Doc modding Marantz imperial 7

[Daniel Quinn]

Simple, use wood, then line with 6mm steel.

You can use the wood to cut holes and make nice cabinets then line it with steel.

In my last mods the wharfedales dovedales would have been to heavy lined solely with steel (especially as I only have 1 arm) so I used a combination of 6mm steel and 15mm acrylic.

[karatestu]

Hey Peter. I am trying to understand your plan Do you mean the tweeter on the front will be inward firing and the new one on top will be the front firing one ?

[Latteman]

Yes

[Latteman]

It's worth a go I reckon. At least the front firing tweeter will be behind the mid bass which is the most important part in my opinion.

[karatestu]

The first foam dice I bought turned out to be a bit too big (15cm3) so I found some which are 12 cm3 but still with the rounded edges. I think it's important to get these tweeters as close together as I can. You can't really go any smaller than 12 cm dice though because the magnets would be touching.

They arrived t'other day. Been busy hollowing them out with a hole saw It worked really well IMO. The holes are slightly too small but the foam will expand and clamp the tweeters in. They will probably need gluing in as well but we will see.



Obviously those holes will be hidden by the tweeter face plates. Mounting this pod above the main cab is requiring a bit of chin scratching for the best method both aesthetically and from the point of view that I would like to be able to turn it for toeing in.. I need a hollow metal tube for the wiring to pass down in to the cab below .

So why foam ? Cos they are available in the right size and shape and are cheap. It may mitigate the amount of vibration getting to the tweeter from the mid bass Or it could let the tweeters move around too much (although it still seems rigid enough even after hollowing it out) . I haven't a clue if this will work or not but that hasn't stopped me trying things before.

[karatestu]

Done a first application of dope on my new 6.5 inchers. Taking it slowly with these as I haven't doped one of these yet. Will need the add a little then listen method.

[karatestu]

Simple, use wood, then line with 6mm steel.

You can use the wood to cut holes and make nice cabinets then line it with steel.

In my last mods the wharfedales dovedales would have been to heavy lined solely with steel (especially as I only have 1 arm) so I used a combination of 6mm steel and 15mm acrylic.

Wood and steel is the obvious way to do it but I was trying to be clever with quartz tiles. They are only 10 mm thick but won't flex. i was trying to make the walls as thin as I could without losing strength. With quartz tiles I could have an external cube of 30 cm and have an internal volume of 22 Litres which is ideal for two 6.5 inchers.

I think it's called having your cake and eating it and I will probably fall on my arse with this at some point and revert back to wood with my tail between my legs. If only I could get a delivery slot with Wickes. They do some 60 x 30 cm samples for £2 each and you can buy more than one by the looks of it. Enough tile for two speakers for £12

[Latteman]

Hey Stu- well what can I say- have moved both tweeters from the front baffle to behind the bass driver mounted on a plywood baffle and blocked up the front holes.
They are as close to each other as possible and both firing forward as I don’t have the room on the top baffle for anything else.
The speakers, IMO were good before, now there is greater clarity and the detail is amazing- the mid bass has sprung to life and you can hear it is more involved in the presentation. Truly amazing suggesting moving the tweeters behind the mid bass.
The only downside is that I have to rebuild cabinets as theses are now hacked about and I look like I have 2 minions in my room

[karatestu]

They are as close to each other as possible and both firing forward as I don’t have the room on the top baffle for anything else.
The speakers, IMO were good before, now there is greater clarity and the detail is amazing- the mid bass has sprung to life and you can hear it is more involved in the presentation. Truly amazing suggesting moving the tweeters behind the mid bass.

Hi Peter. Glad you tried it and concur with my findings. I too found the difference quite amazing. But then who am I to actually come up with a good idea Well ok, I borrowed it from Linkwitz Pluto speakers.

You need to watch out for comb filtering with two tweeters firing in the same direction. You might not notice it though. If you are making new cabs then why not try and make room for having them fire in different directions.

[karatestu]

I tried only one tweeter behind the mid bass at first. It was clearly superior to one tweeter on the front of the main cabinet But being me I was too inquisitive about using four behind the mid bass that ultimately I arrived at the little tweeter cube pod that I currently have.

The strange thing (as you say the mid bass output becomes more prevailing) was I had to tweak the high pass filter on the tweeters to raise the xover frequency a bit (up to over 8 Khz now ). The tweeter's don't have much work to do but I still found that more of them was better. Even though the mid bass were pumping out over 8 Khz, the sound was not coherent without using a tweeter. I know I go on about reduced distortion from adding multiple drivers but it really works and I was surprised that it still holds true for tweeter's crossed over at upwards of 8 Khz.