Doc modding Marantz imperial 7

[karatestu]

There's much more to producing a true 1st order xover than just plonking in a series inductor and capacitor, apparently Thd impedance and phase of the driver needs flattening, the drivers need time aligning via stepped or sloping baffle. I have no problem with the mechanical time alignment but the other aspects require additional components in the xover and it quickly ends up looking like picture above of a Thiele 1st order. Doc would be having kittens looking at that.

So we should just do the best we can. Choose drivers with flat response up to at least two octaves out of band. Size of driver should be considered to avoid beaming - it honks. Power handling should also be considered. You can't take a dome tweeter down low.

Here is a graph showing the sensitivity of the ear against frequency. So about 1kHz stands out as a good place for xover. A small full range should have no problem crossing there first order.



But then I have to think about baffle step with a small 15cm sphere at that frequency. 115÷0.15 = 766Hz. I might just get away with that but the high pass may turn into a second order due to the baffle step loss. 1.2kHz maybe better. More research needed there. 6.5" mid bass won't be beaming at 1.2kHz. Shouldn't loose any sensitivity due to the power required at the frequencies the 2" cone will be covering.

[r3xj0hn570n]

Believe it or not the crossover below is 1st order. It's full of impedance correction, all pass sections etc. Is the result worth it ?

I've listened to Thiele CS3.6s many many years ago. Worth it? Definitely. They were being used with some large plinius amps, so there is that against them. I don't think they were all that amp friendly, but they certainly had a presentation that made most other speakers sound like transistor radios.

[karatestu]

Believe it or not the crossover below is 1st order. It's full of impedance correction, all pass sections etc. Is the result worth it ?

I've listened to Thiele CS3.6s many many years ago. Worth it? Definitely. They were being used with some large plinius amps, so there is that against them. I don't think they were all that amp friendly, but they certainly had a presentation that made most other speakers sound like transistor radios.

I am glad somebody who posts here has heard them. I am glad to learn that all the work involved designing it and all those components were worth it.

For diy enthusiasts like me with no measurement gear then such quality is unobtainable. I can only do my best with my ears. With a bit of luck it will turn out acceptable.

Rex, have you ever heard any Vandersteen or Green Mountain Audio speakers ? Both are advocates of first order filters.

[r3xj0hn570n]

Rex, have you ever heard any Vandersteen or Green Mountain Audio speakers ? Both are advocates of first order filters.

I may have heard Vandersteen's, but they didn't stick in my memory. Definitely haven't heard any Green Mountain Audio speakers. FWIW, i used to try to stick to 1st order crossovers in tweeters, but after numerous failure, then later measurements, it's become clear to me that it's not worth it. Only heroic tweeters like the Dynaudio esotar need apply.

[karatestu]

Rex, have you ever heard any Vandersteen or Green Mountain Audio speakers ? Both are advocates of first order filters.

FWIW, i used to try to stick to 1st order crossovers in tweeters, but after numerous failure, then later measurements, it's become clear to me that it's not worth it.

I totally agree having tried it myself and even at 6 or 7 kHz xover the result is poor with 1st order even at average listening volumes. I added more tweeters and it was much better in most respects apart from imaging and room reflections. Having now tried a very small full range I have abandoned tweeters for good. I can't afford the best tweeters and I would have no hope of designing a higher order xover either so tiny full range seems the best option for me. They generally have low sensitivity but scan speak have a few 3 inch full range cones with 86 - 90dB. I think I will try one of those.

[r3xj0hn570n]

I can't afford the best tweeters and I would have no hope of designing a higher order xover either so tiny full range seems the best option for me. They generally have low sensitivity but scan speak have a few 3 inch full range cones with 86 - 90dB. I think I will try one of those.

It used to be that one of the best tweeters (depending on your definition of best) was the vifa D27s. Are those still available?
Perhaps rebranded or something?

You don't need to perfectly match the sensitivity. A few dB lower will likely be better (a rising response is headache inducing), it's all in how that sensitivity is measured anyway.

[karatestu]

I can't afford the best tweeters and I would have no hope of designing a higher order xover either so tiny full range seems the best option for me. They generally have low sensitivity but scan speak have a few 3 inch full range cones with 86 - 90dB. I think I will try one of those.

It used to be that one of the best tweeters (depending on your definition of best) was the vifa D27s. Are those still available?
Perhaps rebranded or something?

You don't need to perfectly match the sensitivity. A few dB lower will likely be better (a rising response is headache inducing), it's all in how that sensitivity is measured anyway.

Is this it ?

https://www.falconacoustics.co.uk/ ... ter.html

[r3xj0hn570n]

Yep. Price has gone up.

[karatestu]

Yep. Price has gone up.

Post Brexit everything has gone up in this shit hole except the morals of our Government

[karatestu]

Well, you will never believe this but I think I have only gone and bloody cracked it

Took the B&W 6.5" out of their TL enclosures and transferred them to one of my crappy pairs of 30cm cube enclosures. This has never been done before. The cut outs are the same as for the cheap doped 6.5 inchers so they dropped straight in. Chucked some litre blocks of wood in to lower the enclosure volume and the rest (apart from close to the back of the driver was filled with some fibre glass insulation fluffed up .



The sound is transformed so I think a combination of pointing the driver upwards and filling the enclosure with fluffed up fibre glass has done the trick Cheers Rex, I think your suggestion about back wave coming through the cone was bang on the money. The bass hasn't been put to sleep like it has in the past when I have used too much open cell foam. I think fluffed up fibreglass is doing the business here.

The bass is even, articulated, fast and present in just the right quantity. I am a bit of a bass head if truth be told and this is doing the business. The blutack I have added at the junction of the cone and the dust cap must have lowered the Fs of this driver. One of the only parameters I know about these drivers is that the Fs was measured by Gramophone magazine at 40 Hz.

I bought a 60 gram rectangular flat slab of blutack and made sure I divided it into six equal sections before cutting two of the sections off, one for each driver. That means that approximately 10 grams of weight has been added to the driver. When modelled in winisd that does quite amazing things for the F3 and F6 in the bass (using the parameters of the cheap Chinese drivers I have). I have lost just enough sensitivity to mate with this 2" full range. I suspect the response is falling from the bass because that is the kind of sound I like.

It has much more speed, vibrancy, detail and just about everything else than the cheap drivers I doped. Response across the range is to my liking, bass is to my liking, it feels like real music very relaxing and enjoyable. I think my search for a suitable driver to mate with this 2" full range is over I'm well pleased.