 |
| |||||||
|
Welcome to the Jazz Guitar Forums. You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today! If you have any problems with the registration process or your account login, please contact contact us. |
 |
| | LinkBack | Thread Tools | Display Modes |
|
#1
11-26-2009, 06:47 PM
| |||
| |||
 Comparing Speakers That You Don't Have The following is a scenario that I - and many others - have experienced. Needing to replace a loudspeaker, how does one make a sensible selection when it's not possible to make a side-by-side comparison between two different speakers ? Unhappy with the performance of the loudspeaker in his small amplifier, Tal would like to replace it. He's looked up the original speaker, which the manufacturer describes as: "Very loud, touch sensitive and responsive with nice bell-sounding top end and a little bite." He is thinking about a speaker recommended by a friend that has this description: "Performance optimized for lead guitar. Also suitable for bass guitar, vocal P.A., keyboards, club music systems and stage monitors." Unimpressed by marketingspeak, and slightly troubled by the fact that the same manufacturer actually makes BOTH speakers, our man decides that a comparison between the two should be based on measurements of the two speakers under consideration. A side-by-side comparison being impossible, he makes a brief search of the products on the internet and finds these sound pressure level (SPL) curves, one for his existing speaker and one for the new speaker being considered:  Yankee's Best Loudspeaker  Empire Ruler Loudspeaker Looking at both performance curves carefully, Tal observes that "his" Yankee has higher SPL (it's louder) but less bandwidth (total frequency response) than the Empire. He makes what he believes is a reasonable assumption: that the total power the speakers can project is actually about the same. He believes the difference is in the way that the power is distributed across the frequency range. Tal doesn't spend money carelessly and he wants to make this speaker exchange only ONCE. He feels that the speaker decision needs to be based on how he's always made decisions about music: with his ears, but how to do this ? Technological advances in digital signal processing (the same technology represented in low cost CD players) have progressed logically toward sophisticated computer recording and editing programs. These are universally available, free or at modest cost. These programs have an incredible array of post-processing features, some of which are overlooked due to their simplicity of purpose. Tal has downloaded a free, open source recording/editing DSP-based program called "Audacity". As his flash of intuition has suggested, he opens the program and notes that there is an "EQ effect" that he can adjust to emulate an SPL curve to any desired level of accuracy (depending upon how much time he wants to spend equalizing the SPL curve). (Note that "Audacity" is not claimed to be superior to similar commercial programs but it is free.) Re-examining the original "Yankee's Best" SPL curve, Tal makes some graphical modifications. He's noted that the lines depicting measured speaker SPL are not smooth, there are lots of "squiggles" in the frequency response. Most can be ignored because differences in levels of less than 2 dB or so are not distinguishable by the typical human ear. Tal starts to draw some straight lines through the erratic responses of the SPL curves, approximating the slope and magnitude of the measured response. He realizes that if he WANTED to exactly replicate every nuance of the squiggly variations of the SPL curves, he could do so, but it would require a LOT of time. (There are many ways to perform this exercise, one of the easiest is to click on the SPL curve displayed on the internet by the speaker manufacturer, "copy" the information, then "paste" it somewhere convenient, like this document that I'm typing. Then "draw" the lines with whatever drawing tools are available on your computer. Since this document was typed with Microsoft "Word", I used the tools available in "Word". Microsoft "Paint" also works well, just use whatever works and is familiar to you. If you happen to have the catalog with the SPL curve displayed, you can draw in the straight line approximations with a pencil.)     |
|
#2
11-26-2009, 06:48 PM
| |||
| |||
| This is Tal's approximation of the SPL curve after he drew his lines on it:  After this exercise, Tal wants to use "Audacity" to set up an equalization curve (in the "effects" section) to duplicate his speaker SPL curve. (Each of these recording programs has it's own peculiarities and preferences, since "Audacity" is the one that I have, it must be the reference for our purposes.) Tal needs to establish a maximum signal level and for Audacity this is 0 dB reference. (Note that the SPL curve, properly, is calibrated in a scale that is appropriate for the human ear, not for our recording purposes.) Tal decides to modify the SPL level curve by "normalizing" it to "0 dB". This is easily accomplished by subtracting the maximum SPL from the SPL of each point on the curve. The first point on the curve, 70 dB, would become (70 - 108) or -38 dB, the next point on the curve, 96 dB becomes (96 - 108) or -12 dB, the peak reading of 108 dB becomes (108 - 108) or 0 dB and so forth. (Note that the SPL curve characteristics have NOT CHANGED, just re-referenced to a level that the recording program can use "0 dB". Attempting to input SPL of 108 dB would either not have been permitted by the program or would have resulted in unbearable, hard-limited compression.) After Tal adjusted the Audacity equalizer, he gave it a name (the speaker name) and saved it in the program … but it looked like this:  He then repeats the exercise, using the SPL curves from the "Empire Ruler" speaker that he is considering.  After "normalizing" again (and noting that the peak SPL for this curve is 100 dB, not 108 dB) to a peak level of "0 dB", Tal adjusts the EQ curve in the effects section of Audacity and saves it. It looks like this:  Tal is almost done … he's created and stored the SPL curves of the two speakers, now all he need do is play some music through them and LISTEN. But he doesn't want to use pre-recorded music, if possible, because it's ALREADY EQed and adjusted. The best possible tool, since his intent is to put the speaker in a guitar amplifier, is his guitar, recorded direct into the computer, no amplification (which would "color" the sound of the instrument). (So plug in your guitar, controls set as you normally would adjust them, and record a clean track using as many different positions on the neck possible, single notes and chords. It doesn't have to be good PLAYING, just representative of your guitar(s) sounds. Save an unmodified copy of this for other, future comparisons. Using your recording software, separate the recording into two tracks, left and right. EQ one of the tracks using the "Yankee's Best" SPL curve created a few minutes ago. EQ the other track with the "Empire Ruler" SPL curve just created.) Now the two tracks have to be adjusted for level (remember that the two speakers have different peak SPL - they are 8 dB different). Tal sets the amplitude of the "Yankee's Best" track to a convenient level, consistent with no distortion or computer (hardware or software) problems noting that the other track has to be adjusted 8 dB LOWER in level. In Audacity, Tal simply picks "amplify" from the effects menu, sets the level to "0 dB" and "amplifies" the "Yankee's Best" track. Then switching to "Empire Ruler" track and selecting "-8 dB" from the level effect, he "amplifies" the new track. Both tracks are now adjusted for frequency response and relative amplitude for both speakers. Plugging a pair of flat-response headphones into his computer (sound card, that is), Tal plays back his work. Alternately slipping a headphone off an ear, listening to a single channel, then doing the same on the other ear, gives him a very good idea of the differences between the two speakers. (Playing back the two tracks through speakers may not provide an accurate comparison because of the contribution from room acoustics.) NOTE: Whatever means is being used to evaluate the two tracks MUST have a flat frequency response - if not, the comparison is invalid due to variation in SPL curves introduced by monitor speakers or headphones. I'm sure that many are thinking at this point that this is a LOT of work. But it's not, it takes about ten minutes to EQ a SPL curve, start to finish. Add five minutes or so to record your instrument and another ten minutes to set up your software, EQ and playback … the entire process should take way less than an hour. And once you have your source material (guitar) recorded, the comparison of other speaker SPL curves will require only the ten minutes or so required to create another EQ curve and a few moments listening time. OK, so let's hear a sample …. I picked a CD from a musician named "Bob Culbertson", a slight acquaintance from the San Francisco Bay Area. This is his composition "Bourbon Street" and he's playing a "Chapman Stick". Rather than trying to make my abused fingers functional, I used Bob's music because his Chapman Stick covers a fairly broad audio spectrum. The left track is the "Yankee's Best" speaker emulation and the right track is the "Empire Ruler" speaker emulation. Click here to listen to 06 Bourbon Street.mp3 Last edited by randyc : 11-26-2009 at 11:27 PM. |
|
#3
11-27-2009, 12:55 AM
| |||
| |||
| This should be a compelling and audible recommendation for SPL measurements. These specifications are currently the only way to compare loudspeakers, barring a side-by-side "A to B". I just listened to the tracks - on the tiny little speakers of this laptop computer - and the differences are more pronounced than with the headphones used to evaluate the tracks earlier. (I suppose I should have already known that - recent responses to the post regarding "home recording" universally suggested that headphones were a poor idea and that monitors were the best way to listen to recordings, when editing (or comparing). OK, LPD and others, I FINALLY get it!) Regarding the previous exercise, I omitted conclusions and this was by intent. Your observations may dramatically differ from my own - I'm (ahem) old and my ears are not sensitive, especially higher frequencies. Since you've read and listened you will have formed your own conclusions by now. I've often pointed out the importance of speaker SPL, noting that a difference of 3 dB in loudspeaker SPL is the same as either doubling or halving amplifier output power. That should resonate rather emphatically with most … like moving up from a Fender Princeton to a Fender Deluxe Reverb ! But I've also observed that human hearing can't detect small differences in SPL. (Many that study the subject of audible sound suggest that the minimum detectable change in power level is 1 to 3 dB.) There's a dichotomy - and I'm definitely NOT the one to resolve it … In the sample recording, the two extremes of peak SPL were 8 dB apart. The average SPL was about 3 dB. So - was the difference in amplitude easily detectable ? (And that isn't a simple question because - in our earlier example - "Tal" noted that the two speakers distributed the output power over different frequency ranges. He inferred that this had a lot to do with the discernable "loudness".) Personally, it's easy for me to note the difference in "loudness" between the left and right channels but the enhanced frequency range of the right channel (the "Empire Ruler" loudspeaker) was harder to hear. My wife observed the "presence" in this channel easily, but then she is younger... OK, moving on, your observations and comments are welcome, concerning any or all of the following: The method of evaluation - is it appropriate? Is the method understandable? Is it possible for you to use the method? Can I help resolve misunderstandings? Cheers, RandyC PS: listened again to the two tracks again today, this time through the small monitors in my lab. The differences between the two speakers was really dramatic ! Personally, the second speaker (the one on the right channel) wouldn't even be a consideration for me - at least for guitar. Last edited by randyc : 11-27-2009 at 04:28 PM. Reason: add PS |
|
#4
11-27-2009, 04:18 PM
| ||||
| ||||
| You should start your own blog. |
|
#5
11-27-2009, 04:26 PM
| |||
| |||
| Assuming that's a compliment  then thanks ! I don't think that I could stay on top of it, though. I have periods of energy and ambition (and I'm fairly dedicated to passing along some useful information accumulated over the years). But my wife and I have medical issues and we're approaching another surgical procedure soon (hers, this time). I may not have much time even to participate here, as much as I enjoy it !cheers, randyc |
|
#6
11-27-2009, 04:59 PM
| ||||
| ||||
| There's a lot of blogs with less info than you post here, but you can't beat the dialogue going on at this site. |
|
#7
11-27-2009, 08:49 PM
| |||
| |||
| OK, here's another speaker comparison, again using Bob Culbertson's Chapman Stick music as source material. Going back to our original "story", our man Tal is still searching for a speaker to replace the 10 inch speaker in his small amplifier. He repeats the same procedure used initially (this time he took a look at the clock when he started and when he completed). Tal pulled up the SPL curves on three different 10 inch Jensens, marked them up as he did previously. After subtracting the maximum SPL from each curve and "normalizing" the curves, he made EQ curves in his free "Audacity" software. This took just under fifteen minutes for the three speaker curves. Loading Bob's tune into "Audacity" takes another couple of minutes. Tal makes two separate tracks from the material, applies his original speaker EQ to the left one and applies the Jenson P10Q EQ to the right channel. Then he adjusts the tracks for the difference in SPL (the original SPL curve is 1 dB louder than the "new" Jensen curve). After listening to the playback, Tal uploads the tune on his host server. Total elapsed time about twenty-five minutes. Here's the tune for comparison between the two speakers: Click here to listen to 08 The Newz.mp3 (Tal feels like the Jensen is a good speaker but it's not quite as loud as his original and he doesn't notice any substantial improvement in tone. He's surprised by the fact that the Jensen costs about $40 more than his current speaker. He's starting to think that the original speaker isn't so bad, after all !) |
|
#8
11-27-2009, 09:23 PM
| |||
| |||
| And one more - this time comparing the original 10 inch speaker with 12 inch speaker. I expected to hear a greater differerence ... 10 inch on left channel, 12 inch on the right. Click here to listen to 02 Flying Lady.mp3 |
|
#9
11-28-2009, 04:02 PM
| |||
| |||
| For those who might be intimidated by this process, don't have the software, don't have the time, whatever - if you are interested in comparing two speakers (and if they have SPL curves) just provide the names and models and I'll make an EQ curve for them and upload a sample of the two. Each time that I do this, the process becomes smoother and I get better at it. So send me some speaker part numbers and I'll give you comparisons |
|
#10
11-29-2009, 11:59 AM
| |||
| |||
| A mermber of another forum where I participate asked for a comparison between Jensen 12's, one with alnico magnet, one with more modern material. Making the EQ curves from the SPL measurements of each speaker, I didn't see notable differences. Perhaps younger ears will discern subtleties that I can no longer detect. The Jensen P12N is on the left channel, the C12N on the right: Click here to download 03 Track 3.mp3 |
|
#11
11-30-2009, 04:24 AM
| ||||
| ||||
| I love this idea about an emulation speaker. Jim Hall used the Gibson GA-50 amp. This amp has two alnico speakers, one 12" and one 8". And I hesitate to make me an extern cabinet for a 8" speaker. So, I would be curious to listen this match if it's possible... (p12r and p8r, I think). |
|
#13
11-30-2009, 12:27 PM
| ||||
| ||||
| Quote:
 ) that makes it distort in a smoother way compared to what a ceramic magnet would do. So to compare you would have to be looking more at speaker breakup. I hope someone on the forum knows more than I do, because I'm just repeating what I've heard. I'm not so interested in speaker breakup (I'm just not a Tweed guy) so I don't see the advantage to a big heavy AlNiCo magnet, but I know some people claim there's mojo involved. |
|
#14
11-30-2009, 12:51 PM
| |||
| |||
| Quote:
Click here to listen to 09.mp3 Last edited by randyc : 11-30-2009 at 01:41 PM. |
|
#15
11-30-2009, 12:55 PM
| |||
| |||
| Quote:
|
|
#16
12-01-2009, 02:24 AM
| |||
| |||
| Quote:
|
|
#17
12-01-2009, 02:44 AM
| ||||
| ||||
| Quote:
It's very interesting, the 8 inch speaker gives a melody more well-defined. Maybe a p8r for my christmas present... |
|
#18
12-01-2009, 12:17 PM
| |||
| |||
| nado64, I was happy to do it and the exercise only takes five minutes or so. I'm VERY glad that you think the comparison was useful. You are the first person that has a real purpose in mind when asking for a speaker comparison. (And I'm greatly encouraged that you clearly hear the differences between the speakers. For me, it's a simple computer exercise, I cannot detect any differences in the various speakers anymore )cheers, randyc |
|
#19
12-02-2009, 10:05 AM
| |||
| |||
| Hey Randyc, that's very clever "lateral thinking" I was surprised by the results - particularly the 12 and 8 inch speaker - the 8 seemed considerably louder even though you say the 12 is 5dB louder. Have you thought about getting your method marketed/patented? I could imagine speaker manufacturers would love to have such functionality added to their webpages and it would be great from a purchasers point of view
__________________ I play, therefore I am. |
|
#20
12-02-2009, 11:10 AM
| |||
| |||
| Quote:
No, I don't have any commercial plans. This kind of thing keeps me occupied and it's rewarding in many ways. At some point, I may collect the topics that are related and put them on a public file host, so that everything is in one place ... |
|
#21
12-02-2009, 04:53 PM
| |||
| |||
| Quote:
I suppose the answer, as in my last post, is in the distribution of the recorded material (or in the frequency response of your ears, the monitors with which you're listening, and so forth). Anyway, none of that is important, the entire point of the exercise is how YOU discern the differences in the speakers ! cheers, randyc |
Linear Mode
