In-wall rear surround recommendations

[snakeeyes]

Should have mentioned the previous curves are with both ports plugged. I'd like a little deeper extension, so I'm going to remove one port plug for now and redo everything. Also, I'm getting some localization at higher volumes because the damn floor is vibrating. I was thinking of giving the Subdude platform a try, or maybe spiked feet.

You will probably want one port plugged and operating mode EQ1.

 

[ryanosaur]

Spiked feet actually do not isolate. This is a serious misnomer.
They couple to the floor, and depending on the spikes, they do so very, very well.

I used the svs soundpath feet and like them a lot.
Before buying a pad, fold up some towels or a blanket and try that under the sub first, just to confirm the effect.

Also, do you have carpeting up there, or hard floor?

 

[mossman77]

Spiked feet actually do do isolate. This is a serious misnomer.
They couple to the floor, and depending on the spikes, they do so very, very well.

I used the svs soundpath feet and like them a lot.
Before buying a pad, fold up some towels or a blanket and try that under the sub first, just to confirm the effect.

Also, do you have carpeting up there, or hard floor?

I read the same thing about spiked feet. Yeah, they would pierce through the carpeting directly to the subfloor!

Carpet over 3/4" plywood subfloor with 24" joist spacing (unfortunately).

Towels helped a little, but I can still feel the bass in the floor. Guess complete isolation may be unrealistic. I could give the Subdude a try and return it if it didn't make much difference. Or maybe just make my own custom base out of wood and filled with foam and/or sand.

 

[ryanosaur]

I have a very spongy floor, suspended wood. I used a platform on spikes as the foundation, then the isolation feet on the sub, which sits on the platform.

That strategy worked well for me at eliminating a lot of vibration in the structure.

It will not prevent the soundwaves from rattling things. LF Soundwaves are powerful beasts.

Good feet or a pad might help. Try that towel thing just for the experiment.

 

[mossman77]

I have a very spongy floor, suspended wood. I used a platform on spikes as the foundation, then the isolation feet on the sub, which sits on the platform.

That strategy worked well for me at eliminating a lot of vibration in the structure.

It will not prevent the soundwaves from rattling things. LF Soundwaves are powerful beasts.

Good feet or a pad might help. Try that towel thing just for the experiment.

Did you make a homemade platform? I'd prefer a custom solution actually. I have all the tools to do so (table saw, router, etc). I could make say a 12" tall box out of oak, fill it with sand with layer of foam on top (foam topped with black automotive carpet), stain the box black. Would probably look pretty sharp.

 

[Pogre]

You will probably want one port plugged and operating mode EQ1.

Or both ports open, eq 2. That's how I run mine. I like the little bit of extra output.

 

[Pogre]

Oh! When you're running room correction HSU recommends you do it with both ports plugged on EQ 1! After running room correction then you play with the number of ports and which EQ setting you prefer.

 

[ryanosaur]

Did you make a homemade platform? I'd prefer a custom solution actually. I have all the tools to do so (table saw, router, etc). I could make say a 12" tall box out of oak, fill it with sand with layer of foam on top (foam topped with black automotive carpet), stain the box black. Would probably look pretty sharp.

I have a local custom concrete shop that has a boneyard for scrap countertops and such that didn't make the final cut. They let me in to root through the scraps. I found two pieces that gave more than enough material to make 4 platforms for my Mains and Subs.
The concrete they pour is pretty inert, acoustically, and filled with a good amount of aggregate
They cut them to the size I specified and drilled holes in them to receive some threaded inserts.
These platforms were mounted on Outriggers I bought from Soundocity.

Here's a link to a thread I had while I was setting up my mains, you can see the platforms in this post.

This post from a different thread shows the sub on a platform, as well as me working on getting the platforms assembled.

For me, with down firing subs, I was concerned (misplaced) with the carpet being the first thing the soundwaves saw. But more importantly, the isolation feet, set on a platform that can actively dampen any physical vibration was my goal. I have seen some reports that this two part approach requires the Damping platform to be Coupled to the floor very well, hence the outriggers with spikes.

Maple cutting boards are good to use as a platform.

If you choose to make a box like you described, I would think that might be overkill... ...but nothing wrong with that. You would basically be doing what this cat did:

 

[mossman77]

Oh! When you're running room correction HSU recommends you do it with both ports plugged on EQ 1! After running room correction then you play with the number of ports and which EQ setting you prefer.

Oh really? I'm surprised to learn that. Won't opening the port(s) afterwards completely change the response? Guess that would be pretty simple to determine. Yet more measurements to take!

 

[ryanosaur]

I may be wrong, but I think that the changes in that situation, are different than the actual issue of room correction: Placement of the source and interaction with the room.

 

[Pogre]

Oh really? I'm surprised to learn that. Won't opening the port(s) afterwards completely change the response? Guess that would be pretty simple to determine. Yet more measurements to take!

Well first, I remembered wrong. It's supposed to be EQ1, 1 port open. This is from the site.

Should I use the Auto EQ in my receiver?

​

Generally the auto EQ in receivers are getting better and better, and it's usually beneficial to use them. One general guideline for using the auto EQ for the subwoofer - set the subwoofer for the lowest extension and flattest response so the EQ compensates for the room acoustics alone. e.g. with our VTF series subwoofer, set the ubwoofer to one port open, EQ1, and Q=0.7. This is the flattest response mode. The EQ will then correct for the room effects. After EQ, you can select other operating modes for the subwoofer - two ports open, EQ2, Q=0.3, etc.

I think the idea is to get it dialed in on the flattest, lowest extension mode, then when you open the ports and flip to EQ2 you'll hear the little bit of extra output it offers in that 25-30 hz range.

 

[mossman77]

Well first, I remembered wrong. It's supposed to be EQ1, 1 port open. This is from the site.

Should I use the Auto EQ in my receiver?

​

Generally the auto EQ in receivers are getting better and better, and it's usually beneficial to use them. One general guideline for using the auto EQ for the subwoofer - set the subwoofer for the lowest extension and flattest response so the EQ compensates for the room acoustics alone. e.g. with our VTF series subwoofer, set the ubwoofer to one port open, EQ1, and Q=0.7. This is the flattest response mode. The EQ will then correct for the room effects. After EQ, you can select other operating modes for the subwoofer - two ports open, EQ2, Q=0.3, etc.

I think the idea is to get it dialed in on the flattest, lowest extension mode, then when you open the ports and flip to EQ2 you'll hear the little bit of extra output it offers in that 25-30 hz range.

Thanks for clarifying. Coincidentally, I am running one port open with EQ1 already, although I think I ran REW and Audyssey when I had the ports plugged. Oh well, doing everything again anyway.

 

[mossman77]

Just wanted to share this informative article I stumbled across this evening:

House curve: What it is, why you need it, how to do it!

www.hometheatershack.com

 

[mossman77]

Spent some more time last night and got a pretty good response now. I need to look more into the waterfall plot to see if it is satisfactory (still learning what would be the best time domain response in my space).

Question on levels...the first time I ran Audyssey, it set the sub level to -12dB, so I cut the gain in the miniDSP by 10dB and ran Audyssey again. Audyssey then set the sub output at -5dB, which I believe is good. Afterwards, I tweaked the response using the miniDSP. The bass was a little lacking, so I put the miniDSP gain back to 0dB. Is this a bad idea? I basically boosted everything by 10dB in doing so, right? Would it have been better to keep the miniDSP at 0dB and instead cut the gain of the individual subs (via the gain knobs)?

In summary,

1st Audyssey run: miniDSP at 0dB, resultant Audyssey sub level -12dB
2nd Audyssey run: miniDSP at -10dB, resultant Audyssey sub level -5dB
Current configuration: left Audyssey/AVR sub level at -5dB, set miniDSP back to 0dB

My concern is since I boosted (technically un-attenuated) the signal through the miniDSP, that I could be driving the subs to distortion/clipping and not know it.

Here's the FR and TR plots I ended up with. There's a sharp dip at 120Hz in FR that corresponds to a peak in the TR. Not sure if this is a good waterfall response. Doesn't really look as nice as others I've seen. Shouldn't the SPL be down much further at 300ms? At this rate, it looks like the decay time would reach a second or more. And my waterfall dips, levels out, then dips again. Don't think that's ideal. I'm guessing the bouncy subfloor and having the subs too close to the wall could be a contributing factor to the prolonged decay times. I'll have to experiment some more I guess. Maybe turning the Q on the subs all the way down would help? Note the scales are different (FR is 10Hz to 120Hz and TR up to 200Hz).

 

[mossman77]

Here's the spectrograph, which makes things look a little better (most energy above 30Hz dropping off after 200ms):

 

[Pogre]

Those all look really good. You really dug in and did your homework, that much is evident. I know most folks would be pretty happy with that.

-5 for trim levels is a good spot. If it was setting -12 then you need to back off the gain a touch. If you feel bass is lacking try playing with Dynamic EQ and the Reference Level Offsets. DEQ is like a built in house curve and RLO controls how aggressive it's applied.

 

[ryanosaur]

Just wanted to add, that I think adjusting gain at the sub, rather than the mDSP is advised. The AVR should have you in the -5dB range, and I would shoot for 0dB adjustment on the mDSP.

 

[mossman77]

Those all look really good. You really dug in and did your homework, that much is evident. I know most folks would be pretty happy with that.

-5 for trim levels is a good spot. If it was setting -12 then you need to back off the gain a touch. If you feel bass is lacking try playing with Dynamic EQ and the Reference Level Offsets. DEQ is like a built in house curve and RLO controls how aggressive it's applied.

Thanks. Okay. I'll keep fiddling around.

 

[mossman77]

Just wanted to add, that I think adjusting gain at the sub, rather than the mDSP is advised. The AVR should have you in the -5dB range, and I would shoot for 0dB adjustment on the mDSP.

I went ahead and did just that. Was playing around with sealed vs. one port open vs. different Q settings (on the plate amps). I ended up with both ports blocked and Q at 0.7 (highest setting). This is what sounds best at the moment (adjustments done by ear, not REW). Sealed with Q at 0.3 kind of killed the low end and one port open is not tight enough for my liking. I think the room is the issue now, as evidenced by the waterfall and spectrum plots. I'm thinking of perhaps using a couple bass traps here and there to see if I can get the decay times down and tighten things up. Opinions on GIK bass traps? Do you guys think it would also be beneficial to put an absorber panel on the wall behind the listening position and/or on the ceiling above? If you'll recall, my couch is up against the rear wall with a 4' overhang ceiling/balcony above, so I feel like the listening area is one large bass trap, and not the good kind. I don't want to have panels hanging all over, but a few corner bass traps upstairs in the hall and a panel or two on the wall behind the couch and/or ceiling above wouldn't be so bad. I like that GIK has several fabric options.

 

[Pogre]

Did you do any experimenting with both ports open, eq 2? You don't have to recalibrate anything, just open 'em up and let 'r rip. Make sure you switch to eq 2 with both ports open tho. EQ 1 with both open will actually void the warranty if something goes wrong.