Introduction to designing crossovers without measurement - Page 24 - diyAudio
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Old 24th November 2013, 08:36 AM   #231
AllenB is offline AllenB  Australia
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Not necessarily. If you are familiar with the circumstances and the equipment.

If there is a choice, I think it is better to use the crossover to blend the speakers and an equaliser to change the tone to suit a preference. Say you have a mid driver with a resonance below its crossover frequency. Equalising the total sound at this frequency will bring both the mid and woofer down in the process. In this way a problem will still have the same relative contribution from the driver creating the problem.

A crossover will often have to cut problem regions outside a drivers band, and a crossover is a good place to do this. Once you have it blending the drivers you can do simple EQ such as getting the levels right.

Crossover changes can cause previously hidden problems to re-surface. Sometimes more than one change to the sound will come from a single crossover change, and it can be difficult to tell what is going on when trying to avoid making things worse. When a crossover is done as well as it can be it is helpful to leave it there.

When EQing you'll probably also notice that you can't get everything right. Sometimes a resonance will be sharper (narrow band) than the EQ bands. Many issues are beyond EQing due to their nature but these will also be beyond adjusting in a crossover. Such issues need to be fixed where they begin, such as the speakers themselves.
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Old 25th November 2013, 06:25 PM   #232
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Thanks AllenB.

I will try a "scientific" approach.

The woofer/tweeter are stocked mounted in the car, I couldn't find so far any data except the one that is impressed in the part, oem part number and 4Ohm.

Time to do some experimental work.
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Old 7th January 2014, 08:14 PM   #233
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Quote:
Originally Posted by AllenB View Post
You will firstly need to choose a crossover frequency that gets the best out of the drivers.

Woofers - choosing where to cross
If you look at the woofer's frequency response plot shown below, you will see that the woofer has a peak in its response at 4kHz (4,000 Hertz) just before it rolls off above 7kHz. In other words, it will play too loud at these frequencies. This peak is not uncommon for a woofer but it will not always be obvious when looking at some plots.



A rule of thumb is to leave at least an octave (or two) between the crossover point and the cone breakup. An 'octave' means a doubling or a halving in frequency, so in the case of the woofer shown below, our crossover should probably be at or below 2kHz.
An octave or two is quite possibly not enough. These peaks that are common in the harder cone drivers, and right where in frequency the human ear is most sensitive, are often resonant, which means smeared in time (ringing), which makes them even more audible. I would say stay at least one octave away from the peaks if you are using a 4th order active crossover. You want those peaks to be down 12dB if you're talking "Hi-Fi". If you look at the results with a calibrated mic, you'll notice that these peaks are not easily attenuated by a simple passive crossover. For anyone who has limited experience building speakers, I highly recommend using polypropylene cone drivers for bass and mid. Always check the published frequency response graph, which is always averaged, and use drivers that don't have any significant peaks in the upper end.
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Old 6th February 2014, 07:31 PM   #234
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Very good read, Thank you for all the information
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Old 7th February 2014, 06:53 PM   #235
Filius is offline Filius  United States
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Yes, another thank you. This was just what I needed and right at my level.

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Old 23rd February 2014, 09:01 PM   #236
Dlav is offline Dlav  United States
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Mr AllenB, I would like to thank you for the work you've done on this tutorial, I'm a electrician and I know ohms law and that is my limit of electrical theory, please pardon my ignorance. I've been researching for about 6 months now, I became a member of DIYaudio and wow I found your tutorial thank goodness. I'm using the tutorial to build a trial speaker set ( 8" woofer & 1" dome tweeter) to get some experience before I build a permanent set for my home. I have a question on the flattening of the impedance on the woofer, I did the 1st step to find the resistor value it's 4.7 ohm, then went on to find the capacitor value, my woofers LE is 0.5mH divided by resistor squared is 22.09=.0227272, so my question is the value for the cap is it a 2.27mf or 22.72mf, I'm not sure where to place the decimal. Keep in mind this is just a trial set, the woofer is a goldwood 408D it has no frequency plot to find out about where cone break up starts, it gives a FS of 51.2hz & 44-5000hz, so I'm guessing I'll have to randomly choose a xover point. One other question i noticed you made no mention of the wattage of the resistors or the voltage rating of caps to be used, maybe the values don't matter, or just say keep all caps in a xover the same voltage ratings say 100v. Thanks so much Mr AllenB for all the work you've put into the forum, its going to be my rock in my adventure.
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Old 2nd March 2014, 07:22 PM   #237
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22,6uF
Resistors 10W to be on the safe side
100V rated caps are OK but use more V not too much difference in price

Last edited by merlin el mago; 2nd March 2014 at 07:28 PM.
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Old 17th April 2014, 09:43 PM   #238
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Default LaScala Bi amp ?

Hello again . I have been an audiophile since the mid 1960's and thought I knew enough but I have a Question: I love my LaScala in the midrange and treble with my mac pre and 60wpc dynaco vta st 120 tube amp but the dynamics are far better in the bass with a high currant ss amp . Soo the question is with a fairly new [2 years ] Type AA x-over can I use any of the existing X-over parts to make a x-over for splitting the freq. to use the tubes for the mid and high horns and bi-amp with a solid state amp for the woofer ? I am Not flush with money at this time but I do have access to a 100 wpc amp. I am sure active x-over would be best but I look at berringer etc and am not clear if that[ Dont know a model #] but I am Also not clear if I could both make it a very steep x-over and also time align the drivers . I think it may make me happy for a bit Thank all of you for your answers you are an amazing group.I am also sound deadening my room [its 12'x12' with an 9' ceiling and I have big standing waves and way too much at probably 150-200 htz and was told to dampin at least one wall and foor but I am willing to dampin it alot more. when I first got the LaScala My room was about 32'x24' with a very high ceiling and they sounded great but now with a small room Not so great HUGE bump and loss off clean bass. Thank you again for dealing with a newbe.Scott in Eugene ... Raining again ... Good day for tunes !
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Old 19th April 2014, 11:04 PM   #239
krafty is offline krafty  Brazil
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Ok, here to say that the tutorial is great...

But I've got one question... this is the X/O without measurement.

How do you do a X/O based on measurements and what the least right tools does it involve?
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Old 24th April 2014, 04:27 AM   #240
AllenB is offline AllenB  Australia
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@ScottLowe. I am not familiar with LaScala or its type AA crossover, but if it is a conventional parallel crossover couldn't the driver sections be separated as to be powered individually? This would not require any additional crossover, active or otherwise apart from adjusting the relative gains. Some further work could later be done to optimise the usage of the amps such as limiting LF swing in the upper amp etc.

Last edited by AllenB; 24th April 2014 at 04:31 AM.
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