# Active MTM for LRC usage, HT application



## Wooderson (Nov 6, 2010)

Hi gang--

As you see in my sig, I've done a few diy sub builds. Now that I've got a couple of SI 18's pumping, I believe I'm set for life on bass (no, really, I am!). So now I'm turning my attention to my mains. Presently, I'm running some aging Sonus Faber Concerto's on L&R, and a Conertino as my center. I'll post a picture later. I figure if I can't beat the sound of the Faber's, then it's a bust. So, while I want to control costs (no $200 ScanSpeak drivers), I don't want to swing so low that I wind up downgrading.

The application will be strictly HT. So I only need solid bass down to 80Hz. The current plan is MTM w/ 5.25" or 6.5" woofers. After reading some reviews, I'm currently looking at the SB29RDCN ring dome tweeter.

https://www.madisoundspeakerstore.c...sb29rdcn-c000-4-neo-magnet-ring-dome-tweeter/

Still undecided on the woofers. Probably a ScanSpeak or Seas in the $70 price range (will need 6 of them). Xover freq will be somewhere between 2 and 2.5khz. Such is the beauty of active. I can play around with it ad nauseum, as long as I pick drivers with a little overlap. That's one reason I'm leaning towards 5" woofers. Since I'm MTM, I think I want to tend toward drivers with low linear distortion. Hopefully I'll be able to stay out of non-linear operating region while hitting ~110db peaks.

MiniDSP for xover/eq. Amplification is still up in the air. I'm not an "amp-ophile". As long as there's no audible noise (hum/hiss), then I'm happy. PartsExpress has some new high wattage board amps, like this.

http://www.parts-express.com/6x100w-tda7498-class-d-amplifier-board--320-307
http://www.parts-express.com/75v-20a-18800uf-rectifier-board-for-amplifiers--320-3371

I would prefer to mount the amps to the speakers, but I think it will be more cost effective to locate the 3x minidsp's, amp/amps, and power supplies all together and then route the speaker wires from there.

Also, I believe in "disposable" (via Craigslist) AVR's. I will never pay high dollars for one. Therefore, no line level outputs. Therefore, I will need to buy or create some speaker level to line level coverters. I Googled a little. Looks pretty simple to diy them. Probably with a transformer to prevent ground loops. And I'm not worried about response down to 8Hz.

I'm sick and tired of building cabinets, so I'll use a flat pack or prefab. Something like:

http://www.parts-express.com/dayton...-ft-mtm-curved-speaker-cabinet-maple--302-747

So there's the project. I will start by building just one to see if I can really beat the Fabers. Then proceed if it's a success. I don't think I'm ready for full-blown DRC, especially since this is an HT application. I'm pretty confident I can dial in a nice active xover. I have a UMIK1 and I'm pretty familiar with REW.

This will be my first shot at a full custom design (I've assembled a few kits). What am I missing or overthinking? This could easily be a multi-year project. I want to spread the expenses out, and I have a few other home projects that take priority (build a shed, ughh).

One other caveat. I am hearing impaired. Can't hear anything > 6khz. That doesn't matter much since I want them to sound nice for anyone, but I will have a bias toward the frequency range that I can hear.


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## slyons (Sep 17, 2012)

I think alot of what your looking at doing is great speakers wise & xover wise. My only issue is your idea of amplification. Those amps you linked need a power supply in addition to the board. I'm sure you saw that. Also, those are class d, is class d what you want for mids/highs? The specs look pretty bad with a THD of 1%. I would want better speaker control for mids/highs. I would put some more money & thought into your amplification stage.


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## Wooderson (Nov 6, 2010)

Thanks Sly. I agree, that amp board is a little shady looking. So what do you recommend as a minimum? How about this Dayton 12 channel amp?

http://www.parts-express.com/dayton...F_Products_Exact&utm_group=300-815_E_H200-500

With all 12 channels bridged down to 6 ($500). Or a stack of 3 of these Behringers A500's ($600-total)?

http://www.parts-express.com/behringer-a500-reference-power-amplifier-2-x-300w--248-749

Or I could go with a beefier board amp (240Wx2,4ohms,THD1%). One of the power supplies (web-link below) could drive all 3 of them, so $90*3+$70*1=$340 (power supply is rated to deliver up to 1500W total). And since I would probably never exceed 100watts, I'm sure THD will be a fraction of the 1% rating. The reviews are good, FWIW. I think I'm leaning toward this solution. Not just because it's cheap, but because it's over-powered. I can also add another 2 of the power supplies if needed and still be at $480.

http://www.parts-express.com/2x300w-tas5630-class-d-amplifier-board--320-309
http://www.parts-express.com/75v-20a-18800uf-rectifier-board-for-amplifiers--320-3371

Comments?


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## Wooderson (Nov 6, 2010)

BTW, in the name of sound quality and taking advantage of not needing sub-80Hz response, I want to go sealed. And if I really need to get a few more Hz deeper, I can EQ my way there.

So this begs the question: is there any reason to go with a 6/6.5" driver instead of something in the 5/5.25" range? 5" drivers will likely be easier to blend with the tweeter w/o trying to push the tweeter xover freq too low (so I could easily go 2.5Hkz; and also reap the benefit of higher power handling). Also, the 5" drivers will be a bit cheaper.

And another BTW, since this is HT targeted usage, I want to get good off-axis response (don't I?).

So just to throw something out there to get the ball rolling ($65 each).

https://www.madisoundspeakerstore.c...anspeak-15w/8434g00-discovery-5.25-midwoofer/


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## dougc (Dec 19, 2009)

I choose ported and a tune of 60 for my builds so that there is better sensitivity around 80hz. Also, take a look at the iNuke nu4-6000 as a good cheap amp. This and and a nu-3000 would be great for a 2-way LCR


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## fusseli (May 1, 2007)

It sounds like you have a solid plan. I agree on the amplification though, you could do better than the board amps you posted. I got an A500 for $100 used and it's been going strong for years driving a sub in my computer room. You could also save money with a couple inuke dsp amps instead of an amp and minidsps. Just a thought. The DSPs are a little different but the inukes do have crossovers


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## Wooderson (Nov 6, 2010)

Ok, I guess I'll ditch on the board amps just to play it safe and to save myself the work of mounting everything in some kind of enclosure. For the record, I think it would've worked out ok though.

I thought the general wisdom was that pro amps, especially the cheaper Behringer strain, were not "top notch" when used for full range work. I haven't seen any measurements to back that up though. Can anyone confirm/deny the allegations with hard data? Well, looks like it's pretty competent (see link below). I would definitely like to keep it driving 8ohms (which means I should prefer 4ohm woofers so that I can wire them in series??). Or if I can only find 8ohm woofers that I want to use, then maybe go with 16ohms. All of this under the assumption I would choose high power Behringer (or similar) amps. Wait, showstopper, I don't want to incur the expense (or headache) of fan modding 2 or 3 Behringer amps. It's not too hard, but no fun either. And definitely not cheap. So now I'm thinking the A500's are looking pretty good. There are some reports of reliability problems, but my two Behringer amps have given me no trouble (EP4K, iNuke6K).

http://forum.speakerplans.com/behringer-inuke-nu6000-vs-kam-kxd7200-bench-tested_topic69202.html

I still may go with the 12 channel Dayton amp, especially if I can find a detailed review of it (not likely), or maybe the AudioSource that it appears to be a clone of:

http://www.amazon.com/AudioSource-12-Channel-Audio-Distribution-Amplifier/dp/B004XT6PMQ
http://www.parts-express.com/dayton-audio-ma1260-multi-zone-12-channel-amplifier-60wpc--300-8150

Bah, for the same $600, why would I not choose 3*A500's?? 125W-RMS*2 into 8ohms should do just fine. More if I wind up with a 4ohm parallel load (all of the Seas and ScanSpeaks that are appealing to me are 8 ohm). Now, if I could only find 3 of them for $100 each :T.

If at all possible, I want to avoid porting. Smaller cabinet size, lower distortion (I believe I've read that the sound coming from the port is less than ideal and relevant up to 2x the tuning frequency), and saves me the trouble of actually adding a port. I will even go to 6.5" in order to stay sealed. Don't get me wrong, I'm a big believer in ported subs (sig). But I'm trying to use every (cheap) SQ method I know of to beat the sound of these Fabers. Or else this is a waste of time and money.

Next post, I'll edit the initial post to contain the present project proposal. I'll always update it with any more changes. At this point, my rough back of envelope estimate is 80*2+60+90+200+150+[$40 of "random bits" like speaker level to line level converter] -> $700 per speaker. I wish I were in a buying mood right now. PE has one of their MTM curved cabinets on sale for $118-shipped. That's a steal even if I have to sand and refinish it (I want to go flat all-black; don't want to see anything with the lights out except my 70" Sony screen).

http://www.parts-express.com/dayton...-ft-mtm-curved-speaker-cabinet-maple--302-747

But post-holidays and after just finishing up the SI's, I want to lie low for a while. Like I said, in order to "hide" the expense from my wife, this will be a long-haul project .


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## Wooderson (Nov 6, 2010)

$80/driver (ouch), but this puppy sure looks sweet! SEAS Prestige CA15RLY, 5.5".

https://www.madisoundspeakerstore.c...e-ca15rly-h1216-5.5-coated-paper-cone-woofer/

Sealed F3 is 115Hz, vs the 145Hz of the ScanSpeak. I'm sure I could easily Linkwitz my way down to 80Hz. Looks like it's time to do some WinISD modeling.

And off-axis response is excellent.


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## Wooderson (Nov 6, 2010)

Did some WinISD modeling tonight with the Seas driver. Looks lik ported, @ 40Hz tune, makes the most sense. After applying an LT to a sealed design to get F3 down to 80Hz, the ported specs (group delay, max-SPL, etc) all look better for ported. I'll post some screen grabs another night.

So assuming the PartsExpress rounded MTM enclosures (for now) @ 1.01ft^3, roughly reduced to 0.8ft^3 (port/driver volume), then it will hit 105dB @ 80Hz @ xmax (xmech is double xmax so it will get away with a few more dB with some non-linear distortion during peaks).


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## fusseli (May 1, 2007)

If you want to take the time, I would recommend using some more robust tools than WinISD. Try using WBCD for a starter.

http://audio.claub.net/software.html


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## RTS100x5 (Sep 12, 2009)

Hi Wooderson,

Im into my DIY speaker world deep and just wanted to highly recommend the Dayton PT2C-8 Planar for the high end .... I have 10 of these in my 5.2 system and they just are flat out out performing every ring and dome tweeter I have tried... the power/sonic quality to cost ratio is imo the best you can have until you get to the very expensive exotics.... Certainly #1 on my list in the under $300/ catagorie...they especially excel w music but are very fast and accurate w film... :T

http://www.parts-express.com/dayton-audio-pt2c-8-planar-tweeter--275-085


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