Ultimate DIY quazi Watt/Puppy clone project - diyAudio
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Old 18th March 2007, 04:49 AM   #1
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Default Ultimate DIY quazi Watt/Puppy clone project

Hello everyone,

I am designing a new 3.5 way medium size floor standing project and I think that I may need a little help from a few of the veteran TL builders.

Since I have given my old Watt/Puppy quazi clones to my brother-in-law to use as mixing monitors I am in need of some new speakers. Also, the venue for my listening has changed and my high resolution reference system is now a headphone only system in my home office. I have a better listening environment in my home theater/family room and need the new speakers for movies but most of all music.

My quazi Watt/Puppy clone project was quite successful but now I want to push the envelope a little further. At least within the resources that I have.

The drivers for the project I already have as they were left over from other projects or were purchased recently.

Tweeter: Vifa D27TG-35-06 silk dome. Not super high end but a good sounding tweet with relatively low Fs.

Mid/bass: Silverflute W17RC38-S-08 6.5 inch wool cone mid/bass driver.

Woofer: Vifa P21WO-20-08 8.5 inch poly cone woofer that has very good sounding mid range and mid bass quality.

Baffle step woofer: Silverflute W14RC25-S-08 Wool cone mid/bass driver used as second woofer for baffle step and fast upper bass transients and cone material that blends well with mid range driver.

Here is a snap of a basic conceptual design model showing approximate sizes.
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File Type: jpg 38 inch shape and size study2.jpg (29.4 KB, 1913 views)
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Old 18th March 2007, 05:04 AM   #2
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Though you can't tell in the above picture the upper and lower cabinet are seperate and disconnected.

This general cabinet approach has been used successfully by Genesis and Verity and others. And to me this looks rather good. Improvments are the non parallel walls in the bass module.

My first quazi Watt/Puppy clone used aperiodic loading of the mid and woofer since they were being used in a small room and my higest priority was transient response instead of extended bass. They proved to have awesome sounding bass and I have gotten very used to the non ported bass sound and it's tunfulness.

Anyway, with the new speakers they will be used primarily with music in a room that is twice as big as the old room but still modest in size. And since they will also double as the fronts in the HT system I want a more extended bass range. But I still want the fast transients and good pitch differentiation of the aperiodics. So I have decided to go with a TL on the woofer only.

The Vifa P21WO has a Fs of around 28 Hz and my not be the ideal driver for a TL but it is what I have to work with. My rough calculations indicate that a straight TL would need to be about 80 inches in length but the cabinet size is about as big as I can have in the room and I can only get a 70 inch tapered TL. Still, I believe this is balpark enough to work.

The big question I have is how much mass loading will I need or will the taper be enough to allow me to shorten the TL by ten inches. ALso, the TL will have to have three bends.

Here is a rough sketch of the TL layout done to scale but not calculated exactly as a uniform taper, though that will be my goal. At least as much as possible when the design gets further along.

Since I don't have access to MathCAD I was hoping that someone that has access to Kings worksheets might be able to do a quick simulation on this. I want the bass to be strong so I don't want to stuff the line too heavily to shorten it if possible.

THe sketch unfortunately does not show the LT terminus exit through the front baffle but it will be there either as a complete opening or some vents for ML.
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File Type: jpg lower cabinet sketch1.jpg (25.5 KB, 1666 views)
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Old 18th March 2007, 05:16 AM   #3
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Just another picture of the general shape of the speaker without edge rounding.

Since for me the the cabinet construction is going to be the place that I can take this system to the next level of quality and try to best my last efforts I may use some exotic but relatively inexpensive DIY construction methods.

At the present I am considering the top cabinet out of a composite of epoxy resin and lead shot and skinned in and out with fiberglass and epoxy. If I decide to go with this extreme method of construction the bass module will also be of exotic constructin methods, but will also use inexpensive materials in keeping with the spirit of the design.

After I build the cabinets I will tune the aperiodic chambers for the mid/bass and baffle step drivers and then breakthem fully in and test them in the cabinet for frequency response.

My intent is to use LsdCAD to design the crossovers. THe last speaker crossovers were LEAP designed by someone else but worked very well using only general driver frequency curves. I hope with a little learning and more specific measurements I can get a little better results.
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Old 18th March 2007, 05:16 AM   #4
TerryO is offline TerryO  United States
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From the drawing it appears that you have placed the smaller midwoofer under the larger midwoofer. It seems to me that you would have better integration with the tweeter if the smaller midwoofer were placed beneath it, as beaming would start at a much higher frequency and would allow an easier transition. It might also allow you to use a lower order crossover, which some claim, is preferable.
You may have valid reasons for the layout that you've drawn, I'm just not sure I understand what they might be.

Best Regards,
TerryO
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Old 18th March 2007, 05:28 AM   #5
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TerryO,

Initially that is the way that I had the system with the smaller mid/bass driver acting as the main midrange. But the reason I have changed the order is three reasons. THe 6.5 driver has a smother high frequncy rolloff then the 5.5. Also, the cabinet volume for the upper baffle step woofer is not very big and I though the 5.5 driver would be closer to being critically damped then the 6.5 and may sound a bit more natural in the lower bass with the smaller space. The third is just my experience with 6.5 mid/bass drivers as they usually sound more natural in the lower midrange for some reason than 5 inch drivers. At least they do to me. This may just be a subjective preference on my part and I have heard some good sounding 5 inch mid/bass drivers.

Of course the smaller mid/bass should have a little better dispersion but the design is still in the conceptualzation stage and I can still swap these two drivers order if warranted.

Since the midrange driver will be rolled off around 120 Hz or so (I like the midrange to act as a wide range driver cover most fundemental frequencies) I figured it might do better in the smaller volume of the upper cabinet. Like I said this could change but eventualy I will have to make a decision.
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Old 18th March 2007, 05:31 PM   #6
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Here are some other pros and cons of the two mid/bass arraingment.

Having the 6.5 driver lower allows me to move a little more air in the bass so this is a plus for the 6.5 at the lower level.

But when I look at my listening priorities, to me the midrange and mid/bass are the most important quality.

I'm thinking that if I have the 5.5 in the lower placement it will do better in the volume space it has and sound more natural in the upper range of it's operation and still do well down low since as a baffle step driver it will likely be covering the range from as low as it can go up to around 300-600 Hz. I don't know exactly where it will be since I haven't calculated the baffle step yet.

The upper mid/bass will be high passed around 120 Hz or 100 Hz so effecting the bass quality of the upper mid/bass driver by being in somewhat less volume is not as critical in my estimation. It's all a bunch of trade offs but this combination seems the best to me. But maybe I am wrong.

Another aspect of the 5.5 for augmenting the lower bass is that it may be a little faster than the 6.5 due to lower cone mass so my hope is that it will add some very fast bass transients into the mix with the lower woofer.
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Old 19th March 2007, 11:20 AM   #7
sreten is offline sreten  United Kingdom
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Hmmm........

Seems to me there is nothing much "ultimate" about the arrangement,
and much of what you are suggesting is based on conjecture, not facts.

The drivers are not particularly suited to an all out assault on cabinet
quality. They are good value drivers, but also not expensive, so they
would suit a more compromised performance/effort approach.

The 5" driver as a BS driver ? ..........

Use it as the mid driver. Use the the two bass drivers in parallel.

There are various complicated options for implementing BSC and
the bass and midrange c/o points, it is not possible to generalise.

TL's are not suited to getting the bass from compact cabinets.

/sreten.
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Old 19th March 2007, 12:44 PM   #8
AMV8 is offline AMV8  United Kingdom
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Hi

I go along with all sreten says.

If it helps my experience is that is is best to put the treble and mid in the top box which can be made more rigid and have a high mass. Rigidity is very critical for the mid unit. You need to avoid any movement of the front and rear walls of the top box inparticular. I like the pyramid shape of the top box - which is what I use.

In the lower box I would try just one base driver in a sealed box and see how it sounds. My experience is that without access to measuring equipment and computer programmes it will be difficult to get rid of cououration in the base box if you use two base drivers. I am not saying that it can not be done, just that you need more patience than I have.

Don
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Old 19th March 2007, 10:38 PM   #9
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Sreten,

Perhaps my use of the term "Ultimate" was too general. I am talking about getting the "ultimate sound from these drivers with this cabinet. Not in an absolute sense. And getting relatively deep bass without BR alignments.

True, the drivers are not the best, but these are what I have and they are capable of very good sound. At least I know the Vifa drivers are. In fact, all to often I see high end speakers used in the DIY community in inferior designed cabinets. In fact, this is more the norm than the exception. It doesn't make sense for me to intentionally compromise the cabinets and make them of lower quality than I know how to make them since this is a DIY project and to downgrade the only thing that I have the most control over does not make much sense to me.

As for the 5 inch not being used as the BS driver I ask "why not" ?. Not because I want so much to use it as a BS driver but because I want the 6 inch as the mid/bass driver because it has a smoother top end roll off.

Can you give me any further reasons why I should just wire the bass drivers in parallel and not attempt to intitiate some sort of baffle step. There is also another good reason for using the 5 inch as the BS. Because the speakers will only be about 26 inches out from the wall I don't want more than 1-2 db of BS. I though the smaller driver would not excite as much air and might help to moderate the effect a bit.

It is possible that at the distance from the walls the speakers will be used I may not even need the BS. But since I want to cross the woofer at a low Fs I figured that crossover point would be far enough away from the BS frequency to reduce some of the problems of crossover interaction. I'm thinking if the lower crossover is at 100 Hz and the baffle step is around 400-600 Hz that I am at minimum two octaves apart at these two filter points. I can see that if the two points were very close there could be problems.

AMV8,

I think that you have misunderstood my design intentions. The tweeter and the mid will be in the upper cabinet. I have already ruled out a sealed alignment for this project and I only like critically damped sealed alignments. That required too big of a cabinet for this bass driver.

Also, the cabinet sizes cannot be any bigger or taller than these are so I have basically decided that the cabinet shape will not change. It's only a matter of how the innards are arrainged.

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Old 20th March 2007, 12:08 AM   #10
ttan98 is offline ttan98  Australia
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Default Baffle Step compensation

Questions to those more knowledgeable,

I thought when you apply Baffle Step(BS) compensation I think you have to apply at least to mid-bass as well as woofer, not just the mid-bass. No need for the tweeter I believe.

Does it mean BS apply to woofer does not affect the sound as much?

I have seen a x-over the designer applys BS before it reaches the the 3 individual parallel x-overs(for 3 ways).

anyone wants to answer this question?
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