Doc modding Marantz imperial 7

[Latteman]

[CycleCoach]

If you've got some rubber cement you can cut bigger tubes to any length (just insert one cut end inside the other) and while this is sub-optimal for riding, it will be fine for the low pressure stuff you want.
Just remember to have a valve in the section you want to use!

Racing tubes which are nominally 27" come in the narrowest widths (18 or 20mm) but you wouldn't want latex as it naturally leaks and would flatten over a couple of days. So in this case cheaper ones would probably be better.

I won't go in to too much detail here, but feel free to DM me if you want a bit more info.

Thanks again

I thought about doing two cuts and repositioning the valve to point outwards.

Do those thin racing tubes only come in latex then?

No: sorry I wasn't clear Stu. They come in both kinds (Country and Western!) so you just want the cheapest, which are butyl.

[karatestu]

Found these 700c sized tubes (29") in butyl and 18-23mm width.

https://www.amazon.co.uk/Nutrak-700c- ... 99V5H42

https://www.wiggle.co.uk/continental ... er-tube

And this rubber solution

https://www.amazon.co.uk/PUNCTURE-REP ... UE6&th=1

What do you reckon Coach ?

[CycleCoach]

Hi Stu,
the first ones look good (and cheap for five!)) the second is a very light one, and will do the job but it's pricey. And yes, that's the right glue. You can get them with shorter valves, but it won't make much difference to your build I think.

The secret is to rough up the surfaces to be joined with sandpaper (maybe a 1 - 1.5cm join would work?) spread the glue thinly (a clean finger will do, and then apply some pressure till it's dry (I would clamp the joins between a couple of bits of wood or similar.)

Good luck mate!

[karatestu]

250,000 views of this ridiculous saga now . Either people are genuinely interested, have nowt better to do or need a good laugh. Should make 200 pages before the end.

[karatestu]

Oh look a “band wagon”

Yep had to try it- the design of my speakers make the application of a 12” inner tube very easy- it’s different it’s positive it’s another Stu winner

So then Peter, how much music have you played since installing the inner tubes and has it all been improved ?

What kind of floor have you got?

Still waiting for the photo

[Latteman]

I have a concrete floor with wooded flooring on that.
Speakers are on mdf cubes - x2 high.
I’ve used inner tubes a lot but never on speaker bases- there is a certain clarity to the sound so much so the tweeters are more prominent and it’s not something I like- I was considering changing them anyway just not sure what with- I only use them so the diffuser can sit into the cone bringing tweeter & passive woofer as close as possible
Apart from that the bass is the most notable- strong and clearer - tubes are staying

[Latteman]

I have a concrete floor with wooded flooring on that.
Speakers are on mdf cubes - x2 high.
I’ve used inner tubes a lot but never on speaker bases- there is a certain clarity to the sound so much so the tweeters are more prominent and it’s not something I like- I was considering changing them anyway just not sure what with- I only use them so the diffuser can sit into the cone bringing tweeter & passive woofer as close as possible
Apart from that the bass is the most notable- strong and clearer - tubes are staying

Won't increasing the padding resistor value sort the tweeter problem out ?

I don't think your tweeter has to be close to the passive radiator as that is only producing bass with a big wavelength . You do need to get the tweeter close to the active mid bass though.

I have abandoned small dome tweeters because they just don't cut it with a first order high pass filter, even when crossing over as high as 6 or 7 KHz. I now use a small wideband driver for a tweeter which has a 2" cone and dustcap in the centre. It's one of the best decisions I have ever made and I kick myself why I never tried it sooner.

It can be used "full range" as it won't die without a high pass filter and the large dustcap gives it good dispersion af high frequencies. No ferrofluid to age and go hard either. I'm gonna buy some more of them.

[Latteman]

I have tried the padding resistor and am at 18 ohm and still feeling I have to go higher- I’ve popes some foam above tweeters and that has helped
The tweeters are Richard Allan CB4 cone drivers - very rigid cone with a lot of metal chassis- may try to dampen them as well

[Latteman]

Woah, 18 Ohms is a lot You either have a tweeter much more sensitive than the mid bass or the doping on the mid bass has lowered the sensitivity a lot or both. You could maybe try adjusting the high pass filter up in frequency a bit and see what that does (if it is the overlap region which is too prominent and not the high treble) . Or listen to the tweeters slightly off axis.

With my set up I have no padding resistor at all as the tweeter is about 86dB where I cross it over. Padding resistors increase the volume you need to give the driver as it increase Qes (electrical Q) and hence Qts = bigger box required for the same response. Also it reduces the damping factor of your amplifier - if you believe in it's importance.

Maybe you would be better finding a less sensitive driver for the tweeter if experiments don't yield any improvement in the matter.