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dB-Mark XCA 28 - DSP Basics for a Newbie

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Category: General
Forum Name: Newbie Discussion
Forum Description: Newbie Discussion/Questions. Look less stupid here...
Printed Date: 06 June 2023 at 8:16pm
Software Version: Web Wiz Forums 12.06 -

Topic: dB-Mark XCA 28 - DSP Basics for a Newbie
Posted By: SnailSpace
Subject: dB-Mark XCA 28 - DSP Basics for a Newbie
Date Posted: 12 March 2023 at 4:14pm

I bought a dB-Mark XCA 28 (DSP) a few months ago and recently bought a cheap PC Laptop so I could download the software and use the interface to make learning a bit easier.

I’m currently still working on my High & Low boxes but want to learn how to use the DSP on what I will be is using as my Mids for now. Anyway after watching a few basic videos on YouTube from Thai/Vietnam/Malaysian users (this seems to be dB-Marks main market) I now have it working and playing music but the Translate function on YouTube is very sketchy and videos don’t go into the details I need.

So this is where I need to pick your brains to learn the basics. 

The Speakers I’m using (for now! So please don’t ask me why or remind me they are garbage ;) are Jamo 266 D, I have very limited information on them so how do I work out what Frequencies they are capable of producing evenly ‘From’ ‘To’?

4x Jamo 266 D:

Short Term - 265w

Long Term - 150w

4-8 ohm

I will keep it to this one question for now as I have others and don’t want to confuse the issue!

Thanks in advance

Posted By: Conanski
Date Posted: 12 March 2023 at 4:58pm
Well... those are home/studio speakers aren't they? When you play fullrange music through them do they produce what sounds like fullrange sound... within reason? 
I don't know what the published specs are but say they cover 60-18khz, you can safely limit that to smaller range without issue.. in your PA system that might be 100-2khz for example. This assumes that the Jamos are fully functional with no blown drivers or other damage of course, is that the case? It's not likely the 12" driver alone would produce much output at higher mid frequencies so the mid driver in this box would come into play. 

Posted By: SnailSpace
Date Posted: 12 March 2023 at 7:09pm
Yes Home/Studio ‘all in one’ they are a full range speaker comprising of a Tweeter/5”/12”. I can’t find the Specs unfortunately. Yes fully functional no blown speakers.
Thanks I’ll give that range a go…more basic questions to follow ;)

Posted By: SnailSpace
Date Posted: 12 March 2023 at 10:29pm
Question 2.)
I’ve looked at wiki page and read about the origins but is their a simple short answer - Do these filters apply better to a certain setting of sound system or genre/format of music or are they equally great and it’s personal preference?
A. Linkwitz Riley.
B. Bessel
C. Butterworth

Thanks Conanski I’ve used those numbers it sounds nice. Early days of the learning I suppose it gets tricky as I add other outs!

Posted By: Conanski
Date Posted: 13 March 2023 at 12:03am
There are some technical reasons you may select one or the other that has to do with the shape of the filter response and it's phase response, in general you won't hear any difference between them. In short LR filters are commonly used in crossovers as even order filters of this type sum to a flat response, and for PA applications in particular... because driver protection is very important 4th order(24dB/oct) or steeper are more common and recommended.

Posted By: SnailSpace
Date Posted: 13 March 2023 at 11:19am

Thanks Conanski

I imagine my learning and understanding of how the DSP & Interface truly works with the Sound System & Mixer will come when I introduce my High/Low outs. Until then I’m trying not to over fiddle too much. I presume limiters and levels on dsp/amps/mixers should be question 4!

Question 3.) 

Noise Gate - I have had a quick look around and whilst I understand it is for cleaning up noise I can’t find any info on setting it on a DSP  interface in application to a Sound System? The function seems greyed out at the moment for some reason but was it was on yesterday and I noticed it had a ‘dBu’ up and down setting! Do I fiddle by ear to hear if it is reducing or cleaning any noise or is their a general setting/range that noise occurs?

Posted By: Conanski
Date Posted: 13 March 2023 at 1:31pm
A noise gate mutes the outputs when the signal levels drop below a preset threshold, the purpose of this is to reduce the amount of idle hiss or other noise from the speakers when nothing is playing. But most audio systems are pretty quiet these days and the one component that can generate quite a bit of hiss.. the amplifiers, are after the DSP so this function may be of little use.

Posted By: 4D
Date Posted: 13 March 2023 at 2:20pm

60hz might be to low for the Jamo its only a tiny voice coil and they were designed well before modern bass heavy EDM 

but24 hi pass 70hz or even 80hz (let the port do the sub)
lr24 lo pass 20khz 

DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"

Posted By: SnailSpace
Date Posted: 13 March 2023 at 3:10pm
Thanks 4D will have a look at the difference! They sounded ok yesterday but then again it’s in a home setting so I’m not pushing them.

Surely Bass and speakers that could handle Bass existed pre modern EDM? I’m not doubting that they probably don’t have the best voice coil but they were marketed as DJ speakers during the height of the emergence of Electronic Music and post Reggae and they handle pretty well within reason. Or are you saying the modern equivalent of these speakers would be able to handle more?  
But I don’t want to over extend them and damage so will take a look as I don’t have the info it is a bit of guess work.
That leads to another question how do you know besides blowing the cones if I've got the Frequencies right or wrong?  

Posted By: 4D
Date Posted: 13 March 2023 at 3:47pm

That the Jamo's have survived thus far is a testament to their durability. 

Look at any contemporary speaker with similar components and they mostly hi-pass around 60 to 65hz, so for an old girl 70hz is not unreasonable, if they sound to thwock thwock lower it a bit until satisfied but bear in mind, the lower they play the less power they can handle 

DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"

Posted By: SnailSpace
Date Posted: 13 March 2023 at 3:55pm

I take it ‘But’ means Butterworth & LR mean ‘Linkwitz Riley’? 

Ah so you can use different filters for hi & Lo! 

Posted By: teeth
Date Posted: 13 March 2023 at 4:36pm
yes, and i think BE is bessel on that unit

see if anyone has made general videos on LMS / DSP units

the ultradrive is often considered a good "beginner" unit, so this video might be helpful" rel="nofollow -

now you know your way around the dBmark, you can apply what you have learned from other videos to your unit. it's platform agnostic knowledge :]

Posted By: SnailSpace
Date Posted: 13 March 2023 at 4:41pm
I’ve actually got that video saved already as it was a good explanation of Crossover, but thanks good idea I’ll look around for ones showing it via interface too.

I also need to get an iMovie account so I can upload photos of interface controller.

Posted By: SnailSpace
Date Posted: 16 March 2023 at 11:24pm
I found the range of the Jamo’s

  • Efficiency: 95.2 dB (1W/1m)
  • Transitional ranges: 1'800 / 4'800 Hz

(I’m curious to know if the 12” say anything on them, I’ll have a look inside one)

Posted By: Conanski
Date Posted: 17 March 2023 at 3:22am
Originally posted by SnailSpace SnailSpace wrote:

I found the range of the Jamo’s
48-20.000hz Efficiency: 95.2 dB (1W/1m)

That is better than I had suspected... closer to a PA speaker than a home/studio version. The low frequency driver in a speaker like this generally determines the sensitivity for the whole system, so if you wanted to simplify and streamline your system in the future you could build new boxes for the 12's and get rid of the other drivers. The PV drivers/horns will replace the Jamo mid and high drivers.

Posted By: SnailSpace
Date Posted: 17 March 2023 at 8:10am
Thanks that was going to be my next question whether that rating would be based on all speaker or largest.
(I saw a discussion on here where they were slated as the worst speaker ever. I’ve seen photos of the mud and horn and yeah they are basic but balance with the 12” they sound ok as a home speaker. Also I think people based opinion on the magnet size but surely it should be based on sound!)

Anyway I’ve been thinking about what Upper Mids would best work with & compliment my Lower Mids Black Widows, as you say I could use the x4 12” out of the Jamo or I have other 12s I’m wondering if they are more suitable:

I have:

x2 12” Celstion G12/75

-Sensitivity (dB) 97

-Frequency range (Hz) 80-5000

-Chassis type - Pressed Steel Resonance 

-Magnet Type - Ceramic

-Resonance frequency, Fs (Hz) 85

-Voice coil diameter (‘’) 2

 x4 12” McKenzie (Fane) 70w (8ohm) but lacking info on these.

I have x2 boxes that fit x2 12”.

I also have x2 flare boxes that fit x1 12” in each.


x2 15” HH 150w (gonna see if there’s any info on back of these)

x2 15” McKenzie (Fane) 100w (again need to find info on these)

I could try and source x2 of these to make them a balanced x4?

I was wondering if any of these would be any good for Upper Mid?

(Or I could sell Jamos, Celestions are also worth a few quid and use money to fund my 18” and something that fits better with Black Widows range)

Posted By: Conanski
Date Posted: 17 March 2023 at 10:31pm
If you have 4 of the Jamo 12's you are all set, build some 212 boxes with the PV CD's and maybe a different horn that will fit the form factor better to give you something like this..

Posted By: SnailSpace
Date Posted: 17 March 2023 at 11:12pm
 I have the x2 12” dual cabs (not great but suppose I can use them to  see which sounds best as the back opens)

Q) Why do Internal Wires always seem to be very thin silver wore when I open cabs up? What type of wires is favoured for internal wiring?

Posted By: Lucasdude
Date Posted: 17 March 2023 at 11:17pm
Celestion G12 are guitar speakers. Did they come out of a 2x12 combo?

Posted By: Conanski
Date Posted: 18 March 2023 at 5:32am
Originally posted by SnailSpace SnailSpace wrote:

Q) Why do Internal Wires always seem to be very thin silver wore when I open cabs up? What type of wires is favoured for internal wiring? 

The internal wiring in a speaker cab( if original) is usually sufficient to cover the short distance between the cabinet terminal and the drivers at the power levels they are rated for. For longer runs from the amplifier to the speakers larger gauge wire should be used but in your case you probably don't need anything more that 14ga. 

All those drivers you listed are very low power by modern standards and wouldn't be hard to blow under PA uses, I have some Celestion G15-150 drivers that look really beefy but they died pretty quickly in PA cabs... they're just not built for that kind of use. 

Posted By: SnailSpace
Date Posted: 18 March 2023 at 9:10am
Ok probably better off cashing in I suppose and putting it towards the next stage. 

Posted By: SnailSpace
Date Posted: 18 March 2023 at 9:16am
I understand about wire gauges outside of the Cabs but I’ve always wondered why it didn’t apply on the inside.

Does the internal wire have a name as I also need to order some or should I use the old very thin gauge speaker wire I have? I think I have some from an old bookshelf speaker but it might be copper? I don’t think I’ve ever seen copper internally it is always silver?

Posted By: DMorison
Date Posted: 18 March 2023 at 2:54pm
Speaker wire is almost always copper, some of it is just plated to reduce the chance of corrosion.
Use any standard speaker wire of reasonable size, the cost difference between minimal and decent is still less than the cost of delivery so won't really matter - either of these should be fine for example:" rel="nofollow - ," rel="nofollow - .

Posted By: SnailSpace
Date Posted: 18 March 2023 at 6:52pm
Thanks, I’ve probably got some knocking around if not I’ll order some cheers 

Posted By: Conanski
Date Posted: 18 March 2023 at 7:42pm
With my DIY builds I generally use the same gauge speaker wire inside a cab as gets used outside, so that means sub cabs will get heavier wire than mid/high boxes. But that produces a mechanical problem in some cases, the weight of the wire can put strain on the driver terminals so it may need to be clipped to the internal structure of the enclosure to prevent damage occurring over time when the cabs are moved around. 

It's not uncommon to find some really small wire inside mass produced speakers, that might seem like an oversight but the wire in the driver voicecoils and on components in a passive crossover is also really small so it's not as bad as it seems. 
But if you find rigid and/or bare wire inside a cab I doubt that is original, it should always be flexible and insulated. 

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