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In the Forum: Melquiades Amplifier
In the Thread: Planning my DSET
Post Subject: I deserved thatPosted by anthony on: 3/3/2019
 Romy the Cat wrote:
Well, it might sound as a heresy to you, but I personally consider the impedance curve is a bit irrelevant in this application. In this application you need to care only about only 2 things: if you have enough power in you LF DSET to drive your line array and the character of sound in LF. If I was you I would keep lowering damping, more and more idling the LF output stage until you will be in danger the amp approaching clipping. They relies the damping a bit if you feel that you get too SS type of bass or THEN play with plate current to fine tune the damping.
 

No, not heresy at all.

The impedance plot is important from the perspective that the Cannons are an unusual shape and prone to ringing because of that shape, which shows up in the impedance plot as well as when listening to them.  The ringing is gone, and I managed that by observing the impedance plot and listening to them at the prototype stage.  Nowadays, in the absence of outdoor SPL measurements to check frequency response the impedance info is the best available indicator of frequency response and other abberations because I am not pulling down a stack and taking the whole system outside just to measure the free-air response of the speakers...there is no need for that.

I will play with damping the 6C33C when the system is a little more mature.
  
 Romy the Cat wrote:
  
The frequency response is another matter. You need one channel, no time-window and the mike in the exact listening position. I presume that your amps the drive bass has no filters. Your upperbass in your room might be running down to 100-120Hz. The 42Hz is not a problem at all. The problem as I see it is in the 65Hz suck out, but do not worry there are many ways to deal with it.  


That SPL curve and the one that I include below is the entire left side Bass Cannon driven by Channel A of my DSET, no other drivers are connected.  At 1r nominal impedance I cannot drive it with any other channel or even my SS amps.  A first order, 60Hz low pass filter is included.  Mic is at the exact listening position

In the graph below you will see two lines:  blue is the empty room; brown/yellow is with the addition of two bags of polyester wall insulation (still in the bag) sitting in the corner behind the Bass Cannon being driven.

SPL Greenstuf 2 bags.jpg

...the 65Hz hole is more or less gone.  I think that upperbass hole can be filled reasonably well just with a little more room treatment.  The 40-55Hz stuff a little less easy but hopefully it will come together without too much effort with room treatment.

 Romy the Cat wrote:
 What I would like to do is to give me the individual swipe the topmost driver in the LF array and the lowest. They must have a deferent repose and I would like to learn the difference. 
  
We will need the sweep for the other channel and the summation of the R and L channels. What filter you built in into the Milq’s Chenal A? Are you drive the bass now from the Milq’s full range channel? If yes then the Milq’s full range channel and A channel have VERY deferent damping characteristics… 
 


I can give you the response of the top and bottom driver of the Cannons.  It is a fair bit of messing around not to unwire and measure but to wire the things back up...I have not left enough room for my fingers to easily get to the bolt, and wiring it up the first time took half and hour.

The rest of that stuff will need me to finish the second DSET and hook it up.  That will be a couple of weeks.

 Romy the Cat wrote:

PS: Man, you need to play better music with your playback. I am serious, it is very discouraging to hear you play crap music. Please if you want me not to be demoralized then fake better music interest in your videos.


Yeah, sorry.  It is a song from my childhood that I really loved at the time [and still do].  I am late to classical music...my parents are both country kinds of people but Mum still listens to a lot of older pop and a bit of jazz.  Would you believe that my interest in classical was seeded by very late night driving in my 20's where I would leave where I was working and drive 4 hours home through the rough and winding and almost non-populated hills and get in around midnight?  I would purposefully leave at about 8pm because that was when the friday night concert started on ABC Classic FM and it was listening to symphonic music in particular that kept me awake...complete engagement for hours and the trip was gone in the blink of an eye.

It has only grown from there.  If you have any suggestions for music please let me know.  I was thinking some Heifetz/Max Bruch Violin Concerto 1 that I discovered from the same FM station in my late 30's. 


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