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Old 1st November 2012, 08:24 PM   #51
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It was easy in my case as I designed an MTM, So I just measured on axis with the tweeter (which was also the listening axis) . Thanks for the correction wolf and dumprtuck Whilst I had done measurements on my old three way, they were crude and not subjected to the rigourous simulation and comparison I did with my MTM.

Tony.
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Old 2nd November 2012, 11:19 AM   #52
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Quote:
Originally Posted by system7 View Post
Lynn Olson on the problems with first order filters and "LGWAG" speakers:
Can you have sparkling treble but without sibilance
All his posts in that thread are enlightening as usual.
That thread is a goldmine Lynns posts in that thread led me down the path that changed my crossover such that my speakers went from pretty good on simple material to excellent on most material. I think the areas he touches on with respect to slew rate and analog electronics probably account for the remaining areas of deficieny in my system.

I've just been re-reading some of the posts, and the one where he mentions DCR on shunt coils on the tweeter crossover was also an eye opener. How many times have you read that you can use a small gauge (ie high dcr) coil for shunts on tweeters... bzzzz wrong. see this post for his reasoning Can you have sparkling treble but without sibilance (actually mentioned first by simon in post 46)

Well worth a read of the thread. Posts 17, 37, 42, 44, 46 and 48 probably had the biggest influence on my design changes, but there were heaps of good posts in between as well.

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Old 17th November 2012, 05:25 PM   #53
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Ok...finally got in some parts...yeah!!!

Built the xover based on what Steve suggested...subsituting a 1.5mH on the Morel...and using a 4.7ohm resistor inline on the tweeter side...tweeter is wired as the diagram suggests...out of phase...which is supposed to put it back in phase witht he woofer I'm assuming??

Sound is really nice at the moment...it's changed a few times but I can see that with new parts...it's starting to have a more pinpoint soundstage...

Voicing and tone are very nice...nothing is exaggerated...so far LOL!!!

Bass is nice and as tight as I would want it...it still has that warm touch to it...great on jazz!!

So Steve...what is the actual xover point now of this design??

Thanks again for all your help!!

Dave
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Old 17th November 2012, 05:51 PM   #54
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the 8R2 tweeter paralel res lowers impedance
means your 4.7uf series cap cuts higher
and together with the quite large 2mH woofer inductor cutting low.....?

try placing tweeter series res on the other side of cap, getting impedance up again
being able to use smaller cap is one of the nice advantages of a series res att

I would expect tweeter polarity should remain reversed
unless other weird things are happening
maybe also try to tilt the hole speaker
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Old 17th November 2012, 08:56 PM   #55
system7 is offline system7  United Kingdom
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I modelled the tweeter fairly carefully, as it goes, Tinitus:
Need help with a xover please...

1.5mH and 4.7R at the input to the tweeter filter should all be doing the right things here. It's a 3kHz crossover, low order as requested.

Dave, this all sounds excellent. Lining the top, bottom and sides of a bass reflex with stuck-on damping material is my current wheeze for the smooth sound. You'll want a bit of fluffy wadding at the back panel too. Not enough to mess up the airflow for the vent though.
Upgrading Mordaunt Short MS15 Bookshelves

IF you want to experiment further to remove any residual cone breakup harshness from the woofer, you can shunt a 8uF across the bass and swap the tweeter phase. An additional 10uF on the tweeter gets its response and phase better too. You see, I was thinking ahead here.
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File Type: jpg Morel_HU_621_frequency_Response.JPG (45.6 KB, 50 views)
File Type: png Morel_Trial_3rdOrder.PNG (10.9 KB, 48 views)
File Type: png Morel_Trial_3rdOrder_FR.PNG (20.7 KB, 46 views)
File Type: png Morel_Trial_3rdOrder_Phase.PNG (19.3 KB, 47 views)
File Type: jpg Mordaunt_Short_MS15_Wadding_and_Damping.jpg (88.2 KB, 17 views)
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Well, there it is! Best regards from Steve in Portsmouth, UK.

Last edited by system7; 17th November 2012 at 08:58 PM.
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Old 18th November 2012, 10:54 AM   #56
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Morning Steve

Lining...yes...all sides have some covering on them

I'm going to give these guys a good 50 hrs of playtime before I really sit down and see what they are like!! First impressions are really good though!!

And looks like you were thinking ahead LOL!!

Will report back in a bit!!

Toodles!!
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Old 18th November 2012, 11:03 AM   #57
system7 is offline system7  United Kingdom
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Good project, Dave. You'll doubtless be getting a better result on first order bass than I got with a paper woofer on my Mordaunt Short MS 15 speakers. The advantage of polycones!

Frankly, that tweeter has the oddest frequency response I have ever seen. But I expect Visaton know what they are doing.

Are we going to get some pictures?
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Well, there it is! Best regards from Steve in Portsmouth, UK.
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Old 18th November 2012, 11:19 AM   #58
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Pictures?? ROFL!!

They are in ugly cabinets that I reused with a different front baffle...leftover from a set of broken Tangent TM3's!!

K...you asked for it

These are what I've been using to "test" out drivers...lots of different baffles have been put on LOL!!!

Right now...xovers are just laying nicely on the bottom of the box...

Ok...so with the addition of those two caps, I should get a better relationship between the two drivers at the xover point correct??

BTW...that tweeter...I think it's one of the best cheap tweeters I've heard...but I've never had a Morel tweeter in here although I've heard them and I very much like them...but there is something about this ceramic Visaton that's hard to give up...and if you get a chance to hear one you'll see why...it's effortless in it's production of sound...you can't make it sound bad...at least I can't here...even with that simple RC in series and nothing on the Morel, it sounded good!!
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Old 18th November 2012, 11:38 AM   #59
system7 is offline system7  United Kingdom
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Very nice indeed. Seriously. A box is a box.

You have to be the judge of when you are happy with the final result. First order bass polycone and second order tweeter is a classic setup used on the original KEF Celeste. Going higher order raises problems like the dreaded 1kHz midrange shout with polycones.

I am currently delving into low distortion tweeters. The Non-ferrofluid SEAS 27TDC is liked by Troels Gravesen. It certainly has a nicer frequency response than the Visaton, but hey.
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Old 18th November 2012, 11:49 AM   #60
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LOL Thanks!!

See...that's what I was trying to achieve...I love that British sound and the way they did things...my final build box will be like a Harbeth or Spendor...nothing fancy...just that classic look

Here is that Tangent info:

http://www.thunders.ca/tangent/tm3.php

As for the SEAS...I had this one a couple of times:

H1189-06 27TDFC

No matter what the specs and charts say, this ceramic tweeter is the cat's meow!! That SEAS doesn't even come close in the quality of sound...

Think of it like Morel...if you go strictly by the specs, one would think it would sound ugly...but Morel sounds damn fine as you've already stated...

You can't always go on specs alone!!
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