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Old 4th May 2009, 11:38 AM   #151
tinitus is offline tinitus  Europe
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I have double 8" in closed
I have always wondered why they dont move much
Even if its loud and with loads of bass
Sometimes too much on certain kinds of modern music where bass is turned up
On films with heavy lowend effects the whole room is rumbling, to a degree thats really scaring
No subs needed fore that
So, I have loads of bass, yet woofers normally moves very little
Sometimes its almost not even visual, yet still playing bass
If they move a lot I really dont want to be in the room

I do know mine is far from perfect, but could the "impressive" movement" of your BR design be due to the BR getting unloaded below a certain frequency, where a closed is not

Is this a known difference between closed and BR
Im really just curious
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Old 4th May 2009, 04:08 PM   #152
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally posted by tinitus
I have double 8" in closed
I have always wondered why they dont move much
Even if its loud and with loads of bass
Sometimes too much on certain kinds of modern music where bass is turned up
On films with heavy lowend effects the whole room is rumbling, to a degree thats really scaring
No subs needed fore that
So, I have loads of bass, yet woofers normally moves very little
Sometimes its almost not even visual, yet still playing bass
If they move a lot I really dont want to be in the room

I do know mine is far from perfect, but could the "impressive" movement" of your BR design be due to the BR getting unloaded below a certain frequency, where a closed is not

Is this a known difference between closed and BR
Im really just curious
The movement is the result of the Sd area and frequency and pressure you want to generate.
How lower the frequency then the x must increase to maintain the sound pressure.
Till this isn't more possible the speaker loses acoustic resistance and the resonance frequency appears the Fs of the impedance.

With a BR system the port is tuned to the resonance frequency. At the tune frequency the air in the port resonates in opposite phase with the air in the box. Increasing the acoustic resistance for the driver.

Result the x decreases and the sound is radiated by the port and driver together. You see in the attachment the extrusion of the driver at 1 W and at 20W. The red line is the Xmax. That is the limit for linear behaivour of the motor of your driver.

At the attachment the same driver is simulated one(orange) in a closed box the other (yellow) in a bass reflex.

You can see at the closed box that after resonance the x stays constant and thus the sound pressure decreases. The -3dB point.

With the same driver in a BR cabinet the port increases the air load to the max at resonance so the impedance is then near R-DC and the movement decreases radical.

A good design has many air load because this means it radiates sound.
With a horn you virtual increase the sd. because (sd or throot) * X= Mouth horn * X. This creates a huge air load and thus SPL and good impulse behaivour.

In this design the port generates a good load for the driver so at can't resonate afterwards.
What to many a good or many bass is often a very bad impulse behaivour. So the driver resonates afterwards and creates a fat sound.

The waterfall of this driver is exceptional tight. Tight responding low frequency transponders sound not fat but do give fast peak responses and do not store energy in the system (driver box) and resonate afterwards.

I had back loaded horns they can produce very impulsive clean low distortion low frequency. But to my surprise this bass reflex came close to that sound.


So your speaker has a lot of low frequency to test if that is due poor impulse behaivour your can connect a battery and connect it for a second. Than you shout have a dry bop. If it is more a boinggg than it is a poor performing design.


Regards, Helmuth
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Old 4th May 2009, 05:41 PM   #153
Helmuth is offline Helmuth  Netherlands
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Here the attachment of the transfer closed -3dB at 50Hz and BR -3db 26Hz. That is the gain for the same driver when placed in a closed or BR-enclosure

In the attachment of the cone extrusion you can see the BR port does it work maximal at about 25Hz very low x. This you can also see when you look at the impedance. at 25 Hz almost Rdc.

When you use Winisd-pro it is easy to generate this data. This software is freeware!

You can also see when you look at the cone extrusion that the driver in the BR makes the biggest movement at 35Hz and at 18Hz. You can also see that the driver in the closed box has the same movement down to 35Hz as with the BR-system.

Regards Helmuth
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Old 4th May 2009, 06:21 PM   #154
Helmuth is offline Helmuth  Netherlands
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Good impulse behaivour is all about energy storage.

Here a interesting study about this theme.
stored energy

Here the stored energy in a crossover. 1st order performs the best. This is why also my design performs exceptional in the waterfall diagram.stored energy XO
Click the image to open in full size.


The fact that the sound is loose from the speaker is direct related to the off axes response combined with good impulse behaivour.

Regards Helmuth



Click the image to open in full size.
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Old 4th May 2009, 10:53 PM   #155
tinitus is offline tinitus  Europe
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Quote:
Originally posted by Helmuth


The fact that the sound is loose from the speaker is direct related to the off axes response combined with good impulse behaivour.

Regards Helmuth

Well, in that case I will have nothing to worry about


But thanks anyway, fore the details, your work is impressive
Though, may be a bit wasted on me
Im in doubt whether theory and reality really is the same

Amazes me that with your knowledge you take 6db filters serious, I thought we all had agreed long time ago that it really doesnt exist in real life
Are you sure it is 6db
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Old 5th May 2009, 06:00 AM   #156
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally posted by tinitus


Amazes me that with your knowledge you take 6db filters serious, I thought we all had agreed long time ago that it really doesnt exist in real life
?? explain your self.

For midrange bandpass you have to compensate the resonance frequency, and the impedance increase due the voice coil inductance.

For high you have to compensate the resonance but not in this case because there is only a little resonance impedance increase of 1,5OHM.

And for the woofer the voice coil and filter coil filter the high frequencies as a perfect 1 oct filter.

Quote:
Are you sure it is 6db
for 420Hz it is 6db/oct

for 3600Hz the midrange got 12db/oct to filter the breakup at about 5500hz.

And the tweeter is 6dB oct.


The best solutions are the simple ones this also the case with a 6dB filter, although you need drivers that can endure that.
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Old 5th May 2009, 04:29 PM   #157
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally posted by tinitus


But thanks anyway, fore the details, your work is impressive
Though, may be a bit wasted on me
Im in doubt whether theory and reality really is the same

And Tinitus,

If the theory is fault you shout proof that with a good example.

There is a lot to do where DR Geddes has done his part the relation measured values and the perception of these figures.

Regards Helmuth
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Old 5th May 2009, 11:34 PM   #158
tinitus is offline tinitus  Europe
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I havent found any measurement on individual driver slopes, just a simulation, that looks very far from any 6db
A bit hard fore me to argue on that basis
I can only say that when I tried simple 6db filter on my 3way, not long ago, I got ok sound, but also strugled with severe phase issues

Though I have done 2ways with 6db, with no problems
But I have no clew whether it actually was 6db
I have also done cheap 2ways with just a cap on the tweeter, and they were ok too

Personally I find it hard to do a 3way with less than 12db, as I need something adjustable, and a single component is not much to work with
And even so, 12db easily ends up being 24db, on the acoustic side

Your nice design is probably just teasing me

What provoces me a bit is your claims about the benefits you have from 6db, when its in reality probably isnt 6db, on the acoustic side
At least I havent seen measurements that proves it, or I may have missed them

But still, a nice well documented project, have been a pleasure to follow
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Old 6th May 2009, 12:32 AM   #159
tinitus is offline tinitus  Europe
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Quote:
Originally posted by Helmuth


And Tinitus,

If the theory is fault you shout proof that with a good example.

There is a lot to do where DR Geddes has done his part the relation measured values and the perception of these figures.

Regards Helmuth

I believe theres plenty of that around, where theory and practise are bent to match each other

As fore dr Geddes, you mention, he can probably prove just about anything to me, things I cant argue with, as I dont understand any of it

But that doesnt mean I have to believe it all
Lots of proven scientific "facts" that are proven wrong, years later
Right now hundreds of books are written about climate changes, by "scientists"
And they are probably all wrong, because they rely on computers feed with faulty "facts"
Happens all the time

Sure, Im a country boy, and proud of it too
So, most think Im a crazy fool, luckily my best friends say the opposite, so that dont bother me much

peace
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Old 6th May 2009, 06:36 PM   #160
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally posted by tinitus



I believe theres plenty of that around, where theory and practise are bent to match each other

As fore dr Geddes, you mention, he can probably prove just about anything to me, things I cant argue with, as I dont understand any of it

But that doesnt mean I have to believe it all
Lots of proven scientific "facts" that are proven wrong, years later
Right now hundreds of books are written about climate changes, by "scientists"
And they are probably all wrong, because they rely on computers feed with faulty "facts"
Happens all the time

Sure, Im a country boy, and proud of it too
So, most think Im a crazy fool, luckily my best friends say the opposite, so that dont bother me much

peace
To believe some one is good. But it is always important to make your own thoughts.
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