Doc modding Marantz imperial 7

[karatestu]

I wonder why Linn felt the need to feck it up ?

Not having done it wrong, i don't have anything to compare it to.

Maybe i should try it the wrong way then i will know just how wrong Linn got it - isobarik's and sara's. I believe Linn fecked it up the most with the sara's because they are only a two way and so have isobaric mid range which is not a good thing.

Ummm - Cubix have isobaric bass-midrange too.....

The only thing Linn did wrong with 'Briks and Saras was choice of drive units, especially the KEF B200 in the Sara and B110 in the Isobarik, which are inclined to screech if not properly crossovered or PVC doped and depending on the batch used as they varied a heck of a lot! Not sure what other drivers were around back then that they could have bought in quantity.

Saras and 'Briks were TWO KEF-KITs in a box and offered a three ohm load in the midrange to prove it! the tweeters were far more expensive than T27's though but in my opinion, not really better, although going active helped the 'Briks to sound far better depending on the generations of amps used... Falcon made the crossovers but I don't know how different they were from the KEF originals. Good wiring was used inside and the Sara boxes with radiused edges were superbly sealed and finished - copious amounts of a foul tar like substance was used inside and all over the driver chassis too to seal the boxes and drivers up, the 'Briks getting better cabinets as the years went on. I could go on, but it's not worth it here.

I believe the doc heavily dopes the inner 8 incher in the cubix so only the outer one produces midrange. A way of getting around the problem ? If there is in fact a problem at all ?

[Dr Bunsen Honeydew]

There is no problem.

[_D_S_J_R_]

My big bass cubes are made of chipboard. If what you say about the improvement with briks going from chipboard to mdf then i am in for a real treat when i do the final build in baltic birch ply. Maybe some steel too.

Not your problem but Linn's... The active 'Briks in chipboard had more effort put into them and could sound better for it. The change to MDF which improved cabinet consistency (I was told) helped improve the passive ones, but the actives didn't change hugely for the better I recall. All ancient memories now of extremely 'marmite' products and nothing to do with what your doing, so enjoy... I mean, all this spiking to the floor and for years, nothing done about the 'boooooiiiiiinnnnnngggggg' vibration in the stands if the speaker was tapped sideways...

[karatestu]

There is no problem.

I will stop my obsessive worrying then

My big bass cubes are made of chipboard. If what you say about the improvement with briks going from chipboard to mdf then i am in for a real treat when i do the final build in baltic birch ply. Maybe some steel too.

Not your problem but Linn's... The active 'Briks in chipboard had more effort put into them and could sound better for it. The change to MDF which improved cabinet consistency (I was told) helped improve the passive ones, but the actives didn't change hugely for the better I recall. All ancient memories now of extremely 'marmite' products and nothing to do with what your doing, so enjoy... I mean, all this spiking to the floor and for years, nothing done about the 'boooooiiiiiinnnnnngggggg' vibration in the stands if the speaker was tapped sideways...

Thanks for your input Dave. I don't like the fact that my bass cubes are built of chipboard (finest ikea chipboard) and wonder what they will sound like when built out of something much better. My smaller cabs with mid & tweeter in are made of real pine for sides, top & bottom and chipboard for baffle and back panel.

The final build will likely be a different shape too and i have not decided on one or two box design yet. If one box it will probably have sloping sides like steve's metronome design. Had the idea of using a cast iron pipe with one end capped off for the mid enclosure which runs from the top panel down towards the bass drivers. Length would depend on cabinet volume required. A bit of experimenting there would be fun. I thought the mid pipe enclosure down the centre of the bass enclosures may help with standing waves. Not sure on this idea yet.

Doc's doped drivers and the visaton really are as sweet as a nut and could never be described as squakers. The doping surely stops any nasty break up and spikes in response so no worries on that front.

[Dr Bunsen Honeydew]

The pipe will make it worse, I tried it nearly 30 years ago. A one frequency horn = honk. You keep going on about cab internal standing waves, forget it!!!!

[karatestu]

The pipe will make it worse, I tried it nearly 30 years ago. A one frequency horn = honk. You keep going on about cab internal standing waves, forget it!!!!

Thanks for saving me the bother doc.

I dont know why i keep going on about standing waves.

[Dr Bunsen Honeydew]

Probably because "standing waves" is just another forum bullshit. We used to have a lovely word for this forum techno babble. Where they take a technical term or word they don't understand and just use it out of context. Marco and Jerry were hilarious with it. Taking the piss out of them here has largely cured them. It started with the magazine reviewers inventing things to say to pad out boring reviews.

I forget the piss take phrase we used to use to describe them, anyone remember. And of course Marco's fav one that used to come out in every other post explaining why plugs shouldn't have metal in them, etc in his case probably true as silence could well be better than that valve PA system in a broom cupboard, sadly you need metal to conduct electricity. Anyone remember that bullshit phrase as well.

[karatestu]

Yes, that's probably it. Too much reading of nonsense on my part and it has stuck in my head.

[Geoff.R.G]

Probably because "standing waves" is just another forum bullshit.

I suspect it has something to do with not understanding radio. In the days when almost everybody had a tuner one would occasionally see reference to VSWR (Voltage Standing Wave Ratio). Probably someone latched on to the Standing Wave bit and decided it would apply to any wave. Indeed standing waves are possible in sound and radio contexts as well as water but, unless you are in the habit of playing test tones through your speakers, it just isn't going to happen.

[karatestu]

Thanks Geoff. I sometimes obsess about things i shouldn't. I am an over engineering, belt and braces kind of guy.