It has to do with what the frequencies see as they pass through the circuit. In this case, if you were an ultrasonic frequency, it will pass through the 0.1uF cap and the Dayton cap and virtually shunt and short to ground. Some amplifiers will go into protect with a circuit such as this without any resistance in the path of the 2 caps. It can cause instability, and maybe distortion, but the above is the reason why.
Summation refers to the frequency response summation and result of the drivers and xover as a whole in the cabinet as intended.
Sometimes Sonicaps can sound a bit forward, so they may be okay with the BG's. They also have a touch of sssibilance, which the BG lacks completely. It may just fill everything back in as it should be. Personally, the ClarityCap SA is cheaper than the Sonicaps, and I feel is a cleaner and better resolving cap where a lift of brightness is not required. Just my 2c.
Have fun!
Wolf
Summation refers to the frequency response summation and result of the drivers and xover as a whole in the cabinet as intended.
Sometimes Sonicaps can sound a bit forward, so they may be okay with the BG's. They also have a touch of sssibilance, which the BG lacks completely. It may just fill everything back in as it should be. Personally, the ClarityCap SA is cheaper than the Sonicaps, and I feel is a cleaner and better resolving cap where a lift of brightness is not required. Just my 2c.
Have fun!
Wolf
I'm looking at the crossover schematic in the ZX Spectrum link from the OP, and I now see that 0.1uF right across the series inductor for the woofer, and then a 15uF cap from there, right across the woofer to ground. Why in the world is that 0.1uF cap there? It doesn't appear to do anything for the sound, except maybe couple some extreme highs to the woofer, and why would one do that? It does provide a direct capacitive load to the amp (just looking at the two caps in series, the load is 0.0993uF right across the amp's output with only the speaker wire in between - still a bad load), which is indeed a Bad Thing.
This must be a mistake. I've certainly never seen a crossover schematic like that. It's right there as C3 on the schematic and BOM, but there's not enough text description of the crossover to give a hint to why it's there.*
If you really want that cap in there, I agree with putting a 4 ohm resistor in series with it (BEFORE connecting up an amplifier), but I'd take it out completely.
* I recall as a teen reading the "Circuit Description" portions of every Heathkit manual I could get my hands on. They often described every component, or at least every "unusual" component in the circuit. These weren't always right, but I learned a whole lot about electronics from them.
Don't take it out!
If you take out the 0.1uF cap, you have eliminated all of the notching of the response for the M6a. That is called a 'tank' circuit, and provides a notch to suppress breakup in a driver. It's a lot less expensive than using a full LCR, and does the same thing.
It is supposed to be there. Were the Dayton a non-polar electrolytic cap instead, the ESR would be high enough I wouldn't worry about it and just build it as specified. The lower ESR of the Dayton makes it a possibility for problems.
FWIW- I've used this scenario in a lot of xovers, but I have been careful to at least apply 2 ohms in the Cap-cap string to ground. The 4 ohm after the 0.1uF is the simplest, and least influential addition to make this safer.
Later,
Wolf
If you take out the 0.1uF cap, you have eliminated all of the notching of the response for the M6a. That is called a 'tank' circuit, and provides a notch to suppress breakup in a driver. It's a lot less expensive than using a full LCR, and does the same thing.
It is supposed to be there. Were the Dayton a non-polar electrolytic cap instead, the ESR would be high enough I wouldn't worry about it and just build it as specified. The lower ESR of the Dayton makes it a possibility for problems.
FWIW- I've used this scenario in a lot of xovers, but I have been careful to at least apply 2 ohms in the Cap-cap string to ground. The 4 ohm after the 0.1uF is the simplest, and least influential addition to make this safer.
Later,
Wolf
Photos fixed. 4.7Meg of inline photos is not a good idea. Please see this thread:
http://www.diyaudio.com/forums/everything-else/183084-pictures-why-not-attach-them.html
Thanks!
- hehe thanks for that. Sometimes I find it a bit annoying when I'm browsing different forums and the attached images arent shown to non-members, but i will use it and link to the pic gallery (which will dissaper in 6months if it is not visited 🙁 )
thanks for the explanation! I need to read up on filters and get my basic real good in terms of frequencies and what gets filtered where and relation to the values of caps, res and inductors :/
thanks for the informative inquiry.
I am curious as to why would you recommand a 4ohm in series with the 0.1uF? why not 2Ohm or 8Ohm? will it affect the impedance Matching circuit for the tweetera and the Mills 8Ohm will need to be changed to something else as well?
I think you say 4ohm in order to match the impedance of the woofer so it would look like a 4Ohm load...?
oh and one more unrelated questions... I am limited on wire that is available to me :/ so i have Vampire Speaker cable that is standed core 14-16 gauge and a woven copper shield, each one insulated with teflon. The problem is that I will need 4 pieces of 4ft for each driver max and I was wondering if i can use the wofen copper shield as my return/ground connection and if that will affect the audio quality?
What gauge would you recommend?
I also have some nice RGBY Belden Video Cable with 12AWG cores all inslulated that I can take apart and use that wire to wire the drivers? what do you think?
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Hi,
If your amplifier has an output inductor (most have) its not an issue at all.
Any resistance added will detune the notch filter and reduce effectiveness.
The paranoid could add a 2.2R resistor, but most likely not needed.
rgds, sreten.
If you're talking about internal driver wiring you don't need any "special" wire. 18 awg solid thermostat wire will work fine as will 18 awg stranded hookup wire. Before you get concerned about wire gauge, remember that everything is flowing through the ~24awg leads on the XO components.
Just get some thermostat or hookup wire from Lowes, Home Depot, or local hardware and call it good.
Just get some thermostat or hookup wire from Lowes, Home Depot, or local hardware and call it good.
Now I see. The inductor is doing double-duty. It's of course the series coil in the 2-pole low pass, but it's also the inductive part of a parallel resonant circuit with that 0.1uF cap. I looked at the driver's data, and sure enough the frequency response graph shows a sharp peak at 9kHz, and a 3mH and 0.1uF just happen to resonate at 9193 Hz. Odd how one-digit-precision components work out just right.
I put it in LTspice and found the capacitance reactance goes to about 8 ohms at 200kHz, then below 1 ohm at 2MHz. I added a resistor and small inductance between the speaker connection and the crossover which keeps the impedance from dropping. I came up with 20 ohms and 50uH as "good" values. As sreten said, most amps have an output inductor and resistor in parallel, but I don't think the speaker should rely on that. I've attached the LTspice file as a .txt file, remove the .txt extension to load it in.
View attachment cross1.asc.txt
If you run a simulation and add a trace that's v(n001)/I(V1) you'll get a plot of impedance, and with the added resistor and inductor it flattens out just below 20 ohms instead of going below 1 ohm at 2MHz.
- thanks man, i think it should be fine, if my AMP/ Reciever blows up i guess i'll know lol. I have an 85W per ch Onkyo.
-idk if i want to put thermostat wire in there but I will probably take apart the video cable and use those wired.
- thanks for the info
Whoah, I'm late to the party. 
Anyway, it's me, Paul Carmody. You guys have done a good job of deconstructing my use of C3. The one thing to also keep in mind is that the inductance of the tweeter filter will also come into play at such high frequencies.
I did run this design by a few XO and amp gurus a while back about this very issue just to be sure, and they pretty much concluded what we all did here.
As Wolf said, this filter is sometimes called a "tank" filter, or "elliptic" filter. If you look at my designs, I tend to use it a lot because it's a cheap way to get a notch filter by using less components. So far, no one's amp has blown up yet. 😱
Now, on with the show!
Anyway, it's me, Paul Carmody. You guys have done a good job of deconstructing my use of C3. The one thing to also keep in mind is that the inductance of the tweeter filter will also come into play at such high frequencies. I did run this design by a few XO and amp gurus a while back about this very issue just to be sure, and they pretty much concluded what we all did here.
As Wolf said, this filter is sometimes called a "tank" filter, or "elliptic" filter. If you look at my designs, I tend to use it a lot because it's a cheap way to get a notch filter by using less components. So far, no one's amp has blown up yet. 😱
Now, on with the show!
Whoah, I'm late to the party.
I did run this design by a few XO and amp gurus a while back about this very issue just to be sure, and they pretty much concluded what we all did here.
As Wolf said, this filter is sometimes called a "tank" filter, or "elliptic" filter. If you look at my designs, I tend to use it a lot because it's a cheap way to get a notch filter by using less components. So far, no one's amp has blown up yet. 😱
Now, on with the show!
Hi Paul,
Sorry I butchered your name in the tittle :/, myself being with an unusual last name I know how annoying that could be sometimes.
Thanks for chiming in!
I hope in the next two weekends to complete the enclosures and have the speakers running 😀..... but no paint job :/
Big update 😀
Hi guys,
So I did a lot over the past two weekends and I am soo close to having them functional! hehe
First I'll start off with the port. It called for a 3.5" port but the "Precision Port" I got from PartsExpress were made for ports of 4"+ so I had to trim the two flares by 1/4". The precition port describles that the overall lengt of the port should be 1" longer than the port you need because of the big flares they have so mine is 4.5". I had to trim the two flares and the ring that connects them. There is a small gap at the joints that I tried to cover with bondo... but that will need to be taken care of :/
Just .5" longer
Had to trim the flares by 1/4" and the connecting ring by 1/5"
Hot Glue should do fine in this case... hopefully
The bondo.... looks like crap and i didnt completely eliminate the gap... need to work on it more. I figued I'l have to sand it down and the port will be painted with the enclosure
Made my own circle Jig out of plexiglass. Easy to do but must have your measurements right. My port holes were off by a hair and I had to do them by hand so they will have to be fixed before painting :/
Rear Port hole
I used a caliper and mounted my jig to the router bottom and used a caliper to measure from the blade of the router to the center of the circle and made my marking (my mistake was taking the measure not right at the blade and it was off by a hair :/)
The holes came out pretty good and I was happy with my first circle cuts with the router
Made my mounting hole markings with the speakers and face plates on.
I also cut the rectangular hole for the Neo3 tweeter with the jigsaw but you'll see it later.
Ok so while making the speaker mounting holes I managed to have my impact driver roll and fall on my M6A speaker and dent it
.... so yeah be careful :/ had to order another even though I think this one will still work.
Than I did all the in insulation for inside the speaker with some egg carton foam from parts-express
Am I doing it right? lol
Than I worked on mounting the crossovers on the removable bottom.
-I decided to make insulation feet out of some grommets I found online. I got two sizes and apparently they fit perfectly within each other and should do a good job 🙂
Overkill? Maybe hehe
Used some 1 1/2" #6 screws but I could have gone longer. Here is how it looks with the "crosover insulation feet" screwed to the screws on the crossover
-Mounted
Here is how the foot looks. Just a little squeeze on it.
Complete crossover mounting
Here is how the crossover and the bottom plate attach to the speaker bottom.
crossover inside the speaker.... Is it a problem if my acoustic insulation touches the components?
Here is the baffle cutouts with the Neo3 rectangular cutout.... I also fogot to mention that I have a 45deg chamber on the back side of the M6A cutout so the woofer can breathe. Should I chamfer the Neo3 also? Idk I am thinking of sealing it or just putting acustic insulation on the back of it
Grand finale...... a preview 🙂
still lots to be done.... fix the ports, get the cables arranged... glue and screw the baffle.... than chamfer the edges of the baffles and the rest... wire everything...
I think I will primer the speakers white and let them be until the summer after all is done.
Also I will need to make a stand... bottom
here is the build album
p.s.
I tried using the forum upload feature and I kept getting errors and it got annoying after trying to upload 10+ images each time....
Hi guys,
So I did a lot over the past two weekends and I am soo close to having them functional! hehe
First I'll start off with the port. It called for a 3.5" port but the "Precision Port" I got from PartsExpress were made for ports of 4"+ so I had to trim the two flares by 1/4". The precition port describles that the overall lengt of the port should be 1" longer than the port you need because of the big flares they have so mine is 4.5". I had to trim the two flares and the ring that connects them. There is a small gap at the joints that I tried to cover with bondo... but that will need to be taken care of :/
Just .5" longer
Had to trim the flares by 1/4" and the connecting ring by 1/5"
Hot Glue should do fine in this case... hopefully
The bondo.... looks like crap and i didnt completely eliminate the gap... need to work on it more. I figued I'l have to sand it down and the port will be painted with the enclosure
Made my own circle Jig out of plexiglass. Easy to do but must have your measurements right. My port holes were off by a hair and I had to do them by hand so they will have to be fixed before painting :/
Rear Port hole
I used a caliper and mounted my jig to the router bottom and used a caliper to measure from the blade of the router to the center of the circle and made my marking (my mistake was taking the measure not right at the blade and it was off by a hair :/)
The holes came out pretty good and I was happy with my first circle cuts with the router
Made my mounting hole markings with the speakers and face plates on.
I also cut the rectangular hole for the Neo3 tweeter with the jigsaw but you'll see it later.
Ok so while making the speaker mounting holes I managed to have my impact driver roll and fall on my M6A speaker and dent it
.... so yeah be careful :/ had to order another even though I think this one will still work.Than I did all the in insulation for inside the speaker with some egg carton foam from parts-express
Am I doing it right? lol
Than I worked on mounting the crossovers on the removable bottom.
-I decided to make insulation feet out of some grommets I found online. I got two sizes and apparently they fit perfectly within each other and should do a good job 🙂
Overkill? Maybe hehe
Used some 1 1/2" #6 screws but I could have gone longer. Here is how it looks with the "crosover insulation feet" screwed to the screws on the crossover
-Mounted
Here is how the foot looks. Just a little squeeze on it.
Complete crossover mounting
Here is how the crossover and the bottom plate attach to the speaker bottom.
crossover inside the speaker.... Is it a problem if my acoustic insulation touches the components?
Here is the baffle cutouts with the Neo3 rectangular cutout.... I also fogot to mention that I have a 45deg chamber on the back side of the M6A cutout so the woofer can breathe. Should I chamfer the Neo3 also? Idk I am thinking of sealing it or just putting acustic insulation on the back of it
Grand finale...... a preview 🙂
still lots to be done.... fix the ports, get the cables arranged... glue and screw the baffle.... than chamfer the edges of the baffles and the rest... wire everything...
I think I will primer the speakers white and let them be until the summer after all is done.
Also I will need to make a stand... bottom
here is the build album
p.s.
I tried using the forum upload feature and I kept getting errors and it got annoying after trying to upload 10+ images each time....
Shouldn't be a problem if the insulation touches the components.
Sorry to see your bent driver! I'd definitely wait to listen to them until you can get it replaced.
Sorry to see your bent driver! I'd definitely wait to listen to them until you can get it replaced.
Cool, tnx!
Yeah I just got the new driver. Still need work to do. Need to do the base and wire everything. I'm on travel now sp it might be some weeks.
I did glue baffles and routed the edges! They look like proper speakers now hehe
Like I said tho, need to cut the bases, and wire.
I took apart this really nice Belden video cable and have 3 R/G/B coax cables. Coax cables would be cool for it, no? 18AWG, they have a braided shield tho, what do I do with it?
Yeah I just got the new driver. Still need work to do. Need to do the base and wire everything. I'm on travel now sp it might be some weeks.
I did glue baffles and routed the edges! They look like proper speakers now hehe
Like I said tho, need to cut the bases, and wire.
I took apart this really nice Belden video cable and have 3 R/G/B coax cables. Coax cables would be cool for it, no? 18AWG, they have a braided shield tho, what do I do with it?
I'm not sure I'd use those wires. I'd probably go with a decent ofc, 14awg or so. You can probably get a spool of it from parts express for hardly anything.
Why put the xover inside the cabinet , difficult if u have to modify and unnecessary exposure to noise and vibrations ...
The tweeter will be around 31 -32.5" from the floor. 31" now without the base and a 1.5" increase when I make the base/stand. Almost to ear level while sitting down. Why do you ask?
About the crossovers. I am going off Paul's original design so I don't anticipate to do any changes to the crossover but it will be accessible trough the bottom. The base will be 1.5" thick and that will mount to the speaker bottom with about 8 screws and than you will access the bottom plate which will be mounted with about 4 screws and once you pop that you will have the crossover and you will be able to change it out or whatever.
Crossovers outside of the speaker... yeah not very appealing visually and almost everyone eventually gets the crossovers inside the box and I don't think it will affect the sound enough... correct me if I'm wrong tho.
Yeah I think your right, those are kind of bulky and don't bend very well :/.
I have 12AWG Monoprice Speaker cable that is OFC but it does oxidize. It is stranded too. I wish I could get a nicer little "exotic" Neotech cable but the shipping kills it.
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Thats pretty low for good image height, 39-44 is about optimum , unless you are practically sitting on the floor..
OK ...
Nothing to do with performance , Maybe their girlfriends don't like it either ..... 🙂
Nah, it won't change anything about the sound, aside from the small amount of internal volume that the crossover takes up, but Paul's crossover is inside the box, so I wouldn't be terribly concerned with it. I'm sure there's someone who will say that magnets can affect coils and such, which is true, but at the distance that crossover is from the drivers, I wouldn't worry about it.
I wouldn't go too crazy on pricey cables. Something like this:
14 AWG High-Strand OFC Royal Cable Speaker Wire 50 ft. Roll 109-160
would probably be more than sufficient. At 10 bucks for a 50 foot spool, you'll have plenty left over for later too.
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