Doc modding Marantz imperial 7

[karatestu]

Stu box positioning challenges aside, are you rating front firing 12" as better than up firing

I don't know. I have problems arranging the two cabs to get the 5" and 12" both firing up. Doc put the 5" side firing and 12" up firing. I cant try that combo with what i have at the moment. New enclosure would be needed.

What i can say is i prefer front firing 12" to down, side or rear firing. And i prefer up firing 5" to side firing (in or out) with the 12" in any of the firing directions i have tried.

[Latteman]

P&S is ok at the moment but not sure of the reason- driver config, wiring etc etc.
I have also reverted to Richard Allan tweeters which I seem to prefer over the soft dome modded doc tweeters- got an earth hmmm I can’t trace at the moment which is driving me crazy

[karatestu]

Earth hum ????? I feel your pain Hope you get it sorted. What changes led to the hum being introduced ?

I use the Visaton G25ffl tweeters not the Chinese ones that Doc doped.

[karatestu]

Looking at the frequency response graph for the visaton G25ffl it has a rising high end response above 8Khz between 2dB and 4dB.



I think this backs up my tendency to prefer listening to the tweeters slightly off axis. Currently they are firing straight forward from the wall with 0 deg toe in. More side wall reflections with no toe in though so no free lunch here. Another trade off.

[Latteman]

Earth hum ????? I feel your pain Hope you get it sorted. What changes led to the hum being introduced ?

I think it’s from the older A60, the case has a hum feeling if u know what I mean- trying to Earth the case has no effect- the earthing is very different to modern Nva- there is direct interconnects to each amp board for input from pre amp with the speaker outputs the only common earth link- will try removing the power on off button and direct wiring tonight in case it’s the button

[karatestu]

Have u messed with passive radiators yet

You know you can make a passive radiator out of an old unused driver ? You can tune it by adding mass, wiring resistors and capacitors across the voice coil even though it is not even connected to any amplifier

[karatestu]

I think my further experiments are going to require the buying of another 5" driver and the doping thereof. Then i can remove the little cuboid enclosure from the set up completely.

One 5" back wave into each isobaric compartment of my big bass cube to keep things equal. Both 5" up firing or one up firing and the other side firing. Tweeter could go on the existing front facing baffle of the big cube or a little extension that is attached to the top.

That way i could use blanking plates for unused holes and compare all sorts of permutations. I might have to revisit up firing tweeters and try a side firing one. Could go on forever this one

[karatestu]

I am using this thread as a kind of diary to help me with finding information etc. So a few links to interesting or helpful information

http://techtalk.parts-express.com/forum ... ve-rolloff

http://madspeaker.com/Appexamples.pdf

[karatestu]

https://www.diyaudio.com/forums/multi-w ... eters.html

[karatestu]

https://www.diyaudio.com/forums/multi-w ... -mass.html