DIY Music (non-HT) subwoofer conundrum

WmAx said:

You seem to (1) leave out the fact for people that you will be using two of these in stereo, for computer speakers [and] (2) you forget the amp you are using outputs 225 watts into 4 ohm loads, and the driver is 4 ohms nominal.

-Chris

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I did mention the second sub (end of the last sentence), but forgot about the amps 4 ohm capability of the amp although that only increases output by about 2dB which seem inconsequential considering the SPLs previously mentioned.

avaserfi said:

I did mention the second sub (end of the last sentence), but forgot about the amps 4 ohm capability of the amp although that only increases output by about 2dB which seem inconsequential considering the SPLs previously mentioned.

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The point of (1) was not that you are using 2, it is that you are using 2 for computer speakers, in the near field.

-Chris

Arm ???????

These are quite interesting posts from WmAx......

You have almost convinced me to try ported subwoofers instead of sealed

Now I'm sitting here wondering if there's a third alternative. Looking at what subwoofer manufacturer REL calls ARM (Acoustic Resistive Matrix).... I have no idea how this works and how it's actually configured, other than it's a series of differently tuned enclosures..... is this merely a smart name for something that's not that smart.....

From what I have read this configuration will go lower by a considerable amount, without negative effects or reduction of SPL capabilities compared to a regular ported cabinet. I guess if you're using those with Jurassic Park you may feel the footsteps from the T-Rex at some 9 Hz =:-O
- Does anybody know what ARM is really about?
- Does it work? and is it applicable to DIY'ers? or is it way too complex?.....

Regards

Harald N

haraldo said:

These are quite interesting posts from WmAx......

You have almost convinced me to try ported subwoofers instead of sealed

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Just keep in mind that I speak in the assumption of an ideally engineered ported system - which is not likely to be the average commercial ported system.

N

ow I'm sitting here wondering if there's a third alternative. Looking at what subwoofer manufacturer REL calls ARM (Acoustic Resistive Matrix).... I have no idea how this works and how it's actually configured, other than it's a series of differently tuned enclosures..... is this merely a smart name for something that's not that smart.....

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I am not sure what this is; if you links to detailed diagram of this port system, please post it.

-Chris

Perfect Kappa 12 no insert sealed and low Qts 0.34 insert vented

Attached are the data for the Kappa perfect 12 no insert sealed and with the low, Qts 0.34 insert vented.

WmAx said:

I am not sure what this is; if you links to detailed diagram of this port system, please post it.
-Chris

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I have really tried to get down to that, but I have never been able to find anything, Once again.... I will try to find out.....

TLS Guy said:

Attached are the data for the Kappa perfect 12 no insert sealed and with the low, Qts 0.34 insert vented.

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I have modeled the vented low insert using a constructed rectangular section tunnel vent, so you can see how that changes the situation.

Box choice

I have finalized my decision on a 1.5L sealed enclosure. I chose this out of simplicity, as this is my first subwoofer build. I would say a passive radiator setup but I dont believe there is a Kappa passive radiator. I am aware that a correctly ported system increases SPL significantly, but I am also aware that if I mess it up I'll get too much delay, peaks, and a muddier sound, and I dont trust myself to get it just right on the very first try.

In regards to the amplifier, I am only running 1 driver, so the 500w plate would then probably be my best choice. I'm just going to have to do some old fashioned digging around for a deal on one in order to make the budget. If I find another ~500w plate amp somewhere else, I'll make sure to post it and see what the word is on it. Thanks again WmAx and TLS Guy, you both are very knowledgable about these Kappas!

EDIT:
I found this amp, with very similar features to the PartsExpress one. Does anyone have experience with this one?
http://www.oaudio.com/500W_SUBAMP.html

Headfoot said:

I have finalized my decision on a 1.5L sealed enclosure. I chose this out of simplicity, as this is my first subwoofer build. I would say a passive radiator setup but I dont believe there is a Kappa passive radiator. I am aware that a correctly ported system increases SPL significantly, but I am also aware that if I mess it up I'll get too much delay, peaks, and a muddier sound, and I dont trust myself to get it just right on the very first try.

In regards to the amplifier, I am only running 1 driver, so the 500w plate would then probably be my best choice. I'm just going to have to do some old fashioned digging around for a deal on one in order to make the budget. If I find another ~500w plate amp somewhere else, I'll make sure to post it and see what the word is on it. Thanks again WmAx and TLS Guy, you both are very knowledgable about these Kappas!

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Disclaimer! Chris has used the kappa, I have just modeled it!

Headfoot said:

I have finalized my decision on a 1.5L sealed enclosure.

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You mean 1.5 cubic foot, right? This, used with the 12VQ with no insert.

In regards to the amplifier, I am only running 1 driver, so the 500w plate would then probably be my best choice. I'm just going to have to do some old fashioned digging around for a deal on one in order to make the budget. If I find another ~500w plate amp somewhere else, I'll make sure to post it and see what the word is on it. Thanks again WmAx and TLS Guy, you both are very knowledgable about these Kappas!

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Just remember, you need the plate amp with the parametric EQ function in order to remove the peak response of the Kappa Perfec 12VQ used in a small 1.5 cubic foot cabinet. The PE unit has this function. While you would have vastly increased SPL output using a proper ported design, the sealed unit if built as instructed, will outperform a Velodyne DD12 in terms of distortion and SPL, and nearly match a Velodyne DD15. This is based on credible, standardized ground plane analysis of the highly respected Velodyne high end models in comparison to an Infinity Kappa Perfect 12.1(the non VQ version) in a small sealed cabinet.

-Chris

WmAx said:

Just keep in mind that I speak in the assumption of an ideally engineered ported system - which is not likely to be the average commercial ported system.
-Chris

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Do you consider the SVS products to be properly engineered?

How would you compare the Kappa Perfect 12 VQ in a vented box as opposed an SVS PB12-Plus or PB12-Plus/2?

-H

I would do the Kappa myself. Especially if I am building the enclosure.

haraldo said:

Do you consider the SVS products to be properly engineered?

How would you compare the Kappa Perfect 12 VQ in a vented box as opposed an SVS PB12-Plus or PB12-Plus/2?

-H

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The SVS products suffer obvious port compression problems; refer to the PB12-Ultra 12 tests on hometheatershack.com. The ported cabinet that I recommend at minimum for the Kappa Perfect has very little port compression in comparison, due to a substantially higher port cross section to lower port air velocity. I also can not know the upper bandwidth that the SVS products can be used, but with the internal acoustical dampening that I recommend, a higher uppper-bandwidth without loss of fidelity is possible, as what can be expected with the traditional dampening materials used in most commercial subwoofers. The Kappa Perfect driver is not the highest output driver available - it is simply an extraordinarily well designed driver with very low distortion and high linearity when used within it's limits. If super high SPLs are neeed, you will need to move to a special driver such as a TC Sounds high output unit or a JL W7 driver, used in a proper ported enclosure system. I will not recommend using even the W7 in a sealed system; you effectively throw away it's potential output capabilities.

-Chris

Whoops!

My mistake! I definitely meant 1.5 ft^3. 1.5L would be a little small eh?

That Bash 500W amp did also have a Parametric EQ, as you has said that was an important feature to remove that spike. I had the link on the previous post if you would'nt mind just quickly checking it to make sure I haven't missed something important in my inexperience?

Anyways, Im not totally ruling out the possibility of still using the ported system. I suppose if I took it slowly enough and checked over my designs with more knowledgable folk like yourselves I could minimize my chances of error. TLS Guy has been kind enough to provide the specifications for a ported system as well as the sealed as well.

If I can find time, I think I will also write up my process for the Ported set up too, and post it here.

It would be unfortunate to lose those SPL's if I could keep them and retain sound quality

haraldo said:

I'm just wondering about if it's worth the effort to DIY when you can get the AV123 MFW-15 at $600,- or two sub's for $1000...

http://av123.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=189&category_id=9&manufacturer_id=0&option=com_virtuemart&Itemid=37

Seems like something that's very tough to beat..... even with a DIY project.....
(I know they are not sealed. but still....)

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I think Haraldo hit upon something here with the price of do-it-yourself versus buying finished. Can you, for example, get the look and finish of a manufactured cabinet? I know my SVS finished in maple looks awesome and it is a centerpiece in our living room. I believe the cabinets are made out-of-house and probably come from China, but they are very well executed. When you put this with guaranteed good sound quality from a manufactured subwoofer it is a good argument for buying a finished subwoofer. Are you talking about a home built subwoofer being comparable to something like a JL Audio top of the line subwoofer for half the price or something closer to an AV123 MFW-15?

Exit said:

I think Haraldo hit upon something here with the price of do-it-yourself versus buying finished. Can you, for example, get the look and finish of a manufactured cabinet?

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This depends, of course, completely upon the skill of the individual doing the work. Personally, I have never had a problem obtaining factory quality finishes. Years ago, before I tried my first final finish, I used a scrap 'dummy' box to practice until I was confident that I could get a satisfactory finish quality.

When you put this with guaranteed good sound quality from a manufactured subwoofer it is a good argument for buying a finished subwoofer. Are you talking about a home built subwoofer being comparable to something like a JL Audio top of the line subwoofer for half the price or something closer to an AV123 MFW-15?

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The DIY designs that I recommend are in the JL Audio home subwoofer quality range. The specific slot loaded Infinity Kappa Perfect 12VQ design that you may notice me suggesting every now and then will very likely outperform the JL F13 substantially in the lowest octave, so far as distortion vs. SPL, if you build it exactly as I suggest. However, the F13 will have a little more SPL as compared to this specific DIY unit in the upper octave(40-80Hz). You could say it's an even wash between the two, unless you favor an advantage in one range as compared to the other.

User avaserfi on this forum has built the project to my exact recommendations; if you are curious of his subjective assessments, as well as his measured results, ask him what he thinks of the performance as compared to high-end commercial subwoofers and regular line commercial subwoofers that he has used.

-Chris

Exit said:

I think Haraldo hit upon something here with the price of do-it-yourself versus buying finished. Can you, for example, get the look and finish of a manufactured cabinet? I know my SVS finished in maple looks awesome and it is a centerpiece in our living room. I believe the cabinets are made out-of-house and probably come from China, but they are very well executed. When you put this with guaranteed good sound quality from a manufactured subwoofer it is a good argument for buying a finished subwoofer. Are you talking about a home built subwoofer being comparable to something like a JL Audio top of the line subwoofer for half the price or something closer to an AV123 MFW-15?

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I don't think the reason for building speakers is primarily price. Although I do believe that the skilled builder can get better value for money that buying off the shelf or Net.

The reasons for building are to have the satisfaction of building your own quality product. Along the way you increase in knowledge and skill. With progression and guidance you will be able to come up with innovative and creative solutions to your problems. You can create novel designs that are not on offer commercially.

After all what is on offer, are really lots and lots of variations of sealed and and ported reflex enclosures. The skilled hone builder and designer has a lot more options to experiment with. If your experiment fails, you are just out some time and wood and you leaned something. Those drivers can be recycled into another project, and the crossover parts add to your parts inventory for projects down the road.

Now there are unusual products that appear from time to time, but all too often problems are left unsolved or not properly executed due to lack of understanding and or cost. I'm pretty sure we have had one of those on offer lately.

As far as finish, that is up to the skill of the builder. Again the constructor does not have to make do with the finishes on offer, but can choose his finish to fit his own interior design. My interior designer daughter, had me finish my rig in the house trim finish, and I believe she was correct. She specified a mat finish, not glossy.

http://forums.audioholics.com/forums/showthread.php?t=42780

So as the DIY designer gains experience he can push the boundaries of what is possible, and enjoy unique and innovative systems, that would have virtually no chance of seeing the light of day in the commercial world. At the same time design and finish it to their personal space.

For those that want to pursue it, it is a lot more rewarding, than "what manufacturers should I be looking at." At the same time, it has been shown that woodworking and construction is excellent low intensity, continuous exercise.

It is my belief that we are all called to be skillful people.

Looking at the cabinet that Avaserhifi created, there's certainly some bracing!!!!! and this is definitely not a simple cabinet to assemble.... Thinking of my 10 thumbs (well 6 perhaps) in woodworking, I'm not sure how this final result would be, although you get very far with top notch tools or pre-cut panels at exact dimensions....

Some of us may be so lucky that they have large storage rooms right behind the front wall of the main listening room... (At least I am) What I'm really dreaming of is to create one solid 4 inch plywood baffle to line up with the sheetrock wall, and put some 4 and even 6 12" drivers at each side in an infinite baffle....
No large boxes, almost "unlimited" SPL, just add as many drivers you want that fits in the vertical line between the floor and the ceiling (that's a lot of drivers, probably around 8 Kappa Perfect 12 VQ) and you can probably make this cheaper than a high end sub.... 4 drivers at each side is still less than $2000 in drivers.
I just have to get my wife to agree to move a wall first

This is something many DIY'ers could do, because nothing will really be visible except for the sub grill....

And if it's done neatly, you can start off with a few drivers and add some more whenever you get more cash..... you need some dummies in the holes for the unused drivers... When you get more drivers, just remove the dummies and add the new drivers, and then you get more SPL capability and/or less distortion.....
You could never buy that "off the shelf"

Now, I think such a project would be interesting. Anybody built a line-source sub around here?

This is what I'd really like to do, I've heard that Richard Vandersteen has got something like this in his own house.....

haraldo said:

Some of us may be so lucky that they have large storage rooms right behind the front wall of the main listening room... (At least I am) What I'm really dreaming of is to create one solid 4 inch plywood baffle to line up with the sheetrock wall, and put some 4 and even 6 12" drivers at each side in an infinite baffle.... :

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If you do this, and this baffle mates with a normal wood-studded wall structure, then you need to build this baffle into a mechanically de-coupled suspension mount. Failure to execute this step will result in the subwoofers exciting the structural resonances of the house to a higher magnitude. If the baffle will mount to concrete or masonry wall, then a de-coupling system would not be beneficial.

-Chris

WmAx said:

The SVS products suffer obvious port compression problems; refer to the PB12-Ultra 12 tests on hometheatershack.com.
-Chris

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Well looking at these measurements of one PB13-Ultra measured in a wide-open-space...
Darn if there's very much compression going on here.
And < 10% distortion at 105db @ 20 Hz
http://www.avtalk.co.uk/forum/index.php?t=msg&th=22950&start=0&rid=0&SQ=0

If the Kappa Perfect 12 VQ in the ported cabinet is even better than this, I'm stunned.....

WmAx said:

If you do this, and this baffle mates with a normal wood-studded wall structure, then you need to build this baffle into a mechanically de-coupled suspension mount. Failure to execute this step will result in the subwoofers exciting the structural resonances of the house to a higher magnitude. If the baffle will mount to concrete or masonry wall, then a de-coupling system would not be beneficial.

-Chris

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Thanks!, but still probably easier than some of the very complex sub cabinets.....