[rythmik]

When I plug the SW-12-16 numbers into a different spreadsheet I get (essentially) the same numbers as Erling.

At Xmax (18mm), free-space SPL at 1 meter is 93db at 20Hz and 98db at 30Hz.
A dipole configuration (I assumed D=300mm...I'm not sure if that's correct) yields 74db at 20Hz and 82db at 30Hz.

That's a single driver of course.  Add 6db for a second driver and another 6db for four drivers.

This is a pretty simple calculation.  Any measured numbers greater indicate either room/boundary gain, measurement error, or drive past Xmax.  Or a combination of those.

Cheers,

Dave.

I use Bassbox 6 pro and this is what I got.   







This is without the considering the OB loss.



Bassbox 6 and many other simulation software did not consider is the amplifier output characteristic with load. For instance, A370PEQ amps under no load condition can output 80V peak. That is 56VRMS.  But at 4ohms, it drops to 40VRMS. At 8ohms, it is about 45VRMS. So the output voltage increases with lighter load. From Klippel, the impedance at 20hz of single SW12-16 is about 27ohms and two of them in parallel is still 13.5ohms which is consider as very light loading. That may add another 1 db or so.

Assume Dave's OB loss value is correct at -19db (20hz). This will be [EDIT]100+1+12-19=94db. The rest will be room gain and how valid the OB loss value is at a particular sitting location. Also there is a peak SPL vs RMS value difference. Basspro 6 uses RMS value. But Audioholic uses peak SPL.  That is another 3db.

[Davey]

The calculation I did doesn't consider amplifier power or output impedance....since those are assumed to be optimal.  (Unlimited and zero respectively.)  You would obviously need the amplifier characteristics for other types of calculations/measurements.

Your A370PEQ specifications indicate an output impedance of 1.6 ohms.  Is that correct?

Cheers,

Dave.

[rythmik]

The output impedance of the amp is lower than that. What I meant was the extra headroom on the amplifier has when it has only 13.5ohm load vs an ideal standard 4ohm loads.

[Rclark]

Brian and Danny, I would love it if you would stop avoiding questions like the ones poised by AJ of Soundfield Audio.

Stop throwing chaff. You like aircraft analogies, there's one for you.

[rythmik]

Brian and Danny, I would love it if you would stop avoiding questions like the ones poised by AJ of Soundfield Audio.

Stop throwing chaff. You like aircraft analogies, there's one for you.

You meant the one with quantum physics?  do you understand quantum physics? Half of AJ wrote is "tongue in the cheeks". You are really serious about that !!!

[Rclark]

Yes exactly, the questions that were framed within that quantum physics post, and others that were conveniently ignored. And don't pretend to now be a quantum physicist either. We have some here, and you don't need that embarrassment.

(FOR EXAMPLE, the resistor question)

[S Clark]

Brian,
I taught physics for years, and I don't get quantum physics....

But all this is really stupid.  Some folks are still pissed off because Danny's V series has the outward appearance of the Orions (althought that's where the similarity ends), others just like to argue.  What does any of this have to do with the original poster's question--- what dipole bass matches with Maggies?  Good grief, 19 pages of this stuff.

Can we simply say that that Brian and Danny's servo's are a very good option, perhaps mention a couple of others, and move on?  AlliumPorrum, the OP, is new here. We haven't made his first experience with AC all that helpful. 

To answer the original question.  The Servo system sold by GR-Research is one of the best out there by dozens of reviews, including mine for the 2011 RMAF.  It is an excellent solution to the original problem.  There may be other solutions that are also good.

[Rclark]

I can't see anyone complaining, especially the new person. I would consider this response to my first post quite spectacular. Brian and Danny, answer the questions.

[S Clark]

I can't see anyone complaining, especially the new person. I would consider this response to my first post quite spectacular. Brian and Danny, answer the questions.

 

[Rclark]

^

said the home team.

[Rclark]

And by the way, "graphs" wise, I'm not seeing anything other drivers can't do.

[dBe]

Yes exactly, the questions that were framed within that quantum physics post, and others that were conveniently ignored. And don't pretend to now be a quantum physicist either. We have some here, and you don't need that embarrassment.

(FOR EXAMPLE, the resistor question)

Yes exactly, the questions that were framed within that quantum physics post, and others that were conveniently ignored. And don't pretend to now be a quantum physicist either. We have some here, and you don't need that embarrassment.

(FOR EXAMPLE, the resistor question)

You really have to know AJ to get some of his posts.  He and I were bitter enemies for years until we met each other and came to understand each other.  Now I consider him a great guy and a worthy opponent/advocate in a discussion of differing points of view.  He will pull someone's chain for sport with more than a little understanding of the topic at hand.  Me?  I've been known to pull the pin on the controversy grenade and roll it into the middle of a room myself.

What is going on here is that there are some people that just don't want to admit that they don't know all there is about situational dependence in discussions.  Probably on both sides.  What we are trying to do is get to the bottom of a controversy that does not need to exist.

Agendas are what they are: we ALL have them.  That in itself is not a bad thing.  It is when we are unable er, .... unwilling to admit this that these things get out of hand.

Dave

[JohnR]

Now now boys, we are getting some good technical discussion here. Even the OP could learn something.

[dBe]

And by the way, "graphs" wise, I'm not seeing anything other drivers can't do.

The big controversy was if an open baffle could produce these kinds of SPL's... in particular the GR Research servo controlled ones.  This WHOLE issue is not about "other drivers".  It is about the GR Research LF modules.

See?

Bedtime.  G'nite...

Dave

[rythmik]

And by the way, "graphs" wise, I'm not seeing anything other drivers can't do.

And by the way, if AJ graphs his crossover in Mills resistor, I am sure you and others cannot see anything other el cheapo cement resistor can't do. 

[Rclark]

You're the one who claimed a dry sound, not him.

[JohnR]

This WHOLE issue is not about "other drivers".  It is about the GR Research LF modules.

Dave, no I don't think so. It was just a question of how OB drivers behave.

[JohnR]

I use Bassbox 6 pro and this is what I got.   

Unibox gives:





It seems fairly comparable, although the excursion is higher (but 18mm at 20 Hz). One discrepancy is that I used 90W to get that excursion, whereas your screenshot seems to show 400W. I used Sd=479.2 as per your Klippel test.

[JohnR]

Here is 35Hz and 40Hz. They are starting to drop off and level out now. Again this is typical for my room. The 25Hz or so peak for my room can be seen. Not a bad place for room gain.    Even allowing for that you can easily see levels over 100db below 30Hz even at 20Hz.

35Hz hit 100db.

Thanks for taking the time to do that.

[JohnR]

John, see Danny's measurements below.  I was wrong on the 18Hz fundamental.  Pete must have pitch shifted it on Deeper to match the key of the song.  The original 808 drop is 18Hz.  When things get this low I can't tell a lot on the ultimate pitch.  I'm very good at nailing peaks in the mids and HF, but this one eluded me.  My bad.  What's a few Hz among frinds anyway.

What's an "808 drop"?

18 to 26 Hz is half an octave. When you have output dropping at 18dB/octave and excursion rising at 12dB/octave, half an octave could be considered significant