Angle?

[User211]

The Apogee (Duetta) solution was to rake the speaker back at 2.5 degrees as a whole, but the MRT ribbon is pivoted at 3/4 of its length i.e. the last quarter is at somewhere between 10 to 20 degrees at a guess - I haven't measured it. And so are the magnets at that last top section i.e. they follow the ribbon angle.

That does work well when standing. I've messed with the rake angle of the entire speaker but 2.5 degrees does seem to be a very good angle to have them at. I'm guessing Diva was so tall there was no need for the ribbon pivot.

Leo Spiegel was a very clever man who understood how to balance various compromises extremely well.

It's not really an option with an ESL panel, which is a bit annoying but hey.

 

[Bevensee]

Well, thinking that way, why are you using the spikes in your Summits? Take them off, and you will be making a solid connection with the floor, right? What I am avoiding is that. You do not want to transfer the bass energy to the floor, because it will resonate. If I use the spikes, the only what it is resonating are the Summits cabinets. This allows better bass, less boom boom, and cleaner bass too.

Roberto, I think you may be wrong here, or else I misunderstood you. Spikes WILL couple the speakers to the floor, causing it to resonate if it will. I have a wooden floor that resonated dramatically when I used spikes under my Vantages. Now I have a 5 cm thick slap of granite between the spikes and the floor, and that has improved bass-clarity dramatically. The clever thing about spikes is that cabinet vibration energy is directed into the floor, where it (hopefully) will be converted to heat, or directed into the foundation of the building, and after that the ground (alternatively the guy who lives below...;-)). This works quite will on concrete, which does not resonate at bass frequencies, or on wooden floors if they are damped by heavy (thick) carpets (provided, of cause, that the spikes are long enough to penetrate the carpet). On "naked" wooden floors (especially if there is a basement below), spikes can turn the whole floor into one huge soundboard.

Sorry for the off-topic...

 

[Bevensee]

I have been pondering over this rake thing for some time (I find that it makes a difference, but I am a bit unsure why). Here are some thoughts. Comments are welcome...

1) What is the difference between changing the rake and bowing the head? Surely, if there were no room boundaries, and the speakers were hanging in mid-air, there would be none.

2) Since the panel is emitting (part of) a cylindrical wave, we are actually only hearing the DIRECT sound from a small section of the panel. The rest will shoot either above or below our ears.

3) If this is correct, any difference will depend on
a) The height of the seat and how far from the speakers one is sitting.
b) The angle of the head while listening (leaned back in a couch, of leaning forward)
c) The built-up of standing ways between front and back wall (here, rake will be an advantage in "hard" rooms)
d) The phase-alignment between woofer and the small section of the planning that aims at the ears.

This small analysis tells me that we should be careful and experiment since the optimum will depend on many things; including room, placement, height of seat etc.

 

[roberto]

Hola. Your spikes are a coupling device. Pressure equals force into area. P=f/a If your point of force (weight) f is smaller, the energy transfered is reduced. If you increase the size of the point contact to the area, more energy will be transfered. This is simple physics. "spikes under a loudspeaker should reduce the amount of sound energy transmitted between speaker and stand because they reduce the area of contact between the speaker and the wood floor. Hence if we make the contact area tiny, this approaches zero, so should only allow a small amount of vibration through. This is the ideal situation. But it is not necessary what happens sometimes. You need to decouple (your granite base) this bass energy from the floor.

 

[Gordon Gray]

1) What is the difference between changing the rake and bowing the head?

Answer. A sore neck. :ROFL:

Sorry Bev, I couldn't resist.

GG

 

[Bevensee]

Hola. Your spikes are a coupling device. Pressure equals force into area. P=f/a If your point of force (weight) f is smaller, the energy transfered is reduced. If you increase the size of the point contact to the area, more energy will be transfered. This is simple physics. "spikes under a loudspeaker should reduce the amount of sound energy transmitted between speaker and stand because they reduce the area of contact between the speaker and the wood floor. Hence if we make the contact area tiny, this approaches zero, so should only allow a small amount of vibration through. This is the ideal situation. But it is not necessary what happens sometimes. You need to decouple (your granite base) this bass energy from the floor.

I think you are wrong here, Roberto. The force F from an object onto a surface on which it lies is given by its mass times the gravity, i.e. F=m*g.

The pressure applied to the surface is, as you correctly write it, given buy P=F/a, which in turns yields P=(m*g)/a. In other words, the smaller the area, the higher the pressure. This is why it hurts more to be stepped on by a woman in stilettos than sneakers.

When we put spikes under our speakers, we secure a super-efficient coupling to the floor because of the very high pressure. This very efficient coupling secures very good transfer of energy from the speaker to the floor. But since the spike has a much larger contact area tot he speaker, the energy transfer from the floor to the speaker is not very good.

 

[roberto]

Ok...Thanks!!! I got the concept wrong. But what happens if we could have the speakers lifted like floating without touching the floor? I had taken away bad speaker resonance from the floor with the aid of rubber between the spikes and the floor. Strange, right? Thanks for letting me know how wrong I was with the concept.

 

[Bevensee]

Roberto, you are absolutely right that rubber between speaker and floor stops the floor from resonating. When I bought my speakers, I tried first with some soft foamy feet. The bass was good, but everything else was all over the place. I discovered that the whole speaker would rock back and forth very easily. Apparently, ML speakers like to be quite good anchored. Wasn't it Gordon who once recommended hockey-pucks? It makes sense to me, as they probably would stop the low frequencies from exciting the floor, but they are hard enough to stop the speakers from rocking along with the music.

On a site-note, I read again your description of how you tune your guitars to resonate evenly with most of the spectrum. I bet it sounds beautiful! I would love to hear the fantastic Getz/Gilberto/Joabim albums in your house...

 

[Brad225]

This is why it hurts more to be stepped on by a woman in stilettos than sneakers.

OK someone has to ask, so it may as well be me. Does this happen to you often? :-0

 

[Bevensee]

OK someone has to ask, so it may as well be me. Does this happen to you often? :-0

Not lately, but I used to do a lot of ball-room dancing,...

 

[Rich]

Wasn't it Gordon who once recommended hockey-pucks? It makes sense to me, as they probably would stop the low frequencies from exciting the floor, but they are hard enough to stop the speakers from rocking along with the music.

That was me. I have my summits mounted on four hockey pucks each, sitting on a laminated hardwood floor. I drilled a small cone-shaped indention in the top of each puck, which the spikes fit into perfectly. It works great. Also makes it easier to make small adjustments when fine-tuning speaker position. Highly recommended.

 

[roberto]

Roberto, you are absolutely right that rubber between speaker and floor stops the floor from resonating. When I bought my speakers, I tried first with some soft foamy feet. The bass was good, but everything else was all over the place. I discovered that the whole speaker would rock back and forth very easily. Apparently, ML speakers like to be quite good anchored. Wasn't it Gordon who once recommended hockey-pucks? It makes sense to me, as they probably would stop the low frequencies from exciting the floor, but they are hard enough to stop the speakers from rocking along with the music.

On a site-note, I read again your description of how you tune your guitars to resonate evenly with most of the spectrum. I bet it sounds beautiful! I would love to hear the fantastic Getz/Gilberto/Joabim
albums in your house...

My system is your system, my place is your place. When ever you decide to jump the pond and have a jungle visit, you are welcome!!! Love Stan Getz with Joao Gilberto and Astrud Gilberto. Please, come and play with my toys!...besides, a nice evening wine will be served for sure!

 

[Bevensee]

Thanks Roberto! I will keep it in mind next time I "jump the pond". The invitation is hereby returned is you should ever find your feet on European ground.

 

[beanbag]

I have been pondering over this rake thing for some time (I find that it makes a difference, but I am a bit unsure why). Here are some thoughts. Comments are welcome...

1) What is the difference between changing the rake and bowing the head? Surely, if there were no room boundaries, and the speakers were hanging in mid-air, there would be none.

2) Since the panel is emitting (part of) a cylindrical wave, we are actually only hearing the DIRECT sound from a small section of the panel. The rest will shoot either above or below our ears.

3) If this is correct, any difference will depend on
a) The height of the seat and how far from the speakers one is sitting.
b) The angle of the head while listening (leaned back in a couch, of leaning forward)
c) The built-up of standing ways between front and back wall (here, rake will be an advantage in "hard" rooms)
d) The phase-alignment between woofer and the small section of the planning that aims at the ears.

This small analysis tells me that we should be careful and experiment since the optimum will depend on many things; including room, placement, height of seat etc.

1) Bowing the head affects HRTFs, i.e. head related transfer function, which is a fancy pants way of saying that due to the shape of your ears, you can tell how high something is. Even if you bow your head, you can still tell that the speaker is in front of you, and that its elevation did not change. Changing the rake will affect the frequency response of the sound coming at you due to interference and diffraction effects from panel-woofer interactions.

2) No, you are hearing all parts of the panel due to Huygens wave propagation mechanics stuff. Its because of this that you can derive frequency response, diffraction, and lobing effects from curvilinear panels and etc.

3) Even though 1) and 2) are wrong, 3) is still right.

 

[Gordon Gray]

1) Changing the rake will affect the frequency response of the sound coming at you due to interference and diffraction effects from panel-woofer interactions.

Not. It may affect the panel - woofer integration but highly unlikely.

What it does do and what you hear (assuming set perpendicular) is the elimination of any "time delay / arrival" issues from the sound coming from the top of the panel and the bottom.

 

[beanbag]

Naw, you got it exactly backwards.
It's because the panels are tall that in the vertical axis the sound waves are more like a line source, and thus rake does not have much of an effect on frequency response.

Put it another way, you forgot that the panel has a middle section too, and that a panel of finite size will always interfere with itself.
If the panel is facing right at you, BOTH the (sound from the) top and bottom third are delayed from the center section by an amount X. Total delay of 2X.
If the panel is raked back, there is no delay between the bottom and middle section, but the top is now delayed by 2X. Total delay of 2X.*

It does not matter "where" the delay comes from since only the total delay is going to mash into comb filtering at your ears anyway.

The woofer acts like a point source, so its delay relative to the panel is exactly related to rake.

*This is not exact, but mostly correct.

 

[Gordon Gray]

I didn't forget about it.

I thought it was obviously inferred by my post.

I guess you missed it.

Regarding your mathematical thesis, I should have clarified that I was not talking about frequency response per se but the audible effects of a perpendicular rake angle. Said effects include an increase in speed and transient response, a better detailed, more dimensional soundstage, and improvements in the panel / woofer integration. And yes, certain frequencies are more apparent (read more present / less smeared) with this rake angle.

 

[beanbag]

And what makes you think these effects are due to the panel rake angle vs the panel and woofer distance?

 

[Rich]

Personally, I think the rearward rake of modern ML's is a design flaw and a joke. Can anyone point me to any other high end planar or line source speaker manufacturer that uses such a design? I think ML went for form over function, and then when people started pointing out the issue and came up with a means of correcting it, only then did ML add adjustable rear spikes to their speakers and tried to play it off in their marketing as a feature. It is not a feature. It is a correctable design flaw.

 

[Rich]

The woofer acts like a point source, so its delay relative to the panel is exactly related to rake.

I'm certainly no engineer, but this statement makes no sense to me. What does point source vs. line source have to do with speaker delay and how could raking the panel back account for that difference?