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Multi-Way Conventional loudspeakers with crossovers

Discussion arising from Geddes loudspeaker
Discussion arising from Geddes loudspeaker
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Old 23rd April 2008, 10:45 PM   #181
gedlee is offline gedlee  United States
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Quote:
Originally posted by MJL21193


Hmm,
There is a big difference between "doing everything that can be done" and "doing everything as effectively and efficiently as possible".

I detect a hint of snobbery in the above quote. That's to be expected of course.

Funny, I know quite a few engineers. I can actually fill a fair size room with the P.Eng's I know. They have this in common: they don't talk down to me or use a derisive tone when they refer to this "hobbyist".
I even know a few structural engineers, real structural engineers, you know, the ones that design structures? Well paid individuals, with the responsibility of peoples lives resting on their work. They don't last long in the position by doing what is merely "adequate"

You know I didn't mean anything derogatory by my post, I was basically quoting what you said some frames back about doing all you can. ("Why check one and not the other? Better to be sure and cover both") And there is nothing wrong with being a hobbiest.

But your post is clearly intentionally insulting ...
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Old 23rd April 2008, 11:03 PM   #182
MJL21193 is offline MJL21193  Canada
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Quote:
Originally posted by Cal Weldon

Add to that those who get their degrees from the back of a cereal box who tend to under design in the name of the bottom line. I'll tell you it's no fun reviewing drawings that have critical omissions that no one caught until the building collapsed. Silly engineering mistakes that cost lives. You may be right about some but you sure can't lump them all together.

Sorry for the OT but it's a sensitive subject for me.

We now return you to your regularly scheduled program...
Hi Cal,
This thread was supposed to be about MDF anyway, so everything lately is OT.

The structural engineers that I have met didn't get their degree off the back of a cereal box, that's for sure. Tons of civil engineers yes (I call them train engineers? Choo-choooo).
Structural is the top of the heap, and rightfully so.
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Old 23rd April 2008, 11:06 PM   #183
metalman is offline metalman  Canada
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Quote:
Originally posted by MJL21193
Thank you, although something is still not clear. I'm not saying there should be more bracing , I'm saying the bracing can be more effective. That's the real difference between the full panel and the pole - effectiveness.

I like this one very much! It has the Gothic Maltese cross thing happening, so it get extra points for looking cool.

I whipped up a few quickly also, just for illustration. The one on the far right is my favourite.
Thanks for the "cool factor" vote. I hadn't intentionally done that, but sometimes form follows function nicely.

Also, I don't think we are as far apart as you might think, as I would agree that your "far right" drawing would indeed be a very effective brace, and illustrates the points I was not so clearly making.

In my drawing of the bracing for the speaker cabinet I recently built, if I hadn't used 1" baltic birch plywood for the 7" wide front and rear panels, I would have used a brace more like the one you have drawn. An interesting note about the bracing scheme I did use, is that the cross panel posts are not centered but are positioned at 0.618x cabinet depth, and are alternating in orientation with vertical position. This creates a very minor but measureable difference in the resonance spectrum of the cabinet: the number of resonant frequencies is increased, but the instensity of each spectrum peak is reduced, and each peak is broadened across a larger frequency range. I know, this is "Golden Ratio" hocus pocus, but it did create a beneficial effect without increasing the effort or materials required to produce it.

Quote:
Originally posted by Cal Weldon
Not looking to nit pick but when they go beyond the call they have budget overruns and henceforth often do only what is adequate or acceptable. Add to that those who get their degrees from the back of a cereal box who tend to under design in the name of the bottom line. I'll tell you it's no fun reviewing drawings that have critical omissions that no one caught until the building collapsed. Silly engineering mistakes that cost lives. You may be right about some but you sure can't lump them all together.
The eternal bane of engineers, and the reason why most go grey early in life. It must absolutely positively present no hazard to llife, health, environment, etc., etc., but must not cost one penny more than is possible, and must never, ever go overschedule. Oh, yeah, you also get paid like crap for the stress and demands of the job. This is sadly one of the reasons why I have ended up in the business end of big industry and only do a marginal amount of engineering work anymore (although I still work with engineers on a daily basis). I get paid way more for being in a significantly less demanding position.

Cal, I'll fire you a PM so we can catch up.

Cheers,
Terry
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Old 23rd April 2008, 11:26 PM   #184
MJL21193 is offline MJL21193  Canada
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Quote:
Originally posted by gedlee



You know I didn't mean anything derogatory by my post, I was basically quoting what you said some frames back about doing all you can. ("Why check one and not the other? Better to be sure and cover both") And there is nothing wrong with being a hobbiest.

But your post is clearly intentionally insulting ...

Well I accomplished one thing: I broke the silent treatment you were giving me.

I'm sorry if I read something into your post that wasn't there. No harm done? I don't hold grudges. (22 years in construction will beat that out of you; I'd hate everyone by now ).

Honestly, no insult implied. I was only picking up on a tone that wasn't there.
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Old 23rd April 2008, 11:54 PM   #185
gedlee is offline gedlee  United States
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Quote:
Originally posted by MJL21193



Well I accomplished one thing: I broke the silent treatment you were giving me.


I was never ignoring you, it just seemed that your mind was made up.

Quote:
Honestly, no insult implied. I was only picking up on a tone that wasn't there.
This cannot accept because the insults were more than implied they were blatant and deliberate. You need to be more polite. I will ignore you if this is not the case.

The point that seems to get missed by many here, that I may not have made clear, is that when I say to use a rod across the cabinet I have assumed that the corners are well glued and don't bend. As I am sure Terry will confirm, this makes a huge difference since a plate clamped at the edges will respond much better to a pinned center than a free edge (or hinged) plate. And it is plates that we are talking about here, not membranes - there is a very large difference in the two. The rod idea has very little effect on a membrane but a very large effect on a clamped plate.

Of course more rods would work even better and enough rods to make a plate even better yet, but for efficiency you get the most bang from the first rod and they become progressively less effective after that.

And the diference in acoustic radiation efficiency has been completely ignored in this discussion, but it is no insignificant effect. Some vibrations radiate far better than others - basically the closer to a monpole the better the radiation. The single rod (in three directions) concept basically kills any monopole motion of the enclosure thus being by far the most effective (for a minimum of rods) at reducing SOUND radiation.
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Old 24th April 2008, 12:16 AM   #186
MJL21193 is offline MJL21193  Canada
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Quote:
Originally posted by gedlee


I was never ignoring you, it just seemed that your mind was made up.

My mind is made up. That hasn't changed.


Quote:
Originally posted by gedlee

This cannot accept because the insults were more than implied they were blatant and deliberate. You need to be more polite. I will ignore you if this is not the case.

That was me being courteous. You will have to take it whatever way you like.
I can be polite, but who started this ball rolling back in post#125?
I only give it when I get it.

As for threats about ignoring me...well I'll have to try to cope with that the best I can.
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Old 24th April 2008, 12:24 AM   #187
MJL21193 is offline MJL21193  Canada
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Quote:
Originally posted by metalman


Thanks for the "cool factor" vote. I hadn't intentionally done that, but sometimes form follows function nicely.

Hi Terry,
I took liberties with your brace and hacked a few holes to make it more "airy" and "transparent". Hope you don't mind.

The first one is redone on Sheldon's very "sound" advise: to straighten the curved pieces. This would be a great brace for a mid-sized box, where the other would provide brute strength for a sub enclosure - a man of a brace.
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Old 24th April 2008, 01:27 AM   #188
gedlee is offline gedlee  United States
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Lets all try and be nice OK!! There is absolutely no excuse for being rude.
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Old 24th April 2008, 01:33 AM   #189
MJL21193 is offline MJL21193  Canada
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Quote:
Originally posted by tinitus
MJL... your fine suggestions/drawings of bracing reveals that your expertice is a complete fantacy...doesnt look like you actually know what you are doing...I only say this because you claim to be an expert, which you obviously are not

Hi,
Where did I claim to be an expert?


PS: There are many more things I could say, but I won't.
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Old 24th April 2008, 01:40 AM   #190
MJL21193 is offline MJL21193  Canada
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Quote:
Originally posted by gedlee
Lets all try and be nice OK!! There is absolutely no excuse for being rude.

Yes. This thread will be closed and we'll all be doing a stint in the sin bin if cooler heads don't prevail.

We can discuss things without one oneupmanship.
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