I don't think the sealed box are really out of fashion... But if you want to reach a low bass extension, the enclosure has to be quite wide and built with the suitable Woofer to maintain the QTC=0.71, which represents the optimal compromise between volume / bass extension / linearity / impulse response.
To "rival" my DIY bass-reflex 3-ways 375L, I designed a 4-ways sealed enclosure, using a Beyma 12BR70, still available today :
With a neat VB at 115L, I should reach F3=44Hz, F6=34Hz, F10=24Hz, with the excellent transient and damping characteristics tied to the sealed enclosures...
No prototype is built for the moment, but it will come !
T
To "rival" my DIY bass-reflex 3-ways 375L, I designed a 4-ways sealed enclosure, using a Beyma 12BR70, still available today :
With a neat VB at 115L, I should reach F3=44Hz, F6=34Hz, F10=24Hz, with the excellent transient and damping characteristics tied to the sealed enclosures...
No prototype is built for the moment, but it will come !
T
Manufactures seldom use "efficiency", describing a loudspeaker with an 80dB sensitivity at 40Hz as having 0.6% efficiency does not sell well
.Sensitivity is usually defined as on axis SPL in dB at 1 watt electrical input, measured at 1 meter.
A cone loudspeaker’s sensitivity is usually measured using an infinite baffle, a half sphere radiation.
The voltage used is often 2.83 Volts RMS, which is 1 watt into an 8 Ω (nominal) speaker impedance, though that same voltage would be double the power into half the impedance, or half the power into double the impedance.
Since a speaker’s sensitivity and Q (radiation pattern) varies with frequency, a single sensitivity number is not very useful in comparing loudspeakers.
Converting sensitivity to efficiency is possible.
https://sengpielaudio.com/calculator-efficiency.htm
The 0 dB reference level for sound is 10−12 watts.
1 acoustical watt is 120 dBSPL.
The standard measurement for a cone loudspeaker is done with it mounted flush on an infinite baffle radiating into half space at a distance of r = 1 m.
The resultant factor 2π × r2 (area of a half sphere) equals −8 dB. Therefore an efficiency of 1 = 100 % for a sensitivity of 120 − 8 = 112 dB.
This calculation is correct for a loudspeaker radiating in a hemisphere, 2π. Otherwise you must add the Q factor because of directionality.
Spherical radiation Q = 1, hemisphere Q = 2, quarter sphere Q = 4, and eighth sphere Q = 8.
Note that using the above calculation, efficiency of over 100% is possible for high Q devices like narrow coverage horns which can have on axis sensitivity of well over 112dB.
If the horn driver had uniform radiation over a half sphere, it’s efficiency would be under 50%.
Art
The HighEnd Kartesian are really interesting units - but so expensive. You can buy a Purifi for that money.
That's the thought I have with everything they have basically.
Unfortunately I have to say.
yes exactly. acoustic suspension has the box air spring as the dominant stiffness. The lower the suspension stiffness, the smaller box can be used for the same Qtc and same sensitivity. The ideal sealed woofer has thus a low Qts due to a high compliance suspension. The current paradigm about a high Qts suited for sealed is completely misunderstood. Same with the EBP rule for vented vs sealed
In a day and age of active systems are easy to make and in some cases even cheaper compared to passive filters, it's not all that interesting.
Although the truth is, that's also a bit of a simplified explanation if we don't look at other parameters, like apparent power from the amplifier as well as peak voltage from the boost EQ. (Well the last ine will be a cut EQ in this particular case).
I have never noticed the paradigm. It has always been a mix between Qt, VAS and Fs.
But also still ONLY as a very rough rule of thumb.
Just model and simulate it in your favourite software program.
It takes less than 5 minutes to get a first impression.
Or you 3d-print them yourself:
Quite an interesting project (even if I doubt the enclosure thickness is ideal).
Or you contact @Kravchenko_Audio
I have been following that 3D printing guy for a while as well.
Totally admire the whole idea and concept.
I personally wouldn't go as hardcore, like not 3D printing the surrounds.
Also there is only very minimal amount of verification (measurements etc) going on.
So a lot of ideas are just theoretical and hypothetical and nothing more.
Don't get me wrong, that doesn't take away the care that's being put into it.
But it's hard to find the practicality of it.
I use their 8" "PA" driver - it's not cheap but also very good. I also used/measured one of their small midranges with paper membrane - very nice unit, just not very loud. But as soon as you jump to their HE series ... they are too expensive.
I know, but that much better than say like a BMS, Eighteensound or B&C for the right application?
Yes they are.
Or are you now gonna tell us that all these equivalent lumped circuits and fundamental rock solid theory behind is is all BS?
In that case I wonder why you're spending time on a forum and not write an AES paper?
Which must also result in a Nobel price, since it means that fundamental physics has to be rewritten.
Well that statement is at least inconplete the way it is written. Bare drivers are definitely minimum phase devices. For the complete speakers it depends on how they are crossed-over. Crossovers like Linkwitz Riley for instance have allpass behaviour and are therefore not minimum phase.
Regards
Charles
The fact that loudspeakers can be modeled in equivalent circuits already means that they MUST be minimum phase.
Otherwise there is nothing to model.
But hey, this concept is just only already known from about 1870s-1880s
For those who have quite some catching-up to do, this is a easy start;
https://en.wikipedia.org/wiki/Mechanical–electrical_analogies
But I would recommend reading some proper literature actually.
For my application - yes. They are very low loss and have low THD at low levels - what for e.g. a 8NMB420 does not have.
For PA use I would not trust them enough and sensitivity is not high enough, I would chose PHL instead.
But I only tested about 10 8", the newer B&Cs look interesting.
right, I understand what you're saying.
There is basically a gap in the market here.
PA-like speakers that actually don't look like a turd and also perform like hifi speakers (aka, not stripped down because it doesn't matter at 110dB SPL anymore while half the crowd is drunk anyway), but just with more sensitivity and headroom.
I'll just toss this into the fray as potentially of interest: https://www.diyaudio.com/community/threads/dsp-assisted-reflex-system.404349/page-5#post-7552138 Among other things, it describes how the Linkwitz Transform can be applied to vented systems. PM if you want a copy.