JBL HDI-1600 Speaker Review

[Absolute]

The only way to avoid a "dry" or "overdamped" room is to use broadband absorption. It needs to absorb linearly from below 200 hz and up. Most people use too thin absorption and end up with the weird effect that comes from basically EQ'ing the higher frequencies of the reflections.

I'm willing to bet quite alot of outdated milk that those who argue that early reflections are better than damping the reflections have never tried that experiment with 25-30+ cm porous absorbers.

The correct amount of damping is always broadband. Anything else will result in audible weirdness.

 

[tuga]

The only way to avoid a "dry" or "overdamped" room is to use broadband absorption. It needs to absorb linearly from below 200 hz and up. Most people use too thin absorption and end up with the weird effect that comes from basically EQ'ing the higher frequencies of the reflections.

I'm willing to bet quite alot of outdated milk that those who argue that early reflections are better than damping the reflections have never tried that experiment with 25-30+ cm porous absorbers.

The correct amount of damping is always broadband. Anything else will result in audible weirdness.

Isn't too much absorption the cause of a "dry" or "overdamped" room?

Doesn't the use of broadband absorption make sense when you wish to absorb the spectrum evenly?

 

[QMuse]

Isn't too much absorption the cause of a "dry" or "overdamped" room?

Surely it will. According to graphicons Amir posted above reverb less than 0.5 sec is considred low. So the question is how much is too low?

IME it is below 0.3sec when it starts to sound "dry" and "overdamped".

 

[tecnogadget]

Isn't too much absorption the cause of a "dry" or "overdamped" room?

Doesn't the use of broadband absorption make sense when you wish to absorb the spectrum evenly?

He is pointing out (better than I did) the difference between narrow and broadband porous absorbers.

Its not just the amount of let say “panels” you put arround your room, its also the amount of frequencies you are addressing with such panels.

Thin porous absorbers will only be effective for high frequencies. Thicker panels will be efective for both midrange and high frequencies.

When using thin panels, since you are only effectively absorbing high frequencies, the room will be perceived as dry.
Use broadband absorption panels, since the effective absorption is more evenly across frequencies you wont feel the room as dry (as long as you don't exceed with the amount of panels, everything has a limit, and you can always measure the decay times to verify results)

 

[Absolute]

Isn't too much absorption the cause of a "dry" or "overdamped" room?

Doesn't the use of broadband absorption make sense when you wish to absorb the spectrum evenly?

Depends on how we define those words, but essentially that's, of course, true. I put those words in quotation marks because in my experience people tend to use those words when the correct term would have been "unevenly damped".

The sound will feel closed-in or almost like pressurized if you damp too much of the higher frequencies and little to none of the lower. It almost sounds like you have water in your ears. When you absorb evenly (down to 100 hz) it doesn't feel that way, it only sounds clearer, snappier and much more dynamic due to the sensation of quickness to silence between sounds.
The difference between, say 4 inches of dampening and 10 inches is startling. But even if done correctly it's not necessarily for everyone.
Some like the event to sound like "in your living room" while others like to hear "how it was like over there".

No one really likes the sound when you damp reflections unevenly.

 

[LTig]

Some speaker companies have a family sound, the larger ones sounding like 'bigger and louder' versions of the smaller ones in my experience.

This is certainly true for the "better" studio monitor producers. Actually IMV the sonic differences between comparable products of said producers are smaller than one would think.

 

[localhost127]

Is the available research focusing on live speech or stereo-reproduced speech?

what's lost on many that cite such "speech intelligibility" studies (in an effort to imply speech intelligibility is improved with the presence of high-gain, early indirect specular reflections) is the context of such tests and their application. they are primarily with respect to UNAMPLIFIED environments such as classrooms, theaters, conference rooms, etc - where "speetch intelligibility" is "improved" by nature of the direct signal being "heard" where early reflections within the integration time increase the perceived loudness (gain) of the direct signal speech against the background noise floor.

user above cited: https://asa.scitation.org/doi/abs/10.1121/1.1570439

it very-clearly outlines in the Abstract section that the context of the study is related to gain/snr issues - not articulation in amplified environments.

The speech intelligibility test results confirm the importance of early reflections for achieving good conditions for speech in rooms. The addition of early reflections increased the effective signal-to-noise ratio and related speech intelligibility scores for both impaired and nonimpaired listeners. The new results also show that for common conditions where the direct sound is reduced, it is only possible to understand speech because of the presence of early reflections.

in home reproduction environments, we have AMPLIFIED sound sources where if the gain of the direct signal cannot be "heard", one simply turns the volume knob appropriately. and if one has a condition where the amplified direct signal somehow CANNOT be heard without the increase in perceived gain due to early reflections, then one clearly has sound isolation issues and/or lives next to a construction site/train yard.

the 2nd article the user cited above :https://www.google.com/url?sa=t&sou...Vaw0y-0tOmE_7ioJVIpsh5_pb&cshid=1586599059036

Speech intelligibility enhancement by early reflections:
Early reflections in a room can improve speech intelligibility for normalhearing
listeners, because the auditory system integrates them with the direct
sound which results in an increased speech level

again, not an issue in home reproduction setups that have amplification capability where the gain of the direct signal can easily be set such that the direct signal can easily be "heard".

these studies are far too commonly presented on audio forums but the context of the environments is usually lost or missed.

the easiest test to do at home is simply listen to a high-quality speech recording through headphones (of which there are no "early reflections"), and attempt to imply there is any sort of issue with speech articulation or intelligibility.

 

[Frank Dernie]

what's lost on many that cite such "speech intelligibility" studies (in an effort to imply speech intelligibility is improved with the presence of high-gain, early indirect specular reflections) is the context of such tests and their application. they are primarily with respect to UNAMPLIFIED environments such as classrooms, theaters, conference rooms, etc - where "speetch intelligibility" is "improved" by nature of the direct signal being "heard" where early reflections within the integration time increase the perceived loudness (gain) of the direct signal speech against the background noise floor.

user above cited: https://asa.scitation.org/doi/abs/10.1121/1.1570439

it very-clearly outlines in the Abstract section that the context of the study is related to gain/snr issues - not articulation in amplified environments.

The speech intelligibility test results confirm the importance of early reflections for achieving good conditions for speech in rooms. The addition of early reflections increased the effective signal-to-noise ratio and related speech intelligibility scores for both impaired and nonimpaired listeners. The new results also show that for common conditions where the direct sound is reduced, it is only possible to understand speech because of the presence of early reflections.

in home reproduction environments, we have AMPLIFIED sound sources where if the gain of the direct signal cannot be "heard", one simply turns the volume knob appropriately. and if one has a condition where the amplified direct signal somehow CANNOT be heard without the increase in perceived gain due to early reflections, then one clearly has sound isolation issues and/or lives next to a construction site/train yard.

the 2nd article the user cited above :https://www.google.com/url?sa=t&sou...Vaw0y-0tOmE_7ioJVIpsh5_pb&cshid=1586599059036

Speech intelligibility enhancement by early reflections:
Early reflections in a room can improve speech intelligibility for normalhearing
listeners, because the auditory system integrates them with the direct
sound which results in an increased speech level

again, not an issue in home reproduction setups that have amplification capability where the gain of the direct signal can easily be set such that the direct signal can easily be "heard".

these studies are far too commonly presented on audio forums but the context of the environments is usually lost or missed.

the easiest test to do at home is simply listen to a high-quality speech recording through headphones (of which there are no "early reflections"), and attempt to imply there is any sort of issue with speech articulation or intelligibility.

Makes total sense. The reflections simply make it louder to make it more intelligible rather than the reflections themselves being actually beneficial, but rather not detrimental.

 

[tuga]

what's lost on many that cite such "speech intelligibility" studies (in an effort to imply speech intelligibility is improved with the presence of high-gain, early indirect specular reflections) is the context of such tests and their application. they are primarily with respect to UNAMPLIFIED environments such as classrooms, theaters, conference rooms, etc - where "speetch intelligibility" is "improved" by nature of the direct signal being "heard" where early reflections within the integration time increase the perceived loudness (gain) of the direct signal speech against the background noise floor.

Thanks for confirming my suspicions.

In large concert halls reflector panels located in walls and ceiling are used to project a more even soundfield across the audience.
In a control room reflector panels located in walls and ceiling are used to deflect sound away from the listening spot creating a reflection-free zone.

 

[tuga]

Further on the subject of wide- vs. narrow-dispersion and the effects of side-wall reflections.

I was having a look at Geoff Martin's blog. In an entry titled "B&O Tech: What is “Beam Width Control”?" he writes the following:

When a recording engineer makes a recording in a well-designed studio, he or she is sitting not only in a carefully-designed acoustical space, but a very special area within that space. In many recording studios, there is an area behind the mixing console where there are no (or at least almost no) reflections from the sidewalls . This is accomplished either by putting acoustically absorptive materials on the walls to soak up the sound so it cannot reflect (as shown in Figure 1), or to angle the walls so that the reflections are directed away from the listening position (as shown in Figure 2).

Both of these are significantly different from what happens in a typical domestic listening room (in other words, your living room) where the walls on either side of the listening position are usually acoustically reflective, as is shown in Figure 3.

In order to get the same acoustical behaviour at the listening position in your living room that the recording engineer had in the studio, we will have to reduce the amount of energy that is reflected off the side walls. If we do not want to change the room, one way to do this is to change the behaviour of the loudspeaker by focusing the beam of sound so that it stays directed at the listening position, but it sends less sound to the sides, towards the walls, as is shown in Figure 4.

So, if you could reduce the width of the beam of sound directed out the front of the loudspeaker to be narrower to reduce the level of sidewall reflections, you would get a more accurate representation of the sound the recording engineer heard when the recording was made. This is because, although you still have sidewalls that are reflective, there is less energy going towards them that will reflect to the listening position.

https://www.tonmeister.ca/wordpress/2015/06/30/bo-tech-what-is-beam-width-control/

 

[localhost127]

Going back to 1970s style of mixing/master studios where all reflections were considered to be "bad," people have built some kind of online consensus that you need to go and "find all first reflections and absorb them." This is counter to research that indicates that side reflections can be beneficial. And that if you put too much absorption in a room, it can be come quite "dead" and dull sounding. With well designed speakers, reflections have similar tonality to direct sound and help reinforce that sound. This improves such things as speech intelligibility.

i'm unsure which mix/master studios in the 1970s you are referring to specifically, but the primary 2ch stereo control room models do not "consider all reflections to be bad". that's simply a fundamental misunderstanding of the subject matter.

your statement can be made for Hidley/Newell Non-Environment (NE) rooms, as they are constructed as not to induce any significant indirect specular reflections to the listening position. the speaker/listener perspective is effectively anechoic, but the listener/room perspective is not (reflective floor and front wall so operating in the bounded space does not feel uncomfortable).

but for Davis LEDE rooms (and subsequently D'antonio RFZ), the insinuation that "all reflections are considered to be bad" is factually incorrect. in the LEDE psycho-acoustic response, only the Inter-Signal Delay (ISD) gap is defined (length in time, ms) where-by the direct signal is all that is heard and all indirect energy incident from the room is attenuated and thus effectively anechoic. indirect energy is then re introduced to the listening position, terminating the ISD via a lateral-arriving, exponentially decaying, dense/reflection-rich diffuse sound-field. the later-arriving sound-field is achieved via the use of 1-dimensional Reflection Phase Grating diffusers with the wells oriented vertically such that the spatial dispersion (diffraction lobes) are generated in the horizontal plane (and thus impede the listening position from the rear/rear-side walls for lateral envelopment).

Peter D'Antonio (of RPG) created the Reflection Free Zone model, which is in effect a geometric way to achieve the LEDE response. it utilizes splayed walls angled to redirect the first-order reflections away from the listening position and towards the rear wall. this in essence removes required broadband absorption from within the room (as the splayed walls can remain reflective), and the flight path difference from the redirected first-order reflections help to "redrive" the rear wall diffusers to contribute to the dense, reflection-rich indirect sound-field. the termination and later-arriving sound-field are fundamental requirements to achieve LEDE response.

so to imply that control/mix rooms somehow seek to consider "all reflections bad" is factually incorrect and erroneous assertion. in LEDE/RFZ, for example, all reflections aren't "removed" or "absorbed" - they are *controlled* and subsequently re-introduced to the listening position in a managed fashion (ie, controlling their time-arrival, gain, type (sparse vs diffuse), and direction). it's a managed indirect sound-field. "reflections" measured that fall within the ISD-gap are traced back to their incident boundary and attenuated, but only those discrete signals deemed destructive. the diffusers are an integral component to present a very DENSE, REFLECTION-RICH lateral/horizontal later-arriving sound-field to the listening position for envelopment.

is your experience with any of these rooms that their lack of early reflections somehow constitutes poor speech intelligibility? or that re-introducing high-gain early reflections would somehow aid or improve speech intelligibility of these rooms?

 

[localhost127]

I didn't think absorbing 1st reflections was the issue?

you don't even need to "absorb" - you can simply "redirect" with the use of splayed walls or large (wrt wavelength) flat panels angled away from the listening position. attenuating the small room's natural first-order reflections will increase accuracy of localization and imaging, and will increase the psycho-acoustically perceived size of the space by delaying when indirect energy impedes the listening position.

applying reflective panels or splaying the walls is one way to attenuate the first-order reflections while maintaining said energy (which can be repurposed) and limiting the amount of absorption within the room.

 

[localhost127]

You are right. I mean, turning your listening position into a Reflection Free Zone should not be detrimental at all, as long as you know what you are doing and not placing indiscriminate absorption.

Choosing the correct type of absorption solution to address the correct frequency range while measuring the results should be valid and IMHO better than not doing it. Doing it in such way won’t yield to a dry room.

D'Antonio's RFZ utilizes splayed walls to physically redirect the first-order reflections away from the listening position (and towards the rear-wall reflection phase grating diffusers). specular region absorption for first-order reflections isn't even required - but otherwise broadband absorption (to fully attenuate the indirect specular reflection - vs simply EQ'ing it or functioning as a low-pass filter) should be utilized.

 

[localhost127]

Thanks for confirming my suspicions.

In large concert halls reflector panels located in walls and ceiling are used to project a more even soundfield across the audience.
In a control room reflector panels located in walls and ceiling are used to deflect sound away from the listening spot creating a reflection-free zone.

correct - and difference too that small acoustical spaces do not exhibit a reverberant sound-field that is present to mask the early reflections like in concert halls and auditoriums. there is no exponentially rising, exponentially decaying random-incidence reverberant sound-field that becomes the room's effective noise floor.

 

[Bear123]

Did I see somewhere that an HDI tower is planning to be tested as well? Or the center? Really curious to see how JBL managed the wide, four driver center channel in terms of off axis response and lobing. Revel did a great job with their 2 way MTM such as the C25. I assume the JBL 4500 center will be a 2.5 way with the four woofers playing different frequencies to reduce lobing, will be interesting to see how effective it is. One would assume such a design is capable of performing well considering Revels newest, most expensive center channel in the Be lineup uses four woofers.

 

[amirm]

I didn't think absorbing 1st reflections was the issue?

It was but regardless, that was the background story. The real story today is that based on those types of designs and lay intuition that "reflections must be like echos," it has become the norm in many forums to tell people to a) run ETC and b) find anything that spikes in there and put an absorber on it. It starts with left and right walls. Then the floor. Then the ceiling. Then the wall behind you. Then the front wall. Then the lamp next to you. Then the shoes you are wearing, on and on.

Placebo effect and chasing graphs causes them to build completely dead and ugly rooms by the time they are done. Then watch some of them come back a year later and say, "I ripped out everything and the sound was so much better!"

Ask any professional acoustician their number one pet peeve and it is an audiophile who has strapped these panels everywhere as above.

 

[amirm]

Did I see somewhere that an HDI tower is planning to be tested as well?

Originally yes but the owner decided to get the 1600 for testing before jumping both feet. He is planning on getting the towers now so if that happens, I will be testing them.

 

[amirm]

Peter D'Antonio (of RPG) created the Reflection Free Zone model, which is in effect a geometric way to achieve the LEDE response.

Yet he doesn't advocate anything you say today. Localhost, you and I have discussed all of this across months on AVS Forum. This is a review thread. Please don't pollute it with your comments which I have answered repeatedly then to you. You can post them here if you like: https://www.audiosciencereview.com/...ds/perceptual-effects-of-room-reflections.13/

Dr. D'Antonio actually contacted me post publication of that article, saying how much he liked it, and sharing the same complaint I have about stuff you post. So don't think he is your friend in this argument. He is not. See this presentation he made which I shared with you before: https://www.audiosciencereview.com/...y-theory-without-measurement.7127/post-172075

 

[Thomas savage]

Off topic posts moved to here

https://www.audiosciencereview.com/...ds/perceptual-effects-of-room-reflections.13/

 

[Sal1950]

@amirm , I was very excited to see the 1600 do so well in it's measurement. My only personal disappointment was in the sensitivity rating that I had to go to JBL for. JBL rates the speaker at,
"Sensitivity (2.83V @ 1M): 85dB"
which surprised me since the all the larger and center HDI models are rated at either 90 or 92 db? Don't know why they lost so much in the 1600? I any case can you figure from your measurements what the sensitivity looks like to you?
I really wish you would post sensitivity ratings in the same manner in which all the manufacturers and other testers do for comparison.
I know most of them like to exaggerate the posted numbers since many buyers find them important.
I would hate to purchase these only to find out I'd need 3 new amps to drive them.
TIA