Ah, NOW we're cooking with gas, Danny! 
That's your typical 6" driver with a peak around 4.5 to 5kHz! We can do this. It's a bit like the Reed cone SEAS ER18RNX.
Simple bafflestep and a notch in Dynaudio style. I've pretty much nicked Troels' XT25 circuit:
Peerless HDS PPB 830860
That 3.3R input resistor is your tweeter level adjust, and it can be anything you like and impedance stays good. I'd start with closed box and fit a reflex tube later if you want. But it all works rather well. I have, of course, made some allowance for the flattish FR and lower efficiency of the XT19 in the Boxsim modelling. It has to be third order tweeter because of the non-ferrofluid nature of the XT19.
It's a 3kHz crossover and coil resistance is not critical, but you'd use aircoil on the tweeter and notch for sure. Ferrite core or good aircore on bafflestep. 250V polypropylene caps and 5-10W wirewound resistors.
That's your typical 6" driver with a peak around 4.5 to 5kHz! We can do this. It's a bit like the Reed cone SEAS ER18RNX.
Simple bafflestep and a notch in Dynaudio style. I've pretty much nicked Troels' XT25 circuit:
Peerless HDS PPB 830860
That 3.3R input resistor is your tweeter level adjust, and it can be anything you like and impedance stays good. I'd start with closed box and fit a reflex tube later if you want. But it all works rather well. I have, of course, made some allowance for the flattish FR and lower efficiency of the XT19 in the Boxsim modelling. It has to be third order tweeter because of the non-ferrofluid nature of the XT19.
It's a 3kHz crossover and coil resistance is not critical, but you'd use aircoil on the tweeter and notch for sure. Ferrite core or good aircore on bafflestep. 250V polypropylene caps and 5-10W wirewound resistors.
Attachments
Last edited:
I'd start with an open back kind of box. And rather stuffed ( acrylic or cotton or wool ) ....
It should have also some kind of 'sculptured baffle', or also trapezoidal ( but 90° rotated )
Last edited:
I don't usually respond to such childish behaviour, once again show me a source which says you can. @Sean the reason is that the sensitivities won't be the same and the overall impedance of the crossover could be too low and may blow your output trannies.
You can't be serious???!!!
A tweeter is almost always more sensitive than any other drivers in the system and has to be attenuated to match them, and even more so in order to have the proper BSC. So, if you have a 4-ohm tweeter matched up with an 8-ohm midwoofer in a 2-way for instance, you could very well end up with a 4-ohm resistor in series with the tweeter and "voila", you now have a nominally 8-ohm load on the tweeter's crossover. But even if the impedances don't end up as perfect matches, it doesn't matter one iota because you will have designed the crossover properly. Oh, maybe YOU won't have done that but EVERYONE else will have. Also, very few speaker systems have an overall impedance so low as to blow an amplifier. If that does happen, either the amplifier's design is suspect or the speaker design was deficient. I can't believe you're so naive or so lacking in knowledge. Shaun, I hope you're completely ignoring everything balerit has said.
Paul
A tweeter is almost always more sensitive than any other drivers in the system and has to be attenuated to match them, and even more so in order to have the proper BSC. So, if you have a 4-ohm tweeter matched up with an 8-ohm midwoofer in a 2-way for instance, you could very well end up with a 4-ohm resistor in series with the tweeter and "voila", you now have a nominally 8-ohm load on the tweeter's crossover. But even if the impedances don't end up as perfect matches, it doesn't matter one iota because you will have designed the crossover properly. Oh, maybe YOU won't have done that but EVERYONE else will have. Also, very few speaker systems have an overall impedance so low as to blow an amplifier. If that does happen, either the amplifier's design is suspect or the speaker design was deficient. I can't believe you're so naive or so lacking in knowledge. Shaun, I hope you're completely ignoring everything balerit has said.
Paul
JBL XPL200A
These use a 4 ohm middome, the rest of the drivers are 8 ohm
Look at the .pdf and check out the replacement cones and diaphragms + complete Xover wiring diagram
Tweeter D8R046Ti
Midrange D4R093Ti
Low/mid C8R115H-1
Woofer C8R2214
Bold number=Z
8ohm tweeters are also VERY commonly used with 4ohm woofers in automotive component kits
I really do wonder why we are having a flame war about matching impedances of drivers. Really transistor amps couldn't give a hoot. But I always go for the easy high impedance as it goes.
Let's talk sloped baffles and time alignment. Here's what it looks like:
And below a suitable crossover I hope. Based on some guesswork born of experience, but should be sweet. Frankly, I'm a bit like Beethoven, I just need to read the score to hear the whole thing in my head. You can't teach that in school.
Let's talk sloped baffles and time alignment. Here's what it looks like:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
And below a suitable crossover I hope. Based on some guesswork born of experience, but should be sweet. Frankly, I'm a bit like Beethoven, I just need to read the score to hear the whole thing in my head. You can't teach that in school.
Attachments
Hi,
You don't know the subject your pontificating about.
A 4 ohm tweeter of the same sensitivity as an 8 ohm bassmid
can easily be used with it, for reasons you can't work out.
rgds, sreten.
Last edited:
Guess i wasent all that far off the green after all then, the above mentioned XPL200A`s sports stepped baffles, placing the tweets and mids about 1" behind the low mid and the woofer.
Last edited:
To System 7:
I believe your "flaming" comment referred to me, and some others, and want to address it. I agree completely that we should not flame others, but that usually occurs only on issues/subjects/statements that cannot be proved or disproved because the comments being proffered are usually based on personal preferences and perceptions, like why one capacitor "sounds" better than another, or needing to use cable risers to have good sound, or... I assume my drift is clear. But when someone makes a blatantly incorrect statement, like "you can't mix 4-ohm and 8-ohm drivers", that statement needs to be disputed and that person needs to be challenged. There already is so much confusion possible in this hobby when dealing with proven facts, that it's really disheartening and disappointing that someone will make totally false comments that may be believed and followed by those new to and less-experienced in this hobby and our little community.
Paul
I believe your "flaming" comment referred to me, and some others, and want to address it. I agree completely that we should not flame others, but that usually occurs only on issues/subjects/statements that cannot be proved or disproved because the comments being proffered are usually based on personal preferences and perceptions, like why one capacitor "sounds" better than another, or needing to use cable risers to have good sound, or... I assume my drift is clear. But when someone makes a blatantly incorrect statement, like "you can't mix 4-ohm and 8-ohm drivers", that statement needs to be disputed and that person needs to be challenged. There already is so much confusion possible in this hobby when dealing with proven facts, that it's really disheartening and disappointing that someone will make totally false comments that may be believed and followed by those new to and less-experienced in this hobby and our little community.
Paul
I see where you're coming from. However, I believe you are using old school rule-of thumb, which is somewhat outmoded by the level of knowledge currently at the disposal of the average DIYer.
It is generally not a good idea to use a tweeter that has the same sensitivity as the woofer, as it leaves no room for adjustment. Nevertheless, tweeters do tend to be more sensitive than their matching woofers, anyway. One of the functions of the crossover is to set the relative levels of the respective drivers in a system.
As for using unequal impedances between the woofer (8 ohm) and tweeter (4 ohm), it should not be a problem if the amplifier can handle the lower impedance (4 ohm). A loudspeaker's impedance curve is complex: it is not constant over the audio spectrum (and therefore calling a speaker "4 ohm" or "8 ohm" is more of nominal handle than a true indication of the load it presents). In a parallel topology crossover, the tweeter circuit and woofer circuit are only effectively in parallel over the crossover region. And even in that region, impedances are rising as you move from one band towards the other. So, an amplifier may see "8 ohms" in the woofer's band and "4 ohms" in the tweeter's band, but it should not unsettle the amp. There are, of course, amplifiers (typically of the valve type) that have relatively high output impedances (or low damping factors), where the varying load can affect frequency response to some extent, but these are rare these days.
One more thing: modern loudspeaker design software allows one to specify a target impedance range. Occasionally, the crossover optimisation algorithm can't reach a solution, and the criteria have to be relaxed, but the utility exists, nonetheless.
To sum up, although mixing driver impedances in the same loudspeaker system is not commonly done, it is also not unusual and is completely manageable. If the minimum final system impedance is not too low (like below 4 ohms), a common modern amplifier should have no problem driving it.
Apologies for drifting off topic a bit.
Hi,
Not true at all, there is plenty of adjustment, due to BSC.
And you can use the adjustment to raise treble impedance.
rgds, sreten.
Back on topic...
Here's the modelling that lead to the flat baffle crossover, Danny. Pretty typical 3rd order tweeter phase, it always goes a bit wrong below 2kHz, just how it works. I'm expecting the Vifa XT19 to be a lot quieter at the top than the mylar DT94 so it should all work.
Nice impedance IMO, about the best I've got with 3rd order. These 3 ohm DC Vifa tweeters always need 3.3 or 4.7R series resistance to get well-behaved.
Here's the modelling that lead to the flat baffle crossover, Danny. Pretty typical 3rd order tweeter phase, it always goes a bit wrong below 2kHz, just how it works. I'm expecting the Vifa XT19 to be a lot quieter at the top than the mylar DT94 so it should all work.
Nice impedance IMO, about the best I've got with 3rd order. These 3 ohm DC Vifa tweeters always need 3.3 or 4.7R series resistance to get well-behaved.
Attachments
Unfortunately the appropriate resistor to match the tweeter level with the Focal woofer is only 2 ohm or less.
I would have to concede that most of the time baffle step correction would save the day. However, I have had two cases, specifically with centre loudspeakers which were mounted in the AV stand (read bookshelf speakers), where baffle step correction was not required. In both cases I had to redesign the crossover (having designed for free-standing position) such that no baffle step equalisation was applied. As it happens, the tweeters were a dB or two more sensitive than the woofer in one case (MT), and exactly the same in the other (MTM).
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.