Best bass from a closed-box compact standmount speaker?

[alankila]

https://www.spinorama.org/?quality=high&page=1&power=active&sort=f3

Maybe Buchardt A10? (I believe A500 is discontinued.) It is 2-way, not absurdly expensive, and seems to be <20 liters, and maybe these Purifi things really can work all the wonders they are claimed to be capable of.

Bass takes surface area, especially if it has to be from a sealed box, so don't expect an entirely compromise-free result.

 

[DanielT]

nice catch! Amazing scientific level in those days. There is also a nice article about Doppler distortion in the same issue.

What do you think Lars, if we take a 20 liter sealed box, let's say f3 40Hz. Then with a maximum of 10% distortion at 40Hz. How high SPL can you get under those premises do you think? It doesn't have to be with Purifi drivers but just what you think in general, that's if you think about what drivers Hifi/PA that are on the market.

 

[Arindal]

Maybe Buchardt A10?

Thanks, will give these a try as they look pretty attractive. They seem to reach pretty low, with power from the amp seemingly limited compared to Kii and Devialet. I wonder how loud they would play in their lowest octave.

if we take a 20 liter sealed box, let's say f3 40Hz. Then with a maximum of 10% distortion at 40Hz. How high SPL can you get under those premises do you think?

My guess would be it is a matter of linear excursion capability and power reserves/handling. The number of drivers reaching 40Hz in a compact sealed enclosure ´naturally´, i.e. w/o boost, is seemingly limited, and comes with rather low efficiency.

 

[Lars Risbo]

Radiant clarity 6.2
March Audio Sointuva AWG
AsciLabs A6B or similar, in the future
There was a studio monitor with 8" Purifi I think at one stage.

Also doesn't pushing huge excursion in a tiny sealed box create it's own problem with air pressure linearity?

air pressure? it’s not as terrifying as some describe it. Second order distortion is roughly the ratio between volume displacement of the woofer and the box volume. For example: a 6.5 long stroke has about 100ccm of linear Vd and this gives about 1% HD2 in a 10L box. This is more linear than even the best suspension. Moreover, this nonlinearity is of the suspension type and does not produce much IMD - it’s mainly adding harmonics to the bass and that is less audible that full band gain modulation (IMD)

 

[Lars Risbo]

Thanks, will give these a try as they look pretty attractive. They seem to reach pretty low, with power from the amp seemingly limited compared to Kii and Devialet. I wonder how loud they would play in their lowest octave.



My guess would be it is a matter of linear excursion capability and power reserves/handling. The number of drivers reaching 40Hz in a compact sealed enclosure ´naturally´, i.e. w/o boost, is seemingly limited, and comes with rather low efficiency.

once you spec F3 and box volume then sensitivity is given by Hofmanns iron law (passive speakers).

SPL is given by the volume displacement: p=Vd•(2pi•f)^2 •rho/4/pi/1m (for 4pi free field radiation at 1m). If Vd is 100ccm (rms) then SPL is about 88.5dB at 40Hz at 1m 4pi. for stereo and with boundary effect we can add 12dB

 

[Heinrich]

nice catch! Amazing scientific level in those days. There is also a nice article about Doppler distortion in the same issue.

Maths in a magazine, how dare you!

air pressure?

Leakage for one is strongly non-linear, and then one needs a leakage path because of environmental air pressure changing with weather.

I wonder what will come out of this survey ;-)

 

[DanielT]

once you spec F3 and box volume then sensitivity is given by Hofmanns iron law (passive speakers).

SPL is given by the volume displacement: p=Vd•(2pi•f)^2 •rho/4/pi/1m (for 4pi free field radiation at 1m). If Vd is 100ccm (rms) then SPL is about 88.5dB at 40Hz at 1m 4pi. for stereo and with boundary effect we can add 12dB

That was interesting.

Speaking of boundary effect and what @mhardy6647 said in #17 : stick 'em in corners of a room. I immediately think of Klipsch and something like this:

But not just Klipsch. In the Hifi Stone Age era with low powered amps/speakers, there were many who used corners for extra acoustic boost, here are a couple of Norwegian Tandenberg speakers for example:

Then I don't know if it was a popular interior design style at the time to squeeze speakers into corners? Maybe it was. Or it became a popular style because of necessity?

Anyway, nowadays we have a lot of nice amp watts on tap and speakers with good power handling so corner placement of speakers is no longer really needed. Now we have the opportunity to place the speakers in the room so that it sounds good. Speakers squeezed into corners definitely limit that.

BUT small sealed box and use the floor for extra acoustic boost? Down fiering woffer/driver that is. Extra bass boost plus flexibility with speaker placement. If we play with the idea, 20 liters, three-way speaker with down fiering bass woofer/ driver. Maybe that could be something?

 

[MarnixM]

But the idea is good, will search for an 8" sub driver with better-matching parameters which might reach lower in a 15l net enclosure and require less boost.

Used the SB Acoustics SB23MFCL45-4 Subwoofer in a closed box with net 16 liter contents, downfiering. Pleased with the result.

 

[Lars Risbo]

Leakage for one is strongly non-linear, and then one needs a leakage path because of environmental air pressure changing with weather.

indeed very nonlinear but normal good design eliminates that even if allowing pressure equalisation from transport and weather changes.

 

[Lars Risbo]

Maths in a magazine, how dare you!

yes, times were different back then.

 

[Lars Risbo]

driver size: large 12” drivers or beyond won’t necessarily help for small boxes. The driver Vas (equivalent volume of the the suspension ) scales with driver Sd squared, ie linear size in the 4th power. A good passive box alignment requires a certain ratio of the box volume and Vas. this means that large drivers need larges boxes. small boxes that go deep have this small drivers and long stroke to produce some SPL

 

[DanielT]

I used two JBL bass drivers in an isobaric con to cone configuration. Isobaric = less box volume is needed. Maybe something for TS to think about?


Placed downfiering in my DIY subwoofer. Up in the right corner of the picture:

More than 20 liters bass box though.I might have made a smaller box considering the isobaric configuration and the JBL drivers Vas (2.4ft³/68 liters) but that subwoofer got the size it got.

There was a hell of a bass with them. I don't know if it was "good" Hifi because they were car bass drivers (which I bought very cheap, bought because it would be fun to test)
(then I accidentally destroyed those JBL drivers but that's another story)

The red curve is the sealed box with that JBL driver. One driver in a 50 liter box. A number of years ago so I may be remembering wrong regarding that 50 liter:
(Shouldn't it be bigger box? Never mind, it doesn't matter.)

 

[mhardy6647]

nice catch! Amazing scientific level in those days. There is also a nice article about Doppler distortion in the same issue.

Audio was a marvelous publication - and had a (relatively) long life before the "hifi" parade, sadly, passed them by.

 

[Ziltoe]

Beside of all the above and good recommendations, did ya find meanwhile your "Best bass from a closed-box compact standmount speaker?" Do you have a preference now
from what has been recommended?

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