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Discussion Starter #1
Kevin or anyone, maybe you can help me......

I'm finishing my boxes - Baltic Birch Ply... Used Neo-Dan's Sealed cut sheet.... (Thanks as always Dan)

My question, will 3/4" ply wrapped with grill cloth be enough distance with the driver recessed 3/4" to cover it without it being interfered with by the driver...?
I still have to veneer the boxes, going magnetic under the veneer, and granite tops each. Need to finalize magnetic grill design before I do veneer.


Thanks

Patrick
 

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To be honest I don't know. I've not built a grill for the driver and while I can make an educated guess it is probably best to mock something up and give it is try at high excursion to see how it works before doing a substantial amount of work. The surround sticks out proud and if you powered the driver out to 30mm one-way (takes a LOT of power) you obviously will be hitting the grill. That is a LOT of output though so what is theoretical and what is practical are often two different things.

Kevin Haskins
Exodus Audio
 

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I can do it with the F1200 bridged in free-air. You hit the suspension limits before it clanks against the back plate. If you put it in a box the power requirements to hit limits goes up, sometimes substantially. You can still equalize it into an excursion limit but it requires a lot of power. You will likely get into thermal limits if you are pushing that much power into the driver. There is only so much power that a 3" VC can handle.

Note... read my power handling Sticky. People who smoke drivers thermally are typically doing it with continuous test signals running higher frequency stuff at significant power. The voice coil/former dissipates heat primarily by convective heat loss to the environment. Once that coil doesn't have a steady stream of cool air moving over it you significantly change the power handling of the device.

Kevin Haskins
Exodus Audio
 

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Patrick,
I'd go ahead and go 2" clearance on the grill, from the baffle. That ought to clear things even if you do get the excursion into the outer limits.
 

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Discussion Starter #6
Well my room is 8200^3 on the very light side, so I'll be pushin these guys...
I think I'm going to shoot for 1 1/2" for starters to see how it pans out on a test run...

Looking for Willd to show up here with hopefully some quick measurements of excursion with the driver under duress... :D
I'm pretty much at a stand still with the Mal-X boxes until the drivers show up.... And I still have 2 more boxes to build for my other TC-2K's, I hate sittin around... :D
 

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It will start well before that. That is a TON of excursion. From experience we have learned to bring things in for a soft landing by having the suspension tighten up as you reach the limits.

The surround is a 38mm roll but we design the overall suspension to start getting progressively stiffer from about 30mm onward. That is by intention so that the system "soft-bottoms" rather than banging the former against the back plate or hitting the triple joint against the top. Due to this you won't get to use all that X-max like some people are calculating. It requires progressively more power as you get out to the limits to push the cone. Your motor starts loosing strength around 25-26mm and is about 30% down at 32-33mm. The suspension is getting progressively tighter too with the Cms about doubling in stiffness @ 35mm. That combination helps protect the driver from mechanically beating itself to death.

Kevin Haskins
Exodus Audio
 

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Never even thought about that. I guess the models are made with 100% BL and perfectly linear suspension which is 2 factors against being able to get those huge cone excursion figures.
 

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Never even thought about that. I guess the models are made with 100% BL and perfectly linear suspension which is 2 factors against being able to get those huge cone excursion figures.
Yea... the models are purely low-level representations. They also don't take into account power compression which raises the DCR drastically as the voice coil heats. You get significant compression effects at the limits of a driver. It doesn't make a lot of sense to drive it right up to it's limit. You are better off trying to utilize about 80% of it's ability and power limiting the system. If you need more output, use more drivers.

The game of seeing how much you can get out of a given device is great fun if your willing to pay for failed drivers. :) OEM systems certainly have an advantage in terms of testing. They tend to build in limiters and power limit subs. As a DIYer you have to overdesign the system and build it for more output than you need.

Kevin Haskins
Exodus Audio
 

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It will start well before that. That is a TON of excursion. From experience we have learned to bring things in for a soft landing by having the suspension tighten up as you reach the limits.

The surround is a 38mm roll but we design the overall suspension to start getting progressively stiffer from about 30mm onward. That is by intention so that the system "soft-bottoms" rather than banging the former against the back plate or hitting the triple joint against the top. Due to this you won't get to use all that X-max like some people are calculating. It requires progressively more power as you get out to the limits to push the cone. Your motor starts loosing strength around 25-26mm and is about 30% down at 32-33mm. The suspension is getting progressively tighter too with the Cms about doubling in stiffness @ 35mm. That combination helps protect the driver from mechanically beating itself to death.

Kevin Haskins
Exodus Audio

:TThat's the best way to do it IMHP. That way when the surround distortion sets in the driver also starts to let you know "hey...I'm running out of gas here" and you can kick things down a notch. Some drivers just kind of slam into the back plate abruptly and real damage can result.
 

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I think 1.5in would be a good starting point, and maybe 1.75" just to be safe. With a 3/4" countersink the surround already sticks out about 1/4", so I'd want to account for around 30mm of excursion beyond that (even though I doubt you'd go that far very often...).
 

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Too bad the suspension couldn't let her rip %100 to 33mm, then resist hard right after that, so achieving full Xmax is as easy as could be, yet it still self protects from there on up...

ah, life would be to easy
 

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Too bad the suspension couldn't let her rip %100 to 33mm, then resist hard right after that, so achieving full Xmax is as easy as could be, yet it still self protects from there on up...

ah, life would be to easy
You have to keep some perspective. This is stuff you balance with all drivers. You don't have suspensions that don't stiffen at the limits. There is no such thing as linearity out to 33mm one-way on any driver.

Also... look at the difference in output and the power required to use stroke out at 30+ mm one-way. You are getting worked up over meaningless specifications when you are commiserating over a couple mm one way or the other.

Kevin Haskins
Exodus Audio
 

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Discussion Starter #15
I think 1.5in would be a good starting point, and maybe 1.75" just to be safe. With a 3/4" countersink the surround already sticks out about 1/4", so I'd want to account for around 30mm of excursion beyond that (even though I doubt you'd go that far very often...).

Thanks Willd, I appreciate you taking the time to stop by here with some measurements.....

30 millimeters = 1.18110236 inch plus 1/4" is close but I'll make my first grill with 1 1/2" and see how it plays out, if it starts to be an issue I can always go bigger... :)

Worse comes to worse, my grills fly off and alert those around that my drivers are putting in overtime...:T
As if your gunna hear the grills hit the floor at that time anyways.... HHAAHAHH :scratch:
 

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also... Look at the difference in output and the power required to use stroke out at 30+ mm one-way. You are getting worked up over meaningless specifications when you are commiserating over a couple mm one way or the other.

Kevin haskins
exodus audio
makes me wonder about the 06' xxx

somebody gives them 3,000 watts free-air from 30hz up lol
 
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