Basschat 1x12 Active FRFR Cabinet

[Chienmortbb]

Input board populated, 

[basstone]

It's Looking good and a similar concept that I had in mind, even down to the same power amp module. My only proposed addition would be to consider either phantom power on the balanced input or a DC out to power the effect pedal. Thus removing the need for either batteries or an additional power brick.? Any thoughts?

[Chienmortbb]

On 15/07/2019 at 19:12, basstone said:

It's Looking good and a similar concept that I had in mind, even down to the same power amp module. My only proposed addition would be to consider either phantom power on the balanced input or a DC out to power the effect pedal. Thus removing the need for either batteries or an additional power brick.? Any thoughts?

It can be done but both add complication. Pedal supply would be a 9V regulator and the aux supplies on the 125ASX2 has a limited current draw, 350mA if I remember rightly.  This is not even enough to power a Zoom B1 ON or B1 Four let alone a Helix. The HX Stomp needs 3A at 9V.

I could run the pre-amp supplies at +/-9V to simplify matters but that would reduce the headroom in the preamp. I have assembled a fixed voltage +/- 15VPSU for the preamps 

Phantom Power could be put in the final unit but for the prototype I want to prove the concept soI am keeping it simple. 

Personal natters are keeping me from the project at the moment but it is progressing if more slowly than I had hoped.

[basstone]

12 hours ago, Chienmortbb said:

It can be done but both add complication. Pedal supply would be a 9V regulator and the aux supplies on the 125ASX2 has a limited current draw, 350mA if I remember rightly.  This is not even enough to power a Zoom B1 ON or B1 Four let alone a Helix. The HX Stomp needs 3A at 9V.

I could run the pre-amp supplies at +/-9V to simplify matters but that would reduce the headroom in the preamp. I have assembled a fixed voltage +/- 15VPSU for the preamps 

Phantom Power could be put in the final unit but for the prototype I want to prove the concept soI am keeping it simple. 

Personal natters are keeping me from the project at the moment but it is progressing if more slowly than I had hoped.

OK I understand and agree it will be good to prove the concept. I am also am aware of the amp module aux power limitations and any external power output would need to take that into account. I have a zoom A3 and B1Xon that I plan to use with the cab and both have current draw of about 100mA  9v measured but are quoted as 500mA in the specs.

[Chimike]

Just a bump, to keep the interest going, this looks exciting.

[Chienmortbb]

Thanks for the bump. Apart from ilness and the aforementioned personal matters, I have just joined a new band and am frantically learning new songs. I hope to have a prototype at the Big Fat South West Bass Bash bua as that is one week before our first gig it might slip.

[Chienmortbb]

I have had to modify this project due to ........ guess what? So I am prototyping some of the bits, in a lockdown build renovating an Ashdown After Eight. I will post it in the builds area and post a link here as soon as I can. TheBasschat 1x12 Active FRFR Cabinet is still alive and will be completed after we get out of lockdown.

[Chienmortbb]

The new thread is at

 

[basstone]

My own active BC12 cab project has also been stalled due to other priorities and my repair business is now starting to pick up again and one of the items brought in last week for repair was a Mackie TH-12A active speaker. Why is this of any interest or relevance? I found that the DSP input module had failed and being SMT and not repairable I  my only realistic option was to buy a complete upgrade kit for £139 plus £6.99 postage. This kit includes all the electronics ready assembled including; balanced input board with level control, 3 way parametric equaliser with bypass switch, active crossover, input EMC filter, SMPSU and dual amp module with 300W class D LF amp and 50W HF amp. The PSU and power amp are mounted on an alloy heatsink/ mounting bracket and the preamp boards stack on 4 spacers. All Fairly lightweight and compact. It would just need an input panel and mounting inside the cab. I wonder how well the active crossover would match the BC12 design? An alternative would be to use just the LF 300W amp with full range input and use the existing passive crossover design.

Here is the link to the supplier:

https://sbsav.co.uk/shop/59588-mackie-thump-th-12a-digital-to-analog-rework-kit.html

Any thoughts?

[tauzero]

My personal experience with Mackie active speakers (SRM450 mk 2 IIRC) hasn't been great, with a couple of boards needing replacing despite them not being heavily used. I eventually gave up on them and went to RCF. I'm not exactly a large sample though.

[Owen]

My SRM450 experience was no headroom. 

[Chienmortbb]

The basics look good but the active crossover is time aligned for the drivers in the Thump and in the BC112, the crossover frequency is much lower than the 3KHz published. Twwelves will beam considerably below 3Khz so in my opinion it is a bit high.

 

[Chienmortbb]

9 hours ago, tauzero said:

My personal experience with Mackie active speakers (SRM450 mk 2 IIRC) hasn't been great, with a couple of boards needing replacing despite them not being heavily used. I eventually gave up on them and went to RCF. I'm not exactly a large sample though.

I believe there was a period when RCF made active speakers for Mackie.

[Owen]

I believe that the Mark 1 SRM450 were RCF. They ran out of headroom pretty quickly when used as a bass cab.

However, when paired up with an SRM 1500 sub I could slay whole rooms.

Portable rig? No. Used irresponsibly? Guilty as charged.

[basstone]

48 minutes ago, Chienmortbb said:

The basics look good but the active crossover is time aligned for the drivers in the Thump and in the BC112, the crossover frequency is much lower than the 3KHz published. Twwelves will beam considerably below 3Khz so in my opinion it is a bit high.

 

I suspected that would probably be the case. If I have time I could measure the actual crossover frequency response when I get the parts to repair the speaker. I can't find the schematic for this analog preamp and surface mount boards are tricky at best  to modify but it could be possible to feed a full range signal to the LF amp and retain the passive crossover.

[stevie]

It looks like an interesting project. However, if you want to by bypass the passive crossover in the BC12 cab you'll need to be able to programme the crossover and DSP. I've no idea if that's possible. Simply bypassing the passive crossover with the Mackie one will not work properly and will definately sound worse (as Chienmortbb has already said).

To adjust the active crossover, you'll have to time align the drivers by delaying the woofer. Then set the crossover (24dB L/R) to 2kHz and use the parametric function to equalise the response of the CD horn. If you're going to use the separate 50W amp for the HF, you'd need to adjust the sensitivity to compensate for the higher sensitivity of the HF driver.

Even if you can do all this, chances are that the passive crossover will sound better anyway. So I'd agree that connecting a full range signal to the regular input on your cab is probably the best solution. Should be good.

Edited September 21, 2020 by stevie

[basstone]

22 minutes ago, stevie said:

It looks like an interesting project. However, if you want to by bypass the passive crossover in the BC12 cab you'll need to be able to programme the crossover and DSP. I've no idea if that's possible. Simply bypassing the passive crossover with the Mackie one will not work properly and will defintely sound worse (as Chienmortbb has already said).

To adjust the active crossover, you'll have to time align the drivers by delaying the woofer. Then set the crossover (24dB L/R) to 2kHz and use the parametric function to equalise the response of the CD horn. If you're going to use the separate 50W amp for the HF, you'd need to adjust the sensitivity to compensate for the higher sensitivity of the HF driver.

Even if you can do all this, chances are that the passive crossover will sound better anyway. So I'd agree that connecting a full range signal to the regular input on your cab is probably the best solution. Should be good.

The Mackie amp kit replaces the original DSP with analog circuitry, which although easier to modify is still not straightforward! Picking up a pre-crossover signal  from the preamp should however be fairly straightforward, retaining the input and tone controls and hopefully at a suitable signal level to feed the main LF power amp then feed the existing passive crossover. Another possibility may be to feed the full bandwidth signal to both amps and split the passive crossover for the 2 inputs!

I have no immediate plans to try any of this out as I'm already on the same Icepower route as this original project (based mainly on the fact it is already proven in several good bass amps - my own GK SB500 included). I just thought as I came across it, it could be interesting as potentially there is less work involved than developing a preamp and phase splitter required to drive the Icepower modules.