Tech evaluation of the Iron Driver Loudspeakers

[Deward Hastings]

Re: Tech evaluation of the Iron Driver Loudspeakers

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.

One doesn't use "a form of the FM curve", one uses a curve derived from the *difference* between the FM curve at performance level and the FM curve at listening level. That maintains the perceived "balance" when listening . . . sort of. It won't necessarily sound "right", but it will sound "better" . . .

[kenny_k]

Re: Tech evaluation of the Iron Driver Loudspeakers

I use live performances (cd, album, tape...etc) of performers I have experienced live. This is reliable for me. I can not predict if a recording is acurate or not that I am not familiar with. Voicing a speaker is relative to the material and preconceptions in use for the evaluation. What I hear is what I alone hear.

[carlspeak]

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:
What vintage A-25's were tested? Below is my on axis test of an early SS version. No evidence of a dip at 4 kHz. I wonder if the AK test was done a the later Seas version.

[Pete Basel]

Re: Tech evaluation of the Iron Driver Loudspeakers

Hi Carl, I'd expect that they are the SEAS version, as far as I know the SEAS
version was the one produced over the life of the speaker. The SCAN version
was (perhaps very) early production, not sure, anyone have an estimate for
the number of SCAN versions made?

[boroson]

Re: Tech evaluation of the Iron Driver Loudspeakers

This is the first time either Biff or I entered a DIY event, I've built about three different speakers of my own design and Biff has a great set of MTM's that Dennis Murphy helped with. That being said, was our speaker blown away by the others? I know we had a problem with the high end being too muted which led to a too laid back sound, but in my room they sounded good to us. We did not pick up on the decreased tweeter level either in listening or measuring (we aren't that good with measurement). I guess I want to know if we are "on track' with this speaker building business. Any useful comments would certainly help us.

[r-carpenter]

Re: Tech evaluation of the Iron Driver Loudspeakers

This is the first time either Biff or I entered a DIY event, I've built about three different speakers of my own design and Biff has a great set of MTM's that Dennis Murphy helped with. That being said, was our speaker blown away by the others? I know we had a problem with the high end being too muted which led to a too laid back sound, but in my room they sounded good to us. We did not pick up on the decreased tweeter level either in listening or measuring (we aren't that good with measurement). I guess I want to know if we are "on track' with this speaker building business. Any useful comments would certainly help us.

The preferences often have to do with habits too. If you are use to another speaker with decreased tweeter output, then the ear/brain adjusts and compensates. Important aspect is also room/speaker interaction. In a fairly bright room, decreased tweeter output may be beneficial. Your speaker was not "blown away" by others.

[craigk]

Re: Tech evaluation of the Iron Driver Loudspeakers

one other thing to take into consideration is the equipment being used. maybe different cd player, amp, and yes the "c" word, cables, all could have contributed to the laid back top end. that is why the pro reviewers keep around so many different types of eqiupment to review speakers with. do not give up. it is always good to get a second or even third pair of ears to listen to a project. after listening to something for several weeks, or monthes it is normal to start hearing what you "think" they should sound like, and not what the speakers actually sound like. sometimes it is good to just take a break for a week or so and not listen to the speakers you are working on, and come back with fresh ears.

good luck, craig

[jclin4]

Re: Tech evaluation of the Iron Driver Loudspeakers

It's interesting that several of the speakers seem to have subjective comments of top end rolled off or too laid back and that the XT25 or variants appeared to be the tweeter of choice for many of the entries. (Did anyone use the XT19? -- maybe Mike Z, but I can't be sure).

I wonder if the directivity of the XT25 came into play. I wasn't there for the Iron Driver, but I have been in Roman's shop for other DIY events. It is a large room and the speakers are generally placed pretty far apart (at least compared to a room in one's own home). Could it be possible that the listening axes of the judges were generally greater than those of the designers at voice-time?

[boroson]

Re: Tech evaluation of the Iron Driver Loudspeakers

Interesting point. My room is 14' wide and the speakers were set about 7' apart and 8-9' in front of us. When we took our measurements, I attempted to use the method used by LouC, placing the mic slightly off axis from the tweeter. If these were not the conditions at the venue, then the listeners would be way off axis with the resulting fall off of the upper frequencies. I'm not complaining since this set-up was the same for all. Just trying to understand. We used the XT25 for our design. And again, I am sensitive to an overly bright sound and I tend prefer a warm sound.

[r-carpenter]

Re: Tech evaluation of the Iron Driver Loudspeakers

There are few subjective/objective factors at play here. For starters, there's always a reference point. That reference point is an unamplified performance. Ultimately the loudspeaker should reproduce that faithfully or as close as possible.Then, the room and direct/reflected signal ratio comes in to play together with the speaker and the recording.
Just from the measured response it looks like there was a mistake with the SPL of the tweeter output. The tweeter FR appears to be flat and well controlled, but lower in level then the rest of the speaker. Could that play in to your dislike for a bright sound? Could it be a bright recording/s used for the final tuning? Probably a multitude of factors. In the end, in the room where the speaker competed, these irregularities did not play to it's favor, compare to other loudspeakers. This of cause does not negate the fact that in your room, combine response at the listening spot may be quite pleasant.

[boroson]

Re: Tech evaluation of the Iron Driver Loudspeakers

I agree that we made a mistake with our tweeter level, it's aparent in the measurements above. I'll measure the durn things when I get them back and see if I see this dip. Come to think of it, I dont recall doing a system FR test, we just tweaked the xover by ear. I'll bring the system into balance and give them more listening time.

Thanks for giving your time to this event, in planning, measuring, packing and unpacking as well as answering all of the questions I've asked. The Iron Driver contest was very interesting for me, I had fun, made a new friend,Biff, developed new skills, and learned a lot.

[boroson]

Re: Tech evaluation of the Iron Driver Loudspeakers

I agree that we made a mistake with our tweeter level, it's aparent in the measurements above. I'll measure the durn things when I get them back and see if I see this dip. Come to think of it, I dont recall doing a system FR test, we just tweaked the xover by ear. I'll bring the system into balance and give them more listening time.

Thanks for giving your time to this event, in planning, measuring, packing and unpacking as well as answering all of the questions I've asked. The Iron Driver contest was very interesting for me, I had fun, made a new friend,Biff, developed new skills, and learned a lot.

[r-carpenter]

Re: Tech evaluation of the Iron Driver Loudspeakers

double post
I think Iron Driver was a very interesting event.
My observation is that with availability of measuring gear and modeling software like PCD, over all level of design went up quite a bit in a last 10 years or so. I've been learning a great deal lately myself.