Question regarding use of an 18" or larger Bass unit in a "Transmission line" enclosu
Question regarding use of an 18" or larger Bass unit in a "Transmission line" enclosure?
I am partially influenced by the PMC which uses the 15" Volt (RV3363) in the large BB5 system, which has an fs of around 29Hz. It has a claimed response down to 17Hz, I assume in room.
The line length is effectively 4m or 13' according to PMC the actual physical length is a bit shorter at just under 3m. Using 1/4 wave criteria works out at approx 2.9m, so close.
I am considering the bigger Volt RV4564 which has a resonance of approx 26Hz which would offer greater performance than the BB5.
Based on the BB5 specs 1/4 wave comes out at 3.3m (PMC effective length = 4.6m)
Likely response using PMC criteria could indicate response in room to 15Hz or even a little lower.
This would make for a very large cabinet which would not be an issue for me, but I would be very interested to learn if anyone has built a big TL using an 18" or larger driver.
There was one project which used a Hartley 24" some years ago.
Possible drivers include those with QTs > 0.3 or so
Volt RV4564 18"
Beyma 18PWB1000Fe 18"
Precision Devices PD186/2 18"
Precision Devices PD/N18BR40 18"
21PW1400Fe 21"
My aim is to achieve 16Hz bass extension, if the box size approaches 800 litres so be it!!
Thanks,
Simon
Question regarding use of an 18" or larger Bass unit in a "Transmission line" enclosure?
I am partially influenced by the PMC which uses the 15" Volt (RV3363) in the large BB5 system, which has an fs of around 29Hz. It has a claimed response down to 17Hz, I assume in room.
The line length is effectively 4m or 13' according to PMC the actual physical length is a bit shorter at just under 3m. Using 1/4 wave criteria works out at approx 2.9m, so close.
I am considering the bigger Volt RV4564 which has a resonance of approx 26Hz which would offer greater performance than the BB5.
Based on the BB5 specs 1/4 wave comes out at 3.3m (PMC effective length = 4.6m)
Likely response using PMC criteria could indicate response in room to 15Hz or even a little lower.
This would make for a very large cabinet which would not be an issue for me, but I would be very interested to learn if anyone has built a big TL using an 18" or larger driver.
There was one project which used a Hartley 24" some years ago.
Possible drivers include those with QTs > 0.3 or so
Volt RV4564 18"
Beyma 18PWB1000Fe 18"
Precision Devices PD186/2 18"
Precision Devices PD/N18BR40 18"
21PW1400Fe 21"
My aim is to achieve 16Hz bass extension, if the box size approaches 800 litres so be it!!
Thanks,
Simon
Recent discussions on sub forum about how low do you need to go. There are some advocates of 32 Hz, even organ music fans, and some, perhaps home theatre users, who seem to aim for 10 Hz.
16 Hz is quite ambitious. Are you a disaster-movie enthusiast or an acoustic music fan?
Certainly eye-opening to do a RTA (real time analysis fast Fourier....) on the sounds you want to reproduce to see if there is any content below 35 Hz.
For me, the less box the better the sound.
B.
16 Hz is quite ambitious. Are you a disaster-movie enthusiast or an acoustic music fan?
Certainly eye-opening to do a RTA (real time analysis fast Fourier....) on the sounds you want to reproduce to see if there is any content below 35 Hz.
For me, the less box the better the sound.
B.
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bentoronto,
Classical organ is one of my main musical diets. Interestingly many instruments vary, I prefer the Willis Organs with a richer low bass, many French classical instruments tend to be somewhat drier in the bass.
I have built systems in the past using smaller drivers (12 & 15") capable of 16Hz in room, the benefits of which, when well executed manifest themselves in greater musical reality. When there in the recording (alas all to rare) to feel real bass pressure loading the room can be revelatory when well done.
Some say that bandwidth to 5Hz is beneficial as well. I have built in my 20s a pair of equalised sealed subs with this kind of bandwidth as an experiment, this produced interesting results some of which not so desirable!!
Poor alignments with 30Hz capability let alone 16Hz result in musical disaster; there are all too many such commercial examples out there!
My next move is to have this extended bandwidth, but at a higher output / performance level. Hence the 18" or 21" drivers.
Classical organ is one of my main musical diets. Interestingly many instruments vary, I prefer the Willis Organs with a richer low bass, many French classical instruments tend to be somewhat drier in the bass.
I have built systems in the past using smaller drivers (12 & 15") capable of 16Hz in room, the benefits of which, when well executed manifest themselves in greater musical reality. When there in the recording (alas all to rare) to feel real bass pressure loading the room can be revelatory when well done.
Some say that bandwidth to 5Hz is beneficial as well. I have built in my 20s a pair of equalised sealed subs with this kind of bandwidth as an experiment, this produced interesting results some of which not so desirable!!
Poor alignments with 30Hz capability let alone 16Hz result in musical disaster; there are all too many such commercial examples out there!
My next move is to have this extended bandwidth, but at a higher output / performance level. Hence the 18" or 21" drivers.
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Most years I bring my SPL meter to the Phantoms of the Organ event.* **
"Phantoms of the Organ" Halloween bash
Maybe this year I'll bring REW and do an RTA.***
B.
*Big Cassavant, biggest in Canada
**brought the SPL meter to Brahms' "requiem" last week, 95 dB(C) fast, as posted elsewhere.
*** Oct 31, don't miss it
Should that lead your thread to loudness as well as FR? After all, with restrained loudness goals and bass extension goals, you have greatly reduced air-movement requirements. Which in turn speaks to your enclosure choices. Or vice versa.
With 95dBC in the concert hall and not louder on Halloween organ music*, do you think the (mostly car sound) enthusiasts who test north of 120dB really are just people with a hearing-death-wish?
Granted, we play "classical" music at home a few dB louder than at concerts. I sometimes hit 100.
B.
*Do you remember that silly theme Alfred Hitchcock used on TV? It is called "March of..." something or other. Really swell played on the pedals.
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What is the intended use of this TL?
If hi-fi use, a TL 15 will do, a simpler project would be an OB 31'':
Fostex FW800HS, 31.5" Super Woofer
If hi-fi use, a TL 15 will do, a simpler project would be an OB 31'':
Fostex FW800HS, 31.5" Super Woofer
QW designs, TL, ML, QW-pipes
Hi there: Try M-H Audio calculations page for several types of QW enclosures. Play around with all of them to get the capabilities of each, then plug in various drivers to see how they meet your needs. I always start with sealed followed by vented enclosure designs, as a guide. If you have used Horn Response, you will see that sufficient Xmax is necessary for low bass response at moderate to high SPL response, ... regards, Michael
Hi there: Try M-H Audio calculations page for several types of QW enclosures. Play around with all of them to get the capabilities of each, then plug in various drivers to see how they meet your needs. I always start with sealed followed by vented enclosure designs, as a guide. If you have used Horn Response, you will see that sufficient Xmax is necessary for low bass response at moderate to high SPL response, ... regards, Michael
What is the intended use of this TL?
If hi-fi use, a TL 15 will do, a simpler project would be an OB 31'':
Fostex FW800HS, 31.5" Super Woofer
A bit out of my price range!!
4K per unit 
As has been said above, a good 18" with 10mm x max will shift as much
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The PMC BB5 uses the RV3813 (15″) unit
Going to have a go modelling a TL with this one
Volt RV4564 18" The cabinet will likely be bigger than the BB5
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