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What DIY sub to match with Maggies for music??? (1 Viewer)

Jack Gilvey

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There's really some good stuff all over that SL site, in case anyone didn't want to wade through:
The conventional closed or vented box design, that is used for the majority of loudspeakers on the market, contributes significantly to the room problems below 200 Hz. These designs are omni-directional radiators and they tend to excite a maximum number of room resonances, particularly when located in room corners. While this adds to the perceived bass output at certain frequencies, it can lead to a falsification of the recorded material, namely when the room resonance decays more slowly than the original sound. In general, the low frequency response of omni-directional speakers in small rooms is quite non-uniform. Attempts to treat the room with absorbers will make only marginal differences unless very many absorbers or large absorbing surfaces are used. It is best to attenuate peaks in the bass response with parametric equalization. Holes in the response cannot be filled in (Ref. 1).
By far the most uniform response in the range below 200 Hz is obtained with an open-baffle, dipole or figure-of-eight radiating source. Because of its directionality, the dipole excites far fewer room resonances than an omni-directional source. The difference in bass reproduction is startling at first, because we are so used to hearing the irregular and booming bass of the typical box speaker in acoustically small rooms. Quickly one learns to recognize the distortion of this combination and it becomes intolerable.
There ya' go. More detailed than I could muster ;)
 

Jack Gilvey

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I put together a test baffle today from some 3/4" marine ply, basically the same as Linkwitz's sketch g below:

The baffle is 2'W x 4'H with 8" wings (d) extending back. Two DPL12's are mounted on the bottom half of the baffle.
So far, very cool. The smoothness is impressive, definitely a unique character (or lack thereof)to the sound, and it seems to go at least as deep as my PR sub (very surprizing given the lack of any eq), although it can't get as loud before overexcursion. I settled upon a 6-ohm resistor across one unwired VC of each driver resulting in a Qts of .5 or so (resistively damped operation, or RDO), and the wired coils are paralleled presenting a 4-ohm load to the amp.
Anyway, I've just begun to play with it, I'll try and get some FR numbers soon if I can find my disc in all this mess.
 

Mark_E_Smith

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You guys have my interest in building a IB sub. I really like tight bass that sounds real more than I care for the "dinosaurs footsteps". Can you modify the PE plate amp to give the eq nessesary for a flat response? Or do you design a active x-over ahead of the plate amp. Linkwitz tri amps all of his stuff and thats not practical for me, but I was planning on bi-amping (subs + rest of system) So how about a thread on designing the most realistic sounding sub for music? I would be very happy with a tight 105 dB out of a sub.
 
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Well, I got in touch with Dan at Adire Audio and asked him if they would be releasing any type of dipole kit for the DPL12's. Here is what he told me......

****START OF EMAIL****
Stephen,

Thanks for the e-mail! We're probably not going to come out with a dipole
system design for the DPL12 in the foreseeable future, because of the need
to custom equalization to get decent bass response. Rather we'd recommend a
sealed box in the 3 cubic foot range to best blend with the Maggies.

Thanks again,

Dan
Adire Audio

****END OF EMAIL****


SO, here I am. I would probably like the sound of a dipole much better but there isnt very many plans to choose from as far as I can tell. The plans I have seen didn't look like they could be very wife accepting or be able to pose as a nice endtable. Sure I could throw it up on some legs and use it as a end table but.....thats not going to cut it with the wife if ya know what I mean.

Unless anyone has any other designs (or at least pics) for a good looking dipole sub I'll prob take Dan's(and a few people here) advice and go with a small enclosed sub.

Anyone seen any real good looking enclosed subs lately that looked like a endtable???

What is everyones opinion on which enclosed (diy or kit) sub is the most musical. A kit would be nice but a full diy is ok too.

Thanks for everyones help!!!
STEPHEN
 

Brian Bunge

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Stephen,
Check out the sub in this thread! It's probably a bit large for your use but it could be downsized for use with a Shiva. Otherwise, I think it would be best if you went with Adire Audio's Rava.
Brian
 
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Brian, thanks for the link!!!! That sub is AWSOME!!! I wonder how it sounds, good I'm sure!!!

Let me ask you guys this....

I've been advised by a few people that an enclosed sub thats about 3 cubic feet would be a pretty decent mate for maggies. What if I were to make a endtable similar to the one in Brians link but instead of using the entire inside volume of the cabinet block it off where ever needed so that the sub was enclosed in 3 cubic feet instead of the 9 or so feet that this cabinet is.

Also - a few people have suggested the Rava....for $400 complete with speaker and amp is it really that good??? Is it a nice clear, tight, musical sub??? I dont care much for the design(or lack of) but if its really that good its would be a steal for $400. Are there any namebrand subs that it would sound similar too???

Thanks guys,
 

Dustin B

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Rather than blocking off some of the cabinet, why not choose a driver that can make use of the space. Step up to a Tempest or Maelstrom in a sealed enclosure. From what I remember Dan saying the Maelstrom provides the cleanest most effortless bass (compared to the Shiva or Tempest).

I'm not sure if this is clear to you or not Stephen so I'll throw it out incase it isn't. 3ft^3 isn't some magic number for every driver. Depending on the T/S specs of the driver, different box sizes result in different overall Q values. For the maggies you'll want a Q as close to 0.5 as you can get. Take the box volumes required for a Q in the 0.5 range for each of the drivers. Then compare how well that size can be made into an endtable and how much the cost will differ. Then make your call.
 

Richard Greene

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Mar 5, 2001
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"By far the most uniform response in the range below 200 Hz is obtained with an open-baffle, dipole or figure-of-eight radiating source. Because of its directionality, the dipole excites far fewer room resonances than an omni-directional source. " from Sigfried Linkwitz web site

This reads like "over-the-top" advertising copy.
Where are the data to back up the claims of
"By far the most uniform response ..."
Does anyone reading this have bass frequency response
data, measured from the listening position, that proves
a dipole subwoofer generates a much flatter frequency
response than a conventional subwoofer?

I'm looking for data collected by measuring a slow sine wave frequency sweep from the listening position -- not 100Hz. repeating tone bursts that have little correlation with what a subwoofer is actually used for (sustained bass frequencies under 80Hz. from instruments such as bass guitars and organ pedals).

Dipole proponents would have us believe dipole subwoofers are so much better than conventional subwoofers that the only logical reason for anyone to buy a conventional subwoofer is because they can't afford a dipole subwoofer (extra drivers are required to offset bass cancellations -- perhaps triple or quadruple the number of drivers of a
sealed or ported enclosure!)

Dipole proponents would have us believe dipole subwoofers create such directional bass that very little bass will bounce off the walls, floor and ceiling to create those nasty standing waves that cause a very uneven distribution of bass in home listening rooms (few of the other posts address room acoustics at all).
But just how does a dipole subwoofer change sub-80Hz.
bass frequencies from omnidirectional to directional,
other than having cancellations at the sides of the dipole panel? Perhaps reduced output on the sides of the dipole would reduce the strength of the side-wall-to-side-wall room modes. If so, is that a good thing to do? Because even if you could completely cancel the side-wall-to-side-wall room modes, all that would accomplish is to make the lower in frequency front-wall-to-back-wall room modes and the higher in frequency floor-to-ceiling-room modes easier to hear ... and more annoying than before!

The primary room acoustics problem in home listening rooms is the lack of modal density. There are not enough room modes in the 30 to 80Hz. range for our ears to smooth out the frequency response. (Above 200Hz. there are usually so many room modes that our ears can smooth the frequency response and we are rarely aware of how uneven the frequency response really measures). So eliminating one of the room modes is really not what we want to do.

What we really want to do is to use bass traps to reduce bass frequency reflections to reduce the peaks and troughs
of room modes throughout the listening room ... or use an equalizer to reduce the frequency response peaks measured at one specific listening position. A good combination is using a bass trap or two in every available room corner and using parametric equalization to further reduce bass frequency peaks heard at the primary listening position.
That combination should be able to generate a bass frequency response better than +/-5dB measured using a slow sine wave frequency sweep at the listening position

Tightening the bass frequency response deviations is mandatory for creating "musical" bass -- the brand of subwoofer is not very important because room acoustics dominate the sound quality under 100Hz. A typical room has a bass frequency response of +/-10dB or worse measured using a slow sine wave frequency sweep from the listening position.

If a dipole subwoofer can improve the bass frequency response as much as proponents seem to believe, I wonder
why there are so few commercial dipole subwoofers?
Are the companies that sell high-end subwoofers, for example, run by fools who just don't realize how great dipole subwoofers are? Or are dipole subwoofers not as great as their proponents would have us believe?

There is nothing other than data from a comparison of a dipole subwoofer and a conventional subwoofer in the same listening room that will answer the questions I've posed.
Just how good is the frequency response of a dipole subwoofer.
We need data.
Not opinions or theories.
 

Jack Gilvey

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Looks like you've got some building and testing to do. ;)
If a dipole subwoofer can improve the bass frequency response as much as proponents seem to believe, I wonder
why there are so few commercial dipole subwoofers?
Are the companies that sell high-end subwoofers, for example, run by fools who just don't realize how great dipole subwoofers are?
Probably because there's so little SPL available compared to a ported or even a sealed for a given driver, very cost-ineffective.
 

Peter Jessee

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The RAVA is a screaming deal at $400. I've had one for about a year, and it was the single item that pushed my system from "OK" to really satisfying. The RAVA is tight and fast enough to sound very real on music, and it blends very well with my NHT SuperOnes for jazz and rock. It is also great for movie effects, but that is pretty easy compared to music.

Be aware, if you haven't had a powerful sub before, that room placement is CRUCIAL to success. I tried many different locations in my room, and had lots of problems with obvious room modes until I got out the tape measure and put it the RAVA dead center on the long wall in my room. Bingo, my 1/3 octave test showed a +/- 2.5 dB response from 25 to 80 hz, and the sound quality went from boomy to real.

It's amazing how much more realistic music becomes when you accurately reproduce all the fundementals, and the hall resonance. Good luck with your search!

Peter
 

Hank Frankenberg

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Richard, please post Siegfred's reply. It will be very interesting.
Regarding your question about why manufacturers don't offer dipoles, Jack hit on a significant reason: if it takes 2X or more drivers to equal the SPL of sealed or ported subs, the final selling price of such a sub would eliminate much of the potential market. Also, though, I propose another factor: the dreaded WAF! Twofold: first, the size of the cabinet to hold that 2X or more number of drivers, and second, the LOOK of such a beast. The examples I've seen are definitely not decorator scheme friendly, with their sometimes exposed drivers and "different" looks. In my personal opinion, this WAF issue is a larger deterrent to mfgrs than the selling price issue.
 

Jack Gilvey

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To get the same SPL, you'll need about 4X the driver area as for a sealed box, somewhere near 6X to 8X compared with a high performance PR/reflex.
Yikes. None of which addresses Richard's performance/FR questions but does, I think, go a long way toward explaining why it's not done commercially. Especially in today's double-duty music/HT market, SPL is king.
 
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ok guys, I've been doing a little research and talking with Dan at Adire and he sent me some cabinet designes for the Shiva and Tempest.

there is one cabinet for each that could easily be turned into a endtable. The Shiva has a cabinet design with a Q of .6 that is the right size for a endtable. The Tempest has a design that will also work good as a endtable but its Q=.707

There is a Tempest design with Q=.577 but its 35" tall which is way to high for a endtable. Most endtables are between 23"-26", a 35" sub would be almost a foot higher than the armrest.

I guess what it boils down to is which driver I would rather have. The cost of the 2 is about the same so money isnt a factor. Which one of these subs do you think will match a maggie the best? I've never heard either so I'm kinda hoping you guys can give me your opinions on these 2 set ups. My main use of this sub will be music with clean, clear, and tight bass. Bass guitar, ect and I'm hoping for a very musical sub. SPL is nice for movies and I do watch some movies but I've been watching movies with 2 maggies for over a year....any spl is more than what I'm used to haha, so bringing the house down isnt a major concern.

What do you guys think???

Thanks,
STEPHEN
 

Dustin B

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You don't have to follow the Adire plans exactly. All that matters in the internal volume. Add to the depth and width dimensions to compensate for a reduction of hieght down to what you desire.
 
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Well, the only prob with that is the cabinet with a Q of .577 is also 24x24 wide and deep so you really couldnt add there either.

What about this....

There is the design that Q=.577 and it is 24x24x31 + 4" feet that make it 35" tall.

Then there is the next on with a Q=.707 and it is 21x21x21 + 4" feet for a total height of 25". This is really the perfect size for a endtable sub BUT it seems as though the smaller the enclosure the higher the Q. I would have thought opposite than that but I guess I learn something new everyday.

Could I take the .707 box and add to the width and depth making it 24x24 just like the .577 box but keep the same height which is 21" + feet??? Wouldnt that put the Q somewhere between .577 and .707??? How would that affect the sound??? Do I need to keep the "Q" at thier set amounts? Are the speakers tuned with the .577 and .707 to where if I get away from that its going to mess up the sound????

In case you guys cant tell I dont know much about tuning a driver with a cabinet but I'm trying to learn lol

Thanks,
STEPHEN
 

Jack Gilvey

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Are the speakers tuned with the .577 and .707 to where if I get away from that its going to mess up the sound????
Nope, not at all. :) That's why a sealed is so easy, the exact volume isn't critical. I think you'd be very happy with anything in that range. I think you'd be happy with a sealed Shiva also, given that you're already living with the dynamic limitations of the Maggies. If the Shiva Q = .6 design works best for you size-wise, give that one a shot. :emoji_thumbsup: And remember, it's not the dimensions that are important in a sub, it's the net internal volume (Vb).
 

Dustin B

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That would be internal volumes of around 120, 160 and 240 litres. Yes, the Q of the 160 will be inbetween .577 and .707. I don't know how to calculate what 160L would be though.

The Rava has a Q of 0.67.
 

Brian Bunge

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Dustin,

Unibox tells me that a 160L enclosure has a Qtc=.638 with no fill and Qtc=.563 with heavy fill.

Brian
 

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