anatech said:
Not really, because the cone excursion does not increase below Fs in a closed box, its flat. There would be some excursion increase from signal below Fs adding to existing signals, but this is nothing like the problem with ported where the cone becomes unloaded below Fs and the excursion goes way up.
And, as I have said, I use large drivers in smallish boxes and cone excursion related distortion is insignificant.
A sealed midrange is different because its not usually very big and there is a lot of bandwidth below its Fs. Remember my designs use large drivers and have Fs's of about 50 - 70 Hz depending on size so its not like this is a midrange.
Yes, thats exactly correct, implying that we can LOWER Q with a passive network as well as raise it - right? Yes, this does lower the efficiency, but I always have to do that with the compression driver anyways. It might not be a good thing to do for the woofer!
Your welcome.
The enclosure AND the driver are a HP filter. The enclosure alone is just a compliance (unported of course).
Hi Earl,
While I like the addition of more LF sources in more locations with the main speakers set to "large" or equivalent, to do what you describe, you need a receiver/processor which will "copy" the bass of the main speakers to the subs, as well as routing the LFE to the main speakers, although the LFE routing back to the main speakers is probably less of a concern, although it does mean you have different cases of bass reproduction for low frequency content recorded in the L, C or R vs that which is recorded to the LFE channel.
Please note my point is less about the concept and more about the hurdles in implementation.
On the matter of crossovers, I would think it's a bit of an overly absolute statement to say all crossovers are bad. The problems are in driver size and spacing vs. crossover frequency and type as it relates to the desired directivity.
While I like the addition of more LF sources in more locations with the main speakers set to "large" or equivalent, to do what you describe, you need a receiver/processor which will "copy" the bass of the main speakers to the subs, as well as routing the LFE to the main speakers, although the LFE routing back to the main speakers is probably less of a concern, although it does mean you have different cases of bass reproduction for low frequency content recorded in the L, C or R vs that which is recorded to the LFE channel.
Please note my point is less about the concept and more about the hurdles in implementation.
On the matter of crossovers, I would think it's a bit of an overly absolute statement to say all crossovers are bad. The problems are in driver size and spacing vs. crossover frequency and type as it relates to the desired directivity.
Hi Mark,
The fact is that many receivers do exactly what you say. I know all Pioneer receivers do, although some other brands don't. If not, then yes, a little more signal routing is required.
As to crossovers, the performance is a continuum from bad to good where one can never reach the absolute case of an ideal transfer. In this regard I still say that the fewer the better. As the frequency goes up it gets harder and harder to get close to the ideal and with a requirement for narrow constant directivty at high frequencies, which requires a large mouth area, the problems just get bigger and bigger with frequency. Above 1 kHz, where the issue are most relavent psychoacoustically, I see absolutely no reason to have a crossover in a system where power handling is not a big issue. With high power handling requirements the need for large midrange drivers can often necessitate a high frequency crossover, but thats a pro consideration not ours here.
The fact is that many receivers do exactly what you say. I know all Pioneer receivers do, although some other brands don't. If not, then yes, a little more signal routing is required.
As to crossovers, the performance is a continuum from bad to good where one can never reach the absolute case of an ideal transfer. In this regard I still say that the fewer the better. As the frequency goes up it gets harder and harder to get close to the ideal and with a requirement for narrow constant directivty at high frequencies, which requires a large mouth area, the problems just get bigger and bigger with frequency. Above 1 kHz, where the issue are most relavent psychoacoustically, I see absolutely no reason to have a crossover in a system where power handling is not a big issue. With high power handling requirements the need for large midrange drivers can often necessitate a high frequency crossover, but thats a pro consideration not ours here.
Hi Earl,
I understand some of what you are doing in that case. I did intend to say that the system is a high pass filter.
I usually get a good laugh out of this situation. "Unclear on the concept" fits here.
In your response to Mark ...
-Chris
I understand some of what you are doing in that case. I did intend to say that the system is a high pass filter.
Is there a total system Q that you aim for? That is related to some peaking. Do you look for a Bessel type transfer in that case?
I only use ported enclosures with systems with a low f3. Sometimes I will use a resistive port, but still use an electronic crossover/amplifiers to drive the system.
Oh, you've seen the results of this practice.
I usually get a good laugh out of this situation. "Unclear on the concept" fits here.In your response to Mark ...
I agree somewhat. Each element you use for a passive crossover is a losser element. So energy is converted to heat with every additional component. In the case of a parallel RC to correct for tilt, I'll lump both those components together as one element to make the definitions easier. No point in arguing semantics when it's the idea that is important. Also, each component is an opportunity for the designer to make an error. However, the crossover can not be too simple! Some elements are required to correct for peaking or general response tilt.
-Chris
I like your wifes saying.
As to the "Q" of a LF system. Consider this. In a room with dozens of modes below say 150 Hz, usually of differeing "Q" and among these modes there is a mode called a "woofer" (its a mode just like all the other modes). Now how critical do you think the value of the "Q' would be for this singular mode in this forest? So long as its not above say 1.5, it really doesn't matter to me. In small rooms at LFs, the room dominates all else. Box size and type, ported or not, dipole, monopole, cardiod, high Q, low Q, it all pails compared with how you treat the room. And by "treat" I don't mean exclusively room "treatments", although the room damping is critical, I mean the entire LF design. How many subs, location, signals, those are the things that matter.
As to the "Q" of a LF system. Consider this. In a room with dozens of modes below say 150 Hz, usually of differeing "Q" and among these modes there is a mode called a "woofer" (its a mode just like all the other modes). Now how critical do you think the value of the "Q' would be for this singular mode in this forest? So long as its not above say 1.5, it really doesn't matter to me. In small rooms at LFs, the room dominates all else. Box size and type, ported or not, dipole, monopole, cardiod, high Q, low Q, it all pails compared with how you treat the room. And by "treat" I don't mean exclusively room "treatments", although the room damping is critical, I mean the entire LF design. How many subs, location, signals, those are the things that matter.
Dr. Geddes, I'm not sure you are correct that pioneer recievers copy the bass of the left, center, and right to the subwoofer when the main speakers are set to large. Most receivers do not do this, and I have used and even own a lower end Pioneer which I know does not do this. It only copies the bass when the speakers are set to small. In fact, my experience has been that very few processors or receivers do this, which is often of great distress to me (yeah it even makes me cry a little sometimes). Typically when this processing is done, the option is given a name, something like LFE+SW. I know my processor has this option, which means the subwoofer's will receive both the LFE channel as well as the low frequencies of the main speaker channels. It's one of the many things I think need to be fixed in recievers and processors. The other being the ability to vary the slope and frequency of the subwoofer channel and surround channels independently, and also having multiple bass channel outputs which can each be adjusted separately.
I mean, right now I can get close to what I want by mixing the built in crossover of my processor, which is 4th order L-R for the subwoofer which I set at 100hz, and then using the built in crossover of the subwoofer amp to further fine tune them. I found that by having the subwoofers to the left and behind me crossed lower helped smooth the response better in the room (They are set at like 80hz I think).
I mean, right now I can get close to what I want by mixing the built in crossover of my processor, which is 4th order L-R for the subwoofer which I set at 100hz, and then using the built in crossover of the subwoofer amp to further fine tune them. I found that by having the subwoofers to the left and behind me crossed lower helped smooth the response better in the room (They are set at like 80hz I think).
Well my receiver does do this when the subwoofer is set to "plus". It sends left and right bass to the subs in stereo and L + R bass plus LFE to the subs in 5.1 in "Large" mode. I also know that the newer high end Pioneer models do this because I checked the manual. And no don;t ask me the model numbers - just look them up.
Hi Earl,
My wife says "thank you".
My understanding is that an enclosed volume (listening room) will not properly support properly (it will roll off) any frequency that has a wavelength that is greater than 1/2 the diagonal from corner to opposite corner. Obviously there will be modifying factors to this guideline. What this means is that you need a large room to support a 30 Hz signal. By augmenting the normal system with a number of sub woofer systems, you are using brute force. Also a lot of energy.
I do my best to stay between 0.65 and 0.8 considering real life. My designs generally hung around 0.7 given a choice. Most were B4 ported, although there are a number of sealed and resistive port designs. Also a cool dual chamber that broad tunes the enclosure. I do understand that you use use loaded designs. Anything I've done like that were giant affairs with cutoffs around 40 ~ 50 Hz. I also used to do warranty on the Klipsch products, just when they came out with the Tractrix horn design. I must say that this design really improved the performance of their mid and high drivers. The K-Horns often came in with blown woofers, and sometimes a dead Carver PM 1.5 as well. One wonders how loud it was just before it packed it in.
-Chris
My wife says "thank you".
My understanding is that an enclosed volume (listening room) will not properly support properly (it will roll off) any frequency that has a wavelength that is greater than 1/2 the diagonal from corner to opposite corner. Obviously there will be modifying factors to this guideline. What this means is that you need a large room to support a 30 Hz signal. By augmenting the normal system with a number of sub woofer systems, you are using brute force. Also a lot of energy.
Where do you aim? This is if you have the freedom to create what you consider to be a system that fits the room with no other constraints. This is different to having to compromise for box size.
I do my best to stay between 0.65 and 0.8 considering real life. My designs generally hung around 0.7 given a choice. Most were B4 ported, although there are a number of sealed and resistive port designs. Also a cool dual chamber that broad tunes the enclosure. I do understand that you use use loaded designs. Anything I've done like that were giant affairs with cutoffs around 40 ~ 50 Hz. I also used to do warranty on the Klipsch products, just when they came out with the Tractrix horn design. I must say that this design really improved the performance of their mid and high drivers. The K-Horns often came in with blown woofers, and sometimes a dead Carver PM 1.5 as well. One wonders how loud it was just before it packed it in.
-Chris
Thanks for the response Dr. Geddes, I'm going to have to look into this. I bought the pioneer receiver I have for a bedroom system and didn't notice that ability. My father and brother both have higher end Pioneer's that also don't have that ability, but it could just be an age/price level thing? I mean, mine was a few years old and used when I got it, and it was something like 75 dollars, I'm assuming maybe 150 when new. My brother and Father probably spent 250 at most, so it might just be the level. I had looked in some manuals online once before, and didn't see this feature, so its good to know it exists and what to look for. I'm now wondering if more receivers have this and I've just missed the feature.
Dr. Gedlee interview in Voice Coil magazine
Voice Coil Interviews Dr. Earl Geddes
By Steve Mowry
Is a good interview with some valuable informations on various sound/speaker matters.
This was something for my mind:
-------
Given the design philosophy (highly directional controlled
directivity),
larger systems and drivers are required.
This approach tends to make the excursion linearity requirements
a negligible factor ......
Linearity only becomes an issue when one is pushing the
envelope of system size toward the extremely small. There are
customers who request this size constraint, but we try and
make them aware of
the trade-offs of small systems .....
-------
Here you can find a free PDF download of Voice Coil interview (from issue 10/2008)
http://www.audioxpress.com/magsdirx/voxcoil/addenda/index.htm
Regards Lineup
blue934 said:
Voice Coil Interviews Dr. Earl Geddes
By Steve Mowry
Is a good interview with some valuable informations on various sound/speaker matters.
This was something for my mind:
-------
Given the design philosophy (highly directional controlled
directivity),
larger systems and drivers are required.
This approach tends to make the excursion linearity requirements
a negligible factor ......
Linearity only becomes an issue when one is pushing the
envelope of system size toward the extremely small. There are
customers who request this size constraint, but we try and
make them aware of
the trade-offs of small systems .....
-------
Here you can find a free PDF download of Voice Coil interview (from issue 10/2008)
http://www.audioxpress.com/magsdirx/voxcoil/addenda/index.htm
Regards
LineupAlthough I need more hands-on experience with measurements to be able to say this:
I've always thought that crossovers below 100Hz were not too offensive, and thus I did always recommend HP-filtering my midbass to prevent them from dipping down too low.
I see that Gedde's case applies only to properly sized sealed boxes...that makes sense and I'll have to consider his advice now.
As for a X-over above 1Khz... this cannot be avoided unless you use a compression driver. I've been wanting to hear a Gedde's 15" OS-waveguide setup for this reason. I have a feeling it'd be PERFECT for large venues where dynamics are needed.
Some day... I'll be able to devote time/energy to my hobbies... some day
I've always thought that crossovers below 100Hz were not too offensive, and thus I did always recommend HP-filtering my midbass to prevent them from dipping down too low.
I see that Gedde's case applies only to properly sized sealed boxes...that makes sense and I'll have to consider his advice now.
As for a X-over above 1Khz... this cannot be avoided unless you use a compression driver. I've been wanting to hear a Gedde's 15" OS-waveguide setup for this reason. I have a feeling it'd be PERFECT for large venues where dynamics are needed.
Some day... I'll be able to devote time/energy to my hobbies... some day
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