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Old 4th January 2013, 06:58 PM   #21
GM is offline GM  United States
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Quote:
Originally Posted by Siggma View Post
I found one (Dr K's MTM) on PE but there are hardly "thousands". What I'm looking for is a discussion of issues specific to the MTM crossover design. I'm not sure how to wire up the crossover.
Hmm, searching 'mtm design' on this site alone just now returned 1313 threads, which many no doubt will include sufficient XO design theory/application and actual builds to answer any basic Qs, so seems you 'hardly' did any searching: diyAudio - Search Results

Anyway, I see the folks into cone/dome designs are back from holiday, so should get plenty of design info to sift through.

GM
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Old 4th January 2013, 07:31 PM   #22
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Originally Posted by Siggma View Post
Sounds like you're trying to convince me what I have is just fine, or that if I can't make it work now I won't be able to later either. After reading the whole thing it kind of sound like "shut up and live with it". ???
Actually, this is a no on all counts. I am just trying to make sense of your argument for building new speakers. The reason you gave does not make much sense. If you want to build new speakers, great. But the reasoning you use for doing so just is not sound at all.

Quote:
I haven't done any room correction so much of what you say about correcting the room has merit. But I don't like the metal dome tweeter in the KEF speaker. It sounds brassy and hard on movie soundtracks to me. I don't like the sound of a 4" ported satellite straining to keep up. It sounds mushy and loose and has very poor bass definition.
Did it ever occur to you that the reason the tweeter sounds harsh, and the bass sounds muddy, is because you have not treated the room? Bare walls can make a speaker sound harsh, especially at higher levels. Corner resonances can be taken care of with bass traps.


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I have not been able to adjust the current system to what I consider a usable state with the surround processor crossover settings alone and I do not believe I will be able to unless and until I replace the satellites. I do not think a satellite should be ported. It's a personal opinion that I formed after I bought the KEF speakers whether ya like it or not. Without going into the rest of this, the thread is about the issues involved in designing an MTM not whether or not I like KEF tweeters or whether they are well designed or even about adjusting THX crossover alone. I'm trying to do my homework ahead of time so I have a better idea what I'm in for when I get drivers mounted and start taking measurements. Even though your comments sound a little out of place, even "KEF-ish.." I do appreciate you taking the time to write. Opinions are what makes the world of society go round, and round, and round...
Since KEF did not invent small room acoustic issues, then your comment on this is nonsense. The issues you mention are small room acoustical issues. You can build another speaker, and if you do not address the acoustics of the room, you will end up with acoustical issues that will play out differently than your current issue. You cannot build your way to getting good acoustics in your room via the speakers. You are going to have to address the room, or you will not be satisfied with the sound of any speaker you create.

Had you have just stated that you wanted to build a MTM speaker system and need advice, you would not have gotten a response from me. But your excuse for wanting to do so was so off the wall, I had to respond. I am done - good luck with your project.
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Old 4th January 2013, 07:51 PM   #23
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Siggma View Post
I do have a THX (active LFE) crossover it and it doesn't work "just fine". It
has quite a selection of crossover frequencies but they all have the same slope.
The setting each produce a fixed roll off beginning at crossover FR whereas the
satellites have a ported bottom end that rolls of sharply at 65Hz and is unloaded
below that.
It's the unloaded part that's the issue. Below 60 Hz the ported satellites are
still very much "in the mix" and dump LF energy into the room that is somewhat
amplified by the pressure zone of the corner and wall gain from the wall(s).
It sounds muddy and boomy and I doubt it's going to sound any better until
and unless I replace the ported satellites with sealed units so I can control
the LF more accurately. .
Hi,

Its very unlikely your speakers have significant output below the port tuning
frequency to "dump" energy into the room, with an 80Hz 2nd order L/R high
pass you will have a 6th order roll-off in the bass, and if anything going to
sealed boxes will increase bass below 60Hz due to the 4th order roll-off.

I'm not arguing with you wanting new speakers, fair enough. But a valid
point has been made regarding your reasoning about the bass, and that
point is the issue may not be what you describe, consequently you don't
know that you will fix it with new speakers, you are effectively hoping.

rgds, sreten.
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Last edited by sreten; 4th January 2013 at 07:54 PM.
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Old 4th January 2013, 09:34 PM   #24
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Point source and MTM often means compromise in woofer size with 5 inches being as big as I would go, more about C2C distances and Neo tweeters help a lot here.
I have used 8inch MTM but the sweet spot is very small and 3 and 4 inches being better meaning a 3-Way speaker is often better if you want bass but you can use 6 inch woofers.
THX specifications are ( or used to be) for a falling response in the treble. Perhaps the tweeter you have actually has a steep rising response?
A point 5 woofer is a bass driver installed using a first order electrical roll-off
( a Coil/Inductor) to take some of the bass duties away from the midrange Often seen in MMT speakers but I have done it many times when I wanted a cleaner midrange and more bass it takes a big coil with low DCR.
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Old 4th January 2013, 09:40 PM   #25
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I have to agree with STMixer here.
Treat the room first.
We use a very heavy and thick( 120mm) composite wall hanging on the wall immediately behind the couch and very heavy curtains on the big picture window to alleviate some of the issues in the room where we have our HT.Stereo set ups
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Old 4th January 2013, 11:53 PM   #26
Siggma is offline Siggma  United States
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Quote:
Originally Posted by sreten View Post
Hi,

The Aurum-AC130F1 is quite a nice driver suiting sealed and well
stuffed boxes. MTM 2 way is better than MTM or TMM 2.5 way.
First a question:

MTM two way vs MTM? Meaning different woofer and/or crossover vs identical woofers/sing crossover?

And an explanation:
I bought the AC-130MK2, not the F1. The F1 is a carbon fiber polypropylene cone with efficiency rated around 88 if I recall correctly. Jeff B. used it in his "Continuum" as you probably know already stating it was the lowest distortion driver he could find.

The AC-130MK2 is a carbon fiber/Kevlar cone version of the same series. It looks like the same frame casting. I suspect it uses the same motor with a different basket but that's pure conjecture. I read they recently updated the motor for these drivers post 07. I haven't seen it tested for distortion but those who have used it like it a lot. It may be as clean as the F1 but logic says not quite. The Kevlar will have a different sound than the Poly mix for sure but it's still a very nice clean mid-range woofer.
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Old 5th January 2013, 12:07 AM   #27
Siggma is offline Siggma  United States
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Quote:
Originally Posted by sreten View Post
Hi,

Designing a x/o is not a trivial matter and ideally the MTM for
the centre would be different to the other MTM's somewhat.
I agree, if I decide to actually use an MTM it will be a two way (dual identicla woofer, single tweet). But since I'm now convinced a horizontal MTM won't sound as good as a vertical MTM, regardless of crossover, I'll probably look at alternatives to the standard MTM center speaker. I flipped my C6LCR vertical yesterday and it sounds very, very different. I'm also beginning to suspect some of the hostility I'm hearing from tweeters is somewhere at or in the source. These KEF aluminum domes just bring it out more than a soft dome would. My recent testing of a Vifa BC25SC06 1" textile dome sounded a little hot and had a bit of sharpness above 6K but were not hostile. Regardless my setup has a harshness I need to track down. I just assumed the Yamaha RXV 373 was a clean DA/amplifier combination. I'm probably going to go get a separate "Music/Listening" amplifier so I can evaluate sources separate from the amp. I'll be sure and take a pair of my KEF C1's with me for reference.
Quote:
Information as to how to design a proper x/o is in the links below.

Implement some baffle step and choose your x/o points and tweeter wisely.

rgds, sreten.
Thank you. I'm sure I'll learn a great deal designing and building the satellites first. I've already pinned down most of the design and it will not require any baffle step compensation. I have a very clear design goal in mind and only time and $$$ will slow down the process. In the mean time I guess I'll work on the room. I just bought new furniture and it sound much different in the room now. But the tweeter hostility remains...
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Old 5th January 2013, 12:07 AM   #28
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MTM 2.5way is when one of the woofers is rolled off very early (LOW)
Same for MMT
Speaker configuration doesn't always tell you what the XO is

So 1 mid/woofer may have a second order low pass @ 3k ( and the tweeter a corresponding high-pass) but the other woofer gets a first order at the 6dB baffle step frequency or lower
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Old 5th January 2013, 12:17 AM   #29
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Have you considered something like this? Sumiko Audio : Sonus faber
A cross between horizontal and vertical.
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Old 5th January 2013, 12:19 AM   #30
Siggma is offline Siggma  United States
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Quote:
Originally Posted by GM View Post
Hmm, searching 'mtm design' on this site alone just now returned 1313 threads, which many no doubt will include sufficient XO design theory/application and actual builds to answer any basic Qs, so seems you 'hardly' did any searching: diyAudio - Search Results

Anyway, I see the folks into cone/dome designs are back from holiday, so should get plenty of design info to sift through.

GM
7, 810,000 results. In .51 seconds (which is a HUGE amount of time for a modern processor BTW) no less!

Click the image to open in full size.
Are you always this forgiving of newcomers questions? Sheesh. I did look and 1300 links means absolutely NOTHING. Search for "trbailey.net" and you'll see thousands of links to my site but only one or two have my picture. There are several discussions on the topic and there are many opinions but none that I could find had an actual MTM design from though to sound. If there are so many links to MTM designs why not post one, or would that destroy your reputation (with me anyway) as 48 hours of stubble?
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