In-line high-pass filter

[MikeBrewster77]

Greetings,

Does anyone have any experience using an in-line high-pass filter for their main speakers when coupled with a sub? I have a decent sub with solid response to 120hz, and am about to purchase a set of JBL L46's (this system is in a small room, so larger speakers would likely overpower the space.) If I recall correctly the L46's start to bottom out around 70hz, and I'd like to free them up a bit so they're not struggling with the lower frequencies. I'm thinking of a high-pass filter with a cross-over of 100hz. Given what I'm working with, an active cross-over & multiple amps is not really the route I want to go, and as a bit of a stereo purist (unlike the A/V receivers out there) my current amp doesn't offer the ability to control cross-over. The sub has a variable filter, so my thought was use a high-filter pass to cut the mains at 100hz, and set the sub accordingly.

Any suggestions? I guess I could alter the stock cross-over in the L46's, but again, that's a path I'd prefer not to go down.

I've seen a lot of "in-line" passes for car audio, but nothing for home systems. Any advice would be greatly appreciated! Also, are there any potential negative side-effects from this arrangement?

Thank you in advance.

P.S., If anyone is aware of a stereo integrated amp that does have subwoofer crossover control, I'd be interested in hearing about that as well.

Best,
- Mike

[Fred Sanford]

I'm using Harrison F-Mods in a similar way, as a passive line-level low-pass for a sub I'm using under some L110s. At only ~$30/pr from Crutchfield, it was easy to justify testing them out. For your purposes, I'd think they would work just fine.

I have my L46s high-passed at 100Hz as well, but with an Adcom A/V preamp and an HK processor. Works well, and gives me a little more confidence since the power amp I'm using with them is only 60WPC.

http://www.crutchfield.com/p_069900076/F-MODS-100-Hz-high-pass.html?search=fmod

je

[MikeBrewster77]

Thanks Fred - glad I'm not the only one out there with this "crazy" idea, and good to hear that it's working out well for you! I'll check them out.

Update - I did check them out, and while I can see where (with the RCA jack input/output confguration) they'd work well with a sub configuration as a low-pass solution, not sure how I'd use these as a high-pass in line with standard speaker wire. Any thoughts? Is anyone aware of anything on the market that would take actual amp's speaker output and achieve the same effect. Again, I'm trying to avoid bi-amping anything with this particular set up.

Fred, I looked at some H/K processors (specifically the 2.0) that have a cutoff of 100hz, but is that two way - i.e., does it cut at 100hz down to the sub and 100hz+ to the mains?

Thanks again for your help/ Mike


I'm using Harrison F-Mods in a similar way, as a passive line-level low-pass for a sub I'm using under some L110s. At only ~$30/pr from Crutchfield, it was easy to justify testing them out. For your purposes, I'd think they would work just fine.

I have my L46s high-passed at 100Hz as well, but with an Adcom A/V preamp and an HK processor. Works well, and gives me a little more confidence since the power amp I'm using with them is only 60WPC.

http://www.crutchfield.com/p_069900076/F-MODS-100-Hz-high-pass.html?search=fmod

je

[Fred Sanford]

Thanks Fred - glad I'm not the only one out there with this "crazy" idea, and good to hear that it's working out well for you! I'll check them out.

Update - I did check them out, and while I can see where (with the RCA jack input/output confguration) they'd work well with a sub configuration as a low-pass solution, not sure how I'd use these as a high-pass in line with standard speaker wire. Any thoughts? Is anyone aware of anything on the market that would take actual amp's speaker output and achieve the same effect. Again, I'm trying to avoid bi-amping anything with this particular set up.

Fred, I looked at some H/K processors (specifically the 2.0) that have a cutoff of 100hz, but is that two way - i.e., does it cut at 100hz down to the sub and 100hz+ to the mains?

Thanks again for your help/ Mike

I should have mentioned that I use them before a power amp, then feeding a passive sub. This particular product is line-level, I wasn't sure what your setup was or what your potential options could be (pre-out/power amp in, etc.). Yes, there are passive high-pass options for speaker level, but (as mentioned) line level has the added benefit of reducing the working load of your mains amplifier. Check out Crutchfield and Parts Express for what is out on the market...not that they're the only or the best places to buy, but they'll let you wander around and usually have decent descriptions. In fact, you can employ the Crutchfield customer service folks, they're not bad at all - an auto-based trick may be perfect for this application.

What's your current system? If it's a receiver or integrated amp, does it have a pre/power patch option?

Yes, generally if a processor has a sub out with low-pass filter, it will have (at least a menu option for) high-pass filter as well. You'll often see these in the manual as "speaker type small/large" and "bass management sub/main/both" or similar wording.

je

Edit: by the way, you have an active sub... so you are already bi-amping. Does your sub have ins AND outs? Do they have a high-pass in line? What's that model #?

[MikeBrewster77]

Hi Fred:

I truly appreciate your response. :)

I'm running a Yamaha RX-797 receiver with a line-level RCA sub output to a Mirage active subwoofer. I use the line level output to the sub rather than using it in a passive arrangement because I presumed a passive set-up would rob the receiver of power (it’s rated at 100 X 2 @ 8 Ohms.) I have the sub crossed at around 70hz right now, but am trying to get a clean cross over and also relieve my bookshelves from reproducing more low-end bass than they need to (sorry for ending my sentence with a preposition, but it seemed a bit too complicated to re-architect it to be grammatically correct...)

I never conceptualized it the way you described it, but you’re right in that I am bi-amping the system by using the receiver in conjunction with the sub’s amp. The receiver does have pre/power patch capabilities.

In short, what I’m trying to accomplish is a passive (speaker-level) cross over to the mains, and I can pretty much deal with the sub accordingly using the built in cross over or the RCA in-line low pass option you shared earlier. Essentially, what I’m trying to avoid in my current state – as unrefined as it may sound :o: – is having more than one amp in my rack to deal with this.

I’d definitely appreciate your advice.

Best,
- Mike

[Fred Sanford]

Hi Fred:

I truly appreciate your response. :)

I'm running a Yamaha RX-797 receiver with a line-level RCA sub output to a Mirage active subwoofer. I use the line level output to the sub rather than using it in a passive arrangement because I presumed a passive set-up would rob the receiver of power (it’s rated at 100 X 2 @ 8 Ohms.) I have the sub crossed at around 70hz right now, but am trying to get a clean cross over and also relieve my bookshelves from reproducing more low-end bass than they need to (sorry for ending my sentence with a preposition, but it seemed a bit too complicated to re-architect it to be grammatically correct...)

I never conceptualized it the way you described it, but you’re right in that I am bi-amping the system by using the receiver in conjunction with the sub’s amp. The receiver does have pre/power patch capabilities.

In short, what I’m trying to accomplish is a passive (speaker-level) cross over to the mains, and I can pretty much deal with the sub accordingly using the built in cross over or the RCA in-line low pass option you shared earlier. Essentially, what I’m trying to avoid in my current state – as unrefined as it may sound :o: – is having more than one amp in my rack to deal with this.

I’d definitely appreciate your advice.

Best,
- Mike

If I'm following correctly, you'll need to determine whether your Yamaha has pre-out/power-in patch capability, and you'd use two RCA y-jacks (double male, single female) to go out the pre-out, feed the sub amp from the female RCAs, and plug the y-jacks back in through the two high-pass FMODs so the Yamaha amp is relieved of reproducing the low freqs.

je

[grumpy]

This isn't as hard as all that... if F-mods are used, just put them in the "coupler"
main-in/pre-out loop.

Sub line-out is separate.

http://www.crutchfield.com/App/Product/Item/Photos/Default.aspx?i=022RX797&g=10420

(zoom in on rear panel)

[Fred Sanford]

This isn't as hard as all that... if F-mods are used, just put them in the "coupler"
main-in/pre-out loop.

Sub line-out is separate.

http://www.crutchfield.com/App/Product/Item/Photos/Default.aspx?i=022RX797&g=10420

(zoom in on rear panel)

I wasn't sure if the RX series had a dedicated sub out, I knew the RX-V's did. If it has a sub out, wouldn't it have bass management that could be set up to remove the bass freqs from the main amps, eliminating the need for FMODS?

je

[MikeBrewster77]

Fred and Grumpy thank you both for your advice.

After reading your suggestions, it made me realize just how much I had overcomplicated what is a really a very easy setup. :o:

Thanks again!
- Mike

[MikeBrewster77]

One would think, but there is no cross over control or other bass management options on the receiver. From what I've heard in talking to some folks in the audio world, for some reason pure stereo receivers simply don't have this feature, unlike A/V receivers which almost universally do these days.

Nonetheless, the sub does have a cross over control so I can simply use that to manage how it performs. My main concern was eliminating the redundancy of bass reproduction in the mains, so using the F-mods in loop seems like the easiest way to go.


I wasn't sure if the RX series had a dedicated sub out, I knew the RX-V's did. If it has a sub out, wouldn't it have bass management that could be set up to remove the bass freqs from the main amps, eliminating the need for FMODS?

je

[Fred Sanford]

One would think, but there is no cross over control or other bass management options on the receiver. From what I've heard in talking to some folks in the audio world, for some reason pure stereo receivers simply don't have this feature, unlike A/V receivers which almost universally do these days.

Nonetheless, the sub does have a cross over control so I can simply use that to manage how it performs. My main concern was eliminating the redundancy of bass reproduction in the mains, so using the F-mods in loop seems like the easiest way to go.

Sounds right, then...:thmbsup:

je

[MikeBrewster77]

Unless, of course, I can convince myself that I need one of these:

http://www.outlawaudio.com/products/rr2150.html

To my knowledge and based upon my research, the only stereo receiver that has integrated bass management controls. For the price point, it got some pretty good reviews too.

http://www.stereophile.com/integratedamps/306outlaw/

Hmmmmmm.............. ;)


Sounds right, then...:thmbsup:

je

[Fred Sanford]

Unless, of course, I can convince myself that I need one of these:

http://www.outlawaudio.com/products/rr2150.html

To my knowledge and based upon my research, the only stereo receiver that has integrated bass management controls. For the price point, it got some pretty good reviews too.

http://www.stereophile.com/integratedamps/306outlaw/

Hmmmmmm.............. ;)

Hmmm...$30 invisible toys that get installed and forgotten and you can't really hear them, or $700 new toy that's visible and purty and shiny and you get to touch and hear it all the time...hmmmmmm...that's a tough one, you should ask somebody else! :applaud:

Are you the guy that bought Yank's L46s? I also considered plugging the ports on them when using them with a high-pass filter & sub, but never heard any corroborating "go for it" kind of advice from others here. I figured it might tighten things up a bit, and maybe protect them somewhat (I use them in a theater environment) from peaks (such as dropping a needle on a record?).

je

[MikeBrewster77]

I know - tough call, right? Hmmm - something tangible, fun, and unique, or a couple of hidden filters... :blink: This would generally be a no brainer if it weren't for the @#$%&!+ economy scaring the bejeesus out of me these days.

I am the lucky guy who snagged Yank's L46s. That being said, I guess I'm not so scared of the economy that I've gone into hunker down in the bomb shelter, full out preservation financial mode yet; truth be told, I don't even have a bomb shelter - that would be weird, and I bet they have crappy acoustics.

I've read varying opinions on plugging the ports (not necessarily specific to the L46, but on other models) some of which are good, some indifferent, but none particularly negative. It's something I may try once I get everything balanced to see what the sound impact is. Not particularly worried about peaks (the cueing lever on your turntable is your friend ;)) but you make a good point, and accidents do unfortunately happen. :(

- Mike


Hmmm...$30 invisible toys that get installed and forgotten and you can't really hear them, or $700 new toy that's visible and purty and shiny and you get to touch and hear it all the time...hmmmmmm...that's a tough one, you should ask somebody else! :applaud:

Are you the guy that bought Yank's L46s? I also considered plugging the ports on them when using them with a high-pass filter & sub, but never heard any corroborating "go for it" kind of advice from others here. I figured it might tighten things up a bit, and maybe protect them somewhat (I use them in a theater environment) from peaks (such as dropping a needle on a record?).

je

[Fred Sanford]

I know - tough call, right? Hmmm - something tangible, fun, and unique, or a couple of hidden filters... :blink: This would generally be a no brainer if it weren't for the @#$%&!+ economy scaring the bejeesus out of me these days.

I am the lucky guy who snagged Yank's L46s. That being said, I guess I'm not so scared of the economy that I've gone into hunker down in the bomb shelter, full out preservation financial mode yet; truth be told, I don't even have a bomb shelter - that would be weird, and I bet they have crappy acoustics.

I've read varying opinions on plugging the ports (not necessarily specific to the L46, but on other models) some of which are good, some indifferent, but none particularly negative. It's something I may try once I get everything balanced to see what the sound impact is. Not particularly worried about peaks (the cueing lever on your turntable is your friend ;)) but you make a good point, and accidents do unfortunately happen. :(

- Mike

Right - we don't have to get off on that tangent here, but it is somewhat apropos. There's no known bass hump that we're trying to knock down in the L46 (as opposed to the L100 where plugging the port actually brings response closer to flat). I also don't assume that the foam-edged L46 woof is happier overall in a closed box - my initial question was whether plugging the port may help by limiting excursion in this situation, which is likely one not considered by the design engineers (high-pass filter in place, a sub picking up the slack). Also, modern movie soundtracks are probably potentially more dynamic and punishing than music of the L46's time period.

je

[MikeBrewster77]

All very valid and interesting considerations. I was of the thought that by putting a high pass filter in, you'd eliminate a lot of the subsonic stuff that would typically cause potentially damaging excursion. Even with the wider dynamics of today's source material, via the filtering you've eliminated the L46 from pulling duty at an end of the spectrum it would have been operating in originally (e.g., 50-100hz.) And while I don't use my system for home theater often - and thus could be way off base - I don't know that today's soundtracks are any more punishing than say a well pressed version of the 1812 Overture on vinyl, especially with a high pass filter in the mix. Incidentally (and based solely on my anecdotal observation) I tend to see less excursion from digital sources than I've seen from a purely analog signal.

All that being said, it could be interesting to do an observational test with the speakers side by side with one port plugged and the other open to see if there's any visible difference in excursion, and to take note of any sonic differences as well.

Best,
- Mike



Right - we don't have to get off on that tangent here, but it is somewhat apropos. There's no known bass hump that we're trying to knock down in the L46 (as opposed to the L100 where plugging the port actually brings response closer to flat). I also don't assume that the foam-edged L46 woof is happier overall in a closed box - my initial question was whether plugging the port may help by limiting excursion in this situation, which is likely one not considered by the design engineers (high-pass filter in place, a sub picking up the slack). Also, modern movie soundtracks are probably potentially more dynamic and punishing than music of the L46's time period.

je

[Fred Sanford]

All very valid and interesting considerations. I was of the thought that by putting a high pass filter in, you'd eliminate a lot of the subsonic stuff that would typically cause potentially damaging excursion. Even with the wider dynamics of today's source material, via the filtering you've eliminated the L46 from pulling duty at an end of the spectrum it would have been operating in originally (e.g., 50-100hz.) And while I don't use my system for home theater often - and thus could be way off base - I don't know that today's soundtracks are any more punishing than say a well pressed version of the 1812 Overture on vinyl, especially with a high pass filter in the mix. Incidentally (and based solely on my anecdotal observation) I tend to see less excursion from digital sources than I've seen from a purely analog signal.

All that being said, it could be interesting to do an observational test with the speakers side by side with one port plugged and the other open to see if there's any visible difference in excursion, and to take note of any sonic differences as well.

Best,
- Mike

There is a visible difference, I've tried it - I had accidently bought the L46-sized plugs when looking for the L100-sized plugs, that's what got me started thinking...and you're correct that the high-pass would be one good measure against over-excursion, I was wondering if this particular woofer model would benefit in any other way from the addition of a sealed box as well. I don't play vinyl through this particular system, but I'm pretty sure that mechanical feedback from that format would show more overall woofer movement than digital sources, but I was considering the transients in action movies for instance.

Most importantly, my questions arose less from "do my woofers need this?" and more from "what am I gonna do with these plugs I've accidently purchased?" :o:

je

[MikeBrewster77]

Hmmmm ... something just popped in my mind as an additional consideration.

The 034 tweeters in the L46s are prone to failure from all accounts I've read and from a personal experience. My parents owned a pair of L46s that they purchased new, and one of the tweeters blew after about 10 years of faithful service; that's actually how I came to inherit my first pair of these speakers. Unfortunately, back then I wasn't on the new fangled internets and had no idea that one could (at least at the time) buy replacement parts direct from JBL. I'll spare you the gory details of what I did to make the speakers "playable" but suffice it to say that it could be described as a youthful indiscretion at best.

Now, I'm not speaker engineer by any stretch, but I think some of the later 034 tweeters are encased in plastic. By plugging the port in the L46, I'm thinking you could potentially create sufficient internal pressure in the cabinet to crack the plastic and destroy the tweet. It's a hypothetical, and again I could be way off base, but I don't know that it's a chance I'd be willing to take without pulling the tweeter to see if it's plastic or metal.

In essence, I think that you're more likely to blow a tweeter in one of these than the woofer (at least in "normal" duty) and if plugging the port might increase that likelihood, I don't know that you'll gain anything over what you could potentially lose. :(

Best,
- Mike


There is a visible difference, I've tried it - I had accidently bought the L46-sized plugs when looking for the L100-sized plugs, that's what got me started thinking...and you're correct that the high-pass would be one good measure against over-excursion, I was wondering if this particular woofer model would benefit in any other way from the addition of a sealed box as well. I don't play vinyl through this particular system, but I'm pretty sure that mechanical feedback from that format would show more overall woofer movement than digital sources, but I was considering the transients in action movies for instance.

Most importantly, my questions arose less from "do my woofers need this?" and more from "what am I gonna do with these plugs I've accidently purchased?" :o:

je

[Fred Sanford]

Hmmmm ... something just popped in my mind as an additional consideration.

The 034 tweeters in the L46s are prone to failure from all accounts I've read and from a personal experience. My parents owned a pair of L46s that they purchased new, and one of the tweeters blew after about 10 years of faithful service; that's actually how I came to inherit my first pair of these speakers. Unfortunately, back then I wasn't on the new fangled internets and had no idea that one could (at least at the time) buy replacement parts direct from JBL. I'll spare you the gory details of what I did to make the speakers "playable" but suffice it to say that it could be described as a youthful indiscretion at best.

Now, I'm not speaker engineer by any stretch, but I think some of the later 034 tweeters are encased in plastic. By plugging the port in the L46, I'm thinking you could potentially create sufficient internal pressure in the cabinet to crack the plastic and destroy the tweet. It's a hypothetical, and again I could be way off base, but I don't know that it's a chance I'd be willing to take without pulling the tweeter to see if it's plastic or metal.

In essence, I think that you're more likely to blow a tweeter in one of these than the woofer (at least in "normal" duty) and if plugging the port might increase that likelihood, I don't know that you'll gain anything over what you could potentially lose. :(

Best,
- Mike

Valid points. I've yet to blow an 034 (I have 8 of them in circulation now), but have purchased 2 spares just in case. I did physically break one connector tab, luckily managing to repair it effectively but somewhat crudely. I did sub some spare 033s into my 4401s (metal plate & better high-freq extension, but rarer/more fragile/more expensive tweets) with little problem, and I know with a little woodwork and crossover tweaking you could get 035Ti series tweets into 4401s or L46s, which have sturdier back plates and would extend the highs quite a bit over 034s.

Which leads us further off-topic, into "L46s need more high-freq help than low-freq help"...

je

[MikeBrewster77]

I just want to go on record as saying it wasn't me who blew the tweeter! :p By the time that happened, I had a bedroom full of gear and was running ESS Laboratory 10B's, a JVC QLA-200 turntable, and an H/K 990 receiver, along with some nondescript CD player that mustn't have been very good since I don't remember anything about it. My system creamed my parent's at that point in time, so I never touched theirs. :)

Also, the tweeter was blown while mated to a very low power receiver. They previously had a Luxman (which died) and replaced it with a 45X2 Denon, which is far less than I would drive the L46s with since they're not a particularly efficient setup.

You're tweeter swaps sound pretty interesting, and I would definitely concur that I would be more likely to provide some “help” for the tweeters rather than the low end (which is easily augmented by a good sub.) That being said, I don’t think I'll ever be at the point of being able to alter this particular set of L46s (they're just too pure to mess with in their current state) but if I was to happen across another set that maybe needed some work, I could be tempted to do some Frankenstein-like experiments.

But no more speakers for now. I'm moving soon, and won't purchase anything until I'm in the new space. Well, never say never, but it's not likely... ;)

Best,
- Mike



Valid points. I've yet to blow an 034 (I have 8 of them in circulation now), but have purchased 2 spares just in case. I did physically break one connector tab, luckily managing to repair it effectively but somewhat crudely. I did sub some spare 033s into my 4401s (metal plate & better high-freq extension, but rarer/more fragile/more expensive tweets) with little problem, and I know with a little woodwork and crossover tweaking you could get 035Ti series tweets into 4401s or L46s, which have sturdier back plates and would extend the highs quite a bit over 034s.

Which leads us further off-topic, into "L46s need more high-freq help than low-freq help"...

je