Dead D-Bass15, crossover frequency.

[Jean-Claude55]

Hi, first question on this forum, hope somebody can help.

So, I have a Roland D-Bass15 which caught fire one evening. The amp, not the cab. I've re-purposed the cab as a 1X15, using a GK MBS iii, and it works fine (nicer tone than the Roland amp and no faffing about with 'modelling') I've used it like this for a couple of years however I keep thinking that I should wire the hf horn back in. I understand that I need to use an 8 ohm crossover with a reasonably high wattage rating but I cannot decide at what frequency I should cross-over. Roland's website has not been much use. Does anybody have a view on this?

 

[seamonkey]

What did you do with the original crossover?

 

[BogeyBass]

Depends on the tweeter horn.

With a single speaker driver and a horn to mate with it
I wouldn't expect the actual tweeter to be more than 25 to 40 watts. The crossover doesn't have to handle massive power.

Assume resonance of typical bass tweeter to be around 1.8 to 2k

So the lowest most would go would be around 2k
Then again that is very low.
Assume the crossover to be set around 3k to 5k

 

[BogeyBass]

What did you do with the original crossover?

From what I can tell Roland includes a tweeter level control on the front panel with the EQ
It's possible a active crossover

I can't tell if it's a horn , piezoelectric or a paper cone tweeter far as the driver

 

[seamonkey]

From what I can tell Roland includes a tweeter level control on the front panel with the EQ
It's possible a active crossover

I can't tell if it's a horn , piezoelectric or a paper cone tweeter far as the driver

Found a schematic (I think)
https://music-electronics-forum.com/filedata/fetch?id=842344

Looks like the crossover is on the chassis. It should be simple to add one though.

 

[Jean-Claude55]

Thank you for your responses.

I think I may have caused some confusion. The amp in question is (was) a D-Bass 115. The original amp section included a crossover but I don't know whether it was active or passive. Roland claimed outputs of 220w to the bass driver and 80w to the horn which seems to me to imply an active crossover. The loudspeakers are a 15" neo. bass driver and a horn. The horn has a neo compression driver and a mouth of roundabout 4". I haven't taken it to pieces but it looks as though it has a 1" throat. The only mark I can see on it is the word 'Neodymium'.

There is plenty of room to add the crossover and an attenuator.

Once again, any help with crossover frequency would be appreciated.

 

[Jean-Claude55]

Just had a look at the Celestion website, they recommend a minimum crossover frequency of 2,200 for all their 1" neo compression drivers. I'm thinking that 2.5k is probably going to be a good bet. 15" neo bass drivers look as though their response typically drops off heavily around 3k so again 2.5 sounds about right to me. Does this make sense?

 

[Jean-Claude55]

Pulled the horn to see if there was a part no. visible. There isn't. Here are some photos anyway............... .

 

[seamonkey]

Found the service manual
Roland D-Bass 115, 210 Service Manual.pdf 9365 Audio Schematics and Service Manuals files magnet Collections

It is Bi-Amped (Tri-Amped actually)
It's a shame it was junked, it looks like a cool amp.

You could start at 2.5k, and then adjust it if needed.

 

[Jean-Claude55]

The amp was OK I guess, but the cost of repairing it was just mad. The new main board was roughly what I paid for the amp in the first place. I used it mostly for double bass and you could get a nice sound with everything at about half and the modelling not selected. With electric (fretless) bass I found it hard to get a nice warm tone. I realise that my tonal tastes are not necessarily the same as other people's but there it is. With the GK amp that I now use I find it so much easier to get the sort of tone that I want.

So I think I will try 2.5k and see how it goes. Many thanks for your help.