12" Cab Diary Continued

[stevie]

I just checked - and I don't seem to have it. The problem is that I kept developing the cab (it was a diary-style thread) and didn't keep all the details of each stage of development. John who is Chienmortbb built one and he may have kept the circuit diagram. I've asked him.

Otherwise, the Wayback Machine might help..... Sorry!

 

[nekomatic]

No luck with Wayback Machine, but in the meantime I thought to actually take measurements from my cab, and the T-nut holes already there are correctly spaced for the Faital Pro but not the Beyma - which suggests less hassle going with the former.

One option I'm wondering about though (and I guess this is relevant to BCCab builders too, so still on topic) is using an electronic crossover and bi-amping, rather than building the passive crossover - any thoughts? Would you expect any decent HF unit to give good results in that case, or would you stick with the Celestion? 

[stevie]

There are some benefits to crossing over actively, but a properly designed passive crossover does a lot more than roll the drivers off at either end and splice them together in the middle. You also have to equalise the bass/mid driver to compensate for the effects of the cabinet and horn as well as the usual anomalies in the drivers themselves and then you have to deal with the phase problems you get from the spacing of the drivers.

It can be done actively, of course, but you need to be able to delay the bass driver so that LF and HF arrive at the same time at the crossover point. You may have to apply asymetrical rolloffs to compensate for any intrinsic rolloffs in the drivers beyond the crossover point. And you need to be able to equalise the entire system so that it's flat. If you can do all that, and have the measuring gear to ensure that you get it right, you can certainly use another compression driver and horn.

However, sometimes passive is just easier.

John is still looking for the circuit for the Beyma 12 and Celestion CDX1-1445 system and is hopeful.

[Phil Starr]

2 hours ago, nekomatic said:

 

One option I'm wondering about though (and I guess this is relevant to BCCab builders too, so still on topic) is using an electronic crossover and bi-amping, rather than building the passive crossover - any thoughts? Would you expect any decent HF unit to give good results in that case, or would you stick with the Celestion? 

Funny you should ask. I've just bought an INuke DSP amp from @Kevsy71 to investigate just that. The DSP gives you a wide range of options about crossover frequency roll off, delay and so on as well as compression/limiting to protect the drivers. If it is successful it might be a good way to go active by building the amp into the cab for just over £220

[nekomatic]

17 hours ago, stevie said:

There are some benefits to crossing over actively, but a properly designed passive crossover does a lot more than roll the drivers off at either end and splice them together in the middle. You also have to equalise the bass/mid driver to compensate for the effects of the cabinet and horn as well as the usual anomalies in the drivers themselves and then you have to deal with the phase problems you get from the spacing of the drivers.

It can be done actively, of course, but you need to be able to delay the bass driver so that LF and HF arrive at the same time at the crossover point. You may have to apply asymetrical rolloffs to compensate for any intrinsic rolloffs in the drivers beyond the crossover point. And you need to be able to equalise the entire system so that it's flat. If you can do all that, and have the measuring gear to ensure that you get it right, you can certainly use another compression driver and horn.

Fair enough!

[sergelebasse75]

Hallo all, sorry to resurrect the thread again, but after reading all DIYcabs in every color size and tweet no tweet, i decided to use the woofer i first bought, beyma sm212 and i get a very Well priced celestion cdx1 1415, problem now is horn and crossover. As ph170 changed and now is non ferrous, would some of these be a better option? Celestion H1 7050 or Faital pro sth100 (dispersion of Faital 80x70). Maybe new ph 170 still world, i really don't know.. And where could I get the inductors? I was looking for these sizes but had no luck, bluearan had some, but if i there was a continental shop, this would be even better. Thanks a lot!

[RichardH]

These guys are good - I have ordered from them in the past (pre Brexit!)

https://europe-audio.com/intro.asp

They stock a wide range of Jantzen air core inductors - they took some time to deliver when I ordered as they didn't initially have stock, but they came through

Edited April 16, 2021 by RichardH

[Chienmortbb]

39 minutes ago, RichardH said:

These guys are good - I have ordered from them in the past (pre Brexit!)

https://europe-audio.com/intro.asp

They stock a wide range of Jantzen air core inductors - they took some time to deliver when I ordered as they didn't initially have stock, but they came through

https://www.hificollective.co.uk/

[stevie]

The Design Diary progressed from a Beyma SM212 on its own to a Beyma SM212 with a Celestion CDX1-1445 and P.Audio PH-170 horn - all ceramic magnets. The crossover for that system disappeared from Basschat when a particular  image hosting company closed down. Fortunately, chienmortbb has recently located the circuit in his files. So if anyone would like a copy - particularly @nekomatic - just ask.

We then went all-neo with a Faital Pro 12 and the Celestion CDX1-1425 -  again using the PH-170 horn.

Using any other components would mean a complete crossover redesign. The Celestion 1415 could in theory be substituted for the 1425, as they are quite similar. However, their sensitivity is different and you'd need to account for that in the crossover.

As far as inductors are concerned, there's an Ebay.uk seller who winds inductors to custom values in small quantities. The biggest European manufacturer of coils is a German company called Intertechnik, although I don't think they do custom values.

[Chienmortbb]

4 minutes ago, stevie said:

The Design Diary progressed from a Beyma SM212 on its own to a Beyma SM212 with a Celestion CDX1-1445 and P.Audio PH-170 horn - all ceramic magnets. The crossover for that system disappeared from Basschat when a particular  image hosting company closed down. Fortunately, chienmortbb has recently located the circuit in his files. So if anyone would like a copy - particularly @nekomatic - just ask.

We then went all-neo with a Faital Pro 12 and the Celestion CDX1-1425 -  again using the PH-170 horn.

Using any other components would mean a complete crossover redesign. The Celestion 1415 could in theory be substituted for the 1425, as they are quite similar. However, their sensitivity is different and you'd need to account for that in the crossover.

As far as inductors are concerned, there's an Ebay.uk seller who winds inductors to custom values in small quantities. The biggest European manufacturer of coils is a German company called Intertechnik, although I don't think they do custom values.

The crossover circuit diagram is a bit scruffy so I will tidy it up and put it on here later.

[RichardH]

1 hour ago, Chienmortbb said:

https://www.hificollective.co.uk/

...I suggested Europe Audio because @sergelebasse75 asked for a continental based supplier  

[sergelebasse75]

Thank you all, I ll take a look at these shops

 

[funkydoug]

On 16/04/2021 at 11:12, Chienmortbb said:

The crossover circuit diagram is a bit scruffy so I will tidy it up and put it on here later.

Thanks, this would be great. I'm trying to get my head around crossovers so would really appreciate seeing this.

[Chienmortbb]

On 18/04/2021 at 09:08, funkydoug said:

Thanks, this would be great. I'm trying to get my head around crossovers so would really appreciate seeing this.

Sorry for the delay. I will get it done this weekend. 

[funkydoug]

29 minutes ago, Chienmortbb said:

Sorry for the delay. I will get it done this weekend. 

no worries ... and no need to apologise mate, it's not like I'm paying you!

Anything you can share - whenever you can - is appreciated.

[sergelebasse75]

Thanks a lot chienmortbb!

[nekomatic]

On 16/04/2021 at 11:07, stevie said:

The Design Diary progressed from a Beyma SM212 on its own to a Beyma SM212 with a Celestion CDX1-1445 and P.Audio PH-170 horn - all ceramic magnets. The crossover for that system disappeared from Basschat when a particular  image hosting company closed down. Fortunately, chienmortbb has recently located the circuit in his files. So if anyone would like a copy - particularly @nekomatic - just ask.

Ooh, sorry I haven't checked in here in a while so I didn't see this. Yes please, if you or @Chienmortbb has this circuit diagram I would be very interested in seeing it (I don't mind if it's scruffy, you should see some of mine...)

 

[Chienmortbb]

I had a little time so I redrew the crossover on the computer. It is not perfect but it is clearer.

 

 

[martyy]

Any recommendations for places to buy electronic components?   Never mind, spotted the hificollective suggestion above.

Edited May 20, 2021 by martyy

[nekomatic]

Brilliant! Thanks so much. That's plenty clear enough 😁

I feel a plan coming together...

eta: What do you suggest for the wire gauge / dc resistance of the inductors? I'd get the Jantzen ones from hificollective unless I hear any better suggestions, and they offer a range of gauges. I assume the 1.15mH should be a meaty one but what about the two on the HF side?

Edited May 20, 2021 by nekomatic
added inductor question

[stevie]

1mm or 1.2 mm for the bass inductor.  .7 or .8mm for the .5mH value and .6mm for the 1.1mH value inductor, although thicker wire won't do any harm if your choice is limited. Resistors should ideally be 20W. I'd also double up on the resistors in the LF circuit, i.e. 2 x 2.2 ohms for extra power handling. Don't bother with esoteric capacitors. They're a waste of money IMO. But do use film type caps and not electrolytics.

[funkydoug]

 

Is this a 2nd order LPF and 3rd order HPF design? Testing myself here...

 

In case you haven't seen it, blue aran has a crossover configuration thing on their website.  It is interesting  and maybe even useful in this case.

[stevie]

There's no standard formula for crossovers done properly. I've published quite a few on here and they've all been completely different. You have to use the components and circuits that work for the particular drivers and cabinet you're working with. It's like making a bespoke suit or designing a website.

However, like most things in life, it's possible to bodge. The 2nd order LP and third order HP is based on the idea that you don't want two lossy inductors in the path to the woofer if you can help it, and you need to use a fast rolloff to protect the tweeter. There's a lot more to it than that.

 

[funkydoug]

Thanks  Stevie.  

I'm tempted to ask why it is so component specific,  but I guess it's because of how all the different properties of a cab design interact in reality 'on the bench' rather than in the software? 

The tailoring analogy is great. It is of course possible to buy a perfectly decent suit off the peg from M&S (dare I say Asda or is that a 'bodge' too far!?). I guess the difference is that making it bespoke means it is a perfect fit rather than 'good enough'. 

Cheers, I'm learning loads from this ... mainly about how much there is to learn

 

Edited May 20, 2021 by funkydoug

[sergelebasse75]

Thanks a lot chienmortbb Stevie Phil and all the people involved, now i already have woofer and tweeter, Next step, inductors!😃