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john65b 3rd March 2012 01:56 AM

Tympani Voice coil Rewire Advice
 
OK, sold my Tympani IVa and sorely miss the deep solid bass I had with this speakers. The best bass I have heard yet..


Now I have a set of trashed Tympani I-D (cheap) that I have got the bass panels temporarily working by reconnecting the voice coil wires - pulling up the remaining voice coil wire, sanding off the coating, and twisting the ends together, then gluing them back to the mylar...again a temp fix. It doesn't quite compare to the deep bass of the T-IVa panels...

I believe the Tympani bass panels (actually, the two bass panels on one channel are not identical - one was a true bass panel and the other was a mid bass panel with resonant buttons) were two 8 ohm panels run in parallel to get 4 ohms, and also to increase the bass SPL to match the SPL of the mid/HF drivers (methinks).

I had originally planned on rewiring the entire T-ID speaker (both bass panels and the tweeter) but have since decided to use the two "true'" bass panels (one for each channel) with my CLS. I currently have them set up and working, but the wires are so corroded on one driver that I have repaired it about five times already. So I have decided to dive in and rewire these two bass panels...

Since I plan is to biamp the Tympani ID bass panel with a Behringer DCX2496 and dial in the desired crossover frequency (around 200-250hz) and adjust gain on low frequency panel amp to match the SPL of the CLS, I want to, again, use just one (true bass) panel each side.

So question is, what gauge wire should I use? The original Tympani ID was 24g, but I have some bass wire from a 2.6 rewire that is noticeably thicker (22 or 23 gauge?) and less resistance per foot han the 24 gauge.....

If I am targeting 4 - 5 ohms and use 24gauge wire, I should be able to just not double up the six rows on the center of the panel to get around 4 - 5 ohms.

Or I can use the thicker wire and wire up the panel in the current configuration (doubling up the mid six rows) and get the 4 - 5 ohms.

The idea is to get as close as possible to the T-IVa bass performance...

Advice?

Anyone know what the T-IVa bass wire gauge is?

RogerGustavsson 4th March 2012 08:15 AM

Hi,
The Tympani I-D have 25 gauge wiring, like the IV and IVa. That is 8 Ohm for each bass driver. It is also half the mass of the MG 3-series. Do you intend to use the Mylar as it is? Sure after 30 years some ageing must have appered? If you alter the mass of the wiring, the low frequency resonance behaviour will change. Thicker wiring will lower the tuning and increase the resonant peak and therefore increasing the risk of the diaphragm hitting the magnets. What are the tuning frequencies of the I-D? Can you read the numbers on the frame of the drivers? Can you give me information on the curvature of the I-D bass drivers? I would use both bass drivers of the Tympani I-D in combination with the CLS. Only one driver is not enough for good bass.

A complete rebuild at Magnepan is not very expensive and it would save you a lot of work! Think they will last for many years to.

The basses of the Tympani IV and IVa are different from the I-D. The low bass drivers are wider and they have different tuning. It seems that I-D, IV and IVa, all have the wire but the rest is different. The IVa are said to have stronger magnets.

Roger

john65b 4th March 2012 07:11 PM

Roger, Thanks for the reply...

Quote:

The Tympani I-D have 25 gauge wiring, like the IV and IVa.
So they all have same wire guage? I did not know that...

Quote:

What are the tuning frequencies of the I-D? Can you read the numbers on the frame of the drivers?
The writing on the T-1D are as follows:

RC-043863
46 55 (the 55 has line thru it)

LC-043863
46 58 (the 58 has line thru it)

Quote:

Can you give me information on the curvature of the I-D bass drivers?
I do not understand this...curvature?

The mylar on these T-1D seem to be in good condition.

Now again, the two pairs of bass panels are different on this T-1D. Since the design is a two way crossed at around 1000hz (I think), one of the pairs of bass panels have the two tuning buttons (I would think these were the panels needing to reach 1000hz). If I do not intend to go any higher than 250hz, why use all four panels? I am biamping so the 8 ohms is ok, and I can dial in the required amp gain to get the required SPL out of the driver to match the CLS SPL.

Am I thinking of this all wrong?

RogerGustavsson 5th March 2012 07:01 AM

Hi John,

Quote:


So they all have same wire guage? I did not know that...


Yes, I think so. The length of the wires and their resistances are the same. The wider low bass drivers of the IV and IVa does not have double runs of wire in the centre of the drivers.


Quote:


The writing on the T-1D are as follows:

RC-043863
46 55 (the 55 has line thru it)

LC-043863
46 58 (the 58 has line thru it)


These numbers are for the low bass drivers. What about the mid bass drivers?

Can you give me exact measurements of the drivers and the positions of the “tuning buttons” (where the diaphragm is clamped)? I am collecting information of the various Tympanis.

Are your mid bass panels looking like these?
http://farm3.static.flickr.com/2699/...b579fc9f_o.jpg

Are the low bass panels without tuning button?
http://farm5.static.flickr.com/4041/...de3ca05d_o.jpg

My own Tympani IIIA bass drivers look like this.
http://www.twin-x.com/groupdiy/album...mpani_IIIA.jpg



Quote:

I do not understand this...curvature?
Some drivers have a slightly curved back plate, the perforated sheet metal is curved. I thought my own Tympanis had flat back panels, but they have a minimal bend over the lowest spots of tuning. The areas with higher tuning are flat. The mid bass could be flat all over.


Quote:

The mylar on these T-1D seem to be in good condition.

Yes, but after 30 years I think the elasticity has changed, moving the tuning upwards a bit.


Quote:

Now again, the two pairs of bass panels are different on this T-1D. Since the design is a two way crossed at around 1000hz (I think), one of the pairs of bass panels have the two tuning buttons (I would think these were the panels needing to reach 1000hz). If I do not intend to go any higher than 250hz, why use all four panels? I am biamping so the 8 ohms is ok, and I can dial in the required amp gain to get the required SPL out of the driver to match the CLS SPL.

Using only one bass panel will give a rather low output. Two panels will give you at least 6 dB more output and reduce the distorsion/compression. The mid bass is what maked these Tympanis famous and it would be a pity not including it.

How are you going to integrate the CLS and the Tympanis? Do you intend to mount them in a common baffle/frame? I would try to mount the CLS so it will not pickup the vibrations from the bass drivers via the baffle/frame. The Tympani drivers benefit from a structure supporting the sheet metal not only around the edges of the drivers but also with some cross-members glued to the sheet metal back plates. This is a good example.
http://www.twin-x.com/groupdiy/album..._MG_IIIa_1.jpg

http://www.twin-x.com/groupdiy/album..._MG_IIIa_2.jpg


Roger

john65b 5th March 2012 12:34 PM

Roger,

My T-1d's look exactly like your T-IIIa's.

Quote:

Using only one bass panel will give a rather low output. Two panels will give you at least 6 dB more output and reduce the distorsion/compression.
I really only need the single lo driver panel. I have not noticed the output of the single panel to be low - actually blends very well with the output of the CLS. Nonetheless, I will complete the mid bass panels as you recommend...just take a little longer to complete...

I never noticed that my T-IVa's panels were wider than my T-1D's. No double center runs makes sense...with double runs at center you essentially are doubling the amplitude of the diaphragm, increasing the probability of contacting the magnets, correct? Is this not a bad idea?? I believe it to be a necessity since they had to make the 8 ohms...

I also have a pair of the lo/mid bass panels for a T-IIIa, but they do not look like yours or my T-1d's. They have two wooden beams across them on both lo and mid bass drivers.

I totally destroyed the mylar of one of these T-IIIa bass drivers trying to remove the beam (bad idea), but plan on eventually re-mylaring them anyway as the magnets look good (they were tossed as garbage. so they cost me nothing)

RogerGustavsson 5th March 2012 05:38 PM

Quote:

Originally Posted by john65b (Post 2933929)
Roger,

My T-1d's look exactly like your T-IIIa's.


There seems to be at least two versions of the I-D. So, your low basses are without tuning buttons like my IIIA?

Quote:

Originally Posted by john65b (Post 2933929)
I never noticed that my T-IVa's panels were wider than my T-1D's. No double center runs makes sense...with double runs at center you essentially are doubling the amplitude of the diaphragm, increasing the probability of contacting the magnets, correct? Is this not a bad idea?? I believe it to be a necessity since they had to make the 8 ohms...

I also have a pair of the lo/mid bass panels for a T-IIIa, but they do not look like yours or my T-1d's. They have two wooden beams across them on both lo and mid bass drivers.

I totally destroyed the mylar of one of these T-IIIa bass drivers trying to remove the beam (bad idea), but plan on eventually re-mylaring them anyway as the magnets look good (they were tossed as garbage. so they cost me nothing)

I have heard about those wooden beams before. Are you also member of some other audio forums? Magnepan User Group?

The Tympani IV (and IVa too, I guess) have wider diaphragms for the low bass (mid basses are not wider), 13 inches vs. 9 inches for I-C, IIIA and I-D. There are also 33 rows of magnets vs. 27. The lowest resonant frequency is 43 Hz for theIV and 40 Hz for the IVa. This lowers after some playing. I have noticed that longer periods without playing, require a bit of exercising of the speakers before they sound OK.

Yes, the effeciency drops as the impedance is raised. Running the low and mid basses in parallel "squeezes" more Watts out of most power amplifiers. As the moving mass goes down the effeciency goes up.

You can use the remains of your Tympani IIIA. Can you compare the magnets of the IIIA and the I-D? Are they identical? What about the thickness of the spacers around the edge of the drivers? The IIIA has1/8" Masonite and the magnets are 1/4" by 1/16". Spacing diaphragm - magnets 1/16" or slightly more where the back plates are curved.

If I lived in the US, I would let Magnepan replace the Mylar and wiring. You can remove the drivers and send them in "naked". I wanted to do that with my non-working Tympani IIIA bass drivers but shipping and customs both ways makes it very expensive.

There are some guys in Europe that are trying to setup a rebuilding facility. I am too far away to assist them but I have been asked.


Roger

john65b 8th March 2012 12:51 AM

1 Attachment(s)
I reconnected all the bad wiring connections on the bad T-1D panel. I used DAP Weldwood to secure the connections...I have been listening to the setup (single T-1D bass panel per channel) for a while and will leave it as is for now...got some fabric and some oak panels from teh local hardware store to dress up the T-1D to match the CLS.

Below is a pic of the setup...I really like this - Magnepan / Martin Logan / ICEpower / Audio Research D-75 all in one...

I am ABx'ing the Krell KSA-50 Clone and the Audio research D-75A amps - the Krell has a bit more gain, but otherwise very close sound wise...

tyu 8th March 2012 11:54 AM

Thanks for the pic an the info....

ApogeeLover 17th June 2012 09:57 AM

IVa restoration...
 
Hi all,

I've just bought a set of IVa's with the AR active valve crossover (in high end terms of cost - for penuts!) :D
Now trying to gleen as much info on their rebuild requirements...
Inital investigations show 3 out of the 4 bass panes are operational as are the 'true ribbon' tweeters.
However, both midrange panels are silent as the grave... So, I'm gonna work on those first.

Is D.A.P cement the only recommended glue out there now for re-setting the voice coil wire into place on the mylar?



John - Lovely job on the setup ! How is it all sounding for you?

Hi Roger - Any idea what the AWG figure is for the midrange panels is? Also, I'll get the info off the panel surrounds for you to add to your database. Is it possible to view your collected data ? Cheers.

-Andy-

RogerGustavsson 17th June 2012 03:53 PM

I am not sure about the AWG for the mid, 32 perhaps? The Mylar is thinner than other Magnepan, 6 µm. The mid of the MG 20 uses foil conductors. I would have asked Magnepan for it. The glue that Magnepan are using since 2004 are well proven.

I wish I had a database but I have not. I have some resonant frequencies, and the dimenions of the Mylar etc. As you have the T-IVa, can you tell me more about them? I would like to know the position of the tuning buttons. Perhaps some pictures too?

Roger


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