| 1-Pi/2-Pi [message #61673] |
Tue, 05 January 2010 16:58  |
RDLewis
Messages: 15
Registered: September 2009
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Chancellor |
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Hello wayne
You recently send me plans for the 2-Pi and tower, it was only when I saw the latter that I found they are pretty big beasts especially for a more compact room. I was initially attracted to the 1-Pi towers as shown on the Walton Audio site, but you said the 10 would have greater bass potential. I would really like a more compact (say 65 litres) tower any comments on the compromise ?
But my main question concerns the sonic differences between the 8 and 10 besides the bass depth. As the crossover is the same for both I assume there is a family similarity. Besides its musical abilities I want good voice reproduction as I listen to a lot of documentaries/plays via the BBC radio and of course watch films etc.
Not having heard either, I would be grateful if you and any other member could offer their subjective opinions on the merits of the 8 and 10
Thanks
Roy
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| Re: 1-Pi/2-Pi [message #61674 is a reply to message #61673] |
Tue, 05 January 2010 18:36  |
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Wayne Parham
Messages: 18785
Registered: January 2001
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Illuminati (33rd Degree) |
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It really does boil down to the bass, the character below 100Hz. The electro-mechanical parameters of the Alpha 8 are very different than they are in the Alpha 10. Those parameters are largely responsible for bass response. Above 100Hz, the drivers are similar, but below 100Hz, they're very different.
Of course, in all things, there is a balance of priorities and the difference between them is manifested in the cabinets required. The Alpha 8 is happy in small boxes but the Alpha 10 really needs a pretty large cabinet. As an example, The one π cabinet at 1.0ft3 is plenty large enough for the Alpha 8, which can be used in vented boxes from about 0.75ft3 to 2.0ft3, tuned to 55-60Hz. The two π cabinet, on the other hand, is about 1.5ft3, which is right at the bottom end of what can be used for the Alpha 10. It should be put in vented boxes from about 1.5ft3 to 5.5ft3, tuned to 35Hz-40Hz.
What this means is the Alpha 10 can provide quite a bit more bass, but it needs a larger box to do it. That kind of goes without saying but the point I want to emphasize is that the Alpha 8 can be put in a a cubic foot box if you can sacrifice bass and it will still sound nice. The Alpha 10 can't, because in an undersized box it will become underdamped in the midbass and sound kind of thumpy, without any real bass. Such a box would cause voices to sound overly throaty, and stringed instruments will be artificially heavy sounding but without any real bass. On the other hand, if you have a box larger than around three cubic feet, the Alpha 10 is fine but the Alpha 8 won't be, at least it won't make any real bass.
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| Re: 1-Pi/2-Pi [message #61684 is a reply to message #61673] |
Thu, 07 January 2010 16:00 |
RDLewis
Messages: 15
Registered: September 2009
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Chancellor |
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Thank you gentlemen for your replies, the Alpha 10/2-Pi looks like the direction I should follow.
After you sent me the Plans for the above, I did some more searches for the them on your site. To one answer you said that you used MJking's worksheets to model the Towers. Now I have the original "free" version so I put the specs and dimensions and the results looked good. Out of interest I tried out the above using his "ML TQWT" and managed to come up with a very similar response (with different Port size). The box would be narrower and shorter, which would be more acceptable in my room. Modeling is all very well, but would it sound as good?? Though MJK does state that TL's, reflex, MLTQWT all use the same equations.
What is your opinion of the above, have you tried TL's? Do you have any frequency/impedance, charts, etc, for the 2-Pi tower
I would be grateful for any further advice
Roy
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| Re: 1-Pi/2-Pi [message #61688 is a reply to message #61684] |
Fri, 08 January 2010 09:03 |
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Wayne Parham
Messages: 18785
Registered: January 2001
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Illuminati (33rd Degree) |
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| RDLewis wrote on Thu, 07 January 2010 16:00 | After you sent me the Plans for the above, I did some more searches for the them on your site. To one answer you said that you used MJking's worksheets to model the Towers. Now I have the original "free" version so I put the specs and dimensions and the results looked good. Out of interest I tried out the above using his "ML TQWT" and managed to come up with a very similar response (with different Port size). The box would be narrower and shorter, which would be more acceptable in my room. Modeling is all very well, but would it sound as good?? Though MJK does state that TL's, reflex, MLTQWT all use the same equations.
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I don't build transmission lines, as I've always used Helmholtz resonance to tune the box instead of pipe modes. I designed the box with standard Helmholtz resonance formulas and then used Martin King's spreadsheets to verify that port and driver placement would prevent higher standing waves from generating peaks in response.
If you've studied what Martin King does, he essentially advocates using the primary pipe mode to tune the box but then suppresses all higher modes using port and driver placement. This is very similar to the approach I take, except the transmission line speaker uses the fundamental standing wave mode as the primary tuning mechanism, whereas my speakers use Helmholtz resonance. The results are the same, when properly done.
What can get a speaker builder in trouble, can happen either with either mechanism. If the speaker is designed right, I don't suppose which mechanism is chosen, both will probably give identical results. The main thing is to suppress those higher modes. If the box is large, and especially if it's a tower (long and thin), then it will have pipe modes, no matter what you do. Likewise, if it has a port, then it will have Helmholtz resonance.
It doesn't really matter if you call such a speaker a transmission line or bass reflex box - both standing waves and Helmholtz resonance are happening. What matters is that, in the end, the system provides the desired response. The primary resonance - whether it be the first pipe mode or Helmholtz resonance - must be tuned appropriate to give the intended transfer function on the low end, and the higher standing wave resonances must be suppressed either by placement or by damping, or both.
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| Re: 1-Pi/2-Pi [message #61720 is a reply to message #61673] |
Thu, 14 January 2010 08:09 |
RDLewis
Messages: 15
Registered: September 2009
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Chancellor |
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Hello again,
A few months ago I discovered this site "www.prodance.cz", (some of you may be familier with it already). Its a Slovakian site and provides test results for a large number of Pro drivers. Click on the English box, then go to the "MLSSA Data" box at the top.
Not having been there for a while, I discovered they have added the Alpha-8 and 10, as well as the other units in the Pi range. What it shows is that the 10 has a somewhat smoother frequency response and cleaner "waterfall". Which may be "another" reason for the preferance for the "10" over the "8" shown in the previous replies. Its interesting that the larger cone seems to offer a better controlled result!?
Roy
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