Speakerplans.com Homepage
Forum Home Forum Home > General > Newbie Discussion
  New Posts New Posts RSS Feed - Passive crossover design
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Passive crossover design

 Post Reply Post Reply Page  12>
Author
Message
Tbone View Drop Down
Registered User
Registered User


Joined: 30 March 2024
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Topic: Passive crossover design
    Posted: 30 March 2024 at 3:51pm
Hi everyone, I've been refurbing some soundlab p115cve which I managed to blow nearly a year back. As I wasn't able to source the original drivers to utilise the original crossover I got some new drivers and I'm now making my own crossover!

The drivers I'm using are, celestion cdx1 1010 loaded in a horn and a celestion TF1525e and I've blocked the existing holes for the piezo tweeters and ports that were in the original box as I didn't want to make the design more complex (as this is my first time making a speaker). I will be powering two of these boxes with a thoman t amp e800.

I've used VituixCAD to design a crossover and came up with this, https://imagizer.imageshack.com/img922/4427/ssqLtP.png. Now the SPL response isn't ideal but I'm still satisfied with it so I want to make the crossover design shown. I've come up with this list of components bellow:

Low pass filter:

3.3mh inductor: https://cpc.farnell.com/visaton/5025/inductor-air-core-3-3mh-1-0r/dp/FT01430 - https://cpc.farnell.com/visaton/5025/inductor-air-core-3-3mh-1-0r/dp/FT01430

18uF electrolytic capacitor: https://uk.farnell.com/wurth-elektronik/860080773003/cap-18uf-63v-alu-elec-radial/dp/4257015 - https://uk.farnell.com/wurth-elektronik/860080773003/cap-18uf-63v-alu-elec-radial/dp/4257015

 

High pass filter:

3.3mh inductor: https://cpc.farnell.com/visaton/5025/inductor-air-core-3-3mh-1-0r/dp/FT01430 - https://cpc.farnell.com/visaton/5025/inductor-air-core-3-3mh-1-0r/dp/FT01430

18uf electrolytic capacitor: https://uk.farnell.com/wurth-elektronik/860080773003/cap-18uf-63v-alu-elec-radial/dp/4257015 - https://uk.farnell.com/wurth-elektronik/860080773003/cap-18uf-63v-alu-elec-radial/dp/4257015

Lpad:

3.3 ohm resistor: https://uk.farnell.com/multicomp-pro/mp006113/res-3r3-10w-axial-wirewound/dp/3605545?st=3.3%20ohm%20resistor - https://uk.farnell.com/multicomp-pro/mp006113/res-3r3-10w-axial-wirewound/dp/3605545?st=3.3%20ohm%20resistor

8.2 ohm resistor: https://uk.farnell.com/multicomp-pro/mp006185/res-8r2-25w-axial-wirewound/dp/3605625?st=8.2+ohm+resistor - https://uk.farnell.com/multicomp-pro/mp006185/res-8r2-25w-axial-wirewound/dp/3605625?st=8.2+ohm+resistor


I've tried running them through LTSpice but haven't really got a grasp of this software so not too sure what I'm looking for. I was wondering if anyone had more experience with this software and would be able to help me out or if anyone can see some major flaws with the crossover design that might damage my amp or speakers before I go buying the components to make the crossover. Any help would be greatly appreciated!
Back to Top
snowflake View Drop Down
Old Croc
Old Croc


Joined: 29 December 2004
Location: Bristol
Status: Online
Points: 3122
Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 4:22pm
add a zobel (cap and resistor) across the 15" driver or the filter wont work on the rising impedance and it will beam horribly in the vocal range.

use polypropylene caps. just go for a standard value - either 15 or 22uf if that's all you can find. coils are easily adjustable by unwinding some of the turns to get a reasonable filter response. monacor coils are good value

metal clad chasis-mount resistors are only a couple of quid more expensive.

put 3.3R resistor on the amp side of the filter components. and put a polyswitch next to it (probably reduce the resistor to 2.2R because of the resistance of the polyswitch). this provides protection for the whole circuit against over-current.
Back to Top
Tbone View Drop Down
Registered User
Registered User


Joined: 30 March 2024
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 5:44pm
I assume the zobel should be added in parallel to the driver (from what I can tell online)? Why polypropylene caps instead of electrolytic ones? A friend recommended using electrolytic but he doesn't deal much with audio circuit design, so are the polypropelyne ones better for this? 

For the coils then your suggesting I find something with a larger mh value then required and tune it down to the exact requirements? Is it too hard to find an aircore with a value of 3.3mh?

I like the idea of the polyswitch as the last thing I want to do is burn out my drivers! Does this also serve to protect the amp as well? Sorry for all the questions but I just want to make sure I'm making the correct adjustments to the circuit!
Back to Top
Tbone View Drop Down
Registered User
Registered User


Joined: 30 March 2024
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 5:56pm
Originally posted by snowflake snowflake wrote:

add a zobel (cap and resistor) across the 15" driver or the filter wont work on the rising impedance and it will beam horribly in the vocal range.

use polypropylene caps. just go for a standard value - either 15 or 22uf if that's all you can find. coils are easily adjustable by unwinding some of the turns to get a reasonable filter response. monacor coils are good value

metal clad chasis-mount resistors are only a couple of quid more expensive.

put 3.3R resistor on the amp side of the filter components. and put a polyswitch next to it (probably reduce the resistor to 2.2R because of the resistance of the polyswitch). this provides protection for the whole circuit against over-current.

So something more like this? I used the 3.3 resistor value to represent the 2.2 plus the polyswitch
https://imagizer.imageshack.com/img922/6863/sNsN9J.jpg 
Back to Top
Lucasdude View Drop Down
Young Croc
Young Croc


Joined: 16 March 2013
Location: London
Status: Offline
Points: 823
Post Options Post Options   Thanks (0) Thanks(0)   Quote Lucasdude Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 6:10pm
FYI, and not to dampen your good intentions, but I think Nigel @leanbusiness has some genuine Celestion crossovers in stock designed for TF1225/CDX1-1745 which would be very similar to what you're trying to achieve. Just a thought.
Back to Top
Tbone View Drop Down
Registered User
Registered User


Joined: 30 March 2024
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 6:29pm
Originally posted by Lucasdude Lucasdude wrote:

FYI, and not to dampen your good intentions, but I think Nigel @leanbusiness has some genuine Celestion crossovers in stock designed for TF1225/CDX1-1745 which would be very similar to what you're trying to achieve. Just a thought.
I'll have a look at it but if there isn't already one designed for my exact drivers then I don't think it will give the desired performance. Or are the drivers of the crossover you mentioned similar enough to the ones I have that I won't be making compromises on performance?
Back to Top
Lucasdude View Drop Down
Young Croc
Young Croc


Joined: 16 March 2013
Location: London
Status: Offline
Points: 823
Post Options Post Options   Thanks (0) Thanks(0)   Quote Lucasdude Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 7:03pm
They are very similar drivers. All the capacitors are made by Claritycap, so I doubt you will do any better even if you spend 2 or 3 times the price on components. The only difference may be in whatever HF protection the board has, because your 1010 driver is lower power handling than the 1745.
  I would suggest you give Nigel a call. He is an ex-Celestion employee, and probably knows more about their products past and present than anyone else.
  I don't remember Celestion making a single 15"+1" HF cab, because 15s don't behave all that well at higher frequencies. The 12" crossover is probably your best bet unless you want to swap the HF for something with a larger VC and higher power handling.
Back to Top
Tbone View Drop Down
Registered User
Registered User


Joined: 30 March 2024
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 7:05pm
I found this design on the Celestion website which uses the subwoofer that I have ( but a different tweeter and horn) https://celestion.com/wp-content/uploads/2019/10/188.pdf. When I applied it to my speakers it seems to work well but the impedance spikes are a bit wild (https://imageshack.com/i/pooWRA1Tj), should I look to adapt the high pass section of this crossover to work better with my tweeter, or just adopt the suggested design? 
Back to Top
Lucasdude View Drop Down
Young Croc
Young Croc


Joined: 16 March 2013
Location: London
Status: Offline
Points: 823
Post Options Post Options   Thanks (0) Thanks(0)   Quote Lucasdude Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 7:14pm
Yes, that design uses the 1747 HF which is a 1.75" VC compared to your 1010 which is a 1" VC
Back to Top
Tbone View Drop Down
Registered User
Registered User


Joined: 30 March 2024
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2024 at 7:42pm
Originally posted by Lucasdude Lucasdude wrote:

Yes, that design uses the 1747 HF which is a 1.75" VC compared to your 1010 which is a 1" VC

So something like this to adapt to the smaller VC of my driver? https://imagizer.imageshack.com/img922/3167/2yV61Y.jpg, while keeping the polyswitch in front of the 3.3ohm resistor?
Back to Top
studio45 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 16 October 2007
Location: United Kingdom
Status: Offline
Points: 3864
Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2024 at 2:07pm
You might find that the compression driver has more output in the 2-5k region than 6k+, and therefore moving its filter point up (while leaving the bass filter unchanged) and increasing its level could give flatter response on axis. Or, you can EQ that out with final processing.
Most compression driver/horn combos are like that. There will be a compromise between not having it be too bright on-axis, and having enough of the top end coming out of the horn to ensure wide dispersion. 
As has been mentioned, 15" + 1" is not really considered an ideal combo, mostly due to this problem. At the frequency point around 2kHz where the 1" can take over without having too much distortion, the 15" has a very narrow dispersion; they are only "wide" dispersion up to about 500Hz. Then as soon as the frequency crosses over into the horn, the dispersion is wide again. This means there are some frequencies that don't interact with the room the same way as others, and this results in bad sound for audience off to the side and harsh, unbalanced reflections from venue walls.
You can use a larger horn, to help the 1" driver reproduce lower frequencies without distortion. Or use something like a BMS 4538 driver, which are designed to play a bit lower than the average 1". 
Ultimately though, most 15/1 designs end up with fairly non-ideal dispersion in order to get the on-axis response flat and undistorted. 15/1.4 or 15/2 is a better combo, with a big horn that can support 600Hz at least. 
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
Back to Top
MarjanM View Drop Down
Old Croc
Old Croc
Avatar

Joined: 10 February 2005
Location: Macedonia
Status: Offline
Points: 7816
Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2024 at 5:51pm
Sorry to piss on your parade but that is not how you design a passive crossover.
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713
Back to Top
 Post Reply Post Reply Page  12>

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.109 seconds.