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Considering Changing my 15inch to a 12inch For Better Directivity With My CD.

Trdat

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Although there are variations of a typical 15 inch with a compression driver crossed over at around 900hz/1000hz the Econowave DIY build really is mastered with a 12 inch(with no 15 inch as an option) and has some good directivity specs. Why I opted to go with the 15inch I don't know. I am aware that with a 2 inch CD, I can crossover much lower but that would need me to purchase a new waveguide as well as a new CD, hence why I am considering the option of just changing the 15 inch to a 12 inch(fairly afordable and simple enough to CNC a new baffle).

I use digital crossovers with DSP and have 2 decent enough subs and feel that I perhaps have veered to much off the original design parameters of a CD and large PA woofer. My design goals are directivity, well, conformed directivity and I'm hazarding a guess that my 15 inch starts to beam around 600hz and my Dayton PHRN 1014 loses its loading around 1100hz (thanks to Fluid in another thread) so there must be a directivity mismatch.

My questions are

1. What is the right thing to do, get a 2 inch CD or 12 inch woofer.
2. How much difference would the 12 inch woofer make? Is it worth changing the 15 inch to get more power out of the CD down low with less distortion and produce less beaming with the 12 inch crossing it higher?
 

kipman725

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It looks like you use subs so a 10" or 12" would seem to be appropriate. The horn and compresion driver you have at the moment are quite well regarded. If you look at speakers of this format with good directivity the waveguide is larger than the woofer: http://www.gedlee.com/Loudspeakers/NS15.aspx

How about building a turntable and making the polar measurements to see what you are dealing with?
 
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Trdat

Trdat

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It looks like you use subs so a 10" or 12" would seem to be appropriate. The horn and compresion driver you have at the moment are quite well regarded. If you look at speakers of this format with good directivity the waveguide is larger than the woofer: http://www.gedlee.com/Loudspeakers/NS15.aspx

How about building a turntable and making the polar measurements to see what you are dealing with?

Polar measureents will tell us how far off we are to decent directivity, I just got learn how to do them properly and get them done.

When you say build a turntable what do you exactly mean? Something that can precisley lock in the microphone on the correct degrees for measuring? Maybe link me a picture.
 

kipman725

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the easiest way is to turn the speaker not the microphone, or you could mark mic positions using tape and a plumb bob. This turntable can be as simple as two wooden boards with a bolt holding them together. Its worth reading this thread for some methods on at home frequency response measurements: https://www.diyaudio.com/forums/multi-way/353347-measuring-response-close-close-anechoic.html the ~1kHz region you care about I would just get the speaker as high as posible and time gate. It might be worth putting a 35mm pole mount in the base and side of your speaker in order to do this, most 35mm pole mounts like to auto rotate so you wind a load of duct tape around the pole to stop this. I have thought about just rotating speakers on their pole mount but measuring 5 degree increments is tricky!
 

ReaderZ

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Why you decide to corssover at such high frequency for a 15?
 

fluid

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My questions are

1. What is the right thing to do, get a 2 inch CD or 12 inch woofer.
2. How much difference would the 12 inch woofer make? Is it worth changing the 15 inch to get more power out of the CD down low with less distortion and produce less beaming with the 12 inch crossing it higher?

I don't know that there is any huge reason to change. The waveguide is a clone of the one used in the QSC 152HPRi where it is used with a 15" woofer. The waveguide is reasonably consistent in the horizontal being about 90 degrees down around 800Hz which allows it to match directivity with a 15" woofer at 800 to 900Hz.

It could also be used with a 12" woofer as it is still 90 degrees at 1000 to 1300Hz where you would want to cross a 12" driver to match directivity. The 12" would allow the CD to not be pushed quite so low which might be worth considering.

A 2" CD makes no sense as it does not fit with the waveguide and using an adapter can cause trouble if it isn't the right shape to match the CD to the waveguide.

The loss of pattern control is mainly in the vertical due to the smaller dimension so a 12" might be a slightly better match over both planes
 
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Trdat

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Jim Matthews

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Paging Patrick Bateman...

My question would be about SQ, as things are now :
How wouls you assess the intelligibility of vocals from your 15" driver?
 
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Trdat

Trdat

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I don't know that there is any huge reason to change. The waveguide is a clone of the one used in the QSC 152HPRi where it is used with a 15" woofer. The waveguide is reasonably consistent in the horizontal being about 90 degrees down around 800Hz which allows it to match directivity with a 15" woofer at 800 to 900Hz.

It could also be used with a 12" woofer as it is still 90 degrees at 1000 to 1300Hz where you would want to cross a 12" driver to match directivity. The 12" would allow the CD to not be pushed quite so low which might be worth considering.

A 2" CD makes no sense as it does not fit with the waveguide and using an adapter can cause trouble if it isn't the right shape to match the CD to the waveguide.

The loss of pattern control is mainly in the vertical due to the smaller dimension so a 12" might be a slightly better match over both planes

I know the design is used and I fully understand the trade offs but not exactly in tune with the directivity match at the crossover point or lack thereoff. Well, if the horizontal plane is consistent down to around 800hz then the difference with using a 12 inch won't be signifigant it seems.

A 2 inch CD will need a new waveguide and not worth the effort, I can just design a new speaker from scratch. Although, subjectively apparently a 2 inch CD on a PA speaker is a step above a 1 inch CD.

But not pushing the CD down so low might yield some benefit but I have been told for home use that the DE250 is fine so again not a significant difference.

THanks for explaining in laymen terms where the loss of pattern control would be at, in the vertical plain, I knw it simple but sometimes it takes a simple answer to get the whole picture. I should measure but overall if the design is okay and the 12 inch woofer won't make much difference than I think i'll stay with my 15 inch.

And what about the beaming of the 15 inch?

I found some off axis measurements on the deltalite and it seems that the off axis matches on axis till about 700hz or so. I have to take a look again.
 
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Trdat

Trdat

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Paging Patrick Bateman...

My question would be about SQ, as things are now :
How wouls you assess the intelligibility of vocals from your 15" driver?

I've seen the DE250 and Deltalite tested with high regard and minimul distortion, I think the DE250 was measured on Audioexpress. I'm using the Hypex amps with SMSL SU-8 V2 with the MIniDSP UDIO-8 so on paper distortion should be on the down low. To the ear it sounds crystal clear but I have to measure on REW. Regarding intelligibilly of vocals in music its great but i need to watch some television to get a better feel of it.
 

Jim Matthews

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I've seen the DE250 and Deltalite tested with high regard and minimul distortion, I think the DE250 was measured on Audioexpress. I'm using the Hypex amps with SMSL SU-8 V2 with the MIniDSP UDIO-8 so on paper distortion should be on the down low. To the ear it sounds crystal clear but I have to measure on REW. Regarding intelligibilly of vocals in music its great but i need to watch some television to get a better feel of it.

Going against the grain here, there might not be a reason to seek improvement in your implementation of the design.

While a smaller woofer might be crossed higher, you'll likely need more bass support than your current rig.

I would say that if recordings of upright acoustic bass sound realistic, you're getting things pretty close.

There is a strong temptation in our hobby (I've been guilty of it) to fix things until they break.
 
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