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Multi-Way Conventional loudspeakers with crossovers

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Old 30th December 2003, 04:22 AM   #1
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Default Need help choosing 3-way drivers

My roommate has some 3-way speakers that are

length 10.25"
width 12.25"
height 25.25"

They are constructed of 1/2" MDF and currently consists of a 10" woofer, 4" midrange, and 3" tweeter. They are all made of some cheap paper cones and some of the drivers are torn. The enclosure is 1.46 cubic ft with a 1.75" port that is 5" long. I need some help picking out drivers. I am an electrical engineering student in college and do not want to spend too much money. Here is what I have found, please let me know if this will work as I am new to home audio. I am more of a car audio kind of guy.

10" Woofer

PEERLESS 850146 CSX 10" WOOFER (23-1800Hz)

5" Midrange

Seas MP14RCY/P (100-4000Hz)

20mm Tweeter

Seas 20TFF (H830) (3500 - 25000Hz)

I was thinking of making crossovers for the woofer and midrange @ 150Hz and crossovers for the midrange and tweeter @ 3750Hz. I downloaded WinISD and I'm not sure if I used it right. I plugged in all the parameters for the box I had and a Peerless CSX and I think I will only get a response from 47 - 200Hz from the woofer. Please let me know if this is possible and if it will sound any good. I would like to spend less than $300 for the pair. I am capable of making crossovers but I do not know what order I should make them (1st, 2nd, 3rd, etc.) Please let me know if this is a good setup, what drivers you would use, what frequency you would make the crossovers and at what order. This will be my first DIY home audio project and I could use all the help I can get. BTW I think there will be 100watts RMS per channel if this helps any. Please let me know what you all think, as I have seen some pictures of some very impressive setups from many of you. Thanks for all your help in advance.
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Old 30th December 2003, 03:56 PM   #2
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Ok so I've been looking at parts to make the crossovers with and it looks like realistically I'm going to have to cross them at 130Hz and 4000Hz. Do you all think this is ok with these drivers? Also I still need to know if these drivers will work together in this enclosure. Please help.
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Old 3rd January 2004, 01:53 AM   #3
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Ok, so nobody has responded to my post. I would like any suggestions about what drivers to buy. If I don't get any responses soon, I think I'm just going to buy the drivers and see what happens.
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Old 3rd January 2004, 05:38 AM   #4
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It can be a little slow around here at times......

Multiway Main speaker projects from scratch arent for the faint hearted.

Which is why i would follow some one elses Plans,because they wouldve spent the 50hrs optimising the crossover etc....

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Old 3rd January 2004, 07:07 AM   #5
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Hi

If you are doing a three way system, then use a closed back midrange instead. This is important to the design of the passive crossover, so that we can damp the impedance peak at resonance with ease. If you choose an open back midrange like the MP14RCY/P, then it needs an enclosure of its own. The box will then modify the electrical impedance. It will be shifted to another frequency and have a different amplitude, and if a ported box, will introduce a secondary impedance peak too. Damping the peaks at resonance that are modified by the box is very tricky, and involves multiple tank circuits with a tight tolerance factor. Thats why closed back midranges are always used in a 3-way system, as the box doesn't modify the electrical impedance - there is no box. To damp the impedance peak is then simply a matter of using a series notch filter, and plugging the necessary numbers into the formulas for that.

Regarding the CSX 850146 10", you need to change the port size. Use a 3" diameter port, 25" long. This is longer than the depth of your enclosure, so you need to use a 90 degree elbow bend in the port, and ensure that it doesn't restrict air flow in the bend. This port tuning of ~22Hz will flatten out the response curve, and the large diameter will highly reduce port noise and distortion at high power input levels.

I'd aim to set the crossover point at at 3.5KHz minimum on the 20TFF. You can go a little higher, but don't go any higher than 5KHz or crossover nulls will start appearing closer and closer to your listening area; decreasing the dispersion window of "good performance".

So look around for a closed back tweeter that will suit your application. The CSX 10" can be crossed as high as 1KHz actually. If you look at the response curve from Peerless, you'll notice its dead flat right throughout the midrange and up to this point. Actually, you could push it a little further as it's not beaming much a half octave above this point, so 1.5KHz can be considered maximum. I'd expect it to perform pretty well here, its got an aluminium shorting ring in the motor structure to reduce distortion, and intermodulation distortion at the upper limits is reduced by using a bass reflex box for the 850146. But anyway, thats besides the point as your doing a three way system, so theres no need to push the woofer crossover point this high at all. I'd look for a closed midrange driver that can be used between 200/300Hz and 4KHz, and make the crossover points between the subsystems at these frequencies.

Adrian
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Old 3rd January 2004, 01:47 PM   #6
sreten is offline sreten  United Kingdom
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You want some good advice ? Don't even go there !

You cannot just buy drivers and then hope to get them to work
together. It will go horribly wrong, I will guarantee it. Good 3-way
crossovers are expensive and you can't stay within budget.


with that cabinet build this instead, the Dayton Lyra:

http://www.speakerbuilder.net/web_fi...a/lyramain.htm
(hope the link works, doesn't at the moment).

Convert to a sealed box. I also reccommend lining the cabinet
walls with cheap vinyl floor tiles, say five layers, covering the main
centre section of the panels - say with a 1" gap around the edge.

sreten.
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Old 3rd January 2004, 03:13 PM   #7
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Quote:
Don't even go there
i used to "design and build" loudspeakers - for a long time.....

....i ended up buying a brand new set of ATC scm100sl - no matter how much ressources you throw at such a project, it can't be done...in the beginning it looks very simple - but i'd rather put a man on mars........
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Old 3rd January 2004, 04:03 PM   #8
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Hi again

Just read the enclosures you talk about are built from 1/2" MDF. Has it got any bracing? I strongly reccomend adding another layer of 1/2" MDF to the top of that in effort to add strength to the enclosure, and shift panel resonances out the range in which it can be excited. Wall thickness will then be 1" thick total. It should be a pretty easy task, especially if theres no finishing on the enclosures already. If its painted or something, then sand it down until its completely smooth, and then use PVA glue all over to attach an extra layer of MDF to it, and clamp it down securely while drying. Resting a heavy object on top of the pieces being glued will also serve the same purpose as a clamp if you don't happen to own any clamps large enough for this purpose.

Adrian
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