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Multi-Way Conventional loudspeakers with crossovers

Bass reflex not so good
Bass reflex not so good
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Old 28th June 2020, 05:48 PM   #11
GM is offline GM  United States
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Thanks! That's what was 'bugging' me earlier, but too sleep deprived to figure it out plus the peaks are significantly lower than they historically are when dual 8 ohm AlNiCo Altec are wired in parallel.

Then again, Bill has had to replace a lot of worn out Altec/EV tooling, so may be moot.

GM
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Old 28th June 2020, 06:04 PM   #12
EarlK is offline EarlK  Canada
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Originally Posted by giralfino View Post
OK, I'm the only one that sees a problem in the impedance graph? Too many irregularities? It is just a bad measure/methodology or it is a valid impedance? If the latter the speaker is full of vibrations or other problems. Can I see an impedance graph of a standalone driver?

Ralf
It appears that Francesco measured only 1 ( of 2 ) woofers present in the box ( with the 2nd woofer flapping in the breeze, so-to-speak, >> acting as a mechanical microphone ).

That's a sure way to get some unreliable/// hard-to-dissect results.

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Old 28th June 2020, 06:33 PM   #13
ScottG is offline ScottG  United States
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Ah, second woofer acting as another "vent"/passive-radiator. That explains the < 20 Hz irregularity in impedance.

(..the un-connected driver acting as a passive-radiator could result in a "dirty" sound: with too much excursion and it's surround causing audible problems.)

Still, the driver's resonance in-box has a very low magnitude for its Qe - almost always the result of to much "fill". (..the "peak" of the driver's resonance should be closer to 40 ohms at a minimum.)
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Old 29th June 2020, 12:47 PM   #14
francesco81rs is offline francesco81rs  Italy
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Default Wrong measure

Oops, sorry!
What a stupid measure I had done.
Tonight I will do it again with the parallel connection of the two woofers, and using the linear scale.
However, the "dirty / confused" sound sensation is there; with the two woofers connected (certainly) in parallel.
As soon as possible I will also give you some photos of how it is done internally, so that you can better see the "filling".
The internal volume that I had calculated was based on the alignment tables and I had chosen the QB3.
They are around 350L and it seems to me to be a volume very similar to the Altec Valencia project, obviously multiplied by two.
Do you think the cabinet can be used with this internal volume?
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Old 29th June 2020, 09:02 PM   #15
francesco81rs is offline francesco81rs  Italy
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Post Impedence swap

The swap impedence in linear scale and also in logarithmic scale.
Woofer connected in parallel.
Attached Images
File Type: png impedence-parallel.png (60.4 KB, 203 views)
File Type: png impedence-parallel-log.png (48.1 KB, 200 views)
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Old 29th June 2020, 09:13 PM   #16
HumbleDeer is offline HumbleDeer  Belgium
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The impedance curve looks more healthy now. I think the bumpiness might just be the lack of smoothing, though I have no idea what functions the DATS software has on that field.

It looks like first gen DATS software doesn't it? "DATS" in the title bar and not DATS v2 or v3.
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Old 29th June 2020, 10:09 PM   #17
ScottG is offline ScottG  United States
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-take out ALL of the fiber.

Then listen again and take another Impedance measurement.
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Old 29th June 2020, 10:16 PM   #18
ScottG is offline ScottG  United States
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Quote:
Originally Posted by francesco81rs View Post
They are around 350L and it seems to me to be a volume very similar to the Altec Valencia project, obviously multiplied by two.
Do you think the cabinet can be used with this internal volume?

..is that 700 liters total per loudspeaker?

350 liters per driver is not so great as far as bass reflex is concerned (for this driver), unless you are "tailoring" the freq. response for a specific result (..boosted bass and truncated lower freq. (sub-bass) response relative to the average.) That amount of volume isn't bad for a sealed design though.
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Old 29th June 2020, 11:53 PM   #19
N101N is offline N101N
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Others can correct me if I'm wrong, but I believe running the bass driver all the way up to 500 Hz might be causing some intermodulation distortion into the midrange, which could cause the sound you're talking about.
500 Hz is far too high, max 100 Hz would be better.
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Old 30th June 2020, 01:34 AM   #20
GM is offline GM  United States
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Originally Posted by ILikeFoodz View Post
Others can correct me if I'm wrong, but I believe running the bass driver all the way up to 500 Hz might be causing some intermodulation distortion into the midrange, which could cause the sound you're talking about. Is the confusion sound much better if you play the speakers at a low volume? Lower volumes will have lower IMD.
While true for probably 97% of 15" woofers available nowadays, there's a small number of manufacturers that build modern versions/variants of the pioneer's ultra wide range drivers; with GPA building new, improved versions to Altec specs, which BTW the 416 started life in '48 as the 803 designed for an 800 Hz XO.

Time marched on and due to many material, manufacturing advances combined with increasing power the 803/416A was born with up to a 1200 Hz XO at high SQ, so 500 Hz is considered a waste of an excellent 15" ultra wide range woofer by many. Indeed, me and some others have run the original 416s, 515s wide open with just a tweeter horn capped off at ~5 kHz where they finally take a nosedive, though with the understanding that they have limited polar response, but more than you might think due to their curvilinear cone, careful doping Vs modern 'flat' cone drivers.

GM
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