My speakers with dual 10” woofers in closed boxes floor-standing style are measured bass response can reach down to “28Hz at -3dB” and “18Hz at -10dB”. Box resonance is 36Hz. Gross volume is 125 litres and net volume is 94 litres.
From this information, is it sufficient to find Qtc of the boxes? If so, how much it is? And if the target is to lift the 28Hz up from -3dB to 0dB, without any aids of electronic methods, what should be done to the cabinet volume, increase or decrease, and stuffing?
IIRC, in theory, enlarging box would extend bass response—to the lower frequency—but trading off with lower SPL there, while reducing box volume does the opposite—rising bass level up but cutting some deep bass out. Is it correct and still valid for this case?
From this information, is it sufficient to find Qtc of the boxes? If so, how much it is? And if the target is to lift the 28Hz up from -3dB to 0dB, without any aids of electronic methods, what should be done to the cabinet volume, increase or decrease, and stuffing?
IIRC, in theory, enlarging box would extend bass response—to the lower frequency—but trading off with lower SPL there, while reducing box volume does the opposite—rising bass level up but cutting some deep bass out. Is it correct and still valid for this case?
Sure you could increase the volume significantly to get a flatter response and more extension and more efficiency, at the compromise of size. Or, you could explore opening a window in the enclosure and converting it into a modular bass reflex. Port open to increase output to whatever you tune it to. Close it to return to sealed if you felt like it.
With electronics, like a DATS, you could measure its Q values basically in that volume, unstuffed, stuffed, etc, and work out the actual Qtc and what the Qtc can become via over-stuffing or increasing the enclosure volume, or both. Very specifically, but that requires electronics and measurements and a little calculation.
A DSP is the simplest way to get what you want. But if you don't want to add electronics, then you'll have to resort to exploring something other than sealed potentially if you want to increase output to an extended bass frequency, otherwise, sealed has the most extension on its own (full bandwidth), but if you want more output, flatter, to a lower frequency but give up everything under that frequency, then maybe bass reflex would allow this. Reflex tuning would also relieve your drivers of excursions limits down at these frequencies where you're tuning, allowing more power handling to be power limited instead of excursion limited, compression limited, etc.
Very best,
With electronics, like a DATS, you could measure its Q values basically in that volume, unstuffed, stuffed, etc, and work out the actual Qtc and what the Qtc can become via over-stuffing or increasing the enclosure volume, or both. Very specifically, but that requires electronics and measurements and a little calculation.
A DSP is the simplest way to get what you want. But if you don't want to add electronics, then you'll have to resort to exploring something other than sealed potentially if you want to increase output to an extended bass frequency, otherwise, sealed has the most extension on its own (full bandwidth), but if you want more output, flatter, to a lower frequency but give up everything under that frequency, then maybe bass reflex would allow this. Reflex tuning would also relieve your drivers of excursions limits down at these frequencies where you're tuning, allowing more power handling to be power limited instead of excursion limited, compression limited, etc.
Very best,
In theory - yes, if Fb, F3 and F10 are real measured data. Practically - no. It is easier to measure the actual Qtc.
Increase stuffing - the best method, failproof. Stuffing must not be compressed, but fluffy, in over 70% of internal volume. F3 will be slightly lower, but not much. The main benefit is tighter bass.
If not enough - install bass-reflex tube tuned to about 20 Hz (MalVeaux was faster). In this case stuffing must be on the walls only, less than 5 cm thick.
The last resort - increase volume, plus bass-reflex tube. But is it really necessary?
Bigger volume = slightly lower F3/F. SPL is the same, unless Qtc<0.7 (which is unlikely).
Smaller volume = higher F3, slightly (1 - 2 dB) bigger SPL in a hump just above Fb.
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Prescott, you can try a series capacitor as bass booster: https://www.diyaudio.com/community/...capacitor-with-closed-box-loudspeaker.415946/
If the data is correct, than Qtc=1.1. Not optimal for the best sound quality (nor the lowest F3), but ideal for series capacitor ("third order loading") - then F3 will be lower than 28 Hz.
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There's the Linkwitz transform that can alter the low frequency response.
With any given driver choice, how do you get more efficiency out of a sealed enclosure by increasing the size of the enclosure? Isn't the efficiency, as such, going to be essentially fixed by the choice of driver? Maybe a definition of efficiency is in order in this instance?
Assuming that the Qtc≤0.7071, how do you get a flatter response out of a sealed enclosure by increasing its size? Won't the low-frequency response droop more and more the greater the enclosure volume?
Determining the enclosure Qtc and its resonance frequency Fc from the impedance curve should be enough for you to estimate the low-frequency response of your sealed enclosure. Taken together, these two parameters are sufficient to be able to calculate the low-frequency response of the enclosure, and they will include the effective enclosure volume.
Consider the case of a sealed enclosure tuned such that its Qtc = 0.7071, producing the −3dB response at 28Hz. Reducing the enclosure volume will reduce the response at 28Hz and resulting in raising the resonance frequency of the enclosure. If Qtc gets to 1.0, then there will be a quite noticeable peak introduced into the response function above resonance (and well above 28Hz).
If the desire is to extend the low-frequency response, which will have the attendant effect of increasing the response at 28Hz, consider the possibility of adding a capacitor in series with the woofers. This may or may not work, depending on the actual driver impedance curve, as the appropriate interaction needs to occur to result in an extension of the low-frequency response.
When the box resonance frequency Fc is greater that F3, then this implies that Qtc > 0.7071. Hence, the sealed enclosure will have a peak in its response around 36Hz. If you increase the amount of stuffing, you will likely increase the effective volume of the enclosure a little. This will reduce the resonance frequency, and it may serve to also increase the output slightly at 28Hz.
Exactly. Taking most speakers and "simply" removing the passive filters for the woofers, and using any type of separate direct connected amplifier with line level EQ - is absolutely one of the biggest upgrade you could make to any speaker.
If there is a separate connection - dual posts - on the rear of the speaker, then you can avoid removing the passive filter. But having the full control is of course the best.
Correcting the bass, is not only making the bass much better, but it also lets you hear the midrange and tweeter much easier, since all rooms have peaks in the bass, which easily mask our ability to fully hear higher frequencies.
Today, a used amplifier for bass and some kind of EQ, is almost cheaper than rebuilding a speaker cabinet - crazy as it may seem.
You can be sure this speaker has the right volume for the bass drivers used. The theory mentioned doesn't take into account the limits of the drivers used. So increasing the volume will not give you any audible extended bass, but make the drivers less durable and they may hit their excursion limit and get damaged.
There is a mindset which makes people believe the manufacturer didn't give the customer all the fun the product can deliver. Which makes people chip-tune their cars for example. Some think this would be the same with old speakers. Which is quite wrong. Replace electrolytic capacitors and keeping your hands off from the rest will give you the best such decades old speakers can deliver. If you don't like what you hear, get another speaker. The old speaker doesn't care about your finances and will not sound better if you mess up its construction because it has compassion for you.. You get what you pay for and if you pay nothing you get nothing, sorry, but this is a cruel fact in a bad, bad world.
There is a mindset which makes people believe the manufacturer didn't give the customer all the fun the product can deliver. Which makes people chip-tune their cars for example. Some think this would be the same with old speakers. Which is quite wrong. Replace electrolytic capacitors and keeping your hands off from the rest will give you the best such decades old speakers can deliver. If you don't like what you hear, get another speaker. The old speaker doesn't care about your finances and will not sound better if you mess up its construction because it has compassion for you.. You get what you pay for and if you pay nothing you get nothing, sorry, but this is a cruel fact in a bad, bad world.
First of all measure in room response in mlp, when speaker will be in final position. Example (real) - 10" sub, closed, with f10 about 25 Hz is +5db at 24Hz, because there is room mode there. The same sub is eq +6dB at 35 Hz to be flat in mlp... You can use almost any speaker with reasonable bass response to test this
Not really, especially in todays world.
Once there was pride in manufacturing good quality.
These days it is only about producing the cheapest crap one can, for the most amount of profit (else ever increasing proftis which is the basic of the economic system would collapse).
That goes for almost every single industry around in general terms (there are some exceptions).
See all the expensive "luxury" brands getting exposed from China lately.
Rolex's rolling off the Chinese production lines just an example.
Norway has some "high end Hifi manufacturers" the electronics are wholly built and made in Taiwan or Chine, shipped to Norway, slapped a sticker on saying Oslo Norway (Hegel and Electrocompaniet fx).
Arendal sound, completely built and assembled in China every single piece, slapped a plate saying from Norway with love on the back, with some Norwegian landscapes to fool the general buyers into thinking they buy something else. With prices to match for profit margins.
A few hundred $ in components, for a 10,000 $ speaker, with labor at 1$ an hour.
Price justified by fancy marketing and the fancy looking exterior.
Not saying they are badly designed.
Just a dishonest business model aimed to fool potential customers.
A thorough analysis would reveal modding potential, all else is conjecture.
I'll never get why people make things harder for themselves. The simple and best answer is just some basic shelf filters in the low end. If you get some sort of DSP EQ, be it a hardware unit or just do it at the source, that opens up the possibility of further improvement to the speaker beyond bass control. It's basically free sound quality improvements.
Take a driver, any Fs, put it in a small volume. Now put it in a large volume. Or free air. The average response level will be technically flatter. You will get more output at 10~20hz as that lifts and the output above Fb decreases. The same thing can be noted by over stuffing an enclosure and measured. But we're not talking about going from 1.6 ft^3 to 2 ft^3, we're talking 1.6 ft^3 to 9 ft^3 or bigger, or free air. It's not practical for everyone in a loud speaker, but the concept is what it is.
Very best,
People has been doing it for decades over 30 years. e.g.. Waves’ Q10 “Paragraphic” equalizer (parametric equalizer with graphical interface “plug-in” (intermediary) for computers) since 1992.
Why are we so slow to adopt it?
@Arez
Back in the day, when I was fooled by glossy magazines and shiny heavy boxes, I had a Primare I30 amp. Gorgous amp. Great sound. Reassuringly heavy (16kg/30lbs for 100Wx2)
On the back it said-
Primare Systems AB
Designed in Sweden
But actually no indication of where it was made.
Why it was left out was probably a bit of an embarrassment. Most writers for Hi-Fi magazines probably didn’t even know where Taiwan was, or how it was different to China. Often some would comment about it being made in the “Far East”
My guess is that people who didn’t have access to an encyclopaedia in C20 perhaps thought that Taiwan is the same as China or Malaysia or Singapore or Hong Kong.
But that’s like saying Sweden is the same as Denmark which is the same as Norway which is the same as Finland- Ignorant at best but generally insensitive to the rich differences in culture and history.
How Taiwan went from making electronics for companies that decided to offshore (multinational companies) to being one of the biggest manufacturers of semiconductors in C21 is another fascinating story.
My guess it that Rolex is as relevant as a time piece today as the pocket-watch, except to people who like jewellery or heirlooms…. After all, Casio is now making mechanical watches….
Why are we so slow to adopt it?
@Arez
Back in the day, when I was fooled by glossy magazines and shiny heavy boxes, I had a Primare I30 amp. Gorgous amp. Great sound. Reassuringly heavy (16kg/30lbs for 100Wx2)
On the back it said-
Primare Systems AB
Designed in Sweden
But actually no indication of where it was made.
Why it was left out was probably a bit of an embarrassment. Most writers for Hi-Fi magazines probably didn’t even know where Taiwan was, or how it was different to China. Often some would comment about it being made in the “Far East”
My guess is that people who didn’t have access to an encyclopaedia in C20 perhaps thought that Taiwan is the same as China or Malaysia or Singapore or Hong Kong.
But that’s like saying Sweden is the same as Denmark which is the same as Norway which is the same as Finland- Ignorant at best but generally insensitive to the rich differences in culture and history.
How Taiwan went from making electronics for companies that decided to offshore (multinational companies) to being one of the biggest manufacturers of semiconductors in C21 is another fascinating story.
My guess it that Rolex is as relevant as a time piece today as the pocket-watch, except to people who like jewellery or heirlooms…. After all, Casio is now making mechanical watches….
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