AVS Forum banner

2641 - 2660 of 2759 Posts

·
Registered
Joined
·
1,487 Posts
You must have misunderstood me. Why is 1 port firing up and 1 port firing forward?

Why not both ports firing up or both ports firing forward?
 

·
Registered
Joined
·
2,383 Posts
Discussion Starter · #2,642 ·
You must have misunderstood me. Why is 1 port firing up and 1 port firing forward?

Why not both ports firing up or both ports firing forward?
Ideally both mouths would fire forward and I get a 40"+ straight vent. That box is basically the FV1. Particles help with TR, this is a compromise on that. You get the HF resonator particles and lose the LF particles for the straight vent. The straight vent will do better on port noise and compression. The vent frequencies are very low, not too worried about mutual coupling. The sound will have no difficulty wrapping around the enclosure. You need a massive manifold in this frequency range to have an affect on dispersion.
 

·
Registered
Joined
·
2,383 Posts
Discussion Starter · #2,644 ·
Did you duct tape a sub into a pumpkin thing? That’s awesome. Might want another ten layers of tape by the port, or for the production model move to gorilla tape maybe.
I did not create the abomination, I just really like that GIF! R&D is not using pumpkins...
 

·
Registered
Joined
·
238 Posts
@Red Five
I have some general questions:
How much would designs change if you were optimizing for transient response and setting SPL as a far secondary concern?
Does particle velocity directly relate to TR across the frequency range, or does it vary by frequency?

At this point this is a general curiosity type question, however I wouldn't be opposed to building a Proof of Concept if it ever gets that far.

To further that point I don't live THAT far from you so you could even see / experience it in person, and potentially at your house if it isn't terribly large. I only live 17 miles South of the WI border.
Edited again to add: I am thinking of a TR system like what BOSS is doing, but for the skin not attached to the chair. Huge vibrations, but low SPL. I realize very low SPL isn't really practical in this situation compared to BOSS, BOSS is moving your body around, this is still moving air, so it has to have SPL by definition. Also assume port noise is acceptable.
 

·
Registered
Joined
·
2,383 Posts
Discussion Starter · #2,647 ·
@Red Five
I have some general questions:
How much would designs change if you were optimizing for transient response and setting SPL as a far secondary concern?
Does particle velocity directly relate to TR across the frequency range, or does it vary by frequency?

At this point this is a general curiosity type question, however I wouldn't be opposed to building a Proof of Concept if it ever gets that far.

To further that point I don't live THAT far from you so you could even see / experience it in person, and potentially at your house if it isn't terribly large. I only live 17 miles South of the WI border.
Edited again to add: I am thinking of a TR system like what BOSS is doing, but for the skin not attached to the chair. Huge vibrations, but low SPL. I realize very low SPL isn't really practical in this situation compared to BOSS, BOSS is moving your body around, this is still moving air, so it has to have SPL by definition. Also assume port noise is acceptable.
Transient response usually looks better with shorter resonators, the micro 18"s are a good example of this. You can check the impulse response in HR. It is under tools in the acoustical power window. Generally as the horn gets longer you end up with more ringing as the driver tries to return to 0. There is a larger air mass working against the driver in the QW resonator. Stiff suspensions and motors also come into play first an foremost. High mass woofers usually do not fair as well. If you look on the first page of the Index, the UM rings a lot when loaded in a Devastator, but the B&C settles down rather quick.

My basement is terrible for TR. It is very large and very open. For me to get where I want will take at least two beastly subs loaded with NSWs. I have not tinkered with a BOSS yet, only so many hours in a day... The closer you get to the mouths on a Devastator the more particles you will feel. If you really want the particles nearfield is an option.
 

·
Registered
Joined
·
238 Posts
Transient response usually looks better with shorter resonators, the micro 18"s are a good example of this. You can check the impulse response in HR. It is under tools in the acoustical power window. Generally as the horn gets longer you end up with more ringing as the driver tries to return to 0. There is a larger air mass working against the driver in the QW resonator. Stiff suspensions and motors also come into play first an foremost. High mass woofers usually do not fair as well. If you look on the first page of the Index, the UM rings a lot when loaded in a Devastator, but the B&C settles down rather quick.

My basement is terrible for TR. It is very large and very open. For me to get where I want will take at least two beastly subs loaded with NSWs. I have not tinkered with a BOSS yet, only so many hours in a day... The closer you get to the mouths on a Devastator the more particles you will feel. If you really want the particles nearfield is an option.
Ok thanks, I will study the various already published designs to see what I can learn.

A note on the BOSS system. I didn't use any advanced elastomers, mine are floating completely on bike inner tubes. Air in rubber bladders are very good springs. If you have a big flat couch it will be super easy to do, recliners and so forth get a bit harder, but nothing like the builds in this thread. On vibrations, it is roughly equivalent to the pair of quad devastators deep into distortion and 10 feet away, effectively the craziest I have felt them, and the BOSS does that easily. It is the other side of my body of course. My BOSS setup is just a pair of cheap JBL 12's driven by an Adcom 555 because I had it.
 

·
Registered
Joined
·
23 Posts
Putting the vent on the back wall assuming the cabinet lays on the side and having that vent exit what is typically the bottom of the cabinet? I have considered doing that. I am sitting back waiting for data before I push too much more out in the way of designs.
Sorry I didn't back to you sooner. Your later rev is not exactly what I was talking about either. I cobbled together a really (really!) rough sketch showing what I'm talking about. I know it would involve some "interesting" box mods, but I was just curious about how it might work
3116056


Please excuse the extremely rough presentation. I'm terrible at freehand drawing.
 

·
Registered
Joined
·
1,487 Posts
I could see that setup working well If the enclosure is placed in a corner.
 

·
Registered
Joined
·
23 Posts
I could see that setup working well If the enclosure is placed in a corner.
If the ports are aimed towards the corners of the room, the horn slot would be firing directly into the room, toward the MLP. The additional advantage is that the requires only 25 inches of floorspace away from the wall, making it nice for those with smaller rooms. The current Dev 2 DF would use 20% of my room width if oriented as designed
 

·
Registered
Joined
·
2,383 Posts
Discussion Starter · #2,652 ·
Sorry I didn't back to you sooner. Your later rev is not exactly what I was talking about either. I cobbled together a really (really!) rough sketch showing what I'm talking about. I know it would involve some "interesting" box mods, but I was just curious about how it might work
View attachment 3116056

Please excuse the extremely rough presentation. I'm terrible at freehand drawing.
Would a 26" deep box with a 31.5 height work in the space? Running the HF resonator pipe like that will add a lot of parts and complexity to the cabinet.
 

·
Registered
Joined
·
2,383 Posts
Discussion Starter · #2,654 ·
Is there a way to make the BMD Alpha II ports exit on the 26x30" side vs the front?
The port would have to be entirely on the back wall and the HF resonator would have to move to the base of the cabinet. It will be a big of a reach, but you can probably climb in there to mount the woofer!
 

·
Registered
Joined
·
55 Posts
Ran some hornresp models looks like little diff from bmd alpha df shallow so will stick with that version for easy access for the woofer install. Thanks for the write up link was pretty quick to get model comparisons!
 

·
Registered
Joined
·
2,383 Posts
Discussion Starter · #2,656 ·
Ran some hornresp models looks like little diff from bmd alpha df shallow so will stick with that version for easy access for the woofer install. Thanks for the write up link was pretty quick to get model comparisons!
Did you get the S cross sectional numbers to turn red when running the simulation for the Alpha II? I cannot remember if I mentioned double clicking on an S to turn the simulation into stepped mode.
 

·
Registered
Joined
·
55 Posts
I modeled the bmd df shallow with the NSW6021-6 21 driver and looks very similar to v2 so figured close enough for government work!
 

·
Registered
Joined
·
1,487 Posts
If the ports are aimed towards the corners of the room, the horn slot would be firing directly into the room, toward the MLP. The additional advantage is that the requires only 25 inches of floorspace away from the wall, making it nice for those with smaller rooms. The current Dev 2 DF would use 20% of my room width if oriented as designed
I wouldn't even waste the floor space. I would place the enclosure flush into the corner and have the ports visibly firing into the room. Technically, you're still using 2 walls and the floor as boundries (0.5 Pi).
 

·
Registered
Joined
·
238 Posts
If the ports are aimed towards the corners of the room, the horn slot would be firing directly into the room, toward the MLP. The additional advantage is that the requires only 25 inches of floorspace away from the wall, making it nice for those with smaller rooms. The current Dev 2 DF would use 20% of my room width if oriented as designed
This is less relevant if you need/want many of them and are willing to stack them up. You should be able to stack at least 3 in most rooms, and then it becomes a good use of floor space. Don't tell me that no one would ever stack 3 DF Devastators...
 
2641 - 2660 of 2759 Posts
Top