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First 12v sound system plans

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Category: General
Forum Name: 12v Powered Systems
Forum Description: From Mini-rigs to ICE, all your low voltage audio needs here...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=104817
Printed Date: 28 March 2024 at 11:07pm
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Topic: First 12v sound system plans
Posted By: Jack1991
Subject: First 12v sound system plans
Date Posted: 08 February 2020 at 8:39pm
What im planning so far:

Tham12 loaded with;
1x 12" the box speaker 12-280/8W
Power capacity: 280 W RMS
Impedance: 8 Ohm

Mid/Top:

Mid =
1x 10" the box speaker 10-250/8-A
Power rating: 250 W RMS
Impedance: 8 Ohm
SPL: 94 dB (1W/m)


Top =
1x Eminence ASD1001
RMS: 50W
Usable Frequency Range 2.5 kHz - 20 kHz
Recommended Crossover 2.5 kHz / 18 dB
SPL: 104 dB

Passive Crossover =
Eminence PXB2-2K5CX

Amplifier: 
1x Pioneer GM-D8704 Class-D 1200w 4-Channel bridgeable
Bridged = 2x 300w rms @ 4ohm


I was thinking of bridging 2x channels for the Sub and bridging 2x channels for the Mid/Top too.



Look forward to any advice, thanks! šŸ˜€



Replies:
Posted By: Xoc1
Date Posted: 08 February 2020 at 11:16pm
The Box Speaker 12 looks good in a Tham 12 sim. If the parameters I found can be trusted

Midrange efficiency will be important. Maybe consider a 12" mid for better efficiency.

If you are thinking of sticking with the Eminence APT then the crossover frequency is 3.5K.
The Eminence 3.5K crossover is a reasonable match.


Posted By: Jack1991
Date Posted: 09 February 2020 at 3:36pm
Yes ive heard on another forum a good few people said it works great in there tham12. 

Okay cool ill check out the Eminence crossover now thanks! I do like the look of the Eminence top so would like to use it yeh.

I was leaning more towards the fane 8" more than the 10" but you think i should go 12" mid instead? 

With passive crossovers are they litterally "plug and play" as in solder Mid and Top  to it and then connect the crossover to the amp. Or do they need tuning and stuff to get them right? Im new to all this so trying to get the correct info before i begin.


Posted By: APW
Date Posted: 09 February 2020 at 5:39pm

The Fane Sov 8-225 is fairly efficient (@ 97db/w) and in the right box can meet the Tham, I have a friend who has a couple of fanes in the 18-sound 8ā€ suggested designs ā€œapplication noteā€ enclosures that he uses with a couple of Thams, the whole thing sounds quite sweet. 

The Eminence crossover is OK, however you are going to need an 7-8db l-pad between the crossover and APT150s due to the difference in sensitivities.

FYI: http://www.eighteensound.com/en/resources/suggested-designs/" rel="nofollow - http://www.eighteensound.com/en/resources/suggested-designs/




Posted By: Jack1991
Date Posted: 09 February 2020 at 6:23pm
Ah right cool thats good to hear! Ill check that out now as im still stuck with enclosure choice. 

Oh okay i didnt know you should match the sensitivitys of each speaker too. Should i be matching the sensitivity of the Sub, Mid and Top really? Or just the mid top as they are linked together via crossover and in the same box.

Also why do the sensitivities need to be matched? Is it so they all sound equal i assume?

Thankyou! šŸ™‚šŸ‘šŸ¼


Posted By: Mikkel
Date Posted: 09 February 2020 at 10:04pm
Hey. i dont know about what youve seen online but the sim im getting for the 12-280/8-w in tham12 doesnt look so good to me. theres a 3dB drop from 60hz hump down to ~100hz. Dont have computer connected to internet so cant post up sim, will do later in week when get home if your interested.


Posted By: concept-10
Date Posted: 09 February 2020 at 10:15pm
Originally posted by Mikkel Mikkel wrote:

Hey. i dont know about what youve seen online but the sim im getting for the 12-280/8-w in tham12 doesnt look so good to me. theres a 3dB drop from 60hz hump down to ~100hz. Dont have computer connected to internet so cant post up sim, will do later in week when get home if your interested.

Nothing is very flat from 60-100 in the tham 12 when simmed, in the real world that driver is ok with some slight eq if need be, for a 12volt system it will be fine.


Posted By: Mikkel
Date Posted: 09 February 2020 at 10:29pm
Originally posted by concept-10 concept-10 wrote:

Originally posted by Mikkel Mikkel wrote:

Hey. i dont know about what youve seen online but the sim im getting for the 12-280/8-w in tham12 doesnt look so good to me. theres a 3dB drop from 60hz hump down to ~100hz. Dont have computer connected to internet so cant post up sim, will do later in week when get home if your interested.

Nothing is very flat from 60-100 in the tham 12 when simmed, in the real world that driver is ok with some slight eq if need be, for a 12volt system it will be fine.


Fair enough, reason is ive been designing my own tapped pipe for that driver for my own 12v idea and the tham was an obvious candidate but was put off by poor performance. Good to know anyway.


Posted By: concept-10
Date Posted: 09 February 2020 at 11:00pm
It works well in the MTH-30 and some BFM designs as well, for the money you can't go wrong, good luck with your project Smile


Posted By: Mikkel
Date Posted: 10 February 2020 at 7:20am
Nice one, cheers.


Posted By: Jack1991
Date Posted: 10 February 2020 at 10:47am
Any advice on the reducing tweeters sensitivity db? I dont really get the L-pad idea.

Is this a crucial step or something only a "audiophile" would pick up on.

Tweeter: 107db
Mid: 95db


Posted By: APW
Date Posted: 10 February 2020 at 11:11am

I wouldnā€™t worry about having higher sensitivity on the bass; you are bi-amping so you can turn the bass down slightly on the amp if itā€™s too muchā€¦ however the system will sound ā€œfullerā€ having a 3 to 6db extra on the bass.

If you are using DSP you CAN EQ the HF out and/or using separate amps to drive the comp/tweeter, however as you are going to use a passive crossover itā€™s better to use an l-padā€¦ The l-pad is simply two large resistors that reduce the tweeters output but maintain the correct impedance that the crossover sees, without it you will have way to much HF from the tweeter, the result will be a speaker system that you can cut peopleā€™s heads off with!!

L-Pad calculator: http://www.mh-audio.nl/Calculators/att.html" rel="nofollow - http://www.mh-audio.nl/Calculators/att.html

Depending on your MF driver you may also need a Zobel network; however I seem to remember the 8-225 doesnā€™t need one to sound OK. A zobel is a RC network that is placed across the woofer, this corrects for the rising impedance with frequency curve that a woofer has due to the VC inductance, in some instances this messes with the crossover point as passive crossovers are designed to work in to a specific impedance.



Posted By: studio45
Date Posted: 10 February 2020 at 11:11am
Yes you will need the L-Pad. It is just 2 resistors, so don't be scared ;)

107-95 = 12dB. So you need to lose 12dB of signal at the tweeter, in order for it to be the same loudness as the woofer, rather than overpowering it completely (this will sound far too harsh and terrible)

At 8 ohms, a -12dB L-Pad can be made of: one 6 ohm resistor in series with the driver, followed by one 2.6 ohm resistor in parallel with the driver.

Here is a calculator:  https://www.diyaudioandvideo.com/Calculator/DriverAttenuationLPadCircuit/" rel="nofollow - https://www.diyaudioandvideo.com/Calculator/DriverAttenuationLPadCircuit/

Use 20 or 50 watt wirewound resistors. They will probably not need heatsinks but it is good practice.


-------------
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: Jack1991
Date Posted: 10 February 2020 at 11:52am
Originally posted by studio45 studio45 wrote:

Yes you will need the L-Pad. It is just 2 resistors, so don't be scared ;)

107-95 = 12dB. So you need to lose 12dB of signal at the tweeter, in order for it to be the same loudness as the woofer, rather than overpowering it completely (this will sound far too harsh and terrible)

At 8 ohms, a -12dB L-Pad can be made of: one 6 ohm resistor in series with the driver, followed by one 2.6 ohm resistor in parallel with the driver.

Here is a calculator:  https://www.diyaudioand.com/Calculator/DriverAttenuationLPadCircuit/ - https://www.diyaudioandvideo.com/Calculator/DriverAttenuationLPadCircuit/

Use 20 or 50 watt wirewound resistors. They will probably not need heatsinks but it is good practice.

Cool perfect thanks! Ive never done anything like this before so i am out my depth, but really want to give it a go. 

So the resistors litterally just solder into the speaker cable? I saw the diagramf where they go but are they just soldered in place to the speaker cable?

Also how do you heatsink them?!


Posted By: studio45
Date Posted: 10 February 2020 at 1:52pm
If you look up some pictures of 50 watt metal clad resistors, you will see what I mean. You will need to mount them on something, they can't just be free-living in your box! But yes they solder inline with the speaker cables, or you can use a screw terminal block to make the connections. This would be good for testing, as you can get a few different values of resistor and swap them in and out to get exactly the right level of attenuation. 12dB might be just a bit too much, or too little. Your ears will tell you.
A heat sink is just a chunky piece of metal with fins mouled into it. Usually aluminium. It helps disperse heat generated in the resistor. You bolt or rivet the resistors to it, by their mounting holes. Or, if you end up with the ceramic type without mounting holes, you can use some heat-transfer adhesive - same stuff as used to glue heatsinks onto computer CPU's. 
But in fairness, I don't think you will be putting so much power through your tweeter, that the resistors will ever get more than warm. So probably don't worry about heatsinks for this project, unless during testing, you find you have a problem with heat. Just mount the resistors to a piece of wood using wire ties.


-------------
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: Jack1991
Date Posted: 10 February 2020 at 2:07pm
Originally posted by studio45 studio45 wrote:

If you look up some pictures of 50 watt metal clad resistors, you will see what I mean. You will need to mount them on something, they can't just be free-living in your box! But yes they solder inline with the speaker cables, or you can use a screw terminal block to make the connections. This would be good for testing, as you can get a few different values of resistor and swap them in and out to get exactly the right level of attenuation. 12dB might be just a bit too much, or too little. Your ears will tell you.
A heat sink is just a chunky piece of metal with fins mouled into it. Usually aluminium. It helps disperse heat generated in the resistor. You bolt or rivet the resistors to it, by their mounting holes. Or, if you end up with the ceramic type without mounting holes, you can use some heat-transfer adhesive - same stuff as used to glue heatsinks onto computer CPU's. 
But in fairness, I don't think you will be putting so much power through your tweeter, that the resistors will ever get more than warm. So probably don't worry about heatsinks for this project, unless during testing, you find you have a problem with heat. Just mount the resistors to a piece of wood using wire ties.

Perfect thank you! Im glad you said about them not being "free living" in the box as thats what i wanted to know.

So i can just solder the resistors in the correct positions, cable tie to a piece of wood and then screw the wood to the inside of the speaker box.

So once ive got the mid speaker and tweeter connected to the crossover and the resistors connected to the tweeter that will then be it for the 2 way speaker. No more surprises lol? 

Do you have any reccomended sites for buying the resistors? 


Posted By: concept-10
Date Posted: 10 February 2020 at 2:15pm
Jack, we have our own 12" tapped horns, similar to the Tham 12, the Beyma 12lx60 v2s have been taken out and Thomann 12Ws are in as we speak, you will love it Smile


Posted By: Jack1991
Date Posted: 10 February 2020 at 2:24pm
Originally posted by concept-10 concept-10 wrote:

Jack, we have our own 12" tapped horns, similar to the Tham 12, the Beyma 12lx60 v2s have been taken out and Thomann 12Ws are in as we speak, you will love it Smile

Oh thats great! Im glad its working well. I cant wait to build it but want to make sure i know 100% what im doing before i even begin any of it. As i feel  like im learning another language trying to learn the ins and outs of speaker building haha
What amp are you using to power it are you running 12v too?


Posted By: concept-10
Date Posted: 10 February 2020 at 3:05pm
No, Crest buddy, another thought, you will need to high pass the Tham, there is a 12v car amp with high and low pass filters, class d and quite cheap, made by BASSFACE, I will have a look later for you. I will also have a play with high and low pass filters and give you some settings.


Posted By: Jack1991
Date Posted: 10 February 2020 at 7:19pm
Oh okay cool. 

Ah yeh the pioneer amp i have been looking at is class d with low/pass filters https://www.google.com/search?q=Pioneer+GM-DX874&client=ms-android-ee-uk-revc&prmd=svin&sxsrf=ACYBGNSY0DUQYHxVtfKahvNuanb7P5T5qA:1581362231740&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjb3dWw2cfnAhWhwOYKHToeCFsQ_AUoA3oECA8QAw&biw=360&bih=660&dpr=3#imgrc=utAleN-8q6LqtM

Dont you mean low pass filter the sub not high pass?


Posted By: concept-10
Date Posted: 10 February 2020 at 7:46pm
No, high pass around 40hz and low pass about 100-120hz.



Posted By: concept-10
Date Posted: 10 February 2020 at 7:52pm
This would do for your bass, bridged, with a subsonic high pass filter and a low pass to your mid tops, not a bad price.
https://www.bassfacecaraudio.co.uk/product/db21-21-channel-bridgeable-stereo-12v-power-amplifier-200w-verified-rms-power-output/db21" rel="nofollow - https://www.bassfacecaraudio.co.uk/product/db21-21-channel-bridgeable-stereo-12v-power-amplifier-200w-verified-rms-power-output/db21


Posted By: Jack1991
Date Posted: 11 February 2020 at 8:57pm
Originally posted by concept-10 concept-10 wrote:

No, high pass around 40hz and low pass about 100-120hz.


Thanks for the info and the amp recomendation šŸ˜€

The filtering though is different to what i have read everywhere else. Im not saying your wrong obviously just im real confused.

I always thought for example 1 channel with sub i would lpf the sub around 80-100hz 

And then 2nd channel with mid/top speaker i would hpf around 100-150hz


Posted By: concept-10
Date Posted: 11 February 2020 at 9:20pm
You still have to high pass the tham At 40ish then low pass it at 1-120 then high pas the mid top.


Posted By: concept-10
Date Posted: 11 February 2020 at 9:21pm
Where are you based bud?



Posted By: nilspixel
Date Posted: 03 March 2021 at 6:11pm
any news on the project?


Posted By: slaz
Date Posted: 03 March 2021 at 10:03pm
Originally posted by concept-10 concept-10 wrote:

This would do for your bass, bridged, with a subsonic high pass filter and a low pass to your mid tops, not a bad price.
https://www.bassfacecaraudio.co.uk/product/db21-21-channel-bridgeable-stereo-12v-power-amplifier-200w-verified-rms-power-output/db21" rel="nofollow - https://www.bassfacecaraudio.co.uk/product/db21-21-channel-bridgeable-stereo-12v-power-amplifier-200w-verified-rms-power-output/db21


Thats a class AB amplifier. It'll waste plenty of your battery power as heat.


-------------
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON


Posted By: Final_Animal
Date Posted: 15 February 2024 at 10:44pm
How did you get on with this?


Posted By: Jack1991
Date Posted: 16 February 2024 at 7:20am
Originally posted by Final_Animal Final_Animal wrote:

How did you get on with this?

It went really well thanks, really happy with the outcome. Doesn't get used often at all now to be honest. But it was a good fun project. I've really been enjoying learning it all. I still keep going back through old posts, and now understanding stuff I didn't at the time, which all helps.

Here is the build thread I made whilst making it:
https://forum.speakerplans.com/lockdown-audio-a-12v-3way-small-rig-build_topic105202_page1.html" rel="nofollow - https://forum.speakerplans.com/lockdown-audio-a-12v-3way-small-rig-build_topic105202_page1.html





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