jnorem
99 posts
Mar 08, 2014
3:25 PM
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I've been researching this topic and there's a lot of information to be found, including videos showing how to do. And it seems generally agreed that doing this makes a harmonica louder.
Has that ever been tested with a decibel meter?
If you only play amplified harmonica, does it still make sense to open the cover plates?
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Call me J
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walterharp
1337 posts
Mar 08, 2014
3:40 PM
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Good question. I think so, but there are rarely any scientific tests of anything to do with harmonica lore other than trusting those that work with lots of harps and their impressions.
To do this test correctly for each type of cover plate you would need to have at least 6 harmonicas of that make, 3 open and 3 not opened. Then you would need to have a mechanical note blower that used the same force to sound each note the same way across the entire note range. The signal a few cm away from the center of the harp would need to be recorded and analyzed for all notes top to bottom, and then some sort of cupped contraption, the same one, used on all of them and the signal recorded and analyzed.
There really is no incentive to test all the possibilities (who would buy 6 of every model of cover plate and do all this testing?), so believe what you want..
that said the tendency for customizers and higher cost harps seems to be toward open cover plates on the outgoing end of the harp, but having an open hole on each side is another whole can of worms, clearly related to the question as well
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smwoerner
246 posts
Mar 08, 2014
5:38 PM
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I just did a very unscientific test sitting at my bench with the sound meter on my phone and a collection of harmonicas.
I tested the following:
Special 20 Stock, Special 20 Open Back, CrossOver, Seydel 1847 Plastic Comb, Seydel 1847 Wood Comb - All in the key of c
I also tested:
Special 20 Stock, Special 20 Open Back, CrossOver - All in the key of G
Just for fun I threw in a Super 64X Chromatic.
I played the same melody (Soliders Joy in First Position). I played the harps one after another with my eyes closed and did for three rounds (I needed the practice). I reset the meter each time I changed harps.
All of the diatonic harps maxed in the range of 87 to 89 db. I played the Chrome three times and it was 84, 83, 85.
I don't know if this indicates that there is very little difference between the harmonicas or that I have a very consistent accoustic playing level.
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Purveyor of Optimized New and Refurbished Harmonicas.
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Last Edited by smwoerner on Mar 08, 2014 5:40 PM
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jnorem
100 posts
Mar 08, 2014
5:45 PM
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If you have a consistent acoustic playing style then that makes your tests all the more valid, I would have thought.
Your results are as I suspected all along. I'll be leaving all my cover plates just as they are.
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Call me J
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smwoerner
248 posts
Mar 08, 2014
6:03 PM
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Unfortunately the meter on my phone maxes out at 93 db due to the mic. Thus I set the phone far enough away, a little more than arms lenght, to keep from maxing it out. Open covers might allow you to project a little more if your really playing hard and forcing your breath. However, such playing should be an exception and not a player's normal style...unless maybe you're into some serious death metal harp...
Purveyor of Optimized New and Refurbished Harmonicas.
scott@scottwoerner.com
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jnorem
101 posts
Mar 08, 2014
7:03 PM
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So…why do all these harmonica experts make it such a point to open the covers? It's not all that easy a thing to do, you know. I know, I've tried it several times on my laying-around-the-house harmonicas.
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Call me J
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STME58
667 posts
Mar 08, 2014
9:22 PM
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I opened the back of an SP20 with a BMH kirinite comb for the purpose of being able to see in more clearly with a high speed camera. I did not find it too hard to open the back. I used tin snips to make a cut on each side and a plastic jawed vice to hem the metal over.
I can't say that the harp is louder but I do perceive a difference in timbre. I like the way it sounds, but I don't get a lot of opportunity to use an Ab harp.
@swoemer your study is not far from being scientific. Have you ever heard of design of experiments? It is way to set up experiments, like yours, that can be done using simple equipment and a lot of variables and still either get meaningful results or let you know that the changes were not due to something controlled in the experiment.
I expect that as a musician, you have a subconscious level control to get the sound level you want. That might be why the levels can out so close (or it could be that opening the covers makes little difference). To test this hypothesis. you could wear a good set of hearing protection so you really can't tell how loud you are playing, and measure the sound level as you try to blow at the same pressure. A couple of important things about an experiment like this are randomization, (change the order and if possible you should not know which harp you are playing) and replication, (do it at least 3 times on each harp, but not 3 time in a row on the same harp, to see if you get the same results each time. With a bit of math you can easily determine if you have found a significant effect, no effect or variations due to something you are not controlling for. The third result happens most often, but it is quite exciting when you get the first result and learn how to make thing go the way you want them.
Last Edited by STME58 on Mar 08, 2014 9:24 PM
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jnorem
103 posts
Mar 08, 2014
9:39 PM
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But he's already shown that opening the cover plates does not affect the volume, and thinking about it, why would it?
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Call me J
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STME58
669 posts
Mar 08, 2014
10:10 PM
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What was shown by the experiment posted above was that the sound on a harp with the cover plates opened was not measurable louder, with a small sample size, than one with the cover plates unopened. This is subtly but importantly different from showing that opening the cover plates does not effect volume. While this results of this experiment are consistent with the hypothesis that opening the cover plates does not effect volume, it does not prove it, because we don't know what else may have changed (most obviously breath pressure). Further experimentation could narrow this down. Coming up with a good hypothesis and a good experiment is not easy. It might be easier than writing a grant to get funding to study the issue though! ;-) The results of such a study could be important to tens of people around the world.
I can see two ways that opening the cover plates could effect the volume, one is the obvious removing of a sound baffle. The other is that you change the natural frequency of the cover plate when you hem the edge over(anyone else notice how a Manji or Crossover with an open back's covers vibrate strongly on certain notes?). I would expect both of these effects to be very small but a lot of things that seem unlikely turn out to be true. Who would have thought putting dimples on a golf ball make it fly further?
Last Edited by STME58 on Mar 08, 2014 10:15 PM
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1847
1553 posts
Mar 08, 2014
10:21 PM
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so what if you did the test with the cover plates off?
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i get a lot of request when i play my harmonica
"but i play it anyway"
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smwoerner
249 posts
Mar 08, 2014
10:28 PM
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@STME58, Interestingly when I was playing the the Crossover seemed loudest which I expect is partly due to the side vents and the brighter tuning, the Seydels seemed louder than the Special 20's and I would get confused as to which Special 20 I was playing.
I didn't play each harp 3 times in a row (except for the chromatic). I would play one set it off to the side and then grab another until all were played and then repeat kind of randomly. Since I was sitting them face down I didn't know which Special 20 I was playing until after I opened my eyes and looked at the meter and the harp. I guessed wrong several times.
Like you I wonder how much I was adjusting my breath based on what I thought was the volume.
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Purveyor of Optimized New and Refurbished Harmonicas.
scott@scottwoerner.com
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nacoran
7590 posts
Mar 08, 2014
10:41 PM
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It changes the tone a little too, I think, having to do with compression. I can hear it, and I'd describe open covers as a little brighter and closed covers as a little warmer. That said, my go to harps actually tend to be Lee Oskars and Sp20s and generally, if I had to pick, gun to my head, which I preferred, I'd lean a very tiny bit towards closed. That said, if you have some Sp20s, buy a couple cheap Blues Bands and open the cover up on one of them. Leave the other alone. Take the covers off and try them on your Sp20 and see which one you prefer, and you'll only be out maybe $12 or so in parts, and you can mess around with the reeds on the Blues Bands to experiment with some customizing techniques like embossing where you may break a few reeds learning.
Opening covers is simple (especially if you are just worried about tone, not looks), although I'd suggest adding longer screws to serve as supports is a good idea since they are a little more prone to crushing. I would suggest trying it. I can hear the difference, but it's subtle, and I could go either way on which I prefer.
You'll also learn one of the differences between Sp20's and Blues Bands is their 'nearly' identical covers. A Sp20 cover is fairly comfortable, a Blues Band cover is a medieval torture device. Little things, like the corners- thing is, there are better covers than Sp20s, and taking the same sorts of modifications forward you can improve the feel of better harps a bit too (sanding corners, the fronts of reed plates on protruding reed plate harps, rounding the ends of tines- they are all things that are fairly easy, and if you are careful, fairly safe. Whether you think they are worth the time is an individual call, but again, I think it's one of those things worth experiencing to see if it's important to you.
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Nate
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STME58
670 posts
Mar 08, 2014
10:46 PM
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@smwoerner,
It sounds like you have a pretty good knack for setting up experiments. An interesting one to try might be to put on a good studio headset so that most of what you hear is coming through the headset, then have someone change the volume of the sound to the headset while you try to hold a constant volume. I expect that as the sound to the headset is turned down you would compensate by blowing harder, even if you tried not to.
It would be hard to isolate the sound completely to the headset because some of the sound will travel though you jaw bone to your ear, but even so, you might see an effect on your volume that corresponds inversely with the volume in the headset.
I seem to recall people complaining of blowing out harps at a gig because they could not hear themselves in the monitor.
"Seemed louder" is a key phrase. You can select two sounds with exactly the same sound pressure level and one will seem louder to the typical person(say a well played cello vs fingernails on a chalkboard). Where I work we now use a psycho-acoustics lab rather than just a semi-anechoic chamber with sound pressure level equipment to determine not only the level of the sound our products make, but how the sounds are perceived by the customer.
Last Edited by STME58 on Mar 08, 2014 10:48 PM
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jnorem
104 posts
Mar 08, 2014
11:27 PM
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But if you take the harmonica, any harmonica, and cup it up to a JT30 or similar microphone, the thing is going to sound the same as is, with the covers opened up or with the cover plates removed.
Am I wrong?
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Call me J
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BluesJacketman
91 posts
Mar 09, 2014
12:34 AM
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another advantage and the reason why I try to open the covers on any harp I own is the increase in air flow, which makes the harmonica easier to play.
Try this play harp behind a door that is partially open. Then try it again with the door open all the way. Same concept with covers. Open bacs are louder because none of the sound is bouncing back into the harmonica.
Last Edited by BluesJacketman on Mar 09, 2014 12:35 AM
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STME58
671 posts
Mar 09, 2014
8:56 AM
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Some of the reasons a discussion like this can go on and on without resolution is that there are a lot of variables that can compensate for each other and the difference is subtle. Even if someone were to do an experiment that conclusively proved opening the covers on a particular harp in a particular way increased(or decreased) the sound pressure level by X.X decibels,some people might notice the difference and some might not due to differences in the way each person hears.
It is quite easy to come with two sounds that at the same sound pressure level, one is almost universally perceived as louder than the other. Not only is the generation and propagation of sound very complex, with small changes sometimes making a large difference, but the physical and psychological process of hearing is also quite complex.
I already know from experience that the tone and volume of a harp can be changed greatly just by the player with no change to the harp. I also expect that a player makes many subconscious changes based on what is hear to keep the sound the way it is desired. It also seems clear to me that the difference in loudness and/or timber due to opening the back of a harp, if any, is subtle. It seems quite reasonable to expect that a well practiced player could overcome this difference and make a harp with and open back sound the same as a closed one. In fact it might be difficult not to.
Take any massively multivariate problem with subtle hard to measure effects and humans in the loop as one of the variables, and you have something to keep lively discussion going for decades. I used to have very similar discussions with folks on how best to build bicycle wheels.
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arzajac
1299 posts
Mar 09, 2014
9:41 AM
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I open the covers on the harps I work on based on the following evidence:
1- Most customers ask for it/prefer it for some reason.
2- Most customers say the harps look better with open covers.
3- No one has ever claimed that open covers make harps sound worse. If there is no benefit to opening them up, at least there is no drawback, either. I cannot recall anyone ever asking me to not open them up.
So you can as Why? or why not?
To me, it's as simple as that! Keep it simple. Comparison: The debate around side vents is far from being resolved and it would seem to me that the difference in tone between side vents and no side vents is a lot easier to quantify than open versus closed backs.
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Custom overblow harps. Harmonica service and repair.
Last Edited by arzajac on Mar 09, 2014 12:14 PM
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bublnsqueak
25 posts
Mar 09, 2014
12:03 PM
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I reckon the difference is in dynamic range not volume.
In the same way that cupping your hand and waggling your fingers about manipulates tone. I think that opening covers will add something to the top end.
So, for those interested in research methods, we have been measuring the wrong DV!
Paul
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Frank
4001 posts
Mar 10, 2014
5:44 AM
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What's nice about open cover plates - is they're more open, I like that openness,,, it's nice :)
"it was a breezy evening and the window was open"
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Last Edited by Frank on Mar 10, 2014 5:46 AM
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HarpNinja
3807 posts
Mar 10, 2014
6:17 AM
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It changes the timbre, but I don't notice a change in volume necessarily. Stock SP20 covers sound more warm and muted, IMO.
I've experimented with this using a dB meter and frequency analyzer from my iPad. The difficulty was trying to get screen shots of the data.
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Mike
My Website
My Harmonica Effects Blog
Rock Harmonica Lessons
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S-harp
200 posts
Mar 10, 2014
6:45 AM
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I also open up the plates.
Tone and volume aside, that has been discussed above, I'd like to add one more reason to open the covers. Durability.
I steepen the angle of the ridge on the back of the covers. That makes it more sturdy. I also do that on already opened covers, like Manji ...
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The tone, the tone ... and the Tone
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jpmcbride
33 posts
Mar 10, 2014
12:32 PM
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These kinds of experiements have to be very tightly controlled to draw any conclusions. I'm an electrical engineer and for years designed products that had speakers in them which I had to test the SPL. In order to get anything resembling repeatable data, you have to at least control the following:
(1) Fix the distance from source to sound meter. Easy enough to do with a simple fixture.
(2) Make sure each sound source is given the same energy. Not sure how to blow the harp the same every time unless you built a fixture to blow it with a mechanical device.
(3) Control background noise.
You may think I'm going overboard, but I've worked through this in detail in the past and believe me these things make a difference. A few centimeters can make a noticable difference in the sound level. I used to stay late and make the sound measurements at night when no one else was in the lab. One night I was getting 2dB random variations and finally figured out it was the air conditioner in the building turning on and off!
BTW, I like to open up the back of SP20's and they sure sound louder to me. But with harp, what the player hears (behind the harp) doesn't always agree with what the listener hears (in front of the harp).
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Jim McBride
www.bottleoblues.com
Last Edited by jpmcbride on Mar 10, 2014 12:32 PM
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HarpNinja
3812 posts
Mar 10, 2014
1:37 PM
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When I test I use a bellow close miked.
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Mike
My Website
My Harmonica Effects Blog
Rock Harmonica Lessons
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MP
3112 posts
Mar 10, 2014
1:47 PM
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"important to tens of people" yeah, not a whole lot of importance. :-) Joke!!
I use a hammer and the edge of a 2X4 to open SP/20s. It's easy and takes a couple of minutes and you get to hit the harmonica for the pain it caused you.
I like the way they look opened and the access and they seem brighter but I doubt they are any louder.
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Affordable Reed Replacement
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nacoran
7599 posts
Mar 10, 2014
2:35 PM
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I think it's different than when you cup the mic. When you are cupping the mic you are creating a pressure area that includes the pickups. When you have a closed back harp the pressure area is still in the harp.
That said, you'll get more change in tone with your embouchure or with amps and pedals, but it's easier than embouchure and cheaper than amps and pedals.
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Nate
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CarlA
471 posts
Mar 10, 2014
2:46 PM
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I noticed that when my harmonica cover plates are closed, I play like myself. But, when I open-up the cover plates, I play just like Kim Wilson! It's the weirdest thing??
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jnorem
105 posts
Mar 10, 2014
3:01 PM
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"I noticed that when my harmonica cover plates are closed, I play like myself. But, when I open-up the cover plates, I play just like Kim Wilson! It's the weirdest thing??"
Hah!
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Call me J
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Frank
4006 posts
Mar 10, 2014
3:08 PM
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I sing just like Kim in the shower, it's uncanny how being naked with water pouring over you can be so transformative - by the time I'm toweled off the illusion has ended :)
Last Edited by Frank on Mar 10, 2014 3:17 PM
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CarlA
472 posts
Mar 10, 2014
4:11 PM
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"I sing just like Kim in the shower, it's uncanny how being naked with water pouring over you can be so transformative - by the time I'm toweled off the illusion has ended :)
Last Edited by Frank on Mar 10, 2014 3:17 PM"
Lol!
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STME58
672 posts
Mar 10, 2014
4:21 PM
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Frank,
Your comment on openness got me thinking, If covers were made of clear polycarbonate, they could be both open and transparent which would allow the creation of clear honest music, without misunderstandings or hidden agendas!
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nacoran
7600 posts
Mar 10, 2014
5:49 PM
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STME58, I think Turboharp has some clear Turbolids. If I'd thought about it maybe I would have got a clear one. I have a black one instead. It's actually an interesting example of extreme open backs. It does seem to effect tone. I just wish it would work with non-recessed combs, or that one of the customizers would make recessed combs, so that I could mix and match colors. (Actually, I think BlueXlabs has recessed milled combs, and they do have some nice colors, but not nearly the selection that someone like Tom has.)
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Nate
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STME58
675 posts
Mar 10, 2014
9:45 PM
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@jpmcbride,
Your experience with SPL measurements is similar to mine. It is indeed a tweaky business.
The UL requirements for making this measurement specify exactly how to place the product under test and where to place each of the microphones required to get a reading all around the product under test.
It would be interesting to set this up to see if opening the covers makes a harp louder or moves sound from the sides to the front. Unfortunately, I no longer have access to a semi anechoic chamber and the measuring equipment.
It might make an interesting Project for an harmonica playing engineering student at a well equipped university. It would be pretty cool to see a collaborative effort between the music, physics and engineering departments. The hardest part of setting this up might be convincing the music department that the harmonica is an instrument! :-)
Last Edited by STME58 on Mar 10, 2014 9:45 PM
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1847
1568 posts
Mar 10, 2014
9:53 PM
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if we need access to a semi anechoic chamber and the measuring equipment.
then it is most likely not significantly louder
here is a simpler test.... grab someone you know....anybody
have then stand maybe three feet away,have them turn around so they are looking the other way.
play both harps... ask them if there is a difference in volume
should be readily apparent if one is LOUDER
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i get a lot of request when i play my harmonica
"but i play it anyway"
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STME58
676 posts
Mar 10, 2014
9:58 PM
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I think that if it was SIGNIFICANTLY louder we would not be having this discussion. I am sure I can get a closed back harp to make a sound louder than an open backed harp. Opening the back is a second order variable at least. Might not even be worth discussing if I were not procrastinating what I should be doing but don't want to right now :-)
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jpmcbride
35 posts
Mar 11, 2014
11:25 AM
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1847,
Perhaps a decent quick test ... but I would make two changes to this test.
(1) Make the harp player blind as to which harp he is playing (open or closed back). Just expecting the open back harp to be louder may encourage the player to play louder.
(2) Perform the test 3 or more times and see if the results are consistent.
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Jim McBride
www.bottleoblues.com
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harpwrench
794 posts
Mar 11, 2014
11:34 AM
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A big flaw in these testing scenarios is the use of more than one harp:)
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1847
1573 posts
Mar 11, 2014
11:51 AM
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if you use a blind harp player
he will not be able to see how cool they look with the open back.
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i get a lot of request when i play my harmonica
"but i play it anyway"
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MP
3113 posts
Mar 11, 2014
11:55 AM
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Good point harpwrench!
One could do the test by switching open and closed cover plates on the same SP/20 or what have you.
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Littoral
1047 posts
Mar 11, 2014
12:10 PM
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Yes, controlling the variables here borders on hopeless. The same harp with different covers would be a good start. Perhaps 10 good players A/B the same phrase blind with exactly the same recording gear and gear to measure parameters. They can then assess all 10 on the same playback gear via a carefully constructed rubric.
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CarlA
473 posts
Mar 11, 2014
12:46 PM
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I wonder if players like Kim Wilson, Rick Estrin, Mark Hummel, Billy Branch, etc worry about whether an open cover harp is louder???
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Frank
4014 posts
Mar 11, 2014
12:55 PM
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They're most likely more concerned with reed action and tuning - and prefer at the least, side vents in cover plates :)
Last Edited by Frank on Mar 11, 2014 12:56 PM
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jpmcbride
36 posts
Mar 11, 2014
2:22 PM
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I agree, the experiement borders on hopeless. I say if you like the sound of the open covers, then go for it. Maybe its just louder to you, but who cares. Doesn't hurt anything.
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Jim McBride
www.bottleoblues.com
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CarlA
474 posts
Mar 11, 2014
5:16 PM
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Just got a Hohner Rocket today. Man, are they LOUD!! I attribute this to the open cover plates and side vents! In fact they are so loud, I think I am going to go to the loudest blues jam in town with no amp, mic, or PA support! I think the Rocket can keep up with the guitar heroes and 100watt guitar amps no problem.
In fact, I wish Hohner would place a volume pot somewhere on the Rocket to make sure I don't reach too crazy high a decibel reading at the jam accoustically!
-Carl
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bublnsqueak
26 posts
Mar 11, 2014
11:27 PM
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I like to open the top covers for harps played in 1st position and the bottom ones for 2nd position.
Means I can buy more harps.
P
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Ugly Bones Ryan
61 posts
Mar 12, 2014
7:27 AM
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I opened up one of my special twenties and I love the tone so I opened the rest up. The answer is yes it is much louder. I don't need to measure it, the loudness is just too obvious. I preferably play amplified and I love the way it sounds. It doesn't sound soft and whimpy.
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walterharp
1341 posts
Mar 12, 2014
8:20 AM
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you could do the experiment with more than one harp.. as mentioned above. But you would need to replicate, with the more replicates per treatment (open or closed covers)giving the better ability to statistically find small differences. At least 3 replicates per cover type would be needed (6 harps per test). This would need to be done for every model of harp tested, and every key (or a range of keys at least). One would not want to use a real player, but a machine that could replicate the blow or draw pressure exactly from harp to harp.. Real players almost certainly would adjust their technique somehow. And you would need spectral analysis of the sound both played free and cupped. The cup would need to be some mechanical thing that would be the same across all. Impossible, no, likely for anybody but a major harmonica producer to do..
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