Earl, can I ask a few questions regarding placement?
1. How far from the front wall do you recommend placing the Nathan?
2. How much would it degrade the performance by putting it closer to the front wall?
3. Do you recommend wall treatment on the front wall?
By front wall, I mean the wall behind the speaker.
Thanks
1. How far from the front wall do you recommend placing the Nathan?
2. How much would it degrade the performance by putting it closer to the front wall?
3. Do you recommend wall treatment on the front wall?
By front wall, I mean the wall behind the speaker.
Thanks
David Gatti said:
Toole and I both recommend damping the wall behind the speakers. If this wall is very well damped then the speakers can be quite close. But in general away from the front wall is a good idea if this is possible. But better the speakers sit against a wall than the listeners. How much performance degradation s impossible to say since the situation is so room specific.
I try to keep the space arround the speakers a s "clutter" free as possible. Anything, TV's, bookcases, etc. can cause diffraction even if they are at the sides of the speakers. If the speakers are toed-in as I suggest then nothing should be between the speakers as this will diffract the sound. How much? Hard to say - I only know that the more I tried to eliminate these difractions the better the image got.
gedlee said:
What about building the speakers into the wall - Provided that the speakers face the right direction and the integration is smooth to avoid diffraction? This should eliminate short delay reflections and improve imaging?
What if one applies absorbent materials to the front wall in which the speakers are mounted but keep the surfaces to the rear of the listener very reflective, i.e. have more reflection where the power response of the speaker is at its best, and less where the power response is not so good? Or will such a layout sound unnaturral?
I've been looking at the curves and thinking about the "constant directivity" issue. Since the SPL is almost constant within +/-22.5 deg, if we toe in the speakers at 45 deg, and sit at 60 deg position so that the speaker axes cross in fron of the listener, we are sitting 15 deg off axis, which is still in the constant directivity region. As we move to the side, it seems best that the time difference shift best be the same as the intensity difference shift. Has anyone calculated this for CD speakers?
When I measure the wave guide again, I plan to rotate about the AC axis but indicate SPL angle from the mouth plane.
When I measure the wave guide again, I plan to rotate about the AC axis but indicate SPL angle from the mouth plane.
Attachments
See how the horn/guide effects the driver impulse.
Top one is with horn/guide, bottom one is without.
An externally hosted image should be here but it was not working when we last tested it.
Top one is with horn/guide, bottom one is without.
soongsc said:
Soonsc
If you read my white paper on the Summa you will see that this is precisely why I toe in the speakers and that this effect has been carefully worked into my designs. But don't forget that the off-axis response at the crossover must also be constant directivity, which is not so easy, and again, it is precisely why I use large diameter drivers - for their directivity NOT their LF response.
Hennie said:
Workable, but difficult. Toeing the speakers in at 45 degress presents some mounting problems, unless the speakers are in the corners, which is OK except that in most rooms this is way too far apart forcing one to be very far back to not be on-axis. Damping the wall around the speakers would be good.
I always keep the wall behind the listeners highly reflective as this increases the spaciousness effect quite a bit. But you need to be fairly far from this back wall if you are not to have early reflections from it at the listeners position.
If you lay these requirements out you will find that what you suggest is difficult to impliment unless the room is very long and narrow, in which case it can be made to work.
Generally speaking every room is different and each one has to be considered seperately as to what is workable and what is not.
gedlee said:
One thing to consider is that the closer the speaker to the front wall, the higher the frequencies at which reflected waves will cause problems (dips and peaks), and the easier it will be for absorbers to damp them.
But on the other hand the further from the wall the lower the volume of the reflexted waves at the listening position.
So is it easier to damp low frequencies at low volumes or high frequencies at high volume?
this is called a lede room (live end/dead end), and is a common practice in controls rooms.Hennie said:
pos said:
One thing to consider is that the closer the speaker to the front wall, the higher the frequencies at which reflected waves will cause problems (dips and peaks), and the easier it will be for absorbers to damp them.
But on the other hand the further from the wall the lower the volume of the reflexted waves at the listening position.
So is it easier to damp low frequencies at low volumes or high frequencies at high volume?
this is called a lede room (live end/dead end), and is a common practice in controls rooms.
My speakers are so directional that there isn't much HF energy going to the back.
Doesn't LEDE use the absorption behind the listener?
That is approach I took - But my listening area is ( for the most part ) open, and does not have parallel walls. The walls in which my drivers are placed are angled.
So taking those things into consideration that Dr. Gedlee just mentioned ( angle / spacing / less modes and nodes ) my area works very well. But for the majority is not workable or desirable.
To my humble ears it sounds closer to a 180 degree radiation, without baffle diffraction. The imaging is greatly improved.
HK26147 said:
Thanks for all responses.
Well that is interesting. I'm considering a dedicated room with angled inner walls. Then it seems possible to meet the following constraints simultaneously:
- Main speakers toe-in of 45 degrees
- Off axis listening position, eg 22 degrees.
- Speakers mounted in the inner walls so as to reduce diffraction
- Dead end on the speaker side
- Live end on the opposite side
A largish room would be required and the angled inner walls would waste quite a bit of space but I think it may give me less early reflection and diffraction. The question is: If I can meet all the other necessary placement criteria and constraints work in a dedicated room do I really derive additional benefit from mounting the speakers in the wall, designing for the lowest diffraction there and applying absorbent materials to that wall?
I'm also confused w.r.t. the LEDE concept. The LEDE adherents I encountered in the audiophile world seem to want a live end at the speaker side as Dr Geddes said. But I know that the opposite arrangement i.e. dead at the speaker side and live at the rear is quite common in the professional world. This last arrangement makes much more sense to me.
I think the original lede concept is to have a front wall that will absorb all frequencies but the lower ones (2Pi steradian loading for LF).
On the contrary the back of the room will reflect and diffuse high frequencies, but some special absorbers might be used to absorb low frequencies (resonators, bass traps, etc.) and still reflect the highs.
On the contrary the back of the room will reflect and diffuse high frequencies, but some special absorbers might be used to absorb low frequencies (resonators, bass traps, etc.) and still reflect the highs.