Dutch & Dutch 8Cs

[oivavoi]

Give it a try and see if it works. I doubt it will.

I’ve never seen any compelling measurements which demonstrate modal reduction below 100hz for any cardiod speaker. I can see it’s merit in reducing lateral boundary interference (100-300hz common sidewall interference range). But Kiiaudio and D&D have terrible floor bounce; one step forward, one step back. I bet the kiiaudio BXT module will eliminate the floor bounce. Maybe it can lower the bottom frequency for the cardiod response too.

I’m still waiting on some high resolution LF measurements which compare a normal full range speaker to cardiod speaker. There are tons of measurements, tests and mathematical simulations which demonstrate subwoofer efficacy. Subwoofers are way more effective (performance and cost).

There might be some misunderstanding here: the D&D's are NOT cardioid below 100 hz. The cardioid response stops at 100 hz. They have two "normal" omni subwoofers on the back, which fire backwards into the front wall. With boundary adjustment eq settings to optimize it. The idea is to avoid the Allison dip. Hence, the bass wave from below 100 hz will originate from the front wall, kind of.

 

[dallasjustice]

Hence, the bass wave from below 100 hz will originate from the front wall, kind of.

No. It won’t.

 

[oivavoi]

No. It won’t.

Why? You might very well be right, I just struggle to understand what we're disagreeing about here...

 

[Purité Audio]

I can’t either , the rear drivers of the 8Cs would actually be nearer to the wall than a conventional sub, we shall see.
Keith

 

[dallasjustice]

Why? You might very well be right, I just struggle to understand what we're disagreeing about here...

You’ve already answered your own question.

the D&D's are NOT cardioid below 100 hz

 

[oivavoi]

You’ve already answered your own question.

But when the bass waves leave the back subs on the D&Ds, which are located 10 cm from the wall, they will spread out and be reflected back into the room. As far as I can understand it at least. So they will function in exactly the same manner as a subwoofer that is placed against the front wall, with the driver facing against the wall and not the room. How can this NOT create a plane wave from the front wall? Doesn't the front wall function as a big reflector?

There is obviously something you have in mind I fail to see here, but I still don't understand what it is...

 

[pirad]

The best way to try control the bass is to separate it from the mains and distribute it with several (3-4) subs. It’s been researched, described and implemented by Harman, Geddes ( PhD on the topic), LeJeune.
The optimal positions of the subs almost never agree with the desired positions of the mains. Backward firing subs in the same box as the mains
is a courageos proposition.

 

[dallasjustice]

But when the bass waves leave the back subs on the D&Ds, which are located 10 cm from the wall, they will spread out and be reflected back into the room. As far as I can understand it at least. So they will function in exactly the same manner as a subwoofer that is placed against the front wall, with the driver facing against the wall and not the room. How can this NOT create a plane wave from the front wall? Doesn't the front wall function as a big reflector?

There is obviously something you have in mind I fail to see here, but I still don't understand what it is...

If you had to have your speakers up against the frontwall, it’s possible. But it wouldn’t work as well as a single sub on the frontwall. I’ve tried source sink with 4 subs which is the same thing as that. There’s a paper from Celestinos which describe a 4 sub source sink array like that. But the best one is the Fazenda test which shows the 2 mono sub frontwall and backwall performs best. It’s not a bulletproof experiment. But it fits with my own experience.

The fun thing is that you can try different sets ups. Measure them all and pick the one which measures best. It’s that simple.

 

[oivavoi]

The best way to try control the bass is to separate it from the mains and distribute it with several (3-4) subs. It’s been researched, described and implemented by Harman, Geddes ( PhD on the topic), LeJeune.
The optimal positions of the subs almost never agree with the desired positions of the mains. Backward firing subs in the same box as the mains
is a courageos proposition.

I actually think the creator of the D&D concept would agree with you on that, that a distributed multisub setup that is separated from the mains is the ideal. The point of the backward firing subs of the 8cs is to simplify such a setup, since few people have the space and/or know-how to implement four subs. It's a second-best option. Festivus for the rest of us.

 

[oivavoi]

If you had to have your speakers up against the frontwall, it’s possible. But it wouldn’t work as well as a single sub on the frontwall. I’ve tried source sink with 4 subs which is the same thing as that. There’s a paper from Celestinos which describe a 4 sub source sink array like that. But the best one is the Fazenda test which shows the 2 mono sub frontwall and backwall performs best. It’s not a bulletproof experiment. But it fits with my own experience.

The fun thing is that you can try different sets ups. Measure them all and pick the one which measures best. It’s that simple.

Sound advice! Will do it as soon as I get them properly installed (currently just have them setup in a temporary location).

 

[fredoamigo]

multiple sub integration methods are numerous, the velti one is not really the same as the fazenda one which is not really the Griesinger one and maybe I forget some? difficult to find !!

 

[dallasjustice]

multiple sub integration methods are numerous, the velti one is not really the same as the fazenda one which is not really the Griesinger one and maybe I forget some? difficult to find !!

That’s right and many more. I think it’s fun to experiment with different setups. It can be much like putting a puzzle together. The other nice thing about playing with subs is that the measurements (decay and frequency response) always reflect listening preference as long as one uses linear phase crossovers and they are reasonably time aligned to listening position.

 

[pirad]

multiple sub integration methods are numerous, the velti one is not really the same as the fazenda one which is not really the Griesinger one and maybe I forget some? difficult to find !!

They all agree on one thing- the subs positions are different than the mains.

 

[dallasjustice]

They all agree on one thing- the subs positions are different than the mains.

Not always. See my 3rd post on this thread I started.
https://audiosciencereview.com/foru...m2-audiolense-digital-crossovers-w-subs.2369/

It is true that the front subs aren’t right next to the R/L. But they are very close on the each adjacent sidewalk.

 

[oivavoi]

They all agree on one thing- the subs positions are different than the mains.

This is too simplified, IMO. There is no iron law that says that a subwoofer must be positioned in a different place than the mains. It's an empirical matter! The point is rather that subwoofers and mains often will benefit from different placements. One reason is that mains quite often will benefit from standing out in the room, which is usually a bad placement for subwoofers. But this depends on many factors, among them what the best placement would be for a particular pair of speakers in a particular room, and that bass response in actual rooms usually differs from what the rules of thumb would predict.

If you look at Welti's work for example (probably the most famous and influential work on the subject), he lists three different configurations as "best" (see page 21 in this presentation). Configuration nr 12 is actually very close to how it would be logical to place the Dutch & Dutch speakers in a rectangular room like this. Because of their cardioid dispersion, they don't suffer from standing close to the front wall.

So with two additional subs placed directly across the room from the D&Ds in such a setup, you achieve one of Welti's "best" configurations.

What remains, of course, is that having the subs inside the main speaker cabinet creates additional vibrations, which would be reduced if the mains were to be relieved of sub duty. There's no getting away from that trade-off when integrating the subs into the speaker.

 

[Sal1950]

That’s right and many more. I think it’s fun to experiment with different setups. It can be much like putting a puzzle together. The other nice thing about playing with subs is that the measurements (decay and frequency response) always reflect listening preference as long as one uses linear phase crossovers and they are reasonably time aligned to listening position.

Some would call it fun, others a mind boggling chore.
This is all getting way too complicated to get a simple stereo pair + subs implemented.

 

[Dialectic]

Some would call it fun, others a mind boggling chore.
This is all getting way too complicated to get a simple stereo pair + subs implemented.

First we had the GPL issue spotters on this thread, and now we have an increasingly bewildering subwoofer debate. Makes me want to pick up a copy of TAS.

Just kidding, of course.

 

[pirad]

This is too simplified, IMO. There is no iron law that says that a subwoofer must be positioned in a different place than the mains. It's an empirical matter! The point is rather that subwoofers and mains often will benefit from different placements. One reason is that mains quite often will benefit from standing out in the room, which is usually a bad placement for subwoofers. But this depends on many factors, among them what the best placement would be for a particular pair of speakers in a particular room, and that bass response in actual rooms usually differs from what the rules of thumb would predict.

If you look at Welti's work for example (probably the most famous and influential work on the subject), he lists three different configurations as "best" (see page 21 in this presentation). Configuration nr 12 is actually very close to how it would be logical to place the Dutch & Dutch speakers in a rectangular room like this. Because of their cardioid dispersion, they don't suffer from standing close to the front wall.

So with two additional subs placed directly across the room from the D&Ds in such a setup, you achieve one of Welti's "best" configurations.

What remains, of course, is that having the subs inside the main speaker cabinet creates additional vibrations, which would be reduced if the mains were to be relieved of sub duty. There's no getting away from that trade-off when integrating the subs into the speaker.

You are pointing to interim results of one of the scenarios by Welti (investigation no 4), in fact on page 59, not 21. In his end conclusions (page 76) placement # 12 is not there. It is replaced by placement # 6 and with a justification.
But even if there was a recommendation to put subs with mains, that would not be advisable for two other reasons: vibration
and better performance from close to floor placement. Putting subs in mains, high above the floor and firing backwards is not optimal. But of course one needs to hear and test before passing final opinions. I am all open to tests comparing various solutions. From my side I can offer a set of 4 subs with an amplifier. There is of course the small issue of travel/transportation
for one of the sides.
BTW I am personally more influenced by Geddes who did PhD on the topic. See here:
http://www.gedlee.com/Papers/multiple subs.pdf
http://www.gedlee.com/Papers/Setting up subwoofers.pdf
WELTI CONCLUSIONS

One subwoofer at each wall midpoint is the best in terms of Std, Max-ave and Max-min but does not support low frequencies particularly well. Two subwoofers, at opposing wall midpoints, performs very nearly as well as four at the midpoints and gives a much better LF factor. One subwoofer in each corner also has good low frequency support, but does not perform quite as well as one subwoofer at each wall midpoint, in terms of Std, Max-ave and Max-min. If cost and aesthetics are considered, subwoofers at 2 wall midpoints is preferred.

 

[pirad]

BTW, subs don't need to be imposing and ugly. See distributed bass at my friend's house.
The set up is simple: scatter around and ask the wife to put some decorations on them.
EQ at home in my experience delivers gains not worth the additional cost and hassle.

 

[dallasjustice]

I generally agree with Welti 2 and 4 subwoofer midwall. But I have to say that very few rooms are a perfect rectangle and there are other arrays which do other things better than Welti midwall arrays.

The misunderstanding many have for the Welti recommendations is that people believe that the subs cancel room modes. That isn’t exactly the case when you actually measure the decay times. When I did the measurements, I discovered that the modes weren’t eliminated. Rather, the modes were spread wider. Also the frequency response is flattened out. The Welti arrays are very effective and good. But they do not eliminate room modes like a source/sink array can eliminate length modes. Most of the the time, it doesn’t matter that much because the user is also using EQ and that can help reduce decay times as well.

The other criticism I have for the Welti arrays is that it only focuses on <100hz bass. IMO, bass quality 100-200hz is even more important to music than <100hz. Many folks experience boundary interference “Allison Effect” in the 100-300hz range. Some of these boundary interference problems can also be eliminated with smart subwoofer placement.

IMO, the goal should be excellent bass quality from 20-300hz.