[Redefy Audio]

i have not tried the AE woofers, but i have compared between Alpha15 and Beta15.
here is my conclusion :

Beta15 have much clearer bass presentation overall, it has more control.
Alpha15 is muddy.

ive used them in OB 60 x 120cm baffle with 100w classAB power amp and xo with miniDSP 2x4.

i think to get a good sound, at least you will need beta15.

btw, i ended up mixing them together 2x15 per side. which i think best of all.

cheers
henry

[FullRangeMan]

HENRY: good to know it, thanks for inform.
If the Beta15A with a low QTS=0,58 had a good bass, the Delta Pro 15A with a too low Qts=0,40 also would had a good bass...

[Redefy Audio]

fullrangeman, i eq'ed on minidsp, if u do passive then u need to do eq as well, like troels did with his OB deltalite15LF

cheers
henry

[FullRangeMan]

OK OK, I missing this detail. Thanks for mention it.
I feel without EQ, the only woofer that do a good bass is the usual Alpha15A, seems.
Thanks alot.

[scorpion]

I hope you will be satisfied with your 'Jamos'. Regarding Alpha15s and Beta15s there are evidence that the Betas sound more articulate and clearer than the high Qts Alphas as I posted above.

Alpha15 has Fs = 41 Hz and Qts = 1.26 and Beta15 has Fs = 35 and Qts = 0.58. Mostly (in OB) you have to cross from bass to midrange about 200-300 Hz were in fact you will cover a lot of instrumental and voice fundamental tones in the bassrange. I have used Alpha15, AE IB15 and A&D R1524. I cross at 277 Hz sharp between bass and midrange and to me the difference between AE IB15 and Alpha15 is like Night and Day, like you pull a veil from the speakers. I have no experience with the Beta15 but others say they are that better than the Alpha15.

But Alpha15 bass superiority is a bit of a myth. Simulation of the units on a 40 x 20 " baffle, two of them placed about the same as on your Jamo baffles looks like this:

Alphas first, crossed at 200 Hz 2nd order L-R:





Betas, crossed at 160 Hz, to give the same SPL level as the Alphas, 2nd order L-R:



So what is the main difference. The Betas may be about 3 dB down compared to the Alpha at 40-50 Hz in all other frequencis they will be more or less equal.
This is the trade-off then, some dBs in the very low bass instead of overall clarity and articulation.

/Erling

I quote myself from another thread. This is a comparison of un-EQed Alphas and Betas .

/Erling

[MJK]

So what is the main difference. The Betas may be about 3 dB down compared to the Alpha at 40-50 Hz in all other frequencis they will be more or less equal.
This is the trade-off then, some dBs in the very low bass instead of overall clarity and articulation.

Erling,

Above 100 Hz the plots are essentially the same, below 100 Hz the Alpha 15A has more bass extension. Are you saying that the added depth of bass causes a loss of "clarity and articulation"? Looking at the plots I would expect that the Beta 15A would have a drier bass without as much low end growl, is that what you mean? I have seen speakers that are rated highly that do not have much deep bass below 100 Hz and the bass is described as tight and quick, this works for many people.  If the low frequency bass response is the difference, why do the AE Dipole 15 or IB 15 have similar if not worse clarity and articulation issues since they go even deeper than the Alpha 15A.

Some people love the Alpha 15A drivers while other people complain of poor bass performance and sloppy response. I am struggling to understand if this is driven by personal preference, a amp/system issue, or a room driven response. I am having a hard time coming to grips with it just being a driver issue, the T/S parameters should be fairly consistent but what people are hearing seems to be totally different.

Martin

[matevana]

I am having a hard time coming to grips with it just being a driver issue, the T/S parameters should be fairly consistent but what people are hearing seems to be totally different.

Martin

Martin,

One possible explanation would be an amplifier's damping factor, particularly with LF drivers that have weak motors and a corresponding high Qts.  An alpha in a system with a high damping factor will likely sound much different, due to the amps ability to quickly damp undesirable cone movements brought on by the mechanical resonance of the driver, particularly near Fs.  I believe the system's damping factor would include a combination of the amplifier's damping ratio as well as any influence brought on by large inductors, etc. in a passive filter placed between the amp and driver.

In any event, I too have heard alpha's described by people as being "slow" or "sloppy", for what that's worth. 

[Architect7]

That is a very biased review of the two drivers presented by a manufacturer with a definite interest in the final conclusion.

I completely understand the conflict of interest introduced by the context of that test.  However, I am having a hard time seeing where in the test results any bias could be introduced.  John does a pretty goid job identifying the qts spike at 70hz which is probably the muddiness many people hear.  This would especially be applicable for those using passive crossovers.  Of course, a grain of salt should always be taken with "competitor testing" but I think the numbers speak for themselves.  Your thoughts?

[scorpion]

Hi Martin,

My intention with the post was only to question Fullrangeman's claim that the Alpha15s are the only speaker to produce bass without any EQ on OB.
I should have quoted him on that passage.

Now EQ is of course introduced also in a passive setup for instance with the choice of crossover frequency and for the basspeaker also the lowpass slope.

/Erling

[MJK]

I completely understand the conflict of interest introduced by the context of that test.  However, I am having a hard time seeing where in the test results any bias could be introduced.  John does a pretty goid job identifying the qts spike at 70hz which is probably the muddiness many people hear.  This would especially be applicable for those using passive crossovers.  Of course, a grain of salt should always be taken with "competitor testing" but I think the numbers speak for themselves.  Your thoughts?

Those tests (I am not sure if the data is tested or simulated results) were probably done in an infinite baffle. Once you add the OB's 6 dB/octave roll-off to both drivers the hump from the Alpha's high Qts will be flatten out and no longer present in the SPL plots while the Dipole 15 response will be rolled off significantly and not flat down to the fs. Again, I think the results questionable with respect to an OB speaker system.

Martin

[MJK]

One possible explanation would be an amplifier's damping factor, particularly with LF drivers that have weak motors and a corresponding high Qts.  An alpha in a system with a high damping factor will likely sound much different, due to the amps ability to quickly damp undesirable cone movements brought on by the mechanical resonance of the driver, particularly near Fs.  I believe the system's damping factor would include a combination of the amplifier's damping ratio as well as any influence brought on by large inductors, etc. in a passive filter placed between the amp and driver.

In any event, I too have heard alpha's described by people as being "slow" or "sloppy", for what that's worth.

That is definitely a possible explanation for the different opinions on the driver. Many people really like the Alpha 15A driver, more then don't like it.

When I had a passive crossover and a single SS amp driving my OB speakers I tried a tube amp which should of had the effect you describe. The exact opposite problem occured, the bass disappeared. The 15 watt tube amp was not happy driving the system with a crossover in the 200 Hz range, this is also a common problem I hear from tube amp users who have built my simple two-way OB design.

My point is that I hear very different experiences from DIYers trying the Alpha 15A, some good and some bad, and I am not sure if this is just personal preference or a system problem.

Martin

[jacozz]

Personally, I don't really understand why people insist of driving 15 inch woofers with their flea-watt tubeamps?
Why not instead, get a couple of cheap dedicated sub-amps with built-in active crossovers? And some of them even have manual EQ built in. In my humble opinion every bass speaker needs EQ to behave in a normal living room anyway, OB or not...

One thing is for sure, those big woofers need some power to keep them in place.
Use your expensive tubes on the mid/high drivers instead.

[DBO]

If it is still of any help in this topic, I now have direct experience in comparison of Alpha 15A and AE LO15, both working in pair on open baffle and in range up to 1.2 k.

While Alphas worked surprisingly well, AEs are significantly better, this is no small difference - overall ease and dynamics, resolution, low bass energy.

Difference in price is large, one AE cost a bit more than four Alphas, but I'm very glad I invested. 

[versus rider]

I have found the alpha to not sound great above 200Hz until I braced the magnet as suggested by someone here. It nows sounds superb up to 350Hz where I cross it to my 200Hz horn. I haven't tried it at 500Hz as I have no interest to do so.