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Compact Horn subwooferene

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Det er utviklet nye T-serie modeller. T8016 har egen tråd, har fått produktside, med bilder og litt informasjon.

T8016:

Så er det en ny stor, høy, flat T140:

Denne får ytelse som de største modellene, slik som V110. Sammenlignet med V110 for T140 enda litt dypere bass, med enda litt mer kapasitet helt i bunnen.

T140 har også fått produktside nå.

Så er det begynt design av en mindre, høy, flat T101, se her sammnelignet med T140 - slankere, mer elegant, tar mindre plass:

T101 får ytelse nær opp til T8016.

En stor design med lite frontareal og laaang dybde er skissert:

Denne får ytelse som de store T140.

Poenget med veldig laaang dybde er at dette er ideelt for plassutnyttelse i noen rom og systemer. Den kan også plasseres som benker langs frontveggen. Denne kan ikke stå oppreist.

V80 installert i et demorom. Her med JBL høyttalere. Gromt oppsett. / V80 installed in a demo room. Here with JBL main speakers. This is nice.

Slik ser det ut inni en T140:


Bilde fjernet inntil videre.

Når jeg bygger, bruker jeg tegninger på papir. Det er trangt om plassen, så da ser det slik ut når jeg bygger T140:

Jeg kunne satt opp en skrotet laptop-pc der nede, og fått tilgang til hele 3D-modellen, ingen behov for tegninger utover alt. Bortsett fra problemer med støv og fingre med lim på, som gjør pc-løsningen utfordrende, så er gammeldagse tegninger ganske flott. De har ingen software bugs, wifi ramler ikke ut, og blir en tegning ødelagt, så printer jeg ut en ny. Tegninger på papir er bra.

T101 - høy, slank, tar lite gulvplass

Dimensjoner for T101:

h 1140mm (samme som de andre store modellene, fx T140)

b 495mm

d 244mm

T101:

T101 sammen med T140 - samme høyde, smalere og slankere:

(Switching to EN language for easier access to content for most of the world.)

Comparing Compact Horn to typical subwoofers

It is difficult to compare specifications, since other vendors rarely specify anything. But we can use data from independent reviewers, like this from Erin, a test of some small subwoofers:

https://www.youtube.com/watch?v=g2PCemcuRZE&t=675s

Real numbers sometimes are merciless. Their marketing tells a story about "14Hz", reality shows a very different situation. The small KEF, applauded by the "hifi-press", has around 10dB less output capacity at 30Hz, compared to the T6. That is a very significant and definitely noticeable difference.

The numbers presented by Erin in the video shows that the only thing those subwoofers have in common with the T6, is that they are all small size.

Output capacity, from the test:

T6:

Data in this graph is RMS 1m 2pi.

Important to keep track of conditions for measurements, and scale the numbers appropriately when comparing:

Peak = RMS + 3dB

1m = 2m + 6dB

2pi = 4pi + 6dB

 

Data show significant potential for improvement using Compact Horn acoustic loading

I have stated around 6dB improvement in output capacity, data form this test show more like 10dB or even much more, but mind that the T6 actually is slightly larger in size than those very small boxes. Still, a huge difference.

But those numbers does not tell the whole story, there is more, and I will try to explain that.

Usable capacity is much higher with acoustic loading

We see significant capacity increase, but reality is that the difference is even larger, when playing music content.

To reproduce low frequencies, a lot of air has to be moved. This means displacement, and that comes from cone surface area x cone travel, for a typical sealed design. So a small driver has to move a lot, to make sound at low frequencies. This movement is problematic, due to physical limitations in driver construction.

This excessive travel of the cone uses all headroom so it can no longer reproduce higher frequencies properly, so it will sound sluggish and "slow" on transients like drums, there simply is no impact. With acoustic loading, cone travel is reduced so the voice coil is operating within reasonably linear limits, enabling it to reproduce higher frequencies along with the low frequencies, simultaneously. Making drums hit with realism and impact, like they are supposed to do.

Simply adding more power does not fix the problem. Once the coil travels out of the magnetic force field, there is no force available to move the cone.

Motor design for long travel is also problematic. Bl can not be too high, or less the cone will simply refuse to move at low frequencies. A long coil, in a non-saturated magnetic field, also means high inductance with large nonlinearities, which further adds to sluggish and "slow" bass, because those non-linear inductance effects becomes stronger as frequency increases.

The solution is to have a large cone area, or change how the cone couples to the air. Acoustic loading like the Compact Horn changes the acoustic loading, making a smaller driver move air like a very large one.

Integration and time delay

In the review mentioned above, there was also measurements of delay, how long it takes for the input signal to come out as sound from the subwoofer.

We see delay is significant, where 15ms is 1.5 cycle at 100Hz:

This time delay must be compensated by adding delay to the main speakers in the crossover DSP, to achieve reasonable integration of the subwoofers to the main speakers.

The delay is a result of physics. A system with a heavy cone has longer delay, and on top there will be some delay through the processor/DSP in the amplifier.

In post #15 (https://www.kvalsvoll.com/blog/forum/topic/compact-horn-subwooferene/?part=2#postid-413) I show how the Compact Horn subwoofers perform, generally, with regard to delay. Conclusion was that propagation delay was in the order less than 0.5 wavelength. So they typically present much lower delay compared to sealed boxes with heavy-cone drivers.

Value of engineering vs propaganda-style marketing

With independent test data available, I have showed in numbers how new and more advanced technology can indeed achieve significant improvements. How this relates to listening impressions must of course be experienced 1. hand to understand, but numbers is at least a starting point. From a pure performance perspective, there is no contest.

The marketing I have seen for some subwoofers, like the ones reviewed in the test mentioned above, looks more like propaganda, where claims and statements with no foundation in reality are repeated so many times that people begin to believe. And typical reviews are just a quick subjective evaluation, with no measurements to validate those claims, so get a pass.

This is just sad.

One manufacturer, specializing in subwoofers, appears to be a nice, small, dedicated company, with some enthusiastic and dedicated people. Claims they have the "musical" subwoofers, when measurements show the subwoofer underperforms to a degree that it is not really usable as a subwoofer even at reduced listening volume. And then they present a story telling that connecting the sub to main speaker wires is the best for sound quality, when the subwoofer clearly has a propagation delay of 1.5 cycle at 100Hz. Proper integration is impossible, so it will never sound like a proper, good, integrated bass solution.

Then there is the typical "14Hz" claim. Measurements clearly show that subwoofer has no meaningful output at 14Hz. It is just nonsense.

So what can my engineering do for those companies. I can not fix the integration so it works properly when connecting to main speaker wires, it just can not be done from a system topology perspective. And I can not make that tiny subwoofer reproduce 14Hz in any meaningful way, for that you need something like the larger Compact horn units.

What can be done, is to design subwoofer units that perform significantly better for the purpose of reproducing music. Performance will be within constraints given, such as size and cost. Just much better, compared to what they have.

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