For sealed enclosures,
A) designing low Qtc (Qtc ~ 0.5 or lower) bass cabinet and using low sensitivity mid/tweeter, or adding attenuators to mid/high.
B) designing high Qtc (Qtc ~ 1 or greater) bass cabinet and using equal sensitivity mid/tweeter, or no attenuation on mid/tweeter.
Which one do you prefer? And why?
A) designing low Qtc (Qtc ~ 0.5 or lower) bass cabinet and using low sensitivity mid/tweeter, or adding attenuators to mid/high.
B) designing high Qtc (Qtc ~ 1 or greater) bass cabinet and using equal sensitivity mid/tweeter, or no attenuation on mid/tweeter.
Which one do you prefer? And why?
It's unlikely you will not need some matching of the other drivers.
More info.
https://www.diyaudio.com/community/threads/sealed-cabinet-design-qtc-and-layout-questions.56878
Also Dayton make a DSP for woofers called DSP-LF costing $90 and adjusted using a phone app (iWoofer) and highly rated on Amazon.
https://www.daytonaudio.com/product/1664/dsp-lf-low-frequency-dsp-controller
More info.
https://www.diyaudio.com/community/threads/sealed-cabinet-design-qtc-and-layout-questions.56878
Also Dayton make a DSP for woofers called DSP-LF costing $90 and adjusted using a phone app (iWoofer) and highly rated on Amazon.
https://www.daytonaudio.com/product/1664/dsp-lf-low-frequency-dsp-controller
if A & B options are for same exact drivers the system bandwidth would be reduced with increased sensitivity so that's the compromise, the classic. With given size system the low end runs out of steam first. Some thoughts that hopefully help you to make your own decision.
Which ever you choose might depend on your room. If you opt for extended bandwidth, and your listening spot has a modal peak which you must then EQ down, it was perhaps unnecessary and you could have gone with the other option instead. Lean bass is nicer to listen to than peaky bass response. Although, the better the low extension the better the system sounds, but requires not to have peaks that dominate.
Extended lows with same drivers likely means bigger box, or DSP.
Why you would need the sensitivity anyway? too small of a system that needs to work on it's limits? Why not make bigger one with extended bandwidth?
Attenuating the highs could be a good thing if you do it passively. In general it could cut amplifier hiss, if you have hissy amp or poor gain staging. Also it might reduce some distortion as per some "current drive".
It's mainly question what is your requirement for system bandwidth and how your room involves. Then, what is the SPL requirement for listening spot, calculate backwards how much your system needs to be capable of with the bandwidth you have in mind and perhaps considering amplification you have. These are two very basic requirements any project should start with. Then, you could use more sensitive drivers, but don't have to, leave it open to be sacrificed on some other compromise later in the design process. Have fun!
Which ever you choose might depend on your room. If you opt for extended bandwidth, and your listening spot has a modal peak which you must then EQ down, it was perhaps unnecessary and you could have gone with the other option instead. Lean bass is nicer to listen to than peaky bass response. Although, the better the low extension the better the system sounds, but requires not to have peaks that dominate.
Extended lows with same drivers likely means bigger box, or DSP.
Why you would need the sensitivity anyway? too small of a system that needs to work on it's limits? Why not make bigger one with extended bandwidth?
Attenuating the highs could be a good thing if you do it passively. In general it could cut amplifier hiss, if you have hissy amp or poor gain staging. Also it might reduce some distortion as per some "current drive".
It's mainly question what is your requirement for system bandwidth and how your room involves. Then, what is the SPL requirement for listening spot, calculate backwards how much your system needs to be capable of with the bandwidth you have in mind and perhaps considering amplification you have. These are two very basic requirements any project should start with. Then, you could use more sensitive drivers, but don't have to, leave it open to be sacrificed on some other compromise later in the design process. Have fun!
The objective of A & B options is that I found agreement with natural human's hearing or "Loudness compensation" theory. People tend to like bass content. A boost or an extension in bass region is preferable for most (not all) people. Yet, it should have decent quality, not only loud.
Luckily, the low Qtc (Qtc ~ 0.5 or lower) system could offer high bass quality, i.e., better transient, but suffer from the low efficiency. And, vice versa for the high Qtc (Qtc ~ 1 or greater).
Option A will yield decent but low SPL at bass, thus, mildly reducing mid/high would help "reveal" bass response. The disadvantage I could guess is the overall system sensitivity would be decreased, because attenuation will be applied to the mid/high which are the majority on the sonic spectrum. As a result, some amplifiers may find difficult to drive these speakers.
On the other hand, option B won't disturb the performance or the output of the mid/high. In order to emphasizing bass, it's straightforward to solve a problem at the root that is to design the peaky bass itself.
Yeah, first decide which problem you need to solve 🙂 So, first and foremost keep in mind what SPL level you need to reach with your system. If the lower sensitivity system can reach the level the system design is based on, then you don't have a problem and could extend the bass because system sensitivity is fine sacrifice, you can reduce it. You could deliberately design in extra SPL capability, which you can then sacrifice for more extension, but usually this plan includes a DSP as well.
About system Q, I'm not sure if box alignment is that audible, system Q is audible but in context how the system interacts with the room. I haven't done other comparisons side by side with two different Q boxes with same driver other than making my boxes smaller and smaller (150l ported > 55l sealed, same driver) during past few years and use EQ to adjust the system response in room and the sound has got better and better, as midrange noise of the box has gone down (for number of reasons), and finally I don't have to cut bass due to modes. I must add there is plan for additional subs to further help with room. And the system is big enough to allow this adjustment, I never worried about Q after the first boxes as system response is all over the place after bringing it to a room, nothing like in the simulator. It might be that in your application Q would be important so what I'm writing here is my personal experience trying to come up with nice and big enough living room system, that has enough capability for occasional party still being practical in size.
The thing is a small room dominates lows, and whether the box has a resonance or not (high Q) is nothing compared to room modes that resonate much much longer, although could emphasise them. It might be that the box Q is significant factor in bass sound as well, as many seem to reflect it is, it's just not straight forwards to think Q in isolation I think, it's the combination of speaker in room that makes response at listening spot and how resonances of the panels and inside box changes etc, which might also affect impression of sound. For example, if your system is small and you get to party, the driver heats up and Q goes up even if you designed it to be small. If your box is big and party, it might resonate nicely and have quite audible "box sound". So, if you want specific low Q system, better make it big enough that heat will never alter the Q significantly and sound doesn't change, also construct it well in order not to ruin mids. Also, prepare to handle effects of the room to be able to enjoy benefits of any particular Q.
My opinion and experience above is of course biased to what I've observed with my limited experience and since I haven't done proper A/B test it could be right or wrong, and thus value is only in encouragement you to test both systems in order to determine which one works for you better as whole. Until then, theoretical advice like this is as relevant as any 🙂
It is true that greater bass makes system great, and to me greater bass is analogous to big enough physical size of the system so that the capability exists, then positioning and EQ to make sure the room doesn't ruin it too bad, and in this context box Q becomes irrelevant as long as it's reasonable. If your system doesn't have these freedoms to adjust, then perhaps choose which one actually sounds better in the room, it might be the lower Q or higher Q, depending on how the system interacts with the room. Take one step to left and now the other box could sound better in bass. If either has problems in midrange, it'll lose with any positioning.
-------
Here is bit more about db levels, and you could come up with you own estimations.
Checkout: https://www.asha.org/public/hearing/loud-noise-dangers/
If it's casual listening, perhaps 80db + peaks is fine target at listening position, could be lean bass, so perhaps 95db @ 30Hz system maximum capability is just fine, perhaps even less could do.
If speakers are for party use, then 85-90db or so for elevated level and extended bass for nice feel. Movies the same. This could mean 105db @ 30Hz maximum capability peaks included. Or what ever target you land on. If it's small room this might be fine, big room you'd need to account for distance more.
Difference between 95db and 105db at 30Hz is is great, almost four times more volume displacement required.
About system Q, I'm not sure if box alignment is that audible, system Q is audible but in context how the system interacts with the room. I haven't done other comparisons side by side with two different Q boxes with same driver other than making my boxes smaller and smaller (150l ported > 55l sealed, same driver) during past few years and use EQ to adjust the system response in room and the sound has got better and better, as midrange noise of the box has gone down (for number of reasons), and finally I don't have to cut bass due to modes. I must add there is plan for additional subs to further help with room. And the system is big enough to allow this adjustment, I never worried about Q after the first boxes as system response is all over the place after bringing it to a room, nothing like in the simulator. It might be that in your application Q would be important so what I'm writing here is my personal experience trying to come up with nice and big enough living room system, that has enough capability for occasional party still being practical in size.
The thing is a small room dominates lows, and whether the box has a resonance or not (high Q) is nothing compared to room modes that resonate much much longer, although could emphasise them. It might be that the box Q is significant factor in bass sound as well, as many seem to reflect it is, it's just not straight forwards to think Q in isolation I think, it's the combination of speaker in room that makes response at listening spot and how resonances of the panels and inside box changes etc, which might also affect impression of sound. For example, if your system is small and you get to party, the driver heats up and Q goes up even if you designed it to be small. If your box is big and party, it might resonate nicely and have quite audible "box sound". So, if you want specific low Q system, better make it big enough that heat will never alter the Q significantly and sound doesn't change, also construct it well in order not to ruin mids. Also, prepare to handle effects of the room to be able to enjoy benefits of any particular Q.
My opinion and experience above is of course biased to what I've observed with my limited experience and since I haven't done proper A/B test it could be right or wrong, and thus value is only in encouragement you to test both systems in order to determine which one works for you better as whole. Until then, theoretical advice like this is as relevant as any 🙂
It is true that greater bass makes system great, and to me greater bass is analogous to big enough physical size of the system so that the capability exists, then positioning and EQ to make sure the room doesn't ruin it too bad, and in this context box Q becomes irrelevant as long as it's reasonable. If your system doesn't have these freedoms to adjust, then perhaps choose which one actually sounds better in the room, it might be the lower Q or higher Q, depending on how the system interacts with the room. Take one step to left and now the other box could sound better in bass. If either has problems in midrange, it'll lose with any positioning.
-------
Here is bit more about db levels, and you could come up with you own estimations.
Checkout: https://www.asha.org/public/hearing/loud-noise-dangers/
If it's casual listening, perhaps 80db + peaks is fine target at listening position, could be lean bass, so perhaps 95db @ 30Hz system maximum capability is just fine, perhaps even less could do.
If speakers are for party use, then 85-90db or so for elevated level and extended bass for nice feel. Movies the same. This could mean 105db @ 30Hz maximum capability peaks included. Or what ever target you land on. If it's small room this might be fine, big room you'd need to account for distance more.
Difference between 95db and 105db at 30Hz is is great, almost four times more volume displacement required.
Last edited:
From experience with my use of dsp for a good fullrange driver - controlled by measurements and listening tests I can say that system Q does not play any role.
Sonically it's true that the composition of two transfer functions: of dsp and loudspeaker to a desired target is a good solution for making a correct playing loudspeaker. Beside the factor of distortion.
What concerns efficiency a low Q can give you more efficiency in the bass.
Extreme are drivers with very low Q which connot reproduce bass without a horn or dsp use.
Example 18 inch PA speaker bass
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6767025
Sonically it's true that the composition of two transfer functions: of dsp and loudspeaker to a desired target is a good solution for making a correct playing loudspeaker. Beside the factor of distortion.
What concerns efficiency a low Q can give you more efficiency in the bass.
Extreme are drivers with very low Q which connot reproduce bass without a horn or dsp use.
Example 18 inch PA speaker bass
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6767025