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Multi-Way Conventional loudspeakers with crossovers

Help with modification of QLN crossover
Help with modification of QLN crossover
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Old 2nd October 2008, 08:07 PM   #1
Cyberkul is offline Cyberkul  Norway
diyAudio Member
Join Date: Oct 2008
Default Help with modification of QLN crossover

Hi all!
I have a pair of QLN Qubic 929AV speakers, which I use in my home theater. I have a QLN FS-600 center, and four Qln 122 as rear speakers. I think the rear speakers have a rather open and bright sound, while the main speakers sounds a bit dark and muddy. So I suspected that something in the crossovers had failed, and inspeceted one of them. It seemed ok, all components measured fine. The main speakers are rather large, has two 6,5" bass drivers, a 6,5" midrange at the top in a sealed chamber, and a 1" silk dome. The quality of the crossover components seemd ok, and the enclosure is also ok, with internal bracing and made from 22mm board.

These speakers are about 10 years old, and not worth much, but if I could do something rather simple to improve the top/midrange I think it would be worth my while. Then i could spend some more on my dedicated hi-fi system..

The speakers are connected to a Pioneer receiver, and I notice that when i set the speakers to "small" they sound much better.

I made a drawing of the crossover, which I enclose here, in case someone knowledgeable would take a look at it. All drivers are Vifa.
I found the driver parameters online, but I`m not sure the parameters for the bass is correct. They are listed for the P17WJ-00-08 driver while mine is the P17WH-27-08, but it seems that several of the P17W drivers are almost identical.

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File Type: jpg crossover_qln929.jpg (77.2 KB, 84 views)
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Old 3rd October 2008, 01:57 PM   #2
sreten is offline sreten  United Kingdom
Join Date: Nov 2003
Location: Brighton UK

Basically there is not much you can do to change the overall balance
bass to midrange other than make it darker which is not what you want.

Looking at the layout they will sound bass heavy too close to walls.
(as the arrangement implies full 6dB baffle step compensation)

You could brighten the treble by reducing the tweeter series
resistor and the lower treble by increasing the 3.3R in parallel
with the midrange but I do not think that is what you want.

This sounds somewhat radical but you might be better swapping
about the drivers from your different speakers and tweaking the
crossovers, assuming the other c/o's are similar and simple.

Would the bass mid from the 122 be a drop in fit ?

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Old 3rd October 2008, 08:46 PM   #3
Cyberkul is offline Cyberkul  Norway
diyAudio Member
Join Date: Oct 2008
I noticed the treble series resistor, but it is only 0.8 Ohm (R82). I could short it out just to try. I think they sound ok for movies, maybe because of the receiver EQ.

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