now that i start to reverse engineer the passive lcr x over, it is only first order between 15 an 8 inch.
First order does not have good phase - hi and lo have 90 degree shift. I could improve that by introducing 2nd order passive filter, also the steepness would be improved. I would expect the 8inch to profit from more damping against the low frequencies below its enclosures tuning. at least displacement wise. i have good LCR calculation and simulation skills, but I lack an acoustic measurement system to verify the changes. What is your opinion? Leave as is or try to improve to 2nd order?
First order does not have good phase - hi and lo have 90 degree shift. I could improve that by introducing 2nd order passive filter, also the steepness would be improved. I would expect the 8inch to profit from more damping against the low frequencies below its enclosures tuning. at least displacement wise. i have good LCR calculation and simulation skills, but I lack an acoustic measurement system to verify the changes. What is your opinion? Leave as is or try to improve to 2nd order?
You have all the tools you need to do an experiment, using the DCX and your amplifiers you could actively biamp or even triamp these things and play with different crossover slopes and frequencies. And as for a measurement system you just need a calibrated mic like the Behringer ECM or the Parts Express EMM, a computer of some type, a USB interface, and some free software like Room EQ Wizard. If you have a computer already the other parts won't cost more than $200.
Warning. If you make the mistake of actively bi/tri amping these things and give it a listen with 24db filters you will never be satisfied with a passive crossover again.
Last edited:
Yep the $200 is not the issue. Nowadays time is money and if I get into such an technical optimizing project, no matter what it is, it always takes longer and other things suffer. Besides that, I don't have the amp channels to do active biamping,
Only 2 amps, 4 channels (2 for subs and 2 for the RCFs). Buying more amp channels is 4 figure $ plus the need to get a bigger rack as well. And then organize to transport the rack etc.... I am not going for that kind of time killer. My trouble is simply: Although I am an audio tinkerer, an will most likely be the rest of my life, I need to get at least decent system up and running to play music to just sit down and relax. When my friends come over I want to play.
Otherwise they say: Years going by and your systems remain still construction sites. lol..
If I have that system running maybe 95% perfect, I can after that spend $$$ and years of my life to a new better system . But that is far into the future.
Only 2 amps, 4 channels (2 for subs and 2 for the RCFs). Buying more amp channels is 4 figure $ plus the need to get a bigger rack as well. And then organize to transport the rack etc.... I am not going for that kind of time killer. My trouble is simply: Although I am an audio tinkerer, an will most likely be the rest of my life, I need to get at least decent system up and running to play music to just sit down and relax. When my friends come over I want to play.
Otherwise they say: Years going by and your systems remain still construction sites. lol..
If I have that system running maybe 95% perfect, I can after that spend $$$ and years of my life to a new better system . But that is far into the future.
Well you do have enough amp channels to bi-amp or tr-amp 1 speaker and that is all you need to test if changes to the passive crossovers would have a positive impact on SQ. Sound quality is a very personal thing so nobody can tell you what will work for you, and when it comes to passive crossovers less is often more, both the drivers and passive components combine to produce the final acoustic response so it can be a mistake to assume a different crossover slope is automatically better. But that said for a high power/high SPL application I have a hard time believing a first order high pass is sufficient to prevent excessive excursion of that midrange driver, and same goes for the CD.. does it have a 1st order crossover too? I certainly hope not because a CD that is allowed to operate too low will certainly produce some gawdawful screaching noises.
I just looked up the pdf for this speaker system and it states crossovers of 300hz and 3.5khz with slopes of 6db, 6db and12db/oct. This is totally inadequate for these drivers IMO, I bet you can visually see the midrange driver move with the beat at higher drive levels? If so that is very bad and my suggestion would be to completely rebuild the crossovers for 500hz and 5khz at 12db/oct for low and mid and 18db for the CD.
thanks for your input. couldnt see the mid moving the beat because of the metal front cover. 12 12 18 db 500 5k would be quite easy for me to realize if the loads were purely ohmic what they are not. also they have some lcr in parallel and r in series to the mid 8 inch. tweeter has also a voltage divider plus 24 volt light bulb. i ll post the schematic once i have measured the air coils. guessing the inductance doesn't work. too bad they are not marked. you think 500 hz is better but then why they chose 300 what only increases the components and thus the cost? assume the manufactorers always try to get away with higher than optimum xover frequencies as long there is cost for the coils involved. or was the capitalism not like today when they did this speaker. what today most manufacturers not see is that by use of the midrange driver, the CD corner freq. can be set higher so it will operate less screeching. 12db is not much but at least it is not operating down to 2khz like on todays 2way designs.
Last edited by a moderator:
That sounds like pretty standard crossover config actually, possibly a zobel on the mid to flatten impedance and the CD is going to be 6-9db more sensitive than the other drivers so it will need to be padded down that much with an L-pad.
The 5khz crossover moves it outside the bulk of the critical vocal range where crossover artifacts are more obvious, the only caveat is that hopefully the mid driver will behave up that high, this along with the steeper CD crossover will also clean up output from the CD and hopefully stop it from making nasty noises. That light bulb you can completely remove with the the new crossover, it is intended to be a protection device but it adds compression at high drive levels which will be painfully obvious in a critical listening environment.
The 5khz crossover moves it outside the bulk of the critical vocal range where crossover artifacts are more obvious, the only caveat is that hopefully the mid driver will behave up that high, this along with the steeper CD crossover will also clean up output from the CD and hopefully stop it from making nasty noises. That light bulb you can completely remove with the the new crossover, it is intended to be a protection device but it adds compression at high drive levels which will be painfully obvious in a critical listening environment.
i see why go 5000hz but why the 500hz? the light bulb is indeed good to have since the light is visible through the ports and it tells me the box wants no more juice plus it protected the tweeter from too high signals several times, also from too high 5000 10000 15000hz levels. it can fail due to voice coil melting too that is where the light bulb comes in.
honestly why did they choose 300 hz if 500 is cheaper to realize. just look at that big iron core coil.
i think i can easily improve the tweeter filter to 18 db since the phase tweeter midrange cannot be optimized it changes by each cm of listening distance. but the phase woofer midrange could be good to have matched. that is exactly where it is getting difficult.
one other idea is to use a 4 ohms woofer instead but leave the other components 8 ohms. then adjust the crossover impedance then take out 3db activly exactly where the woofer operates at the dcx input. this way i could get 3 db more damping for the midrange even if the filter order stays as is.
honestly why did they choose 300 hz if 500 is cheaper to realize. just look at that big iron core coil.
i think i can easily improve the tweeter filter to 18 db since the phase tweeter midrange cannot be optimized it changes by each cm of listening distance. but the phase woofer midrange could be good to have matched. that is exactly where it is getting difficult.
one other idea is to use a 4 ohms woofer instead but leave the other components 8 ohms. then adjust the crossover impedance then take out 3db activly exactly where the woofer operates at the dcx input. this way i could get 3 db more damping for the midrange even if the filter order stays as is.
My thought on the 500hz crossover was to take a bit more load off the mid, I had a 3-way PA speaker with an 8" cone mid at one time and it would happily run down to 100hz at low drive levels but not with any real power into the system. My coments on the light bulb are also from 1st hand experience, if you raise the crossover and step up to 18db/oct the bulb won't be necessary.
the chokes is all air chokes with the small resistors that have no refdes being the 25 degree chokes rdc.
only the l5 is gapped iron core and shows almost no signs of saturation below about 18 a.
the glow lamp impedance is calculated estimated from tungsten resistor going to 75 W at 3000K. need to verify this.
midrange is rcf l8l750 4 ohm very strange. no more available.
15 inch is available, tweeter also is an issue.
considerations:
i d like more punch from the low side, but at the same time want good or better lf rejection for The midrange. so cannot just push the 100 200 hz by the dcx input without affecting the midrange tweeter excursion too. maybe a 4 ohm 15 inch woofer would do i e give 3 db more output at this range keeping the power for the other components the same.
i think the way the xover works now is only 1st order lowpass at 300 hz, but letting the 15 inch start to beam 300 400 500 600 hz so make up for the loss this way at least on axis and blend somehow with the mid at around 500 - 600. that is my current theory how they fit these strange values into the filter. also, why is there a rlc for the midrange sucking at above 5000hz? additionally i want to go from 1st to sec order but issue is the phase at the xover between 15 inch and 8 inch. no any idea how to optimize without measurement resources. next is to get rid of at least part of that heat burning resistor power esp for the midrange this is pure awesome waste.
any ideas would help.... thanks
only the l5 is gapped iron core and shows almost no signs of saturation below about 18 a.
the glow lamp impedance is calculated estimated from tungsten resistor going to 75 W at 3000K. need to verify this.
midrange is rcf l8l750 4 ohm very strange. no more available.
15 inch is available, tweeter also is an issue.
considerations:
i d like more punch from the low side, but at the same time want good or better lf rejection for The midrange. so cannot just push the 100 200 hz by the dcx input without affecting the midrange tweeter excursion too. maybe a 4 ohm 15 inch woofer would do i e give 3 db more output at this range keeping the power for the other components the same.
i think the way the xover works now is only 1st order lowpass at 300 hz, but letting the 15 inch start to beam 300 400 500 600 hz so make up for the loss this way at least on axis and blend somehow with the mid at around 500 - 600. that is my current theory how they fit these strange values into the filter. also, why is there a rlc for the midrange sucking at above 5000hz? additionally i want to go from 1st to sec order but issue is the phase at the xover between 15 inch and 8 inch. no any idea how to optimize without measurement resources. next is to get rid of at least part of that heat burning resistor power esp for the midrange this is pure awesome waste.
any ideas would help.... thanks
For the use you are intending I would suggest you invest in a decent lms, something like XTA would be best for pro use although the pulse budget range that require a laptop to be plugged in most of the time is a half decent option.
I use the XTA dp226 with turbosound TQ445s, along with a variety of bins depending on venue and gig type. The xta is used as the master volume control when I am not with the rig as it can be set and left (front locking panel is used).
I use the XTA dp226 with turbosound TQ445s, along with a variety of bins depending on venue and gig type. The xta is used as the master volume control when I am not with the rig as it can be set and left (front locking panel is used).
So after reverse engineering the circuit plus working on optimization here is my current state, schematics plus sims.
The triangle amplifiers is just to simulate the phase inversion (minus) plus the difference in acoustical efficiency (double for the mid and tweeter)
Improvements: Midrange now has much better attenuation at below 250Hz.
Tweeter now has much better attenuation at below 2.5kHz.
...the added coil is air coil 4 Ohms 7 - 8 mH, about 340 turns on a beer bottle. AWG 22.
The only thing open is the phase 15" <-> 8 inch at the crossover. I want more out of the 15 inch at 150~200Hz, the 88uF will do this, but the phase is so much changed at the crossover to the mid. so not sure if this is good / better or worse? if not I can still skip the capacitor and boost 100 - 200Hz actively at the DSP signal stage, but then the midrange 8" would also be affected, effectively canceling the improved attenuation it got by the improved circuit. any ideas?
screenshots in next post.
The triangle amplifiers is just to simulate the phase inversion (minus) plus the difference in acoustical efficiency (double for the mid and tweeter)
Improvements: Midrange now has much better attenuation at below 250Hz.
Tweeter now has much better attenuation at below 2.5kHz.
...the added coil is air coil 4 Ohms 7 - 8 mH, about 340 turns on a beer bottle. AWG 22.
The only thing open is the phase 15" <-> 8 inch at the crossover. I want more out of the 15 inch at 150~200Hz, the 88uF will do this, but the phase is so much changed at the crossover to the mid. so not sure if this is good / better or worse? if not I can still skip the capacitor and boost 100 - 200Hz actively at the DSP signal stage, but then the midrange 8" would also be affected, effectively canceling the improved attenuation it got by the improved circuit. any ideas?
screenshots in next post.
So now I think of replacing that L15P530 by
18 sound 15W750
15W700
15ND830
Oberton 15NMB35
P Audio System P150-2226
Fane souvereign Pro 15-600LF
P Audio System 15BM-500B
Beyma SM-115N
Celestion TF-1530E
or even Beyma 15MI100 which has lower Xmax, but very high efficiency and can basically be used from 100 Hz up.
18 sound 15W750
15W700
15ND830
Oberton 15NMB35
P Audio System P150-2226
Fane souvereign Pro 15-600LF
P Audio System 15BM-500B
Beyma SM-115N
Celestion TF-1530E
or even Beyma 15MI100 which has lower Xmax, but very high efficiency and can basically be used from 100 Hz up.
Decision is done for 15MI100 to replace L15P530.
As I work on the xover simulation and so on... re-examined the idea of just buying new speakers.
Obviously there is not many affordable 15 inch 3 way passive speakers.
Could maybe also live with double 12s if they are 3 way passive and not bi - amped.
I understand that there is the "Prosumer" and the "concert grade" market, with the concert grade "high end" vendors charging about 3 times the money for a speaker that is most likely marginally better. This I do not get at all. Why is only the most expensive high end gear used for rocking a few 1000 drunken crazy headbangers if cost / profit is an issue at an event? I simply don't get it.
As I work on the xover simulation and so on... re-examined the idea of just buying new speakers.
Obviously there is not many affordable 15 inch 3 way passive speakers.
Could maybe also live with double 12s if they are 3 way passive and not bi - amped.
I understand that there is the "Prosumer" and the "concert grade" market, with the concert grade "high end" vendors charging about 3 times the money for a speaker that is most likely marginally better. This I do not get at all. Why is only the most expensive high end gear used for rocking a few 1000 drunken crazy headbangers if cost / profit is an issue at an event? I simply don't get it.
Have you looked at JTR?
They use a BMS coaxial compression driver so the horn is "two-way". At the link, that one pictured runs two 10 inch woofers.
JTR Speakers| Noesis 3TX
You can also get a dual 12" version, sealed or ported depending on what you want. They have such a good sound that JTR is hugely popular with the home theater crowd.
They use a BMS coaxial compression driver so the horn is "two-way". At the link, that one pictured runs two 10 inch woofers.
JTR Speakers| Noesis 3TX
You can also get a dual 12" version, sealed or ported depending on what you want. They have such a good sound that JTR is hugely popular with the home theater crowd.
Maybe Jeff at JTR can help you out. Oddly enough, he built those speakers using BMS coaxial compression horns that are made in Germany. The 10 inch woofers are Faital Pro made in Italy. (not sure on the 12's)
Who knows? Maybe Jeff can sell you the crossover network, tell you what 12 inch woofers work with the network and you can build one, or have one built. The dual 12" version is popular in home theaters and the sealed box construction of it would be quite simple to perform.
According to the BMS specs, that driver will go well over 140dB so no worries about output. The 12" dual woofer version of the Neosis is slightly more efficient, good for 101dB 1w/1m. The sealed dual 12" running in sealed box alignment starts to roll off at 70Hz, not an issue with subwoofers of course.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.