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Old 19th February 2009, 01:49 AM   #11
The one and only
 
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I haven't listened to both in a reasonable time span and under
similar enough conditions.

I can't offer comment until I do.

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Old 19th February 2009, 02:48 AM   #12
freddi is offline freddi  United States
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thanks Nelson - -"acceptable" sounds better than the other way...
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Old 19th February 2009, 02:51 AM   #13
badman is offline badman  United States
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looks like that notch wants to be deeper but otherwise pretty good
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Old 19th February 2009, 03:43 PM   #14
freddi is offline freddi  United States
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for those with less room space - would a "No-Box" baffle work about as well?
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Old 19th February 2009, 04:11 PM   #15
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>>> The Beta comes with a magnet.

Yes, the Alpha 15 has a pretty small magnet. I prefer the look of the Beta from the back and the front. But the Alpha's do the trick in an H-Frame. How do you have the Beta's hooked up? H-Frame, ported??? Even tho they don't spec out to work in an OB as well as the Alpha's i wonder how they would sound?

They are both black and round.
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Old 19th February 2009, 04:46 PM   #16
MJK is offline MJK  United States
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Nelson,

Deciding between a higher Qts driver or a lower Qts driver but with EQ is an interesting trade-off. If you select a high Qts driver like the Alpha 15A the magnet is smaller and the cost is a little less compared to the Beta 15A with EQ. The question I have concerns the following scenerio, selecting the Beta 15A with a lower Qts and then adding EQ to push the bass up don't you end up at the same performance point? If both options provide "flat" bass to 40 Hz in your OB does it matter sound wise which path you take? Both drivers should still be working as a single degree of freedom system moving the same amount with rigid cone motion to produce the same SPL/W/m. For bass frequencies below 200 Hz and in a common moderately sized baffle, what advantages or disadvantages do you see using a Beta 15A and EQ over an Alpha 15A?
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Old 19th February 2009, 05:35 PM   #17
Vix is offline Vix  Yugoslavia
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Hi

In my opinion, Beta 15 was not so good without some form of EQ. But, since I applied Graham's T-bass circuit, it's fine .
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Old 19th February 2009, 06:56 PM   #18
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Quote:
Originally posted by badman
looks like that notch wants to be deeper but otherwise pretty good
Actually, the notch depth was based on listening. Routinely the
perception of FR drivers in this region is more forgiving than on-axes
1M measurement.


Quote:
Originally posted by freddi
for those with less room space - would a "No-Box" baffle work about as well?
This is a No-Box baffle as I understand the concept. The front-
to-back distance is increased a bit by the side supports as described.

Quote:
Originally posted by MJK Deciding between a higher Qts driver or a lower Qts driver but with EQ is an interesting trade-off. If you select a high Qts driver like the Alpha 15A the magnet is smaller and the cost is a little less compared to the Beta 15A with EQ. The question I have concerns the following scenerio, selecting the Beta 15A with a lower Qts and then adding EQ to push the bass up don't you end up at the same performance point? If both options provide "flat" bass to 40 Hz in your OB does it matter sound wise which path you take? Both drivers should still be working as a single degree of freedom system moving the same amount with rigid cone motion to produce the same SPL/W/m. For bass frequencies below 200 Hz and in a common moderately sized baffle, what advantages or disadvantages do you see using a Beta 15A and EQ over an Alpha 15A?
After years of playing with FR drivers I have learned to spend the
extra couple of bucks ($8 in this case) on a better magnet and maybe
a little EQ. True, you can get mechanically similar results, but IMHO
the sound is really not the same.

Lowthers, which is a magnet cult if there ever was one, provides the
best example. Depending on what you're looking for, there is
a Lowther magnetic motor to meet your needs. Ceramic, Neodymium,
Alnico, Ticonal, Permendur. Medium, Large, SuperSized and Field Coil.
Voice coils regular, and over-hung (Oh, Baby!).

As the sensitivity of the motor and the exotic-ness of the magnet
goes up, the measured and perceived response alters. Using the PM6
type as an example, from about 200 Hz to 10 KHz the PM6C @8ohms
fits in a 20 dB window. The PM6A @8ohms fits a 15 dB window. The
PM6A @16ohms fits a 10 dB window, and the PM5A (bigger magnet)
@ 16 ohms fits a 15 dB window.

A pair of PM4A's (monster magnet) was deposited on my floor this
morning. I will get some ruffians to carry them to the listening room
real soon now.

IMHO so far the PM6A @ 16ohms provides the best un-equalized
experience, but if you equalize all of them with low Q filters to meet
its 10 dB window, the subjective quality starts lining up as a
function of magnet expense.

What do I mean by subjective quality? That's an individual thing,
but as a general rule a high quality driver makes me go through a
lot of my record collection in one sitting. What quality am I hearing?
More detail for sure - things come out in sharper relief, the same
little bits that you don't notice with more ordinary drivers.

Similar effects with the Feastrex, and I'll let you know about the
PM4A's.

Have I even tried the Alphas? Naaaaah.

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Old 19th February 2009, 07:34 PM   #19
MJK is offline MJK  United States
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Nelson,

Sorry, my question was not clear.

I am totally focusing on the 15" bass driver for the OB, the trade-offs between the Alpha 15A and the Beta 15A with EQ. For the frequency range from 40 Hz to 200 hz what are the theoretical pro's and con's of using either of these Eminence drivers. In my simplified understanding, it would seem that the EQ applied to the Beta 15A is driven by trying to make it perform like the Alpha 15A. I am looking for some other advantage that would justify spending the extra money and equipment to implement the Beta 15A and an EQ circuit. Granted the cost difference seems small, but for some it may not be trivial. I am looking for a list of trade-offs between the two types of bass drivers (Qts > 1 and Qts < 0.7 with EQ) and the impact/benefit of EQ so people can make intelligent decisions (including me).

As far as the different varieties of Lowther drivers, I have a few and have my opinions on my favorite versions. Again in my opinion thay are all great drivers and I like different models for different reasons. To be honest, my least favorite are the A series. I like the DX series for performance and the C series for cost. Unfortunately, a couple of the more exotic ones that I wanted to try are out of the picture due to lack of funds. I will try top limp forward with my current collection.
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Old 19th February 2009, 10:13 PM   #20
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No, it is my answer which lacked clarity

We are probably listening for different things, and given our
different approaches, it's remarkable that we agree as much
as we do.

If I tried the Alpha, I might be surprised.

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