Yes. That's what I thought - and also read in the article linked by @Audentid14. Indeed, the inside speaker has not his cone covered with a damping nor blanketed by a curtain.
As you can see on the picture below, I choose to slant the internal speaker baffle, to tame some possible chamber and enclosure resonances :
I also padded and braced the inside :
Before fully filling the inside :
Sorry, I dis not took pics of the damping in the chamber, but I posted a description on post #220.
T
It may not matter but we always tried to make the air chamber between the two drivers as small as possible for better coupling.
This volume may be less important to the last spare inch if it is 100% air tight. The air volumes wheight also lowers Fs. Just keeping it as small as it is conveniant for the drivers should be fine. LINN even made it quite large for my taste and it worked.
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Yes. I never found clear or defined rules about dimensioning that intermediary chamber, except than purely mechanical, i.e. : the speakers must not touch themselves in operation, small as possible but not too small, some or no damping...
So here's the choice I empirically made :
I don't think that exhaustive studies on the subject have been published, like the one we find on Sealed or Bass-Reflex speakers. At least, I did not found one, so the article linked by @Audientid14 is a welcome additional knowledge...
T
If you know your physic's book, the Isobaric principle has nothing new to show. It is a problem solver if you got "the wrong" driver, but multiple of it. You can integrate the same result in a single driver just as well, halfing the cabinet volume needed.
I see it as a part of the speaker designers tool case. It may come handy in some cases, interesting but nothing sensational.
I see it as a part of the speaker designers tool case. It may come handy in some cases, interesting but nothing sensational.
Maybe the distortion reduction due to having one driver turned is underestimated.
It looks attractive to me to cancel like this nonlinearities out with isobarik alignment.
If box volume plays no rule then two drivers can be put close together one of them inverted without losing efficiency.
If put on opposite sides of the box reducing vibration (also one aspect) I am not sure if nonlinearities would cancel out as good as the drivers have more space between them.
It looks attractive to me to cancel like this nonlinearities out with isobarik alignment.
If box volume plays no rule then two drivers can be put close together one of them inverted without losing efficiency.
If put on opposite sides of the box reducing vibration (also one aspect) I am not sure if nonlinearities would cancel out as good as the drivers have more space between them.
Preparing a pair of cheapo drivers for subwoofer use
marble box will be in a corner and has a downfiring 8cm reflex port 45
cm long in 30 Liter volume.
clamshell alignment.
Spacing of 3mm is enough that the surrounds won't touch during work. Will be sealed with silicone for complete air tightness.
Although cheapo ones these have four holes in the basket ventilating the area below the yellow spider
nice mellow surround, lightweight paper cone.
no cone treatment here as the combined drivers support each other impressively.
Touching one driver immediately moves the other one.
I will try a 2300uF electrolytic for filtering and linearizing the response. But audition test will decide.
marble box will be in a corner and has a downfiring 8cm reflex port 45
cm long in 30 Liter volume.
clamshell alignment.
Spacing of 3mm is enough that the surrounds won't touch during work. Will be sealed with silicone for complete air tightness.
Although cheapo ones these have four holes in the basket ventilating the area below the yellow spider
nice mellow surround, lightweight paper cone.
no cone treatment here as the combined drivers support each other impressively.
Touching one driver immediately moves the other one.
I will try a 2300uF electrolytic for filtering and linearizing the response. But audition test will decide.
their price in egypt is 7 euro in the shop. I know these drivers in china are produced for 1 to 2 euro.
These are spare parts for bluetooth soundboxes. Its hard to get anything else in the country. So ideal use is here the isobarik alignment.
These are spare parts for bluetooth soundboxes. Its hard to get anything else in the country. So ideal use is here the isobarik alignment.
Is it wise to connect 6ohm drivers in parallel? The impedance will be somewhere below 3ohm for sure.
I will try however. After I heard someone abuses small class D chips with one ohm impedance and no failure I have no fear anymore.
see
However there will be 10 meters 0.5mm2 cable for connecting the sub. Will add a bit of resistance. Like 0.35 ohms
see
However there will be 10 meters 0.5mm2 cable for connecting the sub. Will add a bit of resistance. Like 0.35 ohms
Such a thin cable of that length will certainly have a bad effect on the sound. 0.35ohm will raise the Qts of your drivers, and reduce the damping factor of the amplifier. Tie them in series, it is not forbidden, in the counter phase of course.
yes, if the amp shuts down or gets hot, I would have to rewire in series.
Often 8 ohm drivers have in reality 6 ohms.
now the driver is ready for use, sealed with silicone to get 100% airtightness.
If Q is too high I still can add same size magnets to the drivers which I have in reserve and damp the box partially.
In a similar project a single same type driver did well without extra magnet or damping of the box. I couldn't believe myself. Maybe room resonances play a higher role than the Q of a driver in the bass.
Corner placement seems to make a big difference, too.
now finished just waiting 24 hours for the glue to settle
@NIXIE62
my experience with this placement
@NIXIE62
my experience with this placement
I built now several corner placed loudspeakers and subs with different bass drivers and box volumes.
Bass sweep tests showed always bass down to the lowest octave with low tuned reflex systems.
Bass sweep tests showed always bass down to the lowest octave with low tuned reflex systems.
Just for the occasion, the 475L with her nameplate on it, along with the 375L :
T
T
I like the classic design.
Also the Beyma drivers.
I have a pair of Beyma 8agn.
Hope they will be available again.
Beyma should make 18inch fullranges. It would be a hit.
Fane made a 15 inch fullrange with triple! cone.
Also the Beyma drivers.
I have a pair of Beyma 8agn.
Hope they will be available again.
Beyma should make 18inch fullranges. It would be a hit.
Fane made a 15 inch fullrange with triple! cone.
I used to have an incredible system. I had 4 JL Audio subs isobaric. It not only allowed me to use 4 subs in a smaller space but the sound quality was out of this world. I was using precision power amps. Back when they were high quality. Give it a try.
I used to have an incredible system. I had 4 JL Audio subs isobaric. It not only allowed me to use 4 subs in a smaller space but the sound quality was out of this world. I was using precision power amps. Back when they were high quality. Give it a try. I know that is not very technical, but I was very happy
After a while of listening tests between the 375L Bass-Reflex and the 475L Isobaric - with Audiophile and non-Audiophile friends - we can draw the conclusion that between the two models :
1 - the bass extension appears to be a bit deeper on the Isobaric, but we'll say that these are similar.
2 - the efficiencies seems to be slightly higher on the Isobaric, but we'll say that these are similar.
3 - the punch and transients are more underlined and controlled on the Isobaric than on the Bass-Reflex
Taking in count that :
1 - the test are done by instant switch box A/B'ing of the speakers on the same musical programs and amp (Accuphase E-560).
2 - the efficiency specs of the two models of Woofers (Beyma 12BR70 and 12B100R) is very close, both in the 93-94dB/W/m range.
3 - the crossovers are both 1st order serial/parallel configuration.
4 - the QTC of the Isobaric is 0.69-0.70 (critical is QTC=0.71), while the n on the Bass-Reflex is 5.4-5.5 (critical is n=5.7).
T
1 - the bass extension appears to be a bit deeper on the Isobaric, but we'll say that these are similar.
2 - the efficiencies seems to be slightly higher on the Isobaric, but we'll say that these are similar.
3 - the punch and transients are more underlined and controlled on the Isobaric than on the Bass-Reflex
Taking in count that :
1 - the test are done by instant switch box A/B'ing of the speakers on the same musical programs and amp (Accuphase E-560).
2 - the efficiency specs of the two models of Woofers (Beyma 12BR70 and 12B100R) is very close, both in the 93-94dB/W/m range.
3 - the crossovers are both 1st order serial/parallel configuration.
4 - the QTC of the Isobaric is 0.69-0.70 (critical is QTC=0.71), while the n on the Bass-Reflex is 5.4-5.5 (critical is n=5.7).
T
I can give subjective feedback on the sound of the clamshell isobaric of post 255 in this thread as I finished a 2.1 amplifier system with it.
Sub like all my corner placed low tuned reflex boxes reaches the lowest octave and gives a decent result for such cheap drivers.
Heard making of "Wish you were here" and "Dark side of the moon" from Floyd "Which one is Pink?"
Articulate enough to keep it going as is.
Sub like all my corner placed low tuned reflex boxes reaches the lowest octave and gives a decent result for such cheap drivers.
Heard making of "Wish you were here" and "Dark side of the moon" from Floyd "Which one is Pink?"
Articulate enough to keep it going as is.
now finished just waiting 24 hours for the glue to settle
@NIXIE62
my experience with this placement
@NIXIE62
my experience with this placement