I need some recommendation for bass drivers that function both as high quality dipole and closed enclosure. Planning two hybrid columns with a minimum of four drivers on each side. I would prefer smaller then 15" drivers, but would open to 15" if there are clear benefits.
The initial plan is to let them work from 80 Hz area, but would be nice to have the option to cross them over higher (up to about 150 Hz). I will a suitable amp to the task.
They will be accompanying these speakers:
Audio Artistry / CBT Products
Budget is flexible. What drivers can function really well for both applications?
The initial plan is to let them work from 80 Hz area, but would be nice to have the option to cross them over higher (up to about 150 Hz). I will a suitable amp to the task.
They will be accompanying these speakers:
Audio Artistry / CBT Products
Budget is flexible. What drivers can function really well for both applications?
If you want something as small as 10" then this would be my choice.
Creative Sound - Product Details
Creative Sound - Product Details
10" would be fine. I'm not familar with Creative Sound.
I've looked at Seas L26ROY:
http://www.seas.no/images/stories/design/pdf_datasheet/l26roy-d0001_.pdf
I've looked at Seas L26ROY:
http://www.seas.no/images/stories/design/pdf_datasheet/l26roy-d0001_.pdf
Do you have options for EQ'ing the subs? If not dipole and sealed require fairly different drivers. If you have EQ then your options are much more wide open... Probably something with a low Fs and a Qts ~.5? There are a lot of good drivers out there. The Dayton RSS315HF-4 12" certainly seems to get a lot of good comments.
The "optimum" specs for these two applications are somewhat divergent, but I can suggest the following as a compromise:
Subwoofer type driver with high Xmax and 4 ohm Re
Low Vas (the lower the better)
Medium Qts: 0.35 < Qts < 0.45
Fs around 25-35Hz
Electrical connection of 4 drivers as series-parallel to produce a 4 ohm load for the amp
This would allow you to build a "U frame" dipole that is rather tall but not too deep. You can then close up the back and operate it like a closed box subwoofer, although you will probably need some EQ like a Linkwitz Transform to tailor and extend slightly the low end of the passband. IF you don't want to build one, there is a company called Marchand Electronics in NYC that sells a fully adjustable LT circuit that they call the "Bassis".
The reason that I listed a specific range of Fs, is that when you operate the unit as a dipole, the response will slowly roll off (in the absence of EQ) at 6dB/octave until around Fs, where the response will transition to 18 dB/octave. It's actually helpful if Fs is no too low, because this is where the excursion required will stop increasing and start to level off. Since dipoles don't enjoy room gain below the room's characteristic frequency, there is no need to try for really low bass unless your listening space is gigantic, and most program material is above 30Hz anyway, at least for music. If you are looking for a home theater sub to reproduce cannon fire, then stick with closed box.
One 12" driver you might check out is made by creative sound (Canada, Creative Sound Solutions - Loudspeakers, Parts and DIY Speaker Kits). It's their Trio12 driver, with XBL motor system. This has a lower Fs that I listed above, but the cone area, Low Vas and large Xmax (20mm) make it very usable in the dual role. Here is a link to the spec sheet:
http://creativesound.ca/pdf/CSS-Trio12-data-051009.pdf
That's my 2 cents.
-Charlie
Subwoofer type driver with high Xmax and 4 ohm Re
Low Vas (the lower the better)
Medium Qts: 0.35 < Qts < 0.45
Fs around 25-35Hz
Electrical connection of 4 drivers as series-parallel to produce a 4 ohm load for the amp
This would allow you to build a "U frame" dipole that is rather tall but not too deep. You can then close up the back and operate it like a closed box subwoofer, although you will probably need some EQ like a Linkwitz Transform to tailor and extend slightly the low end of the passband. IF you don't want to build one, there is a company called Marchand Electronics in NYC that sells a fully adjustable LT circuit that they call the "Bassis".
The reason that I listed a specific range of Fs, is that when you operate the unit as a dipole, the response will slowly roll off (in the absence of EQ) at 6dB/octave until around Fs, where the response will transition to 18 dB/octave. It's actually helpful if Fs is no too low, because this is where the excursion required will stop increasing and start to level off. Since dipoles don't enjoy room gain below the room's characteristic frequency, there is no need to try for really low bass unless your listening space is gigantic, and most program material is above 30Hz anyway, at least for music. If you are looking for a home theater sub to reproduce cannon fire, then stick with closed box.
One 12" driver you might check out is made by creative sound (Canada, Creative Sound Solutions - Loudspeakers, Parts and DIY Speaker Kits). It's their Trio12 driver, with XBL motor system. This has a lower Fs that I listed above, but the cone area, Low Vas and large Xmax (20mm) make it very usable in the dual role. Here is a link to the spec sheet:
http://creativesound.ca/pdf/CSS-Trio12-data-051009.pdf
That's my 2 cents.
-Charlie
Yes, I have the option of using EQ. This will be an active speaker system. I will most likely either be using a DEQX or Hypex coming DLCP:
DLCP
I have actually looked at Dayton, the RSS390HO-4 15" Reference. But the 12" is a more suited size. But is the Fs too low?
Thanks for the input. I'm hearing different views on what the Fs should be for dipole. So I'm a little confused here whether it should be very low or not.
I understand that dipole will not give me great output to the depth with this size in mind, but that's really fine. I think good output down to about 30 Hz would be suffiecient with dipole. This is a dedicated hifi setup and I want quality bass. I have good experience with dipole bass from a pair of Gradient Revolution speakers I've had (12" Perleess drivers). At the same time I would like to have the option going sealed with a backplate. Both because I'm uncertain what I prefer, and also to make it versatile regarding placements and different room integration (when I move).
But can I combine these two systems without much compromise?
There are two things working against you when you use a low Q driver in a dipole: #1 the Q and Fc are not being raised like when you put the driver in a sealed box. You are getting more like the driver's response when you put it in an infinitely large box, and for a low Q driver this means quite a lot of rolloff in the bass, even the upper bass! #2 In addition the dipole loading gives rise to some roll off, at about 6 dB/oct.
So, you can use a low Q driver in an open baffle or U frame (SL recommends it in fact) but you will need quite a bit of EQ, and not the kind that your graphic equalizer can help with! If you are new to speaker building, leave that to the pros.
One other approach that has been successfully used by some designers is to use a high Q pro woofer in an open baffle. By high I mean Qts over 1.2. Higher Q's start to have a "bump" in the frequency response around resonance, and this can be used to partly offset the downsloping response of the open baffle. Martin King has published some nice work on this approach, see for instance:
http://www.quarter-wave.com/OBs/OB_Design.pdf
But this would be rather unsuitable as a closed box sub because of the high Qts.
One driver that I have in my "arsenal" that I am planning on trying in an open baffle, and that you might find useful for that purpose (but not for a closed box sub, unless it was HUGE) is the Peavey LowRider-18. This has a lowish Qts of around 0.35 I think, but Fs is around 30-35Hz and with a little EQ I can get the response in a large open baffle with "wide wings" to be pretty flat down to 35Hz.
-Charlie
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