Zero Ohms DCR Woofer Inductor??

[LowOhms]

Hi All !!

A "zero Ohms" Inductor, is of course, no inductor at all.

I want to probe others on how one can passively and benignly roll off the high frequencies in a A7-800 VOTT .

Mine is loaded with 515Bs and 802Ds on Emilar EH500-2 horns, run by a single flea-powered Type 45 SE amplifier, in a small ( 12.5 by 14.5 foot ) living room. This KISS crossover assumes use of a minimal first-order passive crossover, maybe at 1-1.25 KHz, but minus any inductor on the 515B.

WHO has tried this, as follows, to eliminate the inductor ??? :

A soft high-frequency-absorbing circular obstruction, in the MOUTH of the A7 bass horn, suspended by four criss-crossed strings or wires, on the same plane as the front of the A7 enclosure, and centrally located in the A7 bass horn's mouth ( not throat !! ) ??

The " high-frequency-absorbing circular obstruction " could be made of a very open stable circular metal mesh grill or fencing ( maybe with 1/2 inch grids ), and a 1/2 inch thick circular piece of white fluffy material, as used in quilting, padding, etc. sewed on each side, with the obstruction held in place - centered in the A7 bass horn, by strings or wire at 90 degree intervals.

One could experiment with :

a) different diameters of this added obstruction, and

b) different amounts of fluffy material thicknesses,

to acoustically roll-off the high frequencies, in lieu of what a single inductor would typically roll off.

If one can ELIMINATE the power-robbing inductor, we obtain superior coupling of the audio amplifier to the 515B, and, we beneficially have less efficiency difference between the woofer and the 802 compression driver.

Who has already tried this in ALTEC - A7 land?? What did it sound like? What useful comments would anyone be able to make??

Thanks in advance.

LowOhms, Jeff Medwin

[tomt]

would this amp happen to have 4 channels ?

[LowOhms]

would this amp happen to have 4 channels ?

No, its my own 2015-constructed simple 2 channel SET amp. 'Just half a 12AX7, Directly Coupled into a Type 45 DHT.



Attachment 2757 Attachment 2758 Attachment 2759




I am NOT interested in biamping to eliminate speaker level inductor Tom.


Key idea of this post is to explore with others the use of a high frequency obstruction, centered in the mouth of the bass horn on an A7, to eliminate the inductor on the A7 woofer.

[GM]

Not aware of anyone doing it beyond stretching dense grill-cloth over it. FWIW, the range of frequencies you're interested in has already been researched by Dr. Geddes for his HF WG where he found fish tank filter material? [30 ppi open cell foam IIRC] 'plugs' worked well when it was completely filled, so considering how much bigger the A7's horn, it theoretically will hold enough to roll off down to a lower F6: Abbey

GM

[mah]

Zero Ohms DCR inductor:

Zero Ohm N390



Zero Ohms reactance = no inductance.


Quality Output Transformers that roll-off early can be used.


Mechanical filtering over a range of frequencies can be problematic.


Tailored HiFi hearing aids are an option.

[LowOhms]

Hello mah,

Those N390 inductors are neat, but I am trying to eliminate the inductor completely. The N390 line, made by Mundorf, may be marketing wise termed "zero DCR " but it should be " near-zero DCR " as the wire has some resistance.

Also, I object to spending hundreds of dollars on a high end inductor, when NO inductor will possibly sound better, and may outperform a N390 added inductor....and at close to a zero cost.

You state " mechanical filtering over a range of frequencies can be problematic."

I agree, but lets solve the problem and APPLY a new solution.

I have been told of ONE person .... who has tried what I suggested. Tried to reach him last week, but very sadly, the fellow died last Sunday. R.I.P.


Here that follows is the description I received, and I am INTERESTED in trying this on my 515Bs in my A7 825 enclosures : ( own 802Ds with GPA new 16 Ohm ALTEC diaphragms, re-magged, and Emilar HB500-2 horns, which I expect to cross over between 800 to 1250 HZ when all is adjusted and set up, first order. Here we go :


The person who heard the audio system, and technique applied to A7 woofers, wrote to me this week, to relay what he recalled :


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Randy had the most highly-modified (and best sounding) A7 based system that I've ever heard. He combined the A7 woofers (loaded with vintage alnico Altec 416s), with the Yamaha horn/compression driver; [which he thought was the best nearfield (meaning used in a reasonably-sized room) high freq horn]. He then passively rolled in a JBL 2405 slot tweeter around 12-13k.


Randy used a standard 2nd order (approx) 600 Hz crossover on the Yamahas, but ran the 416s full-range, relying purely on physical techniques to limit high freq output...this was accomplished by suspending a piece of Styrofoam in front of the woofer. A vertical wire was attached at the front of the woofer cabinet, and this wire went through the Styrofoam, holding it firmly in place. The Styrofoam was a round puck about 2 inches thick, and maybe 5 to 6 inches in diameter - Randy glued a piece of sound-absorbing material to the back of the puck (facing the woofer), but I do not know what sort of material he used...knowing Randy, it was probably just a cotton washrag :-)


BTW: There was nothing stock about his 2nd order crossover: I recall a half dozen high zoot caps wired in parallel. Inductor was a ribbon air-core.


System sounded extremely well-integrated. Randy used a mono subwoofer that [I'm guessing] was crossed over around 40-50 Hz.

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Who besides my friend in Atlanta who described the above, has heard this system or, has DIY experimented with acoustic woofer roll-off of an ALTEC woofer's highs??

LowOhms, Jeff Medwin