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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

Thanks, Mark! :bigsmile:

Yes, that's exactly what I did. I used a few bandpass filters to lower the effective -3 dB frequency of the HP filter to 15 Hz.
This works well. Depending on what you are after and what the system response is, the shelving approach gives a little wider range to work and allows you do create a softer corner if that is needed.

I did measure the tuning frequency of the system; it was exactly 16 Hz (distortion sweeps show it too). But as I explained earlies, it seems that the LMS-5400 could use a little bit more volume than the simulations suggest. Around 10-12 cu ft might be the sweet spot when using such a low tuning.
I caught your measurement of the tuning frequency. What I was referring to was the natural resonance fo the PRs. This is dependent on the suspension compliance of the PR and the moving mass, which sets the natural resonance of the PR's mass and spring itself. The tuning in box is separate from this and it is not affected by box volume. I don't recall what TC had posted for the range that Fp would be vs. mass added. You find this by measuring the system output well below resonance, obviously without a high pass. At some low frequency, ideally low single digits, sometimes in the teens, you will see a frequency where the PR and driver output cancel, forming a notch below the low corner of the subwoofer. Depending how close the notch is to the corner, this can affect the response around the low corner. This is also one of the reasons we want PRs to have very soft suspensions. I suspect you know this but read my question of asking about the tuning of the PRs in box. ;)
 

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Discussion Starter #22
Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

I caught your measurement of the tuning frequency. What I was referring to was the natural resonance fo the PRs. This is dependent on the suspension compliance of the PR and the moving mass, which sets the natural resonance of the PR's mass and spring itself. The tuning in box is separate from this and it is not affected by box volume. I don't recall what TC had posted for the range that Fp would be vs. mass added. You find this by measuring the system output well below resonance, obviously without a high pass. At some low frequency, ideally low single digits, sometimes in the teens, you will see a frequency where the PR and driver output cancel, forming a notch below the low corner of the subwoofer. Depending how close the notch is to the corner, this can affect the response around the low corner. This is also one of the reasons we want PRs to have very soft suspensions. I suspect you know this but read my question of asking about the tuning of the PRs in box. ;)
Sorry, Mark. I was in a bit of a hurry while responding to your question, and I didn't catch that you meant the Fsp instead of Fb. Unfortunately the measurements I took won't clearly show it so I can't give you a definitive answer. Also if the Qmp is lower than predicted (as I'm suspecting), the notch won't be very visible. I can take an impedance measurement for some further investigations.
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

Ilkka, how is your assessment of the in room response of the 5400 compared to any of your other test woofers. What I am getting at is, can you, with your eyes closed and not knowing which system is playing, tell that the 5400 pr system is being played, or, are some of the test systems up to snuff with it.

Thanks,
Robert.
 

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Elite Shackster
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Discussion Starter #24
Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

Ilkka, how is your assessment of the in room response of the 5400 compared to any of your other test woofers. What I am getting at is, can you, with your eyes closed and not knowing which system is playing, tell that the 5400 pr system is being played, or, are some of the test systems up to snuff with it.

Thanks,
Robert.
It mostly depends on the setup. If one doesn't carefully match the frequency responses of the subwoofers he's about to compare (in-room), the differences are quite audible as most subwoofers have quite different frequency responses (if not equalized). I would say it is the biggest reason why different subs sound different. Small differences in maximum output or extension aren't as audible in many situations. But depending on the material and SPL being used, and of course the actual absolute difference between the subs being compared, also these variables will contribute more and more.

But probably you are more interested in hearing whether the LMS-5400 PR system is the best thing since sliced bread. :R Well let's say that if I was about to fill a large room with quality bass (if money nor enclosure size wouldn't matter), this subwoofer (or multiples of it) would be my choice of the every subwoofer I have tested so far. But if I had a small room and wouldn't want to use any external EQ, there are better choices since the low end would get boosted too much due to room gain. Also when thinking about the subwoofers of this caliber, one should make sure that also the other speakers are up to the task. High performance subwoofer with traditional low performance speakers can lead out to an unbalanced system which doesn't sound much better than a lower performance, but a well balanced system.
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

Ilkka,

I have one of my boxes started and my actual measurements of the cubic feet is 9.26 cf per woofer. This includes all braces and the woofers and passives. That is very close to the ten feet you mentioned. What do you think?

Thanks,

Robert
 

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Elite Shackster
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Discussion Starter #28
Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

Ilkka,

I have one of my boxes started and my actual measurements of the cubic feet is 9.26 cf per woofer. This includes all braces and the woofers and passives. That is very close to the ten feet you mentioned. What do you think?

Thanks,

Robert
Sounds really good. You should get a slightly flatter frequency response (and more max output around tuning) than what I measured.
 

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Elite Shackster
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Discussion Starter #29
Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

Ilkka,

How much power did you throw at the 5400's to get the results?

Did you come close to clipping the amp?
I used a single bridged Crown CE4000. The manufacturer spec says 3600W when using 230V line voltage, which I used. Unfortunately I don't know how close to clipping I was, since I don't measure the amp output/waveform. But I can say that if you throw 2-3 kW to that subwoofer (and you have multiples of them!), make sure your room and house are properly constructed. :hsd: :blink:
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

Egg crate foam is used by many with excellent results.
For a point of reference, it should be noted that the average 2" egg crate foam sold as 'acoustic foam', has no appreciable absorption effect in under about 600-700Hz. A premium grade 2" foam, such as Auralex or EchoBuster, will not have an appreciable absorption effect under about 400Hz.

-Chris
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

For a point of reference, it should be noted that the average 2" egg crate foam sold as 'acoustic foam', has no appreciable absorption effect in under about 600-700Hz. A premium grade 2" foam, such as Auralex or EchoBuster, will not have an appreciable absorption effect under about 400Hz.

-Chris
My point of reference would be my first two Shiva unlined sonotubes. They has a "boomy" sound and an obvious resonating problem. I lined them with 1.5 inch thick open cell egg crate foam and the problem was solved. I've since built 5 more subs with egg crate foam installed for lining and have no problems with resonating or "boomy" sound. My personal experience is that egg crate foam works. :T
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

My point of reference would be my first two Shiva unlined sonotubes. They has a "boomy" sound and an obvious resonating problem. I lined them with 1.5 inch thick open cell egg crate foam and the problem was solved. I've since built 5 more subs with egg crate foam installed for lining and have no problems with resonating or "boomy" sound. My personal experience is that egg crate foam works. :T
That is against known physical action(foam of this type/thickness having any appreciable value at the bandwidth at subject here). I would propose that sub-conscious biasing may be one factor at play here.

-Chris
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

That is against known physical action(foam of this type/thickness having any appreciable value at the bandwidth at subject here). I would propose that sub-conscious biasing may be one factor at play here.

-Chris
I agree it's easy to fool the ears. That has been well documented over the years. But in this instance it would also mean I would not have noticed any difference by placing my hand on the cabinet when it was unlined and then lined. Would you have a link to ""no appreciable absorption effect""? I'd like to read up on this.
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

I agree it's easy to fool the ears. That has been well documented over the years. But in this instance it would also mean I would not have noticed any difference by placing my hand on the cabinet when it was unlined and then lined. Would you have a link to ""no appreciable absorption effect""? I'd like to read up on this.
"No appreciable absorption effect" is in reference to credible co-efficient testing of different materials - as can be found in many databases. You can research/look up this data, or you can refer to Ethan Winer's RealTraps web site, which has(or had) a database of lab test measurements of different materials, including two foam vendors(Auaralex and Foam By Mail). Rod Elliot's site(sound.westhost.com) also has some testing of various material as it relates to absorption in a small midbass application, which the general results match up with known general absorption properties established by other testing.

The only appreciable effect the foam can be expected to have in your subwoofer application, is that it can in some instances, reduce the port(or passive radiator) output due to physical air-coupling losses that can be induced in the system alignment. However, this seems unlikely based on the relatively thin foam you used based on the subwoofer cabinet size. For foam to be effective at say reducing the long dimension half-wave modal resonance at bass frequencies, or 1/4 wave null effect based on driver to nearest boundary point; you would have to use a high grade acoustic foam, such as Auralex, in 5-6" thickness. Alternatively, you can use 4" of 6-8lb/ft^3 mineral wool board for similar absorption properties. It must be clear, though, that this amount of material will certainly result in measurable loss in port efficiency/output.

-Chris
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

What about polyfill or poly batting?


Thanks,

Robert
These materials are even less effective than typical foams. At about 2" ployfill does not have an appreciable effect until frequencies above 1kHz. As shown in this article.

If you use OC705 or 8lb mineral board wrapped in a cloth fabric such that nothing is exposed you will have no issues with any fiber escaping into your room via the port while achieving effective dampening.
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

"The only appreciable effect the foam can be expected to have in your subwoofer application, ..."

An important reason to use stuffing is to increase the box effective volume.

The decrease in Fb of my 12 cu ft dual Avalanche 18 subs indicates >20% volume increase.

I used 3 layers of 2 lb/cu ft on all sides.

"...is that it can in some instances, reduce the port(or passive radiator) output due to physical air-coupling losses that can be induced in the system alignment."

Not sure where you came up with "physical air-coupling losses", but the issue, which is much more likely with ports, is restricting the movement of air because of its high velocity and the distance it moves.
 

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Re: DIY TC Sounds LMS-5400 18" + 2x18" PR 200L *new*

http://www.diysubwoofers.org/talkshop/messages/41415.htm

Here's a good read on the subject.

I would say that when the size of the enclosure goes above ~5 ft^3, stuffing the enclosure with "dampening" material becomes less and less effective and also less important. With small enclosure one can gain substantial volume by using a lot of dampening material, but with larger enclosures it becomes harder because one would have to use A LOT of fiberfill etc. Especially with ported subwoofer it usually starts to restrict the airflow before becoming enough effective.

With well built enclosures, I haven't found any difference in "SQ" whether the enclosure has been stuffed or not. Usually I use some but not much stuffing in the subwoofers I build.
 
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