Hi,
the set of parameters certainly looks well suited for usage in a small dipole bass tower.
jauu
Calvin
the set of parameters certainly looks well suited for usage in a small dipole bass tower.
jauu
Calvin
There are a couple of questions remaining in my head concerning the bass unit.
A 51" tall linearray should behave as a line source down to approx 130Hz.
Would a snug fit against the floor make it 65Hz due to floor reflection?
And how would a dipole bass react to a active bass trap positioned against the wall behind the speaker?
A 51" tall linearray should behave as a line source down to approx 130Hz.
Would a snug fit against the floor make it 65Hz due to floor reflection?
And how would a dipole bass react to a active bass trap positioned against the wall behind the speaker?
Here's some opinion to the matter also: Frequently Asked Questions
Power compression in a dipole? Maybe a badly designed woofer in a very badly designed application regarding the needed Vd.
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Maybe I'm missing something in the discussion here but number crunching is always fun. 😉
Let's assume a typical Hi-Fi bass with SPL 90dB 1W/1m.
Dynamic headroom 20dB puts us at 110dB for a 90dB (A) listening level.
The driver must be able to handle at least 100W.
Enter the dipole sub...
At bass frequencies we can pretty much assume a dipole cancelation occuring?
Let's say we loose 6dB?
Now we need 400W! How many typical HiFi woofers are ready to put up with 400W?
Let's include a low Qts.
To make it easy on ourselves we can assume a 6dB EQ and hey, now we're at 1600W?
At this point a medium sensitive woofer and a low Qts is looking not so good.
My figures can be totally off, please correct me since I tend to mix things up. :/
Imho a medium to high Qts and a high sensitivity would make it a lot easier.
Let's assume a typical Hi-Fi bass with SPL 90dB 1W/1m.
Dynamic headroom 20dB puts us at 110dB for a 90dB (A) listening level.
The driver must be able to handle at least 100W.
Enter the dipole sub...
At bass frequencies we can pretty much assume a dipole cancelation occuring?
Let's say we loose 6dB?
Now we need 400W! How many typical HiFi woofers are ready to put up with 400W?
Let's include a low Qts.
To make it easy on ourselves we can assume a 6dB EQ and hey, now we're at 1600W?
At this point a medium sensitive woofer and a low Qts is looking not so good.
My figures can be totally off, please correct me since I tend to mix things up. :/
Imho a medium to high Qts and a high sensitivity would make it a lot easier.
The basic bass enhancing mechanism in high-qts woofer is that the motor system is weak and does not control the cone so well, thus the cone is able to move more than with a stronger motor (low-qts, or low-qes to be precise). More cone movement means more SPL, but imo not higher quality bass in this case.
It's pretty irrelevant in a dipole wether the cone movement is big due the weak motor (high-qts woofer) or due to the (quite little) extra current/power that is going through the coil (low-qts with eq), because the xmax is reached easily in both scenarios, with very modest power - and with medium to high quality woofers - without power compression.
Let me put it also this way that SPL in dipole is xmax-limited (due the fact that the woofer reaches it's xmax with modest power), not power-handling-limited. Thusly both woofer types are able to produce same amount of SPL in a dipole.
If one want's to have the the Q of 0,5 what Linkwitz suggested, it is easier to obtain by taking a 0,25-0,4 qts woofer and put it to a U-, H or W-frame (etc.), which rises the qts (qtd) to approx. 0,5. The amount the qts rises is the same in percentage that the Fs of the woofer drops due the air mass load, ie. a H-frame that lowers woofers Fs from 35Hz to 25Hz, rises woofer's qts from 0,35 to 0,49.
Do also read Linkwitz's opinion why he suggests low-qts woofers in a dipole (link is at my last post).
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Another little tidbit when you say overkill is that it takes displacment in order to get bass at a large SPL most everone translates this to Xmax.
Increasing Xmax also increases distortions (THD,IMD) so having more drivers lessens the requirement for large excrusions.
Thus reducing THD's and IMD's for a given level of SPL.
Some where I was reading about the added noise of the air flowing across the surface of the driver during large excursion.
But the most facinating thing I have learned through my years of messing with large and small systems is how much better the low frequency's sound and couple to the room better when the drivers are up off of the floor.
I will also do some test on this concept and I wil bet that two 2X8 dipole is probably all I will need for this room of 10.5' X 18.5' X 8' when setup 3' to 4' up from the floor at ear level when I am in my listening position.
But I will utilize all 6 in the end.
If this is the case then I can get rid of that big ole' stack of cabinets and have more room and make it look appealing aswell.
jer
Increasing Xmax also increases distortions (THD,IMD) so having more drivers lessens the requirement for large excrusions.
Thus reducing THD's and IMD's for a given level of SPL.
Some where I was reading about the added noise of the air flowing across the surface of the driver during large excursion.
But the most facinating thing I have learned through my years of messing with large and small systems is how much better the low frequency's sound and couple to the room better when the drivers are up off of the floor.
I will also do some test on this concept and I wil bet that two 2X8 dipole is probably all I will need for this room of 10.5' X 18.5' X 8' when setup 3' to 4' up from the floor at ear level when I am in my listening position.
But I will utilize all 6 in the end.
If this is the case then I can get rid of that big ole' stack of cabinets and have more room and make it look appealing aswell.
jer
Hi,
what use is a strong motor, if it can run? Reminds me of those Michelin-man looking bodybuilders who can´t move anymore because of their oversized muscles. 😛 I don´t worry about the driving force if the upper bandwidth limit of the naked driver is >5 times the desired working range.
Technically the best behaviour with regard to impulse and amplitude response is somewhere between 0.5 and 0.7. You can either force a lower-Qt driver with ´brute external power´ to perform a Q of 0.5-0.7 or You can have a higher-Qt driver just do the same on its own.
1) the involved frequencies are very low, so driving force is not the dominant factor of control over the moving system. Since a dipole requires high excursion capable drivers, this would lead to overly large sized, heavy, expensive and complex drive systems.
2) same response leads to same group delays. If I have to equalize the lower Q system to the response of a higher-Q system the GD will be the same in the end. The advantage of the low-Q system beeing less complex. The dominant part defining the GD is the HighPass-filter-function of the whole system. To achive the same amplitude response the electronic HP (i.e Subsonic-filter) for the low Qt-driver system needs to be of 1 order higher than for the high-Qt-system. Unfortunately the otherwise very elaborate work of SL does not explicitely mention this drawback of the low Qt system. The GD of dipoles is already the lowest of all systems (6ms and less), followed by CB and BR. An electronic HP-Filter may add dozens of ms of GD.
3) SL says that the low Qts driver needs more Equing. Compare examples 1 and 2 of the Link. The high Qts driver may get away with a simple 2nd-order-HP (1.5>Q>1) performing Subsonic- and EQ-filtering at the same, hence much less complexity and sensitivity to part tolerances.
Such simple filters are features of many subwoofer-amplifiers. The SL-correction most definitely is not, apart from amps featuring dsp-filters.
4) Using low-fs low-Qts drivers as SL suggests leads to such high values of needed correction, that the driver soon runs into its limits.
jauu
Calvin
what use is a strong motor, if it can run? Reminds me of those Michelin-man looking bodybuilders who can´t move anymore because of their oversized muscles. 😛 I don´t worry about the driving force if the upper bandwidth limit of the naked driver is >5 times the desired working range.
Technically the best behaviour with regard to impulse and amplitude response is somewhere between 0.5 and 0.7. You can either force a lower-Qt driver with ´brute external power´ to perform a Q of 0.5-0.7 or You can have a higher-Qt driver just do the same on its own.
1) the involved frequencies are very low, so driving force is not the dominant factor of control over the moving system. Since a dipole requires high excursion capable drivers, this would lead to overly large sized, heavy, expensive and complex drive systems.
2) same response leads to same group delays. If I have to equalize the lower Q system to the response of a higher-Q system the GD will be the same in the end. The advantage of the low-Q system beeing less complex. The dominant part defining the GD is the HighPass-filter-function of the whole system. To achive the same amplitude response the electronic HP (i.e Subsonic-filter) for the low Qt-driver system needs to be of 1 order higher than for the high-Qt-system. Unfortunately the otherwise very elaborate work of SL does not explicitely mention this drawback of the low Qt system. The GD of dipoles is already the lowest of all systems (6ms and less), followed by CB and BR. An electronic HP-Filter may add dozens of ms of GD.
3) SL says that the low Qts driver needs more Equing. Compare examples 1 and 2 of the Link. The high Qts driver may get away with a simple 2nd-order-HP (1.5>Q>1) performing Subsonic- and EQ-filtering at the same, hence much less complexity and sensitivity to part tolerances.
Such simple filters are features of many subwoofer-amplifiers. The SL-correction most definitely is not, apart from amps featuring dsp-filters.
4) Using low-fs low-Qts drivers as SL suggests leads to such high values of needed correction, that the driver soon runs into its limits.
jauu
Calvin
I'll give it another try.
At what frequency will a 51" tall line array stop behaving as a line array?
something like 130Hz (half wavelength corresponding to the height of the array) or maybe 65Hz with no air gap against the floor? (I'm thinking about floor reflections.)
At what frequency will a 51" tall line array stop behaving as a line array?
something like 130Hz (half wavelength corresponding to the height of the array) or maybe 65Hz with no air gap against the floor? (I'm thinking about floor reflections.)
I love kick in the chest, trousers a flappin'
Kick in the chest is felt in the frequency range 80-100 Hz
Quite a few box speakers have a (higher Q) peak around there
“Scoop” bass bin/ horns are plus 4- 6 db at these frequencies (or a little lower, depending on specifics)
Great for reggae, and power rock ~ over powerred
If your intended XO is active, you can put some EQ boost at 80-100 Hz
For passive XOs, use very high Q woofers, as Martin King does. My dipole woofers on order have a Qts of around 1.0
(But going active, I can still fine tune it more easily)
Kick in the chest is felt in the frequency range 80-100 Hz
Quite a few box speakers have a (higher Q) peak around there
“Scoop” bass bin/ horns are plus 4- 6 db at these frequencies (or a little lower, depending on specifics)
Great for reggae, and power rock ~ over powerred
If your intended XO is active, you can put some EQ boost at 80-100 Hz
For passive XOs, use very high Q woofers, as Martin King does. My dipole woofers on order have a Qts of around 1.0
(But going active, I can still fine tune it more easily)
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Mark
I was going to do an array, but found that a good 15 is more than enough
what are your SPL, Hz range and dB targets?
I was going to do an array, but found that a good 15 is more than enough
what are your SPL, Hz range and dB targets?
If I'm being optimistic my target is 110dB (A) peak and 90dB (A) average listening level.
Crossover will probably end up at 300Hz +/-50Hz.
SPL for the panel if I'm being optimistic again, 90 or maybe 93 dB 1W/1m?
Goal for the bass:
- Slam
- 60-80Hz low cross, I can use a sub below that
- Good integration with the panel.
Crossover will probably end up at 300Hz +/-50Hz.
SPL for the panel if I'm being optimistic again, 90 or maybe 93 dB 1W/1m?
Goal for the bass:
- Slam
- 60-80Hz low cross, I can use a sub below that
- Good integration with the panel.
The formulas for dipole dB are on SL's site, but I suspect that with 6.5 inch drivers, you would need about 12 or so
Just multiply out the Sd of X drivers . .
But you could get there much easier with a high Q 15 incher
Just multiply out the Sd of X drivers . .
But you could get there much easier with a high Q 15 incher
If you are prepared to be patient, I suspect your best option is Acoustic Elegance’s TD 15 LO, if they still have some(?).
Email John, and be prepared to follow up a lot, but they I think are likely best
Oh, budget per side?
Probably in Europe there are better value options, eg 18Sounds . .
Email John, and be prepared to follow up a lot, but they I think are likely best
Oh, budget per side?
Probably in Europe there are better value options, eg 18Sounds . .
Besides higher frequency, also the amount of excursion rises the cone's velocity. This however is not THE function of strong motor. It's the question how good the woofer controls it's cone near the Fs, how accurate the lows are.
As stated, low-qts woofer does not need that much eq, if at all, if H-, U- or W-frame is used because such an enclosure rises the total Q. Woofer with 0,3 qts can easily have a Q of 0,5 in a baffle. Besides the right Q, the bigger baffle allows more SPL because of bigger D.
I must ask why you want to take too high Q and a weak motor at the same time? Why not just take strong motor version and place it to such baffle that rises it's Q to 0,5-0,6? This way one can have all the goodies; strong motor with accurate lows, right total Q (= the need for eq is the same as with high-qts woofer) and better SPL capabilities due to the longer acoustic path difference (D).
Even if one opts to take a smaller frame (which leaves the Q to say 0,4) and thus would have to eq the response more than with high-qts-woofer, it's nearly not that bad that you say. Have you ever measured how much power a woofer needs in a dipole to reach it's full, soundwise usable xmax? I can tell you it's not much. The claim that power compression is a real threat with a low-qts woofer, but not with high-qts woofer, in a dipole, is a dead horses imo. Otherwise the used woofer just plainly sucks, to which I cannot say else than one should upgrade to a better woofer.
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How do we estimate by how much, placing drivers in such baffles that rises the driver's Q?
Cheers
Cheers
Here's some info: http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf
In short, calculate the air mass in all baffle's cavities and add ~60% of it to cone's mass and calculate the Fs again (air weights approx 1,2kg/m3 = 1,2g/liter). If the cavity is damped, I think the air mass is greater due to flow resistance. The qtc rises the same percentage that the Fs of the woofer drops. One can simulate the effect to Fs in WinISD for examle.
The same can be also done by adding some other mass to the cone.
This extra mass of course makes the low-qts woofer's motor "less strong" than before, so some of the benefits are lost. One has to find a good compromise; not too high qts and not too low either, and one does not have to fear the equalizer too much. Low-qts woofer's virtue is still good versatility, it is both low-qts woofer and high-qts woofer in same package, and can be put to every type of enclosure (CB, BR, horn, dipoles, cardioid). Good all-rounder (and can be used in many kinds of projects, if one ever thinks that there will be other projects 😉).
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Yes, I got the idea that 60% of it. It has been explained more thoroughly in that Martin J. King's paper.
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