho's LS50 review and download and listen to his binaural recordings. You'll see what this little speaker can do. (Link in my previous post.)
I did. He mentioned comparing wide directivity to narrow directivity speakers. And he was using the old LS50 which measure a good bit worse!
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If I get a good deal on some Metas the return window might end before Buckeye can arrive. To test if the Metas are defective I need a working amp and dac. Buckeye is $500 with a lead time towards end of Februrary. Topping PA5 is $321 while being available in 2 weeks. The back has TRS, which is just dandy since Motu out is also TRS.

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Should work right? Power graph here to save you time:
At 50mW, the Buckeye is at -76db, whereas the Topping seems to perform at -86db. Topping has a fixed gain of 19.1, vs Buckeye's 25.5db gain. In addition, the Topping has a volume knob. Is it analogue volume control, like a preamp? Power is more limited at 50w vs 100w, however it seems like even with 84db efficiency (85db spec rounded down), listening at 1.5ft, even not close to a wall, I can hit 100db+. Price is a lot lower. Only downside I can see is there's a power brick which adds clutter.

Motu is also out of stock until mid Feb. If I get a deal on LS50 Metas I need to be able to test that it functions. I need a way to connect O2/Odac combo unit into a power amp. O2/Odac has quarter inch out, so I use quarter inch to TRS cable?

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It has always confused me how some people call the KEF speakers narrow dispersion/directivity (those two terms mean the same thing right?).

KEF LS50 Meta Charts:
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Revel M105 measurements:
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Horizontal beamwidth for Revel (which people say are wide dispersion) is 70 degrees, but for LS50 Meta is only 50 degrees. Looking at sound power and early reflections DI they look similar. Yet Mithco and some others said LS50 Metas are wide dispersion. I'm confused on whether LS50 Metas are narrow or wide dispersion and how I can tell based on the graphs.

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When sitting super close to a typical speaker with tweeter at ear level, the speaker won't sound correct, right? The drivers won't 'integrate'? I need to be a certain distance away. My understand is crossover frequency between woofer and tweeter can have an impact on this, as is driver size. Also I think a speaker like LS50 Meta should integrate at a very short distance due to tweeter and woofer being in the same spot. However it seems like Amir's Klippel doesn't entirely agree?

Side note, @amirm, can the Klippel state at what simulated distance the measurements are being taken at after doing the extrapolation? Meaning, can it tell us how far away one needs to be for the drivers to fully integrate?
(Amir https://www.audiosciencereview.com/...helf-speaker-review.11144/page-12#post-317201):
It can and it does. I don't currently have confidence in what it is showing however. As I test larger speakers, I can better tell how good that metric is. Here is what it looks like for KEF LS50 for example:
View attachment 47994

The highest order function flattens at about 0.6 meter where I have drawn that arrow. That means from there on we are in far field. Someone less lazy than me can do the math and tell us if this is correct.
 
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mdsimon2

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One area that is a bit unknown with the PA5 is frequency response in to complex loads. Hypex shines in this area as it has frequency response that is very independent of load which is not often the class D amplifiers.

Otherwise I agree that the PA5 seems ideal for a near field setup.

Michael
 
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BoredErica

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One area that is a bit unknown with the PA5 is frequency response in to complex loads. Hypex shines in this area as it has frequency response that is very independent of load which is not often the class D amplifiers.

Otherwise I agree that the PA5 seems ideal for a near field setup.

Michael
Which of these graphs are you referring to from the Buckeye review? Is it a practical concern?
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mdsimon2

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For some reason Amir stopped measuring amplifier frequency response in to complex loads. If you look at his Behringer A800 review you can see the frequency response deviation at higher frequencies.


@pma recently did some investigation comparing a UCD180 (precursor to Ncore) to a TPA3255 based amplifier which showed the TPA3255 amplifier had load dependent frequency response but the UCD did not.


Michael
 

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I did. He mentioned comparing wide directivity to narrow directivity speakers. And he was using the old LS50 which measure a good bit worse!
--
If I get a good deal on some Metas the return window might end before Buckeye can arrive. To test if the Metas are defective I need a working amp and dac. Buckeye is $500 with a lead time towards end of Februrary. Topping PA5 is $321 while being available in 2 weeks. The back has TRS, which is just dandy since Motu out is also TRS.

At 50mW, the Buckeye is at -76db, whereas the Topping seems to perform at -86db. Topping has a fixed gain of 19.1, vs Buckeye's 25.5db gain. In addition, the Topping has a volume knob. Is it analogue volume control, like a preamp? Power is more limited at 50w vs 100w, however it seems like even with 84db efficiency (85db spec rounded down), listening at 1.5ft, even not close to a wall, I can hit 100db+. Price is a lot lower. Only downside I can see is there's a power brick which adds clutter.

Motu is also out of stock until mid Feb. If I get a deal on LS50 Metas I need to be able to test that it functions. I need a way to connect O2/Odac combo unit into a power amp. O2/Odac has quarter inch out, so I use quarter inch to TRS cable?

--
It has always confused me how some people call the KEF speakers narrow dispersion/directivity (those two terms mean the same thing right?).

Horizontal beamwidth for Revel (which people say are wide dispersion) is 70 degrees, but for LS50 Meta is only 50 degrees. Looking at sound power and early reflections DI they look similar. Yet Mithco and some others said LS50 Metas are wide dispersion. I'm confused on whether LS50 Metas are narrow or wide dispersion and how I can tell based on the graphs.
The Topping PA5 does appear to have a lower self noise than the Buckeye NC252. For desktop listening distance, I believe the PA5 should be sufficient.

The PA5 can output 100 W into 4 ohm (<0.01% THN+N), which equates to 20 Vrms. With sensitivity of 85 dB/2.83V, the loudness unclipped volume at 1 m would be 85 + 20*log10(20/2.83) = 102 dB. Two speakers (and neglecting room gain) will raise it to 105 dB. Using my own personal rule-of-thumb, it will be adequate for 82 dB average listening volume, which IMHO should be plenty loud enough. The wall wart is an annoyance indeed.

To connect your ODAC/O2 combo to the PA5, an adapter cable like this one should work, although probably not optimal, since it shorts the negative side of the balanced input of the PA5 to ground. You'll probably have to make your own cable if you feel absolutely have to "do it right".

The M105 is considered very wide dispersion, and the LS50 Meta is only slightly narrower in comparison. For reference, the JBL M2 is considered medium dispersion, and from Erin's measurements, it is about +/-30-35 deg. Mitchco's JBL 4722's are narrow dispersion intended for cinemas.

JBL%20M2%20%28Crown%20iTech%205000%20Amp%3B%20M2%20Base%20Configuration%29%20Horizontal%20Contour%20Plot.png


When sitting super close to a typical speaker with tweeter at ear level, the speaker won't sound correct, right? The drivers won't 'integrate'? I need to be a certain distance away. My understand is crossover frequency between woofer and tweeter can have an impact on this, as is driver size. Also I think a speaker like LS50 Meta should integrate at a very short distance due to tweeter and woofer being in the same spot. However it seems like Amir's Klippel doesn't entirely agree?
Here is Genelec's speaker distance chart. For their coax based Ones (83x1), the smaller ones are good for distances >0.5 m. I'd expect the LS50 Metas to behave similarly.

correct-monitors-spl-chart.jpg


Please also note that KEF's are best listened to at >10 deg off-axis. Please see this post by Dr Jack Oclee Brown (VP of Technology at KEF).
 
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