High pass filtering the main speakers
Subscribe to Ask Paul Ask a QuestionRemoving the demands of reproducing bass frequencies from the amplifier seems like a really good thing to do. Yet, not many amp manufacturers seem to support it. Why?
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So when running a single or dual sub set up it’s best for your main amplifier to fully drive your main speaker’s while using the high level inputs on the subwoofers to drive the sub unless your sub doesn’t have high level inputs and outputs in which you would have to power the sub through its low pass filter connected to the preamp I assume. Not all subwoofers have high level inputs or high pass filters but I believe most if not all have low pass and/or high level inputs and outputs. I’m wondering if rather then using the subwoofers high level outputs if I’m better off using the second set of speaker connectors on my amplifier to drive the main speaker’s and subwoofer in parallel? Would that set up cause the ohms on my main amplifier to drop too low and cause problems? Noting that not all amplifiers have a second set of speaker connectors.
While agreeing with you Joe, there is another option to using the high-level inputs to a sub. On my Electrocompaniet ‘Nemo’ monoblocks there’s a so-called ‘link’ output which allows you to relay the full-spectrum preamp output onto either a sub’s line-level inputs or to another power amp. In my case, I use the ‘link’ outputs on the monoblocks to connect to my powered subs. Even so, the monoblocks are still amplifying the unfiltered bandwidth, even though the main speakers will be rolling off the lower frequencies.
So I guess Richard Vandersteen is wrong?
How is Vandersteen wrong? I thought his speaker’s are all passive. Has Vandersteen ever said he prefers to use high pass filters to his speaker’s when using a subwoofer?
The upper-end Vandersteen speakers (Quattro, Kento and Model 7) all use high pass filtering with powered subwoofers. From the Vandersteen website:
“High-pass filtering allows the main amplifier to perform better, unburdened of reproducing deep bass, and is also the only way to ensure flat frequency response at the crossover to the powered subwoofer. Passive speaker designs always require placement compromises between the areas in the room where the imaging is typically best (farther out in the room) and where the bass is best (closer to the walls for boundary reinforcement). In Vandersteen’s powered-bass speakers the speaker can be placed out in the room where it images best, while the 11-band EQ ensures powerful but perfectly tailored in-room bass performance. The best of all things”
I have heard what Paul is talking about. In my opinion Paul is right and it sounds better without using high pass filters. Running the amp and main speaker’s fully and run a low pass high or low level to the Sub sounds better because it avoids phase shift and other anomalies. You want to add the sub bass without interfering in any way with the main amplifier and speaker’s. Sure using a high pass will take some strain out of the main amp and main speaker’s and allow a higher output but at a cost to overall sound quality. You lose the main amp and main speaker’s signature.
Like Paul said biamping to get the quality of a tube amplifier at the top end and hefty bass of a transister amp at the low end is a different story. But if you’re happy with the sound of your main amplifier and speaker’s running at full frequency you will alter the sound character of both by using a high pass filter set up. Create other problems that didn’t exist before. The old saying if it ain’t broke don’t fix it comes into mind. Now Vandersteen being a speaker designer might have incorporated something into the design that eliminates or reduces problems because he designed the entire speaker which isn’t the case when mixing different speaker’s and amplifiers into the set up. You can ruin the amplifier or speaker character.
By the way in no way am I knocking Vandersteen speakers. I casually heard them in a hi fi shop one time and they sounded beautiful. Very musical speaker. They get great reviews too. I would love to add a pair of Vandys to my speaker collection someday.
To answer the question, no it won’t.
Most powered subs that have high level inputs and outputs, use resistors in series with the HLN’s and HLO’s to control how much of an impedance load goes on your amp.
Because if you have a pare of 8 ohm speakers, and you’re using a powered sub that has what I call speaker level ins and outs, your amp is only gonna see an 8ohm load per channel.
I bought a couple of 80Hz, 8 ohm, 12dB/oct high pass filters from ‘Parts Express’ to cut down on the low stuff going to my 2way, 5″ standmounters & they made some difference, but generally only on the ‘heavily bassed’ (Jennifer Warnes – ‘The Hunter’) mostly EDM tunes, but with the majority of my CD collection from the 60’s, 70’s & the 80’s there wasn’t that much of an issue with the bass reproduction overworking the 5″ mid/bass driver.
I DISAGREE. High pass filtering is better, not for amps but for the drivers being filtered, but ONLY when it’s done correctly and that means not using a generic filter. We know drivers are not flat and crossovers not only crossover but are used to correct driver frequency anomalies. A generic filter as on a generic sub woofer does not handle these anomalies and this is where the problem is. High pass filtering reduces the excursion of drivers above significantly and improves sound since they are not working as hard. My upper bass/ lower mids became way more open when high passed with a crossover designed just for my speakers.
I also disagree about your take on biamping. Again it’s not so much for the amp power supplies and the amp but for the load the amps see. Biamping should be active. This reduces the reactance the amp sees since the crossover parts are no longer part of the amp load; it only has to handle voice coil load. Reactance reduces effective amp power and reduces fidelity. The less reactance the better. Yes if I had the money I’d own fully active speakers with a seperate amp per crossover division.
In my experience when you roll off the bass on speakers that were designed using the bass, the real foundation of music, the speaker balance is thrown way off then you insert subwoofers that is a crap shoot. The best way I’ve heard any sub system was the main speaker’s full range, the sub attached my speaker wires from the amp and the crossover set at the sub, just below the lowest frequency of the in-room low point of the main speakers. You keep the main speakers sound and just add the lowest bottom end the amp keeps the sonic signature for the main as well as the subs, so integration is the best I’ve heard much better than running I.C’s from the preamp to the sub, REL subs are designed to be used this way and for a good reason.
There is an actual or implied crossover between sub-bass and the bass driver in the main speakers. We know how critical it is to get the design right in a crossover between bass, mid and treble drivers. Why would the crossover between sub-bass and bass be any simpler, particularly when we have to take the room into account at low frequencies? I guess that there is no correct single answer, just as there is no universal crossover design.
In professional sound, there is always a high-pass filter on the main speakers, because the aim is maximum power handling and minimum distortion at high SPL. If you run your home audio at rock concert levels you probably want to do the same. If your main speakers can easily handle the full-range signal, then it might make sense to tune the sub-bass to integrate without a high-pass filter.
I have a pair of Dynaudio BM6 MkIII on my desk as nearfield monitors. The BM6 has a fairly solid 7 inch woofer. I don’t have a sub in this system. It sounds decent enough at low volume levels, but sound quality suffers at medium to higher volume. I can see that the internal 100 W amplifier isn’t clipping. Today, I switched in the HPF at 80 Hz as a test. Obviously this kills the bass, but there’s a BIG improvement in distortion at higher volume. By higher volume I mean the level that we listen at when the house is otherwise unoccupied. I wouldn’t inflict that on other family members. Now I need a sub!