# zdt idea......



## adio (May 27, 2009)

i always wanted to one day own a stereo system with enough bass that having a subwoofer would be optional. everybody thinks 12's, 15's, 18's and now 21's, will forever be in their homes!! i was looking at the zdt 3.5 build on the parts express project page thought that ' hey, why don't i use 8" woofers instead of 7" and maybe have the enclosure tuned to 35 - 38Hz?!?!' is that a great idea???

also would there be an audible difference use a bigger tweet ( from 3/4 inch to 1 or 1.5 inch)??


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## GranteedEV (Aug 8, 2010)

adio said:


> i always wanted to one day own a stereo system with enough bass that having a subwoofer would be optional. everybody thinks 12's, 15's, 18's and now 21's, will forever be in their homes!! i was looking at the zdt 3.5 build on the parts express project page thought that ' hey, why don't i use 8" woofers instead of 7" and maybe have the enclosure tuned to 35 - 38Hz?!?!' is that a great idea???
> 
> also would there be an audible difference use a bigger tweet ( from 3/4 inch to 1 or 1.5 inch)??


It's not a great idea at all. Different drivers have different behaviour. the 8" driver may begin to break up or roll off too early. This will force you to likely use the dome midrange with a lower crossover, reducing power handling. Additionally, it may have a different sensitivity leading to poor driver integration. Remember, the midrange is crossed over at 800hz, which is rather high for most 8" woofers as it is, never mind more affordable ones.

A larger tweeter would also change the directive nature of the top end, which again will mess up the crossover. That doesn't even address the fact that it would be flat out a different driver. Smaller tweeters are normally desired because the more effectively reproduce high frequencies. Larger tweeters are a compromise designed to allow lower crossover frequencies because more 2-way speakers can't cross high. The dome midrange in the ZDT is designed to be crossed higher up (3.5khz) smooth power response is vital when it comes to crossing a tweeter to a midrange.

Then there's the matter of BSC. If you can't fit the 8" drivers into the original baffle, your baffle step frequency will change with the baffle. The .5 woofer in the ZDT is rolled off with respect to the 9" baffle, and by widening the baffle you would need a different component value for the baffle step compensation. Else you would have a dip in response somewhere. 

If you're interested in a more full range DIY loudspeaker, it's possible. But don't expect to just pick a certain design and alter it while expecting good results. You need to pick a different design that can actually dig deep on its own. Personally I feel active is the way to go with 3 way speakers anyways, because the inductors for a good air core at bass frequencies get very expensive, and people usually end up with settling for iron cores.

Here is a speaker you may wish to consider with bass down to deep frequncies:

http://speakerdesignworks.com/Statements.html

Like I said, it uses iron cores over air cores, but people apparently don't seem to notice the difference and that's what really matters.

And if you want to build your own crossover, you need a ton of measurement equipment and strong fundamental understanding of speaker design. From the sounds of it, you have a long way to go in learning if that is your goal.


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## hearingspecialist (Mar 15, 2010)

I have a set of towers that have extension and can be used all day every day without subs. TWW with Bi-Polar T's. 8" drivers that were chosen to meet the enclosure specs, crossover demands, and response. 

Point is it can be done with proper driver choice but I still can't come close to the output while maintaining clarity when using dedicated subs. And that's going to be the nuts and bolts of it, the trade off. If your not a loudness monster and won't be playing at THX reference levels then its way possible to have towers that have it all even in a 2-way setting. My case was 3K crossover point at 12db per octave 2-way tuned to 32hz or low C.

Check my pics out under the DIY section under "sharing latest project"...

Even though my towers are super capable, they are still setup for THX style listening crossed over at 80hz and my stereo subs providing the crazy low extension at super high levels. When calibrating with my Yamaha YPAO it sets my crossover at 40hz allowing the towers to play that low, so it can be done but doesn't mean I have it setup that way.


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## 1Michael (Nov 2, 2006)

No. You can't change out drivers without changing the Xover as well.


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## GranteedEV (Aug 8, 2010)

hearingspecialist said:


> I have a set of towers that have extension and can be used all day every day without subs. TWW with Bi-Polar T's. 8" drivers that were chosen to meet the enclosure specs, crossover demands, and response.
> 
> Point is it can be done with proper driver choice but I still can't come close to the output while maintaining clarity when using dedicated subs. And that's going to be the nuts and bolts of it, the trade off. If your not a loudness monster and won't be playing at THX reference levels then its way possible to have towers that have it all even in a 2-way setting. My case was 3K crossover point at 12db per octave 2-way tuned to 32hz or low C.
> 
> ...



One person at another board has an interesting tower setup.

It uses 

Two 10" Seas Excel woofers per speaker (total = 4 for the pair). One of them (the upper one) is used for baffle step compensation as well, so its top end rolloff is rather high. Few 10" drivers can be used as high AND low as this one though. Acoustic Elegance, Scanspeak, SB Acoustics and Peerless may have some that can however. They're in transmission lines with F3 of 27hz and in room F3 of 20hz. By using the 10" woofer as the BSC woofer instead of the way most normal 2.5 ways are done such as yours, the demand on the small woofers to reproduce midbass is reduced. All these crossovers are done actively.

Of course, one might argue that 10" drivers with fs = 20 are unofficial subwoofers. But the thing that stands out is that by being a dedicated 3.5 way of sorts, the output capability is very high in the full bandwidth. I think 2.5 ways are a bad idea if output is the goal. It's not just a receiver 80hz crossover with subwoofer. The region from 80hz - 300hz has a lot of demand on both amplifier and driver that people neglect.


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## hearingspecialist (Mar 15, 2010)

Agreed! A 10" I would not do, even my 8's are over doing it. I sometimes wonder what would have happened if I used 3 6.5's instead but have to admit I love the capable feeling of knowing they can handle whatever I throw at them. I guess thats satisfaction in a way, and love the sound of a well controlled setup.

Can you provide a link to that build so I can check it out???:gulp:


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## GranteedEV (Aug 8, 2010)

hearingspecialist said:


> Agreed! A 10" I would not do, even my 8's are over doing it. I sometimes wonder what would have happened if I used 3 6.5's instead but have to admit I love the capable feeling of knowing they can handle whatever I throw at them. I guess thats satisfaction in a way, and love the sound of a well controlled setup.


Hehehehe...

i'm thinking more along the lines of... 12" is the right size for a woofer in a dedicated 3-way :whistling:

Like one of these cute little beasts:


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## adio (May 27, 2009)

GranteedEV said:


> It's not a great idea at all. Different drivers have different behaviour. the 8" driver may begin to break up or roll off too early. This will force you to likely use the dome midrange with a lower crossover, reducing power handling. Additionally, it may have a different sensitivity leading to poor driver integration. Remember, the midrange is crossed over at 800hz, which is rather high for most 8" woofers as it is, never mind more affordable ones.
> 
> A larger tweeter would also change the directive nature of the top end, which again will mess up the crossover. That doesn't even address the fact that it would be flat out a different driver. Smaller tweeters are normally desired because the more effectively reproduce high frequencies. Larger tweeters are a compromise designed to allow lower crossover frequencies because more 2-way speakers can't cross high. The dome midrange in the ZDT is designed to be crossed higher up (3.5khz) smooth power response is vital when it comes to crossing a tweeter to a midrange.
> 
> ...


sounds like you don't like my idea.............


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## adio (May 27, 2009)

hearingspecialist said:


> Agreed! A 10" I would not do, even my 8's are over doing it. I sometimes wonder what would have happened if I used 3 6.5's instead but have to admit I love the capable feeling of knowing they can handle whatever I throw at them. I guess thats satisfaction in a way, and love the sound of a well controlled setup.
> 
> Can you provide a link to that build so I can check it out???:gulp:


hows the mids and highs on your speakers, on a scale form 1 - 10? do u have a build thread of the drivers, parts for the crossover and enclosure measurements?


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## hearingspecialist (Mar 15, 2010)

Sorry for late response, I've been experiencing some drama on another site...

My woofs were chosen for their Vas first, their high efficiency 2nd, and their upper midrange response with Dayton 2-way 3K crossovers with their plug placed for 4ohm woofage connector (you can alter the x-over for 8ohm or 4ohm woofers) third. BTW, these crossovers are probably 5"x8" in size and blew me out of the water with how big they are. I also have a set of these on the backside using just the tweeter output for my bi-polar morel that my pics don't show and show my modeling x-overs. Specs of woofers:

*Power handling: 80 watts RMS/115 watts max * Voice coil diameter: 2" * Impedance: 8 ohms * Frequency response: 31-7,000 Hz * Magnet weight: 30 oz.. * SPL: 91 dB 1W/1m * Vas: 2.44 cu. ft. * Xmax: 2.8mm * Qms: 6.51 * Qes: .27 * Qts: .26 * Fs: 31 Hz.*

My woofers play very well and the midrange is super nice and i contribute that to all the modeling clay and ceiling tile/aperiodic placement that yeilds a very great sound naturally without equalization. I have YPAO set to its "Flat" configuration and they can take anything thats thrown at them. I can play a 20hz sine wave thru them without them really caring (even though tuned to 32hz) and anything around the 30hz range is crazy efficient. I do have them currently set up to play from 80hz and up for THX style listening and let my stereo subs do the rest (stereo DVC 10's tuned to 25HZ). I'm missing nothing in the upper midrange and my Dayton softdomes can blend wonderfully, and contribute this awesomness to the crossovers as well.


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## hearingspecialist (Mar 15, 2010)

GranteedEV those are awesome!!! Wonder what they sound like??? Buy them, the family and I would love to come up to Canada, we'll make it a party, and listen to your new 401K financed babies:gulp:


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## fbov (Aug 28, 2008)

adio said:


> i always wanted to one day own a stereo system with enough bass that having a subwoofer would be optional. everybody thinks 12's, 15's, 18's and now 21's, will forever be in their homes!! i was looking at the zdt 3.5 build on the parts express project page thought that ' hey, why don't i use 8" woofers instead of 7" and maybe have the enclosure tuned to 35 - 38Hz?!?!' is that a great idea???
> 
> also would there be an audible difference use a bigger tweet ( from 3/4 inch to 1 or 1.5 inch)??


To give this a little wider perspective, your only mis-step was replacing the RS180's. A buddy of mine just started a ZDT3.5 build, and I'll tell him this:

Tune the bass any way you want, you still have a proven design. You can have an F3 of 90Hz, or somehwere in the 30's, it's up to you. 

What I'll tell you is that you don't need a sub to cover the audible range. (You do need a sub for the subsonic octaves.) My NatP's are the same drivers, albeit in a 2-way, and I get an in-room F10 in the mid 20Hz range. With no sub, there are enough subsonics to follow you out of the room.
http://www.htguide.com/forum/showpost.php4?p=529492&postcount=26

The key to this is a combination of room gain and "extended bass shelf" (EBS) alignment - big box and low tune, 65L and ~30Hz in my case. Are you aware of enclosure simulators like Unibox and WinISD? 

Yes, there would be an audible difference with a larger tweeter, you could make it a 2-way! There are very real advantages to small domes, and 3-ways are the place to take advantage of them. 

Have fun,
Frank


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## GranteedEV (Aug 8, 2010)

hearingspecialist said:


> GranteedEV those are awesome!!! Wonder what they sound like??? Buy them, the family and I would love to come up to Canada, we'll make it a party, and listen to your new 401K financed babies:gulp:


The salks? They cost around 14k and probably sound amazing. Or were you talking about something else?


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## hearingspecialist (Mar 15, 2010)

Nope those are the ones! Just never heard a set of those, just the Songs. What's $14K??? My wifester (wife to shackster) would not only say no, but "H.. no and those are ugly"!!:foottap:

I can't wait for the audio show down in Newport Beach coming up. I want to audition a bunch of stuff, Salks being one, Atlantic Technology being another and so on. I hope Ascend Acoustics will be there being that close to Newport.


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## oneplustwo (Apr 4, 2011)

I built the ZDT a little while back and concur that you won't need any more for most music. New member here so no linking allowed yet... I'll post once able.


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