Pooge,
I agree that the sound of a well built bass horn is nice, the impact of the bass is hard to describe and it not the same as a direct radiator. On the opposite hand it is hard to make a bass horn go down as deep as you can smoothly with a direct radiator, the slope or drop off of the low end is more accentuated with the limited horn size that is practical. I really don't have a lot of interest in the extreme low bass frequencies, I don't need that to listen to music, for a movie soundtrack it is different but for music anything down into the 35-45 hz range is satisfying to me. I think the average listener is happy with the old JBL bass bump at about 65hz and would think that is great bass. So you have to decide what it is you really want to listen to the music and not just talk about theoretical perfection or extreme bass that is surely going to **** off your next door neighbor as that is all they are going to hear and that surely isn't neighborly.
I agree that the sound of a well built bass horn is nice, the impact of the bass is hard to describe and it not the same as a direct radiator. On the opposite hand it is hard to make a bass horn go down as deep as you can smoothly with a direct radiator, the slope or drop off of the low end is more accentuated with the limited horn size that is practical. I really don't have a lot of interest in the extreme low bass frequencies, I don't need that to listen to music, for a movie soundtrack it is different but for music anything down into the 35-45 hz range is satisfying to me. I think the average listener is happy with the old JBL bass bump at about 65hz and would think that is great bass. So you have to decide what it is you really want to listen to the music and not just talk about theoretical perfection or extreme bass that is surely going to **** off your next door neighbor as that is all they are going to hear and that surely isn't neighborly.
I'm not sure I understand the question and so I am not sure what the answer is. The two - predictions vs. reality - will be different, I am not sure which one would be "as good of a result". That might depend on what you were looking for.
Webster generally predicts a greater acoustic load than what really happens - which one is "better"? I am not sure.
I don't know how these discussions get so diffuse. I entered the present discussion enquiring about POOH's statement about a crossover being too low, such that it caused a hole in the response. I inquired about why, and after another page of responses, it came down to simply the loading of the mid horn at its low end, i.e. below ~1000Hz, where the bass driver arguably could not adequately reach, as I understood the point being made.
Webster's equations were critized as being useless since they don't promote a constant directivity design throughout the frequency range, even though the constant directivity issue (over a wide frequency range) was not of concern in the particular range being discussed; but whether it is Webster's or Leach's math, the drop off at the low end is loss of resistive loading, which these "maths" do address. It was stated that loading isn't important since amplifier watts could eliminate the loss of loading as a concern, so to speak. That is one opinion. I have a differing opinion.
Constant directivity has been promoted as the Holy Grail, with anything less being inferior. Well, if that is true, why must the on-axis response be lowered at high frequencies in a constant directivity speaker so it isn't unpleasantly bright? This is at least one factor contrary to the notion that constant directivity, in itself, isn't the MOST overiding factor above all else, with anything less being inferior.
If wide polar response is desired for room coverage for widely seated positions, then fine. But I was once accused of being selfish if my priority leaned toward the best sound possible in the stereo seat rather than best sound over a wider seating position! (I wonder what a headphone user would be called!) Hell, I'd be happy if someone in my family gave a cr@p about fidelity. All this doesn't justify an attitude that anything less than constant directivity is, by definition, an inferior product not worthy of consideration.
Webster's equations were critized as being useless since they don't promote a constant directivity design throughout the frequency range, even though the constant directivity issue (over a wide frequency range) was not of concern in the particular range being discussed; but whether it is Webster's or Leach's math, the drop off at the low end is loss of resistive loading, which these "maths" do address. It was stated that loading isn't important since amplifier watts could eliminate the loss of loading as a concern, so to speak. That is one opinion. I have a differing opinion.
Constant directivity has been promoted as the Holy Grail, with anything less being inferior. Well, if that is true, why must the on-axis response be lowered at high frequencies in a constant directivity speaker so it isn't unpleasantly bright? This is at least one factor contrary to the notion that constant directivity, in itself, isn't the MOST overiding factor above all else, with anything less being inferior.
If wide polar response is desired for room coverage for widely seated positions, then fine. But I was once accused of being selfish if my priority leaned toward the best sound possible in the stereo seat rather than best sound over a wider seating position! (I wonder what a headphone user would be called!) Hell, I'd be happy if someone in my family gave a cr@p about fidelity. All this doesn't justify an attitude that anything less than constant directivity is, by definition, an inferior product not worthy of consideration.
"All this doesn't justify an attitude that anything less than constant directivity is, by definition, an inferior product not worthy of consideration"
Pooge,
That is a marketing term only, there is no such animal, even with a conic section I would seriously question the use of that term. I personally still like the sound of an exponential or hyperbolic horn that is designed well, you just have to decide what suits your needs.
Now when we are doing PA applications with multiple horns and have to cover large areas it is easier to do that is for sure with a conic section horn, but to me that is a special case. As you see it takes a very specific EQ to make those conic horns sound flat across the entire range that they work, just like we have had for standard Webster designed horns all along.
I'll say another thing about a major difference that you may be very aware of. If you walk across a constant directivity horn when you get to the edge of the projected angle you will notice the rapid change in response, where with a traditional exponential type horn it is much less noticeable when you get to the outer edge of the horn flare angle. So for that fact I actually personally would prefer the exponential horn sound. Just my opinion on that sound.
Pooge,
That is a marketing term only, there is no such animal, even with a conic section I would seriously question the use of that term. I personally still like the sound of an exponential or hyperbolic horn that is designed well, you just have to decide what suits your needs.
Now when we are doing PA applications with multiple horns and have to cover large areas it is easier to do that is for sure with a conic section horn, but to me that is a special case. As you see it takes a very specific EQ to make those conic horns sound flat across the entire range that they work, just like we have had for standard Webster designed horns all along.
I'll say another thing about a major difference that you may be very aware of. If you walk across a constant directivity horn when you get to the edge of the projected angle you will notice the rapid change in response, where with a traditional exponential type horn it is much less noticeable when you get to the outer edge of the horn flare angle. So for that fact I actually personally would prefer the exponential horn sound. Just my opinion on that sound.
Greebster,
I mentioned the pattern flip and was wondering if this was what was being referred to when it was stated that the phase changed on the wavelength while moving farther away from the mouth of a horn. I still see no function that would explain the phase inverting with distance, that made no sense.
I mentioned the pattern flip and was wondering if this was what was being referred to when it was stated that the phase changed on the wavelength while moving farther away from the mouth of a horn. I still see no function that would explain the phase inverting with distance, that made no sense.
Dunno where you got pattern flip from but it wasn't me.
Me either - I think it's a mass illusion
Pooge - you are entitled to your opinion on constant directivity (CD), but I think that all the data is against you. I certainly would never bother to design a loudspeakers that did not have CD over the widest feasible portion of its bandwidth.
But it is important to get the facts straight. When you say "the drop off at the low end is loss of resistive loading", that is not true. It is a factor but a relatively small one. The largest factor, by far, is the fact that the device is operating below resonance, i.e. compliance controlled, and hence its output is falling for a constant input. This is the dominant factor, not anything having to do with "loading".
It is pretty amazing. When you read through this little chapter Olson agreed with Geddes even though Geddes agreed with me (in respect to the lower range off the horn falling off beyond nearfield) yet Olson disagreed with me
It's pretty rare for a topic to stay on subject. People are always diverting it (deliberately and not) or they didn't understand what the topic was. I was addressing the claim that there would be a hole in the response between the woofer and the horn if the crossover were too low. That isn't always going to be the case, it can be designed out. The reasons given for this presumed hole have varied widely, but none of them, or so it seems to me, held water.
I don't think that is what I said and this is why discussions get so far off track. All I ever said was that I do not measure in the near field, how the field changes with distance was never discussed (and would be pointless since it is very complex). All I ever said was that one needed to measure away from the near field, which is about 1-1.5 meters for most horns. Olsen did refer to a test that was done that showed very little change from 1 meter out. I don't dispute that. Below 1 meter and the near field varies with distance AND angle and will differ significantly between different designs. It's best to just not have to worry about these problem by moving back.
I don't think that is what I said and this is why discussions get so far off track. All I ever said was that I do not measure in the near field, how the field changes with distance was never discussed (and would be pointless since it is very complex). All I ever said was that one needed to measure away from the near field, which is about 1-1.5 meters for most horns. Olsen did refer to a test that was done that showed very little change from 1 meter out. I don't dispute that. Below 1 meter and the near field varies with distance AND angle and will differ significantly between different designs. It's best to just not have to worry about these problem by moving back.
Yes, and the reason I brought it up is the originator of the thread was asked for details of the crossover and hasn't produced it after so many years. My point was maybe the system isn't done yet and maybe it would be easier to finish if the the crossover was bumped up higher. sure you can play with many vairables to get the BTA measuring better through the crossover region and keep the crossover low but in my experience that may not deliver the best performance. I've ran 15's higher than 1k with decent results but never thought of it as being something i could live with for very long.
I see you are selling active speakers now. Nice!
I see you are selling active speakers now. Nice!
I've followed this thread for awhile, as I have designed my system(concurrently and coincidently) similar to this format. Prior to following this long discussion, I purchased Gary's AE TD15M's to replace the JBL 2226H drivers I'd been using in many systems over the years. I've built many speakers, but my main rig project has gone from a four-way, to a three-way, to a two-way plus bass augmentation, with my thought process being a reduction of components has offered a simpler system to integrate optimally, but also a challenge to fully exploit what is possible. The vacuum tube powered, bi-amped TD15's and custom horn loaded AMT's are as engaging as anything I've encountered. I use a Marchand XM-44 to split signal, and have gone from an 8th order 1K, to an 8th order 500hz crossover point. The horn is a 2380 variant and seems to manage the lower crossover point without a response gap, but I'm still experimenting with much listening, as the ears have to be satisfied when the measuring equipment gets put away. I'm not sure the original posters ever intended a finished system, as we all seem to be on a constant journey for refinement and reinvention. Most all of this has been done before with fine results, but there's never been a better time to make old ideas new again, or at least make them better than what was previously possible. I too have thought about placing a nice midrange back into the system, but that would be yet another version of a previous system that I also enjoyed. For now, I'll soak up the experience and knowledge that is shared here and continue to enjoy the musical journey.
Kind Regards,
Jerrod
https://www.flickr.com/photos/jerrod_harden/
Kind Regards,
Jerrod
https://www.flickr.com/photos/jerrod_harden/
Having spend time on amplifiers, I am convinced optimum performance comes from integration of both amplifier and loudspeaker. Driving the speakers with a more constant current over the bandwidth provides much more desireable sound, which probably why tube amplifiers are desireable in many ways with a good output transformer.
I've heard more than one reason this might make a difference. Could this be amp related or speaker? (ie: making the speaker impedance consistent over frequency with a low Zout amp for a similar effect to just using a high source impedance?)
Reading Nelson Pass' treatise on current source amps shows an interest in the end response. Others have mentioned speaker distortions (motor related IIRC).
Basically you have rising impedance at Fs and the inductance impedance in almost all drivers. With a pure voltage driver, you are not going to be able to drive the same current at the higher frequencies. But with proper directivity and the equalisation, you can get adequate current through to achieve the response you look for. Basically if you equalise a CD wave guide, that is what you will get. To handle the Fs regions really is a more complicated issue with also involves the excursion characteristics.
I cannot recall the details of Nelson's report on current source amplification, but you also need to take into account how the amplifier response is when connected to the driver. I believe this information was not included because it could also show some deficiencies in amplifier performance under real driver loads.
I cannot recall the details of Nelson's report on current source amplification, but you also need to take into account how the amplifier response is when connected to the driver. I believe this information was not included because it could also show some deficiencies in amplifier performance under real driver loads.
This is my expericen too. Since I have experimented amps with defined output impedance (not current source, but things with DF<=1, normally tube amps), I never looked back.
I checked "the reality" it with modified "normal" amps (to make output impedance defined) always with good results (and with good impressions from my friends).
But one need to know the loudspeaker used to make the right impedance choice.
High amp output impedance or low, it matters not as long as this impedance is accounted for in the speaker design. Virtually all passive crossover speakers are designed assuming a very high DF. So when you change the amp and use a low DF amp with these speakers the designed frequency response - usually flat - becomes non-flat and as such will be highly audible. BUT ... this means that the "new" speaker (with low DF amp) is decidedly not accurate any longer. Sure one can say that they "prefer" this, but it is not Hi-Fi, it's something else.
I prefer to get "used to" known accurate sound and not let my sound listening basis to be tainted by a non-accurate system response.
I prefer to get "used to" known accurate sound and not let my sound listening basis to be tainted by a non-accurate system response.
With the normal use of crossover I fully agree, although some crossovers serve for the case, and others can be changed by adding, for example, RLC networks for the conjugate of the peak impedance (an additional task, anyway...). But I meant mainly with reference to the raw driver/ speaker itself, when connected directly to the amplifier (for example, in multi-amping or full-ranges). My practical experience with them suggests that, among other differences, treble and extreme treble (building on the case of a tweeter or full-range) seems less "sandy" or rough when powered defined impedance amplifiers, than if fed by 'conventional' amplifiers (or several coincidences will occur?). And in some cases, I noticed a smaller THD using lower DF, but I also realized that this depends largely on the speaker/motor/suspension used.
When I use a tweeter directly connected to the amplifier with active crossover functionally replicating the properties, I realize these changes *outside* of the crossover region. After all, 99% of tweeteres/HF drivers I know are used with a resistor attenuation for level matching, which basically causes the same effect than an defined impedance amplifier. With such a resistor it is difficult to assess the difference between the process.
An recent example: his weekend I tested one Kef Reference loudspeaker (the bookshelf one) with an amplifier with DF = 1, and because it has an cross designed for low Z (obviously), the result was ... ridiculous. But the far less fatiging treble will motivate me to change the crossover, if this box was mine... The treble level barely change, but the cross regions became an audibly mess, mainly between the woofer / midrange (an coaxial), and bass driver really need an high damping to not "boom". Maybe the internal tweeter resistor is too low and reveal the differences, or my DIY amp is far superior...
But anyway, it's only my still not very long experience and my 2 cents (and I maybe have made some mistakes), but enough so that I have taken this path (easy because I'm only an DIY without commercial issues). After all, I also realize the different perceptions between people lead to different ways, considering what else we like or hate. Since perception is an individual thing, I cannot do projects with another's perception, and vice versa. Fact is I HATE the normal amp harshness, it made me sick. An remark, sometimes I don't perceive certain differences claimed from another people, hence my question for perceptions.
My suggestion to the actual thread project is that if someone is building it is to test these DF conditions in order to know whether big drivers are also influenced by, or whether the perception of the designer tends to these types of detail/differences.
PS.: I have some means to measure acoustics, but in house the measurements needs to be gated short (for >300Hz).
When I use a tweeter directly connected to the amplifier with active crossover functionally replicating the properties, I realize these changes *outside* of the crossover region. After all, 99% of tweeteres/HF drivers I know are used with a resistor attenuation for level matching, which basically causes the same effect than an defined impedance amplifier. With such a resistor it is difficult to assess the difference between the process.
An recent example: his weekend I tested one Kef Reference loudspeaker (the bookshelf one) with an amplifier with DF = 1, and because it has an cross designed for low Z (obviously), the result was ... ridiculous. But the far less fatiging treble will motivate me to change the crossover, if this box was mine... The treble level barely change, but the cross regions became an audibly mess, mainly between the woofer / midrange (an coaxial), and bass driver really need an high damping to not "boom". Maybe the internal tweeter resistor is too low and reveal the differences, or my DIY amp is far superior...
But anyway, it's only my still not very long experience and my 2 cents (and I maybe have made some mistakes), but enough so that I have taken this path (easy because I'm only an DIY without commercial issues). After all, I also realize the different perceptions between people lead to different ways, considering what else we like or hate. Since perception is an individual thing, I cannot do projects with another's perception, and vice versa. Fact is I HATE the normal amp harshness, it made me sick. An remark, sometimes I don't perceive certain differences claimed from another people, hence my question for perceptions.
My suggestion to the actual thread project is that if someone is building it is to test these DF conditions in order to know whether big drivers are also influenced by, or whether the perception of the designer tends to these types of detail/differences.
PS.: I have some means to measure acoustics, but in house the measurements needs to be gated short (for >300Hz).