- Joined
- Aug 12, 2022
- Messages
- 279
- Likes
- 237
The Purifi 10" is about 150mm deep so it's also not gonna work. Have you thought about a redesign on the house in order to accommodate the subwoofer? Maybe if you package it with a new back porch.......
I can be a bit stubborn! But truly, I have considered a lot of options before settling on the shallow, wall-mounted, stereo sub solution.Perhaps you need to reconsider your requirements?
What does "below 10% @ 20Hz " mean exactly? At what SPL and what distance?
What's strange about that? THX reference level is 115dB, so roughly the same. We can call it 110dB if you want, the problem remains the same.@mcdn Are you seriously suggesting you will be playing 20hz at 120dB? How many drivers are you expecting to use?
As you expect to hear 10% THD at 20hz, I am curious to hear if you have tested to play back a 20hz sine wave through your system? 20hz is barely audible even at 96dB. There's very little chance you can hear 10% distortion at 20hz when playing actual music or movie content. You can barely hear the fundamental.
Well, what's strange about it is of course that you need to fill your room with drivers, and that defeats the point of shallow mounting probably.What's strange about that? THX reference level is 115dB, so roughly the same. We can call it 110dB if you want, the problem remains the same.
And yes, I have played 20Hz tones in a system in a different room (the LXsub4 woofers in the family room can't play them). What you hear is indeed distortion, hence why the fundamental needs to be up at 110-120dB.
Don't we get 6dB per driver increase in SPL for correlated signals? so 120-83=37, 37/6 = ~6? And that's before room gain.Assuming 10% THD @20Hz @ 83dbSPL/1m for the SB26DBAC76-4 is correct, which doesn't seem entirely unreasonable, you will need roughly 64 drivers to reach 120dB@20hz/1m.
I suspect this is not the most space saving route to 120dB@20hz.
See the VituixCAD sims above as well. I love the idea of a room entirely covered by bass drivers but suspect that will have to wait until the children have left home.Well, what's strange about it is of course that you need to fill your room with drivers, and that defeats the point of shallow mounting probably.
The calculation of 64 drivers is free air assuming you didn't count on any room gain, so in reality you will probably "only" need around 20 drivers or so if we assume 10dB room gain at 20hz.
'Don't we get 6dB per driver increase in SPL for correlated signals? so 120-83=37, 37/6 = ~6? And that's before room gain.
Doh! Yes of course. So my VituixCAD sim has 3 x SB drivers giving 100dBSPL/1m with ~500W of power (see screenshot on page 1). That's for one enclosure, so two enclosures is 106dB. Add 6-12dB of room gain and we are there, no?'
You get 6dB per doubling of drivers. 2 drivers = 6dB, 4 drivers = 12db, 8 drivers = 18dB..
Doh! Yes of course. So my VituixCAD sim has 3 x SB drivers giving 100dBSPL/1m with ~500W of power (see screenshot on page 1). That's for one enclosure, so two enclosures is 106dB. Add 6-12dB of room gain and we are there, no?
Everything you say is true, but we are talking about peak SPL here. If we have 115dB of peak SPL capability with higher distortion, 100dB average with lower distortion is probably achievable, and that would work well with programme average SPL around 80dB.I guess three of those drivers might theoretically reach 100dB at 20hz at @1m, I suspect you won't be at 10% THD at 10mm excursion though. But ignoring your max THD requirements for a moment, a second enclosure might realistically perhaps give you 105dB. 12dB room gain (best case) will give you 117dB.
And this is of course at 1m, I'm not sure what SPL you are looking for at the listening position, and how far away that is. You theoretically loose around 6dB per doubling of distance, so if you're 3 meters away you're 9dB down. But bass works in mysterious ways in smaller rooms, so you might not loose that much in practice. So maybe 110dB at the listening position if it's not too far away, but likely not at 10% THD.
True, but I already have a system that is rolled off with an LR4 @ 30Hz, and it just isn't satisfying [edit - satisfying enough, it's fantastic of course, but it could do more] for movies or electronica.I would perhaps suggest reducing your requirements both in max SPL and also low frequency. Your shallow mount drivers (whichever you choose) will be much more comfortable and overall play at much lower distortion if they're not forced by DSP to play the lowest frequencies. Allowing them to roll off below 30hz would make for a much cleaner system, and will reduce the distortion significantly. 30hz is still very low (there is hardly any content below 30hz in most music), and 30-70hz is where most of the energy and punch is in movie effects as well.
Everything you say is true, but we are talking about peak SPL here. If we have 115dB of peak SPL capability with higher distortion, 100dB average with lower distortion is probably achievable, and that would work well with programme average SPL around 80dB.
Apart from ruling out the LS10-44 for its por distortion @ 20Hz, and the Purifi for being too deep, I'm still none the wiser on the best choice of driver though.