It is correct, the crossover frequency is nearly 4.5Khz.
You can
1. Suppress the 2.2uF
2. Reverse the tweeter and increase 3.9uF to 10uF
It will down the crossover frequency near 3k. And i think it will be better.
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🙂
Let me think about that for a while. Perhaps I can manage to fabricate a small wooden ring to mount this baby.
Jerome,
thanks for your suggestion! Sounds appealing to me, I will try that, first thing in the morning. It's slightly past midnight here in Germany and I don't want to bother my next door neighbours...
There's more to a genuine full range driver than a light and stiff cone. Damping of cone breakup modes is critical, and in this area carbon fibre is not as good as paper IMHO.
Otherwise known as colouration 😉 If the speaker has it's own signature sound then it's not neutral and balanced. If you like its particular sound that's your prerogative, but that doesn't make it a good speaker.
I find that hard to believe. Unless you're using the driver on an infinite baffle then you do have to worry about baffle step correction. As other have mentioned, the big rise in response starting around 800Hz is consistent with baffle step of a narrow cabinet, although there may be driver response aberrations there as well, such as a surround resonance.
Although it's still useful information to know the response of a driver on an infinite baffle (it's "true" response before baffle diffraction effects alter the response) it really doesn't matter as far as designing and optimizing a crossover goes - you measure the driver response you get on the proposed baffle and design the network around that response, not the infinite baffle response.
Baffle step correction is not always explicit (for example an R-L shelf filter on the woofer) sometimes it is implicit in the design - for example an L-Pad on the tweeter, or a deliberate "mismatch" in the driver sensitivities.
There's no skirting around baffle step correction on a free standing speaker I'm afraid.
You're almost certainly putting a hole in the upper mid/lower treble region by doing that, so naturally it sounds dull and closed. The ear is particularly sensitive to peaks or dips in the "presence region" between 2-4Khz, and a significant dip in this region will sound dull and lacking in imaging/focus.
Without measuring what's happening to the response, you are stabbing in the dark making such changes though.
Again, without measurements we can only speculate, but I would suggest that the "greyed out" characteristic you describe is probably too much output in the 3-4Khz region. The graph in post 6 shows a spike at 4Khz, which can often have this effect if left uncorrected.
The reversed driver polarity is generally the correct polarity with that type of filter (depending on the acoustic slopes of the drivers natural roll-offs and physical offset of their acoustic centres) so when you don't reverse the phase you get a big hole in the frequency response. The fact that you do get a big hole in the response with the two connected in phase means that the out of phase correction is the correct one, and that the acoustic phasing of the drivers is roughly right in the crossover region.
Getting just the right balance in the presence region is a challenge as the ear is very fussy there, so doing it without measurements would be extremely difficult if not impossible.
I see you have ARTA, can you not just pick up a cheap measurement microphone like the Behringer ECM8000 ? They're not the best measurement mic in the world but for $40 or so plus a pre-amp you'd still be one heck of a lot better off than doing it by guesswork. (Most ECM8000's are pretty flat from about 40Hz to 8Khz without any correction, with a bit of a rise in the treble, so are good enough for most crossover work)
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Simon,
you made a nice summary of what we have discussed so far. I have to investigate some of your points, especially the idea that it could be too much output in the 3-4kHz region what might cause this odd effect. And I hear what you're saying: A small and cheap measuring system would perhaps be a good idea. I always thoght I would have to spend serveral hundred bucks to get a set for starters. Say, would a cheap preamp like the Behringer MIC100 or MIC200 be suitable for this purpose?
Behringer Mic100 Tube Ultragain Mic-Preamp
Behringer MIC200 Tube Ultragain Mikrofon-Preamp
And what else would I need? The mic, the pre, and then through my computer soundcard into the ARTA software, is that correct? But I only have the ARTA freeware. Would I need the pro version?
Thanks!
you made a nice summary of what we have discussed so far. I have to investigate some of your points, especially the idea that it could be too much output in the 3-4kHz region what might cause this odd effect. And I hear what you're saying: A small and cheap measuring system would perhaps be a good idea. I always thoght I would have to spend serveral hundred bucks to get a set for starters. Say, would a cheap preamp like the Behringer MIC100 or MIC200 be suitable for this purpose?
Behringer Mic100 Tube Ultragain Mic-Preamp
Behringer MIC200 Tube Ultragain Mikrofon-Preamp
And what else would I need? The mic, the pre, and then through my computer soundcard into the ARTA software, is that correct? But I only have the ARTA freeware. Would I need the pro version?
Thanks!
luckily flush mounting is a little less critical, using a horn. besides thick felt is useful on baffles 2
I don't know much about Jerome's model , but IMO crossing even lower using a 3rd order HPF would be something better to try. Most of the best custom electrical Xover designs are asymmetrical.
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The ECM8000 is a reasonable entry level mic, the next step up in measurement accuracy are mics costing hundreds of dollars, there doesn't really seem to be anything in between, so unless you want to pay upwards of about $300US then it's your only real choice. While obviously not as good as those $300+ mic's, it's a lot better than trying to use a microphone designed for recording music, or other random microphone, which don't even make any pretence to being flat. (Hand held vocal mics roll off below 100Hz for example)
Even expensive measurement microphones are somewhat non-flat - a large part of what you pay for with an expensive measurement microphone is an individual calibration profile (.mic file you install in your measurement software) which calibrates your specific microphone against some reference standard. In theory even an ECM8000 can be calibrated against a reference, so whilst Behringer don't do this I believe there are some 3rd parties doing this. (Probably for more than the cost of the microphone though!)
I would avoid a tube pre-amp mainly for the reason that you don't want any drift in gain levels with temperature as the unit warms up affecting the consistency of your measurements.
If you've got a good quality sound card any decent solid state XLR to unbalanced pre-amp with phantom power should do. (Assuming it's response is flat)
Another option might be a USB audio interface that includes a built in balanced XLR mic input with phantom power.
I actually don't use either - I have a fully passive "pre-amp" which I built which is just a high quality balanced to unbalanced microphone step-up audio transformer, with two 9v batteries providing 18v phantom power via a resistor and the primary centre tap. Works very well and measures very flat, but it does rely on the transformer being good quality. I then plug that into the line level input on my sound card.
As for ARTA - I switched to ARTA about 6 months ago. I'm very impressed with it and highly recommend it. The demo version is very usable - you can make just about any measurements that the full version can (with the exception of polar plots) you just can't permanently save any measurements - once you exit the program they're gone. (Although you could take screen shots)
I made do with the free version for many months, but finally decided to buy it so I could archive my measurements and recall them later, and also to use polar plot mode.
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Here it is second order acoustic slope, asymmetrical 6/12dB. Easy and works well without measurement.
High order crossover, lower point could be better but need actual measurements and a lot of experience.
Note i follow Vifa recommendations LR2@3500Hz. The tweeter could not be enough good to go lower.
Don't forget that after performing an impulse response test you can then export a txt file that contains the frequency and phase response of the measured driver/system and this is what you'll want to import into the majority of loudspeaker CAD programs.
but the problem is really needs to be lower, b/c I couldn't recomend crossing > 2,5 KHz even for a smaller 6.5" given full dispersion flat flange dome design. I've only used that Vifa once, so can't comment on power handling lower than that. But on the other hand the Morels in my experience , are very forgiving even when abused. I aim for 4th order LPF using 2 poles and 3rd order HPF using zobels to adjust phase at the central point.
Yes but it is not necessary, you have exceptions.
Dispersion is not the only criteria, it is a compromise. Slopes are not steep.
What will say about an Audax PR17 or a Beyma 15Mi100 ...
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