Infinity Primus 362 Modification?

[lmt9914]

I'm looking at getting a pair of Primus 362's and trying to mod them. Has anyone here done some of the mods mentioned on these specific speakers?
Thanks!

 

[adwilk]

Have you read this thread?

 

[JerryLove]

I'm running a pair of modifird Primus 362s now:
http://forums.audioholics.com/forums/showthread.php?t=56392&highlight=primus
http://forums.audioholics.com/forums/showthread.php?t=59483&highlight=primus

also (not mine)
http://forums.audioholics.com/forums/showthread.php?t=46286&highlight=primus

I'll put up something of a review of the results when I get around to it.

 

[lmt9914]

Thanks Adwilk for the link. Thanks Jerry for the links and photo.
Those look pretty awesome! Way more modded than what I was thinking.
Anybody else?

 

[sholling]

Thanks Adwilk for the link. Thanks Jerry for the links and photo.
Those look pretty awesome! Way more modded than what I was thinking.
Anybody else?

Not looking for the million dollar mods? I'm betting that they sound great but I'm guessing that it's also way out of my price and skill range,

I think there is a thread someplace where WmAx suggested replacing the P362's speaker stuffing with something better and more of it. He made a similar recommendation for Behringer B2030Ps but what I have not been able to do is find a source for his recommended materials. Google was useless. Without that information I've just been trying out different materials in my B2030Ps and so far I'm pleased with the results but I think I can do a bit better. My next experimental material is fairly high-buck at $5sqft and will be here Monday.

 

[lmt9914]

Not looking for the million dollar mods? I'm betting that they sound great but I'm guessing that it's also way out of my price and skill range,

I think there is a thread someplace where WmAx suggested replacing the P362's speaker stuffing with something better and more of it. He made a similar recommendation for Behringer B2030Ps but what I have not been able to do is find a source for his recommended materials. Google was useless. Without that information I've just been trying out different materials in my B2030Ps and so far I'm pleased with the results but I think I can do a bit better. My next experimental material is fairly high-buck at $5sqft and will be here Monday.

Yeah Sholling, I am not looking for a huge mod but I wonder if I can just incorporate the horizontal bracing along with Wmax's suggestions and get a pretty good result. If I can get them cheap, I can afford to turn them into a garage project.

 

[Alex2507]

The Owens Corning 703 or 705 can be found by bugging HVAC companies in your area. That's the 3 or 6 lb/ft^3 rigid fiber glass material. The mineral fiber equivalent is 6 or 8 lb/ft^3 which is cheaper but just gnarly to work with and doesn't like being handled overly much.

I think it was nibhaz that found like 5 different sources of it in adk's area with a search. PM nibhaz for tips on finding it.

Additional bracing may best be accomplished with Rickster71's all-thread trick. I don't think I would use hockey pucks like he did but rather a couple of neary full width braces with holes drilled in them for a piece of all-thread at the 1/3 and 2/3 points to be snugged up with nuts and washers and then glued. This would allow for square pieces of Peal&Seal and insulation to follow. There's not a lot of room to work through the speaker holes so be prepared to be frustrated.

Gluing up those magnetic shields, adding insulation to the bottom of the cabinet and to the midrange housing are the quick, easy and effective parts. I don't know why but I hate wrapping insulation with fabric ... probably because I'm not an upholsterer. The Peal&Seal thing is very time consuming but not doing it while your in there would definitely be opportunity lost.

 

[sholling]

The Owens Corning 703 or 705 can be found by bugging HVAC companies in your area. That's the 3 or 6 lb/ft^3 rigid fiber glass material. The mineral fiber equivalent is 6 or 8 lb/ft^3 which is cheaper but just gnarly to work with and doesn't like being handled overly much.

I'm wondering if anybody has tried high density sound absorbent open cell foam? It looks like it would be easy to work with but I have no idea how well it would work. I've used it for soundproofing and for isolation pads.

 

[Alex2507]

I'm wondering if anybody has tried high density sound absorbent open cell foam? It looks like it would be easy to work with but I have no idea how well it would work. I've used it for soundproofing and for isolation pads.

I'm pretty sure that the NRC's (Noise Reduction Coefficients) of foam can't even begin to touch those of rigid fiber glass. This question in the room acoustics forum would get the likes of bpape and Glen Kuras answering in a much brainier fashion.

 

[lmt9914]

Thanks for the info Alex! I can get my hands on the rigid fiberglass material pretty easily. I am a sales manager for an HVAC company.
Alex you mentioned a trick thread by Rickster71 so I will look around for it if I have some time later. You also mentioned "full width braces with holes drilled in them for a piece of all-thread at the 1/3 and 2/3 points to be snugged up with nuts and washers and then glued" . I am having a hard time visualizing this.
Would I be able to place the braces in without drilling straight through the cabinet?
Regardless, thanks for all your help and direction guys!

Mike

 

[sholling]

I'm pretty sure that the NRC's (Noise Reduction Coefficients) of foam can't even begin to touch those of rigid fiber glass. This question in the room acoustics forum would get the likes of bpape and Glen Kuras answering in a much brainier fashion.

Okay thanks. I use the 2" thick 4.5lbcuft stuff to soundproof my bedroom window and it does a remarkable job. It's saved the life of the barkomatic dog living behind me for the last 3 years. I can't even hear the mutt now. I also stuffed it into the windows next to my speakers so I can blast my speakers a bit louder at night.

 

[Alex2507]

Okay thanks. I use the 2" thick 4.5lbcuft stuff to soundproof my bedroom window and it does a remarkable job. It's saved the life of the barkomatic dog living behind me for the last 3 years. I can't even hear the mutt now. I also stuffed it into the windows next to my speakers so I can blast my speakers a bit louder at night.

Okay. It seems that you're interested in reducing sound transmission as opposed to sound reflection and those are definitely two different things. Your case is uniquue to anything I have read about because it doesn't involve a normal stud wall with a cavity that can be filled but the product you bought must come with spec's for product submittal.

Google this:

Submittal Sheet Fiberglas® 700 Series Insulations

It gives you some of the info that would be pertinent in using the 703 and 705 for speaker dampening and acoustic panels but some of the test numbers look a little skewed. Reducing sound transmission in a typical wall cavity is something I have read stuff on but it's not like I'm a guru ... just a mildly interested bored guy.

Glad to hear that you and the dog have made it this far. A friend of mine way back when solved his dog problem with a pellet gun rifle and scope.

 

[sholling]

Okay. It seems that you're interested in reducing sound transmission as opposed to sound reflection and those are definitely two different things. Your case is uniquue to anything I have read about because it doesn't involve a normal stud wall with a cavity that can be filled but the product you bought must come with spec's for product submittal.

Google this:

Submittal Sheet Fiberglas® 700 Series Insulations

It gives you some of the info that would be pertinent in using the 703 and 705 for speaker dampening and acoustic panels but some of the test numbers look a little skewed. Reducing sound transmission in a typical wall cavity is something I have read stuff on but it's not like I'm a guru ... just a mildly interested bored guy.

Correct me if I'm wrong but my understanding is that the stuffing in a vented cabinet is intended to prevent reflections off the interior walls and to reduce cabinet resonance sightly without reducing cabinet volume. I could have this entirely wrong but that's what my hours of Googling are pointing to. With the Behringers that I'm experimenting on the factory stuffing is an upside down U of 3/4" felt or something similar that is about 3/4" too narrow to prevent sound waves from going around it and reflecting back off of the corners. In other words cheap and dirty.

Here is what I'm going to be getting tomorrow. I spoke incorrectly earlier - its very heavy closed cell sound absorbent foam. This isn't the cheap stuff that parts-express sells to dampen subs. This at least 10x the density. Because it's flexible I should be able to cut a piece that fits snugly between the front and back of the cabinet which should block all corner reflections. I also have some 1/4 and 1/2" left over from previous (unrelated) projects and I'm tempted to cover the exposed wood of the back wall of the cabinet. It may suck hugely but if don't like it I can always pull it out and put in some 1" 703.

 

[Alex2507]

Thanks for the info Alex! I can get my hands on the rigid fiberglass material pretty easily. I am a sales manager for an HVAC company.

That's convenient.

Alex you mentioned a trick thread by Rickster71 so I will look around for it if I have some time later.

He just used a piece of all-thread with hockey pucks on either end to act as a brace. Nuts on the all-thread were used as friction anchors. I don't think he had a full bore thread.

You also mentioned "full width braces with holes drilled in them for a piece of all-thread at the 1/3 and 2/3 points to be snugged up with nuts and washers and then glued" . I am having a hard time visualizing this.
Would I be able to place the braces in without drilling straight through the cabinet?

Don't drill through the outside of the cabinet. We're not barbarians here. This is only an untried thought but let's say that the internal depth of the cabinet is 13". I'm saying to cut 2 braces 12" long and pre drill holes at 4" and 8" to accommodate the thickness of a piece of all-thread. The braces would go on the cabinet walls. All-thread fitted with nuts and washers placed in the pre-drilled holes would enable you to snug the braces against the side walls. Cutting the brace short would allow for manouvering and the corners are already braced by adjacent walls.

It's easy for me to yak about how this and that would work but I do understand that it is time consuming, tedious work.

Correct me if I'm wrong ...

My understanding is pretty incomplete so there's not much chance of that.

With the Behringers that I'm experimenting on the factory stuffing is an upside down U of 3/4" felt or something similar that is about 3/4" too narrow to prevent sound waves from going around it and reflecting back off of the corners.

A thread with pic's and a comparison of treated vs untreared would be cool.

 

[lmt9914]

Sholling, you have piqued my interest. So your saying, that by doing this your way, we keep true to the engineers original intent but just further reduce the cabinet resonance. I really am naive about this stuff so I am sorry if I don't sound knowledgeable about this.
Is the thickness of the Primus cabinet 3/4" all around ? Is this the standard in the industry for the most part? Maybe we can get WmAx to give further analysis to this. I am impressed by what I have seen from him. Hopefully I will become somewhat more knowledgeable as I go along. I really used to be into this stuff maybe 20 years ago but having kids etc. I need an outlet to satisfy my inner geek. Thanks to all for the input!
Thanks!

 

[sholling]

WmAx is the expert, I'm just a modding beginner fumbling around and extrapolating based on what I've read. The foam should be here in a bit and if I get time I'll give it a try. Unfortunately I don't have measurement gear and will just have to rely on an educated ear.

 

[Rickster71]

Alex you mentioned a trick thread by Rickster71 so I will look around for it if I have some time later.

He just used a piece of all-thread with hockey pucks on either end to act as a brace. Nuts on the all-thread were used as friction anchors. I don't think he had a full bore thread.

I used two pieces of All-Thread and an All-Thread connector, and drilled a dimple in each hockey puck to hold the All-Thread.
Figured the pucks aren't too big and wouldn't change the internal volume.

They could then be installed right over Peel n Seal, and the P&S wouldn't have to trimmed, as you would do, to go around the wood bracing.

 

[Rickster71]

I sometimes wonder if a few built up coats spray on under-coating (inside the box) or spray truck bed liner wouldn't work as well.

 

[Alex2507]

They could then be installed right over Peel n Seal ...

... pretty sure that's a no-no for bracing the cabinet and not enough to be a constrained layer.

 

[Rickster71]

... pretty sure that's a no-no for bracing the cabinet and not enough to be a constrained layer.

What are you thinking, that it would flatten the Peel N Seal too much?