Planar Speaker Asylum

Welcome! Need support, you got it. Or share your ideas and experiences.

Return to Planar Speaker Asylum

Planar Speaker Asylum

RE: total speculation. nt

71.138.52.177

In Reply to: RE: total speculation. nt posted by Davey on August 25, 2010 at 17:05:14

Let me see if I've got this straight........
You have a theory and I have speculation?

My long gone Dual 1209 TT had a 2 piece platter, Pretty dead when given the thump test.
Each half would individually ring pretty good.

Also, as the mass of something goes up, the resonant frequency drops, in general. My theory calls for a light, rigid, one-piece frame. No metal bridgework, either, and all fasteners will be either SS or Brass. Maybe Brass, preferred.

As for bridgework stand designs, I'd be tempted to TRY thin-wall tubing. Fabricate Wooden plugs with threaded inserts to interface with other parts. It's not like the stand is under much stress. I'd also test Aluminum tubing. While I dislike Aluminum for personal reasons, that it is so 'dull', having no fatigue strength and responding poorly to elongation and some other things, at least, as the reasoning goes, You've never seen an Aluminum Bell.

The panel....for the 1.6, anyway has an impedance peak at 600hz. I'll look at the rest of the data and see if a resonance exists. Total frame would ideally be tuned to 'suck out' that frequency and flatten output. Just thinking in print.

It is just my opinion, for now, that the lightest frame of the single sided variety will have good characteristics. I am working on a way to NOT use screws to hold the driver to the frame since I don't want to drill holes in it.

When I have everything taken apart, I'll 'feel around' and try to determine just how much additional sound is produced by other parts of the panel. If everything is a rigid unit, however, the vibes should be 'grounded'. A driver, secured to a low mass frame should have minimal impedance mis-match. I hope.
Too much is never enough

Follow Ups:

RE: total speculation. nt - Davey 20:39:10 08/25/10 (4)
The sandwich construction won't change the resonant behavior of the transducer at all. (At least not in the way I think you're thinking about it.) I've measured it.
I think maybe you're missing the objective of what the hardwood frames are trying to accomplish.
However, you are correct it will weigh more.....double the wood. But that's a good thing....IMHO.
The 1.6 (panel) doesn't have an impedance peak at 600Hz. Both elements are flat impedance through that range. The 1.6 'crossover' is what creates the 600Hz impedance peak.
A single-sided panel without screws and screw holes through the xducer should be possible. I considered that.....and am still considering it.
Cheers,
Dave.

Edits: 08/25/10
- RE: total speculation. nt - pictureguy 21:13:25 08/25/10 (3)
  I want to look at the Stereophile test 'measured data' panel. For the ENTIRE speaker, driver/crossover ..... there is an impedance peak at crossover..... I have no idea how the bare driver will behave. The interaction with the frame is probably not trivial.
  
  That's why I issued a call for data, rather than more speculation. So far, the PG model makes the most sense to me, but I need to get to 'root cause' and figure out which knobs to turn to get a response.
  
  I don't know about frequency peaks....I just remember that impedance peak. I'll look again at that data. I think I linked it here...in one of these threads last week sometime.
  
  Treating the entire panel/ frame as a system, more mass will translate into a lower resonant frequency. IF the driver is coupled firmly to the frame. Things change radically when something is put between driver and frame.
  Too much is never enough
  - RE: total speculation. nt - pictureguy 09:41:11 08/26/10 (0)
    link again, to the Stereophile measurements panel from ....late 90s.
    
    Big impedance peak at crossover.
    
    Also, big response peak in the octave between 50 and 100 hz. While stereophile says not to worry, due to dipole cancelation, that vibration is still transmitted to the frame and must be dealt with.
    
    Still, just a thought, but the reason I'm leaning toward a lighter 'live' frame.
    Too much is never enough
    - http://stereophile.com/floorloudspeakers/595/index6.html (Open in New Window)
  - RE: total speculation. nt - Davey 06:41:10 08/26/10 (1)
    I kind of feel like I'm talking to a wall. :)
    I'm speaking from measurement experience here. I'm not speculating. :)
    
    Anyways, I have some data already from my sandwiched (and stock) MMG panels, but why don't you tell me what you'd like to see and if I don't have it I'll see what I can do.
    
    Cheers,
    
    Dave.
    - RE: total speculation. nt - pictureguy 09:31:28 08/26/10 (0)
      Data needed? hmmmmm
      This would be cost-no-object, wishful thinking type data.
      accelerometer data. several frequencies from say.....35hz to 400hz....something in that range.
      Single frequencies used, to find resonant modes. Crossover? Leave that out of it at first. Check for differences between pole piece front and back. Do frequency response sweeps and impulse tests across 30 or 40 degrees in front of the panel.
      Do such tests for stock panels.....and at several levels of mod and for different designs of the same or similar mod. Nobody has the time, money or resources to do this! Obviously.
      
      On the practical side, I don't know what the minimum would be to tell differences between different panels and mods. I suggested the MASS (weight, sorta) of panels effects the resonance and vibration properties. This was not received well. But it is just what people 'think', not what they know. I don't know, either, but seems reasonable. When someone added that metal to the back, what effect did he really have? More stiffness? Sure weighed a lot more. Need to try to separate out these various thoughts.
      
      Look at this from someone just walking in viewpoint. There are 3 or 4, maybe more, theories and courses of action to help panels perform better. All agree that vibration is key. Some talk about absorbing vibration, others coupling to ground. Others use sandwich construction while others dampen. Some clamp while others say, not to! Metal stands? Stiffening? Real Wood? Dynamat? BlueTac? Balsa Wood? This list goes on. Some theorists seem to have trouble telling the difference between the different effects. I can understand this problem.....Looking at the whole thing, it is pretty complex.
      
      My personal model is single sided, lightweight wood. I want it to have the highest resonant frequency possible consistent with high stiffness. No metal in the load bearing part of any stand. I have other features in mind, as well, which I have not seen discussed and are known in the 'rest' of the speaker world, so are not revolutionary. NO damping material will be applied at first, if ever, and the pole pieces will face the listener. Crossover will remain stock, but be located to an external box. Crossover helps will come down the pipe at a later date. The driver will be in very firm contact with the wood but have no holes drilled.
      
      All the theories simply can't be right. Some even conflict with one another...which is what sets me off. A proper theory can be used to PREDICT. So if you theorize 'X', than 'Y' and 'Z' should also occur. If you don't observe what you predict based on your theory, you need to think it thru again. i don't have funds, time or facilities to do what I intend more than once. I'm taking a woodworking class right now up at the JC and hope to start on my frames next year at this time.
      Too much is never enough

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors:

Parts Connexion