|
|
Joined:
January 2005
Posts: 4903
Location: Phoenix AZ | Originally posted by Tony Calman:
Would be nice to share the "Swept Sin Wave Response" - tried to take mine (7/12) to an uploadable size but you can't read it. I scanned it at 300dpi, then in photoshop converted to 72dpi and resized to 8 inch width. The problem is that the resulting jpg is still too big for the member gallery to accept. That's why I host everything at roundbackguitar forum.com.
If anyone wants to scan their vibrometer print outs and email them to me I'd be happy to host them for you and you can just link to them in RBGF the same way I do and post the photo in your post.
Dave |
|
| |
|
Joined:
January 2005
Posts: 4903
Location: Phoenix AZ | |
|
| |
|
Joined:
August 2004
Posts: 709
Location: Germany | Well, I have a guess of what they are doing to gain the response spectrum. I try to explain it with my limited English skills, so if you don’t understand it, it’s my fault. Probably Darren would be the right person to do that but I’m not sure if he is participating on this board.
They stimulate the sound system of the guitar (mainly soundboard and corpus) with a constant acoustic signal (sinus waveform) in the range of 20 Hz to 20,000 Hz. It’s very important to keep this signal very constant. For instance, stimulation can be done by a loudspeaker.
Then they measure how the guitar’s sound system responds to this simulation. There are different ways to do that, I think they put a piezoelectric pressure pickup or focus a laser vibrometer on the top. You can see the result on the response plot. Obviously you have a weak response at lower and higher frequencies and a relatively constant response in the middle of the spectrum. And you can identify two zones where you get a very heavy response. These peaks are called the resonance frequencies of the guitar’s sound system. You know these special frequencies very well if you play your guitar on stage. The sound properties of guitar, amplifier(s) and environment can lead to feedback – the resonance frequency of the entire sound system. The two resonance frequencies of the OFC guitar are not necessarily the feedback frequencies as the response plot only can examine the isolated guitar.
The guys at the engineering department now identify the lowest resonance frequency and determine this frequency to be very characteristic for this special guitar. In case of #8 it’s about 91 Hz, in case of #7 it’s about 93 Hz. In the past (I think up to serial# 10,000) they suffixed this number to the serial #. In my opinion this has nothing to do with the sound impression you get from a guitar (the complete spectrum is important for the sound). From technical point of view it’s very characteristic for a guitar, from musical point of view it’s totally irrelevant. Nice to know the number but not only this frequency determines how your guitar sounds (not to mention if you like the sound).
Please pay attention how to read the plot. At the top there is a higher signal strength but a lower dB value (as the dB value is negative). That means the lower the dB value the higher is the response signal. #7 has 35 dB at 93 Hz, #8 has 41 dB at 91 Hz, so #7 has a better response at his resonance frequency. But Dave, there is no need to be unsatisfied with your guitar, I’m pretty sure you won’t hear a significant difference between #7 and #8 (assuming they have identical strings). By the way, “dB” means “decibel” and is just a special unit of measurement for very large or small ratios. Simply forget about it.
Now don’t waste your time with these plots anymore. Take your guitars and play them – that’s a better long-time investment.
Karl |
|
| |
|
Joined:
January 2005
Posts: 4903
Location: Phoenix AZ | Great reply (and totally understandable). Thanks so much Karl. You're right what really matters is 1) do you like the sound and 2) does playing this guitar make you happy.
In the case of #8 both answers are YES !!!!!
I ditched the original strings this morning (yes it IS only 6:01 AM, but what the hell). I don't know what kind of strings they were but I put on some Dean Markley PBs and it sounds wonderful.
Thanks again Al. PS - Yes I found the LP.
Dave |
|
| |
|
Joined:
August 2004
Posts: 709
Location: Germany | Well, I said we should not waste our time with the plots. Nevertheless, it would be nice to have some of the plots posted here. I'm interested to see if there are any significant differences between the standard neck and the 3 wide neck guitars. Surely the neck has some influence on the signal response behavior of the guitar but I would assume we can not identify it on the plots. But that's just a guess. I'm curious about it.
I will defintely contribute the plot of #10. Just can't say when.
Karl |
|
| |
|
Joined:
August 2003
Posts: 4619
Location: SoCal | Karl, thanks...
For the 1% who don't know, # 7 is std neck, Dave's # 8 is the 1st out of what is being called the wide necks.
What I don't understand is the same measurements create such a wide difference.
#7 has 158.8656HZ v. #8 with 91.4176HZ for A.
# 7 has 93.0101Hz v. # 8 has 167.3131Hz for B.
158.8656Hz v. 91.4176hZ for A is a big difference as is # 7's 93.0101Hz v. # 8's 167.3131Hz.
These numbers were taken off of the machine generated printouts - # 7 measured 5/23/07 and # 8 measured 6/12/07. If this was a radar gun, the speeding ticket would would probably be dismissed. My defense would be concerning calibration.
Except for subtle differences in the hand work, both are a/e, top, bowl, bridge placement, strings, etc.
I would have expected closer to:
#7 has 158.8656HZ v. #8 with 167.3131Hz for A.
#7 has 93.0101Hz v. #8 with 91.4176HZ for B.
YET, this is not the rating...inquisitive minds want to know
:eek: :D |
|
| |
|
Joined:
January 2005
Posts: 4903
Location: Phoenix AZ | I'll start a new thread with the plots that people send me. It'll be interesting to compare.
I'll play around in photoshop and I think I can stack plots on top of each other for comparison.
If anyone wants to participate, just scan your plot at 300 dpi and email it to me.
Dave |
|
| |
|
Joined:
January 2005
Posts: 4903
Location: Phoenix AZ | I'll start a new thread with the plots that people send me. It'll be interesting to compare.
I'll play around in photoshop and I think I can stack plots on top of each other for comparison.
If anyone wants to participate, just scan your plot at 300 dpi and email it to me.
Dave |
|
| |
|
Joined:
November 2003
Posts: 11039
Location: Earth·SolarSystem·LocalInterstellarCloud·Local Bub | "Neck Mass" could explain the subtle differences in the similar numbers. I was thinking there was either a typo in the "A"/'B" or the test was run differently for each guitar.... |
|
| |
|
Joined:
August 2004
Posts: 709
Location: Germany | Tony,
I'm quite sure that A and B means nothing special. It's just how the engineer at the factory randomly assigned the two frequencies to the letters. Indeed, what you have expected belongs together:
Lower resonance frequency of #7 is (rounded) 93 Hz and of #8 is 91 Hz.
Higher resonance frequency of #7 is 159 Hz and of #8 is 167 Hz.
What does that mean to us? Well nothing when it comes to the sound of the guitar. But it is a fingerprint unique for the specific guitar. You will recognize your guitar when label and serial# are lost. Just like a fingerprint is unique for a specific person. But it tells us nothing if this person is a good or a bad guy.
Karl |
|
| |
|
Joined:
October 2005
Posts: 5331
Location: Cicero, NY | A stupid question - when we discuss plotting differences, I'm assuming that would result in differences in sustain and/or volume. Would these plot differences also equate to tone differences? |
|
| |
|
Joined:
August 2004
Posts: 709
Location: Germany | My theory is that the differences in resonance frequencies don't contribute to a perceivable sound difference. Dave's approach seems to be the way to success. Stack two plots on top of one another. The more the two curves differ the more you will perceive a tone difference. Will we ever have the chance to hear the differences of all OFC guitars? I would assume not. But maybe some.
Karl |
|
| |
|
Joined:
February 2005
Posts: 212
Location: France | As far as I know:
The lowest resonance frequency is called the Helmholtz frequency, it is caused by the holes on the top of the guitar and the body volume.
Blow in an empty bottle and what you hear is the Helmholtz frequency. Add water in the bottle, the frequency changes and you hear a different sound.
There are a lot of other cavity frequencies in a guitar, the helmholtz is always the lowest.
The helmholtz frequency contributes to spread the acoustic energy specifically in the bass notes. I'm not sure it is possible to hear a difference between 91Hz and 93Hz. But I played a 89Hz Adamas and a 100Hz and I think the difference was noticeable. The lowest the hemholtz frequency is the more the guitar will be "boomy" with strong bass.
Tom |
|
| |
|
Joined:
November 2003
Posts: 11039
Location: Earth·SolarSystem·LocalInterstellarCloud·Local Bub | I don't think you can draw any hard conclusions about the "tone" quality, if each guitar has a slightly different unique fq response at a specified db given very similarly constructed guitars.
In "realtime" playing... this means little. |
|
| |
|
Joined:
December 2001
Posts: 7236
Location: The Great Pacific Northwest | Actually the numbers are not a "signature" as they will change depending on temperature, humidity and how much use the guitar gets. Also, it's not a case of higher or lower numbers are better.
When they started doing this, they found that several guitars that "sounded great" had something in common. That was that the lower resonant frequency, which is just that, the lowest frequency that makes the top resonate the most (average across the whole surface) was in the low 90's.
I would think there is more to it, but basically that's it in a a nutshell. If your guitars resonant freq is in the low 90's it's in company with what are consider the best sounding guitars made. |
|
| |
|
Joined:
August 2004
Posts: 709
Location: Germany | I'm looking forward to the OFC slothead reunion when we are going to compare the 2007 to the 2037 plots.
Karl |
|
| |
|
Joined:
August 2003
Posts: 430
Location: Lebanon, TN | Simple statements about the QC issues.
1. Ovation launches the Custom Shop as a deliberate market strategy to pull the brand upscale (and we assume improve unit profitability).
2. Al orders one special batch of a number of significant Custom orders for the biggest fans and supporters of the roundback in the world.
3. 25% of guitars supplied to date (2/8) have potentially QC fixable flaws
IMHO the factory HAS to take responsibility for these quality challenges if they intend to bear fruit from this market strategy. Will it stop me ordering or requesting paid repair/service...No, but accountability in all we do guys. |
|
| |
|
Joined:
December 2001
Posts: 10583
Location: NJ | Originally posted by Stuart Miller:
and supporters of the roundback in the world.
3. 25% of guitars supplied to date (2/8) have potentially QC fixable flaws
. I really HATE when people don't know yet post as if they do.
tell me stuart how many guitars have been delivered.
I really would love to konw.
BTW you are WRONG |
|
| |
|
Joined:
August 2003
Posts: 430
Location: Lebanon, TN | With the 'heat' in that response I apologize for any part of my comments that provoked your ire Al.
Nothing more to add. |
|
| |
|
Joined:
January 2005
Posts: 4903
Location: Phoenix AZ | Everything that needs to be said on this topic has been said. Al, since I’m the one who started this thread, can I ask you to close this? In the old days I could have deleted it. If you don’t think that’s the right thing to do, so be it. The intended purpose of this thread is long over and frankly a lot of peripheral comments don’t add much to the discussion. If you guys want to keep posting on this go ahead. But I’m over it.
I do however want to close this with some comments about myself, not my guitar. It would be wrong for you to think that I am a disgruntled buyer or a spiteful person who feels they have been wronged in some way. Nothing could be farther from the truth. I have had 48 hours to mull over this and put things in perspective. My initial posts on this topic were very emotional and pointed. But I stand behind 95% of it. There is a real problem here and it needs to be addressed. ‘Nuf said already on that topic.
The part I regret saying is that Ovation could not build guitars of the same quality as Martin, Collings and Lowden. That sounds like a criticism of the luthiers who build our instruments and it was wrong to say. These are highly skilled builders, among the best in the business. There are many, many examples of their fine work and the OFC guitar is the shiny star of the whole damn lot. What I should have said is that I don’t believe Ovation has the QA systems in place to do it on a consistent basis. The good thing is that it should be possible to improve QA given good work procedures, proper standards, training, and allowing sufficient time for the QA people to do the job.
I also feel terrible for putting Al in such a bad spot over this. You think we are frustrated when some issue comes up, how do you think HE must feel? To us he is the face of Ovation. To Ovation he is the face of the customers. It’s a can’t win situation and I truly feel bad how it was handled in this case. Lesson learned.
I’m not going to stop buying Ovations, although I might think twice about new ones. But if the odd interesting guitar comes up on the use market I could certainly be interested. Yes, I did take down OvationGallery.com but not to make any “statement” or anything. It just seemed awkward to be talking out of both sides of my mouth. On one site I am criticizing Ovation about their lack of QA and on the other site I’m praising them as gods gift to guitardom. Just did not feel right. The site will be back. Maybe it’s time to do a make over, new layout, new colors, new features. Any site that stays stagnant for too long gets boring (hint, hint).
But what I really wanted to respond to were the many, many emails and PMs I received yesterday. WOW, I hadn’t gotten that many emails since I cracked a free password to BustyBabes.com. Many of the messages were sympathetic, some thanked me for bringing up points that had been bothering other members, and some were very critical of my actions with comments like “what’s the big deal”, "you’re going to make enemies”, “you’re biting the hand that feeds you”, ...
Let me explain one thing about Dave Witko. I am a very black and white person (no Jeff I am not a mulatto). When praise is deserved praise will be given. When criticism is deserved criticism will be given. Maybe not always in the most politically correct or sensitive manner, but you get what I mean. What all of you do NOT know (except Al) is that on several occasions maybe 3-4 times in the past few years I have written personal notes of thanks to the factory (and sent via Al the postman) for delivering me perfect flawless instruments. I think the 47RI, the custom legend Slothead, the U681-12, maybe a few others. These instruments were spot on perfect and I went out of my way to make sure that the people responsible for this good work were recognized for it. Now, to NOT bring it up when things are not so perfect would have been hypocritical and wrong. That’s why I did it. You can question my method, but I don’t think you can question my motive. Think of it this way - I have a puppy and he’s cute, playful and I love him to death. But when he shits on the rug am I supposed to ignore it and hope that it does not happen again? Of course not. Action needs to be taken and it doesn’t mean that he’s still not cute, playful and loved to death.
In closing, remember this – The most reliable predictor of future performance is past performance. Unless something alters the path.
Dave |
|
| |
|
Joined:
June 2006
Posts: 7307
Location: South of most, North of few | Well said Dave. I think this needs to die now. |
|
| |
|
Joined:
April 2007
Posts: 318
Location: Slightly northwest of Trader Jim | ditto... :cool: |
|
| |
|
Joined:
December 2001
Posts: 7236
Location: The Great Pacific Northwest | Topic closed at the request of the author. |
|
| |
OFC Guitar # 8
Forums Archive -> The Vault: 2007
