Bottoming out the M&K MX-5000 THX Ultra subwoofer (1 Viewer)

[Vaughan Odendaal]

Heh, well, that's what happened this morning. I put in the Incredibles, got Chapter 23 running, and somewhere in the chapter, the subwoofer made a "plonk" sound.

I know, I know. The room size is only 2000 cubic feet, the subwoofer is positioned right behind the couch, 1 meter away from me, and it's calibrated flat. The subwoofer bottomed out at -15 from reference.

This makes me feel so much better about my SVS purchase, because I can play the same specific scene at a louder volume and it sounds like it goes deeper as well (in a much larger room).

Oh well, the headroom maximizer circuit didn't really work here as the sub completely overloaded. The funny thing is, after I heard that plonking sound from the sub, no sound emanated from it. I put my hand on the thing and there still wasn't any sound.

I hope that this subwoofer will work in a few hours. And there you go, M&K's top-end subwoofer.

--Sincerely,

 

[MikeLi]

I was just going to say... you should have got an SVS but you have already foud that out...

 

[Kenneth Harden]

I sell some of the M&K's and I think they are AWESOME music subs, but don't have enought bite for movies (*makin' some noise!*). They are not cheap subwoofers.

 

[John Menoni]

I have an M&K 350 sub. I love the M&K but I love an extreme amount of quality bass while watching movies so I'm going to be getting an SVS B12 plus 2 to add to the system. I figure the M&K can handle all the higher frequency stuff and the SVS can really drive home all the super low frequency thunder. I can't wait to see what it is going to sound like.

 

[MikeLi]

John sounds like a great idea it sounds like the M&K is the more musical of the two for you. But don't sell the SVS short. You may find you like it as well or better for music. Each has their own. I have owned some pretty good other subs I thought were good, NHT, Dyno and such until I found SVS. Your going to be in for a big surprise with that sub when you get it!!! Keep us posted.

 

[BrianWoerndle]

I can watch the Incredibles at reference level in my 1250 cu/ft room and my dual 16-46CS+s can keep up (but just barely). That scene is tough on a sub.

 

[Vaughan Odendaal]

BTW, does anyone know the tuning frequency of the M&K MX-5000 subwoofer?

--Sincerely,

 

[Edward J M]

It doesn't have one. It's a sealed subwoofer using a push/pull config.

The only thing it has is a natural system resonance frequency, below which point it will roll-off (unless extended deeper by EQ).

 

[Vaughan Odendaal]

Sorry, I made a fool of myself. I mean't what you said. So, what, in your opinion, is the natural resonance frequency of the MX-5000?

On an unrelated note; Ed, I found something interesting with my sub placement. I found that if I move the subwoofer 1/2 a meter from it's current position, much of the bloom is gone. However, I think that I lose some bass information. In my current seating position, if I stand up, the bass is tighter sounding.

As soon as I sit down, some of that tightness is gone. Now if I sit a meter from where I am sitting right now (which is 2.5 meters away from the subwoofer, the bass tightens up considerably, but it's a little "thick" at times. I hope I'm explaining myself clearly here.

Basically, the bass sounds exactly the same as if I stand up, which I assume is what it should sound like. Otherwise, besides the "thick" bass, it's incredibly tight sounding.

Sorry, if I'm dragging on here.

--Sincerely,

 

[Edward J M]

The only fools are those afraid to ask questions, or admit they don't know everything.

It is likely the M&K uses some EQ to extend the response below the natural system resonance frequency. In truth that point is of little consequence to the end user.

What you really want to know is the anechoic F3 frequency - the point (in free space) where the response has fallen 3 dB relative to the higher bass frequencies.

Knowing the slope of the roll-off is somewhat useful too, as it can help you predict how well the subwoofer will combine with any room gain to extend the in-room response. A 2nd order roll-off is the best slope to take the most advantage of any room gain.

A sealed subwoofer will roll-off naturally at 12 dB/octave (2nd order) unless a high pass filter is used to steepen that slope. High pass filters are common in commercial sealed subwoofers to help protect the woofer from over-excursion.

What you are hearing as you move around the room are standing waves creating peaks and nulls. These alter the FR of the subwoofer at that particular listening position, so you hear this as a difference in the bass SQ.

The best way to lessen this effect is with bass traps in all the corners. They will absorb bass and reduce the amount of standing waves in the room, and your FR will be more uniform at more locations. After bass trapping, you can add a PEQ to fine tune things.

 

[Vaughan Odendaal]

I was just wondering as a matter of interest what the low frequency extension was of the big M&K 5000.

I just wanted to ask you, if I stand up in my seating position and don't detect any difference in bass, is that good or bad?

Dankie. Thank you for your advice, Ed.

--Sincerely,

 

[Edward J M]

The less variation in bass output and SQ you notice as you move about the room, the better.

 

[Brian L]

Vaughan,

Drop M&K an e-mail. In my experience, you will get a quick answer. Here is their e-mail:

[email protected]

I recently was thinking of buying one of their subs, and dropped them a note with a few questions on a Saturday afternoon. I got an answer back in about 10 minutes, and ended up passing e-mails back and forth for the rest of the day with one of their top tech guys ; Barry Ober.

He was featured in an interview as part of a M&K review at Secrets. If you want to know something about your sub, I bet he will answer it, and probably give you a few other kernels of wisdom that you did not ask for, too. A great guy to converse with.

Good Luck,

Brian

 

[Vaughan Odendaal]

Thanks Brian!

--Sincerely,

 

[Arthur S]

Back in 1994 Don Keele tested the 5000 sub and satellites.

I could not find in the review if he tested the sub outdoors or indoors. In any case, the most revealing FR data is this: "... peak output starts out strongly, 106db at 20Hz, rises to 113db at 32 HZ, hits 117db at 40Hz, and reaches a maximum of 122db at 80Hz. Below 40 Hz the output exceeds that of all tested subwoofers except one...."

So, I think it would be safe to say this is a very powerful subwoofer. But the FR (like that of other M&K) rolls off pretty badly below 40 HZ.

If you want to see the review and FR graphs, go to the M&K web site and find the reviews. The entire Keele review is there. I am sure Ed could easily digest it and make some useful statements.

 

[Vaughan Odendaal]

Thanks Arthur! I'll look at the review. I would very much like to hear Ed's thoughts on the test measurements in the review if it's not too much trouble.

Hope I'm not becoming a nuisance.

--Sincerely,

 

[Vaughan Odendaal]

Guys, I have a question for you. My manager tells me (he's been in the audio industry for the better part of 40 years), and he tells me that you cannot measure the tonal characteristics of a sub (or of speakers).

Is that true? Can you not measure the tonal sound of subwoofers with equipment?

--Sincerely,

 

[Edward J M]

Keele shows the 5000 flat to about 35 Hz, and -8 dB at 20 Hz. As predicted, the roll-of slope is 12 dB/octave, indicating no additional high pass filter.

His distortion meausurements were obtained in-room at 0.25 meters with the mic on the ground plane and referenced with drive voltages (typical of the TEF measurement system). This would be virtually impossible to translate into outdoor measurements in 1/2 space at 2 meters - something Keele adopted later on in his review career.

Likewise the peak SPL figures were obtain in-room, and were padded with what Keele refers to as common corrections for room gain: 8 dB @ 20 Hz, 4.5 dB @ 50 Hz, and 2 dB @ 100 Hz. Again, translating this into how the subwoofer would perform on the output compression sweeps at 2 meters in 1/2 space is not possible.

Keele's reviews were always technically ambitious and he was a pioneer and industry leader in subwoofer testing. He eventually adopted the practice of measuring at 2 meters in 1/2 space but IIRC sometimes normalized the data to 1 meter by adding 6 dB, and then also added common room gain numbers on top of that.

I prefer to just test everything at 2 meters in 1/2 space and let the chips fall where they may. It certainly makes things cleaner and easier for comparisons.

With respect to indoor performance, measuring actual peak SPL the subwoofer can generate on source material in a mid-size room without obvious signs of audible distress seems to give a good indication of its real world output capabilities. And there is always a good correlation between the objective 1/2 space performance and the subjective in-room performance.

 

[Vaughan Odendaal]

And there is always a good correlation between the objective 1/2 space performance and the subjective in-room performance.

That's what I've found as well, but my manager tells me that I'm talking crap. He tells me that there is no tonal measurement for speakers or subwoofers.

What are your thoughts?

--Sincerely,

 

[Vaughan Odendaal]

Ed, can't you just, I don't know, borrow an M&K MX-5000 and just review it's performance?

--Sincerely,