Anthony Curtas
Grip
- Joined
- Dec 8, 1998
- Messages
- 22
I have threads going on HTT, AudioAsylum, and others, but I think I have the problem narrowed down and want your all's opinion.
Last summer I built a riser for my HT. You can see it here:
http://www.geocities.com/acurtas/ht/base_layout.html
Recently, while tuning my subwoofer, I found a huge suckout from about 60 Hz to well above 80 Hz, and I couldn't place it at all.
Modal distribution was not great, but wasn't bad. Sub and listenening position weren't on nulls.
So on a whim, I turned my attention to the riser and panel resonators.
The riser is simply a frame of 2x10's with 1/2" plywood on top. Two layers of regular fiberglass insulation line the inside. Note that I said regular insulation, the kind with thick paper on the back.
Based on this website:
http://www.mhsoft.nl/Helmholtzabsorber.asp
I found out that my riser, unstuffed resonates at ~51 hz. Then I read that stuffing lowers the resonance point, so I figure I'm fine, right. Wrong. On all the plans I've seen for panel resonators, they use open fiberglass and acoustically transparent fabrics as to not reflect the sound. Figuring about 7" of insulation, that leaves about 2.5" of free space and a resonance of 100 Hz. Average those two values, and you get ~75Hz, which is exactly where my suckout occurs.
I BUILT A PANEL RESONATOR BY ACCIDENT AND IT'S SUCKING OUT MY BASS!!!!!!!
So now my question is, what do I do? What do you guys with risers do? Fill them with sand? Stuff the insulation really densely? Add multiple layers of plywood for stiffness?
All help is appreciated. At least I feel like I'm onto the solution now.
Thanks,
Anthony
Last summer I built a riser for my HT. You can see it here:
http://www.geocities.com/acurtas/ht/base_layout.html
Recently, while tuning my subwoofer, I found a huge suckout from about 60 Hz to well above 80 Hz, and I couldn't place it at all.
Modal distribution was not great, but wasn't bad. Sub and listenening position weren't on nulls.
So on a whim, I turned my attention to the riser and panel resonators.
The riser is simply a frame of 2x10's with 1/2" plywood on top. Two layers of regular fiberglass insulation line the inside. Note that I said regular insulation, the kind with thick paper on the back.
Based on this website:
http://www.mhsoft.nl/Helmholtzabsorber.asp
I found out that my riser, unstuffed resonates at ~51 hz. Then I read that stuffing lowers the resonance point, so I figure I'm fine, right. Wrong. On all the plans I've seen for panel resonators, they use open fiberglass and acoustically transparent fabrics as to not reflect the sound. Figuring about 7" of insulation, that leaves about 2.5" of free space and a resonance of 100 Hz. Average those two values, and you get ~75Hz, which is exactly where my suckout occurs.
I BUILT A PANEL RESONATOR BY ACCIDENT AND IT'S SUCKING OUT MY BASS!!!!!!!
So now my question is, what do I do? What do you guys with risers do? Fill them with sand? Stuff the insulation really densely? Add multiple layers of plywood for stiffness?
All help is appreciated. At least I feel like I'm onto the solution now.
Thanks,
Anthony