Why Synergy horns?

In another thread I was asked, if I would provide more details about my speakers, so I thought why not?

I have played on active 4 way horn systems since 2016. First iteration was front loaded bass horn, midbass horn, tractrix midrange horn and tractrix tweeter horn. I worked nicely, with all the attributes associated with well implemented horns. Clarity, dynamics, realistic live sound etc.

However some problems will arise, with such horns. First of all, the center to center distance between the different horns is big, compared to the crossover frequencies. We need to be within 1/4 wave in distance at x-over for a seamless transition. For instance if you x-over from the midrange horn to the tweeter horn at 3 KHz the c-to-c distance would have to be 340/3000/4= 2.83 cm (1.11 inch). This is virtually impossible with "normal" horn configurations. This problem rears its ugly head, at every x-over throughout the audio frequency range. As frequency decreases, the wavelengths gets bigger, but so does the horns in the specific bandpass and then c-t-c also increases. It is a linear problem, that can't be solved with the regular approach, aka stacking horns on top of each other. This creates interference problems and lobing in the vertical response curves, that will color the reflection from floor and ceiling. Secondly a large column of vertically stacked horns, will push the sweet spot (SS) further back, for the horns to be perceived as more coherent and integrated, with one another.

But the biggest problem is that almost all horns beam with increasing frequency, it's their way of nature so to speak. What that means, is that the off-axis FR will not be similar to the on-axis FR. This translate into a poor power response, which is not considered a good thing, in terms of best sound quality.

Luckily we can circumvent all these problems with clever engineering and have our cake and eat it too, so to speak. Enter the Synergy horn.

 

DasguteOhr, as Bjorn just explained, we can't use RT60 to determine anything about the sound in the room jokes aside, I think that a specific room reverberation would fall under the subjective department, but I'm well aware of the listening room vs recording room debate. I quite like it a bit dry, also partly why I have narrow directivity speakers, so the recorded room really stands out from record to record. If a piano is recorded realistic, it will sound realistic in here in the garage.

I have also visited a guy that has a RT60 at about 0.1-0.2 sec and even that low, it was not unpleasant to listen to music or converse, on the contrary.

 

Waterfall and reverberation time have nothing to do with each other.

RT60 is the measurement of the decay time of a well mixed reverberant sound field well beyond Dc, a real critical distance.
RT60 is the time in seconds for the reverberant sound field to decay 60 dB after the sound source is silenced.

Since in small rooms, there is no Dc, no well mixed sound field, hence, no reverberation but merely a series of early reflected energy, the measurement of RT60 becomes meaningless in such environments.

What becomes meaningful is the control of early reflections because there is no reverberation to mask them.”

Modal decay rates are not reverberation. Reverberation is “the time in seconds that it takes a diffuse sound field, well beyond a real critical distance, to lower in level by 60 dB when the sound source is silenced.” Modal decay rates are dB-per-second (dB/s) rate of decay for a specific modal frequency.

What is "DC"? Thanks.

 

That would be critical distance

https://gearspace.com/board/studio-building-acoustics/821073-can-small-rooms-have-real-reverb.html

 

What is "DC"? Thanks.

Critical distance.
Critical Distance is the distance from the sound source where the direct and reverberant sound energies become equal. That's not possible in a small room.

If someone treats a small according to reverberation time (RTx), they will end up with a very poor result and the numbers say nothing about the actual quality of the acoustics. It's common that we have to fix rooms that are treated that way.

 

Ethan Winer seems to disagree that we can't have reverberation in a small room, but using absorbers will detriment that notion. He focuses on the 300-3000 Hz area (midrange).

 

Watch the video for a demonstration of the two extremes, very reverberant room vs anechoic. Especially the balloon scene is funny.

The loudest sound in the quietest room | The loudest sound in the quietest room | By The Action Lab | Facebook

The loudest sound in the quietest room

www.facebook.com

 

Ethan Winer seems to disagree that we can't have reverberation in a small room, but using absorbers will detriment that notion. He focuses on the 300-3000 Hz area (midrange).

Should we stick to physics and proof or what an individual thinks? Ethan Winer isn't an acoustician FIY.

You might want to read the thread you linked to. Ethan Winer is being corrected by more knowledgeable people in the field.

 

Ok, so we can't use RT60, but what about the decay waterfall plot, won't they give us a clue about the room sonics, at all?
And can't RT60 be used to compare rooms, even if it might not give us any real valuable information about the room acoustic behavior, i.e. a room with RT60 0.5 sec will be more lively, that a room with RT60 0.2 sec (in REW)? Asking for a friend

 

DasguteOhr, as Bjorn just explained, we can't use RT60 to determine anything about the sound in the room jokes aside, I think that a specific room reverberation would fall under the subjective department, but I'm well aware of the listening room vs recording room debate. I quite like it a bit dry, also partly why I have narrow directivity speakers, so the recorded room really stands out from record to record. If a piano is recorded realistic, it will sound realistic in here in the garage.

I have also visited a guy that has a RT60 at about 0.1-0.2 sec and even that low, it was not unpleasant to listen to music or converse, on the contrary.

I don't doubt in any way that it doesn't sound good. For my loudspeaker (open baffle dipole) a dry tuning is the worst thing you can do. You rob it of all its strengths. If it works for your loudspeaker, congratulations. Here is a room mode analysis(bass) as a waterfall diagram.

 

Went to Royal Arena in Copenhagen, last night to see one of my Bucket List bands Dave Matthews Band. Unfortunately we sat farthest away from the stage and with the concert hall only filled 2/3 a lot of echoes was present from the empty seats. People are actually very good sound absorbers. Kick drum was unbelievable ringing, we are probably talking seconds and with a lot of musicians giving full blast, you really had to concentrate to "listen through" the mess.

Anyway, still had a great time.

 

Ethan Winer seems to disagree that we can't have reverberation in a small room, but using absorbers will detriment that notion. He focuses on the 300-3000 Hz area (midrange).

I want to make the freestanding broadband absorbers from 100 to 150mm Rockwool, but given that I will have to move them daily because my living room is also the listening room, I want to make sure that the Rockwool won't release any particles.

What extra material could I use between the cloth and Rockwool?

If we carefully choose the material it might be possible to kill two birds with one stone. Getting the absorption coefficient of Rockwool more uniform, which by nature is somewhat more effective in the high frequency range. This would possibly also benefit reverberation in my small room.

Apologies for the quick crappy sketch:

 

I want to make the freestanding broadband absorbers from 100 to 150mm Rockwool, but given that I will have to move them daily because my living room is also the listening room, I want to make sure that the Rockwool won't release any particles.

What extra material could I use between the cloth and Rockwool?

If we carefully choose the material it might be possible to kill two birds with one stone. Getting the absorption coefficient of Rockwool more uniform, which by nature is somewhat more effective in the high frequency range. This would possibly also benefit reverberation in my small room.

Apologies for the quick crappy sketch:

Wrapping the rockwool with virtually any cloth will keep the material from shedding particles. I used a coarse burlap for my 2' x 4' x 4" panels to good effect. There are acoustically transparent options out there, but I was looking for the bass absorption capability primarily, to tame a small room's modes better. If you space them from a wall the same distance as their thickness you get an enhanced effect, too. I bought different densities for different locations: 3 lbs/cu. ft. for first reflection points and 8 lbs/cu. ft. for bass duties. Worked well for the room at the time.

 

Nick, you could wrap the Rockwool in some plastic and then finalize it with some cloth of your liking. The thicker the plastic (more layers) the less the absorber will absorb the high frequencies.

 

Ok, so we can't use RT60, but what about the decay waterfall plot, won't they give us a clue about the room sonics, at all?
And can't RT60 be used to compare rooms, even if it might not give us any real valuable information about the room acoustic behavior, i.e. a room with RT60 0.5 sec will be more lively, that a room with RT60 0.2 sec (in REW)? Asking for a friend

A cumulative spectrum or waterfall is simply showing how the frequencies decay over time addional to the frequency response. And yes, that's valid for all rooms of for speaker measurements. But looking at the waterfall for midrange and treble in a room is generally not very helpful.

The importance of measurements really lies in the interpretation and how to apply treatment accordingly. Not many understand that IMO.

 

...I would apply a spray contact adhesive to affix the cloth to the rockwool (or rigid fiberglass). This may work with a plastic "layer" as well, but you would need to test that usecase.

I have made many versions of this solution in multiple thicknesses, shapes and sizes. In my experience, using a spray adhesive and careful wrapping technique, yields professional looking results.

A second set of hands helps a lot, but you can also wind the fabric into a dowel or cardboard tube which will allow a slight tension to be applied while wrapping.

Pre-cut/fit everything "dry" and proceed from there. I recommend starting at a long edge, and completing the top-face. Then go back and fuss with the actual wrap, corners, etc. I have used 3M contact spray adhesive for this, but other products exist at a craft or fabric store. Kind of a fun project, actually.

 

...I would apply a spray contact adhesive to affix the cloth to the rockwool (or rigid fiberglass). This may work with a plastic "layer" as well, but you would need to test that usecase.

I have made many versions of this solution in multiple thicknesses, shapes and sizes. In my experience, using a spray adhesive and careful wrapping technique, yields professional looking results.

A second set of hands helps a lot, but you can also wind the fabric into a dowel or cardboard tube which will allow a slight tension to be applied while wrapping.

Pre-cut/fit everything "dry" and proceed from there. I recommend starting at a long edge, and completing the top-face. Then go back and fuss with the actual wrap, corners, etc. I have used 3M contact spray adhesive for this, but other products exist at a craft or fabric store. Kind of a fun project, actually.

Yeah, fun in an "itchy" sort of way!

 

One of my goods friends have inherited the legendary Snell Type A Reference System, but it has been out of service for the last 15 years or so, because he doesn't have the space to accommodate them. So he decided to sell them. We have common friend who is a private audio dealer, with a very big house and room to represent the gear. So we all had a day of fun of setting up the system and test it before putting it on the market.

It was a bit of a hassle to get it done right, as we did not have a manual and the electronic crossover for the subwoofers were missing (sic). Luckily I had a Behringer DCX 2496 as a stand in filter. Through measurements we got the system up and running and we were all happy to find out, that the speakers and external analog crossovers, were as good as new.



Measurements aprox. 150 cm in front of left and right speaker with no EQ applied, only an electronic subwoofer lowpass filter at 80 hz, 4. order Butterworth . Really nice to see some proper engineering from the hands of the legendary Kevin Voecks. They knew their stuff back in the good times of old The sound was indeed very balanced, with good image and all the audiophile boxes ticked, though I thought there was room for some improvement in the bass. It lacked the last precision, dryness and attack that I'm used to. All in all, this is a top notch speaker system, that runs circles around most out there.

 

Hi,

Concerning the array of mid-range drivers, are they all playing at the same loudness level? I am curious, as this design is always criticized for its potential "comb filtering" effects.

Thanks.

 

Hopkins, no all drivers play with same volume. A normal 3 way bass, midrange, tweeter speaker will have more lobing. Look at the FR in the area 200-500 Hz in the measurement, it is very even and most speakers will have some room induced unevenness in this area. For example the Dali Epikore 11 is using a special approach by giving the two bass drivers a different crossover filter, different slopes and frequency, to prevent floor cancelation.

From Stereophile "Vertically (not shown), the Type A Reference's balance doesn't change to any significant extent as long as the listener's ears are somewhere between the two midrange units, a distance of between 30" and 45" from the floor. Laterally (fig.6), the Type A features the kind of even off-axis treble rolloff that has proved to correlate with excellent soundstaging."

I would say that this speaker is very well engineered.

 

Hopkins, no all drivers play with same volume. A normal 3 way bass, midrange, tweeter speaker will have more lobing. Look at the FR in the area 200-500 Hz in the measurement, it is very even and most speakers will have some room induced unevenness in this area. For example the Dali Epikore 11 is using a special approach by giving the two bass drivers a different crossover filter, different slopes and frequency, to prevent floor cancelation.

From Stereophile "Vertically (not shown), the Type A Reference's balance doesn't change to any significant extent as long as the listener's ears are somewhere between the two midrange units, a distance of between 30" and 45" from the floor. Laterally (fig.6), the Type A features the kind of even off-axis treble rolloff that has proved to correlate with excellent soundstaging."

I would say that this speaker is very well engineered.

Thanks. The very cheap (400€) Teufel speakers I use (mostly for TV and some background listening) have this issue with a dip around 250 Hz, which is more or less pronounced depending on distance you listen to. What is it about the Snell that avoid this? The height of the lower drivers, the fact that there are 2 sets of 2 drivers (top and bottom)?...