In-line high-pass filter

[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?"

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?"

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! 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