biggest risk with horn, dynamics and hearing loss

Hearing loss and maximum allowed listening time before hearing damage

Recommended workplace maximum sound exposure (dBA) before risk of long-term hearing loss.

Few listeners are in the 85 dB category (A scale used). Exposure to six hours of daily listening at 85dB will cause no measurable hearing loss… per safety guideline recommendations.

Most listeners fall into 90 dB SPL category. Exposure to three hours of daily listening is the recommended daily maximum.

I tend to listen louder than the average person, often being in the high 90's dB. This suggests one hour is around the maximum daily limit. However, I'm often guilty of extended sessions in excess of 2 hours.

We all know that once we crank that volume up, going back down again proves rather difficult.

The problem is that all safety guidelines are "A" weighted. Intended for work.

Music is "Z" weighted as it's full-range and your speaker hopefully are full range too.

Conversely, because human hearing is most sensitive at around 4 kHz, low frequency drivers tend not to damage ear drums as much as tweeter or mid-range drivers. Moreover, the first sign of potential hearing loss usually happens at around 4 kHz. (the famous "4 kHz" notch musician develop). Tinnitus (ringing in the ears) also tends to be around this frequency, but sometimes can occur closer to 5 kHz.

My medical benefits cover yearly audiologist visits. While there, I like to chat about various causes of noise induced hearing loss as well as traditional aging factors.

As a member of the military, I’m often exposed to various repetitive loud sounds such as artillery, rifles, generators, armored vehicles, fighter jet engines, heavyweight helicopters and not so quiet marine fleet propulsion units. The average civilian may never hear more than one or two of these sounds, and even then… it’ll likely to be for only a few seconds.

The audiologist told me that hearing aids prescribed to military personnel are roughly 2x as powerful as the general population. Quite often, military people need to wear them much earlier in their life as well. A friend of mine is required to wear hearing aids every day now, and he's only 35. He was a tank driver for few years. Enough said.

The dangerous HORN reality:

Usually, when a system starts to distort (speaker rating limit or amplifier clipping) it sounds so bad that most audiophiles, as a reflex instinct, immediately lower the volume, as it becomes unbearable. On a positive note, this reflex is great as it saves your ears and equipment.

When a system is designed to push around 125 dB across the full 20-20 kHz band, you can crank it up and it always stays "clean" sounding. As a result, the lowering of volume reflex isn’t triggered. This is the horn’s best advantage. However, it can be dangerous!

As horns are extremely efficient, in a home environment, they can play insanely loud at <1 W.

My tweeter and mid-range horns are 107 dB efficient. (3.5 W amplifier on each of them)
The bass bin exhibits 104 dB efficiency. There are 300 Watts of pure Krell power in full class A pushing them, so going loud isn't a problem, and they never come close to reaching their maximum linear +-12mm excursion.
There are 6 sub-woofers also, with each driver relying on a dedicated 400 Watts channel. Each driver has 22mm linear excursion and can go louder than my ears can endure.

Below is a quick measurement I made with the microphone at the listening position, as I raised the volume to see how loud it can get. Daft Punk’s ” Around the World “ features a clean punchy bass line which can accurately test any system’s sheer dynamic capacity.

As you can see below (right), in "A" weighing, it shows a peak of a manageable 96 dB. As per chart above, one would think that you could safely listen for ~30 minutes.

However, one would be wrong! The bass notes of the track are centered around 60-80 Hz and the "A" weighting shows them at ~25 dB lower than they really are.

Reality is that in "Z" weighing scale, one can really see the tremendous impact the song provides. (chest pounding in fact)

I recorded a peak of 123.7 dB. Which is 27 dB louder than the "A" weighting at 96.0 dB suggests.

Per the guidelines, one could listen for less than 30 seconds at 123 dB, before it can potentially cause irreversible hearing loss. (far cry from the initial 30 minutes permissible exposure)

I lasted less than a minute before I had to drop the volume. It was approaching my pain threshold, and I didn't feel like having "buzzing ears" for hours afterward.

Playing Daft Punk at 123+ dB at the listening position, could never occur with some bookshelf or even some so called serious floor-standing speakers.

Even loudspeakers costing more than your average car, don’t often reach much more than 108 dB. (and they sure don’t mention the distortion you'll have at this elevated level. More noise than sound if you ask me...)

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This contrasts with the professional world though, as they tend to provide more information than the retail HIFI brochures. Additionally, they’re often truthful about their product’s real output capacity, and readily admit the limitations.

The 4350 was JBL’s flagship speaker back in the day, when loudspeakers where serious and size reduction wasn't a priority. Accurate sound reproduction was the primary focus, which is a far cry from their current 2 ways "M2" flagship speaker, which incorporates XYZ advanced marketing. Sorry… I meant technology advancement.

The old 4350 still fetches a surprising amount of money, and there are many good reasons why. They often sell for the same price as the brand new, fully warrantied, current Flagship M2’s... think about that.

I can just about imagine the 4350's running fully active with DSP on all 4 channels and have some subwoofer scattered in the room :) Now that’d be quite the treat.

I’m sure the M2 is a great speaker. However, if I had to choose between the two, I’d go vintage for sure, but I’d also transform them to an active speaker.

Below is a partial scan of the "classic" JBL 4350 monitor speaker specification page. The red text are my comments.

At one time, JBL’s were very serious, showing 126 dB output capacity at 3 meters… WOW, this equates to 136 dB at 1 meter!!!

The Famous JBL 4350

Dual 15" woofer (30hz - 300 Hz) Bass Reflex loaded.

12" midrange (300hz - 1.1 kHz)

2" exit horns (1.1kHz - 8 kHz)

Tweeters (8 kHz and up, slot type tweeter)

Why people today try to push 1" exit compression drivers to ~800 Hz is totally incomprehensible to me. They must love distortion :)

New JBL Flagship

The M2, active system with integrated DSP. This is good progress as DSP is mandatory with today’s technology.

Only two way speakers with a single 15"...

800 Hz crossover point. What’s going on here?

Is this really progress or plain cost cutting? How high can that double diaphragm compression driver possibly go?

No super tweeter, shameful.

How much distortion the small double diaphragm compression driver generate at as low as 800 Hz?

Class D amplification? YUK, Do I need say more?

Below: M2 Specifications

My comments in red text.

M2 Specification

Red = my comments...

Having the ability to reproduce sound loud and clean is beautiful.
Using such ability too often and for extended period is very dangerous.
One can't heal hearing loss.