I have been a musician for about 15 years, spend most of my time in front of my computer, listening to other peoples music, games, work I have created, movies, I basically just treat my ears a 24 hour a day experience. But my old trusty purplies have died.
I am trying to come up with a good combination of mid/woofer and tweeter combo for a good accurate all round setup. I use Sennheiser HD280 Pro's, and AKG K-300's for headphones, but since my speakers have died, I have been forced into some $15 desktop PC Speakers...
So far I have been looking at the Vifa P17WJ-00-08 for the mid/woofer's just to start things off with an all round decent performer, I can get this driver, and put it into a matching cabinet that I made myself easy enough, but matching it with a tweeter and knowing what kind of crossover to make, is something I am lacking experience in. My last design was a hack job. I bought some woofer/mid's on special, then bought some tweeters independantly, both Vifa, from Jaycar, with no decision as to why I chose the two... then worked really hard to make them sound good together, and eventually they did, after some zobel networks and attenuation networks, padding, tuning, lots of glue and screws, and ears.
My main question here would be "What should I look for when looking at Data Sheets with tweeter drivers, so that I can make a decent decision?."
And for another question. "I'm studying Visual Design at Uni right now... I want to learn more about audio, ... what audio does in the air, the mechanics of speakers creating the audio, etc, what subject would cover all this stuff?"
I am trying to come up with a good combination of mid/woofer and tweeter combo for a good accurate all round setup. I use Sennheiser HD280 Pro's, and AKG K-300's for headphones, but since my speakers have died, I have been forced into some $15 desktop PC Speakers...
So far I have been looking at the Vifa P17WJ-00-08 for the mid/woofer's just to start things off with an all round decent performer, I can get this driver, and put it into a matching cabinet that I made myself easy enough, but matching it with a tweeter and knowing what kind of crossover to make, is something I am lacking experience in. My last design was a hack job. I bought some woofer/mid's on special, then bought some tweeters independantly, both Vifa, from Jaycar, with no decision as to why I chose the two... then worked really hard to make them sound good together, and eventually they did, after some zobel networks and attenuation networks, padding, tuning, lots of glue and screws, and ears.
My main question here would be "What should I look for when looking at Data Sheets with tweeter drivers, so that I can make a decent decision?."
And for another question. "I'm studying Visual Design at Uni right now... I want to learn more about audio, ... what audio does in the air, the mechanics of speakers creating the audio, etc, what subject would cover all this stuff?"
I have the rest figured out so the tweeters can wait till later I guess. I was using BassBox software to work out most of it, but the last time I used that, I was told by someone who makes speakers all the time that all the calculations were wrong, and BassBox got it wrong. Any other programs or websites or anything I should look at instead?
Hi!
I tried many different 6,5" drivers the past few years and I have to tell you that the good old Vifa P17WJ-00-08 is one of the best allround performers of all of them! Great choice!
To combine a 8 ohm woofer with a 6 ohm tweeter is no problem at all. Most of the older vifa tweeters are 6 ohms and nearly all of the seas units are 6 ohms. When you adjust the volume level of the tweeter to match the level of the woofer you can use a L-pad attenuator. With carefully chosen values you can get the attenuation level you want PLUS a conversion of the total impedance (tweeter AND L-pad) to 8 ohms. Or, let's assume a simple 2,2 ohm resistor in series with the tweeter gives the volume level you want, you automatically have a 8 ohm tweeter then!
Don't even think about the Dayton tweeter used in one of the projects linked above. I bought it, and after a few times of assembling and disassembling it has nearly fallen apart in my hands. Really cheap build quality.
My suggestion is to use either one of the newer morel tweeters or a decent one of the seas program. Thanks to the new faceplates of the morels (104mm diameter, same like seas and vifa) you can even switch them later.
I would suggest:
Morel CAT 308 - http://www.morelhifi.com/products/pdf/Tweeters/CAT/Specs sheet CAT308.pdf
or
Seas 27TDFC (H1189) - THE ART OF SOUND PERFECTION BY SEAS - H1189-06 27TDFC
Both very decent drivers, only the morel is more expensive than the seas, but perhaps not necessarily better sounding.
Regarding the crossover, for starters I would suggest a simple 1st order x-over on both woofer and tweeter, with a zobel network for both. If you are interested I can calculate some values to start with, just let me know. Since I build a lot of speakers using seas tweeters and some using the vifa woofer, I know how these drivers sound with different kinds of crossovers.
But: Keep in mind, it's also a matter of personal taste, and I am a huge fan of very simple crossovers, as these nearly always sound much better to me. Both woofer and tweeters have such smooth frequency responses that a simple crossover should be the way to go!
For the enclosure you can go for a quite small one (about 15 litres minimum) up to around 25 litres, both vented. In the middle of that (around 20 to 21 litres) lies the calculated optimum for the woofers TSP's. With a smaller enclosure you will get a more tight and fast bass response, with a larger one you will get a deeper and more wighty bass response. I found the allround optimum being at 18-22 litres.
Nice project!
Regards!
Martin
I tried many different 6,5" drivers the past few years and I have to tell you that the good old Vifa P17WJ-00-08 is one of the best allround performers of all of them! Great choice!
To combine a 8 ohm woofer with a 6 ohm tweeter is no problem at all. Most of the older vifa tweeters are 6 ohms and nearly all of the seas units are 6 ohms. When you adjust the volume level of the tweeter to match the level of the woofer you can use a L-pad attenuator. With carefully chosen values you can get the attenuation level you want PLUS a conversion of the total impedance (tweeter AND L-pad) to 8 ohms. Or, let's assume a simple 2,2 ohm resistor in series with the tweeter gives the volume level you want, you automatically have a 8 ohm tweeter then!
Don't even think about the Dayton tweeter used in one of the projects linked above. I bought it, and after a few times of assembling and disassembling it has nearly fallen apart in my hands. Really cheap build quality.
My suggestion is to use either one of the newer morel tweeters or a decent one of the seas program. Thanks to the new faceplates of the morels (104mm diameter, same like seas and vifa) you can even switch them later.
I would suggest:
Morel CAT 308 - http://www.morelhifi.com/products/pdf/Tweeters/CAT/Specs sheet CAT308.pdf
or
Seas 27TDFC (H1189) - THE ART OF SOUND PERFECTION BY SEAS - H1189-06 27TDFC
Both very decent drivers, only the morel is more expensive than the seas, but perhaps not necessarily better sounding.
Regarding the crossover, for starters I would suggest a simple 1st order x-over on both woofer and tweeter, with a zobel network for both. If you are interested I can calculate some values to start with, just let me know. Since I build a lot of speakers using seas tweeters and some using the vifa woofer, I know how these drivers sound with different kinds of crossovers.
But: Keep in mind, it's also a matter of personal taste, and I am a huge fan of very simple crossovers, as these nearly always sound much better to me. Both woofer and tweeters have such smooth frequency responses that a simple crossover should be the way to go!
For the enclosure you can go for a quite small one (about 15 litres minimum) up to around 25 litres, both vented. In the middle of that (around 20 to 21 litres) lies the calculated optimum for the woofers TSP's. With a smaller enclosure you will get a more tight and fast bass response, with a larger one you will get a deeper and more wighty bass response. I found the allround optimum being at 18-22 litres.
Nice project!
Regards!
Martin
Basic rule of thumbs is to keep the XO as low as possible and to cross to the tweeter 2 octaves or more above the tweeters resonance.
Beginners advice, get the tweeter and midrange as physically close together as you can, measure the distance between centers and use that distance as your wavelength for the XO frequency
Yeah, bass box calculated a 15 litre box for me, F3 @ 54hz, with a round vent about 148 x 60mm. So far it sounds all good to me. It will be a shelf standing nearfield monitor, level with my ears. I had a sub for when I'm stuffing around with games and movies, that I also made myself ages ago, but it blew. I have the amp still, will make that as a future project. There are some Seas 27TFF's available on eBay right now that I was considering... SEAS Luxurious Dome Tweeter Shielded used with Richter - eBay, Speakers, Subwoofers, Audio, Electronics. (end time 13-Mar-10 14:06:51 AEDST)
With a volume of 15 litres there is no need to put more damping material into the boxes. But I would go for a tuning frequency of around 50Hz, so you would need a round vent with 60mm x 180mm to avoid overblown bass response.
I would be careful with these Seas drivers from ebay. The 27TDFC (H1189) I recommended has a coupled additional volume chamber which gives the unit a far lower resonance frequency, which is absolutely desired when it comes to simple 1st order crossovers. Further more, the frequency response of the H1189 is better suited, since it goes down some db's under 2kHz by itself, which supports the effect of the crossover and matches better to the response of the Vifa woofer. In the opposite, the H0831 has its highest level of sound pressure in the range of 1,7kHz, which is very difficult to handle with a simple x-over. And last but not least, the impedance peak at the resonance frequency is by far lower with the H1189 than with the H0831. It's about 9 ohms at 550Hz with the H1189 while it's about 15 ohms at 1000Hz with the H0831. That means with the H0831 you have to take care about this peak, either with a more complex crossover (2nd or even 3rd order) or, even more complicated, you have to calculate AND measure a proper LCR-filter (parallel notch filter) to compensate this peak. With the H1189 the peak is so low in both, frequency and impedance, that there is no need to worry about.
Theoretically the distance between a mid-woofer and a tweeter should be one wavelength at the XO frequency
Wavelength is 34000 / f ( in Centimeters )
So if C2C distance is 17cm then the XO should be set at around 2000Hz
In practice I almost always break this ROT and cross higher to keep component cost down but I do try and keep the C2C as close as possible
So if XO is set at 2k and we need 2 octaves above Fs on the tweeter you can see that the tweeter resonant frequency needs to be 500Hz or lower; especially when using first order cross-overs.
Tweeters with very low Fs tend to be more expensive, all other things being equal
Are you sure of this?
If it is correct, then commercial manufacturers seem to disagree.
I measured my B&W and KEF cabinets (both 3-way) and the distance between mid and tweet centers is about 1/3 longer than your equation gives for their respective crossovers.
In fact, in both cases if crossed as they are from the factory, it would be physically impossible to get the drivers close enough to agree with the formula, given the driver flange sizes.
Take the B&W drivers (mid 105mm flange, tweet 90mm), crossed at the factory 4500Hz, should be 75mm C2C. Won't happen. Flanges touching gives near enough to 10cm, which is what the factory used. I don't have the parameters for the drivers, but I'm sure that B&W chose 4500Hz with due regard to Fs.
KEF B110/T27 at 3000Hz: Flanges 130mm/108mm, still won't happen (just!).
Perhaps the rules have changed in the last 30 years since these drivers were made, or maybe there is another factor involved.
Gary
Ideal situations don't often exist in practice, but if you use a small faceplate NEO tweeter and a mid-range of 5inch or smaller then it becomes easier.
One of my favourite builds uses a 4k XO in an MTM using 8 inch midranges so I broke a rule, but if I was making my ultimate system this would be one of my design starting points.
One of my favourite builds uses a 4k XO in an MTM using 8 inch midranges so I broke a rule, but if I was making my ultimate system this would be one of my design starting points.
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