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Subwoofer dropping off too early

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umbucker's picture
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I have recently purchased a velodyne SPL 1000 ULTRA and although I am happy with it overall I do have a slight issue....It seems to strugle to reach the very low frequencies I was expecting to hear with this sub, in fact It doesnt seem to get close to the Tannoy TS12 that it replaced when on paper it should distroy the tannoy.

 

With this in mind i decided to connect a frequency generator to the sub and have a little play, it seems the sub can handle everything fine down to about 30Hz. Quite disapointing really for a 1.5K sub! Especially when on paper it should go down to 23Hs. I just wondered what you suggest ??

Please note I had the subwoofer set to JAZZ for this so no filters were applied.

Also, I tried these tests before and after the ROOM EQ.

Thanks

Phil

 

Joined: 27 Jun 2008
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RE: Subwoofer dropping off too early

There's only so much a 10" driver can do, regardless of how powerful the amp is. 30Hz sounds about right to be honest, as a well designed single 12" will reach a little deeper. Also, you can defy the laws of physics - a small cabinet and relaitively small driver will not reach 20Hz with anything meaningful. The most bass I've ever heard from a small box was the Sunfire subs, but they seem to lack the ability to cover the range of frequencies that a sub should do, sounding more like a car sub. But they're loud.

You could play about with placement, and placing it near a wall will help, and in a corner will help a bit more. It could be that it does reach 20, just that it doesn't have the ability to reproduce that frequency with any real conviction.

For serious home cinema performance, I never really tend to recommend much less than 12" drivers.

[EDITED BY MODS - overstepping House Rules]

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umbucker's picture
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RE: Subwoofer dropping off too early

Thanks for the info - i will try placment and see what I can do. With the spec claiming 23HZ -/+3db im sure it should perform a bit better. I am wondering if overall room accoustics may play a big part. I know when I play in my band its incredible how much the bottom end of my kick drum can differ from one room to the next. Is there any rule of thumb of room charictoristics which alter subs performance at the bottom end ? I have laminate floors and large windows. Do rooms with Carpet, heavy curtains make things better or worse ?

Also, I should maybe mention the Frequency generator was an app on my iphone which I was using via airplay. Does airplay cut low frequencies at all ?

 

 

Joined: 27 May 2009
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RE: Subwoofer dropping off too early

Sounds like an intro to room acoustics is on the cards. Start here with my sig and search site for bass etc. Then the web. Do not underestimate the room acoustics, imo they are at least as important as any change in sub or its position. Break out the rockwool!

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Joined: 27 May 2009
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RE: Subwoofer dropping off too early

Sounds like an intro to room acoustics is on the cards. Start here with my sig and search site for bass etc. Then the web. Do not underestimate the room acoustics, imo they are at least as important as any change in sub or its position. Break out the rockwool!

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 Base trap Project -  http://www.whathifi.com/forum/home-cinema/corner-base-trap-completed-project?page=1

Andrew Everard's picture
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RE: Subwoofer dropping off too early

umbucker wrote:
Also, I should maybe mention the Frequency generator was an app on my iphone which I was using via airplay. Does airplay cut low frequencies at all ?

AFAIK Apple is as usual reticent about quoting audio specifications for AirPlay, but given a post here last year suggested there was a high-frequency cut-off, it wouldn't be surprising if there were to be a low-frequency limitation.

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AlmaataKZ's picture
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RE: Subwoofer dropping off too early

How are you measuring the output?

Lows in the region of 20 to 30 Hz for any sub, even much more expensive, are very hard to produce. likey the sub is producing a lot of harmonic distortion - can up to 20-30%. This means that say if you give it a 20Hz tone, the 40Hz (and 60 etc) harmonic will also be part of the output and be only a few (10-15) dB lower than the 20Hz tone. Now, your ear is more sensitive at 40 and 60 than at 20, so you will percive the 20hz less and 40 and 60 more. Now, the sub/room can resonate, say, at 40Hz, so this tone will shoot several times (another 6-12 dB) up and you end up hearing just the 40 and you can forget about 20 as it is completely masked by then.

illustation here, section 3: http://www.linkwitzlab.com/thor-measmt.htm

so it is not a trivial issue to try to reproduce (and hear, and enjoy) a 20Hz tone in a typical room. it is practically impossible.

because of that I advise that it is more improtant to get the part that is easier for the sub to play better. in other words do not try to get it to play 20Hz, just try to get it to play say down to 30 or 35 but with less distortion, more accurately. What you can try:

- reduce (!) the vol level on the sub, this will reduce distortion and effects of resonance

- change its position, this may reinforce its output for certain frequencies and/or even out the peaks/troughs aroudn the room

- (as a last resort) try correction using e.g. antimode 

Edit: just saw you later posts. if you are measuring with an iphone, the mic may be limited below 200Hz or smth by iOS. only some combinations of iOS version and apps AFAIK can bypass this limitation.

Andrew Everard's picture
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RE: Subwoofer dropping off too early

AlmaataKZ wrote:
Edit: just saw you later posts. if you are measuring with an iphone, the mic may be limited below 200Hz or smth by iOS. only some combinations of iOS version and apps AFAIK can bypass this limitation.

I got the impression he was generating tones by iPhone over AirPlay, and 'measuring' by ear Wink

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AlmaataKZ's picture
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RE: Subwoofer dropping off too early

Andrew Everard wrote:

AlmaataKZ wrote:
Edit: just saw you later posts. if you are measuring with an iphone, the mic may be limited below 200Hz or smth by iOS. only some combinations of iOS version and apps AFAIK can bypass this limitation.

I got the impression he was generating tones by iPhone over AirPlay, and 'measuring' by ear Wink

Ah, I see, you mean sending a 20Hz tone to the sub and not hearing anything out? it may be a combination of low output of the sub at this f and a room suck-out? as well as low ear sensitivity? and airplay cut-off? Any and all fo these are possible.

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RE: Subwoofer dropping off too early

Is it really possible to output and measure such low frequencies only using domestic tech?

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CnoEvil's picture
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RE: Subwoofer dropping off too early

I thought the SPL 1000R was very good indeed, but bought the 1200R for that extra depth.....though they were much less expensive back then.

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RE: Subwoofer dropping off too early

There are plenty of online sound files you can download to test out how low your sub can go.

While room EQ and acoustic treatment helps, I doubt very much it will improve 20Hz output. Room acoustics tends to dampen excessive bass, but it can't increase a lack of. EQ can bring you a more balanced sound, boosting dips and dampening peaks, but if the 20Hz point isn't something the sub has been designed to cope with, boosting may damage your sub.

Dont forget that with 23Hz being -3dB, that means your sub is probably starting to roll off around 30Hz, and by the time it reaches 23Hz it is then half the volume of the higher bass notes. 20Hz could be another couple of dB down, or maybe 3dB, which puts it at half the volume again. If you want decent 20Hz output, you need a sub that can reach flat to that point before it starts rolling off. So far I've been referring to sealed subs as they have many benefits over ported ones, but if you want a "quick cheat", look at the SVS range, their PB13 Ultra can be 'tuned' by plugging a series of reflex ports to either 20Hz or 15 Hz. Sealed subs (like your own) are easier to place with less issues, are more even in their response, and will sound cleaner throughout the entire frequency range. Due to their sealed nature, they don't produce any port noise either.

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RE: Subwoofer dropping off too early

RobinKidderminster wrote:

Is it really possible to output and measure such low frequencies only using domestic tech?

Yes, I use the sound check 2 cd with has lots of test tones and a radioshack spl meter.  I think the total cost of both was about £50.  The radioshack spl meters microphone responce drops off at low  frequencies below about 80 hz so you have to add correction to your readings.  

For 20hz you have to add about 6 db to your reading, for 30hz 5.5db, 40hz 5db and so forth up to about 80 hz.

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umbucker's picture
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RE: Subwoofer dropping off too early

Subwoofer moved problem solved. Nice deep bass !!  

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RE: Subwoofer dropping off too early

umbucker wrote:

Subwoofer moved problem solved. Nice deep bass !!  

Glad to hear it.

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RE: Subwoofer dropping off too early

Good news. As u move into different positions does the bass still hold up or are u only interested in a single listening position? The cause seemed to be room interaction as suggested by several posts. Moving listening position and/or sub position can put the listener in a sweet spot. I found this to be the case but I had to address room acoustics to give a larger sweet area. Acoustics is easy to understand but difficult to manipulate imo. Hope u enjoy yr media now. Cheers 

PS wooden floors, large windows, no carpets. As u say in yr op, this makes a huge difference.

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Mordaunt Short Mezzo System C - 8,5,1,9.Yamaha V2065. SonyS570. Panasonic TX-P42G20B., Sky HD 1TB. Garrard 86SB. PF30. Wii. WDTV Live. Harmony One. STAX300. QED cabling. Galaxy Tab 10.1

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 Base trap Project -  http://www.whathifi.com/forum/home-cinema/corner-base-trap-completed-project?page=1