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Chienmortbb

Basschat 1x12 Active FRFR Cabinet

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Posted (edited)

Many of you wil have followed the Basschat 1x12 Cabinet threads over the last few years with sterling work from Phil Starr and Stevie. The latest version has been compared favourably with boutique cabs such as Fearless.

The MK2 cabinet design is just about complete and with the availability of a flat packed cabinet kit, has attracted a lot of attention.

The cabinet has a Full Range Flat Response but many people like the idea of an active FRFR with the amplifier built in. This thread will follow the development of the active version. 

Initially we will add pre-amp and power amp to the exiting passive design. Unlike FRFR PA speakers the circuitry, the inputs will be limited to those needed by us bass players. 

Maybe, if there is interest, a fully active system will be considered.

 

The current spec is:

The current thought  is for the following facilities.

  • Balanced line input, XLR with sensitivity of 0dBm(0.775V).
  • Balanced line output for DI or to feed a second cabinet.
  • Jack input instrument level/high impedance.*
  • Speakon output to passive cab.
  • Fixed HPF tuned to the driver/cabinet combination. Actual Frequency and filter  order TBC. (Added 4/05/19)
  • Volume control.
  • ICEPower 125ASX2** or 700AS1 power module. (Added 4/05/19)

**The 125ASX2 wil output over 280W into this cabinet at 1% THD+N more than enough to power this and one other BC1x12 and is easier to obtain. However the 700AS1 is an even better  module but much harder to get. (Added 4/05/19) Apart from the mechanical differences the electrical interface is almost the same..

I do not intend to put any EQ on the unit as that would be a combo. 

 

Edited by Chienmortbb
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Sounds interesting!

 

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Are you looking at 2 different amps for the woofer and tweeter, and dsp to keep things under control? Is that what you mean by a fully active system?

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Interested. Can we retrofit after we have already built, would be a question I have...

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Funkle, I am looking at whether the amp could be easily retrofitted to the cab although it would be easier to do it as the cabinet is assembled

Moonbassalpha Yes we are looking at a bi-amped system with DSP but not until after we have the amplified passive crossover done.

 

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Is the FRFR version going to be a standard rectangular cab design or will it be configured to use a wedge as well like most commercial FRFRs? Also what do you consider to be inputs needed by bass players? Unbalanced Jack? Balanced XLR? Both?

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It's a fairly easy DIY jigsaw job to alter the cutout so that the horn fits both ways. You don't even need to change the screw holes.

Big RedX, a wedge version isn't on the cards. Because of the crossover point and the vertical dispersion of the horn, you don't need to tilt the cab to hear it.

 

 

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It's all very much in an embryonic stage. So please submit your ideas and comments.

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I forgot to mention, Subsonic, that the piece of wood we cut out to make the (rectangular) hole for the horn is used for the input panel on the back of the cab. Just about every square centimetre of the sheet of plywood is used in the cabs - there's virtually no waste. So altering it would be problematic.

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16 hours ago, stevie said:

I forgot to mention, Subsonic, that the piece of wood we cut out to make the (rectangular) hole for the horn is used for the input panel on the back of the cab. Just about every square centimetre of the sheet of plywood is used in the cabs - there's virtually no waste. So altering it would be problematic.

Of course it would not be that hard to fit another piece of wood in to allow the orientation to change but it does rather defeat the flat pack idea. 

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Just for completeness I will note on this thread as well that any preamp would be improved with an Fdeck HPF as the first stage of the input. 

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Posted (edited)
1 hour ago, Chienmortbb said:

Of course it would not be that hard to fit another piece of wood in to allow the orientation to change but it does rather defeat the flat pack idea. 

The horn is one of those types that has been designed to be rotated, which is quite a useful feature for monitors. All you need to do to fit the horn horizontally is to cut two small pieces out of the horn aperture on the baffle. When you see the cutout, it's dead obvious and fairly simple to do - even with a small handsaw.

If you're planning to rotate the horn, be sure to fit t-nuts rather than wood screws.

Edited by stevie

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6 hours ago, owen said:

Just for completeness I will note on this thread as well that any preamp would be improved with an Fdeck HPF as the first stage of the input. 

I agree than an HPF would be useful and one of the options is a fixed frequency HPF. I have a lot of respect for Francis Deck's designs.

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The actual HPF aspect of it is great, but it is actually the fact that it just makes everything sound nice that makes me like it. I am open to being schooled here, but any passive instrument likes a high impedance input, no?

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Posted (edited)

We need opinions now. Just to be certain, I am not looking at designing a combo or a DSP driven multi purpose cabinet at this stage.. This is an active speaker with inputs suited to bass players. 

Your help is needed.

The current thought  is for the following facilities.

  • Balanced line input, XLR with sensitivity of 0dBm(0.775V).
  • Balanced line output for DI or to feed a second cabinet.
  • Jack input instrument level/high impedance.*
  • Speakon output to passive cab.
  • Volume control.

I do not intend to put any EQ on the unit. 

The amplifier module will be an ICEPower unit. My preference is for the 700AS1 but this is not easy to get. The prototype will feature an ICEPower 125ASX2. Not such a high power module but easily available.

Owen has already requested an HPF and this is under consideration but as I said before,  I do not want to over complicate matters. There is limited space on the panel unless people are prepared to modify the cabinets themselves.

So let me know what you think is important and also if anything I have suggested is not important. * For example the jack/instrument input has been the subject of discussion between the three of us offline. Is it needed or not?  

Edited by Chienmortbb

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30 minutes ago, Chienmortbb said:

Owen has already requested an HPF and this is under consideration but as I said before,  I do not want to over complicate matters. There is limited space on the panel unless people are prepared to modify the cabinets themselves.

If it were me, which it’s not, I would have an always-on HPF designed to fit this cabs excersion limits. That way you are custom designing a solution for this specific cab. In my mind A general frequency selectable HPF is a different bit of kit to solve different problems and better suited to the preamp stage. 

... mind you I’ve read this and if you’re using DSP for the crossover maybe the fixed HPF is just a natural thing that “of course we would do that” 

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Posted (edited)

OK I have always prefered an HPF myself so I will add it in. The DSP option is for later and I may just go for an analogue active crossover in the second phase. DSP is more versatile but I worry that the extra  prpopagation delay ( usually wrongly called latency) caused by the processing may not work well if you use a digital modeller and digital wireless system.

Edited by Chienmortbb
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If you are going to have a volume control, and especially if you are going to have a DI pass-through socket, it needs to be on the front of the cab, or somewhere that is more easily accessible than the back panel.

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BRX is correct. I have a Berg IP which I love dearly (I might have mentioned that?). The sockets, switches and mains are on the back. It is a royal pain. They could go front or side, and I can see issues with both of those, but the back is just inconvenient. 

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The grille that Stevie is proposing is full height, So rather than change the grille I would suggest top front!  

In that case the Speakon output would remain on the back,  as it is on the passive cabinet, it simplifies the connector plate too.  I will look at the position of that once I get my flat pack. 

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On 03/05/2019 at 22:31, Chienmortbb said:

* For example the jack/instrument input has been the subject of discussion between the three of us offline. Is it needed or not?  

Make the input socket a combo XLR / 1/4" and have the gain control (volume) take in to consideration the live difference between line and instrument. - Thus, folk can feed the active cabinet with either Mic or Line level via XLR Balanced or Instrument / Line level via the 1/4" Unbalanced. This would cover all possibilities coming out of preamp pedals or mixing desks.

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