Tech evaluation of the Iron Driver Loudspeakers

[mzisserson]

Re: Tech evaluation of the Iron Driver Loudspeakers

Wow, great speakers, great measurements and great info (I was wondering about how those FM curves factored in recently).

Going back to the "Iron Driver", I had asked for opinions on the 830656 a short while back and the feedback was a fairly cohesive "meh"...not great, not poor...it's decent and easy to work with. Seeing the various implementations in their final forms, is that still everyone's opinion of the 830656?

Thanks.

Like any driver when used well it will yield good results. I would take the MCM buyout 5.25" over it right now. Lower distortion through the mid-range. And there are other drivers that may work better in more specific applications. It is not a bad driver at all, there are few as flat out easy to work with, but what you give up for something so easy to work with is resolution and dynamic capability.

[rpb]

Re: Tech evaluation of the Iron Driver Loudspeakers

Wow, great speakers, great measurements and great info (I was wondering about how those FM curves factored in recently).

Going back to the "Iron Driver", I had asked for opinions on the 830656 a short while back and the feedback was a fairly cohesive "meh"...not great, not poor...it's decent and easy to work with. Seeing the various implementations in their final forms, is that still everyone's opinion of the 830656?

Thanks.

It's a long ways from being the equal to an 831735, which you have. Even at low SPL, or even used as a mid.

[mzisserson]

Re: Tech evaluation of the Iron Driver Loudspeakers

It appears that Ryan pretty much saved me from posting, as he already covered most of what would have been my main points. So, I merely clarify some of it in my own words.

First, of all let's take a look at those FM curves, and reference the line in the 80-90 Phons range. Surely no one here would ever advocate putting a 10-15 dB dip in their speaker's frequency response at 4khz, or add a 10dB peak at 10khz, or heaven forbid a boost of 30dB or more in the bass (however, I believe there are some car stereo around here that do just that ;-). So, that means no one would actually advocate designing to these curves, and if they did their speakers would not sound very good to anyone, them included.

The fact is, these curves have nothing whatsoever to do with speaker design (with a very small exception, which I will comment on at the end), they have to do with our natural hearing sensitivity for what is called "equal loudness" vs frequency vs SPL. In other words the bass must be 30dB louder than the upper midrange before we interpret that sound as equally loud, and so on. But what seems to get lost in the translation is in the fact that we hear everything according to these curves - people talking to us, a baby crying, a jazz ensemble playing, a full orchestra, a jet taking off, etc. These curves are already factored in to how we hear everything in nature.

When you listen to Joni Mitchell singing to an acoustic guitar live you are perceiving according to these curves already. So, if this session was recorded and played back for you would it make any sense to apply these curves to it again? If you do, the playback will certainly sound nothing at all like the original performance. However, if it is played back reproduced as closely as possible to the original, then it will sound as closely as possible to the original to your ears - because, as I said, these curves are already present in the way you are hearing everything anyway. You don't want all sounds to be equally loud, and that's what these curves are about in the first place.

Now, I am not really talking about whether a speaker will sound best if it is designed "flat" or not, because someone will first need to define what "flat" even means. "Flat" is a very cloudy term to begin with - flat on what axis? there are how many of them now? Flat at what distance? Flat in what room, an anechoic chamber, or your living room? and it goes on and on. It is because of these reasons that small changes in frequency response, what we might call "voicing", becomes an important part of the design process. And I am sure this is really what you are talking about and not about designing to FM curves, right?

My Continuum, for example, has some very specific and intentional deviations from what someone might call flat (even though they all fall within +/- 2.5db across the board), but most everyone comments on how natually voiced and balanced they sound, especially with voices. This because these deviations in the on-axis response are specific to how the off-axis response combines with it and how the room tends to impact the response, etc., (there's really a lot of thought and research that went into this) so in the end, the perceived sound seems "correct" to our ear.

I suspect that when all of the semantics get ironed out we will be much closer on all of this than you thought.

Jeff B.

We are there. It was an odd question, Jeff, if you look at the measurements there certainly was no 10-20dB dips anywhere. But slight voiced yields a preferred result. If you use the FM curves as a tool for design and understand HOW we hear, you can better "voice" to yield a preferred sound. To say they have nothing to do with loudsepeaker design is like saying torque curve has nothing to do with designing a transmission. I guess the semantics now become are you coloring the sound and not preserving the input signal, or are your right to do so because you are creating a more listenable, hence enjoyable speaker. May be preference at the end of the day, but in the middle of summer I do not go without sunglasses because what I see is more "pure to the the signal".

[Jeff B.]

Re: Tech evaluation of the Iron Driver Loudspeakers

Well I know little bit about both speaker design and transmission design, and trust me torque is a real element in transmission design, the FM curves are about physiology (oddly, something I have a degree in) and not really about speaker design at all. Speaker design, if not about preserving the input signal, then it is at least about creating a listening experience that tends toward natural sounding. The FM curves can't be used to get you there. You may decide to design in a small dip at 4khz because your hearing is very sensitive in this region. That may be related, but it's not really based so much on the equal loudness curves.

I mentioned above that there was an exception, but forgot to clarify that. If you tend to listen to music at fairly low levels, but want it to sound relatively balanced then you might want to apply a form of the FM curve to the response to provide that balance. However, at a higher level this same adjustment will sound all wrong to you. This was the function of the old "loudness" button on receivers from the 70's if you remember them.

Jeff

We are there. It was an odd question, Jeff, if you look at the measurements there certainly was no 10-20dB dips anywhere. But slight voiced yields a preferred result. If you use the FM curves as a tool for design and understand HOW we hear, you can better "voice" to yield a preferred sound. To say they have nothing to do with loudsepeaker design is like saying torque curve has nothing to do with designing a transmission. I guess the semantics now become are you coloring the sound and not preserving the input signal, or are your right to do so because you are creating a more listenable, hence enjoyable speaker. May be preference at the end of the day, but in the middle of summer I do not go without sunglasses because what I see is more "pure to the the signal".

[mzisserson]

Re: Tech evaluation of the Iron Driver Loudspeakers

This was the function of the old "loudness" button on receivers from the 70's if you remember them.

Jeff

...They need to bring them back.:(

[r-carpenter]

Re: Tech evaluation of the Iron Driver Loudspeakers

Thanks. Which document is this? I have the book Testing Loudspeakers by D'Appolito. And I have a copy of his Audio Express article. Where can I read about this? Thanks.

Testing Loudspeaker, not Measuring. My mistake.
Anyway, page 47." Anomalous impedance data. "

[ryanbouma]

Re: Tech evaluation of the Iron Driver Loudspeakers

Perfect. Thanks.

[Pete Basel]

Re: Tech evaluation of the Iron Driver Loudspeakers

The difference between microphones and ears is that the ear has an outer ear
causing the frequency response to be dependent on direction. If you move a
center placed source to right and left as with a stereo pair the "ear system"
has a different frequency response as compared to center placed. Obviously,
there is no perfect solution but some deviation from flat can help in providing
a much better "phantom" center image. Consider that often, most of the time,
the main source is center placed so we want that to be as close to correct as
possible. I discussed this probably over 10 years ago on the Bass List.

I started a thread on the Stereophile forum named something like "When Bad
is Good" pointing out that sometimes flaws land in the right place to make a
piece sound better than it should. The Dynaco A-25 is a good example in that
they can sound amazingly good, yet they have probably more than a 6 dB dip
around 3 kHz. There were curves over at AudioKarma let me see if I can find
them.
Edit: Here it is:
http://www.audiokarma.org/forums/sho...ghlight=dynaco

We have some excellent, modern large speakers here and my 21 year old son often
listens with me. I finished restoring a pair of A-25s set them up and gave them
a listen with my son, and we just looked at each other thinking these sound far
too good for what they are. He is into music, not so much engineering, but he
does have an excellent ear. He used to sit on my lap when he was about 2.5 years
old and listen when I did final testing of some designs. He's been a critical listener
for a long time!

I attached the curves from AK below, hope that is OK, first by Zilch and second by Jackgiff:

[Pete Schumacher]

Re: Tech evaluation of the Iron Driver Loudspeakers

I can see where Mike has a point. If you "voice" a speaker for a particular SPL, then you'd probably be altering the response to provide the sound you expect instead of what you measure.

For example, you build a very small set of bookshelves designed to be played at 2 meters as background music with levels below 75dB. In such a case, you may opt for a quite a different overall shape to the response due to the physiology of the ear. In those cases, you'd probably be cranking up the bass knob (loudness button) anyway, so why not build it into the speaker if you never intend to turn it up any louder?

But really, who voices a speaker system at those quiet levels?

[johnnyrichards]

Re: Tech evaluation of the Iron Driver Loudspeakers

Boom boom shakalakaboom boom...

FM curves are why there is no such thing as a speaker that sounds "right" at all volume levels.

Of course, if you spend enough or have a big enough emotional investment in a design you can fool yourself into thinking you have discovered a passive solution but that is just lying to yourself, and your customers.

So voice at low levels (as stupid as Pete seems to think that is) or high levels (as stupid as my ear doctor seems to think that is), but you can really only idealize to one level - the rest is a compromise so why not just claim that out front? "These are designed for low level listening" or "these are designed for high level listening" why resort to provable lies like "these sound right at all volumes"?

Besides, the soundguy has already included the FM curve on the original master, so that disparity is included on even the shittiest recording.

[morris]

Re: Tech evaluation of the Iron Driver Loudspeakers

I mentioned above that there was an exception, but forgot to clarify that. If you tend to listen to music at fairly low levels, but want it to sound relatively balanced then you might want to apply a form of the FM curve to the response to provide that balance. However, at a higher level this same adjustment will sound all wrong to you. This was the function of the old "loudness" button on receivers from the 70's if you remember them.

Jeff

IMO this explains why I tend to boost the bass frequencies and attenuate 3-5 khz of my computer speakers when listening at low levels but I dial it to flat when I want it loud.
Very informative post gentlemen....EQ is our friend!!

[Jeff B.]

Re: Tech evaluation of the Iron Driver Loudspeakers

Don't you voice your crossovers using music you typically like to listen to, at the distance you will be listening at, in the room you will be sitting in, and at the volume your normally play it at? I know that's the way I do it. When I do, all of the influences of those things are factored into the outcome automatically.

Boom boom shakalakaboom boom...

FM curves are why there is no such thing as a speaker that sounds "right" at all volume levels.

Of course, if you spend enough or have a big enough emotional investment in a design you can fool yourself into thinking you have discovered a passive solution but that is just lying to yourself, and your customers.

So voice at low levels (as stupid as Pete seems to think that is) or high levels (as stupid as my ear doctor seems to think that is), but you can really only idealize to one level - the rest is a compromise so why not just claim that out front? "These are designed for low level listening" or "these are designed for high level listening" why resort to provable lies like "these sound right at all volumes"?

Besides, the soundguy has already included the FM curve on the original master, so that disparity is included on even the shittiest recording.

[johnnyrichards]

Re: Tech evaluation of the Iron Driver Loudspeakers

Don't you voice your crossovers using music you typically like to listen to, at the distance you will be listening at, in the room you will be sitting in, and at the volume your normally play it at? I know that's the way I do it. When I do, all of the influences of those things are factored into the outcome automatically.

Actually, what I do is a lot of listening at different positions including setting the speaker outside while I sit on the deck and have a couple of beers. I usually listen at somewhat lower volumes, so very often I find myself reaching for the bass knob to restore the fullness, I rarely design that passively since if I do listen loudly I have sometimes come across excursion issues with that approach.

The reason I use the above approach is because I rarely sit in the sweet spot and just listen. I don't know if I even have a sweet spot to be completely honest. So usually I just end up designing towards a mathematical model and using the EQ or other approaches to "fix" the rooms influence. We have heavy furniture, thick carpet, and lots of heavy drapes in the living room for example.

But really, if our hearing changes with the volume of the source then there is really only one point at which a speaker will sound balanced - unless the FM curves are incorrect and I am willing to admit that possibility.

[GranteedEV]

Re: Tech evaluation of the Iron Driver Loudspeakers

As far as equal loudness curves, I think there's gotta be a better way of approaching the problem than passively designing it into the speaker. For a living room setup, get a modern receiver or processor with Dynamic EQ processing.

[Pete Basel]

Re: Tech evaluation of the Iron Driver Loudspeakers

You voice it for the maximum listening level that it is capable of handling, or expected in use, and then use volume dependent loudness compensation for lower levels. Or live with the inaccuracy of listening at a lower level as most do.