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Multi-Way Conventional loudspeakers with crossovers

Help designing crossover
Help designing crossover
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Old 23rd October 2017, 11:12 AM   #1
scimmysfury is offline scimmysfury  Australia
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Default Help designing crossover

So I know that this topic has been covered extensively on this site already but I am just after a little help. I want to make a 2 way speaker with 2 woofers and 2 tweeters in a sealed box powered by a 100W mono amplifier.
Woofers - Dayton Audio 6" Reference RS150-8
Tweeter - Dayton Audio 1" ND25TA-4
Looking at the spec sheets I think I would like to cross them over at around 1800hz. Here is my problem, how do I design the crossover? Should I be looking at a butterworth or Linkwitz-Riley type? 2nd order or 1st order? Do I need to add resistors anywhere? I do realise that these answers can only be answered with measuring equipment or by tweaking the crossover later on but I do not have this luxury.

I know I can use the online calculators to get values of caps and inductors but reading on the forums there are other components which can change the response. Any help on recommendations would be greatly appreciated
Furthermore, the 8 ohm version of the woofer is cheaper than the 4 ohm version. The tweeter I want to use is a 4 ohm tweeter. Will I run into problems using this configuration? I think that I should be able to design the high and low pass of the crossover to whatever resistance so this should be fine? I was going to wire tweeters in series giving 8 ohms and the woofers in parallel giving 4 ohms.

I really want this project to be successful and sound good. This is my first proper DIY speaker build and I am very keen on the whole idea. I have been researching relentlessly but I feel as though I need specific help rather than general thus this question.

Last edited by scimmysfury; 23rd October 2017 at 11:42 AM.
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Old 23rd October 2017, 11:40 AM   #2
wintermute is offline wintermute  Australia
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Help designing crossover
This would be a good place to start reading Introduction to designing crossovers without measurement

I think this would be better in multiway so I will move it there.

Tony.
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Old 23rd October 2017, 12:44 PM   #3
giralfino is offline giralfino  Italy
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Tony gave you the right link, but IMHO the best methodology is described in post #20. If you follow what is described before you end up with an unnecessary complicated crossover.

However I would warn you that the drivers chosen are not well mated. The RS150 has an aluminium cone with low distortion in the pass band but also strong breakup and related induced distortion. As a result it should be crossed no higher than 2KHz. Unfortunately the ND25TA should be crossed not below 3KHz. So you have to change one or both drivers: if you want to cross at 3KHz (good point for a 5" driver), choose a polypropylene cone driver, else you need a more robust tweeter. For a 2KHz LR4 crossover point the cheapest tweeter that I can think of in 5 minutes is the Vifa DX25.
Another point of attention is the box type: for some bass you need a vented box for the RS150, the sealed box won't you give anything under 100Hz, dropping already at 200Hz.

Quote:
I want to make a 2 way speaker with 2 woofers and 2 tweeters in a sealed box powered by a 100W mono amplifier.
...
I was going to wire tweeters in series giving 8 ohms and the woofers in parallel giving 4 ohms.
I'm a bit puzzled at what you said. Whereas two woofers fed by the same signal is perfectly doable, two tweeters is series or parallel is definitely a no-no for interference reasons. If you have only one mono channel build only one speaker with a woofer+tweeter.

Ralf
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Old 23rd October 2017, 01:33 PM   #4
system7 is offline system7  United Kingdom
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Have a look at some existing RS 150-8 designs:
Lou's Speaker Site

It's usually not hard to adjust for a different tweeter. Compare sensitivities and the series resistor in the tweeter filter falls into place. Usually every ohm takes it down a dB. These things are select to taste anyway.
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Old 23rd October 2017, 09:58 PM   #5
wintermute is offline wintermute  Australia
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Help designing crossover
Quote:
Originally Posted by giralfino View Post
but IMHO the best methodology is described in post #20. If you follow what is described before you end up with an unnecessary complicated crossover.

Agree. Understanding Allen's method first, teaches you a lot before diving into Dave's approach. It's a good progression, followed of course by doing your own measurements!

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Old 23rd October 2017, 11:40 PM   #6
system7 is offline system7  United Kingdom
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Every combination is a new adventure IMO!

This Dayton RS 150-8 metal cone doesn't look too difficult.
Dayton Audio RS150-8 6" Reference Woofer

Nice low impedance, correctable with 7.5R and 12uF IMO. Cone breakup around 8kHz is not too bad either.

Louis Corragio did no less than 4 designs with this woofer and its 4 ohm cousin. Even with series and parallel wired MTM, which is close to where you want to go. Notice the breakup notch, which is not apparently essential.
Lou's Speaker Site

I really wouldn't try to reinvent the wheel when somebody has already done the heavy lifting.

You could probably do better on the tweeters here. Puny 4 ohm types aren't ideal for the near 2.5 kHz crossover the metal drivers dictate. But 5" woofers in a biggish reflex box can work well.

Quite an informative thread for the real-World builders here, and series MTM is really no more difficult than MT: C-Killa Build - Techtalk Speaker Building, Audio, Video Discussion Forum

Slightly noobish errors on coil alignment. Which should be at right angles to avoid interaction. But whatever.
Attached Images
File Type: jpg Dayton RS 150-8 FR.JPG (55.0 KB, 101 views)
File Type: jpg Dayton RS 150-8 Impedance.JPG (107.8 KB, 100 views)
File Type: jpg C-KIlla Speakerby Louis Corragio.JPG (36.4 KB, 99 views)
File Type: jpg C-Killa Speaker Louis Corragio Circuit.JPG (34.6 KB, 98 views)
File Type: jpg C-Killa Crossover Lou Corragio.jpg (178.2 KB, 98 views)
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Last edited by system7; 23rd October 2017 at 11:45 PM.
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Old 24th October 2017, 04:09 AM   #7
scimmysfury is offline scimmysfury  Australia
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Quote:
Originally Posted by giralfino View Post

I'm a bit puzzled at what you said. Whereas two woofers fed by the same signal is perfectly doable, two tweeters is series or parallel is definitely a no-no for interference reasons. If you have only one mono channel build only one speaker with a woofer+tweeter.

Ralf
There was no real reason as such for wanting the 2 tweeters and 2 woofers I just initially thought that it made sense. I would like to still have the 2 woofers though just because I have this image in my head of what I want it to look like.
If I still kept my mono amp, could I just run the woofers in parallel out of the crossover and a single tweeter out of the crossover too?
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Old 24th October 2017, 07:23 AM   #8
giralfino is offline giralfino  Italy
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In a single word, yes.

Ralf

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Old 24th October 2017, 07:47 AM   #9
giralfino is offline giralfino  Italy
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Quote:
This Dayton RS 150-8 metal cone doesn't look too difficult.
...
Cone breakup around 8kHz is not too bad either.
If you only look at the FR I can somewhat agree. However as is pretty usual with metal cone drivers the breakup propagates down in frequency with harmonic distortion, so the 3rd harmonics has a peak at 1/3 of the breakup frequency peak at around 3KHz. A notch at the main breakup frequency won't solve the problem, the only way is to cross lower than the harmonic peak, thus my suggestion for a 2KHz crossover point, relatively low for a 5" driver. Crossing at 2KHz solves both the breakup and the harmonic distortion peak.

Ralf

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Old 24th October 2017, 11:00 AM   #10
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by giralfino View Post
an unnecessary complicated crossover.
What would you change, and why?
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