My dipole experiment

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#161
Hi Ted,

By "Blast them" I meant - repeatedly running them up to maximum excursion at LF, say 20-30Hz.

Hi Simon,

Good to hear that your reproduction is becoming more integrated now.

I have an open wound reel of copper wire into which I can insert a ferrite rod to tune it exactly where desired. Covers something like 3 to 6mH - very useful.

Now that you have better sound with the T-bass and simple series choke, it would be interesting whether you then hear the independent peak and phase shift which a capacitor introduces if a series damping resistor is not included; this being one of the main weaknesses of simple 12dB/oct crossover circuits !

Are you taking yours to the audio meet ?

Cheers ........ Graham.
 
#162
Graham Maynard said:
Now that you have better sound with the T-bass and simple series choke, it would be interesting whether you then hear the independent peak and phase shift which a capacitor introduces if a series damping resistor is not included; this being one of the main weaknesses of simple 12dB/oct crossover circuits !

Are you taking yours to the audio meet ?
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Well I didn't ever like the sound with a cap (multiple) across the woofers, although it measured appropriately in ARTA. I never tried a series resistor though, but I will be trying 2nd order again (higher uF this time) and I can insert a series resistor and try with and without.

What value series resistor should have the desired effect?

Which meet, the northern/Chesterfield one that keeps getting delayed? Yep, they'll be present for sure. Even if they're not high end, they're superb for the low cost.

Will you be making it? And with monsters??

Simon
 
#163
If you had a peak with the capacitor, you probably constructed a filter with a very high Q. In that case you should try a smaller capacitor instead of a bigger one. Or a bigger inductor. Or both.

The series resistor is a question of experimentation, because it influences the filter's Q and steepness. Reasonable values are up to around 20 Ohms. Start in the middle with 10 Ohms and then step ~5 Ohms up and down from there. Then again ~2,5 Ohms up and down from the value you found better. And so on.
 
#164
Hi graham, I did try that with the baby brother of these drivers and popped one straght out of the voice coil.
Still if I do it with less than full output I suppose it will help to loosen drivers up.

Simon you could try strange second order low pass if using large cap values put the resisor in series with the cap in the return signal path.

Cecile is going home to the state to see her first grandchild SOOO! I may present her with a "fait accompli" if I can afford the baffles of course
 
#168
pacificblue said:
Does that mean you've finished these?
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lol, I think so.... bar a smidgen of final tweaking. They sound excellent, but tweaking might address the final minor issues:

* slightly nasal mid quality / lack of weight on guitar and piano
* slightly too overlapping woofer response

I am happily enjoying loads of music through them and had a friend over today, who closed his eyes and commented on a simple recording as being "believable, it's basically in the room". The recording was made on two quality microphones positioned in the "near-coincident" position and recorded in 44.1/16 and put on CD with no mastering. It was just a saxophone in a large performance room. It was made by my younger brother, who is doing a degree in Music & Maths!

He was, however, less impressed by Clapton Unplugged, complaining that acoustic guitars somehow didn't sound real, in spite of excellent detail levels. We also enjoyed Jazz at the Pawn Shop, several Michael Jackson CDs and Dire Straits.

I also fired up a drum kit recording and Robin S - Luv 4 Luv from "Soundcheck 2", which were stunning through these!!! His only complaint was real cymbals sound harder... Of course dome tweeters can't quite sound like a real cymbal, so there's nothing I can do about that. We also both agreed it would be pleasing to have the kick drum pressurise the room, but the effect wasn't missed when I turned the volume to 3 o'clock 😉

I think it's worth spending a little more time taking them a step closer, then ultimately I'd like someone to put them to good use (near cost price to get rid of them) to make way for the next set!

Simon
 
#173
Whatever level you adjust/optimise a LS at, that is the only level at which it will sound correct, especially at LF.

Turn the level down and the bass will 'disappear' most.

This is has nothing to do with pressurisation because it is down to our hearing.

This makes me wonder though, do we notice a loss of free wave more than pressure at LF ?

Cheers ...... Graham.

PS. Before you cut the driver do try the simple foam roll (4" paint roller foam rolled off the former after boiling water used to soften the adhesive) right in front of the lower half of the duscap.
 
#175
Will look into foam rollers Graham!

I heard some CSS FR125s today on top of 2 x 12" Celestions.... Not sure I want to go the CSS route now - too recessed / dead for my ears. I'll discuss that in my new thread. The Celestions went lower and with more slam than my 7" drivers though, so I might look at getting some. Supposedly they have an FS of ~22hz and Qts of 0.3.

Simon
 
#177
It's very hard to describe how they sounded (referenced against modified Jamo Concert 8 - Seas Excel drivers). They do everything basically well and sound smooth... but there's no pizazz, no sparkle, no presence, no life!! They were very uninteresting next to the Jamos. They might make a great midrange driver though, matching easily with any tweeter because you could cross over very high (5khz or higher would be no issue whatsoever - it's just there for that sparkle / brilliance).

Simon
 
#179
SimontY said:
It's very hard to describe how they sounded (referenced against modified Jamo Concert 8 - Seas Excel drivers). They do everything basically well and sound smooth... but there's no pizazz, no sparkle, no presence, no life!! They were very uninteresting next to the Jamos. They might make a great midrange driver though, matching easily with any tweeter because you could cross over very high (5khz or higher would be no issue whatsoever - it's just there for that sparkle / brilliance).

Simon
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It was great to see you again Simon. Always nice to get another opinion.

I'm going to play around with the cutout for that css, as the mids are "cuppy" sounding. I also have two spare Vifa tweeters which I may try adding and crossing in high as you suggested.

Cheers, Lee.
 
#180
Thomo said:



It was great to see you again Simon. Always nice to get another opinion.

I'm going to play around with the cutout for that css, as the mids are "cuppy" sounding. I also have two spare Vifa tweeters which I may try adding and crossing in high as you suggested.

Cheers, Lee.
Click to expand...

It's got to be worth a try mate. In the meantime I'll concentrate on anything that I can do to polish off these current speakers. And I may buy some Celestion 12" woofers!!

Simon
 
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