Cabinet Missing Insulation

[CheddarHeadG]

Doing a refoam on some curb-find Marantz SP-1500s. Pulled woofers to find the cabinet has ZERO sound deadening inside. These are a ported design - are they missing insulation by design? If needed, suggested materials?
Thanks!

 

[WillMeyer]

On sealed speakers I use fiberglass insulation, but that stuff is nasty (makes me itch like crazy). So on ported designs, I use polyfill with you can get from Walmart. They sell it two ways, in a box as loose fill, and in a blanet format. The blanket type can be cut and adhered to the walls. The loose stuff is, well loose, you shove in in the cavity. I'd use both.

 

[puppet]

You'd what the blanket since it's a ported enclosure. For starters, do (1) wall, the top and the back. Keep the port entrance clear.

 

[WillMeyer]

Yes, I'd keep the port clear. My JBLs are rear ported, so I slot the blanket so that it doesn't block the port.

The Marantz is front ported. The front is very difficult to blanket as all the drivers are on that face. Most people do not pad the front, but if you do, you do not want to impede the front port.

 

[Lavane]

The earlier Marantz speakers like the ported Imperial's used batting on the back. I have a pair of the Imperial 6 speakers and really like them. But all I found inside was a peice of thick batting covering the rear of the cabinet. They sound good, so I left it that way.

 

[toddalin]

I am currently in the process of installing insulation in ported cabinets that have none.

I am getting a nasty suck-out at 250 Hz and I've determined it to be the cabinet. I even took one of the cabinets to the front door and pointed it outside with the same results, and even more dramatic without room reinforcement. I get the same pattern simply rapping on the cabinet walls without the speaker mounted in the cabinet leaving a 16-1/2" hole and two ports on the one side.

My cabinets (internal dimensions) are 19-1/2"W x 22-3/8"T x 25-5/8"D. They are made of 1/2" plywood with a 3/4" baffle board and double layer 1/2" (1" total) plywood at the back (bottom 4").

I've made a pair of threaded tensioning rods to put pressure on the four walls to reduce resonances.

I've already lined the interiors with sonic barrier material...

https://www.parts-express.com/sonic...on-absorbing-sheets-315-x-1968-4-pcs--268-048

...and am in the process of covering this with acoustic foam material (1/2 done). They should be ready before Turkey Day. I have pics of the process and RTA readouts when in the living room (not outdoors). I also noted source volume, preamp volume, and dBA levels and mic positioning so I can recheck when done. Overall, I would expect the insulation to remove some volume (this is fine), but if it fills a dip by removing a suck-out...

https://www.parts-express.com/sonic...-enclosures-and-studios-12-x-12-x-1---260-546

 

[toddalin]

Starting point:

Tensioning rods to put pressure on the lively side walls:

Insides lined with "sonic barrier":

Completed insides with acoustic foam and tensioning rods:

 

[Poultrygeist]

Modeling programs can be used to determine damping patterns so it's less of a hit or miss proposition.

My Tektons have none and my Lowther MLTL's use a cheese cloth sleeve of polyfil but no damping material on the walls.