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Old 12th December 2004, 06:59 AM   #1
morbo is offline morbo  Canada
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Default Two new widerange drivers at madisound

Check them out:

http://www.madisound.com/new.html

The Aura looks interesting to me, similar specs and price to the TB871... could it unseat the 871 as budget WR favourite?
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Old 13th December 2004, 09:21 PM   #2
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"NS3-194-8E $10.50"

Looks very similar to the TB drivers (cone, surround, and phase plug). The specs are also close to the 871 or 926.The price is good as well, better than TB.

Could be a great driver.


edit: looks like you said the same stuff in another post
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Old 20th December 2004, 09:44 PM   #3
MarkMcK is offline MarkMcK  United States
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I accepted a commission to test the NS3-194-8E driver (and possibly even modify it). For the money offered, I would not normally accept such a commission, but a story was told about a bet in the balance as to whether the NS3-194-8E would "shriek" or not. If the patron who underwrote the acquisition of the drivers wishes to be known I will allow them to identify themselves in the thread.

Anyway, the testing on three unit driver sample is completed. The test results will be attached to this post.

First, about the driver. I do not know if the driver is made by Tang Band or not. Most Asian loudspeaker companies are not vertically integrated. They follow an outsorcing business model. As a result, you can sometimes see identical parts in offerings from different companies. In the case of this Aura driver I have seen every part in a Tang Band driver except for the neodymium magnet assembly. This is the part that is new to the driver. It is also a part not designed for this driver. While it is of the "U-iron" magnet design, it features a vented pole piece. A vented pole piece serves no purpose in a driver with a phase plug. The phase plug blocks the pole piece vent as effectively as a solid pole piece.

Since the "U-iron" magnet design features the magnet as part of the pole piece, venting will reduce magnet mass. This is only a small reduction in magnet strength, but it is still a small reduction. Either the magnet will have to be in some other dimension larger, of a stronger neodymium mix or, the motor is going to be slightly less powerful. This may be important for how the driver performs in comparison to other neodymium "U-iron" magnet designs.

Beyond the vented pole piece, this design has a larger and more massive "U-iron" assembly. The magnet is larger and slightly heavier than the familiar "U-iron" design.

I will let the first set of graphs documenting the stock performance of the N3 driver speak for themselves.

I have also worked out a modification for the driver and will post modification details in addition posts in this thread.

Good designing and good building,

Mark
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Old 20th December 2004, 11:50 PM   #4
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Thanks Mark for that info.

The stock performance is not that great, right?

But maybe alright after your modifications
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Old 20th December 2004, 11:52 PM   #5
morbo is offline morbo  Canada
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Thank you very much Mark for posting your thoughts and measurements. I have to say it does not look that encouraging. I look forward to seeing what you are able to make of them with some tinkering!
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Old 21st December 2004, 07:20 PM   #6
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Mark,
just for aestetical reason, the gem tak ring can be done in the back side of the cone?
This can be complicated compared with your suggestion but there is any teorical reason that makes any difference about the side of the cone where the rings are performed?
Jorge
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Old 21st December 2004, 08:11 PM   #7
MarkMcK is offline MarkMcK  United States
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Jorge,

The glue ring modifications are for polypropylene cone drivers. Glue rings will not work on paper or metal. The heart of the modification for this paper cone is a ring, but not made of glue.

For the polypropylene cones, the glue rings may be applied to either side of the cone. Underside is just much harder to do.

Mark
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Old 21st December 2004, 08:38 PM   #8
MarkMcK is offline MarkMcK  United States
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The modification for this driver consists of a combination of passive electrical prefiltering and one mechanical modification to the cone. The combination of the two will bring the performance to barely within plus or minus 3-db. There is also some degree of variability in the modified drivers.

The attached graphs show the improved transient response of the modified driver and the range of variability in the modified drivers.

This posting is about the mechanical modification to the cone. The cone suffers from a number of vibration modes, but the two worse ones are tightly coupled and the trigger points for them are in close proximity on the cone. One cone treatment will impact both targeted vibration modes.

As I have stated several times before, paper is hard to work with and hard to fabricate mechanical corrections that are effective. The selection of the following technique is based upon the possibility of the average diyer implementing it successfully and easy availability of the part.

The part is a square rubber drive belt. The belt has an inside diameter of 10.2 centimeters (does not have to be exact but should be close) and is 1.19 mm in cross section. You attach the belt to the cone using a high tack, spray on adhesive. Spray the belt, and then apply the belt to the cone. Try to adhere the belt as a concentric circle between the inside edge of the surround and the voice coil former.

It is important to use a square belt of this cross section. A square belt will not sit flat on the inside of a cone. Any mechanical vibration mode is a second order oscillator. If you want to change the characteristics of a second order oscillator you change either the mass or the spring rate or both. Both glue line and belt application modifications change both the mass and spring rate of an isolated vibration mode within the larger cone structure.

In this modification we are changing the mass and the spring rate. We are changing the spring rate in two ways. First, we change the spring rate by laminating another material with a different mechanical impedance. In addition, we are tensioning the cone across the diameter of the belt. We do this by torquing the belt with one face flat against the cone and holding it under tension with the adhesive.

To achieve the results shown in the attached graphs, you have to torque the belt and tension this small area of the paper cone.

These small driver belts are used in a variety of consumer equipment and should be available worldwide. The high tack spray on adhesive is commonly used in automobiles. It should be available in any car supply store.

The remainder of the modification consists of a seven component prefilter network. I will describe that network in the next posting. This network does much the same thing as Pass is doing with his current source amplifiers. It is adjusting the frequency dependent voltage potential at the voice coil. It is just that you do not need the current source amplifier.

Good designing and good building,

Mark
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Old 22nd December 2004, 10:26 PM   #9
MarkMcK is offline MarkMcK  United States
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This is the last post in the modification series. The attachment to this post includes the schematic of the prefilter. It also includes a graph showing the comparision at various points in the modification sequence and an extended version of the lower frequency response.

First, the comparison graphs. This goes back to a long term concern of mine about sensitivity ratings for drivers with large variences in frequency response. With the driver's output varying by 12 or more db over it stated bandwidth, what does a single number sensitivity rating mean.

In the case of this driver, there were indications that its natural sensitivity was somewhere near the bottom of the 4 kHz dip (see first attached graphs). In addition, all the prefiltering has taken off an additional 2 to 3 db of sensitivity.

This graph also shows the impact of the belt application and prefilter parts of the modification. The spectrum drawn in green shows the response with just the prefilter. The spectrum drawn in blue shows the response of the prefilter and with the rubber belt modification applied.

The second graph is an extended resolution graph of just the lowest two KHz of response. There is a general belief that log graphs have greater resolution in the lowest octaves. While a log format does spread the low frequency data out and compress the higher frequency data, there is actually no increase in resolution. In the case of this graph I lower the A/D sampling rate in addition to spreading out the graph. There is a little over 10 times as much resolution in this two kHz slice than in the 0 to 25 kHz graph. There is, however, no more to see. The lower limit is still 140 Hz (no valid data below this frequency) and there is nothing more revealed than can be seen in the 0-25 kHz graph.

Last, is the prefilter schematic. I suggest using air core inductors and polypropylene capacitors. Super quality of either, however, will only produce very subtle improvements in sound.

In sum, even with the modification, this driver is not as good a performer as the modified TB W3-881S. It is, however, a huge improvement over the stock version.

Good designing and good building,

Mark
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