Open door -- the ultimate bass trap?

[JohnA]

Suppose you have a door in a corner (along with the floor, we've got three surfaces meeting).
If there was no door, that would have been a very good location for a bass trap.
But if that door is open (I actually had it removed when I moved in the house and don't intend to replace it) is it not the ultimate bass-trap?
Surely any waves that try to accumulate there will be dispersed outside the room and practically none of them will ever come back.

Am I right, or am I missing something major here?

In fact I've also got another corner door in the room, and empirical evidence suggests that extremely loud music is less boomy when it is wide open (it leads to a conservatory, so most of the acoustic energy through there will be gone for good).

Opinions please...

[Craig]

Isn't an absorption panel or bass trap about the same or similar to an open window or open door? It makes sense since there is nothing there to reflect sound and to create peaks or nulls. However, panels and bass traps don't absorb all the frequency ranges but an opening certainly would.

Since I have my speakers in my system located closer to the right wall than the left, I put more absorption on the right wall to compensate. It seems to work better setup that way. It's an attempt to balance the asymmetrical speaker positioning in my room.

Interestingly, I was at Sleepysurf's yesterday checking out his latest configuration of his HT/Audio system. He has one of the newer Denon receivers with the Audessy Room Correction. We took a look at the graphs of frequency corrections calculated by the Audessy and it reduced the lower frequencies on his left speaker much more so than the right speaker. The left speaker is near a corner and the right speaker is near an opening to another room.

We figured that his room would probably benefit with some absorption in the left corner and there isn't really much of a corner on the right side for any absorption devices the but room correction showed that it probably isn't needed there anyway. The frequency graphs from the Audessy Room Correction seemed to confirm that the open corner had less bass peaks than the closed corner.

[JohnA]

Yeah, that's my line of thought, but since I haven't got JonFo's nice before/after waterfall graphs I can only speculate...

[kach22i]

Your room is an enclosure which acts like a band-pass. By opening that door you allow that energy to escape.

In my home the bass sound energy travels up the stairwell from the living room, bass is all you hear up there on the second floor and it's quite annoying just hearing that part of the music (if you happen to be up there).

There was a thread last year where someone proposed setting up very large speakers in a small room, the solution was to keep the pair of French doors behind the listener's head open to the rest of the house.

[sleepysurf]

Interestingly, I was at Sleepysurf's yesterday checking out his latest configuration of his HT/Audio system. He has one of the newer Denon receivers with the Audessy Room Correction. We took a look at the graphs of frequency corrections calculated by the Audessy and it reduced the lower frequencies on his left speaker much more so than the right speaker. The left speaker is near a corner and the right speaker is near an opening to another room.

We figured that his room would probably benefit with some absorption in the left corner and there isn't really much of a corner on the right side for any absorption devices the but room correction showed that it probably isn't needed there anyway. The frequency graphs from the Audessy Room Correction seemed to confirm that the open corner had less bass peaks than the closed corner.

Attached are photos of my room (open hallway/door on right) and the Audyssey *CORRECTIONS* (this graphic is really a condensed view of the hundreds of corrections Audyssey actually makes). Nonetheless, it really illustrates the corner, and other room effects. As with the LEFT front Summit (near a corner) my RIGHT rear in-ceiling surround is also closer to the back room corner, so Audyssey employs more bass EQ. I've also included the EQ correction for my Motif center channel.

Overall, I'm impressed with what Audyssey does, but WILL still add bass traps to smooth the response further.

[JohnA]

Attached are photos of my room (open hallway/door on right) and the Audyssey *CORRECTIONS* ....

Interesting view and relevant to the question, thanks

As a sidequestion, why on earth does Audyseey add so much midrange and treble? It's not exactly that you have heavy drapes is it?

[sleepysurf]

As a sidequestion, why on earth does Audyseey add so much midrange and treble? It's not exactly that you have heavy drapes is it?

I presume those mid and treble boosts are filling in (relative) room nulls. I, too, was quite surprised by the degree of EQ required. Overall, the Audyssey effect is quite good, but arguably not as "musical" as I'd like. Thus I've also tried feeding my tube pre-amp into the Denon/Audyssey, before routing back to my separate amp. That effect is a bit more "musical" sounding, but involves extra A to D, then D to A, conversions, plus two extra sets of cables. I'm not sure that's the best solution. I'm hosting a local listening session at my place tomorrow, and will report back what the "golden ears" have to say!

[amey01]

It would depend deeply on what is on the other side of that door. Unfortunately, I've got that exact problem. I don't have doors so can't close them. The open out onto a large, tiled area that is the kitchen/family room/dining room. I jolly wish I could close the door!!

[Audioseduction]

I leave the door open at one end to my den that leads into my office. Helps out very much with the bass.

[JohnA]

It would depend deeply on what is on the other side of that door. Unfortunately, I've got that exact problem. I don't have doors so can't close them. The open out onto a large, tiled area that is the kitchen/family room/dining room. I jolly wish I could close the door!!

If the volume of that area is large enough - and yours sounds like it is - then it would absorb far more low-frequency energy than what it would allow to reflect back into the HiFi room.

I try to imagine it like ripples in a lake. In such a case the edge of the lake is linked to another lake. Sure, some form of ripple will always come back after bouncing around the 'adjucent' lake, but it will have lost so much energy that it would have no impact any more. The Audyssey graphs here seem to support this model, don't they

[amey01]

If the volume of that area is large enough - and yours sounds like it is - then it would absorb far more low-frequency energy than what it would allow to reflect back into the HiFi room.

I try to imagine it like ripples in a lake. In such a case the edge of the lake is linked to another lake. Sure, some form of ripple will always come back after bouncing around the 'adjucent' lake, but it will have lost so much energy that it would have no impact any more. The Audyssey graphs here seem to support this model, don't they

Oh sure - it may well do - but it certainly doesn't sound nice with the resonances higher up in the frequency band!!

[JonFo]

Opening the door of my HT does reduce the very low-end a bit. As the room can’t quite ‘pressurize’ at <40hz if the door is open.

But depending on opening size, it really does not have major impact on 80 to 300hz, which is where treatments are effective, and usually needed.

I still think treatments work better, but if opening a door helps, then well, that’s good