THE Crossover Thread

[George S.]

Did amp gain matching to the drivers today within the MiniDsp plugin to approximate a "Harman house curve" I downloaded into REW. Going to give this particular house curve a shot.
Boosted the 700 WOPL output by 10 dB for the subs.
Left the 400 WOPL output unchanged for the woofers.
Reduced the 400 WOPL output by 7 dB for the midrange.
Reduced the PL300S2 output by 5 dB for the tweeters.
Been testing different gain profiles all day. I'm surprised by how much small a gain structure change affects the sound.
Next up is generating the EQ filters and plugging them in to closely match the house curve, then time alignment of the drivers.

 

[laatsch55]

Yeah , I've noticed that too. Doesn't take much gain difference to make it sound not right...
The thing I didn't like about trip amping 10 years ago doesn't seem to bother me this time and that was getting things to sound right at a certain level and then cranking it and having to mess with.levels again.

 

[George S.]

I'm running 10 Hz to 20 KHz sweeps set to a 76 dB level at the microphone for the calibration. The signal is random white noise from the REW signal generator. I'm not noticing any need to change the amp gain settings again.
I did some further tuning last night and was able to drop the subs amp gain from +10 to +8, and stay within the room curve. They'll stay there unless I go to a different curve.
I'm using the so called "Harman" loudspeaker curve commonly used on REW, and Psychoacoustic smoothing of the sweep results.
Both approximate how we hear sound.

 

[grapplesaw]

Yeah , I've noticed that too. Doesn't take much gain difference to make it sound not right...
The thing I didn't like about trip amping 10 years ago doesn't seem to bother me this time and that was getting things to sound right at a certain level and then cranking it and having to mess with.levels again.

Well Lee with the PA2 you can control multiple memory points for different types and loudness Now the trick is to remember which is which

 

[laatsch55]

Well Lee with the PA2 you can control multiple memory points for different types and loudness Now the trick is to remember which is which

Yep..

 

[laatsch55]

I'm running 10 Hz to 20 KHz sweeps set to a 76 dB level at the microphone for the calibration. The signal is random white noise from the REW signal generator. I'm not noticing any need to change the amp gain settings again.
I did some further tuning last night and was able to drop the subs amp gain from +10 to +8, and stay within the room curve. They'll stay there unless I go to a different curve.
I'm using the so called "Harman" loudspeaker curve commonly used on REW, and Psychoacoustic smoothing of the sweep results.
Both approximate how we hear sound.

Are your ear and the eq adjustments always in agreement?

 

[George S.]

They're in agreement from appx 30 Hz to 10 KHz. After that I can't hear unless the volume is turned way up around 100 dB. I don't do that anymore.
I consider REW and the Umik-1 mike, highly accurate, as it has widespread use in the industry by the professionals. Same with the MiniDsp.
Moved crossover points today from 800 Hz to 1000 Hz, and 3500 Hz to 4000 Hz. These are the points JBL used on these boxes originally.
Also summed the subs for the first time. I'm thinking that is the correct move, but I need to do a sweep against the house curve and look at gain with them summed.
My prior tinkering with REW has helped, but it's complicated. There's no good all comprehensive guide on how to do this
Spent time today reading about time alignment and impulse testing and how to set individual driver delays. I'm going to try to start on that tomorrow.
Tried learning this stuff years ago, but work interfered. Now I have the time to do it.
Listening to the first Infected Mushroom Converting Vegetarians. Hope I don't piss off my neighbors. The bass never stops. Finally getting the 700 WOPL broke in.

 

[laatsch55]

They're in agreement from appx 30 Hz to 10 KHz. After that I can't hear unless the volume is turned way up around 100 dB. I don't do that anymore.
I consider REW and the Umik-1 mike, highly accurate, as it has widespread use in the industry by the professionals. Same with the MiniDsp.
Moved crossover points today from 800 Hz to 1000 Hz, and 3500 Hz to 4000 Hz. These are the points JBL used on these boxes originally.
Also summed the subs for the first time. I'm thinking that is the correct move, but I need to do a sweep against the house curve and look at gain with them summed.
My prior tinkering with REW has helped, but it's complicated. There's no good all comprehensive guide on how to do this
Spent time today reading about time alignment and impulse testing and how to set individual driver delays. I'm going to try to start on that tomorrow.
Tried learning this stuff years ago, but work interfered. Now I have the time to do it.
Listening to the first Infected Mushroom Converting Vegetarians. Hope I don't piss off my neighbors. The bass never stops. Finally getting the 700 WOPL broke in.

Converting Vegetarians at 110 db plus has some fine sonic impact. The floor Tom especially can make me jump at times.
A feature of the Ashly is being able to mute any driver of any channel. After muting the woof and the tweeter it was pretty evident why the mid horns deserved the big bucks..

 

[George S.]

The ability to mute individual drivers is important for setting the impulse timing.
I plan on making one of the subs the timing standard, then align all the other drivers to it one by one.
The ability to mute the individual drivers is in the MiniDsp plugin software. The impulse measuring functions are in REW.
One of the shortcomings of the now "Legacy" MiniDsp I use is it only offers 9 ms of delay per driver. The new units offer much more.
Hopefully 9 ms will be enough for the drivers in the JBL cabinets. The sub cabinets can be physically moved forward or backward to fall within spec. From what I've read the 9 ms span is mostly a issue with home theater subs spread around a room.
We'll see.

 

[laatsch55]

The ability to mute individual drivers is important for setting the impulse timing.
I plan on making one of the subs the timing standard, then align all the other drivers to it one by one.
The ability to mute the individual drivers is in the MiniDsp plugin software. The impulse measuring functions are in REW.
One of the shortcomings of the now "Legacy" MiniDsp I use is it only offers 9 ms of delay per driver. The new units offer much more.
Hopefully 9 ms will be enough for the drivers in the JBL cabinets. The sub cabinets can be physically moved forward or backward to fall within spec. From what I've read the 9 ms span is mostly a issue with home theater subs spread around a room.
We'll see.

The PS2 Driverack has those features also.
They have pre-loaded crossover specs for alot of speakers. Plenty of preloaded crossover setups.....but none for a speaker that has been in continuous production since 1947....AND.. .the is no preloaded straight 3 way crossover profile....with woof, mid and tweet. A lot of sub and two wsy...

I was stunned....

 

[George S.]

I made a polarity error at the very start. The JBL's have the well documented negative polarity where the cones pull in during battery testing. I checked each driver individually for DCR and polarity, and was very careful in rewiring the cabinets. The subs are standard positive polarity, duh!
Reversed polarity on the subs to match the JBL's and was able to drop all extra gain matching from the sub amp to match the Harman curve. Details, details, details!

 

[Gepetto]

I made a polarity error at the very start. The JBL's have the well documented negative polarity where the cones pull in during battery testing. I checked each driver individually for DCR and polarity, and was very careful in rewiring the cabinets. The subs are standard positive polarity, duh!
Reversed polarity on the subs to match the JBL's and was able to drop all extra gain matching from the sub amp to match the Harman curve. Details, details, details!

plus it sounds better that way...

 

[J!m]

Um, 9ms is like 3 meters. That should be plenty and I would be concerned about having fine enough resolution between 0 and 9ms.

 

[George S.]

Um, 9ms is like 3 meters. That should be plenty and I would be concerned about having fine enough resolution between 0 and 9ms.

Yup, did some more reading. 9 ms is massive.

 

[George S.]

Been reading about and watching home theater setup videos for several days.
Even the professionals have differences in how they implement active DSP crossovers.
Nice thing about software is it's easy to discard preferences and reboot to a fresh slate. Been doing a lot of that.
Getting there through trial and error. Slowly.

 

[George S.]

Impulse measurement of the JBL tweeter and midrange. The midrange has a 1 ms delay applied to it. The tweeter has no delay, therefore the tweeter fires before the midrange. The horizontal graph is time in ms, with the tweeter indexed at t=0.

Precise measurements can be made. Here is the peak of the midrange at 1.152 ms.


To align the two. Take the 1 ms delay off the midrange, and apply a 0.152 ms delay to the tweeter. And, we have this, driver alignment. The midrange is aligned to the tweeter.


The woofer is similarly aligned to the midrange with delay placed on the midrange. That delay is then added to the tweeter delay. So midrange and tweeter are then aligned to the woofer.
The woofers will have no delay until individual cabinets are aligned to each other. Then one woofer will have a delay, and that delay will be added to the other drivers within the cabinet.
It gets complicated quickly, and the REW software is stellar, but also complicated.

 

[Skratch]

Does it have to be retimed every time you move the speaker?

 

[George S.]

Not for drivers within the cabinet. Only if you move the cabinets in relation to other cabinets you've matched timing to. Guess that's why they mark the floor.
This rabbit hole goes very deep. They talk about much that I don't understand and use shorthand phrases for words I need to look up, and still don't get. This driver timing is extremely basic and important in setting up a system.
The ability to precision measure impulses with REW and a Umik mike is rather amazing.
Lots of functions in the software, and it appears to be very popular with the Pros.

 

[mr_rye89]

This is interesting, I put a little delay on my woofers cuz they sit ahead of my tweeters a bit. The voice coils of the tweeters are on the back of the compression drivers.... The Dayton app has the delay in in/cm but I read those don't work, only on milliseconds. I got the delay set under 1 ms I think, I'm not sure of the distance between the voice coils of the drivers......

 

[George S.]

From what I've read, it's hard to impossible to integrate subs accurately using impulse because the subs frequency is so low.
One fellow on the Klipsch Forum does it this way. I'll give it a try once I get to that stage. This is a good read.
https://community.klipsch.com/index...rew-to-determine-time-delays-between-drivers/