Not so sure about that. Tuning and all the harmonics are directly related to the enclosure itself, not the driver or the driver location. Putting the driver in different spots might light up the peaks differently but it can't change tuning or the location of the peaks.
Looking at measurements of dual driver THs on DSL and data-bass, the peaks look pretty well defined, not blurred at all.
One of the first things I ever learned when I started learning about transmission lines is that you could move the driver around to get rid of peaks and dips by illuminating them differently by driver location. This does not change where the harmonics are for the most part, it only changes how the driver interacts with them. Sure, the impedance changes a bit but the harmonics don't really move around much. This is a very common tweak, common driver positions for transmissions are .217 and .414 x line length, those positions can provide much smoother response than putting the driver right at the closed end of the line.
Here's a quick pic.
In this random tapped horn I changed L45 from 36 to 75 cm. Even though that's a massive change in driver position, and even though that also changes the shape of the line somewhat (I forgot to change S4 to Auto and I'm not redoing the pic) the peaks are still in the same places and they are not blurred.
If you start making massive changes, like moving the driver 100 cm or more, you can make some pretty significant changes to response and impedance, but what we are talking about here is the comment that having the drivers offset by their physical distance of a few inches would blur the tuning and peaks. For the purposes of this question the practical answer is that having drivers offset by their physical distance is not going to blur the tuning and peaks.
Here's a quick pic.
An externally hosted image should be here but it was not working when we last tested it.
In this random tapped horn I changed L45 from 36 to 75 cm. Even though that's a massive change in driver position, and even though that also changes the shape of the line somewhat (I forgot to change S4 to Auto and I'm not redoing the pic) the peaks are still in the same places and they are not blurred.
If you start making massive changes, like moving the driver 100 cm or more, you can make some pretty significant changes to response and impedance, but what we are talking about here is the comment that having the drivers offset by their physical distance of a few inches would blur the tuning and peaks. For the purposes of this question the practical answer is that having drivers offset by their physical distance is not going to blur the tuning and peaks.
You can't simulate the blurring of the peaks. The "blurred" response is the average of the two separate driver locations. Which in case of 15" drivers will give a 3 - 5 Hz difference in higher cut off location. This in turn will cause a rounding of the higher peak (or a blur).
In post 4 you state that driver location doesn't change the tuning, in post 6 you state that it does change the tuning by a little, now I call that progress
And to be honest, you seem to be the kinda person that rather writes a lenghty response than stand corrected (it takes one too know one), so I'm going to do a little victory dance over here.
Best regards
In post 4 you state that driver location doesn't change the tuning, in post 6 you state that it does change the tuning by a little, now I call that progress
And to be honest, you seem to be the kinda person that rather writes a lenghty response than stand corrected (it takes one too know one), so I'm going to do a little victory dance over here.
Best regards
Sure you can simulate it just fine. Use Akabak and sim the drivers as individuals instead of one driver. In this case I really don't think it's worth the bother. Two drivers separated by a few inches absolutely will behave differently than a single driver but it's nothing to get excited about. And if you check the measurements on DSL and data-bass there's absolutely no blurring of any peaks. The peaks are just as sharp as single driver measurements.
In post 4 you state that driver location doesn't change the tuning, in post 6 you state that it does change the tuning by a little, now I call that progress
And to be honest, you seem to be the kinda person that rather writes a lenghty response than stand corrected (it takes one too know one), so I'm going to do a little victory dance over here.
Best regards
Anytime you change anything it's going to change the impedance, I'm not sure if that's worth doing a dance.
I write lengthy responses because that's what it takes to fully explain what I'm talking about.
I truly invite you to find ANYTHING I've EVER said that was incorrect and we can discuss it. (That doesn't imply I was never wrong, just that I am willing to discuss any occasion I've ever been wrong.)
If I was incorrect and you can prove it, I always admit it. Don't believe me? Do a keyword search with my username and the words "wrong", "sorry", "mistaken", etc, and you will find that I admit I'm wrong far more than the vast majority of people on forums. I absolutely love being wrong, it gives me an opportunity to learn something new, and I always admit when I'm wrong.
Go ahead. Prove me wrong. I dare you.
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Let's try this one more time and only discuss the technical issues, not personality or posting style.
If you are talking about amplitude being blurred, I would agree 100 percent. In fact that's exactly what my picture shows and it's exactly what I described when I said different driver positions illuminate the harmonics differently. The harmonics don't move but the different driver positions light them up in different ways.
But if you are talking about frequency of the peaks being blurred (and that's exactly what Chris was talking about when he talked about tuning shifting and top end mush being easier to cross over) than I have to disagree. My picture clearly shows none of that happening.
I never said tuning would shift, I said impedance changes. Here's proof. This is the excursion graph of the tapped horn shown above. The excursion graph shows tuning most clearly, I think. This time I moved the mouth side driver tap over 100 cm and tuning remains exactly the same. All the blips in the excursion graph are in the same spot regardless of driver position. That's because the harmonics are still in the same spot regardless of where the driver is.
The impedance graph is quite a bit different, as you would expect when you move the driver more than a meter down the line but the harmonics are all in the same spot. Tuning doesn't change. Peaks don't shift in frequency, only in amplitude.
I'm happy to post detailed proof of any statement I make. Always. Don't imply I'm trying to weasel around issues with long posts. If I'm wrong I'll admit I'm wrong.
If you are talking about amplitude being blurred, I would agree 100 percent. In fact that's exactly what my picture shows and it's exactly what I described when I said different driver positions illuminate the harmonics differently. The harmonics don't move but the different driver positions light them up in different ways.
But if you are talking about frequency of the peaks being blurred (and that's exactly what Chris was talking about when he talked about tuning shifting and top end mush being easier to cross over) than I have to disagree. My picture clearly shows none of that happening.
I never said tuning would shift, I said impedance changes. Here's proof. This is the excursion graph of the tapped horn shown above. The excursion graph shows tuning most clearly, I think. This time I moved the mouth side driver tap over 100 cm and tuning remains exactly the same. All the blips in the excursion graph are in the same spot regardless of driver position. That's because the harmonics are still in the same spot regardless of where the driver is.
The impedance graph is quite a bit different, as you would expect when you move the driver more than a meter down the line but the harmonics are all in the same spot. Tuning doesn't change. Peaks don't shift in frequency, only in amplitude.
An externally hosted image should be here but it was not working when we last tested it.
I'm happy to post detailed proof of any statement I make. Always. Don't imply I'm trying to weasel around issues with long posts. If I'm wrong I'll admit I'm wrong.
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This is a good exercise to do in Akabak. Do a full model with separate drivers where in a TH the tap and throat positioning for both will be different. you'll see some interesting things. The overall response of the subwoofer and the voltage sensitivity of the sub will be close to splitting the difference of the placements in HR but if you dig deeper and start looking at things like individual driver excursion, impedance, loading and the forces seen by each cone you'll see it does not match the simple method in HR and you'll lose what can be a not insignificant amount of output near the driver excursion maximums.
I guess it comes down to semantics. If tuning is synonymous with excursion minima, I believe your right with the statement that tuning doesn't change. If it's not then not.
I always thought tuning is synonymous with how it sounds, so that it incorporates phase, impedance and frequency response (those are all over the place).
Regardless:
I've seen the higher peak (cut off) of a tapped horn change as much as 20 Hz with a change of 50 cm. Completely different sound, completely different excursion behaviour, yet the same excursion minima as before.
I can't seem to put my head around the fact that you would make a broad statement based upon a single simulation. As an educated guess, the reason you see so little change in your simulation, is because of the relatively high cross sectional area. The cross sectional area of most of my simulations is around 50 cm^2.
First things last, I'm not talking about harmonics here and never was. This is probably my last reply in this topic, so don't expect an answer after this. No hard feelings.
Best regards Johan
I always thought tuning is synonymous with how it sounds, so that it incorporates phase, impedance and frequency response (those are all over the place).
Regardless:
I've seen the higher peak (cut off) of a tapped horn change as much as 20 Hz with a change of 50 cm. Completely different sound, completely different excursion behaviour, yet the same excursion minima as before.
I can't seem to put my head around the fact that you would make a broad statement based upon a single simulation. As an educated guess, the reason you see so little change in your simulation, is because of the relatively high cross sectional area. The cross sectional area of most of my simulations is around 50 cm^2.
First things last, I'm not talking about harmonics here and never was. This is probably my last reply in this topic, so don't expect an answer after this. No hard feelings.
Best regards Johan
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I think tuning is always regarded as the midpoint between the two lowest impedance peaks, which is going to correspond to the excursion minima. Looking at the excursion graph makes it really quick and easy to see what the tuning is.
If you have a personal definition of tuning that is different than the formal definition I suppose that's fine and it would be just a matter of semantics. But you can't expect anyone to realize you define tuning different than everyone else unless you explain it from the beginning.
I'm not making a broad statement based on a single sim. I showed a simple sim because it illustrated my simple point in a simple way. Here's another way to look at it.
An externally hosted image should be here but it was not working when we last tested it.
That's the first graph in all of MJK's worksheets, it shows acoustic impedance for the enclosure. This never changes, regardless of where you put the driver. Even if there is no driver this graph doesn't change. This is the enclosure analysis and it has nothing at all to do with the driver.
Once you start adding drivers and moving them around in relation to the enclosure, the impedance, response, and everything else changes but the acoustic impedance of the enclosure NEVER changes, and the changes made by driver location are dictated by the enclosure acoustic impedance. In other words, the harmonics are always in the same spot, so in general the peaks and dips in response will also be in the same spot regardless of driver location. Because of how phase (reflections off the closed end) interacts with the enclosure acoustic impedance, peaks can turn into dips and can change the shape and q of the low knee somewhat but the harmonic spikes are dictated by acoustic impedance and they don't ever move. So they can "blur" in amplitude but not in frequency.
In other words, the peaks don't move in frequency. The low knee might look like it's shifting in frequency by a couple of hz and you might assume tuning was changing if you don't know what you are seeing but it's just the q changing. The peak isn't changing location, it's just not a peak when it's low q, and becomes a visible peak when the q changes. Tuning doesn't change, it remains exactly in the same spot.
And I can probably explain this in a few other ways if you like too. Please don't imply I'm making a wild guess based on a single sim. If you don't like the way I've explained something ask a question, don't imply I looked at a single picture and made something up.
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