Subwoofer driver advice needed: 10" - 12" driver for 88L (3.1CuFt) enclosure

[ctmorsejr]

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 they’re 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 I’m 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 I’ve 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 I’d 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). I’m not against going with 12” drivers but I’d prefer to try 10” first so if I don’t 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 didn’t 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. I’m hoping that some of you might have experience with these or other drivers that might suit my needs. I’m 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. I’d like to keep the cost under $250 per driver if possible and I’m not totally against making new enclosures if there isn’t 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

 

[CharlieLaub]

Have you considered the Dayton UM12-22, sealed? These are sold through Parts-Express.

 

[sreten]

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.

 

[ctmorsejr]

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.

 

[CharlieLaub]

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.

 

[ctmorsejr]

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.

 

[ctmorsejr]

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

 

[sreten]

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.

 

[CharlieLaub]

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.

 

[ctmorsejr]

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.

 

[Baldin]

Add another sub

Hi ctmorsejr

I dont think there is anything wrong with your drivers. If you press them lightly in and out with the hand and not scratching sound are heard then almost certainly no problem.


I think you are just putting in way too much power into them and expect them to go much deeper than they are designed to do.
HT needs much more deep bass to de really satisfying ..... If you use all the power from your good Aragon 2x200W amp then you have quite surely exceded the Xmax of the drivers (which can of course also damage them).
See the first sim. As you have tuned to 25 Hz I don't think it will make any difference to add a subsonic filter ... not even for HT are there much sound under 25Hz and your port are taking the most load in this region. Problem is more around 40 Hz.

If you like your sub for music (though I would have chosen something going somewhat lower than the 36Hz f3 point here ... but if it works for you), then simply add a sub more, and also put it somewhere else in the room to get better room response ... experiment here for best result.
Use one chanel of the Aragon for the two Peerless wofers in parallel, and add another sub driven by the other. Here you need something a bit older school to get the max out .... e.g. UM10 is quite hungry for watt ... something like a Lab12 in 80l vented at 23Hz. You might need a potentiometer on the input for the peerless chanel to match the output.

By the way
IMHO a 10 inch is no slower than a 12 inch or 18 inch for that matter. There is alignment and room modes ... and this can cause boomy or slow lingering bass ....

 

[ctmorsejr]

Hi ctmorsejr

I dont think there is anything wrong with your drivers. If you press them lightly in and out with the hand and not scratching sound are heard then almost certainly no problem.


I think you are just putting in way too much power into them and expect them to go much deeper than they are designed to do.
HT needs much more deep bass to de really satisfying ..... If you use all the power from your good Aragon 2x200W amp then you have quite surely exceded the Xmax of the drivers (which can of course also damage them).
See the first sim. As you have tuned to 25 Hz I don't think it will make any difference to add a subsonic filter ... not even for HT are there much sound under 25Hz and your port are taking the most load in this region. Problem is more around 40 Hz.

If you like your sub for music (though I would have chosen something going somewhat lower than the 36Hz f3 point here ... but if it works for you), then simply add a sub more, and also put it somewhere else in the room to get better room response ... experiment here for best result.
Use one chanel of the Aragon for the two Peerless wofers in parallel, and add another sub driven by the other. Here you need something a bit older school to get the max out .... e.g. UM10 is quite hungry for watt ... something like a Lab12 in 80l vented at 23Hz. You might need a potentiometer on the input for the peerless chanel to match the output.

By the way
IMHO a 10 inch is no slower than a 12 inch or 18 inch for that matter. There is alignment and room modes ... and this can cause boomy or slow lingering bass ....

The drivers don't exhibit any discernible voice coil damage and in my experience exceeding the Xmax of a driver results in a very distinctive snapping sound when the voice coil bottoms out in the magnet. And I wasn’t implying that 10” subs are slower than larger ones but just the opposite that larger ones were slower than 10” drivers (at least back when we were designing systems).

I’m going to give up on using these enclosures (my brother has expressed an interest in them as they are) and start a new thread requesting opinions on 12” drivers that work well in various alignments. When we were active in trying available drivers it was evident that most drivers didn’t work well even in their best software modeled alignment. Since the price of sub drivers has risen so much I don’t want to throw away a lot of money experimenting with a bunch of different drivers only to find that they don’t work well in any low frequency alignment.

Thanks to everyone who provided input.