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Thread: How to: Fast/Natural Bass?

  1. #1
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    How to: Fast/Natural Bass?

    I have been working on a project for awhile and I am approaching satisfaction. I am using an Altec 414c with a large Ess Heil air motion transformer. Imaging is not great due to the relative sizes of the drivers (12" & 7") but nothing the fans here are not used to! This is a dynamic and sweet sounding, very "fast" system. I am missing the bottom. I would like to go Three way - 3db at 35hz so essentially flat for the vast majority of music. I like rock and classical and will sacrifice the Home Theater shake for music. I love great transients, both attack and decay as well as a natural sound. I must keep the box below 12 cu.ft. and ideally between 5-8cu.ft. For the next five years or so I will be in a modest 14' x 17' room, open to another smaller room as room loading and distance usually enter the equation. Researching here many believe a horn loading is the way to go but I may have issues with stacking my 20" high mid/high combo on top- keeping the center of my tweeter about 42" high from the floor minus 16-1/2" leaves max 25-1/2" in the vertical dimension. While I can treat the bass as a sub and go beside, it would be nice to stack and save floor space. Also, it will likely be easier for me to build a 1/4 wave t-line than a horn as I have no experience with making a horn or for that matter a port. I have considered the Altec 416c but it may need a really big box. I have also considered a Jbl 2234H (a 2235 without the mass ring for more speed) and cross somewhere between 80-150hz. but that is quite flexible- what counts is integration and bottom! Suggestions? Many thanks!

    And I am not stuck on -3db @ 35hz either. I just wanted to go flat to 40hz before roll-off begins, the common rock and roll bass limit.

  2. #2
    Senior Member jcrobso's Avatar
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    My room is 14X17' with a double wide door on the long side & one on the end.

    For bass I have two JBL loaded home made "K" horns, works very well.
    My setup in on one of the 14" ends is your like this or on the other wall?
    There are plans available for different kinds boxes, reflex and horn. But you have stated a lacked of experience in box construction, do you know anyone that can help you with this?
    The actual size of the box depends on the speaker used, some work better in a 3~4 cu ft box. Bass horns sound great, BUT they are very large. One of the smallest Bass horns is the JBL C40, the box that makes up the horn is about 8 cu ft in size. There are many things to consider, many bass players use 4-10" speakers they feel that the small speaker gives them faster response. May be a box with dual 12" would give you what you are looking for, but you would have to build it.
    Bass boxes show up on eBay, but the cost of shipping can be more than the cost of the box.
    The other choice is to but a good sub woofer, and use it until you move.

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    In the lows much of what you hear is room related. To improve transient response and make a better bass presentation, removing room interaction a big part of it. Geddes gets room averaging below 100Hz by using multiple subwoofer locations, and this solution works quite well, as you average not only the frequency response, but the associated resonance times. For instance, the corner location might excite a mode with a long delay time, but if that sub is only one of many, and the others don't excite it, then only a small portion of that frequency is contribution from the modal response.

    Horns also work, by ensuring that you get the wavefront before the rest of the room does, and limits the excitation energy applied into the room for a given on-axis SPL, but in the bass, this means very large devices indeed, and all the associated complexity and cost.

    Which leaves us one more option, the open baffle. This would be a very good choice, but most JBL woofers are not suited to it. JBL likes strong motors, which means low Qts, and accordingly, a lot of damping at Fs. The older 2213/123A woofers work exceedingly well for OB, as they have both a low Fs and a high(ish) Qts. There's an abundance of information on the use of OBs at various resources online. Here's a project using that woofer OB.

    http://www.enjoythemusic.com/diy/031...pen_baffle.htm

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    Quote Originally Posted by jcrobso View Post
    For bass I have two JBL loaded home made "K" horns, works very well.
    My setup in on one of the 14" ends is your like this or on the other wall?
    There are plans available for different kinds boxes, reflex and horn. But you have stated a lacked of experience in box construction, do you know anyone that can help you with this?
    The actual size of the box depends on the speaker used, some work better in a 3~4 cu ft box. Bass horns sound great, BUT they are very large. One of the smallest Bass horns is the JBL C40, the box that makes up the horn is about 8 cu ft in size. There are many things to consider, many bass players use 4-10" speakers they feel that the small speaker gives them faster response. May be a box with dual 12" would give you what you are looking for, but you would have to build it.
    Bass boxes show up on eBay, but the cost of shipping can be more than the cost of the box.
    The other choice is to but a good sub woofer, and use it until you move.

    Thanks. I am aware the Vandersteen 2W is highly regarded and uses (3) 10" : any box & driver suggestions besides purchasing two of these? (a big financial stretch) to get that level of transient response? I am familiar with building boxes. I just never tried to tackle the appropriate curve of a horn or play around with tuning a port. Simple boxes, even tapered transmission lines I can do with confidence.

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    Quote Originally Posted by badman View Post
    In the lows much of what you hear is room related. To improve transient response and make a better bass presentation, removing room interaction a big part of it. Geddes gets room averaging below 100Hz by using multiple subwoofer locations, and this solution works quite well, as you average not only the frequency response, but the associated resonance times. For instance, the corner location might excite a mode with a long delay time, but if that sub is only one of many, and the others don't excite it, then only a small portion of that frequency is contribution from the modal response.

    Horns also work, by ensuring that you get the wavefront before the rest of the room does, and limits the excitation energy applied into the room for a given on-axis SPL, but in the bass, this means very large devices indeed, and all the associated complexity and cost.

    Which leaves us one more option, the open baffle. This would be a very good choice, but most JBL woofers are not suited to it. JBL likes strong motors, which means low Qts, and accordingly, a lot of damping at Fs. The older 2213/123A woofers work exceedingly well for OB, as they have both a low Fs and a high(ish) Qts. There's an abundance of information on the use of OBs at various resources online. Here's a project using that woofer OB.

    http://www.enjoythemusic.com/diy/031...pen_baffle.htm
    I will look into this. Seems like an interesting solution. But your not saying I do not have the traditional main woofers under my mid/tweeter arrangement for the notes above say 60 hz? Then, if I am understanding you correctly, add a couple subs to take advantage of the natural room load/distribution, say the room corners (for instance)? And maybe stick with the previous idea of dual 10" or 12" in OB for the main subs below the mid/tweet for coherence? This will get complex but I am not one for simplicity if simplicity will fail to achieve the objective: looks like I may be in the market for (6) 10" drivers soon -thanks!

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    Quote Originally Posted by cerondipity View Post
    I will look into this. Seems like an interesting solution. But your not saying I do not have the traditional main woofers under my mid/tweeter arrangement for the notes above say 60 hz? Then, if I am understanding you correctly, add a couple subs to take advantage of the natural room load/distribution, say the room corners (for instance)? And maybe stick with the previous idea of dual 10" or 12" in OB for the main subs below the mid/tweet for coherence? This will get complex but I am not one for simplicity if simplicity will fail to achieve the objective: looks like I may be in the market for (6) 10" drivers soon -thanks!
    I'm having a tough time following your posting style, but what I'm saying is that for 100hz and down (even 200, but I'd not want to use multiple sources that high) the room is dominating, so horns or OB or multisubs all help reduce the room influence, but do so in different ways. I'm using a multisub approach currently and am very happy with it, but I've previously been very happy with OB bass too.

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    Quote Originally Posted by badman View Post
    I'm having a tough time following your posting style, but what I'm saying is that for 100hz and down (even 200, but I'd not want to use multiple sources that high) the room is dominating, so horns or OB or multisubs all help reduce the room influence, but do so in different ways. I'm using a multisub approach currently and am very happy with it, but I've previously been very happy with OB bass too.
    I know I can muddy up questions but I appreciate your input and I think I get it:
    Open Baffle- good, Multiple woofers in different locations- for smoothing time and frequency response, particularly below 100hz is good. Open baffle seems the way I would like to get started. I can always add more low frequency drivers as required. I remember listening to both the 406-8y 10" (bolero) as well as the 414c in open baffle before deciding on the quickness and transparency of the 414's with the Heil tweeter. The 406-8y had a 'thicker' and more natural full sound that did not make the choice an easy one. Unfortunately the 406's (Fs 28hz) can no longer be reconed. I will buy three other likely candidates and low pass filters, including the 123A you mentioned, to begin my process of elimination. Much has been written on OB in the recent past and is gaining a following for "natural" bass. Many thanks for your suggestion!

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    Administrator Robh3606's Avatar
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    I have also considered a Jbl 2234H (a 2235 without the mass ring for more speed) and cross somewhere between 80-150hz. but that is quite flexible- what counts is integration and bottom! Suggestions? Many thanks!
    Don't take out the mass ring. Just go straight up 2235 in 5 cubic ft tunned to 30hz or so. A pair will rock your world.

    Rob
    "I could be arguing in my spare time"

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    Senior Member Sootshe's Avatar
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    For OB design & components check out the Hawthorn Audio site. http://www.hawthorneaudio.com/

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    Senior Member Loren42's Avatar
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    I agree on multiple subs and a sealed cabinet for the mains.

    You want at least two or more subs and you will have to play around with the locations to get the best and most even response. Read Geddes for an understanding of the mechanism at play.

    For the frequency range (below 150 Hz) you really don't have to worry too much about "Fast & Natural". That's the job of the mid bass in the main cabinets.

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    Quote Originally Posted by Loren42 View Post
    I agree on multiple subs and a sealed cabinet for the mains.

    You want at least two or more subs and you will have to play around with the locations to get the best and most even response. Read Geddes for an understanding of the mechanism at play.

    For the frequency range (below 150 Hz) you really don't have to worry too much about "Fast & Natural". That's the job of the mid bass in the main cabinets.
    So far we have agreement on multiple subs. To that I would like to add a quote from Siegfried Linkwitz:"...the modulation envelope is subjectively preserved more frequently with the dipole..."
    "This correlates strongly with the impression that bass reproduced by a pair of dipole woofers is more articulate and thus more realistic of the recorded source."

    So many possibilities, so little time and money. Oh well, I will keep all this in mind. But I just broke the bank on this months play money and bought a pair of 2235H's. I Figured to add some versatility to my sub by getting a pair of drivers that could cross into the midbass regions with ease should I decide in the future to toy with a different midbass driver that reaches higher but not as low as the 414. For now I think I will shelve the OB woofer idea for another day. I like QW Transmission Lines, which is what my 414's are currently using- their just a bear to keep out/tune for internal resonances. Maybe run the 414's in a smaller cabinet- go dipole with them front and rear facing and make a 5 cu. ft. 1/4 wave rear firing T-line for the 35's. That way we gain in effect (pun intended) 4 woofers in the same space. The crossover for the sub can start out simplified as well until I get the tweaking and measurements down. ERSE will be glad to help with new crossovers. Thanks guys for the input. We are now at the point of making due, for the meantime, with what drivers I have. They now include a near mint pair of 2235H's, a pair of 414c's and some large AMT Heils. I can lay awake now and move on to dreams of dipole JBL's. Thanks goes to Dan Marshal for keeping safe my almost NOS 2235's at his house for so long!

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    Depending on what you mean by bass you could go with the subwoofer set up proposed or investigate the old Jensen Ultraflex (AKA Onken) which imho has the qualities of fast agile bass you are seeking - if I understand you correctly. I built mine 4 yrs ago and am absolutely delighted with their performance. Google Onken calculator if interested. These work very well with Altec 515 and similar. I am in fact using the Iconic 165-8G which is very similar to late versions of the 515. There are a number of eminence drivers that will also work well. My Onkens get down to 32Hz, but are rather large. (Almost 12 cu ft each including vent volume.)

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    Quote Originally Posted by kevinkr View Post
    Depending on what you mean by bass you could go with the subwoofer set up proposed or investigate the old Jensen Ultraflex (AKA Onken) which imho has the qualities of fast agile bass you are seeking - if I understand you correctly. I built mine 4 yrs ago and am absolutely delighted with their performance. Google Onken calculator if interested. These work very well with Altec 515 and similar. I am in fact using the Iconic 165-8G which is very similar to late versions of the 515. There are a number of eminence drivers that will also work well. My Onkens get down to 32Hz, but are rather large. (Almost 12 cu ft each including vent volume.)
    Thanks- Yes, I have read good things about this design. I will need to pass on that for now so I can use the drivers I already have. If only we could know what experience and inspiration would have us build in the future so we could start at the 'ultimate' and avoid all the indecisions/purchases and pitfalls/failed or partial successes along the way? Nah, we all enjoy the journey too much don't we?...

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    Quote Originally Posted by cerondipity View Post
    Thanks- Yes, I have read good things about this design. I will need to pass on that for now so I can use the drivers I already have. If only we could know what experience and inspiration would have us build in the future so we could start at the 'ultimate' and avoid all the indecisions/purchases and pitfalls/failed or partial successes along the way? Nah, we all enjoy the journey too much don't we?...
    Yes, sometimes the journey is the most fun part. I've just embarked on a set of major system changes which at times can feel like a step backward or two, but should eventually result in even better sound. I know people who periodically start all over just to relive the joy of discovering what works. I guess I am on at least my third iteration myself..

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