When making calculations I figured with 2 drivers, as most bass at those low levels is mixed mono, and the wavelengths are long enough that in a standard near-field setup they are within phase and working together.
I wouldn't imagine box size would make a huge difference, as you can set your filter up to match a particular box's response. That said, the smaller you make the box, the more of a "peak" you're going to have just about the tuning frequency. Though the EQ can filter some of that out, the resonant nature of the peak will cause a certain amount of "ringing" which EQ can't deal with.
That can, of course, be dealt with by using dense stuffing, and the side effects of the stuffing CAN be corrected with EQ, but will require a bit more power to do so, so I imagine you'd have to start taking the driver's thermal power handling into account if you go too far with that...
These boxes have a system "Q" of about .8, and I imagine you could go a bit higher than that without too much problem.
Sound pretty good! I don't have a decibel meter, but I'm playing it about as loud as I would ever choose to listen to music while sitting at my computer. I'm assuming you're referring to the extremely low "kick." It subtle, but definitely there.
Another fun track is off the new Gorillaz album, "Welcome to the World of the Plastic Beach." It has a bassline that's almost entirely within the bottom octave.
and then there's The Planets, by Holst... but I won't get into that, as I'll have a chapter on listening impressions later
More eq needed = more power input.
The maximum SPL is always limited by displacement. (See the signature). With sealed boxes, the LF efficiency goes down with smaller boxes, but the max SPL output is always the same. You just have to shove more power in because the cone is being physically held back by the tiny amount of air (means harder to stretch and compress), so you've got your lower efficiency.
You'll end up hitting thermal ratings.
Chris
The maximum SPL is always limited by displacement. (See the signature). With sealed boxes, the LF efficiency goes down with smaller boxes, but the max SPL output is always the same. You just have to shove more power in because the cone is being physically held back by the tiny amount of air (means harder to stretch and compress), so you've got your lower efficiency.
You'll end up hitting thermal ratings.
Chris
Angel by Massive Attack, is one that my buddy always uses for speaker auditions.
looks like thermal rating won't be a problem.
for the same level at 30Hz the 3l box will need an extra 4db cut in the higher frequencies but I think that just means turning the amp up a bit more (double the power and a bit?)
that all depends on the driver and how much power it was taking to get that level at 30hz in the first place.
HOWEVER, Based on some crude measurements and calculations, if you're shooting for about 75-80db (AT OR WITHIN ONE METER), your power requirements are so low in the first place that any speaker that could physically pull it off is going to have well more thermal handling capability than you'd need.
Imagine a speaker similar to the CHR-70 with a 70hz resonance and an efficiency of 85db at 1watt/1meter. Playing that at 80db will require about half a watt. If you figure a 12db/octave falloff from a sealed enclosure, you need double the power for every half octave. In a 3liter box your cutoff is going to be about 100hz. The difference between 100hz and 30hz is less than two octaves, so you need conservatively 4 times the power to get flat to 30hz.
Thus, you need a whole whopping 2 WATTS OF POWER to get a CHR70 to play 30hz at 80db at 1meter.
According to specs, the CHR-70 can handle 22 watts continuous (worst case scenario, i.e. test tone) or 40 watts max (short burst like a kick drum). Yeeaahh... you've got a bit of room to work with.
In other words, stuff that thing silly and see what happens!
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in winISD I modelled 3l sealed and putting in 13W signal gives 4mm cone excursion and 73db. Is that right? or am I doing t wrong. And I need -23db EQ above 160Hz
with 9l it needs 5W, and cut of 18dB above 200Hz
I'm playing with electri-Q now. What filter combination do you use to get your EQ curve? My low-shelf is steep and has 'overshoots'.
with 9l it needs 5W, and cut of 18dB above 200Hz
I'm playing with electri-Q now. What filter combination do you use to get your EQ curve? My low-shelf is steep and has 'overshoots'.
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Most likely scenario is that I have no idea what I'm talking about.
As far as the EQ goes, I had to use two low shelf filters, each with a Q of about 1.5 added together. I just kinda messed around with it until I got the curve how I wanted. Then I used a couple "simple gain" filters to turn the whole thing down until the bass boost wsa at 0
I'd suggest using real materials for the LF evaluation. Not only for the power/excursion check, real materials consist of more complex content than the test tones, thus make the speakers busier, so you'll get a whole picture.
Take any bass-heavy materials you are familiar with, music or movies are all fine. (RTA helps.) If there's any problem, you won't have any problem to find it.
For example, Saint-Saens Symphony No.3, 2nd movement, should be the ultimate test of bass (or fullrange) - flat out full orchestra, bass drum hits, cymbals hammerings, pipe organ's padel... almost everything (except chorus). The speakers should be very very busy doing all those.
Or any action movies you like. Dinosaur's footsteps, various explisions, helicopters... anything.
If you watch the RTA in the meantime, you'll find out most 'explosive' bass notes are peaked around 40~60Hz range with wide band fast rising. LF under 30-some Hz does exit, not weak, but is seldom the strongest.
If the system is doing fine with these real materials at your desired SPL, then nothing to worry and just enjoy it.
Take any bass-heavy materials you are familiar with, music or movies are all fine. (RTA helps.) If there's any problem, you won't have any problem to find it.
For example, Saint-Saens Symphony No.3, 2nd movement, should be the ultimate test of bass (or fullrange) - flat out full orchestra, bass drum hits, cymbals hammerings, pipe organ's padel... almost everything (except chorus). The speakers should be very very busy doing all those.
Or any action movies you like. Dinosaur's footsteps, various explisions, helicopters... anything.
If you watch the RTA in the meantime, you'll find out most 'explosive' bass notes are peaked around 40~60Hz range with wide band fast rising. LF under 30-some Hz does exit, not weak, but is seldom the strongest.
If the system is doing fine with these real materials at your desired SPL, then nothing to worry and just enjoy it.
Hi,
Try these clips from Tom Danley: (bottom of the page)
Danley | Technical Downloads
As Danley said dynamic range in these clips is huge. I hope your project can handle it, don't break anything
Cheers,
--
Tuomas
Try these clips from Tom Danley: (bottom of the page)
Danley | Technical Downloads
As Danley said dynamic range in these clips is huge. I hope your project can handle it, don't break anything
Cheers,
--
Tuomas
I prefer to use both real material AND test tones. Aside from being a science geek and loving objective data, it's good to know what the speaker is ACTUALLY doing, rather than what you THINK it's doing.
Sure, the speakers might sound great with those particular recordings, but that doesn't mean they're making all the sounds that I should be hearing, or making them loud enough, or making them too loud. Perhaps they're completely loosing the whole 20-30hz range, but without a solid point of reference (having heard the song on a system that IS flat down to 20), I have no idea whether it sounds right or not.
"So go listen to the song on a solid reference system," you say? Well, think about it. How did that system BECOME a reference system? Objective measurements! Test tones!
You're nearly right. You need 2x the power for every 3dB more you want. A sealed box falls off at 12dB per octave, so you need 2x2x2x2 (4 lots of 3dB increase) of the power, which is 16 times. You'd end up needing 8 watts, and if you want it a little louder, they'd cook.
Chris
I fully agree. Just tried to say the (more or less) ignored half.
TBH, my main point is, please don't bother measuring a 4" doing 20Hz. If the speakers can please you by its bass performance subjectly, it's already a tremendously great job. Nothing wrong about that. After all, we build speakers for pleasing our hearing. At least that's one of the major reasons.
And, what's the point torturing such small driver with the last thing it should do? Excessive bass signal is just a big burden for it. A ballerina would never be happy performing with a barbell on her shoulder, and she would never perform well with such 'property'. She may survive unharmed, but what's the point?
I will be doing this very soon. What do you think of comparing them side by side with slightly different signal chains:
flac file > foobar+EQ > chipamp Left > sealed
flac file > squeezebox > chipamp Right > BR
The alternative is to use just foobar and switch the EQ at the same time as switching the speaker over.
do you mean comparing the left channel against the right channel due to having only 2/ch amp? i think it should work, for the LF stuff is often equally spread over the two channels in the mix
also you can try the 'downmix channels to mono' in foobar->preferences->dsp configuration. to me it muffles up the sound and also LF driver duty i think would be a bit higher on the mono mix, but still it can be interesting comparison
also you can try the 'downmix channels to mono' in foobar->preferences->dsp configuration. to me it muffles up the sound and also LF driver duty i think would be a bit higher on the mono mix, but still it can be interesting comparison
I will only have 1 BR test speaker and 1 selaed test speaker.
What I meant was have one as the left speaker and one as the right speaker and have them both going at the same time (both can play the same channel). I think that will make it easier to spot any slight differences. The problem is the difference in the DtoA component.
I wonder if foobar can apply different EQ to each channel.
What I meant was have one as the left speaker and one as the right speaker and have them both going at the same time (both can play the same channel). I think that will make it easier to spot any slight differences. The problem is the difference in the DtoA component.
I wonder if foobar can apply different EQ to each channel.
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