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Multi-Way Conventional loudspeakers with crossovers

Problems with Scanspeak Illuminator 12MU/8731
Problems with Scanspeak Illuminator 12MU/8731
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Old 19th September 2015, 08:31 AM   #21
Lojzek is offline Lojzek  Croatia
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Hi Mercury,

could you post a separate measurement of both midranges in parallel low
passed, then the tweeter high passed, and finally their sum without moving
the mic and leaving like 1 m away from speakers at the tweeter axis
(about the listening height)?

Measure only one channel. Try to present the mid LP and tw HP in the same
graph.
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Old 19th September 2015, 08:39 AM   #22
Mercury3 is offline Mercury3  United States
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Quote:
Originally Posted by Lojzek View Post
Hi Mercury,

could you post a separate measurement of both midranges in parallel low
passed, then the tweeter high passed, and finally their sum without moving
the mic and leaving like 1 m away from speakers at the tweeter axis
(about the listening height)?

Measure only one channel. Try to present the mid LP and tw HP in the same
graph.
Yep I can do that. I work 12 hour shift so might be a few days again when I have another day off.
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Old 19th September 2015, 08:47 AM   #23
Mercury3 is offline Mercury3  United States
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Quote:
Originally Posted by rabbitz View Post
I thought that 1.5V max batteries were normally used for phase check (it was decades ago).

Drivers don't like DC voltages as witnessed when amp rails voltages come through from an amp failure.

Since you are running active, just try a DC blocking capacitor about 100uF in series to the +ve terminal of the mid driver just in case some DC is coming through from the electronics.

I can understand you wanting to throw in the towel as it's very frustrating. Try returning the drivers as they are too expensive.

You could have a look around for other designs using these mids and even talk to the designers for some opinions.
Okay I'll order a couple of 200uF caps. That'll give me low enough frequency I'll just leave them installed. I think can't hurt and the tweeters already have one.
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Old 19th September 2015, 10:28 AM   #24
andy19191 is online now andy19191  Europe
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The driver is used in some good speakers and so the problems you describe are not going to be due to a design defect. You might have incorrectly manufactured drivers but it is unlikely. The most likely cause is an implementation issue.

"Very expensive tube amplifier" could be the source of a lot of problems. I would recommend replacing it with any reasonable class AB solid state amplifier while performing the diagnostic tests. If the impedance of your previous setup was different to the roughly 4 ohm load you now have then you cannot reasonably draw the conclusion that the valve amplifier is not the source of the problems.

You seem to be describing something like a resonance but are showing heavily smoothed plots which are not going to show resonances. I would suggest changing your measurement setup so that you can first see the problem and then try to work out what is causing it.

When you listen to the midrange alone do you include the low pass filter? The cone is fairly hard and so the breakup will need attention.
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Old 19th September 2015, 10:31 AM   #25
Mario Pankov is offline Mario Pankov  Europe
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Problems with Scanspeak Illuminator 12MU/8731
I have a few questions:

- have you got off axis measurements, up to +/- 75 degrees in 5 degree increments would be sufficient
- how close to walls or furniture are the loudspeakers in question
- do you have floor carpets or anything soft
- what crossover have you used for the tweeter
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Old 19th September 2015, 04:15 PM   #26
eriksquires is offline eriksquires  United States
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Quote:
Originally Posted by Mercury3 View Post
Earlier today when I had the drivers out and taped the terminals with a nine volt battery (phase check) I notice they ring. They ring to nine volt battery. I'm like what the hell.
This is the best experiment yet! I am not sure about the battery, but please leave them out of the cabinet and play full range music through them (at a reasonable volume) without the XO. If you still hear the issue then you have eliminated all of the cabinet, and the crossover. Also, just to be sure, you aren't using esoteric cables with high capacitance or inductance are you?

If you take the drivers out of the cabinets, and a battery as well as music still causes the issue then you pretty much know where the problem is.

If it wasn't for the 9V battery tap ringing in the same way I would suspect your amplifier as a possible culprit as well.
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Old 19th September 2015, 08:13 PM   #27
Mercury3 is offline Mercury3  United States
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Okay thanks for all the additional suggestions. I want to be wrong about the drivers but I wish one of you could hear them right when in hand and just hitting the terminals with a battery. That ring sounds same frequency I'm hearing when female voice hits certain tone at high enough level. I've always done that batt. check just to make sure I'm phasing it right when I go to connect the wires and these are the first drivers I've ever heard do that.

However I am novice at speaker building. Many of you are experts so I'm hoping I'm wrong and think I could be wrong even though it looks like I'm not.

I need to play with and learn how to use the mic better which I will do. Then I'll try to get some additional graphs which have been suggested.

Incidentally when I very first encountered this I did think I had a tube ringing. Microphonics. I replaced all the tubes and bought some tube dampers. When that made no difference I did swap amps and checked with my transistor amp but it still made no difference. Not amp or tube related.

The crossovers are the Pass Labs XVR-1 and I can do a lot of adjustments with them. I thought if it might be ringing caused by the crossover I was hearing but low Q at 6db should almost eliminate the vast majority of crossover ringing. And the ringing is the same weather 6db or 24db slopes. It does sound like ringing/resonance rather than a peak.

I suppose I could be wrong but I sort of know what to listen for. I've been an audiophile for 35 years and used Altec and JBL horns/compression drivers back in the olden days so I've heard very bad peaks/irregular response curves and it doesn't sound like this. It's like a hiss/resonance being added to the sound but only when female vocals hits certain tone at high enough level. With the volume down it won't occur.

Tend to have to agree more people would be noticing something if it were the drivers though. I'll keep pursuing all of these suggestions and I appreciate everyone's efforts in attempting to help me with this.

By chance no one lives in the Denver area I suppose? It'd be nice if someone else could hear what my problem is.
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Old 19th September 2015, 08:57 PM   #28
Lojzek is offline Lojzek  Croatia
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Quote:
Originally Posted by Mercury3 View Post
Okay thanks for all the additional suggestions. I want to be wrong about the drivers but I wish one of you could hear them right when in hand and just hitting the terminals with a battery. That ring sounds same frequency I'm hearing when female voice hits certain tone at high enough level.
The 9V battery test is unnecessary high voltage just to test the phase.
That's 14 W of heat dissipation. 1,5V is enough.

You should hear only a short crackle sound the moment you touch the
terminals with battery and then the cone travels to some degree and
stops right there until you disconnect it.

Can you confirm that the voice coil is not rubbing while playing a very
low frequency sine wave signal (few Hz) of low voltage just to make the
cone move a couple of mm? The impedance graphs looks normal except
the high frequency part where the curve starts falling down (Zobel?).

edit: Try to simulate the TS parameters in your box at 14W of input
power and you should see how much of voice coil travel it would make
at certain frequencies. Could it be that you exceeded the mechanical Xmax
value?

Last edited by Lojzek; 19th September 2015 at 09:14 PM.
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Old 19th September 2015, 09:14 PM   #29
Mercury3 is offline Mercury3  United States
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Quote:
Originally Posted by Lojzek View Post
The 9V battery test is unnecessary high voltage just to test the phase.
That's 14 W of heat dissipation. 1,5V is enough.

You should hear only a short crackle sound the moment you touch the
terminals with battery and then the cone travels to some degree and
stops right there until you disconnect it.

Can you confirm that the voice coil is not rubbing while playing a very
low frequency sine wave signal (few Hz) of low voltage just to make the
cone move a couple of mm? The impedance graphs looks normal except
the high frequency part where the curve starts falling down (Zobel?).
Thanks I'll add this to my list of things to check. One thing has been in the back of my mind. I ordered these four drivers from Madisound. One of the boxes was missing part of the box material and looked like it was opened. I realize madisound has to test for their LEAP and so thought maybe it was that but if so Madisound would have replaced all the cardboard/plastic in the box which was missing.

I need to test all four drivers and see if I possibly only have two bad drivers which may have been returned by someone prior to me purchasing them. However they did not show any signs of being mounted.

Question can the Zobel pull down the upper frequency response on the tweeter?
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Old 19th September 2015, 09:26 PM   #30
Lojzek is offline Lojzek  Croatia
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An RC filter in parallel with the tweeter with the right values
can indeed pull down the FR similar to being low passed.
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