Hi all, I'm good at putting wheels on things but crap at electronics.
This is mk I of an object I intend to build,
a subwoofer on wheels
with outdoor JBL control speakers (8ohm)
and an Alpine PDX 2.150 2 channel amp capable of
[2ohms @14.4V 1%THD]: 150W x 2
[4ohms @14.4V 1%THD]: 150W x 2
link here
The subwoofer is 2 ohm. Its a pioneer TS-WX205.
The speakers are 2x 8ohm. I intend to wire the speakers so that they are 4ohm.
I was informed on this forum that the amp can drive a 2 ohm load on one channel and a 4 ohm load on the second channel and not die. So thats nice.
So this is what I want to do.
I need to find a 2ohm low pass filter for the sub, but that is not an easy thing to find.
I read a bit, but I'm not naturally good at this stuff.
Is it true that I could use a 4ohm low pass filter at 160Hz, and because it has a 2ohm load, it will actually filter at 80Hz ?
This is mk I of an object I intend to build,
a subwoofer on wheels
with outdoor JBL control speakers (8ohm)
and an Alpine PDX 2.150 2 channel amp capable of
[2ohms @14.4V 1%THD]: 150W x 2
[4ohms @14.4V 1%THD]: 150W x 2
link here
The subwoofer is 2 ohm. Its a pioneer TS-WX205.
The speakers are 2x 8ohm. I intend to wire the speakers so that they are 4ohm.
I was informed on this forum that the amp can drive a 2 ohm load on one channel and a 4 ohm load on the second channel and not die. So thats nice.
So this is what I want to do.
I need to find a 2ohm low pass filter for the sub, but that is not an easy thing to find.
I read a bit, but I'm not naturally good at this stuff.
Is it true that I could use a 4ohm low pass filter at 160Hz, and because it has a 2ohm load, it will actually filter at 80Hz ?
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In general terms (I don't have the schematic for your 4ohm/160Hz LP filter):
To cross over at 80Hz, all C and L values should be doubled.
To then accommodate a 2ohm load, C values should be doubled and L values halved.
From the above, it would appear that your statement (Is it true that I could use a 4ohm low pass filter at 160Hz, and because it has a 2ohm load, it will actually filter at 80Hz?) is not true.
To cross over at 80Hz, all C and L values should be doubled.
To then accommodate a 2ohm load, C values should be doubled and L values halved.
From the above, it would appear that your statement (Is it true that I could use a 4ohm low pass filter at 160Hz, and because it has a 2ohm load, it will actually filter at 80Hz?) is not true.
Yes, but you could fairly easily build one yourself, which probably would be faster and cheaper.
Just post the info about all the parts of the system. The 80Hz crossovers could be either
before or after the amp. If they were after the amp, they would be much larger and more
expensive, since they would have to handle high currents and power.
You'll need an attenuator before one channel of the amplifier for either the sub or the series speakers,
depending on which is louder, to match their levels. It could be a pot to make it adjustable in level.
The Alpine amp literature mentions: HP/LP Crossover: 30 - 400 Hz, 12dB/oct
so this could be easier than you think.
Just post the info about all the parts of the system. The 80Hz crossovers could be either
before or after the amp. If they were after the amp, they would be much larger and more
expensive, since they would have to handle high currents and power.
You'll need an attenuator before one channel of the amplifier for either the sub or the series speakers,
depending on which is louder, to match their levels. It could be a pot to make it adjustable in level.
The Alpine amp literature mentions: HP/LP Crossover: 30 - 400 Hz, 12dB/oct
so this could be easier than you think.
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It appears that the easiest (and perhaps cheapest) way is to buy another of the amps (or similar),
and use one for the sub, and the other for the main speakers, setting the crossovers differently.
There is a wide range level control as well to match the outputs. No building of special circuits at all,
you just need the stereo to mono converter, and another similar amplifier with a crossover.
https://www.alpine-electronics.co.e...r_audio_manuals/PDX-2.150/OM_PDX-2.150_EN.pdf
Alpine PDX-2.150
Input Impedance .... 10k ohms
Frequency Response (+0, -1dB).........20 - 20 kHz
Crossover (Variable, L.P. /H.P. /OFF) 1/2 ch ....30 - 400 Hz (-12 dB /oct)
Input Sensitivity (V / at 10k ohms).......... 0.2V - 4.0V
and use one for the sub, and the other for the main speakers, setting the crossovers differently.
There is a wide range level control as well to match the outputs. No building of special circuits at all,
you just need the stereo to mono converter, and another similar amplifier with a crossover.
https://www.alpine-electronics.co.e...r_audio_manuals/PDX-2.150/OM_PDX-2.150_EN.pdf
Alpine PDX-2.150
Input Impedance .... 10k ohms
Frequency Response (+0, -1dB).........20 - 20 kHz
Crossover (Variable, L.P. /H.P. /OFF) 1/2 ch ....30 - 400 Hz (-12 dB /oct)
Input Sensitivity (V / at 10k ohms).......... 0.2V - 4.0V
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If you would prefer a passive solution, note that a passive crossover for 2ohm/80Hz would involve large values of C and L.
A higher crossover frequency would be more practical.
Play with this calculator Low-pass filter 12 dB per octave
e.g. 2ohm/180Hz can be achieved with 440uF (two 220uF NP electrolytic capacitors in parallel) and one 3.0mH inductor (preferably wound down to 2.8mH).
The components, as rayma says, would require high power handling capacity.
A higher crossover frequency would be more practical.
Play with this calculator Low-pass filter 12 dB per octave
e.g. 2ohm/180Hz can be achieved with 440uF (two 220uF NP electrolytic capacitors in parallel) and one 3.0mH inductor (preferably wound down to 2.8mH).
The components, as rayma says, would require high power handling capacity.
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Support for TS-WX205 | Pioneer
The Pioneer sub manual says it is 4R impedance, do you want to use two of them in parallel?
You only show one in the diagram. If two, just use one sub per amplifier channel.
The Pioneer sub manual says it is 4R impedance, do you want to use two of them in parallel?
You only show one in the diagram. If two, just use one sub per amplifier channel.
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Guys thanks, thanks so much I really apprciate it.
I got cash! I work my *** off all day.. so I do have cash.
I want the system to be efficient and to run on a 12v battery. The literature says the PDX amp is very efficient and runs cool, so I like that.
You can see below I have a JBL GTR-7535 5 channel bluetooth amplifier strapped to the sub.
The bluetooth feature is awesome but the amp gets very warm during operation, I dont like that. Too wasteful to use battery.
The JBL is a 5 channel amp and I played around with some speakers and the sub crossover settings on the amp, and it came out at 80 hertz that sounded good to me.
Thats why I chose 80Hz
So I figure using the same sub... 80Hz will proabably work.
The reason I like this configuration, (mono signal > alpine 2 channel amp > 1 channel high range, other channel subwoofer) is to try and make the object power efficient, so adding another amp wont work.
__________________________________________________
I hear what you are saying about the crossover needing to be beefy to cope with the power, and yeah, thats fine, how do I do it?
I came across this coil on ebay.... MTX AUDIO 200 WATT OPTIMIZED COIL OC42 CROSSOVER POINTS 80Hz @ 2OHM PLEASE READ | eBay
Regarding a volume level attenuator, yes I thought of that also this evening, I think a 4ohm attenuator is going to be easier to find.
I got cash! I work my *** off all day.. so I do have cash.
I want the system to be efficient and to run on a 12v battery. The literature says the PDX amp is very efficient and runs cool, so I like that.
You can see below I have a JBL GTR-7535 5 channel bluetooth amplifier strapped to the sub.
The bluetooth feature is awesome but the amp gets very warm during operation, I dont like that. Too wasteful to use battery.
The JBL is a 5 channel amp and I played around with some speakers and the sub crossover settings on the amp, and it came out at 80 hertz that sounded good to me.
Thats why I chose 80Hz
So I figure using the same sub... 80Hz will proabably work.
The reason I like this configuration, (mono signal > alpine 2 channel amp > 1 channel high range, other channel subwoofer) is to try and make the object power efficient, so adding another amp wont work.
__________________________________________________
I hear what you are saying about the crossover needing to be beefy to cope with the power, and yeah, thats fine, how do I do it?
I came across this coil on ebay.... MTX AUDIO 200 WATT OPTIMIZED COIL OC42 CROSSOVER POINTS 80Hz @ 2OHM PLEASE READ | eBay
Regarding a volume level attenuator, yes I thought of that also this evening, I think a 4ohm attenuator is going to be easier to find.
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Why insist on a passive crossover? High power wasting, expensive components, amp channel unloaded on higher frequencies (noise, interference, connect/disconnect pops, thumps, etc).
Especially since efficiency is high on your list of requirements, buy or build a simple one or two op-amp LPF, OR USE THE ONE BUILT INTO THE ALPINE!
And please don't waste your time and money on a 4 ohm power attenuator -- a simple, perfectly ordinary 10K pot to control the input to the amp channel is better.
Cheers
Especially since efficiency is high on your list of requirements, buy or build a simple one or two op-amp LPF, OR USE THE ONE BUILT INTO THE ALPINE!
And please don't waste your time and money on a 4 ohm power attenuator -- a simple, perfectly ordinary 10K pot to control the input to the amp channel is better.
Cheers
The calculator linked to above by Galu, says the following (I could set the slider to 80Hz)
So approximately a 6.5mH coil should work, how about this one?
So approximately a 6.5mH coil should work, how about this one?
You can do it the very same way, one capacitor and one coil, right there in the box with the volume control if you want! Usually folks want to eliminate coils whenever possible, but before there were op-amps, all decent crossovers had one or more. You may need to sniff around for a handy calculator if the one Galu linked won't allow 10k for a load impedance.
I still don't understand why you don't want to use the LPF built into the Alpine .. It could solve all your issues (that you've mentioned so far), plus if you use the corresponding HPF side for the other channel, it will allow higher SPL on less power! And your full-range two-ways won't suffer the insult of below 80Hz stuff, which they can't deliver anyway.
I'll download that manual linked earlier (thanks rayma) and try to help; it may take me a day or two.
Regards
I still don't understand why you don't want to use the LPF built into the Alpine .. It could solve all your issues (that you've mentioned so far), plus if you use the corresponding HPF side for the other channel, it will allow higher SPL on less power! And your full-range two-ways won't suffer the insult of below 80Hz stuff, which they can't deliver anyway.
I'll download that manual linked earlier (thanks rayma) and try to help; it may take me a day or two.
Regards
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OK, I was wrong. It appears that the crossover doesn't allow a different setting for each channel. If it can't be persuaded to affect only one channel, it won't do what you want.
I'm going to dig around and see if I can cobble up a passive solution, for the amp input, that doesn't require extreme/outlandish component values.
I'm going to dig around and see if I can cobble up a passive solution, for the amp input, that doesn't require extreme/outlandish component values.
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Ooops, wrong again. (Guess it has been longer than I realized since coils participated in an audio filter design of mine -- aging memory syndrome ..)
If you can find an audio-quality 1,47 Hy inductor (I couldn't, but must confess to not trying too hard), you could still build the straight-forward LC filter. (see below) But now this makes me wonder, 'What are your plans for the JBL amp? It has several crossover options, doesn't it?'
Cheers
(Guess it has been longer than I realized since coils participated in an audio filter design of mine -- aging memory syndrome ..)If you can find an audio-quality 1,47 Hy inductor (I couldn't, but must confess to not trying too hard), you could still build the straight-forward LC filter. (see below) But now this makes me wonder, 'What are your plans for the JBL amp? It has several crossover options, doesn't it?'
Cheers
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Rick I love your idea of placing the crossover before the amp, thats genious
So will that crossover work you think? Should I start buying components, and where might I buy the components online, I'm in Ireland. I had a look at ebay, seems like it might be a good place to get them.
So will that crossover work you think? Should I start buying components, and where might I buy the components online, I'm in Ireland. I had a look at ebay, seems like it might be a good place to get them.
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