Doc modding Marantz imperial 7

[karatestu]

My preference is the flat base speaker stand - KISS

Thanks Dave. KISS indeed - it is the least fussy and most elegant option.

It would seem most members have got tired of this saga and either don't bother looking or can#t be bothered to spend a minute to help me out. Oh well, such is life.

[CN211276]

I prefer flat based stands which provide more stability.

[karatestu]

I've been looking at tulip style chair bases. Looks a bit 70's but most are too tall. I need 20 cm height.

[karatestu]

I prefer flat based stands which provide more stability.

I know what you are getting at here but what about uneven floors ? A flat base would be more prone to wobble unless it was spiked. That's where three legs wins. My floors with carpet are flat I think but not exactly sure about that.

I like the single wide upright especially as if its hollow then I can load it up with sand which may help eat some vibrations before it gets to the suspended floor.

It's the swings and roundabouts of compromise again

[Toontrev]

I'll vote for 3 legs and ditch the tube. Part fill the large sphere and it should be very stable.

[karatestu]

Thanks Trev.

My wife's favourite is also the three legged version. She hates the 12" speaker basket version. I like 'em all so that's why I asked for opinions.

There's no clear winner but my wife must have the second say (after me of course ). My kids don't care - the closer it looks to BB8 from star wars the better

The other good thing about a single hollow leg is the wiring can run inside it up to the steel sphere. Not a deal breaker by any means, the cables can be strapped behind the back two legs or the speaker binding posts can be in the legs somehow I have to be careful with binding posts and a steel enclosure - don't want any sparks and nasty smells.

I am looking in to the cost of getting the spheres powder coated although they can't do plastic as it will melt so the top sphere would also have to be steel. They are available in that size .

[karatestu]

What happens to polar axis tilt with a semi omni with up firing mid bass and forward firing tweeter right above it in a sphere ? Rex ?

A conventional 2 way with tweeter has a lobe pointing downwards towards the floor. Put the tweeter at the bottom and the lobe is pointed up. Do a D'Appolito configuration (tweeter sandwiched between two mid bass) and the lobe fires straight ahead.

I can't work out what is happening in my case. The tweeter is above the mid bass so maybe is still points downwards

[CN211276]

I prefer flat based stands which provide more stability.

I know what you are getting at here but what about uneven floors ? A flat base would be more prone to wobble unless it was spiked. That's where three legs wins. My floors with carpet are flat I think but not exactly sure about that.

I like the single wide upright especially as if its hollow then I can load it up with sand which may help eat some vibrations before it gets to the suspended floor.

It's the swings and roundabouts of compromise again

I believe my floor is flat. The stands have spikes which dig into small mats on a wooden floor. I posted a picture of the lay out on the speaker stand thread last month. I have had the stands for twenty years. I think mass was the in thing then and it still is with me. They are filled with sand.

[r3xj0hn570n]

What happens to polar axis tilt with a semi omni with up firing mid bass and forward firing tweeter right above it in a sphere ? Rex ?

If wavelength at the frequency of interest (? 1kHz?) is much longer than the size of your sphere, it will pretty much flow out and around unimpeded. If it's near the same, you can expect diffraction in lots of directions. Either way the phase will not be altered.

A conventional 2 way with tweeter has a lobe pointing downwards towards the floor. Put the tweeter at the bottom and the lobe is pointed up. Do a D'Appolito configuration (tweeter sandwiched between two mid bass) and the lobe fires straight ahead.

The lobing depends strongly on your crossover.

[karatestu]

What happens to polar axis tilt with a semi omni with up firing mid bass and forward firing tweeter right above it in a sphere ? Rex ?

If wavelength at the frequency of interest (? 1kHz?) is much longer than the size of your sphere, it will pretty much flow out and around unimpeded. If it's near the same, you can expect diffraction in lots of directions. Either way the phase will not be altered.

A conventional 2 way with tweeter has a lobe pointing downwards towards the floor. Put the tweeter at the bottom and the lobe is pointed up. Do a D'Appolito configuration (tweeter sandwiched between two mid bass) and the lobe fires straight ahead.

The lobing depends strongly on your crossover.

Thanks Rex


Xover is 7kHz - acoustical roll off of the mid bass with first order tweeter high pass. I was going to try 1kHz and somebody else has suggested that on the SB acoustics thread on diyaudio. Means introducing an electrical low pass though.