Subwoofer without hi pass filter

Hi all,
I’ve been looking to add a subwoofer to my two channel system. The one I am looking at is a Rythmik L12. It does not have a hi pass filter output (only low level input) . It will be used with Spendor 3/5’s that go down to 75 hz. Is a high pass filter necessary with a subwoofer? If so, why no high pass filter on this and some other subs I have looked at ?
Thanks much for some input on this !

It's not absolutely necessary, but without it your man speakers and amps will still have to reproduce the bass, where most of the energy is. This will limit their dynamic range in terms of both excursion and amplifier power.

Using a high pass filter the satellites get worked a lot less, their woofers stay in a linear operating area more often and you can turn them up louder without distortion.


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1- The L12 doesn’t contain a filter because it uses the economy Rythmik plate amp, not their full-feature model, which does.

2- However, picky listeners have found that many subs contain high-pass filters that aren’t the most transparent around, including Rythmik’s. Sub filters are not designed and built to audiophile standards, containing OpAmps and other nasty components.

3- There are two good ways to add a high-pass filter to your system:

     a- Install a capacitor of the correct value on the input jacks of your power amp. That creates a 1st order (6dB/octave) roll-off at the frequency determined by the capacitors value. That value, in combination with your amp’s input impedance, results in the corner frequency of the filter. The formula for determining the appropriate capacitor value to achieve your desired x/o frequency can be found all over the net via a Google search.

     b- Install an active electronic cross-over between your pre and power amps. A good one is the First Watt B-4, which Reno Hi-Fi sells for about a grand. It provides 1st/2nd/3rd/4th order filters (6/12/18/24dB an octave roll-off) in 20Hz increments up to about 1250Hz (I believe). Nelson Pass designed and builds it with all discrete components, no IC’s or OpAmps. The best deal around in an active x/o!

I would recommend caution. Very few people use a sub with your speakers. I'm not saying it can't be done, just that there's a high potential for mistakes. If I was in your position, I would contact John at Wellington Audio in FL.

He's an expert on British audio products. I can't think of anyone more competent to help you. If you live in CA, maybe try Gene Rubin if he's within driving distance. Other than that, I would call John. I haven't been to his store in a few years, but last time I was there we just happened to be talking about subs for small British speakers like you have. He's one of the most honest people in the industry, and will not try and sell you something that's not in your best interest.
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" Using a passive first order filter has two drawbacks: 1) you have to know the input impedance of your amp (maybe your amp meets the manufacturer's spec and maybe it doesn't) and 2) first order filters allow too much bass to reach the main speakers."

How do you come up with this stuff? As for 1), you have to consider the amp/speaker compatibility no matter what type of xover the speakers have. I've been in this business my entire life and never had a situation where someone had the slightest trouble picking an amp that will work with first order xover's. As for 2), I can easily prove you wrong. Not only that, I think you're just making the statement up altogether. (feel to counter that by providing the reputable source where you found it.). Vandersteen speakers use first order xovers. They have a reputation for making some of the best bass in all audio. They also have a reputation for merging seamlessly with subs for even better bass. If their way is wrong, why is the company so successful? The Model 2 is the best selling high end speaker of all time. Can you show me where you got that info, as well?

All that aside, what you're doing here isn't funny. There's a good chance someone will use the info presented in a thread like this to make a purchase. Obviously, you're upset with me and some of the others from yesterday's conversation. You were the one who lied and gave bad info. Now it looks like you're retaliating because you didn't like being proven wrong. If you have words for me, fine. But don't screw someone else up just because you're trying to get back at me.


Just to clarify things, if you didn't read any of the other posts I was referring to, its the exact same topic topic (First order xovers) where he was proven wrong. He's just making these comments to get back at me and some of the owners. The guy has absolutely no idea what he's talking about. I don't mean to make a problem in your thread, but you need know what his motives are. He's not here to help you.
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