The Obama administration has showed total incompetence over this oil spill disaster in the Gulf of Mexico.

That have ratcheted up rhetoric and getting knee deep in lawyers, before attending to the job at hand.

From the beginning BP should have been allowed to focus all their energy on the leak.  The administration seem to have no clue what 450 atmospheres at the end of a 26 inch pipe means.  Admittedly the pressure of the ocean is 150 atmospheres, but that still leaves 300 atmospheres at the end of the pipe.

They have no clue as to the cooling effect of rapidly expanding methane and the vital need to exclude water from the collection process.

If they had done their home work, they would have known that no deep water well leak has been shut down without a relief well.

Instead of using the formidable organizational resources  of the American military to carry out clean up at sea and on shore, they have allowed federal agencies and departments to run amok.  Just look at the red tape that has got in the way of building the berms to keep the oil out of the marshes.

Instead of continually grandstanding and bashing BP, President Obama should have been bulldozing the Federal bureaucrats out of the way, and streamlining the federal response.

He is now risking US British relations with his rhetoric.  The Mayor of London, Boris Johnson, has been highly critical of the presidents response.

The Administration’s hysterical rhetoric is likely to drive BP to bankruptcy, which will leave affected business owners and employees in the gulf region sucking air.  If that happens it will largely be President Obama’s fault.

BP and its survival is very important to the UK economy.  For one reason one in seven BP retirement pounds is invested in BP.  An awful lot of US funds are also invested in BP.

Here is a another article encouraging BP leaving its American corporation behind.

David Cameron the new PM of the UK, seems on track to be as daft as President Obama.

What is required now is a supreme concentration on curtailing and mitigating this disaster, inquiries, hearings and lawyers can wait.

The trans Atlantic spat seems to be hotting up and Obama is getting a bad press in the UK.  This daily Telegraph editorial is on target.  However the reader comments from both sides of the Atlantic give the best insights into this developing rift.

Obama needs to be called out on his personal agenda.

Judging by numerous Net blogs you would be entitled to believe we have a nation whose collective IQ is equivalent to pig dribble.

It seems science has not be taught in our schools for generations.

The fact is that this environment on the ocean floor is more hostile and difficult to work in than outer space.

All humans tend to underestimate risk prior to unforeseen events.

It seems an operator made a mistake back in early March and drilled out a vital seal. A very human error. The rig operators fought against tragedy and lost. You can’t just pull the pipes, the gush would be catastrophic. The weight of a mile of rock above the well makes the pressure enormous. It is apparently 10,000 PSI. That is twice the pressure in a diesel injector that atomizes fuel. However this is not a pin sized hole, but a 26″ pipe with three pipes down the middle.

When the well blew the BOP actually worked and closed all pipes but the drill pipe, was only partially closed. This is probably why BP thought that this would not be a major event at first. What they did not know until after top kill was that the oil was coming up around the pipes, posing a severe risk of total well blow out.

The top kill almost certainly did a lot more damage and opened up passages in the BOP and increased oil spill.

Worry over the fact the well might blow totally, with unimaginable consequences, has prompted the riser cut. This to lower resistance and make total well blow out less likely.

Unfortunately as can be seen from the videos, oil flow has dramatically increased since the riser was cut; a lot more than 20%, that’s for certain.

Unfortunately the riser cut could not be one cleanly, and the riser is slightly bent, stopping the collection device from seating against the BOP. At the moment it looks as if the cap has come off the BOP.

A tight seal is important as leaks will make the jet of water entrain cold water. This will defeat attempts to warm the water up. As the methane gas is released it will cool quickly, just like in a heat exchanger in an air conditioner. This will cause hydrates of methane and ice to form and prevent flow up to the ship. I personally doubt anything further can be done to control this leak on the sea floor, and think far more likely than not the present scheme will fail.

So most likely this horrendous gush of oil will continue until a relief well is placed in the correct spot and bottom kill accomplished. As far as I can find out, no relief well has got to the correct spot until at least the fourth attempt. I think we will be very lucky if bottom kill is accomplished before the memorial weekend. I further believe that no matter how many resources a thrown at this clean up efforts will be largely window dressing until bottom kill is accomplished.

For the record, you can not place silk curtains to do the job. You can not drop heavy objects on it, because in water they are not heavy, because of the Archimedes principle. You can not drop explosives or nuclear devices down a pipe flowing under 10,000 psi. Because of damage done to the BOP during top kill and above all from information learned during the top kill event, placing another BOP on top of the one above the well is no longer an option.

Conspiracy theories are really dumb. Of course BP would like to get this stopped more than anyone.

The eruption of Eyjafjallajökull in Iceland is creating quite a pickle and getting worse and more serious by the day.

The incident is showing the impotence of western governments and leadership.  Dither is the order of the day.  Strong action and leadership are required.

First item of business is to listen to the right expert, and understand what he is saying.  The situation has thrown up The Man of the hour Haraldur Sigurðsson, a supremely eminent Icelandic Volcanologist.

I first became aware of this eminent scientist  when Al Roker interviewed him on 04/16/2010.  At once he impressed, by being quite honest about the limits of his knowledge.  He gave is opinions in a delightfully dour Scandinavian way reminiscent of the Scandinavian characatures on Prairie Home Companion.

His basic position was that he did not know how long this eruption would continue, but that even if it subsides, there will be frequent discharges over the next year to 18 months.  Further the possibility of even larger discharges in the near future from other dormant volcanoes in the area was very high.  He felt that Europe was in for a prolonged period of disruption of air travel.

You can read his blog here.  It has to be translated by Google from Icelandic, so you will have to read it carefully.

Here is a page of quotes from  Haraldur Sigurðsson which are quite funny.

There are problems rapidly building in Europe.  Large numbers of people are stranded without adequate food and shelter and out of funds.  Yet the government fondly imagine this will all magically end.  Well it might, but more likely than not it won’t.  These individuals need protection and plans made for repatriation in face of the likely probability this situation will not soon end and if it does will likely soon recur.

Fresh produce in Europe is running short, and will to all sense and purposes disappear from warehouses and shelves in the next day or two.

It is not too soon for the Royal Navy to requisition Cunard’s ships and prepare to repatriate the stranded.

Its time to stop electioneering and get down to the serious business of government.

04/18/2010.

It now seems that the extent of this infamous volcanic cloud over Europe is based on a computer model and not hard data!  This will probably be as misleading as computer models of C02 induced global warming.  Modern man is lazy and wants results from the arm chair.

However there is still a problem as volcanic ash is harmful to jet engines, that is hard data.  The volcano is spewing large amounts of harmful material which is going somewhere.

Test of aircraft over European air space have shown no sandpaper effect on the cockpit wind shields and no engine damage.  More hard data.

Today a data gathering plane flew from the British Isles over the Atlantic and ran into harmful pockets of volcanic material.  More hard data.

A BA jet airliner, flew for four hours over the Atlantic and has returned to Cardiff, where the engines are receiving intensive inspections, the results of which are expected tomorrow.

So the suspicion is that the computer model only shows areas where an airplane could encounter dangerous concentrations of  volcanic material, but probably won’t.

Now Satellite imagery is of little help in knowing where the ash is.  So the only solution is to send lots of aircraft frequently into the debris field to get hard data.  The problem is daunting because the area over which potential problems could be found is vast.

So if after flights resume while this volcano is still active and spewing and a plane encounters a problem, the faith and trust of the public will be lost, and people are unlikely to fly where a computer model shows there could be a volcanic ash.  So this problem is not easily solved, and I suspect that with all the care in the world, the safety of the air space down wind of this volcano is to an extent going to be based on an educated guess.

In the meantime the situation for people trapped on other continents by this dilemma continues to worsen rapidly.

The British Government are negotiating putting an air hub in Spain.  Then requisition ships, and putting them under naval control.  Passengers would the go by ship from Spain to the UK.  Residents of continental Europe could make their way home by rail and road.  This seems like a plan that should be activated immediately.

Here is a cost effective three way speaker.  It uses the paper coned Peerless SLS 830668 woofer, the Audax carbon fiber HM130C0 as the mid range and the soft dome Vifa 27TG-35-06 Tweeter.

This makes a very decent three way speaker with an F3 of 26 Hz.

Here is the optimal box for that woofer.

Note that driver and vents will displace about .2 cu. ft.

Here is the sealed mid range cavity.

The driver displaces about 0.01 cu. ft.

Here is the crossover.

These second order APC (Linkwitz Riley) slopes, which produce composite slopes that are pretty much third order.  The cross over points are 350 Hz and 3 kHz.  This allows for the band pass to be 3 octaves, encompassing most of the speech discrimination band.  Minimum impedance is five ohms.  There is optimal diffraction compensation.  There is a slight peak centered at 650 Hz from the mid range driver of 3 db which has not been notched.

I would feel inclined to build the speaker with a narrow top and broad base.  It will not matter if the band pass enclosure is over sized.  I would put the tweeter at the top, with the band pass driver below, and the a board below that to make the top of the speaker enclosure the tweeter/band pass enclosure, and have the bass enclosure below that.  Quarter round should be placed as trim all round the edge of the front panel.  It should be an attractive good performing speaker.

Now it is well known I have been highly skeptical of automated room correction and Eq systems.  I did have a demonstration of Audyssey from Kris Kyriakakis of USC.  He was using  SVS MTS-01 speakers to demonstrate Audyssey at SOTU.  In all honesty I was underwhelmed by the demonstration.  I thought the bass was improved, but that overall the sound was worse.  Kris canceled all except low frequency correction and then things were improved.

So after doing a careful manual set up and calibration of my updated rig, and living with it for a few days, I unleashed Audyssey on my very unusual system not expecting it would make any sense of this highly unconventional system.

The most unconventional are the front three, especially the main front left and right speakers.  So it is necessary to give a description of operation.

As many know I’m a full ranger at heart, and regard all crossovers as a necessary evil.  So the concept is to keep the system as close to a full range driver as possible.  In fact there is only one complete electronic crossover in each three fronts.   These are between bass/mids and tweeters. The mains contain independent aperiodic transmission lines.  The center is a single line.

The 7″ drivers in the mid line are allowed to roll off in the bass acoustically.  F3 is 42 Hz, 44Hz for the center.  The bass line has an F3 in the room of 23 Hz.

An active crossover sends the bass and step response correction to the upper of the two 10″ drivers.

The LFE signal is low pass 60 Hz and fourth order roll off.  This signal is sent to the amps powering the lower of the 10″ drivers.  The LFE signal is also sent to mono sum buffer amp and then sent to the amps powering the upper 10″ drivers along with the diffraction compensation signal.  This is to keep the diffraction compensation stereo.  Diffraction compensation is performed by the 10″ driver and not through the 7″ drivers, to off load them and prevent large cone excursions.

There is a low pass crossover that provides diffraction compensation to an amp supplying the upper of the two drivers in the center speaker.  One of the biggest reasons for an active crossover is to have precise control of diffraction compensation which varies greatly with speaker boundaries and room placement.  This is in no way possible with passive crossovers and is a big advance in accurate reproduction.  The design concept minimizes phase shifts and time aberrations due to crossover artifact.

The surrounds are sealed  speakers with Dynaudio drivers with a Fs of around 50 Hz second order roll off.

The rear surrounds are biamped dual transmission lines.

The system is optimally configured with all speakers set to large, and the speaker bass management set to both with the LFE crossover at 60 Hz.

A careful level calibration was done prior to utilizing Audyssey.

So I set up the rather cheap feeling calibration mic in the first position on a tripod.  I plugged the miserable small gauge mic cable into the jack on the front of the AV 8003.  With not much optimism I started the calibration, of the staccato tones played via each speaker in turn and at the end all three fronts.  There were two false attempts from problems such as a noisy fly that got in the room.  However third time lucky.  I measured in six positions.

So then I checked results expecting to see nonsense.  Well I was dumbfounded that it had done the speaker set up as designed.  It did not change any speaker levels from my calibration, and imagine my surprise when I saw it had figured out all speakers should be set to large and the LFE crossover at 60 Hz!  All just as intended.

The only confusion concerned the woofer distance.  It placed the woofer 5 ft behind the mains, and yet they are the same driver.  I thought about this and realized the program has averaged the driver and port arrival times.  This I had to reverse and manually put woofer and main speakers in the same place as there would have been phasing trouble with the upper diver as it is receiving a mix of signals.  It also altered the distances of the other speakers from measured.  However I think this has had a highly beneficial effect on getting a more even result though out the room.

Here are the results of the Audyssey frequency response correction.   In the main except for the surrounds between 1 and 2 kHz the mid band correction was insignificant.

However for all speakers except the rear surrounds there was a first order lift put in place above 8 kHz.  I think this was because in three of the testing positions the microphone was close to the rear surrounds.  There is a fall off of HF with distance and this in my view should not be corrected.  Listening test confirmed this.

The system sounded better with the frequency response correction canceled.

However I was intrigued by this, so I did and experiment purposely introducing a frequency response error.  I boosted the level of the bass amps to the rear backs below 150 Hz by 7db.  I did a run of Audysey and it caught the problem and corrected it.

So in summary I think this program is useful and may well take the edge off loudspeaker errors.  I suspect this is much more a loudspeaker correction program than room correction in a lot of cases.  For instance I know my surrounds have a slight null between 1 and 2 kHz that was identified by Audyssey.

I feel the most useful aspect in my studio was the re timing of the speakers.  I think this made a difference in two areas.  The sound is more uniform over the seating area.

However I think the greatest benefit was the improved sense of space achieved in 7.1 reproduction, especially.  I was definitely hearing different spaces captured.  In essence the reproduction was to a very large extent freed from the boundaries and constraints of the room.

I will make more comments about this when I report on some of the discrete multichannel discs I have listened to.

My biggest issue with the system is what I feel to be inappropriate last top octave equalization.  I would encourage adopters to be alert to this.

My preference would be for Audyssey to only make cuts in the top octave and leave alone any high frequency loss above a first order roll off.

I have to say I was fascinated evaluating this system and regard it as a work in progress.  I think we are early in total system/room Eq and suspect there is still a lot to learn.

Now there are increasing numbers of operas on Blue Ray.  It was time to upgrade the studio to take advantage of the audio and video improvements possible with Blue Ray.

Since the Oppo BD-83 seems to be good enough for Lexicon, I thought it should be good enough for me.

I was not disappointed.  The unit arrived superbly packed and presented.  The unit was in it own carrying case.  Cables were is a nice cardboard box.  A very high quality HDMI cable was included.

The instruction book is published on high grade paper.  English is excellent and idiomatic.  The instructions clear and informative.  In the play list, the illustration is a compilation of Bach preludes, which I thought added a touch of class.

Since I was not planning to use the analog circuits, I selected the standard version, not the SE.

I mounted the unit in my rack

Connections  were straight forward.  One two pin power plug, one Ethernet cable, and one HDMI cable.

Audio and video set up using their wizard could not have been simpler or more straight forward.

No problem was encountered watching high def audio and video program right away.  DVD performance was good also.  I have a had a couple of CDs the unit does not like and the other players will.  I don’t know what it is about CDs, but they seem more fussy than other digital disc mediums.  I know if you have a large collection you need more than one player and probably three!  I have a choice of four drives in the system!

The unit seems to make no appreciable heat.  There is a fan on the back, but I don’t think it has started.

This unit is phenomenal value for money and highly recommended.

The unit was purchased from the Audioholics store. The staff was professional and courteous throughout the transaction.

It was time to change my Rotel 1098 for something more up to date.  The Rotel unit, now four years old, had no HDMI facilities, and of course did not contain the new loss less codecs.  Also even after to going to a lot of trouble, it was impossible to make the unit totally impervious to RF interference from SCR light dimmers.  So on deciding to add Blue Ray, as there are increasing number of opera BD disc it was time for a change.

I decided on the Marantz AV8003, because it had the corps functions I wanted, especially a Neural 6 decoder, as MPR are now broadcasting the live Friday night Minnesota Orchestra broadcasts in 5-2-5 neural six.  Also the signal to noise ratio was excellent at 105 db.

I did do some measurements on the unit.

In pure direct mode, at 1 Volt output I measured the signal to noise at 106.2 db A unweighted.  I should stress this is at the limit or beyond of my older test gear.  However I think it shows that his unit is superior in the regard.

The unit has a clipping indicator for the analog inputs.  I had to use the 6 Volt out terminals of my Quad 44 preamp and crank it to get the indicator to light!

So I measured the head room.  This is a really important aspect of audio gear, and not enough attention paid to it.  The specs for the line inputs are 400 mv for I volt out at the unbalanced outputs and 2 volts out at the balanced outputs.

It took 15 volts in the clip the line in preamp and 14 volts out from the unbalanced connector before distortion was evidentb on the scope.  This is a very superior performance.

The order of the low pass LFE crossover is not stated.  The low pass crossover is fourth order.  I did not measure the high pass crossovers since I don’t use them.  My system requires the low pass crossover to be set to 60 Hz.  At 60 Hz the LFE output is 6 db down compared to a reference signal at 30 Hz.  At 120 Hz it is 30 db down.  I have not idea why manufacturers choose to hide such vital information from the prospective user.  That is irritating to say the least.

The unit is impervious to SCR noise, and is exceptionally quiet in use.

The unit is well constructed.  I did not remove the case, so as not to void the three year warranty.  However a large toroidal power transformer is visible.  The boards are stacked in logical fashion close to the inputs and outputs.  There appears to be no crowding, and I would think service would not be a nightmare.

Installation: -

I purchased the optional rack mounting brackets, which gave me one of those “what do I do now moments,” at the start of installation.

The standard practice for 19″ rack mounted equipment is to mount from the front.  The front mounting is 19″, but the space through which the equipment goes is 17.5″.  Now the main body of the case will fit the 17.5″ width.  However the case bells out at the front because of the fascia, and the brackets bell out as well, so it will not go all the way in.  So the unit has to be mounted from the back instead of the front.  Now the mounting brackets were slightly too wide to go into my rack from the back.  I think it would have gone if the rack had been fabricated of steel.  However because if humidity/rust issues I fabricated the racks from aluminum, which requires a greater thickness of metal.  So I had to take off exactly 3/32″ from each bracket with a JET band saw in my shop.

Fortunately the inside width of the mounting brackets when mounted is 17.5″, and the inside rack spacing of my racks is precisely 17.5″.  So I was able to make a cosmetically acceptable job of the installation.  As you can see, because of the need for rear mounting the inside metal edge of the rack is exposed, which it would not be with the usual front mounting.

Here is a frontal view of the mounting.

Set up: -

I took the opportunity to fully revise the some aspects of the installation as the LFE crossover is different.  I revised the active crossovers that send the the low pass output to the upper 10″ driver in the large bass lines, to improve the diffraction compensation to the 7″ drivers in the bass mid line.  The SEAS ecal drivers are a challenge to say the least.  I modified the crossovers to better compensate for the rising response of those drivers above 200 Hz.

The unbalanced LFE output goes to the lower 10″ driver.  I added an ATI L200 buffer amp, replacing my buffer amp to send the LFE signal to the upper 10″ driver also.  This requires a mono sum buffer amp, as the diffraction signal has to be stereo and the LFE is mono.  Without buffering the diffraction compensation would be mono.  The ATI L200 was connected to the balanced LFE output of the AV 8003.

Other connections were quick and straightforward, as I can get behind my equipment in the studio mechanical chase.

Doing Audio, speaker, input and video set up was quick and straight forward.

I should add that the instruction manual is poorly written, sufficiently poor that it would give the novice a lot of difficulty.  There is a lot of “Pigeon English” in the manual which is unacceptable in a unit of this quality and price.

Functionality is good.  You can can use digital and analog inputs of the same label.   If a digital signal is resented it will use that.  If an analog one is presented it will use that.  No need to go back to the menu.  That is a nice touch.

As far as recording, only an analog input selected is presented at the analog tape out.  So you can not record from the analog outs and listen and or watch something else.  That is inconvenient.  The Rotel had this covered.

I did a vet careful manual set up, before experimenting with Audyssey.  My review of Audyssey is a separate review.

The unit is easy to use.  There is a left control knob for changing inputs.  I use this the most, as you need to be at the equipment to switch units.  It is faster than using the remote.  The right knob is for volume.  The knobs are on plastic shafts and have a little wobble.  I think this was done to stop static on the fingers transmitting to the electronics and cause failure and damage.  With the Rotel, it would lock up if you touched a knob without discharging yourself first.  This unit does not require you discharge yourself.  The rack mounting by the way securely bonds the unit to the robust studio star cluster ground plane.  The power cord is two pin with no grounding prong.

There is a pull down panel to get to the other front panel controls.  The most frequently used front panel controls are the button to select the7.1 channel analog inputs, and the selector for direct and pure direct modes.  The Direct mode, by passes everything except volume, and the pure direct in addition switches off the video circuits.

Audio modes such as Dolby Plx stereo etc are best switched from the remote.  They can be changed quickly on the fly.

I have not got into file sharing yet, but I might.  I have no difficulty sending any audio file from a file my audio workstation via its RME Fireface 800, in SPDIF digital or analog.

Performance in use: -

So far the unit has performed flawlessly.  Both sound and video are beyond reproach.  In pure direct it is literally a wire with gain.

I did not have much expectation that the FM tuner would be of high caliber.  However I was wrong.  It is a first class FM tuner.  It is every bit the equal of my quad FM 4 which I hold in high regard, as do numerous others.  The unit also comes with the iBuquity HD radio system.  This unit did not endear me to that system any more than the little Sony unit I bought to evaluate that system.  An analog FM is significantly better in all aspects except dynamic range.

The only issue I have is this.   I have found is that it decodes SACD discs incorrectly from PCM via HDMI.  The rear channels in SACD should go to the center backs.  The Marantz sends them to the surrounds, which is not what should happen at all.  So I’m glad I kept my Marantz player in the rack, as I have to still use the external analog inputs for five channel SACD.

I have reviewed this recently and find that the speaker and monitoring arrangements for SACD in the US and Europe are different.  Since all my SACDS are from Europe, I have to use the 7.1 analog inputs for SACD playback.

The unit has a power draw of 60 watts and makes significant heat.  This further reinforces my view that complex processors like this should not be in the same case as power amplifiers.

So I have to say that I would recommend this unit who has need of a pre/pro for AV.

I purchased the unit from my local dealer Hi-Fi sound of Minneapolis.  I have had good relationship with them for over a quarter century.  They gave me a discount.  I purchased the unit with mounting brackets for a little over $2300.  I could not be more pleased.

Review of ATI Stereo line buffer amp

Pros : Compact, Versatile, Excellent Sound, Accurate Controls
Cons : Turn off thump a problem, Low output impedance
Best Uses : Blending buffer amp, Mono summing amp, Variable gain voltage amp

The ATI L200 is a useful device.

Its main uses will be to buffer blended signals.

To place a mono signal in two independent outputs.

For use as a positive or negative gain stereo or mono voltage amplifier.

The L200 has two xlr balanced inputs and two balanced outputs.

It can provide up to 28 db of gain down to zero output.

Input impedance is 40 Kohm and output impedance 40 ohms which presented a problem that I had to solve.

The unit comes with a 24 volt DC power supply. There is a 24 volt DC output that can power another unit.  Be careful if you do, the outside of the DC plug is hot!

I used my unit as part of my triamped dual aperiodically damped transmission line monitor speakers.  These are a novel design of mine and are truly full range.

However the LFE signal which is mono needs blending with the signal from the low pass active filters which are stereo.

So I took the balanced LFE out from my Marantz AV 8003 pre/pro, to the left balanced input of the L200.  I opened the unit up and moved the link to the mono sum position.  Then I could blend the LFE output with the low pass outputs of the active crossovers from the two L200 outputs

However the low 40 ohm Zs output impedance drastically dropped the output from the low pass crossovers.  So I had to modify the unit to increase the output impedance.

One other problem, when power is cut to the unit a large spike appears at input and output.  The unit sent my Marantz into reset.  So I have left the unit permanently on.  The unit contains no on/off switch.

All in all the unit is nicely made, has excellent signal to noise in all modes except maximal gain where it is noisy.  It would be better if it did not have a huge turn off thump, and had provision for a higher impedance output when used as a combining buffer amp.

However when all is said and done this is a useful unit, but for the price could be improved.

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. L1.  L2.  The value is 1.5 mh, but this is close enough to 1.6 mh.

C1 and C2.  Ce.

Rp1.  Rp2.  Req.

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.

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.