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In Reply to: RE: Absolutely! ... posted by ghost4man on September 08, 2016 at 01:06:35
Well, I think you have quite a heroic bracing effort. The driver frames are supported by steel slats from the back? And the wood is backed by steel beams and that goes into the back struts and big feet. That may have more to do with the increased performance than the QR - which Roger is right to question regarding resolution into the midrange/ However, when you get the DSP running you can compensate by lowering the XO to the md/tweet and use a steep slope.
You are far more into the club than I am. The T IV are my first and only maggies, I just went for what I wanted when I could afford to and had the space. But my mids are not maggie mids so I am standing with one foot out of the club, though the BG Neo8 are planar .and in a line source fitting into the midrange slot on the TIV
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Satie,
You can attribute whatever increases in performance to the designer Peter Keenan who worked on both the wooden frames AND the metal stands. What I like about the stands is that there is no welding. It's all bolted together. If you want to make the stands wider for whatever reason to accommodate bigger Maggie's then you simply get a longer cross brace. That's it. The drivers are fixed directly onto the wooden frames. The metal uprights then fix to the wooden frames. It is extremely solid in design. The length of the stands at the base is only 450 mm. They can easily go down to 350 mm in my opinion. I can position a 100mm masking tape at the back of the base to tilt the entire system forward and the speaker holds down. No issue.
My intention was to go even further than this. I am hoping to rewire the existing tweeter, again in QR with foil from what you would find on the 20.7 mid. That was supposed to happen but ideological differences crept in. I will keep everyone posted as to whether this takes place or not. As I understand it there were no changes to 1st order frequencies.
Ozzie
Ozzie wrote: "My intention was to go even further than this. I am hoping to rewire the existing tweeter, again in QR with foil from what you would find on the 20.7 mid."
The foil used in the mids of the 20.7 is too wide (0.0005"x0.1") to be a direct replacement for the round wire in the Tympani I-D tweeters. In your case with a ribbon tweeter, it might be a step in the right direction as, in theory, it shifts the original tweeter into a slightly lower register (8 ohm=Tympani I-C and Tympani IIIA). I am using that foil in my T-IVa mids. You could also think about the use of thinner Mylar for your tweeter rebuild.
Roger,
I just want to reiterate that I was not in a position to confirm either way whether that foil at that dimension was not only a good physical fit but translated into good music. I am hoping that in the next couple of months I can come back and report on this.
I believe the black stuff at the top of the panels is certainly NOT tar but another type of glue to prevent delamination. I will try and get this information for you all. It feels quite "rubbery". Its something that the repairer has been using for a while to great effect. It is not standard to the repair.
Ozzie
Roger,
You are correct in the sizing. You are however not correct that it is too wide. It can be done and was done. The only issue was that working with it was problematic.- it kept breaking. The only reason why the job wasnt completed was due to circumstances that I don't really want to get into at this stage. To be fair we didn't get to the point to be able to test for efficacy.
You are quite correct about Mylar thickness. We were heading down that route but the repairer was short on Mylar. One of the channels had to have the mylar replaced due to damage. Magnepan do NOT provide Mylar the customers for purchase. It would have meant sourcing it from elsewhere which we could have. However, again and frustratingly so, ego got in the way and the work didn't go in the direction I had hoped for. But yes the repairer did comment that thinner Mylar would have been a good direction to head into. At the time he didn't want to create a disparity between the two. It's also a pain in the ass to replace. Magnepan won't repair tweeter panels on the 1Ds. They replace them. In fact they strongly advise you even attempting to remove the driver. I did. Luckily I had no issues. It's all about getting the correct tensioning of the Mylar which without proper setup is not easy. Luckily the repairer was willing to have a go and it worked.
I would have still liked to have at least tried t see what the result would have been like. But at no stage did the repairer think that size of the ribbon would be prohibitive. It was worth a shot and still so.
Cheers Ozzie
Well, it is not too wide to use but it will give a different impedance /resistance. The I-D tweeter is originally about 4.8 Ohm. With the smallest size foil Magnepan can offer, you will have about 7.4 Ohm, you loose about 2 dB and the mass is higher. Yes, this foil easily breaks but it is still doable. My T-IVa uses more of this than any tweeter.
I have been workning on my Tympani IIIA tweeters. Replacing the Mylar with a thinner one, cutting down the width of the driver in order to place it closer to the midrange driver etc. The driver is 20 cm wide but the diaphragm is just 6 cm. I ended with 10 cm wide drivers. I still did not like the very closed sheet metal in front of the driver. There is just about 11% of open area.
Roger,
That figure of 7.4 ohms that you state - is that something that you have measured yourself using that specified foil size for the T1D tweeter?
Cheers Ozzie
I have that foil on my Tympani IVa mids. It has the same cross sectional area as a round wire with AWG 32, 0.032 mm2, or 0.85 Ohm/m. In the Tympani tweeter there is 8.8 m, about 7.5 Ohm in total. That is what the earlier tweeters, before the I-D had.
30 years ago, that is before Magnepan started to use foil conductors, I cut 10 m long strips of foil, 1.5x0.018 mm. Wanted to use it for modifying my Tympani tweeters. Also had 6µm Mylar. Never finished the project as I wanted a more open area in front of the diaphragm.
Hi Roger,
Thanks for that. Okay you have convinced me that I should pursue this further and perhaps do the relaying on the existing tweeter with the foil. Bear in mind that with the addition of the version 2 true ribbon the old tweeter would be my new mid range.
cheers Ozzie
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