Archive for February, 2010

A two way speaker using the SEAS CA18RNX and Vifa D27TG-05 drive units.

Friday, February 19th, 2010

This design is a two way.  Here is the box alignment for the woofer.

Note that the driver and port will displace 0.0408 cu.ft. in the enclosure, this will have to be added to Vb.  To get to Vt you will have to add brace volumes as well.  Mineral wool (Rockwool) should be placed on the back surface behind the driver.  50% of the internal surfaces should be covered with Polyfill.  Damping is included in Vb.

This is the crossover.  Chokes should be air core. L1L2.  The value is 1.5 mh, but this is close enough to 1.6 mh.

C1 and C2Ce.


The rise below 1 kHz is intentional to correct the diffraction loss of the cabinet.  The acoustic response is for a driver on a baffle, so when loaded the rise will continue to cut off as intended.  These Vifa tweeters have a slight rise in response at 15 kHz but there is no need to notch it.

The crossover point is at 2.8 khz and both drivers are down 21 db an octave either side of crossover.  The tweeter has an Fs of 1500 kHz and ideally the tweeter should be a little further down at that point, but I think the result will be satisfactory.  This could really only be corrected by selecting a tweeter with a lower Fs.

With the diffraction compensation these speakers have to be considered essentially five ohm.  The phase response is superior and the speakers are only 90 degrees out of phase at crossover.

When the boards are constructed the inductors should be spaced from each other as far as possible and their axes at 90 degrees to one another.

This is the port you will need, you will have to cut to length.

Loon Platform Rafts

Wednesday, February 17th, 2010

The Loons are in trouble in Minnesota and Wisconsin.  We are now thought to be as low as 700 nesting pairs in the two states.  The Loon is moving North to Canada.

The reasons are.

1).  The rising Eagle population that takes the chicks.

2).  Fluctuating lake levels, that leave the nests away from the water.

3).  Raccoons taking the eggs on the shore line.

4).  Boat traffic in nesting areas, especially big wakes that swamp the nest and can cause loss of eggs.  Also when the Loons get scared they can become “flusher Loons” and flush their eggs.

5).  The cold windy Springs we have had of late.  The conditions are brutal on the newly hatched chicks, that in natural nest are pitched by their mother straight into the water, never to return to the nest.

On Benedict Lake we are down to two nesting pairs.  Last year one chick was produced but did not survive.  The year before there were no chicks.

So, I was informed of this fact as my neighbors as they left for Florida in the fall.  They left giving me orders to fix it!

I was steered to the Mantrap Lake program by Ms Perry at the DNR office Brainerd, who informed me they would be of more assistance then the DNR.  Seems like another program that needs less money!

On Benedict Lake, the problems have been exacerbated by the American Army Corp of Engineers operation of the Federal Dam.  Now there is a government agency that goes around spreading harm far and wide.  That is definitely an organization that needs legislating into oblivion.  Please see the page on this blog on Red River Flooding.  The problem has occurred since the Corps lost their lawsuit filed by the State of ND over their operation of Lake Sakakawea.  The Corps can no longer empty Lake Sakakawea into the Missouri river to float barges on the Mississippi, so they are taking water from lakes like ours that drain to the Mississippi watershed.

So at Ice off the lakes are high.  Then as soon as the flood run off is gone, the Corps drop the Lake levels by opening the dams.

The loons nest the day of ice off on the shore line.  The Loons can not get around on land and have to abandon their nest.  This also causes increased predation by Raccoons.

The Eagle population has increased drastically and they love the chicks.

On Benedict Lake the Loons like to nest at the entry to the Benedict River.  Unfortunately far too many fishermen and boaters, do not obey the closed throttle rule on the river, swamping nests and scaring Loons.

So the Mantrap Lake Association has been studying the Loon and assisting breeding with a rafting program.  They have identified 19 nesting areas, and have increased the population of Loons to 19 pairs.

Loons return to the same Lake.  A lake that looses its Loons is far more lilely than ot to stay silent.

Yesterday with Don, a local Artisan we constructed the latest version of the Mantrap Raft, but modified, by allowing the canopy to hinge to allow this portly old chap to easily built the nest.  Here is a late model Mantrap Raft.

Now you have to deploy the raft the day the ice goes out.  Now for obvious reasons it usually goes off on a windy day, so boat control is a significant problem.

We will try and encourage nesting away from the river. There is a relatively sheltered area when Loons have historically nested, so we will deploy our first raft 15 ft off shore from this location.  We can only put the canopy 12″ up until we have our first successful nesting.

The rafts are deigned to accomplish the following.

Provide a stable nesting area for the nesting pair that is unlikely to be swamped.

The nesting ring prevents eggs rolling into the water.

The canopy prevents predation of chicks by Eagles.

The chicks never return to a natural nest but these rafts they do, and have been observed to use the rafts for 3 to 5 weeks following nesting.  The ramp is crucial here.  The black canopy provides shelter and heat, as the sun heats the black structure.  Chick survival is much improved.

Once the Loons accept the rafts, they expect them to be there each year, and follow their raft to safe anchor, and hop right in as the boat pulls away.

Loons have been known to fight to the death over rafts so once acceptance is achieved it is desirable to have enough rafts for the nesting pairs of the lake that use them.

It can take 3 to 4 years to get the Loons to accept the rafts.

There is some push back from Fishermen who feel deprived of these nesting areas in breeding season.  The rafts and the deployment are licensed by the County Sheriff.  When legally marked with official marker buoys fishermen can not approach the nesting area without risking severe penalties.

So we will see how this endeavor progresses this year.

This nesting program has been successful.  The raft has now been deployed for 4 years at ice out.  The first year the placement was less than ideal.  The next year the raft was deployed close to successful nesting area where one chick hatched and survived.  The next year the raft was deployed in the same place.  The loons built a natural nest that was predated right away.  No chicks resulted from that pair.

The next year 2012 the loons used the raft and two healthy chicks hatched which survived.

This year 2013 the loons again used the raft and two healthy chicks hatched which are doing well at just over 5 weeks of age.

It has surprised me how well wild animals take to a device like this.  However they seem content and safe in these rafts and do not stay head down most of the time.  They sit up surveying the scene like lord and lady of the castle.

Probe into Toyota throttle control intensifies, and now Chevy Cobalt electric power steering under scrutiny. Is new technology getting ahead of safety?

Thursday, February 4th, 2010

Are we letting new electronic car control systems outpace development of  fail safe mechanisms at times of failure?

Electronic devices and systems, have, and always will be prone to both unpredictable intermittent and sudden total failure.

When electronic controls and systems are used to control vital systems in cars, such as speed, steering, braking and shifting, there is grave cause for concern.  Added to which an automobile is a harsh environment for electronics.

Toyota’s recent problems with unwanted acceleration have brought these issues into focus. Worries are intensified by the fact that Toyota almost certainly has no clue as to the real cause of these incidents, but have come up with a couple of face saving sham solutions.  More likely than not this will result in larger helpings of egg on the old visage, giving new meaning to “loss of face.”

Today I had my Toyota Camry hybrid out to the dealer to get numbers off the radio/CD/GPS unit which has developed problems.  I understand from the service department this is not infrequent.  They checked the accelerator pedal and confirmed it as a Denso and not CTS.  They checked the recent recall data and said there is a carpet recall.  I told them that the carpet is firmly fixed by stout hooks, and the pedal hung from above, and nowhere near the carpet!  The service tech agreed.  With a twinkle in his eye said, “But we will be doing something to the carpet.”  Now the word so often used by  Click and Clack fits the situation perfectly: – “BOGUS!”  It is also a total waste of everyone’s time.

Toyota’s situation is rapidly deteriorating to farce.

However the issues remain serious.  This report leaves open to question whether under some circumstances the driver can exert any control over a Toyota vehicle at all.

This report gives credence to the belief that the accelerator pedal fix is a smoke screen.

Despite Ray LaHood’s retraction the Houston Police Department have parked their Toyota Camry Hybrids, and they are not involved in the pedal recall!

Toyota now have company with accidents caused by electronic controls in vital places of GM vehicles.  The electronic power steering in the Chevy Cobalt is now under intensive government scrutiny, after failure reports, accidents and deaths.  GM have this system on all their vehicles with engines 2.4 liters or less.  Ford say they will have the system on 80 to 90% of their vehicles by 2012.

From Wikipedia, this is the rational for moving to electric steering: –

[The aim of steer-by-wire technology is to completely do away with as many mechanical components (steering shaft, column, gear reduction mechanism, etc.) as possible. Completely replacing conventional steering system with steer-by-wire holds several advantages, such as:

  • The absence of steering column simplifies the car interior design.
  • The absence of steering shaft, column and gear reduction mechanism allows much better space utilization in the engine compartment.
  • The steering mechanism can be designed and installed as a modular unit.
  • Without mechanical connection between the steering wheel and the road wheel, it is less likely that the impact of a frontal crash will force the steering wheel to intrude into the driver’s survival space.
  • Steering system characteristics can easily and infinitely be adjusted to optimize the steering response and feel.

As of 2007 there are no production cars available that rely solely on steer-by-wire technology due to safety, reliability and economic concerns, but this technology has been demonstrated in numerous concept cars and the similar fly-by-wire technology is in use in both military and civilian aviation applications. Removing the mechanical steering linkage in road going vehicles would require new legislation in most countries.]

In pursuit of government mandates to stretch the gallon of gas ever further, manufacturers are forced into these complex high tech systems.  In order to keep prices down the temptation to compromise safety grows by the mandate.

So if this is the way of the future, the same rigorous testing review and oversight will have to be given to automobiles as aircraft.

In addition, it is instructive to note that in the errant Toyota vehicles no OBD fault codes have shown up, and the problem goes away at least for a period of time after re starting.  To me this indicates that like aircraft, automobiles will have to have black boxes, that record data form every sensor, every driver command and computer command.  If this technology was in Toyota vehicles now, I very much doubt any facts about these serious incidents would now be in doubt.  We would then be well on our way to the right fix.

The problem is that the cost of all this is likely to put the cost of vehicle ownership outside the reach of most.  Cost I suspect will not only be prohibitive in terms of cost but maintenance.  The cost of maintaining older high mileage vehicles will put them out of the reach of low income families.  The personal and family car is destined to become a luxury for the few.

This incredible news just in today.  Our government could not get people drunk in a brewery.  Our government seems bought and paid for through out and that’s sad.