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Author Topic: Another CII modification..  (Read 33064 times)
vesaII
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Posts: 84


« Reply #15 on: October 15, 2010, 07:34:04 PM »

Hello Stefan

Did some experiment with my little spekers with Peerless mids. Friend of mine calculated a zobel (one cap and resistor) for it to make impedance same all the way to 3000hz and new highpass according to lower impedance. Much better!

Your Seas also has much higher impedance at 3000. Zobel might help.

CII also have some peak around 40hz. At least if you put it in small room as i do. Issue i like to solve...

/V
« Last Edit: October 23, 2010, 07:29:03 PM by vesaII » Logged
Stefan I
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Posts: 141



« Reply #16 on: November 01, 2010, 08:49:33 PM »

Hello Stefan

Did some experiment with my little spekers with Peerless mids. Friend of mine calculated a zobel (one cap and resistor) for it to make impedance same all the way to 3000hz and new highpass according to lower impedance. Much better!

Your Seas also has much higher impedance at 3000. Zobel might help.

CII also have some peak around 40hz. At least if you put it in small room as i do. Issue i like to solve...

/V
Hi Vesa, in fact i use a Zobel Circuit to my midrange, and bandpass values is calculated based on that.
New smaller midrange enclosures is under construction, hope to be able to play them soon. The project has been passive during the summer..
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vesaII
Getting there
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Posts: 84


« Reply #17 on: November 06, 2010, 03:00:49 PM »

Hi

If you do it my way, you really need to double check things. And do not make parts too tight or you have problem with glueing.

Hope we see some pictures soon Smiley

/VK
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Stefan I
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Posts: 141



« Reply #18 on: April 07, 2011, 11:57:55 AM »

Time to put in some new information about this project Smiley.

I will start with some pictures to show how the work has proceeded.



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Stefan I
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Posts: 141



« Reply #19 on: April 07, 2011, 12:36:08 PM »

The crossover is also different since last, an Amplitud Parallel notch circuit is mounted on midrange to decrease energy in a decided area, in this case mostly between 600-1000Hz.
A Zobel circuit is seen under the speakerterminals.
Under construction everything looks very messy, it has to bee that way to make it easier for fast adjustments.





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Stefan I
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Posts: 141



« Reply #20 on: April 07, 2011, 01:06:40 PM »

Something fun is that despite very little is left from the original design, the sound is still a lot Snell i think, that indicates that my philosophy in reproduction is not very far from The designers, but with the new drivers the overall resolution is much better than original CII.
Especially the Scanspeak woofers is on a totally different level compared to original Peerless, i will describe it as they have a very good timing and is quiet when the signal say so, instead of a monotonous background rumble wich was significant with peerless.
I also have some thoughts about testing Ring Radiators from Scanspeak in the future to see if i can make it even better and more homogenus in the upper range.
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vesaII
Getting there
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Posts: 84


« Reply #21 on: May 28, 2011, 07:21:17 PM »

Hello Stefan!

Looks great and a bit different construction as mine. Diagonal is good idea, which i missed ;(
But in other hand your back wall have no support from mid-box as i have. Does it vibrate much if you try with hand?
Maybe it have no big influence, but i like to build cross support in every place it is possible. I even have five veneer things on lower end of cabinet end cross support bars between them all. Overkill just feels good Wink

As i understand you did not change anything else but only built a box for midrange?

Do you think it made a big improvement?

/V
« Last Edit: May 29, 2011, 08:16:34 PM by vesaII » Logged
Stefan I
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Posts: 141



« Reply #22 on: May 31, 2011, 11:47:12 AM »

Hi Vesa, yes i didn't fastened the midrange enclosure to the backpanel of the cabinet, it would be interesting to see how the cabinet behave with an accelerator, to see where the resonancefrequency is, and take decision from there.
Anyway it's a relative easy job to do if necesary, with rectangular clumps with tight passform glued outside each corner between the surfaces.

The result however is better i think, amplitude feels more linear in both bass and midrange and i have also taken away that original yellow fiber and tried some other stuff with a smaller dampfactor.

It feels like it's going to be real good when the Crossover is working properly, it still has some shortcomings, mostly in the crossing between midrange and tweeter, the most painful area for the ears if something is wrong.. Sad



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vesaII
Getting there
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Posts: 84


« Reply #23 on: July 02, 2011, 09:50:52 AM »

Hi Stefan

I try to collect power to do some necessary improvements to this uneven pair...
Have even plan to make it to two way + back tweeter Wink

And one thing is to get bass somewhat muted. Originally CII is 12/16 & 12/16.

What if i changed it to 16/12 & 12/16. At least it would make midrange a bit louder and midrange crossover more simple. In other hand it will make it more costly, but luckily we do not need to ask P. Snell's opinion of this Wink

You have not explained your crossover yet...? At least i am curious to know what you have found on path.

Best,
/V



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Stefan I
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« Reply #24 on: July 02, 2011, 01:14:11 PM »

I see your point in 18/12 & 12/18, a disadvantage though would be bigger coilvalues on Lowpass compared to 12db, but it is definitely worth a test.
Regarding the crossover i have mostly worked with adjusting crossover points and ouput levels, ones i tried 18/18 on midrange but went back to 18/12 because of an experience of some lack of dynamics.
Later on i was adding that amplitude circuit to get rid of what i thought was a peak in the upper midrange, and moved it a bit up and down to find the right frequency for it.
Next up will be to lower one crossoverpoint in midrange, to increase balance between lower midrange and upper bass.

Whats your plan for a two way system? Can you explain the design?

It is always difficult to explain with words whats happening when you don't have the possibility to measure things after adjustments, anything comes out to experiences only.  /Stefan
« Last Edit: July 02, 2011, 01:21:21 PM by Stefan I » Logged
vesaII
Getting there
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Posts: 84


« Reply #25 on: July 03, 2011, 08:41:34 AM »

Two way idea is to replace tweeter and current midrange with small Scanspeak 10F8424G00 fullranges i have http://www.snell.no/forum/index.php/topic,1292.0.html And drive them with 18/12 & <300Hz + back tweeter.

First i will get two cardboard box or big baffles of feneer just to hear if scanspeak really is better than these very nice Audax carbon fibres have now.

Maybe we also should learn to use at least microphone to find peaks...

/V
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Stefan I
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Posts: 141



« Reply #26 on: July 03, 2011, 11:07:47 PM »

I understand, the crossover will be much more simple that way and thats good, the backside is that you get bad off-axis performance when using the midrange in fullrange. But if you tolerate a smaller sweetspot it's not a big problem, but for me i want the dispersion to be as smooth as possible.

By the way, after years with discussions i still don't know your position? Mine is in Sweden. Smiley

Quote
Maybe we also should learn to use at least microphone to find peaks...

Absolutely!!

« Last Edit: July 03, 2011, 11:13:57 PM by Stefan I » Logged
vesaII
Getting there
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Posts: 84


« Reply #27 on: July 04, 2011, 05:57:51 PM »

Yes, bad part is bad off-axis and one nice thing with Snell's is just good off-axis.

But it i like to try and see how bad this issue will be. Scan-speak 10F/8424G00 have so light cone, even less than the praised mid in AIIIi, i cannot resist. Can also happend that i get those original AIIIi midranges and put them in CII, if Scan-speak sound is no good  WinkWink http://www.seas.no/images/stories/vintage/pdfdataheet/h143.pdf

Quite likely i will go back to 3-way, only with higher x-over frequency or 3000 to get best off-axis.

Actually CII:s are bought from HifiKlubben Sthlm when i lived there at -80's av min kompis Jakob Smiley


/Vesa
Helsinki
« Last Edit: July 04, 2011, 07:10:43 PM by vesaII » Logged
javilha
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Posts: 440



« Reply #28 on: November 06, 2011, 12:50:25 PM »

Why did you just sell the C2 if they don't sound good in your ears?? It's a very sad thing to see how you are spoiling them totally. Or from the bottom, built a complete pair of speakers you own, instead of doing this.


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vesaII
Getting there
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Posts: 84


« Reply #29 on: November 06, 2011, 09:05:38 PM »

We do not have market here for 20year old speakers with name Snell.

And they had become quite outdated.

And cause i cannot keep my fingers out of these things.

And cause of building a decent cabinet is too big effort.

And cause of i am a heretic and prefer good sound over history.

Sorry
« Last Edit: November 06, 2011, 09:36:49 PM by vesaII » Logged
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