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Active/passive MMG help

67.250.119.244
Posted on March 30, 2017 at 12:24:45
atreies
Audiophile

Posts: 5
Location: Hudson Valley, NY
Joined: March 30, 2017



So I've gotten into some woodworking lately and thought I'd try the MMG sandwich frame mod. Came out really well, still lots of finishing work to be done but thought I'd give the functional product a run first. Bought an ART CX311 active crossover to start with. Certainly added detail but it is very thin sounding. Highs are muted, whole range is just veiled and lacks dimension. I assumed its the CX311 so I rigged up some crossover components temp style on a chunk of wood and sure enough, much more full sound. Forgive me I'm new at this and hope I'm describing things well. Few more details then my real questions. From tons of reading here and elsewhere I used a 1.5mh inductor and 15uf cap in my temp 1st order crossover becasue some ideas called for lower inductors and some higher so I thought I'd try in the middle as a starting point. The cx311 was bi-amped but not this passve Xover. Too much midrange, so I grabbed the 12uf stock cap and made the low pass portion
into a 2nd order by using it as a bypass cap. It helped but not enough. Now before continuing on and throwing money at things I'm looking for advice. I'd really like to bi-amp, so should i attempt changing internal components in my CX311, opamps and what not, or is the 24db LR crossover in such a device just not a good fit for the MMG's? Should I get a miniDSP and mic to help me learn and have more ability in tailoring the xover and other features? The miniDSP concerns me in final sound quality because at its price the A/D to D/A double conversion theoretically (and from some but not all reading) seems like a bad idea. If not using either of those how do I split my signal to bi-amp with passive xovers? I can't just use a Y-adapter on the rca right? I mean, wouldn't that split my voltage and force me to increase gain before the Y? Sorry for the wall of text I'm just inundated with info and scenarios trying to gain some experience in all this.

 

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RE: Active/passive MMG help, posted on March 30, 2017 at 17:16:42
Davey
 Yep, your CX311 crossover is not suitable to bi-amp those speakers. It has generic higher-order slopes which are totally different than the stock scheme.

If attempting bi-amp these speakers, you'll need a modifiable or dedicated active analog crossover......OR a DSP crossover of some sort that allows any slope combination.

Dave.

 

RE: Active/passive MMG help, posted on March 30, 2017 at 19:09:47
atreies
Audiophile

Posts: 5
Location: Hudson Valley, NY
Joined: March 30, 2017
 Thanks, I'll work on selling the cx311 then. I have yet to find analog active crossovers at reasonable prices that have multiple slopes. I'm not prepared to spend more than my amps on a active crossover yet. I guess I'll have to try the miniDSP to see if I can hear any loss from the multiple conversions. At least I will have a tool to provide objective data to compare to what I'm hearing. Then I can research PLLXO once I've learned enough about what crossover settings to use as these seem a good way to a quality signal. Good plan?

 

RE: Active/passive MMG help, posted on March 30, 2017 at 19:43:02
Davey
 Yes, good plan.
Check in the tweaks section and you'll see an example of PLL crossover for the MMG that I posted MANY years ago. :)

Dave.

 

RE: Active/passive MMG help, posted on March 31, 2017 at 06:55:11
BigguyinATL
Manufacturer

Posts: 3475
Joined: April 10, 2002
 Good measurement and DSP is the way to go... But Don't limit yourself to trying to match original crossovers... You can do so much better. - the beauty of DSP in that you can dial in time alignment and EG prequency response. I've not used the minidsp - but am thinking about grabbing a system to learn and play with - I don't need thier measuring stuff though - I have much better.

I started with a Behringer crossover for development - but now use DSP built into amplifiers (Crown) to do the final work,

Have fun, it's amazing what you can get out of the MMG's. If you go pro audio you can use efficient and safe SpeakOn connectors at the MMG.


"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

 

RE: Active/passive MMG help, posted on March 31, 2017 at 11:05:26
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 First thing is to extend your baffle to get a better low end. You are getting unnecessary dipole cancellation that you can avoid by adding a board to extend your baffle to the floor

Re XO
I would suggest you start with a PG crossover at speaker level as those are rather successful. The particular choices he made are detailed in his mods.

For a PLLXO you can choose PG's or Davey's XO points and build the particular simple circuit to match your power amps. Incorporate level control pots if the amps are not identical, and you can replace them with fixed resistors once you have a final setting. That would be my choice.

There are plenty of folks who managed to do miniDSP implementations without much of a degradation in sound. It is something you need to check out personally to see if the AD DA cycling is bothersome for you. If you are an analog guy and never heard a digital setup that did the job to your satisfaction at a reasonable cost, then you are likely to dislike what the AD DA cycling does.

 

RE: Active/passive MMG help, posted on March 31, 2017 at 16:05:39
atreies
Audiophile

Posts: 5
Location: Hudson Valley, NY
Joined: March 30, 2017
 Thanks, I ordered the miniDSP. I can see myself building PLLXO afterwards, just seems like fun. Thanks for all the replies, I really appreciate forums like these on all different subjects.

I was wondering about the open space beneath the speaker after reading some about enclosing the backs a little also. I'll extend it down. I already routed a 45 on the bottom edge but I'll just put another edge on the adjoining piece and it will a make a nice V accent line. What about putting wings on the sides? I am on the fence about putting a support from the top down to the feet. It doesn't need it as they are oak and very rigid but it might look good and if I made it a full wing would it reinforce the bass further? Was also juggling with the idea of a small woofer box instead of feet with the MMG frame mounted to the box. Immense amounts of reading about matching subs with MMG. I don't have room for the large dipole subs and I don't like huge amounts of bass but I do like some dynamic range. A friend has a pair of stacked 1.7i's and some expensive subs and when I listened to the system it sounded great, then I found out the subs were not turned on and after he turned them on I liked it better without the subs. But, something small since I don't have the large bass surface area of stacked 1.7i's. Obviously DIY is preferred.

 

RE: Active/passive MMG help, posted on March 31, 2017 at 21:26:11
Davey
 How about posting a side photograph that illustrates how the "sandwich" is constructed? This is an important aspect of this type of construction and I've seen numerous incorrect implementations.

Dave.

 

RE: Active/passive MMG help, posted on March 31, 2017 at 21:48:58
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 If you do use a wing then do it on only one side as two sides will create a cavity resonance.

There are quite a few guys who installed small subwoofers under their raised MMGs.See if you can find something useful that would fit in the open slot you created under the panel. There are probably plenty of 8" subs that would fit and possibly a 10 incher. Green Lantern did such a thing with a pair of sealed subs.

Another option is a W frame open baffle sub which is not as tall as an H frame with the same drivers and you are likely to be able to fit one built around 10" drivers in your open space under the panels.

 

RE: Active/passive MMG help, posted on March 31, 2017 at 23:06:26
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 GR Research has an 8" woofer designed specifically for open baffle use. You can install two in an H or W frame, and lay the frame on it's side, with the two woofers laying horizontally under the MMG's. The regular version of the OB/Dipole Sub using 12" woofers can be used on it's side as well, and the H and W frame for them is only 16" wide (or high when laid on it's side).

 

RE: Active/passive MMG help, posted on April 2, 2017 at 08:08:20
atreies
Audiophile

Posts: 5
Location: Hudson Valley, NY
Joined: March 30, 2017



Here you go. Don't mind the mess of wires and the TV I'm repairing. Extra wires are there for bi-amping and not hooked up and the very temp crossover is just laying there hooked up with a combination of speaker wire utilizing the binding posts for connections lol.

I used your design to start with Davey. Had a hell of a time finding them since they moved. Lots of references to it but all the links were dead until I found a mention somewhere of a domain switch so I just edited the link and found it. So much info on the Maggies is quite old. You'll notice the 1/4" spacers in the middle do not extend all the way to the corners. Havn't decided if I'll extend them as anywhere there is a screw pulling the halves together the spacer is present. Really just got a functional unit together so I could test and will revise the plans for the other channel and actually I'm using an MMG as a center channel also. Small room and I'm the only one in the house that cares about quality so it aims at a love seat with no beaming issues for those two listening positions.

 

RE: Active/passive MMG help, posted on April 2, 2017 at 08:37:08
Davey
 Excellent. I was just concerned you were putting the death grip on the transducer units by not utilizing a proper spacer scheme.

Well done. Carry on.

Dave.

 

RE: Active/passive MMG help, posted on April 8, 2017 at 17:55:19
atreies
Audiophile

Posts: 5
Location: Hudson Valley, NY
Joined: March 30, 2017
 My miniDSP came in and it is quite a cool item. I'm trying many different crossover settings, room EQ compensation will come later. I've been googling my butt off trying to find a thread with what worked for other ppl with MMG's. Can anyone point me int he right direction? I started with the stock settings of 680 LP and 2250 HP. Adjusted for a bit more midrange and it sounds pretty good but I'd love something to read to open up my perspective on what might be better. I'm currently at 850 2nd order LP and 1900 1st order HP. More listening needed after giving my ears a break. It's all starting to blend too much after so many changes. I have a few different amps to try as well after deciding on a crossover. Currently bi amped on a NAD t955. I have 2 x NAD C275BEEE, 1 Adcom 545, 2x HK-775 to play with, eventually bi-amping the center MMG as well.
Of note is that my right MMG was still stock and I was making comparisons all along with my wood frame MMG. Now with the miniDSP I can get an apples to apples comparison without much "temp" setup. I disconnected the stock crossover, soldered some silver clad copper wire directly from the driver to temporary binding posts just like the wood frame is setup. Non-wood MMG adjusted to stand as vertical as possible. You would have to be half deaf to not notice the difference immediately. Again I'm new to this but I would use words like more open, airy(but sweet), and detailed.

 

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