I need help, professional help!!!
Greetings from Tasmania, Australia, where most sane people buy their speakers!
Once again I find myself doing things back to front. This is what happens when you live down under!
Take a look at the schematic that I will attach or post and tell me what the impedance of my speaker box will be. Have I got it all rong? I am aiming for 3-6 ohms. My father says I have only enough electrical knowledge to make my work dangerous, is he right? Will she blow? I am a wood machinist after all.
I will pay $5ea. (into the DIY kitty) for the first two sensible suggestions, advice or ideas . Tossing the speakers out and starting again is not an option.
I will also pay $10 for a (really) funny audio anecdote.
Here's a snap of the proposed crossover:
PS. I don't know anything about HTML so if the picture or link doesn't appear on this post please get back to me and I will try again.
Cheers and bye for now, Phil Elliott
Greetings from Tasmania, Australia, where most sane people buy their speakers!
Once again I find myself doing things back to front. This is what happens when you live down under!
- I purchased a nice subbie (12" Venom) from ebay. (That's how this epic started).
- I really liked the thumping shockwaves that came out of it, so I got another one - they were new and only cost me $40ea + $15 postage.
- When I looked at them sitting on my carpet, I suddenly realised that I would have to build a box for them.
- I want a pair of low impedance, high power, full - range speaker boxes to match the rest of my surround speakers.
- I decided to buy four 6.5 inch DME Woofer/Mids (N178CS) which are a favourite of mine - yep, once again, they're cheap, with solid construction and a wonderfully satisfying sound. I realise they can only handle 50W RMS, so I intend to paralell two for each box's midrange section. I know they work really well between 100Hz right through to 5kHz at a good volume level.
- Finally I decided on a pair of nice looking silk dome tweeters from Altronics (C2003) they are rated at 80W RMS with a frequency response of something like 2k - 20k.
- My amp has an output limited to about 120W RMS.
- Two 6.5" fifty watt mids will handle 100 watts in paralell?
- The tweeter will remain intact even though it's rated at 80 watts because I am only using it from 5kHz and over??
- I will need to build a box inside the box to stop the subbie from pumping that pair of mids?
Take a look at the schematic that I will attach or post and tell me what the impedance of my speaker box will be. Have I got it all rong? I am aiming for 3-6 ohms. My father says I have only enough electrical knowledge to make my work dangerous, is he right? Will she blow? I am a wood machinist after all.
I will pay $5ea. (into the DIY kitty) for the first two sensible suggestions, advice or ideas . Tossing the speakers out and starting again is not an option.
I will also pay $10 for a (really) funny audio anecdote.
Here's a snap of the proposed crossover:
PS. I don't know anything about HTML so if the picture or link doesn't appear on this post please get back to me and I will try again.
Cheers and bye for now, Phil Elliott
Attachments
Hello inductor.
In reply to your first question "Why place mids and woofer in series?"
The simplest explanation I can give is that; "Due to the number of speakers inside the box and their individual impedance, something has to be placed in series with another section in order to get the stated parameter of 3-6 ohms overall average box impedance (the mean average of measurements made all along the audio spectrum). I tried (on paper at least), a series connection between woofer and tweeter but this gave me a figure of around 3 ohms which is getting (almost) too low.
To your second question; If my amp frazzles at 4 ohms (a minimum of 4 ohm - remember that the rest of the spectrum will be higher than 4 ohms impedance), I will send it back to the manufacturer and ask them to take another look at their design. To sum up what I have stumbled through here;
YES I am very confident that my old Sony amp will cut the mustard.
Thankyou inductor for your questions and observations, there are plenty of mugs out there that don't know the difference between series and paralell crossovers and I am only new to the concept of series crossovers. This is why I have posed the question; "Will it work?" I am still not sure if it will work and may just have to try it out and see.
Sincerely, Phil
In reply to your first question "Why place mids and woofer in series?"
The simplest explanation I can give is that; "Due to the number of speakers inside the box and their individual impedance, something has to be placed in series with another section in order to get the stated parameter of 3-6 ohms overall average box impedance (the mean average of measurements made all along the audio spectrum). I tried (on paper at least), a series connection between woofer and tweeter but this gave me a figure of around 3 ohms which is getting (almost) too low.
To your second question; If my amp frazzles at 4 ohms (a minimum of 4 ohm - remember that the rest of the spectrum will be higher than 4 ohms impedance), I will send it back to the manufacturer and ask them to take another look at their design. To sum up what I have stumbled through here;
YES I am very confident that my old Sony amp will cut the mustard.
Thankyou inductor for your questions and observations, there are plenty of mugs out there that don't know the difference between series and paralell crossovers and I am only new to the concept of series crossovers. This is why I have posed the question; "Will it work?" I am still not sure if it will work and may just have to try it out and see.
Sincerely, Phil
Agreed 100%. Farmerjack, a 2.5 way is a system that will utilize a box for each woofer and and a box for each 2 way that you will build from the mid bass and tweeters. You will require a plate amp for each of the woofers or you have the option of getting a more powerful plate amp and putting the two woofers in one box. Then the mid/high boxes can be placed more where you like as they are smaller and the (one or two) woofer(s) can be put out of the way. This is assuming you have a WAF to consider and that you would like to have this less conspicuous than perhaps when you were a young'n. Are you with us so far?
I hardly think it's an option with a less than 85dB sensitivity of the woofer, 90 for the mid bass and one would assume around 93 for the tweeter. I can't find that exact model but this may be the one to which Farmerjack refers., the 3004 rather than the 2003?
Altronics - Your One Stop Audio Visual & Electronics Supplier
Doing it this way will save you a lot of headaches with the XO.
Altronics - Your One Stop Audio Visual & Electronics Supplier
Doing it this way will save you a lot of headaches with the XO.
Cal, Re: 'less than 85dB sensitivity of the woofer' - good point...
A classic mistake that most newbs make, attempting to buy a bunch of drivers & stick them in a box.... the importance of the relative sensitivites of the drivers is vastly underestimated, if taken into consideration at all...
A classic mistake that most newbs make, attempting to buy a bunch of drivers & stick them in a box.... the importance of the relative sensitivites of the drivers is vastly underestimated, if taken into consideration at all...
When connected in series, the component with higher impedance sees higher voltage, thus sharing higher power.
So, the unit of paralleled mids has a lower impedance, thus lower power. It's an elegant and smart solution to a common requirement - keeping the woofer loud and attenuating the mid.
Be careful though, around the low end resonant frequency of the mid, its impedance would be very likely higher than the woofer, so the woofer gets less to eat around here.
The xover portion might not side step this problem perfectly (it has another set of problems), so there'd be a strange zone where the roll-offs of mid and woofer are not what you want.
So I'd suggest a LCR in parallel with the mids to suppress the impedance peak.
ps. try measure the impedance curves of the drivers
So, the unit of paralleled mids has a lower impedance, thus lower power. It's an elegant and smart solution to a common requirement - keeping the woofer loud and attenuating the mid.
Be careful though, around the low end resonant frequency of the mid, its impedance would be very likely higher than the woofer, so the woofer gets less to eat around here.
The xover portion might not side step this problem perfectly (it has another set of problems), so there'd be a strange zone where the roll-offs of mid and woofer are not what you want.
So I'd suggest a LCR in parallel with the mids to suppress the impedance peak.
ps. try measure the impedance curves of the drivers
Phil Elliott, why such a "goofy" xover? NPI
Is that supposed to be a (all) series xover?
Why the variable resistor/L-PAD (100W Poly?) in series?
The problem is that the impedance sometimes gets lower (depending of xover o.c.), can you handle a 2 ohm load as an example? Do you feel comfortable, from the two drivers you have 3 Ohms.
I looked at the mids drivers and they look nice. http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=330530430674
Last edited:
Will it work?
Hello CLS, You just earned a $5 donation towards the DIY website's running costs. Be proud and hold your head high.
You know, I had no idea why those inductors went into the tweeters, (and therefore the mids as well)! - I just copied what everyone else was doing! But I'll be factoring them in from now on because it makes perfect sense when explained in laymans terms. Cheers
PS.That's what I love about this site; Good people, with a collective 'wealth' of knowledge. Awesome. Thankyou.
Hello CLS, You just earned a $5 donation towards the DIY website's running costs. Be proud and hold your head high.
You know, I had no idea why those inductors went into the tweeters, (and therefore the mids as well)! - I just copied what everyone else was doing! But I'll be factoring them in from now on because it makes perfect sense when explained in laymans terms. Cheers
PS.That's what I love about this site; Good people, with a collective 'wealth' of knowledge. Awesome. Thankyou.
Hello again Inductor. You're right mate, it is a really goofy looking thing, but it's the best that I could come up with. I don't like to copy everyone elses work, so although I borrow good ideas from good designers, I try always to add something in the process.
The issue about low impedance is another good point.
The symbol I used for the 100W Polyfuse is probably all wrong but that was the one that helps me to visualise the internal 'auto-protect-and-reset' action of the device. BTW they only cost 50c so if they save the drivers from overload as they should, then I think they are a good investment. My last 5 or 6 designs have included them on the crossover board.
farmerjack61, You have to many issues. At the end they might work or not.
I see that you use a polyswitch. That's ok, but needs to be calibrated, not just a 100W.
I didn't check anything else because as PeteMcK said, to many components for my taste (zobels).
Might not be goofy after all, if it works.
It's just the series xovers (that I don't like), and (maybe) they seem to work for you. With the parallel xover on tweeter. You know the series gives a symmetrical shape curve atten. for both sides (from my memory).
I see that you use a polyswitch. That's ok, but needs to be calibrated, not just a 100W.
I didn't check anything else because as PeteMcK said, to many components for my taste (zobels).
Might not be goofy after all, if it works.
It's just the series xovers (that I don't like), and (maybe) they seem to work for you. With the parallel xover on tweeter. You know the series gives a symmetrical shape curve atten. for both sides (from my memory).
That's sort of a good experience.
Last edited:
RE; I didn't check anything else because as PeteMcK said, to many components for my taste (zobels)
Hi there Inductor; I found nothing in the FAQ link you posted about Peter's comments on Zobel networks can you give me the link to what he said? or is it one of the responses from this site? PS. I don't even know who this bloke is!
My approach to electronics involves active, energetic, enquisitive experimentation with a "try it out and see approach".
The circuit that has led to a few 'less than positive' replies, is of my design and I am posing some simple questions in a bulleted and numbered format. But few have attempted to use their intelligence (with the exception of CLS) to answer or comment on those questions!
One of my old teachers told me years ago that; "The essence of good design is simplicity" - If what he said is true, (and I believe it is) then we need to reduce the amount of 'cut and paste' in our replies, and increase their informative content.
Also, you said that "the polyswitch is ok but needs to be calibrated, not just a 100W" - What on earth are you talking about?
Hello Cal, I wish I was up there now, I just opened a big can of worms and reckon I could catch a brace with that kind of bait. (just like that old sony ad with the bloke in the dinghy watching television as he waits for a bite....."It's a Sony" he yells as he lands one! Or is that an Aussie advertisment? It was pretty popular over here.
Luckily I don't have a Waf, she left with me dog, the pain has subsided now, and the bad dreams are all gone, But I really miss him.
I am just about to google "Plate Amp". Might be a good time to plug in the old Jimmy Buffett recording. Or my new Tim Obrien album "Chicken & Egg" Music is great.
Cheers and bye for now, Phil Elliott
Luckily I don't have a Waf, she left with me dog, the pain has subsided now, and the bad dreams are all gone, But I really miss him.
I am just about to google "Plate Amp". Might be a good time to plug in the old Jimmy Buffett recording. Or my new Tim Obrien album "Chicken & Egg" Music is great.
Cheers and bye for now, Phil Elliott
Hello again. My intention is to increase the SPL of the bass driver using a box like some of the P.A. bass bins you might see at a concert. I have also seen these designs in a fane catalogue of speaker drawings. I reckon they will give me a bit more bang for my buck i.e increase the SPL of this particular 12" driver and not the other mid and hf drivers which should match nicely, they (one DME + one 90db silk dome tweeter)
sound warm and funky in a 48L (tall skinny) ported box.
I am not really keen to use more amplifiers, as my aim is to simplify things. Use one amp and one box for the four drivers. As I said before; I will have to section off the mids, so I will build a box within a box. This is the part where the cabinetmaker can do his bit to increase the SPL, as that parameter is not only controlled by electronics but by other environmental factors. No?
sound warm and funky in a 48L (tall skinny) ported box.
I am not really keen to use more amplifiers, as my aim is to simplify things. Use one amp and one box for the four drivers. As I said before; I will have to section off the mids, so I will build a box within a box. This is the part where the cabinetmaker can do his bit to increase the SPL, as that parameter is not only controlled by electronics but by other environmental factors. No?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.