i am sharing this, but expect that if you use it commercially, you will credit Stefano Bae, and myself, by name. it is original work, and already commercially available. it is patented in South Korea, that is, prior art. if you are a DIYer, have yourself a ball. failure to credit or attempts to pretend we never existed will result in open shaming by me and my many influential friends. this blog is also published within the creative commons, so some legal protection does exist as well.
at etf 2017 in Denmark, Frank Blöhbaum used his outrageous tubed 6th order subtractive crossover in the main system. it was a seamless and dead quiet match between the Volt RV3813s and the 200 Hz Iwata horns with Dietmar Hampel’s handmade compression drivers. wow! and the circuit is as elegant as the concept is sophisticated. okay, you might say… but what are “subtractive” filters? why? wtf!
at the other end of the spectrum, and as a way to introduce the idea, i have a passive subtractive crossover Silbatone exhibited for the Munich High End show at M.O.C. back in 2015 and 2016. there’s an image of the unit below. above is the general implementation. we use it specifically for the Western Electric Mirrorphonic system type “M2”, and to provide a subwoofer for speaker systems such as the WE-12A or the WE-16A or B, and the WE-15A. but you can use it in any system it fits. It has been the biggest improvement to the M2 we have heard. there are several methods we like. the one above… and we use a bridged T filter as well. the filter caps used in the crossover pictured are custom wound silver foil units… 900V @ 68uF. they’re really big, insanely expensive and very low ESR. you can just see one of them in the background, in the open chassis to the right of the finished crossover, below.
besides providing the dividing network, crossovers are immensely important so as to protect the drivers we use… in the case of original WE-555/Ws, sudden exposure to an amplified ground loop, or thump from a cable or turntable could exceed the 6 watt dissipation/Xmax pretty quickly. while some might question driving such a magnificent “full range” driver through a cap, the price of breaking a voice coil or diaphragm is so high, that component looks better and better with every year that goes by. some of the units we use regularly are 70 to 80 years old! restricting the amount of low frequency energy applied to the driver to above 60 – 120 Hz, is most easily accomplished with a dividing network, which also derives the signal for the sub bass.
the more durable WE-594 is typically crossed over at 300 Hz or higher… but anything that reduces exposure to mains frequency can’t hurt. not to mention, low frequency pulses from heavy metal or hiphop!
or is it? the crossover circuit itself probably looks a little peculiar for some of you? note that except for the specification “1 to 1”, any signal transformer will do, providing the levels are within spec… and it has at least 10H of primary impedance (Frank chimed in here and pointed out the response will rise up again at really low frequencies, without the critical inductance…. he is, correct! most line level transformers have no airgap, and often have something like 10H, but not all! an important point.). of course we have made an insane bridging tranny to do this job. but, given that the level needed to drive a 555 is at most 20 V peak (above that is destruction), any interstage or bridging transformer, capable of handling at least + 26dB, will work fine. doesn’t matter if it’s 600 ohms, 2K or 10K! 8 ohms will always be looking “up” into it. the Lundahl catalog has at least 8 different transformers that all work perfectly, for example. and if the level needs to be higher, you can always make it an electronic crossover instead, and at line level the number of transformers only multiplies. good symmetry will insure good performance.
but…? “wait a minute!” “what the hell is it?”. “why?” why is it connected across the cap? what advantage do you get out of this? such excellent questions.
the answer goes back to one Richard Small. the M.I.T. and Bell & Howell Small, as in “Thiel-Small”. in 1970, he wrote a not much publicized article concerning “constant voltage crossovers”, that paired with a presentation he made a year earlier in Sydney. a particular case of dividing network which are more commonly designed as “constant resistance, or constant power” networks (as in the way it’s shown in the radiotron, 4th ed.). his concern was focused on issues associated with the differences between the drivers used in multiple driver loudspeaker systems… especially driver position and amplitude, in relationship with the filters. but the precision with which Small worked is much appreciated by me. basically, Small laid out all the math and derivations for parallel and series first order crossovers, particularly in the case of “minimum phase shift”… his simple and straightforward style makes it relatively easy to understand, even for a dimwit such as myself. he even used two of the same drivers to illustrate precisely the relationship between them in their respective attenuation bands, which makes very clear the problems of integrating multiple drivers to behave as one.
he also derived the advantages series connected constant voltage networks have over the parallel connection, in both the thevenin and norton perspectives (voltage drive and current drive)… and the crescendo of the article was the introduction of an idea who’s time had not really arrived in 1969: the subtractive crossover. there was very little to dislike about the article.
i will not rehash the argument because you can read it yourself in the reference page of this website!
Small withdrew his support for the approach. and no one really looked at it closely again for many years. subtractive crossovers did become a real topic of discussion in the 80s and onwards… especially for high frequencies, and later for audio. the subtractive approach is used in digital code quite commonly. there are several analog approaches today, such as G.I.C. filters that are based on variations of subtraction, and are used everywhere. but it is not well known, that Small was probably the first to do it.
the technical solution Small presented employs difference amplifiers in shunt with low pass filter sections. it works equally well with high pass filters…
in fig. 13 of the reference article, you see a 4-way crossover. above i have arranged one block of his design used with a passive high pass filter driving an 8 Ohm load. that would be C1, above. 68uF for a 300 Hz f3 driving a resistive load. all you need is a differential amplifier to derive the precise inverse of the filter characteristic. so brilliantly simple. the sweep is shown below… green is the high pass, and blue is the output of the difference amp. this can be connected to a separate amplifier and the woofer driven directly. elegant.
the reasons behind Augspurger’s criticism has mainly to do with the industry! the way things were done… i think the extent of his argument is that speaker designers can’t be expected to equalize everything just to meet the requirements of constant voltage. a constant power approach is more flexible… all the trimming needed to correct the drivers ahead of the filter adds cost, and complexity. but, what Small was trying to accomplish was very simple: a multiway speaker that behaves like one driver. it actually takes very little for these systems to NOT behave like one driver.
if the experts were saying it didn’t matter, then it mustn’t matter. right? not so long after, you have the general consensus among the AES that absolute phase isn’t important in loudspeakers… who gives a shit about the time domain? and then the Linkwitz-Riley (ex Hewlett Packard guys) mishigosh (because now it doesn’t actually matter at all where the fuck you put the drivers…. it will NEVER sum in time). before you know it, 4th order LR is “high end” and i am generalizing brutally. and so much happened between 1970 – and 1990…
in any case, today DSP speaker processing is all about equalizing the drivers and flattening the level, BEFORE the crossover is applied… and then FIR to correct time domain issues inherent with steeper attenuation and the physical position of the drivers. some things just never change, do they? point given to Small!
however, the limitations to the constant voltage case, are severe, for symmetrical outputs. the hi and lo will always sum as a unity with the input because difference amplifiers reject whats common to the input, but as you see in the article, steeper slopes or additional phase shift on one side will cause marked changes in the sum and difference. this means that anything more than a first order will produce asymmetry in the output. this is manageable up to a point…
another wrinkle that can be used to advantage, is that any changes in loading will automatically be reflected in the difference… the crossover is self adjusting. this makes it easy to adjust, but also, if the driver’s impedance and amplitude aren’t flat, the response will vary as well.
above you see a “bridged T” RC filter tuned for roughly 50 Hz (actually closer to 60 Hz). imagine R1 and R2 is a dual ganged 10K linear ten turn pot. changing their value to 100 Ohms now changes the tuning frequency to 5 KHz. 1K each will become 500 Hz. etc. here you have an easily tuned electronic crossover, that can be easily accomplished with solid state or tubes… a unity gain difference amp and a buffer is all you need.
one of the most notoriously horrible crossovers in my book is (any) found in the Altec “Valencia” or “Model 19” family of loudspeakers… all the two way models descended from the Lansing “Iconic” (the mother of most modern two way speakers). yes. just remove the crossover and give it to your enemies. yes, it is my strong opinion that Altec burdened itself with a profound ignorance as to what a good crossover is, but you can remedy this yourself by simply discarding it into the nearest recycling pit, or simply by burning it. i have nothing more to say about the matter. it is so ironic that they could make such good quality drivers, and blow chunks with the crossover.
another huge mistake Altec made was the 511 and 811 cast aluminum horns. the exact type found in the above range of two way loudspeakers. it is an extreme effort to make these horns barely listenable… but dipped in tar and sand, packed in clay, covered with felt “dots” and bathed in C37 varnish… cut or ground away the dividers, glued “wookie hair” to the edge of the horns… etc. good fucking luck. you’ll need it. in any case, lets hypothesize that you have damped the thing into some kind of better behaved dread yeti lookin POS, and thrown away the crossover (incineration is good because it prevents it from falling into some other fool’s hands), now what?
this can help. now you have a much better sounding arrangement for the 811 horn, and you can directly connect an amplifier to the 414, 416, or whatever is inside your Altec box… i think the woofers and the compression drivers will need some additional tiny coils to tame breakup modes and ripple… but that is just normal house cleaning.
note that i have replaced the differential stage with a transformer. the crazy thing is, as hard as i have looked, i have yet to find anyone who has done this! well before the difference amplifier became widely used in laboratory work, or in consumer electronics, the humble transformer functioned in much the same way. think “Loftin-White”. in fact, the “bridging” transformer, which is usually wound with an extreme symmetry between all the windings, was used as a difference extraction device by the telephone company and in research up until the post WW2 era. the reason you haven’t seen a subtractive crossover done with a transformer is because no one has done it! well, there may have been someone out there someplace… especially at Bell? but it has never been published or used in the audio business… it might only be that it’s so simple, it just got passed over? or no one cared enough to try? no one found any value in it?
Stefano Bae, Björn Kolbrek and myself were talking about current drive and crossovers… and the inevitable conversation over series crossovers came up. and then Richard Small… boom! Stefano and i were drawing schematics for a week and a half. but the gem is really the absolute simplest implementation. which you will find at the beginning of this post. the simplest things are sometimes the hardest to see.
in any case, now you can use it too. if you need a steeper slope than is possible with this approach, a combination with additional filters is the obvious solution… and now, you need to go research Blöhbaum’s crossover!
enormous gratitude to Björn Kolbrek, for manifesting the the discussion which led to this “aha!” moment! without you it might have been another 50 years…?
State of Alaska > Department of Labor & Workforce Development > Employment And Training Services > Home
Provide labor exchange, employment and training services, and unemployment insurance to Alaskans and Alaska businesses, thereby advancing opportunities for employment and providing economic stability for communities in Alaska.
Operate the Alaska Labor Exchange system (ALEXsys), an online no-fee labor exchange system that connects job seekers with employers.
Operate job centers across the state to provide services to job seekers and employers and promote long-term employment for Alaska’s workforce.
Provide temporary unemployment insurance benefits to eligible unemployed workers while they are seeking employment.
Collect employment security tax contributions and maintain the integrity of the Unemployment Insurance Trust Fund from which benefits are paid.
Provide adult basic education services to adults who need a high school diploma or General Educational Development (GED) certificate.
Established in 1951, the Fishermen's Fund provides for the treatment and care of Alaska licensed commercial fishermen who have been injured while fishing on shore or off shore in Alaska.
Benefits from the Fund are financed from revenue received from each resident and nonresident commercial fisherman's license and permit fee.
The Commissioner of Labor and Workforce Development oversees administration of the program with the assistance of the Fishermen's Fund Advisory and Appeals Council.
The council is composed of the Commissioner or his designee, who serves as chairman, and five members appointed by the Governor.
Crewmembers with injury or illness directly connected to operations as a commercial fisherman must hold valid commercial fishing licenses or limited entry permits before the time of injury or illness to qualify for benefits. Note: Eligibility of a limited entry permit holder is based on the embossed date of the permit, not the date on which it was paid or when payment was received.
It is the fisherman's responsibility to see that a claim is filed. If the medical provider agrees to file a claim with your insurance company, the Fishermen's Fund, or a federal program such as Medicare, Veterans' Affairs, or the Indian Health Service, it remains the responsibility of the fisherman to see that the claim is complete and filed appropriately.
The fisherman and physician must each fully complete their respective report. These two reports need be completed only once, by the fisherman upon his initial treatment, and by the initial treating physician. All items must be answered and comments provided. (The reports are printed back to back. They are also available from most doctors, hospitals, clinics, and some harbormaster offices in Alaska, as well as from the Fishermen's Fund.)
Provide the geographic location where injury or illness occurred. Be specific, such as nearest landmark, miles or hours from a reference point. Give latitude and longitude if known (Box #16).
If you have health insurance or are covered by a public program such as Medicare, Veterans Administration (VA), Indian Health Service (IHS), etc., provide the name of your coverage provider (Box #21).
Describe in detail the injury or illness and how it was directly connected with commercial fishing (Boxes #17-19 and Boxes #22-25).
Submit the reports immediately to the Fishermen's Fund. The Fishermen's Report of Injury/Illness & Claim Form is considered the fisherman's application for Fund benefits.
Include a permanent mailing address and advise of address changes. Benefits may be denied if you do not receive and respond to an inquiry.
Questions 5-14 require very little time to complete, and a clerical assistant may answer most of them.
Questions 6 and 7 must be answered by the initial treating physician, to confirm that the injury is directly connected with the commercial fishing operations of the fisherman applicant.
Chart notes or medical records are required, as an attachment to the Physician's Report, but do not substitute for it. The physician may use the "see attached" notation for numbers 2 & 4 on the Physician's Report if the form is signed and the fishing-related questions are answered.
The Physician's Report serves many purposes, such as providing the necessary information in a logical order and concise manner to expedite processing and approvals for payment.
When bills are received for the treatment of an injury or illness for which an application has not been filed, the fisherman and all medical providers will be sent a letter informing them no action can be taken until an application has been filed.
The Fund is an emergency fund payer of last resort, which means that benefits are awarded only after full consideration of other coverage from private health or vessel insurance, and public programs, including Veterans' Affairs or Medicare. (Medicaid is an exception.)
A worker whose injury or illness is directly connected to a processing activity does not qualify for Fund benefits, but may be covered under Workers' Compensation.
A fisherman on a freezer or troller vessel who becomes injured or ill as a result of processing activities related to freezing the product would generally not be covered.
However, a fisherman injured or becoming ill on a tender vessel is usually covered unless the incident was directly connected to processing activities.
Pursuant to the March 4, 1985, Op. Att’y Gen., the Fishermen’s Fund is an emergency fund payor of last resort, with the exception of Medicaid. Benefits are awarded only after full consideration of other coverage from private health insurance, vessel insurance, and public programs, including Veteran’s Affairs or Medicare. The Fund is not a workers’ compensation program, commercial fisherman are exempt from the Alaska Workers’ Compensation Act under the authority of AS 23.30.230(a)(6).
If you have medical insurance, the Fund must have a written statementExplanation of Benefits (EOB)verifying you have filed a claim for each of your medical expenses with your health insurance carrier.
If the fisherman applicant does not indicate the P&I deductible on the application, a Report of Vessel or Site Insurance will be requested to verify whether P&I coverage exists, and if so, the amount of the deductible and the name of the vessel owner's insurance carrier or adjuster. If the deductible is unknown, benefits will be limited to $10,000.
The fisherman applicant should file a claim with the vessel owner's insurance carrier. These expenses are usually covered under the P&I policy. Expenses not covered should be submitted to the Fishermen's Fund. Otherwise, eligible expenses paid from the Fund which exceed the P&I deductible will be recovered by exercising subrogation rights under 8 AAC 55.035.
A vessel owner who pays for transportation or medical expenses for the injured or ill fisherman may be reimbursed if an agreement exists verifying that the employer advanced the money or paid any medical treatment on their behalf. A crewmember may be reimbursed if there is verification that the employer deducted the payments directly from wages due the injured or ill fisherman. Reimbursement cannot be made without the above supporting information.
Alternatively, the injured or ill fisherman and the vessel owner may complete the Vessel OwnerCrewmember Agreement, both signing to attest their understanding that the expenses paid by the owner were paid as a loan to the crewmember. The wording of the form may be revised to fit the circumstances. There is no assurance this agreement in any way complies with marine law. (Agreement in Appendix C)
A fisherman who is eligible to receive direct care services from an IHS facility is expected to utilize these services when possible. In the event that an IHS recipient chooses not to use an IHS facility when it is available, the fisherman must justify to the Council his/her reason for not using the IHS facility.
The Fund covers (pays for) services for IHS eligible individuals for items and services that are not covered by IHS; i.e., eyeglasses, chiropractic care, and dentures, if a legitimate claim is filed. However, direct care services that are covered by the IHS are not eligible for benefits from the Fund.
If an IHS facility makes a referral to another facility that is not an IHS facility, the Fishermen's Fund is responsible for the first $10,000. The Fund should be provided with a copy of the billing form to pay the claim.
When a direct care provider is not available, the Fishermen's Fund will pay emergency or urgent care at a non-IHS facility. Limitations on a fisherman's time are taken into consideration when determining "not available."
When the Fishermen's Fund administrator cannot immediately approve an application for benefits, it must go before the Fishermen's Fund Advisory and Appeals Council for review. The Council meets twice a year, usually in November and March.
4. Injury or illness unrelated or not directly connected to operations of a commercial fisherman in Alaska.
The Council may approve benefits when just cause is demonstrated for the delay in the following circumstances:
When a fisherman does not meet the timelines established above, and the Council has determined just cause for the delay exists, the Council may allow the administrator to approve benefits if:
A written statement is received from a physician or fisherman which: states the late treatment or surgery was necessary to correct injuries or illnesses such as a hernia, carpal tunnel, or musculoskeletal condition; and notes the injury was directly connected to the commercial fishing activity described in the fisherman's application; and states that any delay in treatment was for the purpose of allowing the physician or fisherman to observe whether remedial treatments or time would correct the condition.
A letter from the provider (i.e., hospital, medical clinic, etc.) or from an insurance company or public program noting the delay in filing or responding timely was their fault; or,
Verbal or written evidence from the fisherman applicant that the late filing or response was due to their medical condition, fishing responsibilities, or an emergency requiring the fisherman's attention.
When a decision indicates, "Your claim cannot be approved by the administrator," it does not mean the fisherman is denied benefits. Often further information is required to enable approval by the administrator, or by law the application requires approval by the Council.
In the event the administrator cannot approve an application, all parties will be notified in writing of the reason. The application will be reviewed and a final determination made at the next meeting of the Fishermen's Fund Advisory and Appeals Council. Parties will be notified of the time and place of the meeting and may submit written information supporting the application or may appear before the Council. A Notice of the Council's decision will be mailed to all parties, usually within four weeks. A decision may be reconsidered or appealed as noted below.
In some cases the Council will deny benefits unless certain conditions are satisfied by a certain time. The fisherman, therefore, must read the Council decision carefully and fulfill all the conditions to assure the best opportunity for approval.
Under Alaska Administrative Code 8 AAC 55.030(d), the fisherman has the right to appeal the decision of the Council to the Commissioner of Labor within 30 days after mailing of the notice of the council’s decision. The appeal must contain a complete statement of the justification including a description of the relief sought. The council’s decision is final unless appealed to the commissioner within 30 days.
An appeal must be in writing, signed by the claimant, and filed by mail or in person at the Office of the Commissioner, Department of Labor and Workforce Development, PO Box 111149 (1111 West 8th Street), Juneau, AK 99811.
The decision of the Commissioner is final and may be appealed under the Alaska Administrative Procedures Act (AS 44.62).
Related costs of transportation, medical care, hospitalization, prescriptions, therapy, and chiropractic care will be paid for an occupational injury or illness if it is "directly connected with operations as a commercial fisherman" in Alaska waters or on shore preparing or dismantling boats or gear used in commercial fishing.
Those costs noted above that are necessitated by a cardio-vascular disease may be paid if "attributable, directly or indirectly, to the fishing endeavor" (AS 23.35.080). A fisherman is also entitled to "such assistance after discharge from the hospital during period of convalescence as allowed in consideration of the condition of the Fund" (AS 23.35.090).
Covered Injuries or Illnesses. Occupational illnesses or diseases which may be covered include: hernias, varicose veins of the leg; rheumatism, arthritis, musculoskeletal ailments such as bursitis, traumatic sciatica and tenosynovitis; the respiratory diseases bronchitis, pneumonia, and pleurisy caused by or aggravated by the fishing endeavor.
With respect to a pre-existing injury, if subsequent aggravation is attributable strictly to that injury, and does not amount to a new injury, then, as with a recurring disability, benefits will not be awarded (AS 23.35.130 and AS 23.35.140, Opinion of Attorney General).
Noncovered Illnesses and Diseases and Other Conditions. Illnesses or diseases and other conditions not covered include strep throat, tonsillitis, the common cold, influenza, ulcers, cancer, appendicitis, insect bites, salmonella, giardia, smoking related conditions, cracked teeth or loose fillings from eating. Sexually transmitted diseases or drug or alcohol related injuries, and those caused by not following good hygiene and health practices, or improper care are not covered. Ear infections caused from diving in a commercial fishery are covered but not when due to a cold.
Chronic Conditions. Chronic injuries, although aggravated by the fishing endeavor, may not be covered since they are usually pre-existing and not directly connected to the operations of a fisherman.
Three-Month Gap in Treatment. The Council must reassess the treatment of an injury or illness when there is a three-month gap in the treatment. A doctor's statement is required noting how the treatment was directly connected to the prior commercial fishing injury.
Dental and Eye. Dentures, glasses or contact lenses lost or broken may be replaced or repaired only when lost or broken in activities directly connected to operations as a fisherman. A claim for dental injury without other bodily damage must be supported by a doctor's report that substantiates the injury's direct connection to operations as a fisherman, or an affidavit may be required.
Away from the Boat. An injury or illness occurring away from the boat or fishing site will be covered as long as it is directly connected to operations as a fisherman, such as injuries incurred on a dock while hauling gear to the boat or at home repairing commercial fishing gear.
Transportation. Costs are covered to and from the vessel, fishing or gear repair or storage site to the nearest medical facility where appropriate emergency care can be provided. Additional transportation costs to receive specialized or skilled care unavailable at the nearest approved medical facility must be supported by a written statement from the attending physician which clearly defines the specialized medical skill required and the nearest place where it is available. Approval of additional transportation costs may require consideration of the financial condition of the Fund.
Costs incurred for transportation after discharge from the hospital during period of convalescence may be approved to return the fisherman to the boat, home or another place that reasonably meets with the fisherman's convenience. (AS 23.35.090-100, 8 AAC 55.010(e) and AS 23.35.080 & 100.)
If the injury/illness occurred while the fisherman was intoxicated or under the influence of non-prescribed drugs (8 AAC 55.010(c)(3).).
Fishermen’s Fund may reimburse 50 percent of the vessel owner’s deductible, up to a maximum of $5,000. Vessel owner must submit required documentation to the Fishermen’s Fund to receive reimbursement.
Benefits will be paid only to the medical provider or to the fisherman  to the provider if the bill is outstanding, or to the fisherman if his payment is verified by evidence such as cancelled checks, receipts, or bills or statements from medical providers.
A vessel owner who pays a bill can be reimbursed if the Fishermen's Fund administrator receives evidence in writing that there was a prior agreement that the vessel owner would pay any medical expenses, or would advance payment with an agreement to be reimbursed. The fisherman will be reimbursed instead of the vessel owner if the fisherman submits evidence that the vessel owner deducted these expenses from the fisherman's compensation. However, these reimbursements do not imply that such an agreement or understanding is in compliance with marine law.
Except for compelling reasons, benefits for the care of any one person involving a single injury or disability will not be paid beyond one year from the date of initial allowance, and cannot exceed $10,000. To request an extension of benefits or an extension of duration of care, the fisherman must submit a separate written letter justifying the request and a completed Compelling Reasons Questionnaire (Form 07-6124).
The written letter must note the "amount of relief" or additional benefits needed, or the "extent of additional time" required. The compelling reasons justifying the request must be specific. The Council must approve all requests.
Compelling reasons to exceed $10,000 are not defined in law but must be sufficient to justify the requested benefit or time extension and must include:
Impact of injury or illness on the fisherman's ability to earn a living while undergoing required treatment and to continue to earn a living commercial fishing.
Any other compelling factors that affect the fisherman's ability to pay for related expenses in excess of $10,000, or that result in conditions that require follow-up treatment beyond one year.
How much additional relief or money is needed in excess of what the fisherman can pay and/or the amount of extended time wanted beyond one year.
Ideal for paellas, salads, as an accompaniment to meat or fish, and for making delicious rice-based deserts.
Extra Montsià, with its incomparable flavour and quality, is the rice of choice of prestigious chefs and the one most used by professionals in this sector.
The same Montsianell variety of rice selected is always used, so it has the same cooking time and a great capacity to absorb tastes and flavours.