Subwoofer driver advice needed: 10" - 12" driver for 88L (3.1CuFt) enclosure - diyAudio
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Old 19th May 2016, 06:20 PM   #1
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Default Subwoofer driver advice needed: 10" - 12" driver for 88L (3.1CuFt) enclosure

I was lucky enough to learn speaker design from a gentleman named Frank Knight who was the owner of The Sound Room in Northern NY. We worked on many designs over a 15 year period from the late 80s to early 2000s including my current subs which are a pair of Peerless 831727 10 CC Line woofers in custom made 3.1 cubic foot (88L) enclosures. I decided on this particular 10 design after having no luck finding any 12 or larger subs (commercial or subs we built) that I liked with music. Even in sealed designs with their inherently better transient response I found 12 and larger drivers to sound slovenly and *****-like as Frank used to describe it.

I still love these subs with music but theyre not quite up to the task for HT now that my main system is sharing duties for both 2 channel listening as well as HT surround sound. At higher volume HT use whenever there is any significant levels of LFE the cones start to flex and the bass starts to sound like a warble instead of the fast and tight lower frequency attack that Im accustomed to with music. These drivers have a thinner cone than other drivers we tried which helps with the transients but not so much with the sometimes excessive low bass found in the LFE track in movies. So Ive been looking at replacing the 10 Peerless drivers with something more up to the HT side of things while maintaining the fast, tight bass I prefer for music.

Frank passed away a few years ago and Id like to continue to use the existing enclosures if possible (this was the last system we worked on together). The 3.11 cubic foot enclosures currently have a 3 x 7.75 port (tuning frequency of 25Hz or thereabouts iirc) but I am in no way against plugging the ports for a sealed design. I also know that there have been advances in woofer cone material and design which hopefully will allow for the type of bass I prefer (fast and tight being more important than an F3 under 30Hz). Im not against going with 12 drivers but Id prefer to try 10 first so if I dont like them the Peerless drivers can simply be put back in the enclosures. There is no crossover in the mix as I let my Arcam AV9 or Oppo BDP-95 take care of the bass management. The subs are powered by an Aragon 8008ST.

I have been out of the game for over a decade now but we used to get the majority of our drivers from Madisound so I checked there for available drivers. I didnt really find anything for 10 drivers that would seem to work in the existing enclosures but I did find a number of 12 drivers that Madisound listed for use in 3 4 CuFt enclosures. Im hoping that some of you might have experience with these or other drivers that might suit my needs. Im a little surprised at how much the price of 12 drivers has risen over the last 12 years or so. When I last ordered drivers the most expensive ones were usually from Dynaudio and those ran in the $100 range for 12 drivers. Id like to keep the cost under $250 per driver if possible and Im not totally against making new enclosures if there isnt anything suitable for use in the existing ones. I was a custom cabinet maker for 30 years before I switched to computer work as my main source of income so building new enclosures isn't a big deal.

The drivers I found that would seem to work are:

1) SB Acoustics SB34NRXL75-8 12" - 3.0 cu.ft ported
2) SB Acoustics SB34NRX75-6 12" - 2.6 4.04 cu.ft. sealed
3) Peerless 835017 XXLS 12" Aluminum Cone 4 ohm - 3.3 cu.ft. ported
4) SB Acoustics SB34SWNRX-S75 12" - 2.8 3.5 cu.ft. ported

Any advice would be greatly appreciated.

Thanks
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Old 19th May 2016, 06:28 PM   #2
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Have you considered the Dayton UM12-22, sealed? These are sold through Parts-Express.
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Old 19th May 2016, 06:41 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

Your problem is probably you haven't high passed the subs
below the port tuning frequency. Hardly ever a problem with
music, most definitely a problem with the HT LFE channel.

It that is the case new drivers won't help much, keeping vented.

2nd order Butterworth highpass @ 22 Hz will help a lot.

Can be built into the input circuit of the sub amplifier,
with just R's and C's, treating the inverting input as a
unity gain point for standard unity gain active filters.

rgds, sreten.
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Old 19th May 2016, 07:35 PM   #4
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Quote:
Originally Posted by CharlieLaub View Post
Have you considered the Dayton UM12-22, sealed? These are sold through Parts-Express.
Thank you for the suggestion.

I just checked this model on the Parts Express site and according to them ported it wants to be tuned to 20 Hz with a 10" wide by 1.5" high slot port that is 25" long. Unfortunately that won't work with the enclosures I have now and converting that to a 3" port will require it to be 13.12" long which also will be difficult in the current enclosure. And I've never seen a DVC woofer rated at 2 Ohms per coil. Even though I'm powering it with a beast of an amp 1 Ohm might present an issue so I'm assuming those could be wired in series instead of parallel.

I will check out the other drivers listed on the Parts Express website though. Thanks again for the suggestion.
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Old 19th May 2016, 08:04 PM   #5
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Quote:
Originally Posted by ctmorsejr View Post
Thank you for the suggestion.

I just checked this model on the Parts Express site and according to them ported it wants to be tuned to 20 Hz with a 10" wide by 1.5" high slot port that is 25" long. Unfortunately that won't work with the enclosures I have now and converting that to a 3" port will require it to be 13.12" long which also will be difficult in the current enclosure. And I've never seen a DVC woofer rated at 2 Ohms per coil. Even though I'm powering it with a beast of an amp 1 Ohm might present an issue so I'm assuming those could be wired in series instead of parallel.

I will check out the other drivers listed on the Parts Express website though. Thanks again for the suggestion.
Um, yeah, that's why I mentioned "sealed". Just close up the port.

You connect the two voice coils in series to yield a 4 Ohm nominal driver. I assumed you would use one per side, at 4 Ohms each.
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Old 19th May 2016, 08:11 PM   #6
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Quote:
Originally Posted by CharlieLaub View Post
Um, yeah, that's why I mentioned "sealed". Just close up the port.

You connect the two voice coils in series to yield a 4 Ohm nominal driver. I assumed you would use one per side, at 4 Ohms each.
Sorry I missed that. According to PE the sealed enclosure should be 2CuFt and if I remember bass section enclosure design correctly (which I may not be) placing a driver in too large of a sealed enclosure starts the low end roll off at a much higher frequency. But as I mentioned it has been over a decade so I may not be remembering anything correctly.
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Old 19th May 2016, 08:41 PM   #7
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Quote:
Originally Posted by sreten View Post
Hi,

Your problem is probably you haven't high passed the subs
below the port tuning frequency. Hardly ever a problem with
music, most definitely a problem with the HT LFE channel.

It that is the case new drivers won't help much, keeping vented.

2nd order Butterworth highpass @ 22 Hz will help a lot.

Can be built into the input circuit of the sub amplifier,
with just R's and C's, treating the inverting input as a
unity gain point for standard unity gain active filters.

rgds, sreten.
I considered that but it's only been an issue the last month or so and wasn't for the 2 years prior that I've used this system in it's current state. Maybe the spiders are losing some of their elasticity so now it's becoming an issue when before it was not.

I doubt I have much for crossover parts anymore and I'm unfamiliar with unity gain filters. I calculated a standard 2nd order high pass filter and I'd need a .23yF cap and a 225K mH coil for the 22KOhm input impedance of the 8008. I know I don't have any coils anywhere near that large.

I found 20Hz inline high pass filters on the PE website for $25/pair but they don't indicate what impedance they're designed for. But if these are a unity gain filter as you described maybe impedance is unimportant. Do you think these would be adequate to test if this is the issue?

Harrison Labs FMOD Inline Crossover Pair 20 Hz High Pass RCA

Thanks
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Old 19th May 2016, 10:59 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

There is not enough info on the FMOD's to be sure, but
IMO they should be enough to test if this is the issue.

However if the problem has suddenly appeared, then
suspect some sort of damage / failure somewhere.

rgds, sreten.

FWIW its possible to add an active high pass filter to
any power amplifier by modifying its input topology.

Last edited by sreten; 19th May 2016 at 11:01 PM.
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Old 19th May 2016, 11:15 PM   #9
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Quote:
Originally Posted by ctmorsejr View Post
Sorry I missed that. According to PE the sealed enclosure should be 2CuFt and if I remember bass section enclosure design correctly (which I may not be) placing a driver in too large of a sealed enclosure starts the low end roll off at a much higher frequency. But as I mentioned it has been over a decade so I may not be remembering anything correctly.
Lots has changes in the last 30 years... since a Dynaudio woofer was $100! Now you can get pretty accurate Thiele Small specs on a driver like this from the MFG, along with a plot of frequency response and so on in a nice pdf datasheet. There are ways to measure them exactly on your computer (with a small investment for an interface tool) if you need to know these numbers better than +/- 10 percent or so. You can then use one of several nice freeware box modeling programs. I host a couple of these (they are Excel spreadsheets) on my web site (see link in my signature) in the software page. Heck there are even online tools for this.

Instead of going by the generalizations that you recall from years ago you can simply model the frequency response and then see if that is satisfactory.

I suggest that you model the response you will get for a variety of drivers and then decide which one will work best for you given the box size, power amplifier capability, and so on.
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Old 20th May 2016, 01:02 PM   #10
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Quote:
Originally Posted by sreten View Post
Hi,

There is not enough info on the FMOD's to be sure, but
IMO they should be enough to test if this is the issue.

However if the problem has suddenly appeared, then
suspect some sort of damage / failure somewhere.

rgds, sreten.

FWIW its possible to add an active high pass filter to
any power amplifier by modifying its input topology.
Before I posted the question here I tried a different processor and amp and the problem persisted so I agree that it may very well be that something is damaged with the drivers. I'm actually having some work done on that amp soon so I'll inquire about modifying the input topology as you mentioned.

Thanks for the suggestion.
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