This time I turned off the furnace, waited for zero street noise, no fan running on the laptop, mic 1 meter away. Sweep with all tone controls flat.
Looks totally different! I think it looks pretty good, eh? Please advise Art and JJ. Let me have it!
It is amazing to me how sound can change so dramatically based on so many different situations.
I put my guitar in a corner, like a Klipsch Horn, Ok a stretch, (see pic) the damn thing was more powerful. Not that I can play it that way, oh wait play into a baffle?
Then I put it on the floor, full volume, the damn thing sustained forever, I mean in a pre feedback loop? No squeal, just note sustain. I don't think it would ever stop, crazy! Let's rock! Joe
Looks totally different! I think it looks pretty good, eh? Please advise Art and JJ. Let me have it!
It is amazing to me how sound can change so dramatically based on so many different situations.
I put my guitar in a corner, like a Klipsch Horn, Ok a stretch, (see pic) the damn thing was more powerful. Not that I can play it that way, oh wait play into a baffle?
Then I put it on the floor, full volume, the damn thing sustained forever, I mean in a pre feedback loop? No squeal, just note sustain. I don't think it would ever stop, crazy! Let's rock! Joe
Radiating into free space, half space (one boundary), quarter space (two boundaries) or eighth space (3 boundaries) (4 x Pi, 2 x Pi, Pi or Pi / 2 steradians solid angle in Hornresp) all have dramatic effects on response, though in a room none of the boundaries are infinite, so room modes dominate low frequency response. Boundary gain increases low frequency output, increasing "sustain", the acoustic/mechanical feedback loop.
Your “Joe Jan 15” test shows a response rising from 44dB at 65 Hz to 49dB at 400Hz, +/-2dB out to past 3kHz, then rising response to 53 dB at 18kHz.
The response looks unbelievably good, as in too good to believe it’s true, given the prior responses and comments you have posted stating that the low end is huge and the high end drops off.
Background noise and low drive level could have been the problem in the “Joe Jan 7” test, but no way can it drop from 55 dB to 0dB today.
If the input to the drivers was around 2volts (one watt per 4 ohm driver) you should be seeing around 50dB more level at one meter if the test system is calibrated correctly, something like this:
What voltage level were you using in the above tests?
Are the horns or the soundboard side facing the mic?
Art
Thanks much Art, I just though of something. I have the mic 1 meter away from the horn/waveguide opening (mouth). So facing the horns, not the soundboard. The horns are 5 feet long, so the mic is actually 8 feet away from the driver. Is this correct? Maybe I will try putting it directly at the mouth. The dB level is low, so was wondering.
I was also pleasantly surprised about how flat the response was, about +/- 5 dB. Not sure how different a sweep is compared to playing a guitar thru the horns. Also I did say my bass was going way up when the horns were covered, great sound, but my REW measurement still had them lower than the mids. Then when the horns were sealed, my highs seemed to get stronger. So I had a strong mid (guitar range pretty much), with less on the highs and lows, but not AS less as a standard guitar measurement.
So this sweep shows strong mids, with lows somewhat below that, not surprising. What is surprising is how the highs/harmonics don't trail off, interesting.
Following the scientific method means I need to get my results to repeat, and show more evidence, I will do that. I might find good results again, or maybe I will find a flaw in my methods.
I will also test with the horns uncovered, just because I am curious. I will test with the mic at different distances, and different locations, in a different room. Plus I might even stick the mic inside the horn.
The other change was I used both channels this time, with a dual 1/4" patch cord to USB on the laptop. I am pretty sure last time I just used one channel, that obviously changed results (I need to keep better records). Plus the room was quite, furnace completely off, late at night, zero traffic noise during recording, no laptop fan going during recording. After that the guitar jamming was strong again, encouraging.
Plus I did more small hole drilling. I also bought a XLR to USB cord. I have about 50 cords, but of course not that one. I am experimenting with the Shure mic right into by laptop with DAW software, bypass the four track recorder. Need to listen to results though headphones, the laptop speakers are completely lame. Plus I am not so sure the laptop mic is worthy.
Boy was I surprised when I saw the +/- 5 dB, I thought the same thing Art, thats pretty good, did I do something wrong? If I can keep repeating this, great. If I can get this same relatively flat response at a higher dB with other mic options, also great. Stay tuned, more next weekend, traveling again.
Oh yeah I also started the sweep at 30 Hz instead of 0 Hz, so hence the change at the bottom. I will check out the voltage. Thanks! Joe
I was also pleasantly surprised about how flat the response was, about +/- 5 dB. Not sure how different a sweep is compared to playing a guitar thru the horns. Also I did say my bass was going way up when the horns were covered, great sound, but my REW measurement still had them lower than the mids. Then when the horns were sealed, my highs seemed to get stronger. So I had a strong mid (guitar range pretty much), with less on the highs and lows, but not AS less as a standard guitar measurement.
So this sweep shows strong mids, with lows somewhat below that, not surprising. What is surprising is how the highs/harmonics don't trail off, interesting.
Following the scientific method means I need to get my results to repeat, and show more evidence, I will do that. I might find good results again, or maybe I will find a flaw in my methods.
I will also test with the horns uncovered, just because I am curious. I will test with the mic at different distances, and different locations, in a different room. Plus I might even stick the mic inside the horn.
The other change was I used both channels this time, with a dual 1/4" patch cord to USB on the laptop. I am pretty sure last time I just used one channel, that obviously changed results (I need to keep better records). Plus the room was quite, furnace completely off, late at night, zero traffic noise during recording, no laptop fan going during recording. After that the guitar jamming was strong again, encouraging.
Plus I did more small hole drilling. I also bought a XLR to USB cord. I have about 50 cords, but of course not that one. I am experimenting with the Shure mic right into by laptop with DAW software, bypass the four track recorder. Need to listen to results though headphones, the laptop speakers are completely lame. Plus I am not so sure the laptop mic is worthy.
Boy was I surprised when I saw the +/- 5 dB, I thought the same thing Art, thats pretty good, did I do something wrong? If I can keep repeating this, great. If I can get this same relatively flat response at a higher dB with other mic options, also great. Stay tuned, more next weekend, traveling again.
Oh yeah I also started the sweep at 30 Hz instead of 0 Hz, so hence the change at the bottom. I will check out the voltage. Thanks! Joe
It's 'funny' how measurement systems (very useful) only approximate 'what is real'. (and, can be interpreted in different ways) > as an aside... Is there a way? to not have 50 cords... and not have the 'ONE' that works 'today'... for software. ? > I'm impressed with this project! > Can you share picture of actual guitar?
Thank you sir! Please stick with this thread, the more input, the better. Info attached, please share with others. Patent can be found on Goggle Patents.
I have another patent being reviewed by the USPTO right now, it includes improvements. Lets make the acoustic guitar rock! Joe
I have another patent being reviewed by the USPTO right now, it includes improvements. Lets make the acoustic guitar rock! Joe
Joe,
Even with the sweep starting at 30 Hz, hard to separate signal from noise with SPL at a whisper level of 45dB.
Considering you haven't checked the drive level voltage, can assume that you have not calibrated the system.
The acoustic point of origin is 5 feet (around 4.4 ms) behind the horn mouths, but the output must be measured outside the near field to be representative of what you hear. The output will vary considerably with frequency depending on the orientation of the measurement mic or your ears to the horn mouths.
You will probably find 10kHz around -20dB at just 45 degrees off axis, even less in front or above the guitar, expect that horizontal and vertical will be quite different also.
The curvature inside the horn mouths and their separation distance is going to make for some unusual polar patterns!
Art
Agree that the SPL is too low Art, not sure what is going on there, suspect.
I did calibrate the mic, and the amp was measuring flat at about 5.5V
Drive level voltage and system calibration? Uh-oh. Did I miss something, might this be a problem, please advise!
I did measure on axis at 1m from the horn mouth.
Hoping I will find the problem and get higher SPL but still flat, or at least a good FR, we shall see! Joe
I did calibrate the mic, and the amp was measuring flat at about 5.5V
Drive level voltage and system calibration? Uh-oh. Did I miss something, might this be a problem, please advise!
I did measure on axis at 1m from the horn mouth.
Hoping I will find the problem and get higher SPL but still flat, or at least a good FR, we shall see! Joe
For a loudness perspective, I'm "treating" a guitar I dont like the sound of, by beating on it with pink noise. For this I have an ordinary rubber band with a "S" hook holding the little Dayton exciter to the bridge. I'm using an amplifier that's mono output, plays whatever files I put on an SD card and uses a USB cable for power, which I've connected to a wall-wart I assume was intended for charging a phone.
I dont have the volume all the way up and considering the 5V powersupply, I figure I'm putting maybe 1.5W into it. It's located in a detached garage (so as to not drive everyone nuts) and I can still hear it inside the house. It's loud! I'd say about as loud as you could possibly make the guitar sound by playing on the strings. That's the volume level you want to shoot for. If I put a measurement mic 1M away, there's no way it would pick up on anything - plane overhead, car passing by - over the sound level it's putting out.
Still thinking you should try the measurement on the bed-plane or carpeted-floor-plane, rather than fiddle with walls 'n corners...
Stupid guitar. I paid $200 for it because it was supposed to be better than my Taiwan manufacture versions of the same model line, because it's made in Japan. Physical condition and appearance are great. Sounds like "Gimme an S, Gimme an H..." compared to a lesser grade instrument of the same line I have. Measures different than all the other guitars too; has this giant 30db suck-out at 500 Hz, where all the others have a resonance there. I'll show it who's boss; how about a 100 hour helping of pink noise excitation - 20 in, 80 to go!
I dont have the volume all the way up and considering the 5V powersupply, I figure I'm putting maybe 1.5W into it. It's located in a detached garage (so as to not drive everyone nuts) and I can still hear it inside the house. It's loud! I'd say about as loud as you could possibly make the guitar sound by playing on the strings. That's the volume level you want to shoot for. If I put a measurement mic 1M away, there's no way it would pick up on anything - plane overhead, car passing by - over the sound level it's putting out.
Still thinking you should try the measurement on the bed-plane or carpeted-floor-plane, rather than fiddle with walls 'n corners...
Stupid guitar. I paid $200 for it because it was supposed to be better than my Taiwan manufacture versions of the same model line, because it's made in Japan. Physical condition and appearance are great. Sounds like "Gimme an S, Gimme an H..." compared to a lesser grade instrument of the same line I have. Measures different than all the other guitars too; has this giant 30db suck-out at 500 Hz, where all the others have a resonance there. I'll show it who's boss; how about a 100 hour helping of pink noise excitation - 20 in, 80 to go!
JJ - crazy! Let us know how it goes.
Art - speaking of polar patterns, I often wonder what is happening with my curves/turns/distances. At work we use the Bernoulli principle for cooling systems with water. We want as many turns as possible, as it creates turbulent flow, which improves cooling as the water from the outside hot walls mixes with the cool water at the very inside (or close) of the water stream.
I know horns are often chamfered at the corners, so they are not square. My curves are closer to this than square, so hopefully helps. What I wonder about is do short sound waves have constructive interference, or cancelation, or both in turns? Same for long sound waves, which of course would be different, and every frequency for that matter. I would like to draw a series of vectors, but I don't think it would be accurate. Very complicated. Another reason FR is so important! 🤣
Art - speaking of polar patterns, I often wonder what is happening with my curves/turns/distances. At work we use the Bernoulli principle for cooling systems with water. We want as many turns as possible, as it creates turbulent flow, which improves cooling as the water from the outside hot walls mixes with the cool water at the very inside (or close) of the water stream.
I know horns are often chamfered at the corners, so they are not square. My curves are closer to this than square, so hopefully helps. What I wonder about is do short sound waves have constructive interference, or cancelation, or both in turns? Same for long sound waves, which of course would be different, and every frequency for that matter. I would like to draw a series of vectors, but I don't think it would be accurate. Very complicated. Another reason FR is so important! 🤣
Sound waves are not very analogous to water flow, though at low frequencies they behave somewhat like laminar flow, at high frequencies more like ray tracing. At high frequencies a narrow horn beams like a ray gun 😉.
Constructive interference (peaks), or cancellation (nulls) are dependent on the wavelength of the frequency (1130fps/frequency) and it's relationship to the radius and diameter of the turn.
Your 1/15/23 test of the offset horn shows virtually no peaks or nulls, and the rising response out to 18kHz just dosen't seem likely.
It's possible the BMR (balanced mode radiators) drivers avoid some of the problems of standard drivers of this size, but we won't know until you sort out your drive levels and determine that your system is calibrated.
To put it simply, if you put in 2volts to both drivers at 1000 Hz, your RTA and dB meter should read about the same, around 90-100dB, something similar to the simulations in post 462.
You will also see harmonics (X1, X2, X3 etc.) of the fundamental tone rising above background noise in the RTA if the amp or speaker distorts.
A harmonic -20dB below the fundamental is 10% distortion, -40dB is 1% distortion.
I'd suggest putting the horn on a keyboard stand, tray table, or ironing board as far away from any walls as possible for your tests, or else on the ground (floor), with the mic also on the ground. Ground plane will reduce boundary reflections, but make the low end appear 3-6 dB louder than it will be in a playing position, which is why I suggest using a stand for both the speaker and mic.
Art
OK Art, low is laminar and high is ray tracing, and all points in-between? So what is really happening with all the frequencies in my curved horns, somewhat of a mystery to me!
Yes need to get 90-100 dB, what happened? I will find it, I hope. 🤔
Thanks for the harmonics/distortion info, they were dropping off before, but not to much, so...another point of interest.
I will try the guitar/mic positions.
I attached REW compare info with better resolution again, the fundamental to harmonic does drop about 40 Hz total, does this show low distortion?
Let me have it, and thanks! Joe
Yes need to get 90-100 dB, what happened? I will find it, I hope. 🤔
Thanks for the harmonics/distortion info, they were dropping off before, but not to much, so...another point of interest.
I will try the guitar/mic positions.
I attached REW compare info with better resolution again, the fundamental to harmonic does drop about 40 Hz total, does this show low distortion?
Let me have it, and thanks! Joe
As I wrote sound waves are only somewhat analogous to water flow, you will need to test at various angles to find out what is happening with your horns. Two things for certain, the lows will wrap around the speaker 360 degrees, an omnidirectional pattern, the highs won't- they will progressively "beam" more at higher frequencies.
Either the amp or signal is set too low, or something else.
No, it doesn't show anything, it does not compare a known input signal with output.
REW can show you the distortion in a sweep, but using a single input signal sine wave tone you can see the fundamental and harmonics clearly, if they are above the noise floor.
Here are examples of harmonic distortion using my computer built in mic about .5 meter from it's right speaker.
At the 160Hz sine wave tone fundamental, the speaker produces 78dB, the second harmonic (320 Hz, H2) reads 42dB, -36dB below the fundamental, under 2% distortion. H3 is 50dB, -28dB below the fundamental, about 4% distortion. Not bad at normal listening levels. Things don't look so good at a lower frequency.
At 63Hz, the speaker fundamental is barely audible at only 32dB, H2 is -1dB, 89% distortion, H3 is 51dB, way over 100% distortion, and H4,5,6,7 are above the variable traffic noise floor. That said, if the heat pump happened to turn on, all but H3 would be below the noise floor.
Art
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Thanks Art, I thought external noise was a "maybe" but you show it is not, I believe it! If I have time tonight I will try again, if not then tomorrow night for sure. I will find the problem, I hope!
I have all my small holes for the soundboard drilled in the body walls tonight. (43) 5/64" holes, all centered well on the wall section, all straight. X-Y position is important to me, as they need to line up with features on the sound board that look decorative, but actually help soundboard movement.
My second patent should have been reviewed with a (6) month wait, it has been almost (9) months, go figure.
Thanks for the info about low frequency wraps 360 degrees, and the highs beam. I like to "picture" the sound waves in my head, I get frustrated with things I can't see.
I picture spherical lows moving at the speed of sound, and beaming highs moving at the speed of sound, yikes, complicated! I picture one of those all swords with a big spherical radius at the hand, and the blade straight out, the size of my wave guides traveling down them at the speed of sound, hello?! 🤔🤣 Lets rock! Joe
I have all my small holes for the soundboard drilled in the body walls tonight. (43) 5/64" holes, all centered well on the wall section, all straight. X-Y position is important to me, as they need to line up with features on the sound board that look decorative, but actually help soundboard movement.
My second patent should have been reviewed with a (6) month wait, it has been almost (9) months, go figure.
Thanks for the info about low frequency wraps 360 degrees, and the highs beam. I like to "picture" the sound waves in my head, I get frustrated with things I can't see.
I picture spherical lows moving at the speed of sound, and beaming highs moving at the speed of sound, yikes, complicated! I picture one of those all swords with a big spherical radius at the hand, and the blade straight out, the size of my wave guides traveling down them at the speed of sound, hello?! 🤔🤣 Lets rock! Joe
I had my horns pointing to the floor in the corner before, interesting. Tonight I had them parallel to the floor and pointing directly to the corner walls,
Klipsch style.
To bad I can't play my guitar this way, the power went up noticeably! I played an open tuning song (drop D), up and down the neck with different chords,
as I do often to test this guitar. The sustain was better than I ever heard. In fact, the low drop D string sustained so much I hit it about 1/3 the time
I normally do.
If I hit it every time, it was actually too much. I would stop at a good point, let the chord sustain, then continue with the song again, and of course end
with a chord that sustains for 25 seconds. Let's Rock!
Here is one way to see the beamwidth of a speaker:
These pictures show three more ways of visualizing the same polar response information, the center horizontal and vertical being the way you will see it in REW.
If the tape covering your driver's compression chamber is not backed with wood, it may be acting like a passive radiator, contributing a Helmholtz resonance.
The low frequency of your horns is omnidirectional, when it's sound pressure level becomes loud enough to vibrate the guitar body enough to vibrate the strings, electro-mechanical feedback occurs. You are calling this form of feedback "sustain", it will be way more of a problem when the soundboard is inches away from the horn.
Art
Thanks much Art, really great info. I should find a way to test that in my horn configuration, to visualize even better!🔊 Some day.
Yes the sustain is definitely feedback, and it only happens at full volume, or close to full volume. When I use my piezo only (which I like to do for finger picking) it is completely gone. The magnetic pickup seems to be more feedback prone (zero squealing, just this type of feedback), but I know that will change when the soundboard is installed. It might be the piezo that feeds back more then. I have "tested" this and it seems OK, we shall see. I think I noted before, the piezo would not even feedback on the horns themselves, unless they were approx. 4" or closer to speaker, and they will be on the soundboard.
I am going for the acoustic sound, but I do admit having more of an electric guitar sound at certain settings is desirable, so the controlled sustain is something I like. Uncontrolled, would be a disaster. Solos with sustain of course is great, but just a little while you are playing chords on the acoustic sounds very powerful and appealing, I have to admit I like it as an option only. The horns facing the walls in the corner had this guitar rocking last night, I could barely put it down, even played the same songs over and over, it was so appealing, an entirely different experience than playing regular acoustic guitar without an amp. Then I turn everything off and just play regular acoustic, its like what the hell happened to my sound! 🤣
The tape is over the first piece of wood above the driver compression chamber, then another piece of wood everywhere except that area, hence the tape. Older chamber divider with hole cut out, bad idea! This is the test guitar. The build guitar has a 1/2" solid piece of Baltic Birch, I could swap that out for testing. The third guitar has not been hand worked to have the driver holes and horn pathways cut out in the four areas. I am wondering how I can improve that, I have some "corners" in those areas that could probably improve. Maybe the polar response visualization above would show that?
The soundboard installed will be worse, eh? Yeah I know, worry about that a bit (nervous excitement). 🤔 I am trying to make time tonight to glue the bridge on the soundboard, must be precise location compared to the neck and soundboard install location. Sweeping tonight for sure- Dust My Broom! Joe
Yes the sustain is definitely feedback, and it only happens at full volume, or close to full volume. When I use my piezo only (which I like to do for finger picking) it is completely gone. The magnetic pickup seems to be more feedback prone (zero squealing, just this type of feedback), but I know that will change when the soundboard is installed. It might be the piezo that feeds back more then. I have "tested" this and it seems OK, we shall see. I think I noted before, the piezo would not even feedback on the horns themselves, unless they were approx. 4" or closer to speaker, and they will be on the soundboard.
I am going for the acoustic sound, but I do admit having more of an electric guitar sound at certain settings is desirable, so the controlled sustain is something I like. Uncontrolled, would be a disaster. Solos with sustain of course is great, but just a little while you are playing chords on the acoustic sounds very powerful and appealing, I have to admit I like it as an option only. The horns facing the walls in the corner had this guitar rocking last night, I could barely put it down, even played the same songs over and over, it was so appealing, an entirely different experience than playing regular acoustic guitar without an amp. Then I turn everything off and just play regular acoustic, its like what the hell happened to my sound! 🤣
The tape is over the first piece of wood above the driver compression chamber, then another piece of wood everywhere except that area, hence the tape. Older chamber divider with hole cut out, bad idea! This is the test guitar. The build guitar has a 1/2" solid piece of Baltic Birch, I could swap that out for testing. The third guitar has not been hand worked to have the driver holes and horn pathways cut out in the four areas. I am wondering how I can improve that, I have some "corners" in those areas that could probably improve. Maybe the polar response visualization above would show that?
The soundboard installed will be worse, eh? Yeah I know, worry about that a bit (nervous excitement). 🤔 I am trying to make time tonight to glue the bridge on the soundboard, must be precise location compared to the neck and soundboard install location. Sweeping tonight for sure- Dust My Broom! Joe
Post #466 shows you how to position your horns for polar tests, just need to do them at about 10 degree increments to get more than a rough idea.
The corners near the mouth will affect the polar response, the inner corners will mostly affect frequency response.
Indoor boundaries will also affect response, you need to be very precise in repeating set up conditions to make comparisons.
OK Art, I found the problem, see attached page 2. Highest SPL was 68 dB, where was this error message before? Behind another window?
The last two measurements obviously had this error, fixed it, now back to normal as before. So the last two FR pdf's were indeed suspect.
The good news is, I am getting about 100 dB max from the sweep, the bad news of course, is not as flat as before. I was at +/- 5 dB, now I am at +/- 10 dB on the mids, and +/- 10 dB on the highs, but a major drop off, so not total range.
These drivers are rated at 100 Hz to 20,000 Hz, so I understand the low dB below 100 Hz, but why does my guitar measure 80-90 dB below 100 Hz, so much higher? I like it, and can hear the great bass, please advise!
The mids look good, strong and very similar to my guitar output.
My guitar output highs are strong at about 85 dB, but this FR is about 75 dB, and the drop off from about 1,300 Hz to 2,000 is significant, not so great, what gives?
What do you think of this Frequency Response? I think this is the real deal, but I will test again, to verify the setup is legit. Let me have it! Thank you as always Art , I await with bated breath! 🤣 Joe
The last two measurements obviously had this error, fixed it, now back to normal as before. So the last two FR pdf's were indeed suspect.
The good news is, I am getting about 100 dB max from the sweep, the bad news of course, is not as flat as before. I was at +/- 5 dB, now I am at +/- 10 dB on the mids, and +/- 10 dB on the highs, but a major drop off, so not total range.
These drivers are rated at 100 Hz to 20,000 Hz, so I understand the low dB below 100 Hz, but why does my guitar measure 80-90 dB below 100 Hz, so much higher? I like it, and can hear the great bass, please advise!
The mids look good, strong and very similar to my guitar output.
My guitar output highs are strong at about 85 dB, but this FR is about 75 dB, and the drop off from about 1,300 Hz to 2,000 is significant, not so great, what gives?
What do you think of this Frequency Response? I think this is the real deal, but I will test again, to verify the setup is legit. Let me have it! Thank you as always Art , I await with bated breath! 🤣 Joe
Joe,
Can't help you find all the error messages 😉
As usual, your 1/22/23 test does not indicate any measurement conditions, but assuming the test was on axis, away from boundaries, the good news/bad news is your sweep looks similar to the response predicted in Hornresp.
We can see your horn's major nulls at 1.9kHz and 4.9kHz due to the offset driver orientation, pointing at the horn sidewall rather than the throat.
The peak and dip frequencies don't line up exactly, since the inputs used are not identical to your actual horn dimensions.
If you provided the actual cross sectional area along the horn path and volume of the compression chamber, a simulation could be a closer match to what you built. That said, the BMR drivers used have some properties that won't match the rigid piston model, which could explain some general differences, like a bit less low frequency than predicted.
You are using 1/12 octave smoothing, if you use less (1/24 or 1/48) or no smoothing, the horns sharp dips and peaks in response will look more like the simulation.
In other words, worse, like this example of the same response with no smoothing compared to 1/12:
The data sheet posted in #451 shows the drivers you use rated at 150 Hz to 20,000 Hz, with response -18 dB at 100Hz. I was surprised that the driver simulated as well as it did.
Since the horn's overall level drops so severely above 2kHz, your general impression of boosted bass when you play guitar through it tracks what the response appears to be.
You could try testing your JBL speakers response in the same location with the same amp and drive level to validate your test.
Cheers,
Art
Can't help you find all the error messages 😉
As usual, your 1/22/23 test does not indicate any measurement conditions, but assuming the test was on axis, away from boundaries, the good news/bad news is your sweep looks similar to the response predicted in Hornresp.
We can see your horn's major nulls at 1.9kHz and 4.9kHz due to the offset driver orientation, pointing at the horn sidewall rather than the throat.
The peak and dip frequencies don't line up exactly, since the inputs used are not identical to your actual horn dimensions.
If you provided the actual cross sectional area along the horn path and volume of the compression chamber, a simulation could be a closer match to what you built. That said, the BMR drivers used have some properties that won't match the rigid piston model, which could explain some general differences, like a bit less low frequency than predicted.
You are using 1/12 octave smoothing, if you use less (1/24 or 1/48) or no smoothing, the horns sharp dips and peaks in response will look more like the simulation.
In other words, worse, like this example of the same response with no smoothing compared to 1/12:
The data sheet posted in #451 shows the drivers you use rated at 150 Hz to 20,000 Hz, with response -18 dB at 100Hz. I was surprised that the driver simulated as well as it did.
Since the horn's overall level drops so severely above 2kHz, your general impression of boosted bass when you play guitar through it tracks what the response appears to be.
You could try testing your JBL speakers response in the same location with the same amp and drive level to validate your test.
Cheers,
Art
Thanks much Art, much to think about! Yes it was on axis, 1m away, that is how I measure almost everything, to be consistent. I do have some room in my third guitar to change the orientation of the drivers. I will send you a 3D STEP file of my horns (if diyAudio will accept that). You may not have a CAD system, so I will include a 2D drawing, and send you that as a pdf with all dimensions included. I will model it as built now, no driver holes or soundwave openings, wood safe, so to speak. Very much appreciate the offer!
Oh yeah 150 Hz, not 100 Hz for the driver rating. That is pretty amazing that Hornresp is so close, very encouraging. That means what you model with my horn dimensions will be highly accurate, and give me great feedback. If we can get a big improvement from any type of changes we make, that would be great!
You said "I was surprised that the driver simulated as well as it did", so what is your overall impression of this horn system?
Also I would like to simulate this horn at 80 dB max, 90 dB max...etc...any value to that? Since the 65 dB max looked good, but that
is just too low of a level for anybody to play.
I did not get my bridge glued on the soundboard, another work emergency. I will do that next weekend with the horn 2D drawing, some more sweeps to get better acquainted with REW, and some jamming of course. Also I was thinking about my 1/2" Baltic Birch testing, it really made a huge difference to eliminate feedback, so hopeful. I need to listen to Leo Kottke (one of my all time favs) in the car with my iPhone dB meter on, to get a feel for acoustic guitar sound at different dB levels. Thanks! Joe
Oh yeah 150 Hz, not 100 Hz for the driver rating. That is pretty amazing that Hornresp is so close, very encouraging. That means what you model with my horn dimensions will be highly accurate, and give me great feedback. If we can get a big improvement from any type of changes we make, that would be great!
You said "I was surprised that the driver simulated as well as it did", so what is your overall impression of this horn system?
Also I would like to simulate this horn at 80 dB max, 90 dB max...etc...any value to that? Since the 65 dB max looked good, but that
is just too low of a level for anybody to play.
I did not get my bridge glued on the soundboard, another work emergency. I will do that next weekend with the horn 2D drawing, some more sweeps to get better acquainted with REW, and some jamming of course. Also I was thinking about my 1/2" Baltic Birch testing, it really made a huge difference to eliminate feedback, so hopeful. I need to listen to Leo Kottke (one of my all time favs) in the car with my iPhone dB meter on, to get a feel for acoustic guitar sound at different dB levels. Thanks! Joe