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Post by jklow888 on Nov 4, 2017 17:28:51 GMT -5
Long time no post - I am in the process of designing/build to start for an open baffle speaker and given the drivers to be used (dual Eminence Alpha 15A's + Tang Band 5" paper cone full ranger per side) the passive xover needs some hefty coils and capacitors which ironically cost as much as all the drivers. One option I would like to consider is going active xover which would be easier to fine tune the OB implementation as I am not working 100% to a tried and tested "recipe" design as the full ranger is different due to availability of the documented/tested full rangers. I am also trying to keep things simple by using a pair of RCA in-wall leads available at the front of my room that gets its source from the back of my (dual 2-channel + HT) room so want to avoid RCA to XLR even though the XPA can take XLR inputs.
So for active xover, the entry level miniDSP 2X4 seems to be a good candidate. But, I have read some threads about concerns on the output being too low as the "standard unbalanced miniDSP 2x4 has a maximum output voltage of 0.9 Volts RMS" and a number of XPA owners having clipping. I can't see a date on that website page but I do see on miniDSP's website there is a rev B option for the base miniDSP with a "2.0Vrms Max". Should I get the rev B or will rev A be sufficient ? Another alternative should I just go for the miniDSP 2X2 HD which is 2.0Vrms Max ?
Hopefully miniDSP owners using XPA's can provide some guidance and comments on their experiences.
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Post by jklow888 on Nov 6, 2017 19:53:32 GMT -5
Anybody ? Sounds like I'll have to go with the 2.0 Vrms units to be on the safe side ?
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Post by geebo on Nov 6, 2017 20:36:58 GMT -5
Anybody ? Sounds like I'll have to go with the 2.0 Vrms units to be on the safe side ? The only difference between the A and B versions is a jumper position. Either board can be converted to the other via this jumper. But that's only for the input sensitivity. The max output is always 0.9V. You have to go with the XLR version or the HD version to get a higher output voltage.
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Post by jklow888 on Nov 6, 2017 21:33:38 GMT -5
The only difference between the A and B versions is a jumper position. Either board can be converted to the other via this jumper. But that's only for the input sensitivity. The max output is always 0.9V. You have to go with the XLR version or the HD version to get a higher output voltage. Ok - thanks for clarifying that. So then is it better to get the unit with the higher output voltage being HD as I am only using unbalanced ?
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Post by geebo on Nov 6, 2017 23:01:44 GMT -5
The only difference between the A and B versions is a jumper position. Either board can be converted to the other via this jumper. But that's only for the input sensitivity. The max output is always 0.9V. You have to go with the XLR version or the HD version to get a higher output voltage. Ok - thanks for clarifying that. So then is it better to get the unit with the higher output voltage being HD as I am only using unbalanced ? I have the HD and it works fine for me feeding a pair of powered subs.
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Post by leonski on Nov 7, 2017 1:49:26 GMT -5
A SINGLE 2x8 would provide enough I/O for BOTH speakers. And extra for a pair of (stereo) subs. the 'kit' has Phoenix Connectors for Balanced and it comes with single ended On Board. you'd only need ONE power supply and could deal with everything at once, when connected to your computer for programming.
I think the 'options' open up a little for the 2x8, as well. Might even be a little less $$$, but that's easy enough to check. I don't see it listed, so it MIGHT be discontinued.
I'd go to MiniDSP boards and try to determine IF one or the other were 'quieter'.
But in any event, since you are starting with what amounts to a clean-sheet design, you'd be best off starting with the speakers OUTSIDE in as open a space as you can manage.
You'll need the analysis mic. and a copy of REW, Room EQ Wizard to do the measurments before starting in on the crossover.
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Post by geebo on Nov 7, 2017 8:08:26 GMT -5
A SINGLE 2x8 would provide enough I/O for BOTH speakers. And extra for a pair of (stereo) subs. the 'kit' has Phoenix Connectors for Balanced and it comes with single ended On Board. you'd only need ONE power supply and could deal with everything at once, when connected to your computer for programming. I think the 'options' open up a little for the 2x8, as well. Might even be a little less $$$, but that's easy enough to check. I don't see it listed, so it MIGHT be discontinued. I'd go to MiniDSP boards and try to determine IF one or the other were 'quieter'. But in any event, since you are starting with what amounts to a clean-sheet design, you'd be best off starting with the speakers OUTSIDE in as open a space as you can manage. You'll need the analysis mic. and a copy of REW, Room EQ Wizard to do the measurments before starting in on the crossover. The 2x8 is alive and still available. www.minidsp.com/products/minidspkits/2-x-in-8-x-out
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Post by jklow888 on Nov 7, 2017 21:29:02 GMT -5
Thanks for the replies - I'll go for the miniDSP HD.
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Post by leonski on Nov 8, 2017 17:10:15 GMT -5
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Post by jklow888 on Nov 20, 2017 4:29:42 GMT -5
LOL - they will be quite big/awkward to get outside without damaging anything. I did read through the 2 way example at their site and some other threads on measuring outside but there will probably be way too much noise outside at my place. I guess when I finally get to it in room measurements/a house curve will have to do.
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Post by leonski on Nov 20, 2017 16:50:03 GMT -5
You start with BARE Drivers. Than work 'up'.
Do you have a signal generator or are you content to use whatever DIRAC or other 'ruom tuner' (a misnomer) uses?
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Post by jklow888 on Nov 22, 2017 17:05:29 GMT -5
I'm not that advanced other than trying to get a xover done that is not passive. So you're advising I should test each driver individually with some amplification outdoors and a laptop + REW + UMIK ?
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Post by leonski on Nov 23, 2017 0:24:02 GMT -5
Not passive is 'active'.
But the real split is between Line Level and Speaker Level. I'm assuming you want powered speakers and thus some form of line level crossover.
Line level goes between preamp and power amp while speaker level is usually in the speaker enclosure, using lots of power and decoupling amp from speaker driver.
Line level is sub divided into Active and Passive.....socalled ALLXO and PLLXO for Passive or Active Line Level Cross Over. Each has a few advantages. Main point FOR a Passive LLXO is that it uses small parts and can be made into an Altoids Tin. Problem is you need to know the Input impedance of the amp and the Output impedance of the PRE. You can afford very good parts, too. But some capacitor values are Exceedingly small. Nothing like the 20mfd or whatever used in the speaker. The downside of a PLLXO? Won't drive long cables and you should probably minimize cable TO the crossover, too. Changing Xover frequencies is a hassle, too, so progress to a finished product may be slower than you'd like.
An ACTIVE LLXO is a neat device in modern times. Computer programable and nearly infinitely flexible. Can drove longer cables and you don't need to know the input/ output impedance of partnering gear. Many have choices from 6db/octave on UP to 48db/octave filter slopes and the MiniDSP stuff has multiple bands up Parametric EQ coming and going. Bewildering, to me. You can ALSO implement FIR filters on some units, which have NO phase shift thru the passband. Neat. But math intensive.
I'd heartily recommend reading the HELPS at the MiniDSP site. Going thru all the steps for a virgin design will be very helpful in getting the most out of it. How are you deciding on the speaker enclosure size? Amount of damping? Port size, if used? Where were you going to start with Crossover Frequencies and how did you decide THAT? Do you have the TS parameters of the drivers?
Lots of stuff to do which scares the crap out of me.
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Post by jklow888 on Nov 23, 2017 17:05:38 GMT -5
Yes - I do want to go line level ALLXO or PLLXO. Originally I started with the various open baffle documented designs but the price of coils/inductors and capacitors was going to be > $100 per speaker for a speaker level passive xover. I know the input impedance of my amp being an XPA-5 per the manual its 47K Ohm. The UMC-1 (yes it is still in action) doesn't have that detail in the manual but in another Emo board thread its confirmed as 1K Ohm. Now my room cabling - this is where I hit an issue needing a hybrid approach: - I keep all my gear at the back of the room, from rear to front I have: - 3 pairs of speaker cabling to front - 2 pairs of speaker cabling to rear ceiling - 1 pair of RCA line out for sub (it is a long run but testing it with CD pre-out from rear to an integrated amp in front there was no hiss/hum/inteference) Sadly if I had just one more pair of speaker cabling to the front or one or two RCA line out to front then I could do all the line level xover in one place. So after reading plenty on the miniDSP site and having modeled a passive xover for my open baffle and all the drivers per their T/S specs I will have to do this: Left + Right - UMC-1 line out from rear to front of room and into miniDSP (or powered analog line level xover), then to XPA-5, then to high/low for each speaker Centre - use miniDSP to model xover - calculate PLLXO for new amp impedance and UMC-1 output impedance - UMC-1 line out to PLLXO to new amp (2 channels) which is close by and then to 2 speaker cable pairs from rear to front of room, then to high/low for the center speaker - another option is to buy a single XKitz xover once I know what works using miniDSP, but PLLXO should be cheaper especially if the UMC-1 dies or I change up gear Rears - continue but to new amp and then onto cabling to Emo in-ceiling with passive xovers So my L+C+R will be all line level xover and direct amplification to the high/low drivers and the rears will remain passive xover driven. BTW - all my drivers landed in Australia after a day in Hawaii Hoping it all gets delivered on Monday and then I can do the final check measures and get the baffles CNC'd and then start on the staining/sanding. Will be another 2-3 weeks before the drivers actually go onto the baffles so looks like ordering the miniDSP HD will happen this weekend !
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Post by leonski on Nov 24, 2017 1:00:01 GMT -5
This would be some reading before 'breaking ground' on your project; Linkwitz makes Fine OB speakers using MiniDSP or 'other'. www.linkwitzlab.comDown at the bottom of the page are some articles which should help. ALSO: Look at my Thread 'Idea Noodle' over in the general section of amps. My original post shows a 'block diagram' which you might want to use. Or at least use as a model for your OWN such diagram. At least for MY Brain Cell, that kind of drawing makes things clear and helps when it comes time to make a parts list. Later, you can get to the cardboard CutOut phase when you start doing the layout of the various pieces intended for ONE case, which might make location easier than having a half-dozen boxes strewn about the listening area.
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Post by jklow888 on Feb 6, 2018 7:03:38 GMT -5
Ok - so finally got the OB build done - drivers mounted, wiring/soldering done, miniDSP HD setup (simple) with 2 inputs and simple 2 way xover @ 200 hz for 4 outputs: Left -> left low + left high Right -> right low + right high Started with a 2 channel amp direct to my full range drivers without miniDSP and then miniDSP with only high line level inputs and it all sounded good. So next moved into place the XPA-5 and then connected left and right full range drivers to channels 2 + 4 for the left and right highs, then connected bi-wired two woofers for left and two woofers for right for left lows and right lows to channels 1 + 5. Checked polarities and for any loose wires and then powered up the XPA-5 - red light cycles through 1-5 and then I get a medium pop on the right speaker and then channels 4 + 5 flash yellow The two woofers per speaker are in parallel and the actual impedance is 5.88 each so in parallel it drops to 2.94 - could the two sets of dual woofers be pushing the XPA-5 just beyond its limits ? I was able to do any combination of 2-3 of the 4 channels without going into protection mode but when all 4 have an RCA signal from the miniDSP it goes into protection mode. Any ideas
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Post by jklow888 on Feb 6, 2018 18:15:59 GMT -5
Damon in Tech Support suggested to replace the RCA leads on my right speaker and that stopped the amp from going into protection mode. Strangely switching that "faulty" RCA pair to the left speaker does not send the amp into protection mode.
Kudos to Emotiva for the fantastic support provided - my unit is a Gen 1 and I just checked - almost 10 years old !
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