I understand Hoffman's Iron Law stating that if I want low and loud, I need large. But lets say I have certain 12" driver that works well in a 2.5 cu. ft. cab with a port tuned to 34Hz. Lets say I use 3.5 cu ft. cab with same tuning. Of course, the port length will be shorter, but do I gain SPL?
Not necessarily. But if you use a driver that is optimum in 3.5 cf with a port tuning of 34, it will be a higher sensitivity driver.
Exactly.
@ johnr66: Once the driver is in an enclosure, it no longer means a lot of sense to speak of the driver alone, since it is now a "system", entangled with the enclosure volume/tuning. In physics this is known as a coupled double-mass/double spring damped oscillator. Although, one way you can enlarge the enclosure and gain total SPL is by using a tapped horn. Here you can scale the whole design up and gain wide bandwidth SPL.
Hi,
You'll gain SPL by having a higher Q bass alignment making the transient
response worse. For a 2.5cuft/34Hz alignment that does work well you
generally need a lower port tuning for the bigger cabinet to avoid boom.
Generally if the box is bigger than a good volume you either get a
bass peak, or to avoid a peak you get a tapered / drooping roll-off.
You don't gain a lot with the extra volume over a good volume.
In the example below optimum volume is less than 2.5cuft as
you are dealing with portable equipment, 2 cuft tuned to 33Hz
looks good for a low B 5 string bass, and a 4 cuft / 33Hz 2x12
is always going to better than the same 1x12 in 3.5 cuft.
rgds, sreten.
Attachment is Fs - 25Hz, Vas - 6cuft, Qts - 0.3.
Attachments
As well as what sreten has written, it also depends on if with the smaller box you are thermally limited but not mechanically limited. If you are thermally limited and therefore have spare mechanical capacity then the bigger box will enable you to use that capacity by not running into the thermal limit as soon.
The theroetical power performance ideal is an intersection of power and thermal limits, in practice this may not be the best sound however.
So it does means that i can make a simple conclusion that if i need tight bass i need to sacrifice low end SPL?? Still didnt get the idea here 😕
^ Generally yes! 🙂 The one way you *might* be able to avoid this is with Transmission lines, however I have never made nor listened to one so I only say that based on anecdotal stuff I've read.
Tony.
Tony.
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Hi
In general:
In a TL (Quarter Wave) you can control the roll off, resulting in a bass with no unwanted peaks. And even make the roll of a little "too" steep to compensate for room gain.
You can get the low SPL you want by the right combination of driver, geometry, volume and stuffing.
This modelling is done with MJK´s excellent models.
In general:
In a TL (Quarter Wave) you can control the roll off, resulting in a bass with no unwanted peaks. And even make the roll of a little "too" steep to compensate for room gain.
You can get the low SPL you want by the right combination of driver, geometry, volume and stuffing.
This modelling is done with MJK´s excellent models.
Correct, unless one can 'afford' a large cab and the generally more expensive driver
http://stereointegrity.com/docs/SIGroupDelay.pdf
http://stereointegrity.com/docs/WooferSpeed.pdf
http://stereointegrity.com/docs/Efficiency.pdf
GM
To me, having a mild peak in the 40-50 Hz range is not necessarily boomy. The bass is low and powerful feeling. I agree this is not hifi and there are transient issues. Boomy (to me) is having the peak in the 80-120 range and this is unlistenable. I had cheap car woofers like that. I had to stuff socks into the ports.
I've also ran into issues with good sealed designs sounding "slow". It was because of the room and standing waves. Moving the speakers helped.
I've also ran into issues with good sealed designs sounding "slow". It was because of the room and standing waves. Moving the speakers helped.
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a mild boost of how much bass boost around the mentioned frequency ... how many dB of gain is acceptable for it to sound like you've described ??
TQ ...
You really have to give it a listing test. I'd say 2 or 4 db. I've gone as high as 5 (modeled) and it sounded good. Too high and roll off is quick and transient response is a problem. Remember, this is not hifi, but bass lovers often like it. It is like free amplifier power for the bass.
I found in many builds that I didn't care for the flat response. Bass went low, but lacked any punch. I cut the port down which moves the tuning higher and adds peak. Bass sounded much better and punchier. It only works well with speakers that are tuned low for flat response, say with the F3 at 30 Hz. Tuning them to 35hz or more adds some punch. Some of the small commercial speakers do this, but at too high of frequency and they sound boomy to the point that I seal the port.
It is easy to experiment. Just build the box to what the modeling software recommends for flat response and try shorter ports until you find one that gives you a balance of good boost and overall sound.
Floyd Toole once remarked that he magically turned "flabby" bass into tight bass by equalising out the room resonance causing the flabbiness.
rcw
rcw
rcw666, this mostly applies in the subwoofer range. when we approach the schroeder frequency, room modes vanish and slowly turn into some sort of reverb, which should make midbass less punchy/focused if its energy is spread in time. lets say about 0.5x up to 2x the schroeder frequency should be about the midbass range. that would be around 100 to 400hz for most rooms. this is an area where equalizers are less ideal, but horns would be too big to add directionality. what do we do here to achieve tightness?
Without the stuffing, TLs and BRs are the same. That is, you can get any alignment of a TL in a BR, and vice versa. The difference is, because the "port" of a TL is so much bigger, you can add stuffing to it with more precision, and thus get quasi-aperiodic responses not practical with a small tube port.
(This is in line with what sreten said in one of his early posts.)
But yeh, I agree with recent posters that "tight bass" is more a matter of tuning the speaker to the room than any quality inherent in the speaker itself.
So if a horn is "tuned" to 35 Hz, external size 20x20x40 (just an example)
And a BR Is tuned to 35 Hz, same external size,
Same SINGLE driver, same voltage applied....the horn will have no more output?
Don't let Master Bateman get you going, he's still working it out for himself.
Totally. I hope people understand that 2/3rds of my projects are abject failures. I appreciate that people enjoy following them, but most of them wind up in the trash. I enjoy the process of learning more than I enjoy achieving perfection. That's the whole reason I bought the Gedlee Summas, I figured that I couldn't do any better on my own, so I might as well pay a pro to build the speakers for me.