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Dutch & Dutch 8Cs

Martijn Mensink

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From a user perspective, I don't find the current volume control satisfactory as a complete solution. It always takes some seconds to load when I load the control interface, and that becomes cumbersome if changing volume a lot. It's fine for ego listening if one just puts on an album and keeps the volume, but for playlists, multiple users etc, it doesn't quite cut it IMO.
I agree. The big benefit of the browser-based app is that it works on many different platforms. That means it was much quicker to develop. We're now developing a native app that will be easier to use, easier to access and quicker to respond.
 
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Martijn Mensink

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I seem to recall that enabling Roon remains in a yet to be delivered upgrade. It'd be interesting to know how volume control will work once Roon is enabled as I guess that there is the potential for volume control to be executed from the Roon app. That would make for an excellent single source set-up.
Roon is now working in beta-mode in the 8c's of a small group of testers. We are in the process of preparing a pair of 8c's to be sent to Roon for testing. Once they've given their sign of approval, we will release a firmware update that includes Roon.

The implementation of Roon in the 8c's has taken a lot longer than we originally expected. The implementation of the Roon SDK was quite straightforward and done within a week, but the difficultly lies in the fact that Roon does not guarantee perfect audio sync between different endpoints. That is usually - for instance within a multiroom system - not much of a problem, because small differences in latency aren't really audible. In a stereo system it messes up the stereo-image. Even a difference in latency of a couple of samples can pull a center image away from dead center. We've now achieved a perfect sync between the two speakers in a stereo system.

Roon takes control of the 8c's internal volume control. When you start a stream in Roon, the 8c's are automatically switched to Roon as an input. When you stop the stream, the 8c's automatically go back to the source you were playing before you started the Roon stream.

Anyone know if the the on-board volume control in the digital domain? The reason for asking is that I'm a bit worried about late night listening where one might be -30 or 40dB (in which case perhaps it'd be better to use an off-board analogue volume control and accept the A/D conversion).
Yes, the volume control is done in the final stage of the DSP, in the digital domain. We're using an excessive number of bits (I'm not sure, but I believe it's about 56) and dithering to make the volume control inaudible.
 

Martijn Mensink

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Regarding the Roon ready, I am hoping 8C could accept data via Ethernet in the coming future, and also use Ethernet connection between the 2 speakers, instead of only AES nowadays.
With the Ethernet connection, this is much more convenient to feed in data from a network, i.e. router, switch, and we could make use of app from a tablet to control the speakers and surf music.
Actually, this is how Roon works. The Roon server is connected to your local network, the 8c's are connected to the local network, that's all you need. We are big proponents of audio over ethernet (in many ways it's better and more convenient than for instance USB or AES). Roon is just the start.
 

Martijn Mensink

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Martijn

It sounds as if there is a lot of development both on the software and hardware (external box) elements of the speakers. Have you got a sense as to what s/w features will come available when? (I'm keen to understand the plan for integration with subwoofers but also other developments). And, as one involved in s/w, I get that dates are difficult and priorities change. And is there definition of the functions that will be supported in the external control box that Keith mentioned?
That's a good question Andrew. As you say, it's difficult to give dates. We are fortunate to have a team of very smart and talented software engineers. In the past we pressed them for estimates and we've communicated expected release-dates, but we've learned that what we call 'unknown unknowns' always get in the way. You're right that we do have a list of priorities. I'm not going to share the entire list, but I'm willing to share what we are working on right now. Roon is our top-priority. It is close to completion. Besides that we are working on native apps for Android, iOS and Windows. Subwoofer integration is on the list, but a bit lower in priority.

Edit: One comment on the speakers is that the bass is plentiful. I'm using these in large 21' x 25' room that isn't sealed and getting good bass at normal listening levels which is improved via use of DSP / EQ. My plan was, when I get to adding subwoofers, was to high pass the 8c and utilise mono-subs for all bass <80Hz but now not utilising the 8c bass seems like a waste. The reason that I mention all this is that if one takes this view it likely impacts the design of the subwoofer integration DSP - perhaps, for example, have a setting such that the on-board subs and sub output both utilise a mono signal to simplify integration with off-board subs.
The feedback we get from most users is that the bass is indeed plentiful. Some people who first intended to add subwoofers to their setup have told us they changed their minds. That, plus the fact that properly setting up a multi-sub system is quite difficult, have led to the decision to prioritize other features for now. It's definitely still on there though!

The best way to do a multi-sub setup with the 8c's, is with subwoofers that have an equally flat frequency response and phase response as the 8c's. Then you get the most predictable, closest to textbook behavior. A matching subwoofer is on our hardware-development 'backlog'. The control box you mentioned is higher in priority. For that box I've actually learned a lot from the discussions in this topic and the topic about a pre-amp for active digital / analog speakers. I'm planning to join that topic at some point in the near future as well.
 

Martijn Mensink

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I spent quite a bit of time in the Dutch & Dutch room at Cranage on Sunday and I'm impressed. A bit disappointed that the dealer played so much electronic/dance music which for me made it more difficult to assess the speakers. But when they did finally play some decently recorded vocals I was struck by the clarity and complete lack of smearing.
It's difficult to please everybody with the choice of music, I guess! Many people actually enjoyed to hear something other than the usual and this music sound quite impressive on the 8c's, but I do get what you mean.

The wide soundstage was very evident (I was sitting slightly to the left of centre with some folks in front to the right, but not blocking the right speaker) and instrument placement was excellent. Bass was powerful and very well controlled. They simply played music with an overall cohesiveness that didn't call attention to the speakers at all. For all their clarity, punch and detail I couldn't see these speakers bringing about any fatigue in long listening sessions. There was nothing else at the show that came close to them...all IMO, of course.

Martijn - you can send me the cheque now ;)
You never sent me your details! Please drop me an email :D .

Actually, I had a really enjoyable chat with Martijn who assured me that if I could sit in the sweet spot the auditory scene would be even better - I did return later to try to do this, but he had left to catch his plane and the room had even more folks than the first time - and the dealer was playing electro once again! Never mind, they were the highlight of the show for me.
On the surface they're very different, but there are some similarities in the design approach of you Linkwitz speakers and the 8c. I love the LX521 as well!
 

Martijn Mensink

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Yesterday in a hifi show when I audited the 8C, I was standing on the right side of the right speaker - completely outside of the sweet spot, not even in between two speakers, and yet I was impressed by the sound and image created by the 8C. These speakers does very well off-axis, it is amazing and I couldn't imagine what it would sound like if I am sitting in the sweet spot.

I might have another chance to listen to this pair in August, hopefully I can get closer to the sweet spot next time. The dealer's showroom was the most popular one in the last two hifi shows, it was full of people and I gave up trying to get a good position. Now I regret its.
I'm happy to hear you were impressed!

By the way, I am surprised that the 8C doesn't come with a remote... I was expecting the 8C can completely replace all my gears.
The 8c as a complete system, that is the idea. We're gradually working towards the realization of that idea. Streaming is an important step, native apps with a great UX is the next. The 8c you buy today, keeps getting better over time.
 

Martijn Mensink

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I don't, to be honest, see the web app as a solution except for the case of a sole, enthusiast, listener. If it was just me, with Roon, then it'd be a fine solution made better with a native app. Our situation, though, sees the entire family using and enjoying the speakers which have to support a wide range of A/V sources as well as streaming. To this end, we're using a mini-DSP DDRC-22D as a digital pre-amp that allows for volume and input to be controlled by a simple universal remote programmed with activities such as "listen to music" or "watch Apple TV". (The A/V sources go direct to TV with optical output sent to the mini-DSP and Auralic Aries is connected direct to mini-DSP as a Roon end-point.) All this is simple enough for family use with limited support. I'd love to ditch the music streamer, and control volume in the 8c, but I don't see this as being practical via the web-app - it would have to be via a universal remote control or integrated into a smartphone app that support other A/V equipment to win over the living room.

P.S. The idea of the D&D control box is a solution to this dilemma but has it's own issues. Support for remote controlled volume and input switching, as well as sample rate conversion, are the base requirements for a ticket to play. How, though, does it differentiate against pre-amp options whether these be digital (not many) or analogue (DAC/pre or AV Pre-Pro)? I'd imagine that one advantage would be that it'd be able to control the 8c volume natively rather than applying digital volume control earlier in the chain or requiring a A/D from an analogue pre-amp - but we've heard that the latter isn't a problem. So, whilst I'm in the market, it'd be good to understand the thinking on this box.
All good points, Andrew. Based on the conversations I've had with many of our hifi customers, I believe Roon plus a decent native app that can be accessed from the lock-screen of your phone to change inputs and volume, would be a great low box-count solution for most people. If you have many different sources, a device such as your miniDSP or an AV-processor might be the most convenient solution. I'm not familiar with this specific miniDSP, but if it's well-designed, it should sound very good with the 8c's, just like any decent AV-processor with (preferably) a balanced output. Unfortunately, there don't seem to be too many digital preamps with an AES output on the market.

For many people an AV-processor may be the best solution with a pair of 8c's. We are currently working on a more purist solution that keeps the signal in the digital domain all the way up to the DACs in the 8c's. The preferred way to connect between this control box and the 8c's would be either AES or ethernet. With the latter way of connecting, the control box doesn't even need to be placed close to the 8c's themselves, it just has to be on the same local network. We're yet to decide on the precise design spec.
 

matthijs

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Yes, the volume control is done in the final stage of the DSP, in the digital domain. We're using an excessive number of bits (I'm not sure, but I believe it's about 56) and dithering to make the volume control inaudible.
It's 24 fractional bits (+ 8 integer bits), which is generously sufficient for volume control (indeed for most signal processing that does not involve feedback) and puts the quantization noise floor around -144 dBFS. Dithering is not relevant when you have this much resolution and not used. 56 fractional bits is used for feedback paths of recursive filters.
 

dc655321

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I'm hoping that some of the forum folks here can shed some light on how the 8c
bass response is formed.

Conventional wisdom goes something like, "don't place your speakers too near the
front wall (< 1.5m)". With conventional speakers, front-firing woofers radiate
directly at the listener, followed by the wave reflected from the front wall.
These reflected waves are 2*(speaker_depth + front_wall_distance) [m] out of phase
with the front-launched wavefronts. Naturally, interference abounds.

The 8c are designed to be used maximally close to the front wall. So, I have to
assume that the rear-facing woofers fire (2*front_wall_distance +
speaker_depth)/c ahead of the (assumed) time-aligned front-facing speakers.

Questions (no particular order):
1) From a sealed speaker enclosure, how strongly is the woofer back-wave
(anti-phase) typically attenuated? My intuition says anti-phase wavefront
leakage must cause some interference in the 8c.

2) What are the consequences of putting ordinary (non-8c) sealed speakers reasonably close
(~0.1-0.2m) to the front-wall boundary?

3) What, if any, are the compromises present in the 8c sub-woofer design? Given
their small-ish size, I assume efficiency takes a big hit (thus the copious
amplifier power on tap), but what else?

BTW -- kudos on the acoustic design. It's brilliant.

Edited: strike-throughs mysteriously added to post. WTF?
 
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andreasmaaan

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I'm hoping that some of the forum folks here can shed some light on how the 8c
bass response is formed.

Conventional wisdom goes something like, "don't place your speakers too near the
front wall (< 1.5m)". With conventional speakers, front-firing woofers radiate
directly at the listener, followed by the wave reflected from the front wall.
These reflected waves are 2*(speaker_depth + front_wall_distance) [m] out of phase
with the front-launched wavefronts. Naturally, interference abounds.

The 8c are designed to be used maximally close to the front wall. So, I have to
assume that the rear-facing woofers fire (2*front_wall_distance +
speaker_depth)/c ahead of the (assumed) time-aligned front-facing speakers.

Questions (no particular order):
1) From a sealed speaker enclosure, how strongly is the woofer back-wave
(anti-phase) typically attenuated? My intuition says anti-phase wavefront
leakage must cause some interference in the 8c.

2) What are the consequences of putting ordinary (non-8c) sealed speakers reasonably close
(~0.1-0.2m) to the front-wall boundary?

3) What, if any, are the compromises present in the 8c sub-woofer design? Given
their small-ish size, I assume efficiency takes a big hit (thus the copious
amplifier power on tap), but what else?

BTW -- kudos on the acoustic design. It's brilliant.

Edited: strike-throughs mysteriously added to post. WTF?
I’m not familiar with the rearward polar response of the 8Cs, so I'll mostly restrict this to attempting to answer the non-8C related question. Sorry if any of the following is repeating what you already know ;)

The short oversimplified answer is that with a short distance from the speaker to the front wall you’ll get a broadband 6dB boost from the low bass up to approximately the frequency of wavelength 4 times the distance from the front wall to the acoustic centre of the woofer, and then a series of decreasingly severe higher frequency nulls (eventually resembling more a comb filter effect) up to the point at which the speaker stops projecting significant rearward energy. At 20cm, for example, with typical box speakers this will most significantly result in a nearly 6dB boost from 0 Hz to just under 430Hz, then a very deep null at around 430Hz, then further nulls (of decreasing severity) higher up in frequency, until eventually the response flattens out at the point at which the speaker projects so little sound rearward that interference between the front wave and the reflected back wave becomes negligible.

The longer answer is as follows:

Firstly, the distance from the speaker to the front wall determines the extent to which the direct sound and the reflected sound from the front wall interact at the listening position.

The shorter the distance, the closer in level the reflected wave from the rear wall will be to the direct wave from the woofer at the listening position. So, as the speaker is moved closer to the front wall, the influence of the reflected rear wave on the frequency response at the listening position becomes more severe. At a distance of 20cm (assuming a typical say 2m+ listening distance and a purely reflective front wall) there will be a difference of only one or two dB between the direct and reflected waves, meaning maximum interaction. The first result of this will be a large broadband boost at the listening position to frequencies up to the frequency 4 times the wavelength of the distance from the front wall to the woofer's acoustic centre.

Secondly, the distance from the front wall determines the frequencies at which that the rear reflected wave and the direct wave interact (sum and null).

To illustrate, take your example of a 20cm distance from the front wall (I'll assume this is 20cm from the acoustic centre of the woofer). 20cm is 1/4 wavelength of about 430Hz. So at this frequency (assuming the speaker is omni, which it will more or less be at this frequency if it is a conventional box speaker), the reflected wave will bounce back and combine 180° out-of-phase with the direct wave, creating a deep null. The same will occur at various higher frequencies if the speaker is projecting significant rearward energy at those frequencies too. Meanwhile, in between these nulls the reflected wave from the front wall will be in phase with that of the direct wave, resulting in summing (i.e. narrowband boosts of up to 6dB).

If the reflected wave is almost as high in SPL as the direct wave (which it will be if it's travelled only 20cm before bouncing back, and if the front wall is basically reflective), the cancellations at these frequencies will be almost absolute. Here is a graph which assumes a listening position of 3m, an omni source at all frequencies (obviously false at mid-high frequencies for a monopole box speaker but used here to illustrate), and a purely reflective front wall. You see massive nulls beginning at the frequency with a wavelength of 4 x 20cm, i.e. 430Hz. This first null in particular will tend to destroy the midrange.

1535623613673.png


As we move the speaker away from the front wall, the difference in SPL between the direct and reflected wave increases, meaning that (1) the extent of the interaction becomes less extreme, and (2) the frequency at which the waves begin to interact decreases. Meanwhile, the distances between peaks and nulls at any given frequency above the 1/4 wavelength frequency become closer together, so that the peak/null behaviour begins to resemble a comb filter at a lower frequency.

Here is the same idealised example (omni source, 3m listening position, purely reflective front wall), but now with a distance between the woofer's acoustic centre and the front wall of 1m. As you can see, the overall boost is now not as great, and the nulls now begin lower in frequency, are far less pronounced, and closer together at any given frequency. The frequency of the first null is now that of wavelength 4 x 1m = approx 86Hz.

1535623781374.png


What these idealised graphs don't show (among other things) is that, in reality, a monopole box speaker will tend to become less omnidirectional as frequency increases, i.e. the differences in SPL between the direct wave and the wave reflected off the front wall will tend to become greater as frequency increases. In most cases, a typical modern narrow-baffle closed box speaker will be truly omni only up to about 300-500Hz depending on baffle width and speaker depth, and will project very little rearward energy above around 1 or 2KHz, so there will be little interaction above these frequencies. In other words, the graphs above will begin to look less boosted and less ragged above around 300-500Hz. This transition range in which there is some interaction, although not as much as the graph assumes for an omni source, will tend to continue up to about 1-2KHz, or whatever frequency the speaker stops producing significant rearward energy.

In terms of how to deal with this, as a general rule, for decent midrange reproduction you’d want to keep the distance from the woofer(s) to the front wall at least around a metre, which should reduce the magnitude of the peaks and nulls to under 6dB in most real-world cases, and keep that first widest and deepest null down below the Schroeder frequency (more on this below). In a studio context, I also try to solve this problem two additional ways. Firstly, I use broadband front wall absorption that extends in frequency to below the 1/4 wavelength distance to the woofer (or the point at which the woofer crosses to the subs, whichever is higher). Best is usually dense, thick rockwool with an air gap between it and the front wall (obvs not practical at home). Secondly, I try to ensure that the cancellation distances between the woofer and each of the front wall, ceiling, floor and sidewalls to the listening position are all different; remember that a similar effect occurs not just with the front wall, but with all the room's first reflection points. By ensuring these distances are all different from each other, nulls due to out-of-phase first reflections are spread out in frequency (this is still difficult, but often possible, in a home context).

Use of subs is another way to improve the situation, since these can be placed along room boundaries so that there is no cancellation within their operating frequency range from reflected waves bouncing off first reflection points (the frequencies reproduced by the subs have long wavelengths so the distance from sub to wall will never approach 1/4 wavelength when placed along room boundaries).

Ofc none of this takes into account room modes, which tend to have the most significant impact on the response below the Schroeder frequency, and which require a whole additional set of room treatments and considerations to mitigate. For this, best to use corner bass traps and at least two subs (also positioned along room boundaries).

Finally, it's always a good idea where possible to get the first reflection nulls (especially from the front* wall) below the frequency at which the mains cross to the subs. As mentioned, the subs can then be placed along the boundaries, avoiding any first reflection-related nulls. And then ofc to try to fix any remaining problems using DSP if possible...

Regarding the 8Cs, if they do indeed project very little rearward energy, it can be assumed that this will result in zero or negligible boost/cancellation from front wall reflections. So both the broadband boost and narrowband nulls shown in the above graphs will basically disappear down to the frequency at which the 8Cs cease to effectively control directivity (wherever that is - I think around 100Hz IIRC).

(NB: I believe there would still be similar broadband boosts and narrowband nulls resulting from floor and ceiling reflections, since AFAIK the 8Cs are constant directivity horizontally but not vertically. I haven't seen measurements of the 8C's vertical polar response, however, so I'm not sure about this.)

The 8C's ability to dispense with these front-wall related nulls is an excellent thing; the trade-off, however, would be a flatter power response, resulting in less low-mid frequency broadband boost. This is just speculation as I don't have a full picture of how the speakers measure, but this may lead to them being perceived as thin/bright due to the fact that we (and perhaps more importantly, the engineers who mix and master our music) are used to the room/speaker interaction providing a broadband boost to low and (to a lesser extent) mid frequencies, in-room.

*edited to correct mistake
 
Last edited:

hvbias

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I'm on page 18 of this thread and still catching up.

Anyone have measurements of the speakers in their room? How is the bass? How does it handle room modes? Do you use additional DSP to correct the response? Additional subwoofers?
 

Krunok

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I’m not familiar with the rearward polar response of the 8Cs, so I'll mostly restrict this to attempting to answer the non-8C related question. Sorry if any of the following is repeating what you already know ;)

The short oversimplified answer is that with a short distance from the speaker to the front wall you’ll get a broadband 6dB boost from the low bass up to approximately the frequency of wavelength 4 times the distance from the front wall to the acoustic centre of the woofer, and then a series of decreasingly severe higher frequency nulls (eventually resembling more a comb filter effect) up to the point at which the speaker stops projecting significant rearward energy. At 20cm, for example, with typical box speakers this will most significantly result in a nearly 6dB boost from 0 Hz to just under 430Hz, then a very deep null at around 430Hz, then further nulls (of decreasing severity) higher up in frequency, until eventually the response flattens out at the point at which the speaker projects so little sound rearward that interference between the front wave and the reflected back wave becomes negligible.

The longer answer is as follows:

Firstly, the distance from the speaker to the front wall determines the extent to which the direct sound and the reflected sound from the front wall interact at the listening position.

The shorter the distance, the closer in level the reflected wave from the rear wall will be to the direct wave from the woofer at the listening position. So, as the speaker is moved closer to the front wall, the influence of the reflected rear wave on the frequency response at the listening position becomes more severe. At a distance of 20cm (assuming a typical say 2m+ listening distance and a purely reflective front wall) there will be a difference of only one or two dB between the direct and reflected waves, meaning maximum interaction. The first result of this will be a large broadband boost at the listening position to frequencies up to the frequency 4 times the wavelength of the distance from the front wall to the woofer's acoustic centre.

Secondly, the distance from the front wall determines the frequencies at which that the rear reflected wave and the direct wave interact (sum and null).

To illustrate, take your example of a 20cm distance from the front wall (I'll assume this is 20cm from the acoustic centre of the woofer). 20cm is 1/4 wavelength of about 430Hz. So at this frequency (assuming the speaker is omni, which it will more or less be at this frequency if it is a conventional box speaker), the reflected wave will bounce back and combine 180° out-of-phase with the direct wave, creating a deep null. The same will occur at various higher frequencies if the speaker is projecting significant rearward energy at those frequencies too. Meanwhile, in between these nulls the reflected wave from the front wall will be in phase with that of the direct wave, resulting in summing (i.e. narrowband boosts of up to 6dB).

If the reflected wave is almost as high in SPL as the direct wave (which it will be if it's travelled only 20cm before bouncing back, and if the front wall is basically reflective), the cancellations at these frequencies will be almost absolute. Here is a graph which assumes a listening position of 3m, an omni source at all frequencies (obviously false at mid-high frequencies for a monopole box speaker but used here to illustrate), and a purely reflective front wall. You see massive nulls beginning at the frequency with a wavelength of 4 x 20cm, i.e. 430Hz. This first null in particular will tend to destroy the midrange.

View attachment 15182

As we move the speaker away from the front wall, the difference in SPL between the direct and reflected wave increases, meaning that (1) the extent of the interaction becomes less extreme, and (2) the frequency at which the waves begin to interact decreases. Meanwhile, the distances between peaks and nulls at any given frequency above the 1/4 wavelength frequency become closer together, so that the peak/null behaviour begins to resemble a comb filter at a lower frequency.

Here is the same idealised example (omni source, 3m listening position, purely reflective front wall), but now with a distance between the woofer's acoustic centre and the front wall of 1m. As you can see, the overall boost is now not as great, and the nulls now begin lower in frequency, are far less pronounced, and closer together at any given frequency. The frequency of the first null is now that of wavelength 4 x 1m = approx 86Hz.

View attachment 15183

What these idealised graphs don't show (among other things) is that, in reality, a monopole box speaker will tend to become less omnidirectional as frequency increases, i.e. the differences in SPL between the direct wave and the wave reflected off the front wall will tend to become greater as frequency increases. In most cases, a typical modern narrow-baffle closed box speaker will be truly omni only up to about 300-500Hz depending on baffle width and speaker depth, and will project very little rearward energy above around 1 or 2KHz, so there will be little interaction above these frequencies. In other words, the graphs above will begin to look less boosted and less ragged above around 300-500Hz. This transition range in which there is some interaction, although not as much as the graph assumes for an omni source, will tend to continue up to about 1-2KHz, or whatever frequency the speaker stops producing significant rearward energy.

In terms of how to deal with this, as a general rule, for decent midrange reproduction you’d want to keep the distance from the woofer(s) to the front wall at least around a metre, which should reduce the magnitude of the peaks and nulls to under 6dB in most real-world cases, and keep that first widest and deepest null down below the Schroeder frequency (more on this below). In a studio context, I also try to solve this problem two additional ways. Firstly, I use broadband front wall absorption that extends in frequency to below the 1/4 wavelength distance to the woofer (or the point at which the woofer crosses to the subs, whichever is higher). Best is usually dense, thick rockwool with an air gap between it and the front wall (obvs not practical at home). Secondly, I try to ensure that the cancellation distances between the woofer and each of the front wall, ceiling, floor and sidewalls to the listening position are all different; remember that a similar effect occurs not just with the front wall, but with all the room's first reflection points. By ensuring these distances are all different from each other, nulls due to out-of-phase first reflections are spread out in frequency (this is still difficult, but often possible, in a home context).

Use of subs is another way to improve the situation, since these can be placed along room boundaries so that there is no cancellation within their operating frequency range from reflected waves bouncing off first reflection points (the frequencies reproduced by the subs have long wavelengths so the distance from sub to wall will never approach 1/4 wavelength when placed along room boundaries).

Ofc none of this takes into account room modes, which tend to have the most significant impact on the response below the Schroeder frequency, and which require a whole additional set of room treatments and considerations to mitigate. For this, best to use corner bass traps and at least two subs (also positioned along room boundaries).

Finally, it's always a good idea where possible to get the first reflection nulls (especially from the front* wall) below the frequency at which the mains cross to the subs. As mentioned, the subs can then be placed along the boundaries, avoiding any first reflection-related nulls. And then ofc to try to fix any remaining problems using DSP if possible...

Regarding the 8Cs, if they do indeed project very little rearward energy, it can be assumed that this will result in zero or negligible boost/cancellation from front wall reflections. So both the broadband boost and narrowband nulls shown in the above graphs will basically disappear down to the frequency at which the 8Cs cease to effectively control directivity (wherever that is - I think around 100Hz IIRC).

(NB: I believe there would still be similar broadband boosts and narrowband nulls resulting from floor and ceiling reflections, since AFAIK the 8Cs are constant directivity horizontally but not vertically. I haven't seen measurements of the 8C's vertical polar response, however, so I'm not sure about this.)

The 8C's ability to dispense with these front-wall related nulls is an excellent thing; the trade-off, however, would be a flatter power response, resulting in less low-mid frequency broadband boost. This is just speculation as I don't have a full picture of how the speakers measure, but this may lead to them being perceived as thin/bright due to the fact that we (and perhaps more importantly, the engineers who mix and master our music) are used to the room/speaker interaction providing a broadband boost to low and (to a lesser extent) mid frequencies, in-room.

*edited to correct mistake
How effective is MiniDSP SHD with the room response issues? Is it worth the money? :)

https://www.minidsp.com/products/streaming-hd-series/shd

P.S. I have Castle Harlech S2 speakers, room is app 30m2 but speakers are in the corners of the room app 30cm from each wall. They are app 4m from each other and my listeing chair is in the third corner of the triangle with equal sides.

http://www.hifi-review.com/151351-castle-harlech-s2.html
 

oivavoi

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Just to add to the brilliant comment by @andreasmaaan : As I’ve understood it, the DSP boundary adjustment for the back woofers in the 8Cs determines the delay of the drivers on the front vs on the back. The goal is to get a unified wave front reaching the listener, and depending on how far the speakers are positioned from the front wall, this necessitates different delays/adjustments.

In addition, let me add that I haven’t perceived them as “thin” at all. Quite on the contrary, actually. Will take measurements when I set them up anew some weeks from now.
 

andreasmaaan

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Just to add to the brilliant comment by @andreasmaaan : As I’ve understood it, the DSP boundary adjustment for the back woofers in the 8Cs determines the delay of the drivers on the front vs on the back. The goal is to get a unified wave front reaching the listener, and depending on how far the speakers are positioned from the front wall, this necessitates different delays/adjustments.

In addition, let me add that I haven’t perceived them as “thin” at all. Quite on the contrary, actually. Will take measurements when I set them up anew some weeks from now.
That's nice to hear :)
 

Dialectic

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I have measurements taken in my listening room, which is irregularly shaped and, frankly, terrible. I'll share measurements when we move to a house and I get them set up in a proper listening room.
 

Soniclife

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I have measurements taken in my listening room, which is irregularly shaped and, frankly, terrible. I'll share measurements when we move to a house and I get them set up in a proper listening room.
I'd be very interested in the measurements taken in difficult rooms, and how your subjective opinion matches the measurements, i.e. do any measured problems seem audible.
 

Purité Audio

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I have some ‘in-room’ on my site, I measured ATC, Kii and Dutch&Dutch from the same spot speakers in the same positions, the Three/8C measurements are much tidier.
No subwoofer needed unless you wish to use them destructively.
Keith
 

RayDunzl

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I have measurements taken in my listening room, which is irregularly shaped and, frankly, terrible. I'll share measurements when we move to a house and I get them set up in a proper listening room.
Well, please show what you have now to provide a datapoint for a nice before/after discussion on how well they work in sub-optimal (that's all of them isn't it) rooms vs less sub-optimal rooms...
 

Dialectic

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I'd be very interested in the measurements taken in difficult rooms, and how your subjective opinion matches the measurements, i.e. do any measured problems seem audible.
Well, please show what you have now to provide a datapoint for a nice before/after discussion on how well they work in sub-optimal (that's all of them isn't it) rooms vs less sub-optimal rooms...
Too busy working and making money right now. I haven't had a day off since April.

Why don't you guys buy some and test them in your respective rooms? There are a lot of measurements of the 8Cs on the internet already.

I have a feeling one poster wants measurements so that he can say they're worse than speaker X made by Genelec. But I've ignored him, so I don't know for sure.
 

RayDunzl

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