The Othorn tapped horn

What is the relation between density and flux?
That higher mass often means metals with higher density. If the process in alloy making is also concentrated in improving the density (the mass will raise with it) the electrical and thermal capabilities are enhanced also.
The relation between mass and flux rings, the higher the mass the more effective the flux rings become down low (in frequency). Often the 'ideal' mass is way to high for practical reasons of transportability and costs. That's why a few Italian loudspeaker manufacturers have done research to improve the effectiveness of the rings. The results from that research ended in balancing the suspension in areas where the flux rings aren't so effective. All in favour of better linear movement of the cone.
 
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The idea for searching for alloys is to mix or change the characteristics from their pure element form. These alloys, or 'new' metals, can combine the higher strength capabilities and lower weight from magnesium and titanium plus the better electrical values from aluminium, silver and sometimes gold.

For flux demodulating in loudspeaker, magnesium is no go since it can influence the magnetic field generated by the magnet and the voice coil. Titanium is usable but only in alloy form to keep all positive aspects of the pure element; strength, low weight, lowest heat/expansion factor and improve the electrical capabilities by alloying with aluminium and silver. It is not as effective as pure copper for flux rings but it has better characteristics for the voice coil former or any other use where weight (moveable parts) is an important factor. Of course from an economic point of view the use of titanium alloys is not very realistic (yet). If in future the demand is for LF drivers with even high power capabilities the titanium alloys can become economically justifiable. If the electrical capabilities are the main factor the best cost/performance ratio will be found in (pure) copper.

Not many loudspeaker manufacturers have research capabilities in this area simple because it’s not their core business. However, in Italy a few loudspeaker manufacturers work close with other industries. For instance 18Sound is part of the AEB technologies Group that finds its origin in car/motor parts and production lines. Both areas are involved in the research of ‘new’ metals. Any PA manufacturer that claims their flux rings are made out of aluminium and do work significantly below 150Hz have not published their findings trough AES or any other recognised institute as far as I know. Besides copper and some 'new' metal alloys (that can include aluminium) there is to my knowledge not any other metal that has achieved measurable improvement in the lowest octaves in the sub range. Some manufacturers claim stainless steel can be used as voice coil former and get measurable results in lower THD figures for the sub range. I can’t confirm those findings but I have no reason so far to doubt their findings.

As far as the traditional idea of the relation between flux rings and mass/density for low frequency PA use, it is commonly accepted that the more mass is added or the higher density of the metals the more effective they become in the lower regions of the frequency band. Some alloys can improve the density, electrical and thermal capabilities (or just one of them) but I haven’t seen any better result yet than flux rings made out of pure copper. Like you said pure copper has already a high density besides good thermal and electrical capabilities but the price of pure copper is still rising on the global market.
 
stainless steel is a bad conductor for both heat and electricity. A material datasheet would be rather enlightening, I think. Titanium is an even worse heat conductor.
In case of a metal voice coil formers like stainless steel, it still has significant influence on the heat dissipation of the VC. Although it doesn’t work in a 'fast' responding way compared to pure copper or aluminium, the heat dissipation is considerably higher than just using the traditional Kapton formers.

Fast reaction times for heat dissipation are less important to drivers (with the exception of ribbon drivers). The VC will be constantly heated by the LF signal. Power compression in LF drivers is achieved over relative long period of times, minutes instead of seconds. Even metals with low heat conductive capabilities still perform way better then the traditional Kapton formers.
The wires of the VC can reach extreme temperatures which are why manufacturers prefer to use a Kapton film between the VC and the metal former. Besides an electrical insulator, Kapton is also a thermal insulator. If the film is thin enough and the VC is tightly wired on the former there is still a significant increase in heat dissipation from the VC to metal former part. It works on the same principle of how Mica or Kapton are used to separate electronic part electrically from their heatsinks.

If you compare aluminium and titanium you will find aluminium has 10 times faster heat conductive capabilities in those datasheets. But if we look to HF compression drivers you don’t see 10 times faster burn outs from titanium membrane drivers. The reason is again the reaction time of the materials in relation to their thickness. The thickness of the HF membranes is so thin that reaction times are no longer an issue.
The whole concept of heat absorbing figures of metals in relation to loudspeakers should be seen in relation to responding times and the thickness of the materials. We are not talking centimetres here but materials thinner as 1mm. If that wasn’t the case try to find a less than 1mm thick stainless steel sheet and put it on your BBQ and see for yourself how 'bad' of an conductor it will be.

Therefore stainless steel or titanium in loudspeakers can have a significant contribution to heat dissipation.
 
I haven't had a chance to check here much in the last couple of days. We have gotten off on quite a tangent I see. :D

Great stuff Djim. The comment about judging the materials as they apply to loudspeaker or bass driver design in particular is spot on IMO. These materials will often be very lightweight or thin as utilized in these applications so the conduction properties are better viewed under that context.
 
Thanks Josh, but after rereading my own posts I understand 454Casull’s points about a few strange looking phrases in my posts.

Besides the stainless steel former, I'm curious about how the TC's will hold in real PA circumstances over a longer period of time. I don't have good experiences with full alu cones but I also haven't worked with TC's.
 
There is a little confusion here. The aluminum cone TC's and the Gjallerhorn are not intended for what would be considered typical PA work. IOW run on very high average power for very long durations, moved constantly, content heavily concentrated on 40-100hz with not a lot below there. Those are for my own personal use and as best I can describe would be more intended for a commercial cinema or IMAX type or duty. High output required with an octave lower extension than typical PA. Capable of producing very high levels and absorbing lots of power but in much briefer, more varied signal types and random durations more typical of an action movie than the higher concentrated and longer duration signals of typical PA work. Not saying they would fail under that use but that was never the intention for them.

This thread is about the PA bin but it uses a B&C 21sw152, or other pro type driver. TC does make the pro5100 which should work in here but it is a Rohacell cone not aluminum. Somehow we got to talking about the LMS Ultra driver used in the Gjallerhorn.
 
Josh,

Although I agree with most all you have said, my most early “expensive mistakes” were back in the days when aluminum (rather than titanium) HF diaphragms were used in the JBL line.

The aluminum diaphragms would develop stress cracks from fatigue over time, in my two years time with Eclipse Concert Systems, I became very adept at changing (and aligning) aluminum four inch 2440 and early 2441 diaphragms.

The aluminum diaphragms would all fail over time, time depending on excursion. There are plenty of 50+ year old aluminum diaphragms still working in low excursion home use, but none in high excursion PA use.

When the titanium diaphragms were introduced (JBL 2425, 2445) we started to use them at STS, and had no failures due to cracking from 1982 through 1992.

I had about twenty 1.75” 2420 aluminum diaphragm drivers which failed from cracking, all failed over several years, but when replaced with the titanium 2425 diaphragms, never failed (other than coil burnout) again.

In fact, JBL wrote in the 2425 spec sheet:

“This titanium diamond structure combines the ruggedness of phenolic and composite type diaphragms with the outstanding frequency response of the fragile aluminum and exotic metal diaphragms. Nontoxic titanium has no fatigue limit, It can last forever if not overdriven.”

It would be interesting to look at the LMS ultra cone under a strobe with a sine wave playing and see if the movement is purely pistonic, or if it does flex some.

Although your short term tests show the aluminum LMS ultra cone has held up fine, I hope they fare well over the long haul.


Art


1.75" vs. a 16.5" cone...

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I'll put it this way, the VMP cone is 40 mil and you'll break (or severely hurt) your knuckles before you dent it with your fist.
 
How well do you think that SSA Zcon 18 D2 would really perform (looks great in Hornresp)? That, the Faital 18XL1500 and the B&C 21SW152-4 (least expensive to most expensive) are my top pics for this enclosure, so far. Seems it would be 1 sub per 20A circuit, for clubs/buildings only having this option.
 
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How well do you think that SSA Zcon 18 D2 would really perform (looks great in Hornresp)? That, the Faital 18XL1500 and the B&C 21SW152-4 (least expensive to most expensive) are my top pics for this enclosure, so far. Seems it would be 1 sub per 20A circuit, for clubs/buildings only having this option.
Just a thought but 468,99$ for a woofer with a foam surround?! Not sure that is a 'good' investment in the long run, especially when used for clubbin'...
 
How well do you think that SSA Zcon 18 D2 would really perform (looks great in Hornresp)? That, the Faital 18XL1500 and the B&C 21SW152-4 (least expensive to most expensive) are my top pics for this enclosure, so far. Seems it would be 1 sub per 20A circuit, for clubs/buildings only having this option.

No idea how that Zcon would do. They are made to take a serious beating for car audio competitions though. I wouldn't worry about reliability myself with club use. This assumes that it actually performs as advertised. I have no idea on that account. Inductance is a question mark too.

You don't have to drive the cabs into oblivion constantly. If you arent giving them that last 3db of power they will just be that much cleaner and free from being overdriven.I figure a Xti6000, Crest cc5500, Rmx5050, ma5050, ca18, ma5002vz, should all happily drive a cab on each channel just fine. Or you can move up to the pl380, itech, Lab gruppen class of amps and run 2 or 4 off of one.

The cabs are in process at the shop building them.
 
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