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I have 2 spare um-18's and a plan for a modded full marty cab I might do>16" deep , tuning is 17
but I'd also like to know if I could get a better deal if I put 2 of UXL 18's in a slim Devastator cabhttps://www.avsforum.com/forum/155-diy-speakers-subs/3094240-devastator-index-27.html#post59418164
also 16" deep, tuning is 19 with a BMD 18
but there is a need for a refinement wrt to optimal tune,
those UXL's cost me $400 per from a group buy like 5 years ago
and the Berrry 6K and 2x4HD to "tame" them

and then the issue of making them play nice with the SUBMAXIMUS V3 FLH-
TBD
and thanks to the guys who did their homework and can actually explain all this science in English.
 

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Discussion Starter #242 (Edited)
Going off of concept purely, both will work although less bends the better. But the concept rarely translates to final build, one model has the port spanning 3 walls and your final sim would probably only need it to span 2.
I just wanted to eliminate that helmholtz issue by putting those two bends, otherwise unnecessary, check the below one, removed them.

When contemplating builds you have to understand what the different alignments accomplish, plug and play your driver in those models and simulate them. Take what the simulate says you need; example a port tuned to 23hz and is 2inchx17inch will need to be 28inches long to achive the tuning.
Plus the volume of the chamber right?

The Devestator is your build, the front volume is the volume present directly infront of the driver. The port is the area exiting below it.
You mean the front port (which is above the driver) or the rear...?

Update:
I took a closer look at the Devastator, you're right, mostly the same (enclosure is vertical though).
 

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Discussion Starter #243 (Edited)
The picture at 3:05 shows how to do it w/o bends, which could be modified as shown: View attachment 3095523
I watched 3:05, ports firing in opposite directions (like duplex in networking), good solution (bit awkward-looking though), but my design can easily be altered if bending is the real problem here, see below, it's that simple.

Update:
I have to disagree on your drawing bro, reason is, when placed on the floor (horizontally) the front port is sealed as I could see. :rolleyes:
 

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Discussion Starter #244
I have 2 spare um-18's and a plan for a modded full marty cab I might do>16" deep , tuning is 17
but I'd also like to know if I could get a better deal if I put 2 of UXL 18's in a slim Devastator cabhttps://www.avsforum.com/forum/155-diy-speakers-subs/3094240-devastator-index-27.html#post59418164
also 16" deep, tuning is 19 with a BMD 18
but there is a need for a refinement wrt to optimal tune,
those UXL's cost me $400 per from a group buy like 5 years ago
and the Berrry 6K and 2x4HD to "tame" them

and then the issue of making them play nice with the SUBMAXIMUS V3 FLH-
TBD
and thanks to the guys who did their homework and can actually explain all this science in English.
17hz would be monstrous!

UXL 18 is near audiophile in bass extension, you were lucky to have a pair for 800, usually costs around 1600 (now discontinued I think).

Wow, thumbs-up for 2x4HD...

Yeah, SUBMAXIMUS seems to be a mismatch with DEVASTATOR, mechanisms vary.

Cheers in advance! 🤜🤛
 

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Discussion Starter #246
What do you mean by Helmholz issue?
I guess you already know what helmholtz really is, however, if not, helmholtz is simply the sound as you blow across the top of an empty bottle (back to school days), in acoustics this effect is used to make different notes at different air volumes, but in subs, I doubt this is what you were trying to say about slot ports, am I right...?

That's the top view.
Sorry, it means that one port directs front and the other side. I got another question now, have you thought all my sketches were top views as well as yours...?
 

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I guess you already know what helmholtz really is, however, if not, helmholtz is simply the sound as you blow across the top of an empty bottle (back to school days), in acoustics this effect is used to make different notes at different air volumes, but in subs, I doubt this is what you were trying to say about slot ports, am I right...?
Yes, I do, and (maybe) you do.

It seems like every time I ask you about a questionable or fuzzy statement, you say something unrelated and/or ask another question.

If you keep doing that I won't respond.

So what Helmholz issue are you referring to?


Sorry, it means that one port directs front and the other side. I got another question now, have you thought all my sketches were top views as well as yours...?

I didn't consider what the orientation was, just as schematic representations of port layout.
 

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Discussion Starter #248
Yes, I do, and (maybe) you do.

It seems like every time I ask you about a questionable or fuzzy statement, you say something unrelated and/or ask another question.

If you keep doing that I won't respond.

So what Helmholz issue are you referring to?
I'm sorry but it was your misunderstanding bro, I wasn't arguing with you on anything, I'm not that stupid to argue with anyone on a subject I really don't know, but I still don't understand what you tried to mean by "air slamming into a wall" in a previous reply (long ago), so I thought you were referring to that "helmholtz" thing, however, I don't know any of these, I'd be pleased if you'd kindly explain me further about that "air slamming", I'm still confused cos I'm gonna be the listener at last... :)

I didn't consider what the orientation was, just as schematic representations of port layout.
👍
 

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I still don't understand what you tried to mean by "air slamming into a wall"
I thought that was obvious, but fair enough.

The air is traveling at high velocity down the port tube. It's inertia makes it unable to turn 90 deg so quickly, so instead of going around the corner smoothly, a lot of it will hit the wall at the end.

It will suddenly reach zero velocity, some of even bouncing backwards to have negative velocity.

Now it has to be reacceleratred by the air behind it.

Overall, it creates turbulence and restricts overall flow, reducing port output.
 

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Discussion Starter #250 (Edited)
I thought that was obvious, but fair enough.

The air is traveling at high velocity down the port tube. It's inertia makes it unable to turn 90 deg so quickly, so instead of going around the corner smoothly, a lot of it will hit the wall at the end.

It will suddenly reach zero velocity, some of even bouncing backwards to have negative velocity.

Now it has to be reacceleratred by the air behind it.

Overall, it creates turbulence and restricts overall flow, reducing port output.
Alright, I was just thinking about this phenomenon bro, it's easily understandable in practice, a sudden 90° drift will dissipate air mass, as a result some air will reflect back, it means no bends is better, so this one finally wins right (or the spots marked in red still make 90s, if yes then shortening the ports like in the next one will fix it)?

BTW, can this not be something related to "helmholz" as well (just asking)...?
 

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Right, the points at the red circles are problematic.

The one w/shorter ports is much better.

Not sure how much better it would be, but if it was me I might still put in some corner deflectors, depending on the actual distance from the end of the port to the wall.
 

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Discussion Starter #252
Right, the points at the red circles are problematic.

The one w/shorter ports is much better.

Not sure how much better it would be, but if it was me I might still put in some corner deflectors, depending on the actual distance from the end of the port to the wall.
Thanks bro, I just wanted to figure that out... :giggle:

Update:
I'd have to make the decision, slot or round.
 

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Discussion Starter #253 (Edited)
@Trimlock

Bro, just gotta ask, referring back to your graphs B&C 12" and 18" you tested hit 22hz and 20hz respectively, how in decibels (SPL) was that...?

Update:

I believe this one would be simpler as you (& @noah katz) mentioned lesser the 90s better the resp.

I prefer high-pass @50 & low-pass @20 in port tuning, cab volume doesn't matter for me, possible (with 12TBX100)...?
 

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Discussion Starter #254
Can anyone of you please explain this in the meantime?

I was asked this by a friend of mine who's a DJ in profession, gotta know I'm gonna amp 1k for my 2 subs (changed mind to make it 2 with 2 TBX100s), he told me 2k amp he owns can full-power 2 STX818Ss inside of a 60*60 party hall shaking the crowd, then why 1k for my 20*20, I know big watts need at low notes (and sensitivity of the speaker is another thing in which less watts more decibels), but amping in kilowatts for a LIVING room, would that be a LIVEABLE ambiance...???
 

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Can anyone of you please explain this in the meantime?

I was asked this by a friend of mine who's a DJ in profession, gotta know I'm gonna amp 1k for my 2 subs (changed mind to make it 2 with 2 TBX100s), he told me 2k amp he owns can full-power 2 STX818Ss inside of a 60*60 party hall shaking the crowd, then why 1k for my 20*20, I know big watts need at low notes (and sensitivity of the speaker is another thing in which less watts more decibels), but amping in kilowatts for a LIVING room, would that be a LIVEABLE ambiance...???
Overly simplistic answer - Your DJ friend isn't playing 20hz, or even 30hz. (The STX818S is -10dB at 35hz)
Also - He's playing at a more or less constant level, so there's little dynamics involved, and he's not playing them at 115dB.
 

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Discussion Starter #256
Overly simplistic answer - Your DJ friend isn't playing 20hz, or even 30hz. (The STX818S is -10dB at 35hz)
Also - He's playing at a more or less constant level, so there's little dynamics involved, and he's not playing them at 115dB.
I just wanted to confirm this, loads of power consuming at the 20-30 region, fair enough.
 
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