my tiniest speaker so far

[Heinrich]

I agree that the standard calculation is ...
´Natural´ was meaning solely the bass from the given driver+enclosure w/o heavy EQ or boost.

I don't think we come to terms. Lets give the aGnome, metaphorical speaking, some room to breath (despite its miniscule enclosure ;-)

In fact it's the contrary; I would have chose a higher Fb in order to gain middle bass level; tuning to i.e. the 30Hz region would have exceed x-mech of the passive radiators and limit the bass level. What is the interest of searching low-bass with such a concept?

But the deep notes are still in the signal, aren't they? Won't they make the driver exceed excursion limits anyway? More so, as they hit below tuning and see the driver un-loaded. Was that issue of unload solved recently without me taking note?

In France, a Vifa dome is more expansive than this Monacor and the reason of its choice is partly given in my first post. Fx around 2.3kHz is clever assuming the mid-woofer is fully able to go this frequency while limiting costs.

O/k, cost cuttings, But the Vifa would have allowed for
a) better vertical dispersion, especially benefitial if listener position is not fixed or distributed
b) less intermodulation, less distortion
c) better dispersion in treble
d) maybe, better linearity

It's funny to see that some people give their opinion on this speaker explaining that Vb is too low, that the mid-woofer is too small, that the tweeter coulfd be another and on... without staying connected to the initial concept.

The initial concept wasn't explained in too much detail:
"My goal was to create the most affordable standed/bookshelf speaker with an enclosure of H10.12” x W5.75” x D7.24”, so a size smaller than the well known LS3/5A."

For instance, regarding necessary compromise, what was the weigthing of quality parameters versus cost in money and/or size. Targeted listening volume, distortion, dispersion etc. What is the actual use case for which audience?

 

[Arindal]

But the deep notes are still in the signal, aren't they? Won't they make the driver exceed excursion limits anyway?

They are in the amplified signal as increased voltage, but it does not mean that they will drive the current or excursion noticeably.

In the region of the reflex tuning frequency, there is almost no active drivers excursion as the system of air and resonator mass reaches its maximum efficiency. Below that, impedance is usually increasing again so not much of power is drawn from the amplifier with the excursion slowly increasing. In a ´standard´ tuning, the spike in impedance below tuning freq is as high and broad as the one above. If you go even lower in freq, impedance will be getting closer to the minimum at tuning freq again while driver and radiator will act out of phase. Only in this region and below reserves of power and excursion are eaten up noticeably without usable SPL produced. That happens usually in the region of 1.5 octaves lower than tuning freq. So if you tune @55Hz as I would suggest, noteworthy energy below 25Hz will push the driver and eat up reserves overproportionally. Nothing that I would overly worry about. If you tune much higher, and play some fierce electronic music, you might need some sort of subsonic or highpass filter.

 

[Heinrich]

So if you tune @55Hz as I would suggest, noteworthy energy below 25Hz will push the driver and eat up reserves overproportionally. Nothing that I would overly worry about. If you tune much higher, and play some fierce electronic music, you might need some sort of subsonic or highpass filter.

But the deep notes are still in the signal, aren't they? Won't they make the driver exceed excursion limits anyway? More so, as they hit below tuning and see the driver un-loaded. Was that issue of unload solved recently without me taking note?

Now I see, the noteworthy issue of unloading below the reflex tuning frequency isn't that bothersome, you think.

I was tempted to show you and others some simulations on that topic. How excursion explodes below the tuning. I would also point to the literature. Then I thought, o/k, better to not come along as a professor.

I came to point to the measurements on this site. Every single bass reflex box, aka ported aka vented shows a little kink in distortion to lower values right on the tuning frequency, but going lower, man, booom (except for electronically /DSP filtered specimen, sometimes). I leave it to you.

I discussed the topic in 'my' thread on some little ones, that deliberately were intended, planned, designed and built to do the limbo, as a contender to the Purify route ... . See post #18 over there: https://www.audiosciencereview.com/.../sealed-mini-speaker-3-way.61896/post-2269574

Now I understand, why it didn't get a foot on the ground, except for quotations of look-alikes ... I personally leave it at that.

 

[agnostic1er]

The initial concept wasn't explained in too much detail:
"My goal was to create the most affordable standed/bookshelf speaker with an enclosure of H10.12” x W5.75” x D7.24”, so a size smaller than the well known LS3/5A."

For instance, regarding necessary compromise, what was the weigthing of quality parameters versus cost in money and/or size. Targeted listening volume, distortion, dispersion etc. What is the actual use case for which audience?

My first goal was to create a passive speaker of this size. Second goal was to limit the cost to the maximum. No targeted parameters, just seeing if I could make a speaker which would give me a listening satisfactory with so little money.
IMHO, I succeeded. Otherwise I wouldn't have posted this topic. I firmly believe targeting quality parameters for such a tiny speaker is senseless, except if going DSP/active.

 

[Heinrich]

What I see in the horizontal dispersion graph reminds me of the Peerless TC9FD wideband driver. At least it doesn't resemble a typical 1" dome tweeter that much. So, to take the TC9 would have been an option, having much wiggle room for an arbitrary low x/over to the bass. The x/over frequency would eventually be dictated by the cost for the passive components alone.
As already discussed, the lower x/over frequency would improve the vertical dispersion a lot, and minimize intermodulation. The TC9 is pretty cheap at 15. When experimenting with it, it felt a bit dull, not sparkling, but clarity in the mids was very convincing.

Regarding the bass, still I would ask for a tuning to 40Hz. You know the Fletcher/Munson curve. These show, that trying to design for bass at 40Hz, but not being able to output like 60dB@listening distance doesn't make much sense. It would stay below the threshold of hearing anyway One might extend the argument further, and weigh output capabilities versus extension. I think it is quite plausible to do so.

But reiterated, the un-loading of the driver below the tuning frequency sets a limit. Excessive excursion below tuning frequency is prevented, if the driver has a stiff suspension, but that counteracts a proper Helmholtz alignment. I finally simulated the SB Acousics driver in 4 liters, tuned to 40Hz and 50Hz respectively.

The 50Hz tuning isn't the worst in the world, but 40Hz looks better.

Are you going to follow the concept further?

 

[Arindal]

I would ask for a tuning to 40Hz. You know the Fletcher/Munson curve. These show, that trying to design for bass at 40Hz, but not being able to output like 60dB@listening distance doesn't make much sense.

Sounds like a contradiction to me, particularly in a passive design with given volume and woofer. You want to tune the reflex lower in order to have less SPL over the complete bass band, significantly down from the 100Hz level, and then claim insufficient SPL at 40Hz is anyways inaudible?

I finally simulated the SB Acousics driver in 4 liters, tuned to 40Hz and 50Hz respectively.

4l is by far insufficient for this driver if you want real bass. 14l would be ideal if you tune below 50Hz.

The 50Hz tuning isn't the worst in the world, but 40Hz looks better.

Do not really understand the point of such tuning. The level would be -8dB down anyways @50Hz compared to 100Hz. The lower you tune, the more level you loose in a broad band between 40 and 120Hz. Your simulation proves it.

The other aspect of choosing an enclosure which is too small and tuning the reflex comparably low is that you have a broad freq band in which the woofer and the radiator play in parallel. Which means the character of the bass reproduction is influenced by the passive radiator.

@agnostic1er if you ever feel the necessity to alter the bass tuning, I would recommend to exchange the active woofer for the

SB Acoustics SB12PACR25-4

or any derivative thereof. Thanks to different TSP, it might allow a much for effective reflex in 4l.

 

[agnostic1er]

Are you going to follow the concept further?

No. I only sporadically listen to them. I usually listen to much bigger speakers.

 

[agnostic1er]

@agnostic1er if you ever feel the necessity to alter the bass tuning, I would recommend to exchange the active woofer for the

SB Acoustics SB12PACR25-4

or any derivative thereof. Thanks to different TSP, it might allow a much for effective reflex in 4l.

I simulated the SB12PACR25-4 in the same enclosure/radiators: a few Db gain at 40Hz but a same loss up to 150Hz.