RSS-390HF "Oil Canning" question

[mike price]

I have two RSS-390HF's on hand , which I removed from a recently revamped project , and I'm about to build two subs from them. I have a few questions and concerns , about the inherent "Oil Canning" of theses subs when mounted in smaller enclosures. I would lie to build the subs as small as possible , 3.75 cubic feet each would be ideal for me as far as physical size is concerned , but as much as 5.5 is not out of the question. I have read several places about this "Oil Canning" effect when the RSS-390HF is mounted in "too small an enclosure" , but I never really did find anywhere at what volume this phenomenon begins. So in short , powered by an EP-2500 , how small of a sealed box can I get away with before they start "Oil Canning" ? Also , I know certain woofers parameters make them unsuitable for downfiring , is that the case with the RSS-390HF , or are they ok to downfire?

[mike price]

I suppose the next question would be at a given volume within my range , lets say 4.5 cubic feet , would porting the box eliminate the "Oil Canning" issue? Because I've done some modeling and it actually looks better ported to me , even in that small of a box , which was kind of surprising. Here's some models of both.

[fbov]

Downfiring is marginal. This driver is calculated to sag 5.5%, so you should model with 95% of Xmax to see the effect. Here's the formula, the source long forgotten, but Unibox gives me the same answer:
Percentage of Sag for Vertical Use = 24,849 / ( Xmax * Fs²)

I don't think you can oil can in a ported box. An EP2500 is enough amp to get you there. Check your excusion, though, because too big a box lets the cone bottom with less power. I can't speak from experinece (no ported subs), but I'd design with a small enough volume to control the cone, and a low enough tune that port output takes over below driver Fs. Unibox simulation at 5.5 cu ft and 18 Hz doens't look bad.

Have fun,
Frank

[fastbike1]

Unless the port is really small, porting should eliminate oil canning.

I suppose the next question would be at a given volume within my range , lets say 4.5 cubic feet , would porting the box eliminate the "Oil Canning" issue? Because I've done some modeling and it actually looks better ported to me , even in that small of a box , which was kind of surprising. Here's some models of both.

[mike price]

Unless the port is really small, porting should eliminate oil canning.

I've got a pair of 4" precision ports laying around also , based on simulations , they should be big enough , I'll probably go ported to avoid the possibility then. I wasn't sure if going ported would eliminate it , I remember reading somewhere , in an article about box construction , that the pressure inside a ported box was actually greater at port tuning than the pressure in a sealed box.

[kmibb]

I've got a pair of 4" precision ports laying around also , based on simulations , they should be big enough , I'll probably go ported to avoid the possibility then. I wasn't sure if going ported would eliminate it , I remember reading somewhere , in an article about box construction , that the pressure inside a ported box was actually greater at port tuning than the pressure in a sealed box.

You will need a pair of 4" ports per sub, at least. Those things move some serious air.

[AMC]

I've got a pair of 4" precision ports laying around also , based on simulations , they should be big enough , I'll probably go ported to avoid the possibility then. I wasn't sure if going ported would eliminate it , I remember reading somewhere , in an article about box construction , that the pressure inside a ported box was actually greater at port tuning than the pressure in a sealed box.

I have a 390HF in a 6.5ft^3 ported box, and I love it for it's primary application, which is HT. I will caution that I think it could be better for music. (I have it tuned to 19Hz) If you main goal is Music, tune it higher. Also, a 4 in each should be enough, I have run some very high SPLs, and have had no noise issues, the flares do their job well.

[mike price]

I have a 390HF in a 6.5ft^3 ported box, and I love it for it's primary application, which is HT. I will caution that I think it could be better for music. (I have it tuned to 19Hz) If you main goal is Music, tune it higher. Also, a 4 in each should be enough, I have run some very high SPLs, and have had no noise issues, the flares do their job well.

They don't do upper bass well , in my honest opinion , I have them on hand because I built a large pair of 3-ways based on the pair , and I was not impressed with the result. It's not really an issue though because my current mains are very solid down to about 40hz , which is about where I want these to take over. When I had them in my mains they were ported with the 4" precision ports and never heard a hint of port noise , they were in a much larger box however , which does have some effect on port velocity.

[wlb]

I have the 390HF in a 7cu.ft. box with a 4" by 11" long port tuned to 20hz. It sounds great for HT and music and I have mine crossed at 100hz. My older HT amp doesn't offer a lower Xover option. I have never herd any port noise even with all 500watts pumping through it. Never herd oil canning from it either.

[DIYNut42]

I have my RSS390 in 6.5 cu ft tuned to 17 Hz. I also used a 4" precision port, and its powered by a Bash 300S. I've noticed no chuffing at all even at high excursion. Never once had it oil can, but I thought that was only an issue with sealed enclosures.

My Onkyo crossed my mains @ 40Hz using Audyssey as well, and the sub fills in great. You won't be disapointed with that sub for LFE bass duty. The first time I fired everything up after running audyssey I tested it out using the opening sequence of the newest Star Trek movie at THX Reference volume. I definitely found out what pictures through out the house weren't rattle proof...

Like AMC said though, if you're wanting to use it for music it will need to be tuned higher. Mine does ok, but it's not very fast and punchy. I HAVE noticed though that when it comes to movie sound track music, if does great. Still haven't figured that one out...

[Pete Schumacher ®]

They don't do upper bass well , in my honest opinion , I have them on hand because I built a large pair of 3-ways based on the pair , and I was not impressed with the result. It's not really an issue though because my current mains are very solid down to about 40hz , which is about where I want these to take over. When I had them in my mains they were ported with the 4" precision ports and never heard a hint of port noise , they were in a much larger box however , which does have some effect on port velocity.

I remember you posting your project with those. I'm really curious why you think they don't do upper bass very well.

Where did you cross those to the pair of RS180 you were using as mids?

Just curious, since the upper bass I get from the RSS315 is exceptional.

[mike price]

I remember you posting your project with those. I'm really curious why you think they don't do upper bass very well.

Where did you cross those to the pair of RS180 you were using as mids?

Just curious, since the upper bass I get from the RSS315 is exceptional.

I was crossing to the 180's at 200hz , active. I listened to that setup for several months , and was just never happy with the upper bass , it seemed like the upright bass and bass guitar didn't sound right , and a bass drum sounded sort of muddy and muffled. Not the best explanation I know , but it's sort of difficult to explain what it sounded like , it just didn't sound right. When I built the cabinets I built them with removable baffles , so I have the same cabinets at present , with a completely different driver lineup. The new setup is an 18" Peavey Lowrider as the bass speaker , a Peavey-22a driver/P-Audio-H4427 horn as the mid , and an Eminence APT-50 driver/ Selenium-HM17 as the tweeter , all passive crossover. With the new setup , upper bass sounds much better to me , the lower bass , like with all pro drivers , is a little lacking(drops like a cliff below 40hz) , but this isn't a problem because I still have the pair of RSS390-HF's on hand to build a sub/subs. All that being said , I have no doubt the upper bass is fine from the RSS315's , I attribute the upper bass issue on the RSS390 to the cone being too heavy , and the cone of the RSS315 weighs about 50% less than that of the RSS390. The RSS315 has an Mms of 179 grams , the RSS390 is 273 grams , which is extremely heavy considering the Mms of the 18" I'm currently using is only 163 grams. I think what it all boiled down to in the end is that the RSS390 is truly a SUBwoofer , and when I tried to use it as a woofer , it didn't work out. I do however think that it will make a great subwoofer , or two.

[Pete Schumacher ®]

I was crossing to the 180's at 200hz , active. I listened to that setup for several months , and was just never happy with the upper bass , it seemed like the upright bass and bass guitar didn't sound right , and a bass drum sounded sort of muddy and muffled. Not the best explanation I know , but it's sort of difficult to explain what it sounded like , it just didn't sound right. When I built the cabinets I built them with removable baffles , so I have the same cabinets at present , with a completely different driver lineup. The new setup is an 18" Peavey Lowrider as the bass speaker , a Peavey-22a driver/P-Audio-H4427 horn as the mid , and an Eminence APT-50 driver/ Selenium-HM17 as the tweeter , all passive crossover. With the new setup , upper bass sounds much better to me , the lower bass , like with all pro drivers , is a little lacking(drops like a cliff below 40hz) , but this isn't a problem because I still have the pair of RSS390-HF's on hand to build a sub/subs. All that being said , I have no doubt the upper bass is fine from the RSS315's , I attribute the upper bass issue on the RSS390 to the cone being too heavy , and the cone of the RSS315 weighs about 50% less than that of the RSS390. The RSS315 has an Mms of 179 grams , the RSS390 is 273 grams , which is extremely heavy considering the Mms of the 18" I'm currently using is only 163 grams. I think what it all boiled down to in the end is that the RSS390 is truly a SUBwoofer , and when I tried to use it as a woofer , it didn't work out. I do however think that it will make a great subwoofer , or two.

Well, I will say that your experience is an exact mirror of what I got when voicing the Byzantiums.

I was crossing the RSS315 at 250Hz, and was really unhappy with the sound of upright bass. It wasn't until I pushed the XO point to 350Hz that everything came together.

[mike price]

Pete , if you were to build a sealed sub with an RSS390-HF , how big would you make the box?

[Pete Schumacher ®]

Pete , if you were to build a sealed sub with an RSS390-HF , how big would you make the box?

I'd give it no less than 3 cubic feet, preferably 4. Since we're discussing "oil canning" which some have heard in other variants of the Reference subs, better to be safe than sorry.

[mike price]

If I build them sealed , I will keep them at 4 to be safe. I'm having a real tough time deciding what to do with these drivers , I keep waffling between sealed and ported , and also whether to build them both in to one big sub , or two separate subs. I need a sub to fill in below 40hz with my mains , I have two RSS390-HF's , and two 4" Precision Ports on hand. I have about 200 bucks to buy wood to build enclosures , so I'll need to get them out of two sheets or less of Oak Plywood, and I plan on getting started Monday. When I originally posted this thread , I thought I had my mind made up to go sealed , Hence the oil canning question , but a small ported alignment looks pretty good too.

[Pete Schumacher ®]

If I build them sealed , I will keep them at 4 to be safe. I'm having a real tough time deciding what to do with these drivers , I keep waffling between sealed and ported , and also whether to build them both in to one big sub , or two separate subs. I need a sub to fill in below 40hz with my mains , I have two RSS390-HF's , and two 4" Precision Ports on hand. I have about 200 bucks to buy wood to build enclosures , so I'll need to get them out of two sheets or less of Oak Plywood, and I plan on getting started Monday. When I originally posted this thread , I thought I had my mind made up to go sealed , Hence the oil canning question , but a small ported alignment looks pretty good too.

Build two and place them along the midpoint of two walls. That'll give you the best shot at uniform room fill. Locations like that will produce "peaks" that can be EQ'd away. Placement that produces nulls cannot be EQd.

[mike price]

I'm in the process of drawing up these enclosures , looks like I'm going to go with two separate enclosures , 5 cubic feet , ported. I asked earlier in this thread about downfiring these , which is my normal first choice of sub orientation , but from some of the stuff I've read it might not be the best idea with the RSS390's ? Anyone ever done this and had ill effects ? Is it a really bad idea? Or would it be OK?

[Pete Schumacher ®]

I'm in the process of drawing up these enclosures , looks like I'm going to go with two separate enclosures , 5 cubic feet , ported. I asked earlier in this thread about downfiring these , which is my normal first choice of sub orientation , but from some of the stuff I've read it might not be the best idea with the RSS390's ? Anyone ever done this and had ill effects ? Is it a really bad idea? Or would it be OK?

If you don't plan on running these to max power, pushing the driver to Xmax, you should be fine with a down firing orientation.

Just make sure you have adequate high pass filtering since you're going with a vented enclosure.