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In Reply to: RE: Bass panels one after the other? posted by AkuAnkka on June 16, 2014 at 04:45:53
The bass driver of the 2.6 has different tuning than the Tympani basses. The mass of the wire is also different, double for the 2.6. One or two identical bass drivers will not change the low frequency roll-off.
There is something strange with the technical data on the 3-series, the cut-off frequency is not as low as indicated. My 3.6 roll-off below 42-44 Hz, 18 dB/octave as any open panel. My Tympani IIIA roll-off below 31-33 Hz. I have not checked my Tympani IVa but expect them to be similar to the IIIA.
Follow Ups:
"There is something strange with the technical data on the 3-series, the cut-off frequency is not as low as indicated. My 3.6 roll-off below 42-44 Hz, 18 dB/octave as any open panel. My Tympani IIIA roll-off below 31-33 Hz. I have not checked my Tympani IVa but expect them to be similar to the IIIA".
I don't know if these numbers are accurate: http://www.integracoustics.com/MUG/MUG/articles/speakers.html
But it says that;
- Tympani III-A: 42hz
- Tympani IV: 43hz
- Tympani IV-A: 30hz
- MG-20- series: 25hz
It's quite surprising to see that MG-20's would really go lower than IVīs??
When you switch around the T IV panels and wall load the deep bass panel and place the upper bass in the middle, you get a rolloff at about 25 hz. Together with the tangent or oblique room mode when the speakers are placed midway into the room near the sidewalls, you get an elevation of the 30-40 hz band - I set it up to have the deep bass 3-6db above the midrange 30 to 50 hz.
Well, the 3.6 has a "hump" at 50 Hz. The "hump" for the T-IIIA and the MG-20.1 is at 35 Hz. Two drivers lowers the distorsion for the same soundpressure. Magnepan states 34 Hz for many 3-series, not really true...
"One or two identical bass drivers will not change the low frequency roll-off". But Roger, if I use active setup with digital equalizer such as DEQX, shouldn't it be possible to get a bit more lower freqency? I mean; two identical drivers will give 10db more on a whole frequency range (or was it so...?). So, I need to drop 10db from the basses to match mid's level again. But if I would not cut anything from the lowest frequencies, only above roll-off point, wouldn't it give a bit more basses on the lowest section?? I don't know how much, anyway...
On the other hand; two bass drivers per side could give a bit more sound pressure and/or less distortion on higher basses, but I don't know if it actually makes any difference in real life?
Roger; did you have any comment on my post posted on June 16, 2014 at 09:01:38..?
I can answer You Aku.
You will get somewhat louder sound and lesser distortion.
But the loudness depends on if You connect them in series or paralleled.
But the distortion is only lesser if the drivers are very close together.
But You have to get that You will NOT be able to play any louder at all!
This because the chain is not stronger then the weakest link and the membrane that would before the build hit the magnets will do it again at the same db and at that hz that the tuned part will resonate.
No gain apart from lowered distortion!!!!!!!!!
The one who succeeded was the one who didn't know it was impossible.
Ok, thanks JLindborg! I don't care about playing any louder, I'm just thinking is there any way to get more lower bass from Maggie bass panels, somewhere near 30hz or even a bit lower. Of course buying 20.x should do it, but it's just out of my budget.
BTW; what actually is purpose of those tuning buttons? What would happen if they are removed...?
You can use EQ to boost.
But be aware of the fact that particularly the bass frequencies are directly related to move a LOT of air.
With a fixed area of membrane, the only left thing is larger excursion. And with as little excursion ability that a Magnepan speaker has, You are not going to be able to play any "loud".
Removing the tuning buttons will only be possible by removing the whole membrane.
Cheers!
The one who succeeded was the one who didn't know it was impossible.
JLindborg; "But be aware of the fact that particularly the bass frequencies are directly related to move a LOT of air. With a fixed area of membrane, the only left thing is larger excursion. And with as little excursion ability that a Magnepan speaker has, You are not going to be able to play any "loud".
But wouldn't it be so that using twice the driver area, those drivers need to move only half of that with one driver, on a same volume level? So basically I could add a bit more level on the lowest frequencies (25-40hz etc.) with EQ, without having to be afraid that driver hits the magnets?
I don't know if my thinking is totally wrong with this...?
That is only true if You actually ADD bass area.
Joining 2 panels as You described with the magnets opposing each other will not ADD any surface at all!!!
It will still be the same amount of square meters/feet.
Joining them side by side will add to surface area and will double the space they take up in the room.
That is why they built the Tympani models! To make up for the limited excursion ability of the Magneplanar design.
Cheers!
The one who succeeded was the one who didn't know it was impossible.
No no no, that idea of joining two panels was already rejected. So now I'm thinking if two 2.x (or such) panels would give any benefit when positioned side by side, maybe on a one stiff wooden panel? It might not be IVA- like, but could it be even close?
BTW; why couldn't two unequal drivers connected parallel be driven with one amplifier? I think that even IVA- drivers are not quite similar, and for what I have understood, they are often driven with one amp..?
Sure You can drive 2 panels with 1 amp! No problem at all!!!
If You are serious with low frequency reproduction with a Magnepan dipole, You have to use panels without tuning buttons.
If You have tuning buttons You will restrict movement at each place a button is placed and thus the whole membrane will NOT move as 1.
1 tuning button will render about 2/3 of usable membrane the rest is downforced by its own mounting at the surround AND the button creating a curved movement. So in practice, to say that the whole of the membrane is usable as bass reproduction is EXTREMELY faulty reasoning as it does NOT move like a piston at all!!!
Only the center of the membrane is close to a piston movement and the rest is a declining function of a curve.
Cheers!
The one who succeeded was the one who didn't know it was impossible.
"If You are serious with low frequency reproduction with a Magnepan dipole, You have to use panels without tuning buttons."
Do you JLindborg (or anyone else here) have any experience on removing those buttons? Would not want to be first one to try, just to see that it destroys the whole driver and it can't be fixed back...
On the other hand; why would Magnepan use those buttons, if removing them would be better? Or does it have something to do with upper frequencies?
Magnepan uses tuning buttons for the very reason they are called just that.
To remove them You will have to ruin the membrane and replace it with a new with specified tension to get the resonance frequency You need.
Cheers!
The one who succeeded was the one who didn't know it was impossible.
Unfortunately, he doesn't understand the trade-off the buttons provide and the result if they were removed.
If the folks at Magnepan were to construct a bass transducer (for one of the buttoned systems) with their normal procedure with the exception of not gluing in the tuning buttons it would yield a drum skin with a large resonant mode at a single frequency. This resonant frequency would be much lower than the existing one(s) and then front/back dipole cancellation effect/distance created by the baffle width would no longer line up to EQ it.
It's simplistic to think you could achieve a superior result just by removing the tuning buttons and leaving all the other design aspects the same. I'm not sure that's what he's advocating, but if it is, it won't work. :)
Hope that makes sense.
Cheers,
Dave.
True, you cannot remove the buttons without destroying the diaphragm, the buttons are glued to a piece of foam tape sitting between the Mylar and the magnets.
Well, you can't take out the buttons without making holes in the Mylar, but you can fix the holes with packaging tape. For the bass freq you want to cover with it that should not be a problem. The downside is that the speaker will never sound like the 2.x it once used to be and will have really low resale value.
Wiring it up you would want to have the second bass driver kicking in at a lower freq so as to avoid smearing so you would hook it up in parallel with its own new inductor calculated to kick in at the 100-200 hz range.
The tuning buttons are to the distribute the resonance behaviour over a larger frequency range. If you remove them it will change the low frequency behaviour. Not sure if you can use a 2.6 without the buttons. Maybe the diaphragm will hit the magnets early? A low resonant frequency will result in a large peak that takes a lot of excursion, lowers the maximum soundpressure. One of the buttons came loose om my 3.6, made an awful resonance around 90-100 Hz.
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