Next step for DSP based OB

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Parts List....

Arcam Alpha 9 - 12" Sealed Sub
Cambridge Audio 640a - Mid(850439)+HF(xt25tg03) - Passive XO (2k)
1 x MiniDSP - Sending LF to SUB

You can imagine whats next!! Funds have finally come around and its time to get another mini and an amp for the HF, then some sort of preamp for control.

I've looked at quite a few options but for anybody who knows me I really have no idea what I'm doing

My current thinking is a T-amp for the HF and a B1 for the Pre but I really am open to suggestions.

All post welcome


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Joined 2004
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10dB is a lot, but not uncommon in OB. It means gobs more power is needed. Does not matter if passive or active, you still need the headroom. So size your amp accordingly. You are now down to effectively 77dB/W worst case. Actually better than that with 2 drivers and he front-rear firing thing.

Very interested to learn how you like the miniDSP in this application
I like your wood working, nice job. Did you sew the black covers?

I just started using miniDSP (two of them). I like them so far, although I still haven't finalized it. I use +15dB of EQ on the mid and woofer, and I think that is causing the miniDSP output to clip, although on its own internal meters dont indicate that.

You might not need a preamp - the miniDSP has a single pot that can control many miniDSP kits. The only thing I need is to find a programmable motorized pot, so I can use my remote with it.

Keep us posted!
Some great suggestions guys, thankyou.

The rubber suspenders are from Bunnings (AUS) and are really ladder/gutter holder thingies. They come with a hook through an eyelet at each end which can be removed then simply put a screw/bolt through and your done. They seem to work well in the isolation roll as i cant feel any vibration at the far end when playing music. They also come in different lengths and have an American patent number on them.

I did sew a piece of material in a tapered tube shape to cover the stands, my better half loves the look and i tend to agree, although there is some tweeter attenuation which i hope to measure one day.

The match between drivers/equalization/amp headroom is going to be interesting. Seeing what happens with so much eq at the minidsp output will be to. Could i raise the low end and drop the top to balance excess at the outputs of the mini??

The great thing about this project is the 1 day it took me to get it built and running, and no sanding/painting !!!!!!!!!!!YAY!!!!!!!!!!!!

I was thinking a seperate preamp module so i can switch my inputs.
Any suggestions?



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Joined 2008
I see that you have mouted the two mids in push-pull arrangement, which is a good idea. I would recommend that you look into the offset between them, as the "wrong" off-set will lead to cancellation between the two. With my own Seas 5" I found that they had to be aligned so that the front of the chasis on both were at the same vertical axis to avoid cancellation in the on-axis (straight forward) direction.
Use a IR preamp kit, and rewire the pot (or resistor network) to the minidsp's volume control pins. This way a simple stereo or even mono pot can control volume of all outputs.

Volume only:

Volume + input:

Both are cheap options, you can pay more if you wish. PS i have not confirmed either option is correct for minidsp volume pins.
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The rubber band thingies look like what american truck drivers call "tarp straps".They come with a metal hook in each end,that can be removed and would leave a hole in the end of the rubber part that a screw could be put through.They come in lengths from 6" to 48" and are only a couple of dollars.You can find them at any truck stop.You may have to search around for the different sizes.

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