AE Lambda Midbass 10 Project?

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#81
Hi tinitus,

Here is the SPL graph for the Tang Band W8-1722 from the TB home site. There are some web reports that TB data is very optimistic, but it still seems useful to look at the 0, 30, 60 degree curves for this 8" for this discussion. The SPL looks like 87 db from the graph, but I don't know if this is "per watt" or at 2.83V. ...not high efficiency like Lambda target. This is a 4 ohm speaker. There is a diyAudio thread on these new TB underhung speakers and Zaph is starting measurements.
 

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#82
Re: Re: Re: system & market view . .

nickmckinney said:


I would like to see 93-95dB on this driver with a range from low bass to 2Khz as smooth and clean as possible. My personal desire is a simple 2 way with this driver that can play loud in a large room.
Click to expand...


Hi Nick,

I think your on to a good thing. I've been listening to 4435's and 4343's for a few years. Recently, I decided I really wanted a bookshelf speaker so I could have the speakers were I wanted them rather then on the wrong wall, and bought a pair of Audio Nirvana Super 10's.
I'm amazingly pleased with them. They are full range. They don't play 120dB, but you know, I never did that very long, and the super 10's get plenty loud, and they only have like 1mm of xmax, at ~95dB sens.
The thing they don't do, is have quite enough low end, and think what your talking about would work well. And oh, btw, I'm powering them from a UCD400 and haven't toasted them yet and don't expect I will.
Go make a decent 10, that you call a midrange, and I'll call it a great woofer for all most all people at home. Present company mostly excluded ;>)

btw, I'm only teased by these super 10's and I have two questions for you since I want the "breath" they have but more low end.
1) Have you ever pondered drilling a hole in your pole piece that can bolt on a CD? i.e. a coax woofer? (I know it might not be that easy!)
2) I'm jazzed about the specs on the TD15M as a woofer. I'm still wanting the bass and midrange of my long lost EV SP15A in a 8 cu ft, 35Hz cabnet. Is the TD15M the dream solution? Would you, could you bump the Q just a tiny bit?

Glad your back btw.

Mike Wurtz
 
#83
Hello,


I remember Mr. McKinney saying that his motors are having a 100mm central pole piece, with a 12mm gap. I hope I remember thid well. Is this pole piece straight or is it machined, with the termination (the length of the gap) being smaller in diameter than at the base? I ask because I don't understand how can you cover with copper a pole piece machined like that.

Mr. McKinney told that the copper layer is pretty significant so I guess it's not a chemical layer.

I hope I'm not asking for trade secrets here 🙂
 
#85
The lambda drivers use a 2" diameter coil. Since we are pulling the heat away with the copper, and in the apollo options the alum as well, the 2" VC can handle high amounts of power. The smaller coils also keep the inductance low. In the pic that Sheldon posted, you can see the non-TD T-yokes. These are the standard vented poles that go on the SBP drivers, PB drivers, and on our upcoming SL series drivers. They have a thick copper sleeve that is drawn out for us by a company in lower michigan. We turn every T-yoke down by hand to within .003", then by hand put on the copper with a special adhesive. We clean up the edges, polish the copper and they are ready to get sent off for plating.

We have looked into doing a coaxial version in the future. The issue currently is that we need to go larger on the VC diameter to do so. For a 1" throat driver we'd need to go with a 3" diameter VC to keep enough steel in the pole and be able to get the proper flare rate to mate up to the cone. I have some prototypes started, but need to get a small CNC lathe here in the future for experimenting on things like this.

John
 
#88
Thank you for your answer.

I was looking at you webpage, and noticed that you've taken in account two solutions for stabilising the flux in the gap.

1. Using higher permeable materials like Hiperco 27 (that's permadur, isn't it? There is an even finer material, Hiperco 50. That would be 50 iron, 50 cobalt-almost)

2. The faraday ring.

Did you had the chance to try permadur in your motor?
 
#90
I think this permadur stuff goes into the feastrex/lowther territory already. The prices, I mean.

I would like to thank you again for all this info, it's really of great value.

I would have another question. Using an electromagnet instead of ferrite, wouldn't decrease the need of copper sleeve on your pole piece? Do you estimate any effect on the eddy currents and flux stability? I mean, you'll already have about 2Kg of copper in your motor all around the pole piece!
 
#91
I looked into the Hiperco50(permendur) for the poles. It is VERY expensive. For 2" diameter bar stock it is around $230 per INCH! That means for the typical pole in the TD drivers we are at about $920 in raw material alone! It is also extremely difficult to machine and work with as it shatters and cracks easily.

For all practical purposes, the copper sleeve works well. Another option is to use powdered iron as it is magnetically permeable(although about 20% less than 1010steel) and non conductive electrically. Since we have more BL than needed in the higher diameter coil drivers, this can be a possible option as we get to those. The drawback is that you don't get the heatsinking ability with the powdered iron that you do with the copper sleeve.

John
 
#92
I looked into the Hiperco50(permendur) for the poles. It is VERY expensive. For 2" diameter bar stock it is around $230 per INCH! That means for the typical pole in the TD drivers we are at about $920 in raw material alone! It is also extremely difficult to machine and work with as it shatters and cracks easily.
Click to expand...

Crazy! And Feastrex is making monocoque motors entirely out of permadur. Of course, those units cost 7000 or so per piece.

For all practical purposes, the copper sleeve works well. Another option is to use powdered iron as it is magnetically permeable(although about 20% less than 1010steel) and non conductive electrically. Since we have more BL than needed in the higher diameter coil drivers, this can be a possible option as we get to those. The drawback is that you don't get the heatsinking ability with the powdered iron that you do with the copper sleeve.
Click to expand...

Just to understand. Moving magnetic field in the gap is an issue only when using conductive metals like steel as pole pieces? Or is it the fact that low content carbon materials like powdered iron, permadur have a better magnetic permeability? I guess any material used would benefit from the use of a copper sleeve, right?
 
#93
Am I getting close HERE ? 🙂

The yoke is 39mm or so, the VC would be 40mm. As you can see the yoke is larger at the base, and is copper plated. I can "cite" some of the sources for this design, but I couldn't test it yet with a FEM simulator. Don't have the time/knowledge.

The gap is 15 mm in length. This would qualify for an underhung design I guess. The yoke and the top plate ideally would be made of permadur. The rest is iron or soft steel. The outer iron rods are there for closing the magnetic circuit. The yellow ring would be the electromagnet. The cone is 12".

I drew these just for fun. I have to finish school first, get a home, and maybe then I'll try to build something 🙂. Until then, I'd rather purchase a TD midrange if I'll ever save some money 🙂 .


EDIT: The yellow thin bar that exists the yoke is a heatpipe, as in CPU coolers. This would take the heat around the voice coil even faster than copper, and disipate it through a copper/al phase plug. Haven't seen this ideea yet. Maybe I'll patent it 🙂. Heat pipes can be used, if properly positioned, to greatly dissipate the heat in a motor like this.
 
#97
Tang Band W8-1722

LineSource said:

Here is the SPL graph for the Tang Band W8-1722 from the TB home site. There are some web reports that TB data is very optimistic, but it still seems useful to look at the 0, 30, 60 degree curves for this 8" for this discussion. The SPL looks like 87 db from the graph, but I don't know if this is "per watt" or at 2.83V. ...not high efficiency like Lambda target. This is a 4 ohm speaker. There is a diyAudio thread on these new TB underhung speakers and Zaph is starting measurements.
Click to expand...

Hi linesource,

I can`t seem to find the data for Tang Band W8-1722, could you send me the link, please? Do you know who is selling them?

thanks
 
#98
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