[rockadanny]

My speakers (EgglestonWorks Fontaines - TMM - M's are Morel 6.5" polys) do not delve too deeply: -3dB @ 55Hz. I have a Titan sub, dialed to its lowest setting, resulting in a very satisfying full-enough for me-range sound (within +-3dB to 25Hz, where it is -4dB, and -7dB at 20Hz). Would adding the high-pass filters relieve my amp (Van Alstine Fet Valve Ultra 550) enough to warrant using? If so, which (65Hz or 85Hz)? And would their use degrade the sound quality from my mains in any way?

[Mike Dzurko]

My speakers (EgglestonWorks Fontaines - TMM - M's are Morel 6.5" polys) do not delve too deeply: -3dB @ 55Hz. I have a Titan sub, dialed to its lowest setting, resulting in a very satisfying full-enough for me-range sound (within +-3dB to 25Hz, where it is -4dB, and -7dB at 20Hz). Would adding the high-pass filters relieve my amp (Van Alstine Fet Valve Ultra 550) enough to warrant using? If so, which (65Hz or 85Hz)? And would their use degrade the sound quality from my mains in any way?

I personally have always gotten better performance when using the high-pass filters . . .. there is a little insertion loss, so you of course have to adjust the volume level relative to the sub. The benefits of taking the bottom octaves load off the main amp and main speakers works for me. In your case, I'd go with the 85Hz filters.

[rockadanny]

Mike - Thanks for your help! I ordered the 85Hz filters as per your suggestion.

[rockadanny]

Mike - Insertion loss requires increasing the mains level? Does this mean that my amp will be working even harder than prior to the insertion of the filters?

[Mike Dzurko]

Mike - Insertion loss requires increasing the mains level? Does this mean that my amp will be working even harder than prior to the insertion of the filters?

The insertion loss will mean that you'll need to increase the GAIN on the amp via the volume control. However, this does not increase the demand for power, just means that the signal going into the amp is at a lower level so the gain has to increase. And, by rolling off starting at 85Hz, you are greatly reducing the amount of current that the amp has to deliver . . . . with some musical content it can be quite a lot.

[Mike Dzurko]

Forgot to mention, an added benefit will be significantly reduced distortion from the woofers in your mains. They won't be flapping around trying to reproduce nearly as much of the last two octaves and this will limit excursion

[rockadanny]

Mike - Awesome!! All that for only $30!!?? Why the hell did I wait so long to do this!? (Obviously, only I can answer that ... although my wife would gladly chime in.) Thank you Mike.

[rockadanny]

Anyone out there use the high-pass filters from ACI?
What is your experience with them?
I was told that filters such as these (not ACI's specifically) may mess up my highs and/or mids, constrict the soundstage width/depth, and likely impart their own signature into the sound, which would not be desireable.

[hoosier21]

Anyone out there use the high-pass filters from ACI?
What is your experience with them?
I was told that filters such as these (not ACI's specifically) may mess up my highs and/or mids, constrict the soundstage width/depth, and likely impart their own signature into the sound, which would not be desireable.

VERY interested in this onformatin also.

Thanks
Russ

[Mike Dzurko]

I wrote a long piece on this topic awhile back, wish I could find it ..  .

In summary, we did a number of very controlled tests with the result that yes, the passive filters change the sound in a couple of ways:

A) Less distortion above the crossover point, this varies from system to system. To me, this is an advantage, however, it may result in a slight perception of less warmth . . . probably at least in part for some of the same reasons many prefer vacuum tube electronics (hey, I love tubes myself!)
B) The frequency response of the system is changed, the subwoofer will likely need to be re-adjusted in terms of level, phase and crossover frequency. Until these are "re-dialed in" it may not sound as good.

When testing passive filters you must be very careful about matching levels. The insertion loss of course means that the balance will thrown off . . . and as mentioned above, you'll need to re-adjust other subwoofer parameters as well.

Frankly, it is difficult to easily test with and without the filters. In our case, we set up two identical sat-sub systems that shared the same source components. We optimized each system and then listened.

[Tom Tripp]

I put in high-pass filters when I added a Force to my Sapphires.  Huge improvement!  The soundstage,rather than becoming more restricted, opened up even more.  I noticed no changes in tone, other than obviously the low-end was missing, until I turned on the Force, that is.  Also, there was a little more detail. I heard no insertion loss, actually, nor loss of any kind.  I don't know if matters, but I use tubed amplification.   

[Fishboat]

Not to hyjack the thread, but I have a similar question & either I could start a new & very similar thread or add to the knowledge base here...so...

Mike,

I have a set of full range(36Hz-18kHz) Snell Type A's and I recently added a Titan LEII.  Sounds great so far(crossing over at around 40Hz), but I have run across your comments about the high pass filter being a step in the right direction.  You offer the HP filters at 65 & 85Hz.   The 65 seems a bit high for my speakers...would they be appropriate?   I have around 350 watts/channel going into the Type A's (86dB sensitivty) so I'm not hurting for power...is the HP option still advisable?  It might be worth locating the article you wrote & posting it in your web site's FAQ section as this topic probably comes up frequently (I would think).    

[Mike Dzurko]

Not to hyjack the thread, but I have a similar question & either I could start a new & very similar thread or add to the knowledge base here...so...

Mike,

I have a set of full range(36Hz-18kHz) Snell Type A's and I recently added a Titan LEII.  Sounds great so far(crossing over at around 40Hz), but I have run across your comments about the high pass filter being a step in the right direction.  You offer the HP filters at 65 & 85Hz.   The 65 seems a bit high for my speakers...would they be appropriate?   I have around 350 watts/channel going into the Type A's (86dB sensitivty) so I'm not hurting for power...is the HP option still advisable?  It might be worth locating the article you wrote & posting it in your web site's FAQ section as this topic probably comes up frequently (I would think).    

I haven't been able to find my copy of that article, might just have to do a re-write and post in the FAQs . . .  good idea! I do think it very possible that the 65Hz filters will help your present setup. Like all things audio, it varies by room, person, and system. However, the basic benefits of hi-passing are: improved dynamics (because the main amps and speakers aren't working as hard), and greater resolution (same reason).  Is there a downside? It is possible that adding the additional filter will result in a phase change that causes a discontinuity. However, that is again a function of distance, placement, and the characteristics of the main speakers. Probably 90% of the time this can be overcome with a re-balancing of the subwoofer controls. 

[rockadanny]

Dateline Atlanta ... "Slowest audiofile on the planet (me) finally installs ACI 65Hz in-line (RCA) filters - amazing results ensue" ...

I originally ordered the 85Hz filters, tried them out very briefly and felt I wanted to allow my mains to run slightly lower freqs so my sub would not have to run much, if at all, above 80Hz (the freq limit of non-direction). So I traded my 85s for another member's 65s, allowed them to collect just the right amount of dust and threw them in the other day.

Here is the data collected using my Radio Shack SPL meter (corrected) at my listening seat without and with the 65Hz in-line (RCA) filters playing ACI Sub Setup CD (warble frequencies) through my mains (Fontaines) with my subwoofer OFF, calibrated at 1kHz (and verified at 250Hz) to 80dB. (My room creates a suckout of -6dB at 55Hz and 60Hz when playing mains AND sub together regardless of the filters.)

         Mains only  Mains only
         No Filters    w/Filters
Hz         dB             dB
--      --------      ------
22.5      57              -
25         59              -
27.5      62              -
30         64              -
32.5      67              -
35         68              -
37.7      68              -
40         67             61
45         67             62
50         69             64
55         70             66
60         70             67
65         70             66
70         77             67
75         80             75
80         80             79
85         82             80
90         82             82

As you can see, the filters do their job in keeping the mains from attempting to produce very low freqs. The sound with the filters installed and sub ON (set to lowest crossover point) has greatly increased clarity. Better imaging and  soundstage, and I am also able to increase the volume greater than before with NO distortion.  An absolutely amazing improvement for $30!! A belated THANK YOU to MIKE D!

[Mike Dzurko]

You are very welcome and thanks for taking the time to write this up . . .  enjoy!   

Dateline Atlanta ... "Slowest audiofile on the planet (me) finally installs ACI 65Hz in-line (RCA) filters - amazing results ensue" ...

I originally ordered the 85Hz filters, tried them out very briefly and felt I wanted to allow my mains to run slightly lower freqs so my sub would not have to run much, if at all, above 80Hz (the freq limit of non-direction). So I traded my 85s for another member's 65s, allowed them to collect just the right amount of dust and threw them in the other day.

Here is the data collected using my Radio Shack SPL meter (corrected) at my listening seat without and with the 65Hz in-line (RCA) filters playing ACI Sub Setup CD (warble frequencies) through my mains (Fontaines) with my subwoofer OFF, calibrated at 1kHz (and verified at 250Hz) to 80dB. (My room creates a suckout of -6dB at 55Hz and 60Hz when playing mains AND sub together regardless of the filters.)

         Mains only  Mains only
         No Filters    w/Filters
Hz         dB             dB
--      --------      ------
22.5      57              -
25         59              -
27.5      62              -
30         64              -
32.5      67              -
35         68              -
37.7      68              -
40         67             61
45         67             62
50         69             64
55         70             66
60         70             67
65         70             66
70         77             67
75         80             75
80         80             79
85         82             80
90         82             82

As you can see, the filters do their job in keeping the mains from attempting to produce very low freqs. The sound with the filters installed and sub ON (set to lowest crossover point) has greatly increased clarity. Better imaging and  soundstage, and I am also able to increase the volume greater than before with NO distortion.  An absolutely amazing improvement for $30!! A belated THANK YOU to MIKE D!

[Jeff_Z]

Mike,
I am considering the high pass filters for my setup and not sure if I should go with the 65Hz or 85Hz. I also realize this question has been asked before and may have been answered. My speakers have a range of 35-20K -/+ 3db but in all honesty about 50 they really start to drop significantly. I think they really start to taper around 65Hz. They are electrostatics and obviously have different characteristics than conventional speakers.

They are Martin Logan CLSiiZ's and their specs are:
System Frequency Response
35–20,000 Hz ± 3 dB
Dispersion
Horizontal: 30 Degrees
Vertical: 48 inch (122 cm) Line Source
Sensitivity
86 dB/2.83 volts/meter
Impedance
Nominal: 4 ohms
Minimum: 1.5 ohms @ 20 kHz

My sub-woofer is also a Martin Logan, a Depth. It's specs are as follows:
20–150 Hz ± 3 dB. Anechoic through the LFE effects input.
Low Pass Filter Frequencies
30Hz, 35Hz, 45Hz, 55Hz, 65Hz, 80Hz
High Pass Filter Frequencies
40, 70Hz
Phase
0°, 90°, 180°, 270°

Sorry for the way this is posted. I currently have my sub at 55HZ and in general I believe it does a fine job but I am thinking that the high pass filter would clean up some of the "muddiness" I occasionally get in the low frequencies. I am assuming this is actually doubling the frequencies around the "cut-off" range. I am just not sure if the 65 Hz would be fine or should I use the 85Hz.

Thoughts? Comments? Advice?

Thanks

Jeff

[Mike Dzurko]

Jeff:

Generally we recommend the 85s for monitors, etc. and the 65s for full-range or nearly full-range speakers. Your MLs are sort of in between these two types.

I'd really suggest trying them both . . .  which works more optimum is also a function of the room and the response you're getting from both your sub and your mains, in your room. Without trying them both, you will always be wondering if it could be "even better".

[Jeff Zaret]

Mike,

Thanks for the reply. I kind of figured I might be in the middle on this.

Jeff

[DTB300]

Mike, any thoughts of making more filters for a wider range of choices - both lower and higher in frequency??

[NewBuyer]

...The sound with the filters installed and sub ON (set to lowest crossover point) has greatly increased clarity...

Well this might be another naive question on my part , but here goes:

The above member rockadanny, produced a table of db/freq measurements with the 65Hz filters in place, showing essentially nil response from the speakers at below 60Hz.  Also mentioned, is use of the lowest crossover point on the sub, which I believe is 35Hz.

Mike has also mentioned that the subs are already down -6db at the subwoofer's dialed crossover point, and from there on up, exhibits a further steep dropoff of -24db/octave.

So about the the above described setup: Would it not have a huge audible frequency dip, occurring between approximately 35Hz and 60Hz?