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In Reply to: RE: Are my ears really that sensitive? posted by Roger Gustavsson on September 10, 2014 at 12:06:51
Hi Roger,
Thanks for the tips.
The MGIIIas have magnets to the front, so its not so easy to add damping, but maybe I can suspend something like you say, or reverse the speakers back to front (though that will mess up my tweeter resistor tuning). Have you any ideas what's a good damping material to try.
I have tried measuring the FR sweep again using the Anthem ARC system in my MRX500 AV receiver (this time with a 0.47 ohm tweeter resistor installed instead of 1 ohm), though as we know dipoles are hard to measure so this is probably not quite what we hear. The output does look quite strong around 1-2 KHz, but its not as bad or a peaky as the measurements I took the other week before I changed the mid cap from 10 to 11.2uF and decreased the tweeter resistor. I guess the improvement in the peakiness has come from increasing the mid parallel cap.
I will try measuring at different positions in the room, - in fact with these graphs you can measure between 5-10 positions for a single graph and it averages it. I was doing 5 positions quite close around the listening area, which was probably not the best way to do it!
One thing I will say about the MGIIIa is that the bass (when they are run full range) is good. It's bigger and more punchy than the MG3.3Rs. Not sure why. The bass panel tension is different of course, - two buttons on the MGIIIa and one on the 3.3R and tuned differently.
Follow Ups:
"One thing I will say about the MGIIIa is that the bass (when they are run full range) is good. It's bigger and more punchy than the MG3.3Rs. Not sure why. The bass panel tension is different of course, - two buttons on the MGIIIa and one on the 3.3R and tuned differently. "
The deep bass on my IIIa's is a completely different beast from my 3.7i's. My room is real favorable to 30 hz, and in the right set up I can get good bass down to the upper twenties with the old model, with a small and appreciated peak at 32. The new model only reaches into the upper thirties. However, the middle and especially upper bass is substantially better and fuller on the new guys. On most music, the new models have punchier effective bass. Considering I can also get better low bass from a good sub, I think the tuning of the new models is more practical for me.
One thing I forgot to mention for dealing with the peaky upper mids, is that I bought a pair of DWMs. This fills in the upper bass and lower mids and balances the IIIas. I am not currently using the DWMs with the 3.7i's. They simply do not need it. The IIIa's benefited greatly.
Oh, and I tried placing felt over the rear of the midrance at one time. It definitely affects frequency response and depth, but I was not happy with the overall effects in my room. It was a short lived experiment. Oddly it didn't just decrease mids. It increased it at some frequencies and decreased it in others. I don't know why.
Thanks for the info. Yes I guess the 3.7i has slightly less ultimate extension than the older models as the bass driver has to work up higher due to the first order crossover. Still sounds great if the bass quality is better. Will have a wait quite a while for used ones to turn up on the market. I don't want to get a 3.7 if I can't upgrade it to "i" spec (I'm in London, UK).
Thanks for the info on the damping you tried, and the DWMs. Might get a pair of those at some point soon anyway, as they look like useful devices.
Davy,
I meant adding damping or diffusors behind the midrange driver. You can also try to locate where this midrange peak is alonge the midrange driver. I think the frequency response is slightly different along the driver in the vertical plane. I have not seen any strange peaks in my own Magnepan speakers, maybe you hear some sort of distorsion? No loose wires or buttons?
Hi Roger,
Yes I realise you meant add damping behind the driver, was just wondering what sort of damping to use.
I've did dealm repair on these IIIas a while back, no problems inside. Like Swamis Cat says above, the MGIIIa with stock crossover is just peaky in the mids, which I am sure is the issue I am experiencing. Like we said before Magnepan addressed this issue in later speakers. In fact when i had my 3.3Rs stock there was too much suckout in the midrange for me personally, though it was still probably easier to live with than a hard midrange sound. My father had a pair of original MGIII and those were not as peaky from memory and sounded good. Might revert to that crossover and see what happens, its quite easy to do from MGIIIa stock and much easier than changing all the values in the crossover. I already have the 35uF external HP caps made up. The imaging etc might change but to be honest I don't' really care if the tone/FR is better.
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