Limiting a full range driver

My speakers, Reference 3A NEFES, have 2 full range 8" drivers. My question; is it better to limit the frequencies to 100 Hz and higher. My thinking is that the lower, sub 100 Hz signals interfere with the midrange too much with their larger cone movements. Or, is there no benefit to cutting out these frequencies?


Get a pair of rythmik FM8 8inch dual driver subs and limit your full range speaker to 250 hz. Your full range driver will stop crying and thank you from the bottom of its heart.

Hi OP,

Doppler distortion is a real thing, but usually the room interferes more.  It's worth understanding if your bass is smooth enough before going much further.

The quick answer is you can put a high pass filter in front of your amp, which is just a single capacitor at the right value for the amp impedance. 

I think 250 Hz is a little too high to cross a main speaker at.  Around 100 Hz is usually the upper bound, 60 Hz the lowest I'd normally recommend, but the idea that adding a subwoofer AND utilizing a high pass filter on your mains is sound, especially if you have room modes which you want to use an EQ to tame.  This way you put the EQ in line with the sub only.

Also, check out the AM Acoustics room mode simulator which will help you understand how bad your room modes are as well as give you ideas for the best placement.

I think 250 Hz is a little too high to cross a main speaker at. Around 100 Hz is usually the upper

You didn’t know?? The Rythmik FM8 is no ordinary sub. It is a special sub designed to wipe the tears/alleviate the struggles of his full range driver.

I am considering a miniDSP SHD Studio, all digital with no converting to analog, and then sending out to 2 DACs (OKTO DAC 8 to main speakers / Schiit Modius to my 2 15" passive subs). Amplifiers are Benchmark AHB2 for mains and a Crown Class D (750 WPC) to the subs. All on AES/EBU and balanced.

Well, the usual recommendation to avoid subwoofer localization and enhance the ability to put it elsewhere is to keep the low pass filter somewhere below 120 Hz.  I haven't heard any other methods.

OP:  Sounds like a good idea, but, this is key, be ready to measure your results.  Once a speaker/subwoofer gets into a room throw the specs out the window and pretend you know nothing about the performance of the speaker, because without measurements you really don't.  The room changes everything so while I think your approach to using digital miniDSPs is sound I also think you'll need to carefully gauge the setting and for that you'll need a mic and software.

It's an 8" driver and it can handle but low frequencies without distress.  If you really want to set a low limit you should aim for a 60Hz or less.  Do you really want your 15" subs handling the upper bass region?

I plan on getting the UMIK-2 (the better one) because the miniDSP also has Dirac that will need measurements. I know the 8" can handle the lows, but does that prohibit the midrange from sounding its best?

Unless you have larger and very good quality 20-20000 hz full range speakers, offloading the lowest octaves to a proper sub or 2 designed specifically for the task at hand is pretty much always a good move. You just have to choose the right sub(s) for the specific job at hand and do the integration right, which takes a little know-how. Definitely measure before and after in order to do the job right.


miniDSP and UMIK 2 mike is a very good choice. I use that mic with Room EQ Wizard to apply room correction in Roon DSP similarly both in one room with sub and several without. miniDSP is on my list as a potential future experiment in tweaking my sound both optimally and cost effectively.


I do observe that on paper those REF3a’s alone do look pretty full-range capable, depending on room size, with the right amp to enable that. Even then offloading bass to subs properly will allow the amp to not work as hard, theoretically lowering distortion, and that combined with the right powered sub or subs in the mix should yield clearly positive results, if done right.

I am considering a miniDSP SHD Studio, all digital with no converting to analog, and then sending out to 2 DACs (OKTO DAC 8 to main speakers / Schiit Modius to my 2 15" passive subs). Amplifiers are Benchmark AHB2 for mains and a Crown Class D (750 WPC) to the subs. All on AES/EBU and balanced.

Minidsp should do the trick. Their QC is a lil poor. Check if everything is working and get a replacement unit otherwise. If you have pre-existing 15 inch subs for intended use, you may be restricted to crossover no higher than 100ish hz. The specific rythmik sub I was talking about earlier can also serve as a mid bass unit and get down to 20 hz.

Depending on your room and freedom of placement, you could try your large subs at the 1/4, 1/4 and 1/4, 3/4 widthwise, lengthwise locations. With adjustable phase, you should be able to get rid of a lot of problematic room modes and hopefully still not localize anything. If you have 2 subs or more, a read of the Harman paper outlining the virtual sub placement principle could come in handy (as you play with placement).

I have been running full range for many years.  Don't limit the lower crossover at all.  You will get a much better blend and it will be more seamless running full range.  That is the idea of a single driver???

The sub can compliment the system and you will only have to play with the upper cross on the sub and how hard the cut off is.

Finally, if you are finding that your single driver is distorting because you like lots of bass or lots of volume then that is another story.  Most single drivers will fill a room but not rock it.

Dear @koestner  : Yes, doi t and your home system reorduction will shines as even before because what you will doing is to lower the IMD of those 8" drivers. You will have with out any doubt a higher quality performance levels and yes the  high-pass filter must be at 100hz.


Regards and enjoy the MUSIC NOT DISTORTIONS,


Funny..I`ve been running my Revel F52`s full range with subs from the start.

I`ve just recently put the Revels closer to the front wall and put the switch in back to the 'Contour' setting and I`m liking what I hear.

The three 'bass' drivers are only 6.5" so this position is sounding cleaner to me.

I would just keep the low pass setting of the sub at it's lowest setting (many are 40 or 50hz) to keep it well out of the lower male vocal range, which typically starts around 80hz, but some basement dwellers can get near 60hz.    I would only attempt to limit the LF of the main speakers if this doesn't give a satisfactory blend. 



This is one of those it-may-or-may-not things. Even if you crossover the drivers at 100hz, they are still 8-inch drivers. The midrange performance should not change since the relationship between the radiating area and wavelength (frequency) is still the same. The bass performance is probably not at the expense of midrange and instead attributed to the driver's excursion remaining linear throughout the frequency range at realistic volume levels.



Wow, some very interesting posts here. Some are the opposite of others, but I want to thank everyone for their thoughtful and honest opinions. As is usually the case, I will have to try it to find out. Well, at least I have a lot of tinkering to look forward to.

It seems to me that you're running the Ref 3As full range without a sub.  Before you go adding filters and subs, have you experimented with moving the speakers around in the room to see if you can smooth out the tonal balance that way?

Hi Koestner. You are right on the money. The level of distortion and volume limitation low bass causes in full range drivers is unacceptable. It is the single most significant thing you can do. Room control is important but it will do you no good if your system is volume limited and distorting. I have made this AB comparison for other people many times. I use full range ESLs. By themselves they are big polite loudspeakers, good at Jazz and classical. Crossing to subwoofers at 100 Hz is like putting a turbocharger in a 911. Hold on to your hat.

There are several obstacles, finding a decent subwoofer and a good active crossover. For subs I suggest the Martin Logan Balanced force series and the KEF KC 92 also a balanced force subwoofer. This is an extremely important design feature, it helps to limit distortion by keeping the enclosure from shaking. 

The best crossovers are digital. However, now you need four DAC channels instead of two. The inexpensive MiniDSP is a fine crossover, but the DACs are not so hot. The MiniDSP SHD Studio gives you a fine crossover and room control and you use your own DACs. Benchmark Media Systems uses this set up with their own DACs. That is a $6000 bill. Preamps such as the DEQX Pre 4, the Trinnov Amethyst and the Anthem STR have everything built in. The STR is under $4000.

I have no doubt that if you do this right you will be THRILLED with the results. Don't punt, take a full swing or you will just waste money. If you want to discuss this more please message me.

I still don’t  understand why a single driver to handle all of the frequencies would be a desirable thing given the potential problems that arise. Is the lack of a cross over the only reason? It seems like a well built 3 way would be the way to go. 

Happy listening all! 

Interesting speakers.

Dual 8’s are the equivilant of an (approximate) single 11" woofer. That’s a fair amount of "meat" and should produce a reasonable amount of bass at moderate levels without getting too "weird" in the midrange. Having dual motors and smaller cones (dual 8" vs 11") gives you advantages in control and resolution. I think this is a valid design that should yield very good sonic results. (Some reviewers agree). I’d make sure your vertical listening position height (ears) are dead on with the tweeter location. Otherwise, the "point source" benefit of the speaker will be compromised

To high pass, or not to high pass, may be a product of experimentation. There’s credible sub manufacturers out there that INSIST that you run the mains full range. I’ve experimented with this a bit, and can’t disagree with their recommendations. I think it’s speaker dependent, and volume dependent. And, yes, room dependent.

Before you start throwing money at fancy crossover schemes, you might want to just toss a quality sub (or, two, or three...) in the room and see/hear what happens. You may also find that the additional sound pressure created in the room by the powered sub(s) negates, to some degree, the need to put the pedal to the metal on the volume control, which will reduce some stress on the mains, thus cleaning up everything.

Nice speakers by the way. Well done.

Thank you for the recent posts, but deeper in this thread I did say that I am using subs. They are Velodyne DD15's that both broke (electronics problems) so I ran drivers to banana plugs that I installed on the plate amps. Now I use a stereo Crown Class D amp to power them. The amp is about 750 WPC into 4 Ohm in each channel. The amp has a built in low pass that I have set at 24 db/oct. and at 74 Hz.

"but deeper in this thread I did say that I am using subs."

Yep, there it is.  Got me.