Low end in older sp...
 

Low end in older speakers  

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Douglas Blake
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19/08/2019 12:24 pm  

I just had the chance to re-cap the crossovers in a pair of Klipsh Heresies...

These are old school all the way and they are surprisingly good sounding speakers. I changed the caps with low ESR Nonpolars, even though the old ones were still serviceable. I don't think it made a lot of difference in performance or sound, but they'll be good to go for another 30 years or so....

But this brings me to an old, unanswered question...

These speakers can handle 10hz and make it felt in a room. Nobody could hear it but you can feel the presence in the room. It's like the room is haunted. My Deforest speakers from the late 1970s could do the same thing, occasionally finding every thing that rattled in my house.

The new Fluance towers I set up for another client just recently, my current bookshelfs, and just about every other modern speaker dies a rather graceless death at about 40hz.

So... What changed?

 


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bjaurelio
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19/08/2019 3:24 pm  

Do you have a frequency response on those speakers? I would be surprised if they played well to 10Hz. If you are feeling a 10Hz signal through those, there's probably significant room gain in your house at that frequency. I have to admit to not having any knowledge about Fluance or Deforest speakers. What drivers and configuration are they using?


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Douglas Blake
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19/08/2019 4:05 pm  

@bjaurelio

I tested them right down to 5hz, which is the lower limit of my signal generator, yes they do produce 10hz at about -4db.

The Deforest speaker line was made by Philips and in the late 70s up to the mid 90s they were the go-to product for many manufacturers. They are discontinued now but there are a lot of Deforest speakers out there, rebranded by various companies. Yes, mine got down to well below 20hz and could shake the whole house on about 50 watts.

The information on Fluance is on Their Website

None of the new testing was done in my home ... these are clients where I do in-home service, for a fee of course.

But my question was not that specific. In general speakers don't do what they used to... the question is "Why... What changed?"

 


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bjaurelio
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19/08/2019 4:16 pm  

I wouldn't expect a speaker with 8" woofers to extend flat below 40 Hz. Since these are designed for home theater, they really don't need to extend below 80 Hz for a crossover to the subwoofer.

I have to admit that I'm really surprised by a 12" high efficiency driver playing down to 10 Hz at only -4db. My 15" Ultimax can only go down to about 14-16 Hz with significant DSP boost before excursion gets out of control. A -4db of 10 Hz on a 12" woofer is unheard of. I have no idea how your old speakers are going that low.


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Douglas Blake
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19/08/2019 4:36 pm  

@bjaurelio

In theory ... since the woofer is DC coupled to the amplifier, it should be able to follow a signal right down to 0 hertz.  Hook a battery across a woofer and the cone will move in or out and just sit there until you remove the battery... So the speaker itself is capable of very low frequency behaviour.  

I don't have the answer.  🤔 Which is why I asked...


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shrub0
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19/08/2019 5:49 pm  

My guess is that you are also getting alot of harmonic distortion like 2nd and 3rd (20 and 30hz). There are some decent spectrum analyzer apps for your phone out there.


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Douglas Blake
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19/08/2019 6:11 pm  

@shrub0

Actually, I have one of These

Yes, there is bound to be some distortion from the speaker at those frequencies. I didn't spend a lot of time on it, just took it down as far as I could to verify the reworked crossover...

 


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123Toid
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19/08/2019 6:13 pm  

@douglas-blake

I believe the Hersey's are sealed enclosures, correct?  One thing that many older speakers did, was use a large woofer, typically sealed.  Which in the right room can give you a decent amount of gain.  After all, you get a 6db per octave slope going down. T he Hersey's F3 is 58hz (depending on the year and model).  So to get 10hz, that well would have to be dsp and or a ridiculous amount of room gain.   Without room gain 10hz, should be about -30db down.  


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Douglas Blake
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19/08/2019 6:30 pm  

@123toid

That's what surprised me. Their own spec sheets say 30hz ... and even that isn't bad. getting a half decent reading down to 10hz was like a gift for my client.  

I honestly don't know how much room gain we were playing with. The FFT didn't show any significant nodes, but then that's not what I was looking for.  I was mostly concerned that the crossover frequencies where correct.

Yes, they are sealed, in as much as a removable back speaker can be sealed.  

The only thing I noticed was that they seemed a little big for a 12 inch woofer.  When I built mine way back when I also went a bit big (20%) knowing it would give better low end... but I never expected to shake the house.

In a similar vein my CA bookshelves go down to about 30hz without significant roll off, but that's because I tampered with the ports (I posted about that when I joined).

 This isn't the first time I've seen older speakers get down well into sub-woofer territory. We're talking about a full octave... The JBL L-100s are quite comfortable at 22hz... and they are ported. The Klipsh Horns get real low too. But most of the new stuff seems to cut off rather sharply in the 40hz range. 

That's why it's got me a bit mystified.

 


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TVOR-Ceasar
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20/08/2019 9:32 pm  

I can't say for sure, but I have a feeling that it's probably a couple of things.

First, I believe that older drivers were a bit more "loose" than today's drivers. You know, a little more compliant in the suspension. Today's drivers are engineered with accuracy in mind, moreso than digging really deep. Afaik, it's a tradeoff in that range, and the old designs went for bottom end.

Second, it's way too easy for today's designer to throw a sub into the mix rather than go the extra mile to wring the last few Hz out of a design. Not saying it's wrong, but just an observation over the last 40+ years.

Most newer designs are going for smaller drivers. While smaller drivers can produce low tones, they just don't have the surface area to do so with ease or without some sort of electronic compensation. The older designs were designed to passivley reach lower without any help. 

For example, I have my old Optimus 30's (10" 2-ways) and I had to replace the woofers with ones that have ceramic formers (burn-out proof). At the time, I had the Radio Shack STA-7 receiver driving them. This was the designated companion to the Minimus 7 Speakers. It's specs were 15 Hz - 20 kHz and 10 W/Ch. Volume set to 5 would shake the whole rec-room plus the rooms above. Not sure of the rest of the house since I was too busy enjoying the music to care that much. Unfortunately, I have no clue how low they go and that reciever is a door nail now.

-Charlie


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Douglas Blake
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20/08/2019 10:09 pm  
Posted by: @tvor-ceasar

I can't say for sure, but I have a feeling that it's probably a couple of things.

First, I believe that older drivers were a bit more "loose" than today's drivers. You know, a little more compliant in the suspension. Today's drivers are engineered with accuracy in mind, moreso than digging really deep. Afaik, it's a tradeoff in that range, and the old designs went for bottom end.

This is what I've been pondering ... some fundamental change in driver mechanics taking place.

Second, it's way too easy for today's designer to throw a sub into the mix rather than go the extra mile to wring the last few Hz out of a design. Not saying it's wrong, but just an observation over the last 40+ years.

I agree ... One has to wonder how much extra revenue that gets them. 

Most newer designs are going for smaller drivers. While smaller drivers can produce low tones, they just don't have the surface area to do so with ease or without some sort of electronic compensation. The older designs were designed to passivley reach lower without any help. 

That's just it. They simply don't move enough air to get the job done.

That and the shape of the cabinets has changed. In my day we made the box depth just enough to clear the back of the woofer magnet and the fronts were often almost as wide as they were tall, like the Heresies in the picture above. I have to wonder if the new "tower" shape has an impact on this as well.

For example, I have my old Optimus 30's (10" 2-ways) and I had to replace the woofers with ones that have ceramic formers (burn-out proof). At the time, I had the Radio Shack STA-7 receiver driving them. This was the designated companion to the Minimus 7 Speakers. It's specs were 15 Hz - 20 kHz and 10 W/Ch. Volume set to 5 would shake the whole rec-room plus the rooms above. Not sure of the rest of the house since I was too busy enjoying the music to care that much. Unfortunately, I have no clue how low they go and that reciever is a door nail now.

I had a pair of Optimus speakers back in the day, I believe mine were 8 inchers... they dug pretty deep as well. But it was the Deforest speakers that really rocked the house. 

Yes, the RS System-7 is a legend in stereo, the first miniature hi fi system, even had a phono preamp built in... Still got a pair of Minimus 7 speakers on my desktop, today, working off of a 20w/ch Muse Tripath amp. They were one of the best near field speakers of their day.

Wow ... memory lane...

It might be an interesting experiment to go old-school and prototype a set of speakers with the older proportions and design goals, just to see what would happen...


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TVOR-Ceasar
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21/08/2019 1:01 pm  
Posted by: @douglas-blake

That and the shape of the cabinets has changed. In my day we made the box depth just enough to clear the back of the woofer magnet and the fronts were often almost as wide as they were tall, like the Heresies in the picture above. I have to wonder if the new "tower" shape has an impact on this as well.

*************

I had a pair of Optimus speakers back in the day, I believe mine were 8 inchers... they dug pretty deep as well. But it was the Deforest speakers that really rocked the house. 

Yes, the RS System-7 is a legend in stereo, the first miniature hi fi system, even had a phono preamp built in... Still got a pair of Minimus 7 speakers on my desktop, today, working off of a 20w/ch Muse Tripath amp. They were one of the best near field speakers of their day.

Wow ... memory lane...

It might be an interesting experiment to go old-school and prototype a set of speakers with the older proportions and design goals, just to see what would happen...

Most modern cabinets seem to be based on the Acoustic Ratio rather than the Golden Ratio. Both are supposed to be comparable in performance, especially in dealing with standing waves internally. Although, there are many out there that have different shapes that seem to perform admirably, at least in their design bandwidth.

For those who are unfamiliar, the Golden Ratio (found quite a bit in nature and man-made objects - research it on Google) is based on the width being 1 unit, while the height is 1.6 units and the depth is 0.6 units. Any numbers around those are good enough to be included. The Acoustic Ratio is based on the Width being 1 unit while the height is 1.25 units and the depth is 0.8 units. Again, any numbers around those are good enough to be included.

Most of the older designs mentioned above are based on the Golden Ratio. Maybe there's something there. I know my old ADC 404's are based on Acoustic, and they are a pair I'll keep forever. They're that good.

I have those drivers I bought a while ago. When the weather cools a bit, I think I'll do some testing like you mentioned, see if there's a discernible difference.

 

Re: STA-7 (System 7) - I still have it and the original booklet and schematic. Might dig it out and do some further testing, but I think the Amp IC is gone. I forget which one it is. Here's a bit of info on it:

https://www.radiomuseum.org/r/radioshack_sta_7_catalog_no_31_1968.html

-Charlie


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Douglas Blake
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21/08/2019 1:20 pm  

@tvor-ceasar

Since I live in an apartment, I'm not able to set up a wood shop, so yes I would be very interested in the results of such an experiment.  In the good old days (sigh) I used to have a prefab cabinet where I could move the back in and out and adjust the top up and down... it was very interesting to play with the dimensions of that box and it did seem to have quite the effect on the sound.

If I may suggest ...

I've been looking at a lot of pictures and thinking about the setups I've worked on over the years. It seems to me there are two commonalities among the systems with the lowest bass response ... First; that they are relatively shallow depth wise and second that they don't use a lot of acoustic padding.  Some actually had none.  These Heresies I just worked on had about an inch and a half of glass wool. 

Of course they all have larger drivers... 8, 10, 12, 15 inches... but I also have to wonder if, as you posited there is a fundamental difference in the way older and newer drivers are being built.

Finally there's the matter of positioning.  The Audiophile solution of having the speakers nearly in the middle of the room is actually rather new. Back in the day we used to place speakers right against the wall and most often at the 1/4 and 3/4 positions along the wall.

As my history teacher used to constantly remind us... "Sometimes the old ways really are the best ways."

The thing I would really hate to discover is that this new thin, tall, speaker design with smaller drivers is nothing but a way to sell sub-woofers.

 


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Douglas Blake
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21/08/2019 1:52 pm  

Some older speakers ... note the proportions...

JBL L-100

Polk Audio s6

Advent 2w

Sony SS-7200

 


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