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Passive crossover design

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2024 at 6:52pm
Originally posted by studio45 studio45 wrote:

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. 
I may have to go for the equaliser option it seems. I don't have much more money to be spending on new drivers (and potentially a new amp to power the higher power tweeters), I know this isn't the best option but I most likely will look to upgrade to using a better compressor drive with the 15" in the future and using some sort of 1u equalizer and a compressor to process the sound in the meantime.

If I am going down this route would it be best to use the already designed crossover which has this effect on my drivers: https://imageshack.com/i/pooWRA1Tj, or the adapted my adapted version: https://imageshack.com/i/pm2yV61Yj?
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2024 at 6:54pm
Originally posted by MarjanM MarjanM wrote:

Sorry to piss on your parade but that is not how you design a passive crossover.
Fair enough LOL, I didn't expect this to be the most ideal way to do things but I'm learning as I'm going so hopefully I'll be able to learn better practices for future designs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2024 at 7:15pm
Originally posted by Tbone Tbone wrote:

Hi everyone, I've been refurbing some soundlab p115cve which I managed to blow nearly a year back. 

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.
Ports should likely remain. Did you model the cab in an application like WinISD before buying drivers? The woofer(it's not a subwoofer) must be matched with an appropriately sized enclosure to perform even adequately, or given you already have a cab you want to find a driver that will deliver decent results in it. 


Originally posted by Tbone Tbone wrote:

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
That looks terrible honestly, the woofer doesn't like a sealed box that size(big spike at 60hz) and a 2nd order crossover isn't steep enough to produce sufficient out of band rejection in the crossover region or to offer enough protection for the CD. A 1" exit CD will need a 3rd-4th order crossover up around 2khz just to survive PA use. 







Edited by Conanski - 31 March 2024 at 7:18pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2024 at 9:02am
Originally posted by Conanski Conanski wrote:

Originally posted by Tbone Tbone wrote:

Hi everyone, I've been refurbing some soundlab p115cve which I managed to blow nearly a year back. 

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.
Ports should likely remain. Did you model the cab in an application like WinISD before buying drivers? The woofer(it's not a subwoofer) must be matched with an appropriately sized enclosure to perform even adequately, or given you already have a cab you want to find a driver that will deliver decent results in it. 


Originally posted by Tbone Tbone wrote:

I've used VituixCAD to design a crossover and came up with this, https://imagizer.imageshack.com/img922/4427/ssqLtP.png - https://imagizer.imageshack.com/img922/4427/ssqLtP.png. Now the SPL response isn't ideal
That looks terrible honestly, the woofer doesn't like a sealed box that size(big spike at 60hz) and a 2nd order crossover isn't steep enough to produce sufficient out of band rejection in the crossover region or to offer enough protection for the CD. A 1" exit CD will need a 3rd-4th order crossover up around 2khz just to survive PA use. 






I may have to look at adding back in some ports then, or correcting with some eq (I know not ideal but potentially the best way to resolve it). I did have quite an extensive look online to find the right driver for this box but it does seem like I’ve picked something with too large a VAS for it. 

Alright I’ll have a go at adding a 3rd or 4th order to the HP filter and see if that improves the overall response of it. As for the driver being too large I know it’s not ideal but I don’t really have the money to change this at the moment. My aim will be to repurpose the components used in this crossover for a crossover in a better box (and most likely a different CD) in the future. I’ll have a go at the 3rd/4th order in a bit and see how I do!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2024 at 2:40pm
I think I may opt to change tack as it seems adapting a poor solution with lots of effects and processing won't deliver great sound. I've been chatting to a mate who works with CAD and he said he might be able to help me make some of these CKT-TF1525e System (https://celestion.com/wp-content/uploads/2019/10/188.pdf), with keeping the woofers I have currently and getting new tweeters and horns for it. Does anyone know if I will need a new amp to power these speakers? I'm trying to power them with a T amp e800 which delivers 2 x 350watts into 8ohms (https://www.thomann.de/gb/the_tamp_e800.htm), will this be too little power for the tf1525e and the CDX1 1747?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2024 at 8:59pm
That looks like a similar sized box to what you have... which would make this a lot of work for nothing if true. Take the time to model the TF1525 in a program like WinISD, to do that you need to know the internal volume of your existing enclosure and the port dimensions, and if that Celestion driver isn't already loaded in the software then you just have to add it... but all the TS specs are available from the manufacturer to do that. 
This program will show you what the LF response of the driver/box combo will look like, you also can experiment with port sizes and see how that affects it.

The amp you have is fine, it wouldnt make much difference if you had 500w available.


Edited by Conanski - 01 April 2024 at 9:02pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2024 at 10:40pm
Originally posted by Conanski Conanski wrote:

That looks like a similar sized box to what you have... which would make this a lot of work for nothing if true. Take the time to model the TF1525 in a program like WinISD, to do that you need to know the internal volume of your existing enclosure and the port dimensions, and if that Celestion driver isn't already loaded in the software then you just have to add it... but all the TS specs are available from the manufacturer to do that. 
This program will show you what the LF response of the driver/box combo will look like, you also can experiment with port sizes and see how that affects it.

The amp you have is fine, it wouldnt make much difference if you had 500w available.
I'll have a look on WINisd and simulate it with the origional port sizes of the box that I have and see what it looks like. Although as I won't need to replace my amp to power the new CD combined with the 15" I'm starting to lean more towards the new cabinet idea. Yes it does mean the work I have done on the old cabinets is somewhat pointless now (although some good skills have been learnt), but the benefit of having a purpose made cabinet for the exact drivers I'm using and a guide for the crossover circuit will make constructing the speakers a lot easier overall. I know someone who might be able CNC the parts for me as well which will be really handy for the construction!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 02 April 2024 at 6:19pm
if you are building two way then 12"/1.4" is probably the best compromise. If you use a really good 1.4" compression driver you can cross about 1.3kHz where the 12" beaming hasn't become ridiculous.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 02 April 2024 at 8:08pm
Originally posted by snowflake snowflake wrote:

if you are building two way then 12"/1.4" is probably the best compromise. If you use a really good 1.4" compression driver you can cross about 1.3kHz where the 12" beaming hasn't become ridiculous.

I may have a free plan that would fit the bill. Need some more measurements first.
12NDL88 + HF146.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 02 April 2024 at 11:44pm
Originally posted by snowflake snowflake wrote:

if you are building two way then 12"/1.4" is probably the best compromise. If you use a really good 1.4" compression driver you can cross about 1.3kHz where the 12" beaming hasn't become ridiculous.
Yeah it does look like a better solution but I already have both of the 15" subwoofers, a  case of impulse buying before doing enough research! I think I'm going to build those celestion cabinets for now then look to pair them with other cabinets in the future
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 03 April 2024 at 2:03am
Originally posted by Tbone Tbone wrote:

Yeah it does look like a better solution but I already have both of the 15" subwoofers, a  case of impulse buying before doing enough research! I think I'm going to build those celestion cabinets for now then look to pair them with other cabinets in the future
I had time on my hands so I ran the TF1525 through WinISD, it defaulted to a 321L/11.3 cu-ft enclosure with 38hz tuning for a nominally flat response.Shocked

Looks like these are a classic style woofer. The good news is it still does pretty good in a 4.5cu ft box tuned to 50hz and if my math is correct that is the net volume of the cabs you currently have... tough the ports will have to change.
A 1.4" or 2" exit compression driver is the correct mate for a 15' woofer but the 1" you have can sound fine, there are literally millions of them out there in the wild in use every day. But don't expect ANY low bass from these things, are you planning to use these with subs?


Edited by Conanski - 03 April 2024 at 2:06am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tbone Quote  Post ReplyReply Direct Link To This Post Posted: 03 April 2024 at 1:49pm
Originally posted by Conanski Conanski wrote:

Originally posted by Tbone Tbone wrote:

Yeah it does look like a better solution but I already have both of the 15" subwoofers, a  case of impulse buying before doing enough research! I think I'm going to build those celestion cabinets for now then look to pair them with other cabinets in the future
I had time on my hands so I ran the TF1525 through WinISD, it defaulted to a 321L/11.3 cu-ft enclosure with 38hz tuning for a nominally flat response.Shocked

Looks like these are a classic style woofer. The good news is it still does pretty good in a 4.5cu ft box tuned to 50hz and if my math is correct that is the net volume of the cabs you currently have... tough the ports will have to change.
A 1.4" or 2" exit compression driver is the correct mate for a 15' woofer but the 1" you have can sound fine, there are literally millions of them out there in the wild in use every day. But don't expect ANY low bass from these things, are you planning to use these with subs?
Hmmm changing the ports could be a bit more challenging then expected, I've started to try and modify these cabs before and they seem to be made of chipboard which has gotten damp at some point because parts of it just flake away. Although as the cabs were cheap I don't really have much to loose with messing with them so I might give that a go.

Yeah the plan will definetly be to run them with subs, for now it will just be with an active sub (a gale storm 8 which I got for dirt cheap) and then in the future I want to build some purpose made subs to go with these as midtops. Potentionally something like a cubo 15" or 18" or a bog standard bass reflex like the type you can find on blue arran designed for the Bnc driver
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