I cannot buy any of the usual suspects open baffle drivers like the Eminence 15A or goldwoods here in Thailand.
I did however fell in love with this driver:
HOME ||nanovaspeaker.com
I am very new to OB but know about the different QTS schools. Many claim we need very high QTS, others claim sensitivity/efficiency is important.
This driver is 98dB sensitive, 4.2% efficient but QTS is only 0.40.
Would this driver do well in a passive OB? And if so why? I would like to understand this better.
I did however fell in love with this driver:
HOME ||nanovaspeaker.com
I am very new to OB but know about the different QTS schools. Many claim we need very high QTS, others claim sensitivity/efficiency is important.
This driver is 98dB sensitive, 4.2% efficient but QTS is only 0.40.
Would this driver do well in a passive OB? And if so why? I would like to understand this better.
It will work but since you are a bit from ideal Qts of 0,7 you have to do some extra EQ except from the usual dipole compensation of 6dB/oct.
So you need an active crossover HP filter at 20 Hz, and a LP filter at 100Hz (example) then you need to have Dipole compensation that has a slope of 6dB/octave with increasing of the output at lower frequency, and addition to this compensate for the low Qts.
You will get more information on Linkwiz homepage, R:I
LS
Electro-acoustic models
C3 explains more.
So you need an active crossover HP filter at 20 Hz, and a LP filter at 100Hz (example) then you need to have Dipole compensation that has a slope of 6dB/octave with increasing of the output at lower frequency, and addition to this compensate for the low Qts.
You will get more information on Linkwiz homepage, R:I
LSElectro-acoustic models
C3 explains more.
I was wondering myself too...why no X-max? That seems to be one of the most basic specs.....
But in thailand many vendors don't even have any specs. They have no idea what they are selling. No more info than 300w 15".....not even sensitivity
You might also look at ...........
SB Acoustics :: 12” SB34NRX75-16
You will need two of these per channel and connected in parallel to give you sufficient cone area and sensitivity, X max is very good too. These are made for purpose, though a little expensive.
C.M
SB Acoustics :: 12” SB34NRX75-16
You will need two of these per channel and connected in parallel to give you sufficient cone area and sensitivity, X max is very good too. These are made for purpose, though a little expensive.
C.M
So would i be better off using 2 of these 10" drivers for each side for a passive OB? HOME ||nanovaspeaker.com
These have Qts 0.71....but again no published X-max........
If i use 2 I gain about 3dB sensitivity to get 95dB
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These Nanova drivers are sold by many vendors, some even pop up on Lazada/Shopee. If you find a driver you like on the nanova website just google the model number and usually a few vendors pop up.
If I end up buying one I will post my impressions here. From the pictures they look reasonably well made and they are very affordable.
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The largest SB Acoustics driver sold in Thailand is only 6". It is a bit of a HiFi ghetto here....
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With Open Baffle design, Xmax is very quickly used up and low frequency distortion becomes an issue. Added to that when equalization is applied the end result can be an overdriven driver at moderate volume levels. With music OB design is fine but with home theatre OB bass needs a powered Sub woofer to help with those low thumps.
One has to define their target ( music or H.T ) before spending those big dollars on drivers, and is best spent on those drivers designed for the purpose. In my opinion, cone area Sd is more important than Xmax in OB design although both work together to give the final result. It is just that Xmax is used up so easily if the design is inadequate.
C.M
One has to define their target ( music or H.T ) before spending those big dollars on drivers, and is best spent on those drivers designed for the purpose. In my opinion, cone area Sd is more important than Xmax in OB design although both work together to give the final result. It is just that Xmax is used up so easily if the design is inadequate.
C.M
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The more I read the more confused I get. Everyone keeps telling me I need high qts but then i read many accomplished builders saying they prefer <0.5Qts drivers. Troels Gravesen uses drivers around 0.25Qts with passive filters and I just read this from LinkwizLab:
A34 - The low frequency roll-off of a woofer and its associated group delay are optimal, from what I have observed, when they follow the response of a 2nd order highpass filter with Q = 0.5. When a driver is mounted in a dipole W-frame or H-frame its mechanical resonance frequency Fs decreases to Fd, due to air mass loading, and Qts increases by a similar percentage to Qtd.
For example, a driver with very strong motor, Fs = 18 Hz and Qts = 0.2 might have Fd = 16 Hz and Qtd = 0.22 as determined from an impedance measurement of the baffle mounted driver. With Qtd < 0.5 the low frequency behavior of the woofer is characterized in the complex s-plane by real axis poles at -69 Hz and -3.7 Hz and by 3 zeros at the origin. One of these zeros is due to the front-to-back dipole cancellation with its 6 dB/oct low frequency roll-off. The frequency response of this 3rd order acoustic highpass filter must be equalized to obtain a flat response. A suitable target response could be Fd = 20 Hz and Qtb = 0.5. It is easily realized with two shelving lowpass filters. The first filter with a pole at 20 Hz and a zero at 69 Hz corrects for the low Qts of the driver. The second filter with a pole at 20 Hz and a zero at 400 Hz compensates the 6 dB/oct roll-off due to dipole cancellation. The 3.7 Hz pole is low enough in frequency so that the response is dominated by the 2nd order roll-off below 20 Hz. An advantage of a low Qts driver is the ease with which it can be equalized for an optimum response with Q = 0.5.
A driver with a smaller motor might give Qtd = 0.7 and Fd = 20 Hz, which leads to a pair of complex poles in the s-plane. This can be readily changed to a 3rd order Bessel highpass response by using a shelving lowpass filter with a pole at 20 Hz for the necessary dipole roll-off compensation.
Likewise, if Qtd = 1 and Fd = 20 Hz, then an additional pole at 20 Hz, from the dipole equalization, leads to a 3rd order Butterworth acoustic highpass response. Third order filters introduce more group delay than 2nd order ones. It is therefore advantageous to use Qts < 0.5 drivers, even when they require driver roll-off equalization in addition to the normal 6 dB/oct dipole correction.
But I am not smart enough to completely grasp everything they say though.
A34 - The low frequency roll-off of a woofer and its associated group delay are optimal, from what I have observed, when they follow the response of a 2nd order highpass filter with Q = 0.5. When a driver is mounted in a dipole W-frame or H-frame its mechanical resonance frequency Fs decreases to Fd, due to air mass loading, and Qts increases by a similar percentage to Qtd.
For example, a driver with very strong motor, Fs = 18 Hz and Qts = 0.2 might have Fd = 16 Hz and Qtd = 0.22 as determined from an impedance measurement of the baffle mounted driver. With Qtd < 0.5 the low frequency behavior of the woofer is characterized in the complex s-plane by real axis poles at -69 Hz and -3.7 Hz and by 3 zeros at the origin. One of these zeros is due to the front-to-back dipole cancellation with its 6 dB/oct low frequency roll-off. The frequency response of this 3rd order acoustic highpass filter must be equalized to obtain a flat response. A suitable target response could be Fd = 20 Hz and Qtb = 0.5. It is easily realized with two shelving lowpass filters. The first filter with a pole at 20 Hz and a zero at 69 Hz corrects for the low Qts of the driver. The second filter with a pole at 20 Hz and a zero at 400 Hz compensates the 6 dB/oct roll-off due to dipole cancellation. The 3.7 Hz pole is low enough in frequency so that the response is dominated by the 2nd order roll-off below 20 Hz. An advantage of a low Qts driver is the ease with which it can be equalized for an optimum response with Q = 0.5.
A driver with a smaller motor might give Qtd = 0.7 and Fd = 20 Hz, which leads to a pair of complex poles in the s-plane. This can be readily changed to a 3rd order Bessel highpass response by using a shelving lowpass filter with a pole at 20 Hz for the necessary dipole roll-off compensation.
Likewise, if Qtd = 1 and Fd = 20 Hz, then an additional pole at 20 Hz, from the dipole equalization, leads to a 3rd order Butterworth acoustic highpass response. Third order filters introduce more group delay than 2nd order ones. It is therefore advantageous to use Qts < 0.5 drivers, even when they require driver roll-off equalization in addition to the normal 6 dB/oct dipole correction.
But I am not smart enough to completely grasp everything they say though.
I only use it for music and don't listen at extremely loud levels anyway. All i need is getting to let's say 40Hz at moderately loud levels.
My idea is a 60cm baffle with one 15" or 2 10" drivers with an array of 4 TC9FD drivers above it on a 10 cm wide baffle. I already have 8 Peerless TC9FD drivers and 8 TC5FB00 dipole drivers as tweeters for better HF dispersion. All with passive crossovers.
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Confusion....
Ericknils.... The 15" you reference is basically a pro audio mid range that, if it does meet the stated specifications, would make a nice pro audio vocal (PA) woofer application. Can you use it as an OB woofer... well maybe. The FS is too high and the Xmax, given the stated efficiency is like around 2.5 MM peak.
You would be buying capabilities that are of little use as an OB woofer.
P Audio is there in your country so I would assume most of their products would be available there... have you investigated them? Unless you have already purchased the woofer you posted, you would be way better off looking for a woofer better suited for OB applications. Are your intending to make a passive OB system, or active?
Ericknils.... The 15" you reference is basically a pro audio mid range that, if it does meet the stated specifications, would make a nice pro audio vocal (PA) woofer application. Can you use it as an OB woofer... well maybe. The FS is too high and the Xmax, given the stated efficiency is like around 2.5 MM peak.
You would be buying capabilities that are of little use as an OB woofer.
P Audio is there in your country so I would assume most of their products would be available there... have you investigated them? Unless you have already purchased the woofer you posted, you would be way better off looking for a woofer better suited for OB applications. Are your intending to make a passive OB system, or active?
There is a Lavoce distributor in Thailand: Single Product |
Not sure about the X-max of the driver i linked, but at least they have a range of 12, 15, 18 inch drivers. With low and high Qts and known X-max. Don't forget to look at the bassguitar section, some of these are made for open baffle. Sica Jensen is sold in Vietnam. I really don't know how easy or hard it is to get parts from Vietnam to Thailand. But some of these are pretty good and budget drivers and TSP's as x-max etc are known: Distributors
Not sure about the X-max of the driver i linked, but at least they have a range of 12, 15, 18 inch drivers. With low and high Qts and known X-max. Don't forget to look at the bassguitar section, some of these are made for open baffle. Sica Jensen is sold in Vietnam. I really don't know how easy or hard it is to get parts from Vietnam to Thailand. But some of these are pretty good and budget drivers and TSP's as x-max etc are known: Distributors
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