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Multi-Way Conventional loudspeakers with crossovers

Introduction to designing crossovers without measurement
Introduction to designing crossovers without measurement
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Old 11th November 2017, 04:25 PM   #571
BobCat1950 is offline BobCat1950  United States
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Default Help!

I have a pair of Minimus 7 die cast aluminum speakers and i salvaged coils and capacitors from a pair of M7W. They are similar in measurements; C1=C2= 4.7 uF and L1=L2= 0.4mH.
The original crossover was filtering low frequencies to 1 inch dome tweeter (8 ohm) but the 4 inch woofer had no filter. Am i correct to assume that the woofer is actually duplicating some of the frequencies of the tweeter then.
I plan to take the salvaged parts to make a 2-way crossover putting the cap in parallel and the coil in series. Will this make a noticeable difference?
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File Type: jpg Minimus 7 7W Original X-over.jpg (30.0 KB, 324 views)
File Type: jpg Minimus 7 modified X-over.jpg (33.1 KB, 324 views)
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Old 12th November 2017, 11:31 PM   #572
phivates is offline phivates  United States
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Bobcat: The silence is the forum giving you time to read through this thread.
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Old 13th November 2017, 01:28 PM   #573
BobCat1950 is offline BobCat1950  United States
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Quote:
Originally Posted by phivates View Post
Bobcat: The silence is the forum giving you time to read through this thread.
thx for the info; I just saw this thread and thought i'd ask first, thx
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Old 15th November 2017, 07:07 PM   #574
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by BobCat1950 View Post
Am i correct to assume that the woofer is actually duplicating some of the frequencies of the tweeter then.
---
will this make a noticeable difference?
On the surface, the less duplication there is suggests the less difference it will make.. and there obviously isn't too much or they might(?) not have been made that way.. but when you listen to a woofer on its own without a filter they typically have an edge to the sound, gaps and peaks at the top end where the cone isn't operating as satisfactorily as it should, before dropping off.

Adding a filter can trim this, adding a controlled rolloff while limiting the bandwidth. Using the same coil/capacitor combination for both woofer and tweeter is a reasonable choice for a random assignment (without measurement). This assumes the two have an overlapping region where they can behave well and meet at some point after being trimmed. Some experimentation will still be in order.
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Old 15th November 2017, 07:37 PM   #575
BobCat1950 is offline BobCat1950  United States
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Quote:
Originally Posted by AllenB View Post
On the surface, the less duplication there is suggests the less difference it will make.. and there obviously isn't too much or they might(?) not have been made that way.. but when you listen to a woofer on its own without a filter they typically have an edge to the sound, gaps and peaks at the top end where the cone isn't operating as satisfactorily as it should, before dropping off.

Adding a filter can trim this, adding a controlled rolloff while limiting the bandwidth. Using the same coil/capacitor combination for both woofer and tweeter is a reasonable choice for a random assignment (without measurement). This assumes the two have an overlapping region where they can behave well and meet at some point after being trimmed. Some experimentation will still be in order.


Thank you so much, Allen B. You have actually helped a great deal. I am the original owner of the M7 from the late 80's and always felt/heard these speakers had more high's but when I modified the crossover I thought I could hear a big difference. Recently I set the M7 speakers to my Denon DRA-325R stereo as B speakers; put them about 5 feet above the A speakers(Mirage FRx 3's which I used to replace some older B & W V201's that seemed to have more than normal bass but that's another story) on top of the entertainment center facing up about 2 ft or less from the ceiling and I heard a lot more from the M7's which don't have as much bass as the A's but when played by themselves the sound was great on a Kitaro CD. I was modestly impressed! When both A & B play the room is full sound.
Thanks again for the Information, Allen. I appreciate it immensely.
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Old 23rd December 2017, 11:52 AM   #576
Eftegarie is offline Eftegarie  Netherlands
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Thanks Allen very well written introduction to custom cross-over designing!

Curious about your personal thoughts about high quality active systems without vs (high quality passive with crossover. I am hesitating betwee using active or passive for my custom 3-way project, using a high quality 3-way active crossover feeding my existing 3 Sony 80es amps, then from there directly going to various speaker drivers 4 / 8 ohms. That way completely avoiding the tidious/difficult proces of crossover designing. At the moment I am htinking about the following question:

Why would someone prefer a passive system over active system (given the fact and context when there are multiple high quality amplifiers and active crossovers already at hand)? So is there a acoustic BENEFIT in using passive vs active system? Thanks!
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Old 23rd December 2017, 08:46 PM   #577
AllenB is offline AllenB  Australia
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In the hands of a competent designer I feel there is no difference.

If you have the gear, active can give quick results, if you don't then passive can give quick results, but this is not what good crossover design is about either way. The tedium is the learning process, either way, but you'll find many have gone there before and can help.

Personally (and this is relatively insignificant and based on preference), I also design amplifiers. I concern myself with the active stages I put in my chain. I use two stereo amps for my main speakers in a combination of the above but I favour passive.. some at line level and some at speaker level.
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Old 4th January 2018, 03:28 PM   #578
Cirrus57 is offline Cirrus57  Canada
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I have just started reading this thread to help me design a crossover for my project . If I have 2 woofers in parallel do I treat them as 1 4ohm woofer ? I'm looking at flattening the impedance . Or do I use a resistor and capacitor on each one ? Connect them in parallel and add the inductor after ? I'm using scanspeak 22w/8857/t00 . I was thinking of cutting them off around 2k where they dip .
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Old 4th January 2018, 03:32 PM   #579
AndrewT is offline AndrewT  Scotland
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You can parallel the two 8ohms drivers and then treat the combination as if it had a 4ohms impedance, i.e. design the Low Pass Filter to feed a 4ohms load.
But that will need big heavy and expensive filtering components.

You may find it cheaper and easier to make the Power Amplifier and the Bass Drivers an active combination.
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regards Andrew T.
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Old 4th January 2018, 07:00 PM   #580
Cirrus57 is offline Cirrus57  Canada
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define expensive ? a couple nice size resistors to bring the ohms up to 8 ?https://www.walmart.ca/en/ip/100-Wat...RD4G6N8ZW49II0

Last edited by Cirrus57; 4th January 2018 at 07:09 PM.
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