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Do I need tweeters ta all?

74.182.27.248
Posted on October 16, 2010 at 08:25:10
Gandra1

Here are two Betsy K full range drivers I plan to place inside the t-line enclosure. I would like to stay with the original plan - where no tweeters are required. However, it looks like at the 10-12Khz (red line)the drop is significant. Will my 45 year old ears miss anything?

 

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RE: Do I need tweeters ta all?, posted on October 16, 2010 at 09:40:28
weltersys
Industry Professional

Posts: 685
Location: FL
Joined: September 28, 2004
 I would be more concerned about the 6 dB (or so) 3.5 K peak, where our ears are most sensitive, than the peak at 10K.
The 16K level is higher than 1K.

That said, one can get a response curve looking similar from compressed air coming out of a valve, the curve does not tell you what levels of distortion you will hear from the full range driver.

 

RE: Do I need tweeters ta all?, posted on October 16, 2010 at 11:52:07
tomservo
Manufacturer

Posts: 8210
Joined: July 4, 2002
 I liked Art's answer about air noise, he is correct too.

Assuming the speaker is otherwise behaved, you would still want to add at least one tank circuit to damp out that rise around 3200Hz. That bump will be audible, the same could be done for the bump around 10K, the cost is generally an R and L and C for each bump you smooth.

Also, an on axis response curve will describe what you hear on axis but often enough, one is hearing sound from off axis too. If the speakers had a similar HF response say 10 or 20 degrees off axis, then it would possibly make a nice speaker.
Best,
Tom

 

RE: Using the plain math, what values I am looking at..., posted on October 16, 2010 at 13:53:29
Gandra1
 ...regarding L,R,C? Still didn't hear any opinion on tweeters yet.

 

RE: Do I need tweeters ta all?, posted on October 16, 2010 at 13:55:22
Gandra1
Since you put it that way - I see it better now. However, should 11+ft of acoustic stuffing smooth out those bumps?

 

RE: Using the plain math, what values I am looking at..., posted on October 16, 2010 at 17:38:24
Saturntube
Manufacturer

Posts: 331
Location: Austin
Joined: April 21, 2006
 If it is a full range driver, most probably everything over that valley at around 5K is no good, cut it there and add a tweeter from 6k....
I like beyma Cp21f...or Raal.
JMHO

 

RE: Using the plain math, what values I am looking at...It depends, posted on October 16, 2010 at 18:19:30
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 The values totally depend on what the impedance is-at the freq of interest-not the "rating" of the driver.

The values will be different for 8 vs 12 vs 16 ohms.

 

RE: Do I need tweeters ta all?, posted on October 16, 2010 at 21:31:57
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 No, those high frequency bumps come from the whizzer and are not affected by what's behind the cone. However, they may or may not be highly directional, and hence may or may not be as audible as the on-axis plot shows. Unless there is more complete data available, I'd say you should listen to it for a while first. Initially a 3kHz bump will usually lend greater "presence" and liveliness to the sound. Eventually it will get tiring or annoying if it is too big a bump. At that point, if it happens, you can look into notch filters to remove it.

 

RE: Do I need tweeters ta all?, posted on October 18, 2010 at 05:27:20
thetubeguy1954
Audiophile

Posts: 6112
Location: Orlando, Fla
Joined: January 7, 2001



Hello Gandral,

Charts are nice and all to get an idea of what's happening, but the only real way to know if your 45 year old ears miss anything, will be to build the enclosures you want to use with those two Betsy K full range drivers. Then once you start playing music, in your room, via your equipment and listening to music with your ear/brain, that's when you'll know if your 45 year old ears miss anything!

I can tell you that I use Fostex FE208ES-R drivers ---{which weren't yet installed in photo above}--- and these almost 57 year old ears definitely missed things without adding tweeters to cover from 8Khz to 25Khz, but then again that's using my drivers in their enclosures, playing music, in my room, via my equipment and listening to music with my 57 year old ear/brain. Hope that helps...

Thetubeguy1954 (Tom Scata)

SETriodes Forum -- Central Florida Audio Society -- Fullrange Drivers
==============================================================
"The man that hath no music in himself nor is not moved with concord of
sweet sounds is fit for treasons, stratagems and spoils."
- William Shakespeare









Thetubeguy1954 (Tom)

Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers


 

RE: Do I need tweeters ta all?, posted on October 18, 2010 at 08:46:16
sunnysal
Audiophile

Posts: 845
Location: Central America
Joined: May 27, 2000
 IMHO I would add tweeters, you have attracted good answers so far, don't look to the curves to explain totally what you will or will not hear in your listneing room. I might add that these 49 year old ears still notice the lack "of air" when listening to my single driver speakers (fostex 208ES based), I think that some decent response to 18-20khz (or higher) is crucial to accurate music reproduction. YMMV. warm regards, Tony
Jean-Francois Lessard 2A3 PP amp
Marantz 7T Preamp
Klipschorns w/ALK xovers
Squeezebox Touch
Asus netbook running itunes and LMS feeding
MSB link DACIII w24/96k
MSB digital director
Technics M85 Cassette

 

RE: Do I need tweeters ta all?, posted on October 18, 2010 at 09:22:17
Godzilla.
Dealer

Posts: 1828
Joined: July 1, 2002
 I don't think you will need a tweeter. I own a pair of beautiful wizzerless Betsy's and enjoy them off axis. I've added a piezo with a 1uf cap + 8 ohm resistor to extend the high frequencies. Looking at the chart you posted i'd suggest listening to the speakers and playing around with toe in. If you like the sound off axis you can add a tweeter (perhaps a piezo with a .47 or .33 cap - don't forget the resistor across the piezo). You may like the sound without any tweeter at all... many do.

 

RE: Do I need tweeters ta all?, posted on October 18, 2010 at 11:41:41
Inmate51
 Whether or not you need tweeters depends on the quality of sound you want from your system. That is distinctly different from the sound you personally are able to hear and appreciate. Assuming that other people will also hear your system, you may wish to consider this aspect.

From the chart you posted, the system starts to go haywire at about 500-600 Hz, and really goes squirrelly at about 1.2 KHz.

Swings of 6-12 dB within a couple of octaves - or less, clearly color the sound and can create other problems if they are of narrower bandwidths and in certain frequency ranges.

Again from the chart you posted, I can't imagine why a person would use this driver above 400 Hz, if they're looking for high quality sound (depending on one's definition of "high quality").

Regarding your 45 year old ears: What your ears are able to hear can be easily measured by a competent audiologist. At age 45, I'd expect more-or-less reasonably good hearing, but with some upper frequency loss as compared to a 15 or 25 year old. Obviously, individuals vary, and previous exposure to frequent loud sounds (whether machinery or gunshots or whatever) over a long period of time will contribute to hearing loss. If your hearing is of concern to you, I'd recommend a thorough hearing exam, so you'll know "where you're at".

Just be glad that your ears aren't 57 years old, around the age when many males begin to notice some difficulty in hearing conversation in a noisy restaurant, and have a tendency to turn up the treble on the stereo when they want it to sound really "crisp and detailed".

I noted this paragraph from another poster:

"Charts are nice and all to get an idea of what's happening, but the only real way to know if your 45 year old ears miss anything, will be to build the enclosures you want to use with those two Betsy K full range drivers. Then once you start playing music, in your room, via your equipment and listening to music with your ear/brain, that's when you'll know if your 45 year old ears miss anything!"

I'd argue that a good hearing check-up is cheaper, less time-consuming and more accurate than building a pair of speaker enclosures and then attempting to self-diagnose what you are able to hear.

hth

 

RE: Using the plain math, what values I am looking at..., posted on October 18, 2010 at 12:50:06
tomservo
Manufacturer

Posts: 8210
Joined: July 4, 2002
 Hi

An exact solution requires the amplitude response and impedance curves as data files. Lacking that, using the plot's legend, an approximation would be;
.125 millihenry (1/8 mH)in parallel with 20Mfd polypropylene and in parallel with a 6 Ohm 10 W resistor. Those three parts in parallel are then put in series with your speaker.
If you want to raise the frequency you notch, reduce the C value a little, if you want a deeper notch, increase the R value.
Have fun
Tom

 

RE:Lots of good advices/opinons, thanks - I will soon post the *plan, posted on October 18, 2010 at 16:56:32
Gandra1
 ...from the vintage (80's) book on Loudspeaker Designs.

*plan for the enclosure

 

Tweeters and Enclosures for the BetsyK, posted on October 19, 2010 at 08:03:11
Paul J.
Manufacturer

Posts: 174
Location: Scottsbluff, NE
Joined: May 6, 2004



My ears are 31, and I get by fine without tweeters. When you look at the graph, keep in mind that what you see at 10K and 3.5K are humps/resonances in the response (that I think are less audible a little off axis). Compare 15K more to 6-7K (as a baseline), and you'll realize that extend fairly high. I think you actually get more extension than some big popular soft domes.

IME, most fullranger folks that use high frequency help do so as much to broaden the dispersion up high as to extend the absolute response (when it comes down to it, not a great deal happens above 15Khz). "Add some sparkle" if you will. Many also seem to enjoy the "phase-y" sound you get when a super tweeter is spaced well away from the fullrange driver. I don't dislike the addition of super tweeters, but I am perfectly happy without them. If you decide you need them, there are fairly inexpensive options.

Now, what enclosure are you thinking of? You know that the box needs to be perfectly tailored to the driver, and computer simulation has allowed "t-line" design to progress considerably in the last few years. I attached a pic of and link (sorry, its another forum, but it is the only place I have it posted) to a t-line/tqwt sort of thing for the BetsyK. I'd be happy to talk more ideal boxes and the need for tweeters anytime you want.

Paul
www.wildburroaudio.com

 

RE: This is what I 've been working on for Betsy-K, posted on October 19, 2010 at 10:08:36
Gandra1




Generic T-line - the size was determining factor.

 

Hmm., posted on October 19, 2010 at 10:41:00
Paul J.
Manufacturer

Posts: 174
Location: Scottsbluff, NE
Joined: May 6, 2004
 Did you run any computer models? How did you arrive at the dimensions? That isn't much box volume for the BetsyK. Is the path the same depth in each fold, or does it contract? Do you know the path cross sectional area and length off hand? I could toss the numbers into Horn Response for you to get some idea of how it will behave.

Paul

 

RE: Hmm., posted on October 19, 2010 at 22:41:37
Gandra1
The "pipes" are uniformly 3.5". Th bends will have ceramic tiles, at the 45°, and spaces filled with concrete. The length of 11+' will be filed with the acoustic foam.

The instructions? From the vintage Vivian Capel's book "Loudspeaker design." T-line for the full range driver(s) with the similar spec's to his, in his example.

 

It might work., posted on October 20, 2010 at 09:31:10
Paul J.
Manufacturer

Posts: 174
Location: Scottsbluff, NE
Joined: May 6, 2004
 I plugged it into Horn Response, which isn't the perfect tool for such a thing. But, I think I can interpret the results well enough. My biggest worry is the giant suckout at 100hz. I think a great deal will depend on stuffing. Were I you, I'd rig a way to listen to it without attaching the final side. Thick weatherstrip and clamps. Then play with stuffing: density and placement.

You probably won't like this idea, but I'd also skip the tile and concrete. First, you need all the box volume you can get. Second, those corners will help to keep midrange frequencies from traveling down the line, which in my mind is quite desirable. You don't want midrange coming out of the terminus if you can avoid it. The bass that you are trying to reinforce with the line won't care a bit about the reflectors. The wavelengths we're talking about are too long to be affected either way, so better to have volume and midrange filtering. At the very least don't worry about the tile until you've made certain that the box will suit your needs (by clamping a side on and listening).

Finally, let me know your results! I sure would appreciate some pics over on my forum. And if this little box works well, I bet others will be interested in duplicating it.

Paul

 

RE: It might work., posted on October 20, 2010 at 13:49:26
Gandra1
Thanks Paul, I sure will keep you posted about the findings - I am relieved I wont have to use concrete and tiles. :)

 

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