Buiding new xovers for Infinity SL40 speakers - diyAudio
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Old 6th April 2006, 06:47 PM   #1
killtoy is offline killtoy  United States
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Default Buiding new xovers for Infinity SL40 speakers

Unfortunatly or unfortunatly for me the 8" passive woofers on a pair of Infinity SL40 speakers has become damaged beyond repair. I have an older set of Infinity 8" non passive woofers that where in an older Reference series set of speakers. I would like to replace the passive woofers with these 8" woofers. My problem is what is the best way to go about this project? I know that I will have to convert the xover to a 3 way configuration and am not sure of the best way of going about this. I would prefer to upgrade the xover altogether with newer parts. I am pretty new to the whole scheme of things and was looking for some advice on parts selection and proper values. I have emailed Infinity and have a line diagram of the xover I just am not sure if it is still feasibel to use it with the new drivers?

Any help would be greatly appreciated


Matthew
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Old 6th April 2006, 08:10 PM   #2
dfdye is offline dfdye  United States
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I just looked for some information about the woofer driver specs on that model, but I can't find anything. You may want to check with Madisound and see if they know of a drop-in replacement for that series. Check here: http://www.madisound.com/replace.html and see if it looks like they could help you. They have a pretty good selection of drivers, so my guess is they could find something that would work even if they don't have a direct match. From what I can find, the "bass driver" as they call it is an 8" polypropylene cone, but I can't find anything about a passive radiator on that series. Can you post some pictures or some more information?

As for building new xovers, you may have to tweak the cover point or compensate for differences in the new driver sensitivity, but I would try and find a driver that would be a drop in replacement at first. If you post pictures of the xover network, I am sure somebody will help you figure out the circuit and figure out how to modify it to suit your needs.
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Old 6th April 2006, 10:34 PM   #3
killtoy is offline killtoy  United States
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I have attached a pdf file of the technical manual that Infinity sent me. Would it be possible to upgrade the speaker system to a 3 way systenm without a lot of hassle or am I better off just replacing the bad drivers?
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Old 7th April 2006, 12:39 AM   #4
dfdye is offline dfdye  United States
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Of course you can!!! The question is whether it will sound anywhere close to normal!

Honestly, without rebuilding the cabinets, my guess is that anything you do with those specific drivers will probably get a little funky. Reason being is that the passive radiators will act like a port by extending the low end of the 6 1/2" woofer. Granted, if you put the woofers in a smaller sealed enclosure, it should tighten up the bass, but without the Thiele/Small paramaters, there is not really a good way to predict how. The most likely scenario is that you get something that will be close, but not quite right.

If you are OK with this and want to add in a crossover stage ~300-500 Hz, you could drop in a decent 8" woofer into the existing hole and just see what happens!

A decent starting point on the cheap would be the DAYTON DC200-8 http://www.partsexpress.com/pe/showd...number=295-310 I have never used this particular part, but they have gotten pretty good reviews for this series at this price point, and the price is definitely right to see if this is anywhere close. The sensitivity is a little off, but there can be some tricks played with the Xover to compensate for this. Also, check the cutout in the cabinet to make sure it can take 8.125" since this driver is slightly larger than the one you are replacing.

Alternately, the GOLDWOOD GW-8028 ( http://www.partsexpress.com/pe/showd...number=290-355 ) may be an option as well.

Realistically, I am going to bet you won't get a ton of extra bass out of this setup. If you are looking to drop the frequency response, I would recommend an external sub. HOWEVER, if after all of this, you still want to try putting the 8 in the cabinets, knowing it will probably be a little goofy and will probably make most of the members of this board throw something at me for suggesting it ( ), I'll be happy to draw up a quick circuit you could add to your existing crossover network to make it a 3 way. Just let me know.

David
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Old 7th April 2006, 03:29 PM   #5
killtoy is offline killtoy  United States
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Well now I am not sure what to do. I already have the drivers and it looks like they will fit it will be a snug fit though. I am willing to give the 3 way a try and see how things go. If I do not like the sound I may just try to hunt down a pair of passive woofers as replacements then. I can always use the 8" drivers for another project down the road.

Thank you for your helpf and the circuit diagram would be much appreciated.

Oh on another subject if I do find a set of passive woofers as replacement. Would upgrading some of the components on the 2 way crossover really make much of a difference? I know these are not the top of the line speakers but even a small improvement would be pretty neat to hear. I am mainly trying to learn small bits here and there to gain a better knowledge of speaker building and the electronics involved?

Matt
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Old 7th April 2006, 11:56 PM   #6
dfdye is offline dfdye  United States
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I will get on that tonight! I just want to play with a couple of things, but could you tell me what 8" drivers you have? You mentioned something about having some already.

David
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Old 8th April 2006, 12:53 PM   #7
killtoy is offline killtoy  United States
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Default The drivers I have are:

I have a pair of older Infinity Model# 902-5030 8" woofers. They where in an older pair of Reference speakers that I found at a flea market. The rest of the speakers where severely damaged but the 8's where in good condition. These are the ones that had the clear looking woofer cone. I believe they are 4 ohm drivers.

Thanks for your help


Matt
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Old 9th April 2006, 02:50 AM   #8
dfdye is offline dfdye  United States
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Alright! I'll see what I can do.

David
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Old 9th April 2006, 06:37 PM   #9
dfdye is offline dfdye  United States
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The easiest way to make your 2 way into a 3 way is to add in a second order network in front of your existing crossover (see attached image). Assume that the existing network is the high pass speaker of the circuit and send the output from your new high pass stage into your old crossover inputs. In order to compensate for sensitivity mismatches, I would add in an L-pad to allow you to change the relative power going to the 8” vs. the other drivers. This way you can change the volume of the drivers to ensure that they match. You don’t need to do this for the existing speakers since they are already matched.

For a crossover point of 500Hz, I would use the values:

C1: 25 uF
L1: 4 mH
C2: 40 uF
L2: 2.5 mH

This assumes that your driver is indeed 4 ohms. If you measure it and it is closer to 8 ohms, then I would use these values:

C1: 25 uF
L1: 4 mH
C2: 20 uF
L2: 5 mH

Of course in both the high pass stage is the same, but I think you can see how crucial it is to get the right impedance of the woofer before you order parts. Either way, this should be pretty straightforward to put together.

Here are some links to Parts Express components that should be pretty good for this application. You can go cheaper, but indicated you wanted to upgrade crossover components in the first place, so I went for middle of the road crossover electronics that would be better than the cheap stuff, but not have the cost of Rhino Horn.

For 4 ohm

L-Pad $7.80
http://www.partsexpress.com/pe/showd...number=260-262

40 uF cap $9.41
http://www.partsexpress.com/pe/pshow...TOKEN=55195563

25 uF $5.90
http://www.partsexpress.com/pe/pshow...Number=027-438

2.5 mH Inductor $6.63
http://www.partsexpress.com/pe/pshow...=255-270&DID=7

4 uH $8.28
http://www.partsexpress.com/pe/pshow...=255-280&DID=7



For 8 ohm

L-Pad $7.80
http://www.partsexpress.com/pe/showd...number=260-262

5 mH inductor $9.21
http://www.partsexpress.com/pe/pshow...=255-284&DID=7

25 uF $5.90
http://www.partsexpress.com/pe/pshow...Number=027-438

20 uf $4.95
http://www.partsexpress.com/pe/pshow...Number=027-436

4 uH $8.28
http://www.partsexpress.com/pe/pshow...=255-280&DID=7


If you need anything else, let me know and I will get you some more details.
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