Compact monitor

[johanwholst]

Thanks a lot again Pos!

Sorry for the off topic

[sebackman]

Dear all,

I think POS ideas should work very well.

I also received some questions on the anti-vibration feet.

I think the company I used to calculate has been sold and the site is downsince many years. However, I think this may be where they winded up.

http://www.hutchinsonai.com/company/index.cfm

Here is another company that should be able to help.

http://www.gmt-rubber.com/

I don't know who makes the ones I use, as I buy them locally and have actuallynever asked. They just happen to have dampeners with similar function as theones I calculated.

The ones I use are 50mm diameter, 36mm high and made with 40 shore rubber (soft). Theyhave a built in metallic plate covering one end and with a M10 bolt hole formounting. I typically bolt them to the speaker using a sheet of standard anti vibrationrubber mat in-between the foot and the speaker. The mat is thinner (6mm) and absorbs adifferent frequency spectrum.

I have read somewhere that the mounts recommended for aircraft, are all-attitude,with resonant frequencies of 15-30Hz, and 1:1 stiffness in alldirections. The mounts for helicopters are 7-10Hz, must be mountedhorizontal, and have stiffness ratios of around 4:1. They are much looserside to side than up and down.

So are my speakers. You can sit on the subs without problem but can also swaythem from side to side with only one finger. A bit odd but it works very goodindeed.


POS, no extra drilling. Just very slow turning the tapand empty the hole many times as you go to avoid loose plastics jamming the finished threads. I typically did 5-10 mm and the outwith the tap and clean the hole with compressed air. Takes a bit of time butthe threads are perfect and very sturdy. I did the threads all to the bottom in the holes.
You can borrow my extra long M6 tap if you want. Shall Isend it to you in an envelope?

Kind regards

//Robert

[pos]

POS, no extra drilling. Just very slow turning the tapand empty the hole many times as you go to avoid loose plastics jamming the finished threads. I typically did 5-10 mm and the outwith the tap and clean the hole with compressed air. Takes a bit of time butthe threads are perfect and very sturdy. I did the threads all to the bottom in the holes.
You can borrow my extra long M6 tap if you want. Shall Isend it to you in an envelope?

I did already tap one of the two horns my M5 taps, so it would probably be better to redrill it to 5mm to remove any trace of the old thread.
Or should I just retap it?

Thanks for the offer on the tap.
I had a lot of difficulties finding a long enough tap, or more precisely thin enough, because for some strange reason 99% of the taps out there have a rod that is larger than the internal part of the thread (and sometime even larger than the external one!), so you cannot go very deep.
The rod must not exceed 4.2mm for a M5 tap, and 5mm for a M6 one.
I finally found good/thin taps in a very specialized shop, so now I am all set

[pos]

So are my speakers. You can sit on the subs without problem but can also swaythem from side to side with only one finger. A bit odd but it works very goodindeed.

I tend to do the same thing, but this remark from GT got me worried lately :

The trick is to get something that doesn't rock or tip. You will eat the bass kick immediately if any enclosure movement is allowed. The woofer kicks really hard and if any energy is consumed moving (rocking) the enclosure due to it not being properly coupled to the floor, you will lose bass kick and impact. The proper use and need for spikes (or equivalent) is not BS. It is based in sound theory and is easily demonstrable.

[sebackman]

Hi,

Well, who am I to question the master. That is probably the norm and correct in an overwhelming majority of the cases.

But what I can say is that my subs are sealed 70 lite cabs (one SUB1500 driver in each cabinet fed by 1100W RMS each) with very thick walls and sturdy bracing and even if I play very loud they are completely still. No movement what so ever. But you can still move them with your finger. You can balance a quarter on the edge on them when playing "full throttle".

I have no idea why it works, but it does.

POS, I had to make a tap to get it long and thin as you mention. Good that you found a finished one, I never did.

Kind regards
//RoB

[sebackman]

I just got the WG's back from paint. A bit of a bumby ride, they had to redo them several times.... Now they are textured black (black is such a happy color) .

Tomorrow the will mate with a fresh pair of 2450SL/476Nd and go into the Compact Monitor.

Amps are also ready to go to work.





Have a nice weekend

//RoB

[pos]

It looks really nice!
I prefer this texture to the original, and it is probably also more solid...

[bubbleboy76]

Nice!

I will not do any anatomical jokes on the M2-horn. I did it on the Buttcheek-horns, and on the Array-horns, but with the M2 it is not funny any more!!

[sebackman]

Dear all,

Slowly getting there. Mounted one WG today and it was quite difficult to adapt the gaskets to get a smooth surface. Tomorrow I will try to adjust the port lenght.

Kind regards

//RoB

[Odd]

Snyggt!

[sebackman]

 
Dear all,

The HW part of the project “Compact Monitor” is done. Did not really turn out exactely as planned, but close enough. Attached are some pictures on the final result.

There were some questions earlier on the LE1400H and I have not used them before. Attached is a measurement from them in the 75 litre “Compact Monitor” cabinets. They are ported at 30Hz (measured). The curve is a combination of the dual ports, near field and far filed. MLS measurement with calibrated mic and no smoothing! Look pretty darn good to me.

The waveguide is attached with M6 machine bolts from the inside. That was tricky. Sealing was crucial as the WG are not level in the back. There is a picture of the sealing and the result.

We also had a discussion on spikes or soft feet and just for the fun of it the last picture shows a coin balancing on top while playing some country music at roughly 200W peak. They are completely still.

Kind regards
//RoB

[sebackman]

[sebackman]

[sebackman]

Ok. The small VTX clones are done. The M2/LE1400H Compact Monitors are done.

Now I'm setting up amps and XO for them. Crowns and BSS as usual.

Next task will be the new HT speakers with modified M2 WG's. I have already milled out for the 045Ti-1 drivers and K2 9900 horns. The woofers will be1400PROS's and in order to reduce baffle width I decided to make them as narrow as I can. They will be wall mount and a small baffle will be more esthetically pleasing.

I was a bit worried to put the saw blade into them. To be sure they would not move I built a jig and built some support for my adjustable circle saw. Only the first one is done but it worked out just fine and I’m taking of 36mm on each side.

The material is a bitch, it is some kind of glass and just kills the blade. I’ve got a pretty decent machine but can just go 1-2 mm per pass to not get to hot so the plastic melts. I did a first try run to confirm and then took the plunge.

More info will follow.

Kind regards
//RoB

[pos]

Wow, very impressive as usual!
Looking forward to seeing the result!