Flex Your PCD Mettle:

[Greg01]

Re: Flex Your PCD Mettle:

Pete

I would like to build this project. I would like to clarify a point or two. The cabinets that Zilch used appear to have the baffle inset about .75 inches or so. If I have read what you posted earlier correctly, because of the waveguide and the size of the woofer, this would not have too much of an effect on the frequency response. Is this correct?

Also... After compensating for the baffle step response it appears that this system will only have ~ 90 db efficiency. Is this correct as well?

I know watts are cheap and I don't mind putting some power to this project. I just wanted to clarify these things before I committed to a project.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Pete

I would like to build this project. I would like to clarify a point or two. The cabinets that Zilch used appear to have the baffle inset about .75 inches or so. If I have read what you posted earlier correctly, because of the waveguide and the size of the woofer, this would not have too much of an effect on the frequency response. Is this correct?

Also... After compensating for the baffle step response it appears that this system will only have ~ 90 db efficiency. Is this correct as well?

I know watts are cheap and I don't mind putting some power to this project. I just wanted to clarify these things before I committed to a project.

Some diffraction control on those edges wouldn't be a bad thing. The waveguide helps mitigate the issue since the signal is directed in a well formed forward lobe. If you will notice in some of the pics, Zilch has applied some sound absorbing/diffusing material to those edges.

Yes, the mid band sensitivity is 90dB. ~4dB Baffle step has been included.

[NWCgrad]

Re: Flex Your PCD Mettle:

Pete

I would like to build this project. I would like to clarify a point or two. The cabinets that Zilch used appear to have the baffle inset about .75 inches or so. If I have read what you posted earlier correctly, because of the waveguide and the size of the woofer, this would not have too much of an effect on the frequency response. Is this correct?

Zilch linked photos on a the big econowave thread over at AK Design Collaborative (see http://www.audiokarma.org/forums/sho...50939&page=644, post #9658) where the PE cabinet was modified to remove the baffle inset. The cabinet has only one coat of Watco Danish oil.

This is how I plan to proceed so I won't worry about the effect on the frequency response. Note this an earlier iteration that was not built by Zilch (it is from jackgiff) and the woofer is not mounted on the rear of the baffle as with the current Zilch design.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Zilch linked photos on a the big econowave thread over at AK Design Collaborative (see http://www.audiokarma.org/forums/sho...50939&page=644, post #9658) where the PE cabinet was modified to remove the baffle inset. The cabinet has only one coat of Watco Danish oil.

This is how I plan to proceed so I won't worry about the effect on the frequency response. Note this an earlier iteration that was not built by Zilch (it is from jackgiff) and the woofer is not mounted on the rear of the baffle as with the current Zilch design.

Rear baffle mount for the woofer is important. It pushes the acoustic centers closer together. A rear mount on a thick baffle would be even better.

[Zilch]

Re: Flex Your PCD Mettle:

AK EconoWave DIYers have been working for several months with the PE KD Trapezoid cab using different drivers and waveguides. In response to an express desire for an off-the-shelf "premium" kit using select components that anyone could build, I assembled this combination and presented it here as a crossover optimization exercise. Pete dove in and came up with an excellent design, which I am finalizing per his recommendation for high SPL installations tonight.

I left the front baffle recessed in the "stock" location to assess the impact of the edge overhangs. Installing pipe insulation on them made a measurable difference, but it remains arguable whether those measurements represent anything more significant than the signature of the the foam in lieu of the overhangs themselves. The data is posted in the AK thread. If nothing else, it indicates that there is enough illumination present to alter the response, albeit minimally:

http://www.audiokarma.org/forums/showthread.php?p=3266252#post3266252

There's certainly room for experimentation with moving the baffle forward, expanding the volume of the stock cabs from 1.65 cuft to 2.00 cuft with it flush front, or some intermediate position retaining a smaller recess for mounting a grille....

[[email protected]]

Re: Flex Your PCD Mettle:

it seems that there is no need to model with such high watts. will greatly effect the excursion and vent air speed. am i wrong here?

[NWCgrad]

Re: Flex Your PCD Mettle:

Rear baffle mount for the woofer is important. It pushes the acoustic centers closer together. A rear mount on a thick baffle would be even better.

Pete, I am planning on a 1.5" thick baffle. I was going to rear mount at 3/4", but are you indicating I would be better off mounting on the back at 1.5"? Does this require any other modifications?

I plan to brace the internal cabinet to bring the volume back down from 2.0 cu ft to approx 1.65". Using a 4" port (7.17" long) the box will be tuned (theoretically) at 45 Hz. If I miss my target volume, the tuning could range from 49.7 (1.35 cu ft enclosure) to 40.9 (2.0 cu ft enclosure). I modeled a range of tuning frequencies in beteen and should be fine if I am off in enclosure volume.

Pete dove in and came up with an excellent design, which I am finalizing per his recommendation for high SPL installations tonight.

I left the front baffle recessed in the "stock" location to assess the impact of the edge overhangs. Installing pipe insulation on them made a measurable difference, but it remains arguable whether those measurements represent anything more significant than the signature of the the foam in lieu of the overhangs themselves. There's certainly room for experimentation with moving the baffle forward, expanding the volume of the stock cabs from 1.65 cuft to 2.00 cuft with it flush front, or some intermediate position retaining a smaller recess for mounting a grille....

Zilch, Thanks for all the efforts you (and others at AK) have put into this project. It just gets better and better. I am looking forward to getting back home (Navy has me on a multi-month temporary assignment 7 hours away from home) so I can start building. Look forward to watching the development of the project.

Pete, Thanks again for all your advice!!!!!

[Zilch]

Re: Flex Your PCD Mettle:

I wouldn't recess the woofer any more than the prototype without measuring where that steered the forward axis. Last night it was at 2.0° above the midpoint between the drivers, which calculates to on waveguide axis at 12.5' listening distance.

Flush-mounting the waveguide, which I intend to do to round over the woofer opening, will push that a bit higher, based upon prior experience with moving the acoustic centers. PCD shows what happens, but it should always be verified with measurements....

[NWCgrad]

Re: Flex Your PCD Mettle:

I wouldn't recess the woofer any more than the prototype without measuring where that steered the forward axis. Last night it was at 2.0° above the midpoint between the drivers, which calculates to on waveguide axis at 12.5' listening distance.

Thanks, my listening distance is 13' from my speakers - so the current 3/4" recess should be spot on.

[Zilch]

Re: Flex Your PCD Mettle:

it seems that there is no need to model with such high watts. will greatly effect the excursion and vent air speed. am i wrong here?

Yes, correct.

[Unless you're building rock band road gear.... ;) ]

[Greg01]

Re: Flex Your PCD Mettle:

Pete

Thanks for answering my ramble from last night which is recreated in its entirety below. However, I never got around to asking you the question I really intended to ask.

I know that Zilch's cabinet has the inset baffle. I was going to build my own cabinet of approximately 60 liters tuned to 40 hertz (with a slot port). My cabinet may or may not have an inset baffle depending on how you answer the following question. I would normally flush mount the woofer. In this cash I would rear-mount the woofer .75 inches from the front of the baffle to maitain the distance pursuant to your model.

I usually do not inset a baffle. I would just have a flat baffle with a .5 inch roundover (this is the largest roundover bit I am comfortable using in my quarter inch collet router). Do you think this would make a material difference in the frequency response? Sorry for not getting to my point in my last post.

Pete

I would like to build this project. I would like to clarify a point or two. The cabinets that Zilch used appear to have the baffle inset about .75 inches or so. If I have read what you posted earlier correctly, because of the waveguide and the size of the woofer, this would not have too much of an effect on the frequency response. Is this correct?

Also... After compensating for the baffle step response it appears that this system will only have ~ 90 db efficiency. Is this correct as well?

I know watts are cheap and I don't mind putting some power to this project. I just wanted to clarify these things before I committed to a project.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

I think doing what you're planning is great. It keeps the offsets as measured by Zilch, so everything should come out the same. As for diffraction on the woofer output? Any diffraction signature will be small due to the large size of the driver area. The roundover won't change the response much, but it sure will look a lot nicer.

Having a flush mount waveguide on a flat front baffle is how I would do it too. Zilch is using those knockdown cabinets from PE.

Pete

Thanks for answering my ramble from last night which is recreated in its entirety below. However, I never got around to asking you the question I really intended to ask.

I know that Zilch's cabinet has the inset baffle. I was going to build my own cabinet of approximately 60 liters tuned to 40 hertz (with a slot port). My cabinet may or may not have an inset baffle depending on how you answer the following question. I would normally flush mount the woofer. In this cash I would rear-mount the woofer .75 inches from the front of the baffle to maitain the distance pursuant to your model.

I usually do not inset a baffle. I would just have a flat baffle with a .5 inch roundover (this is the largest roundover bit I am comfortable using in my quarter inch collet router). Do you think this would make a material difference in the frequency response? Sorry for not getting to my point in my last post.

[Zilch]

Re: Flex Your PCD Mettle:

EconoWave Deluxe crossover and parts list updated for compression driver protection at high SPL. Increase R1 power rating as required; use 9.1 in parallel with 10 Ohms for 20W (shown, optional) or 4 x 4.7 Ohms in series/parallel for 40W. I left standard at a single 10W, as I detect no appreciable temperature rise under moderately high (90 dB @ 2m) listening conditions:

http://techtalk.parts-express.com/showpost.php?p=1626379&postcount=72

Also added final vertical polar map; we're good (-6 dB) +/- 15°.

Forward axis is midpoint between drivers +2.0° and XO at 1.565 kHz.

All measurements w/L-pad @ 1:00....

[Zilch]

Flex It, Round 2.1 - EconoWave Deluxe HO for Efficiency HOunds:

As previously, measurements on axis midway between woofer and waveguide, 10.5" c/c distance, 44" mic distance, HF w/L-pad @ 1:00:

Performance on the Schumacher V1.1 XO, "Deluxe":

Comparison to 3012LF, HO HF at "Max":

I'm not seeing 5 dB to grab there; 3 dB perhaps....

The files:

[donprice]

Re: Flex Your PCD Mettle:

Zilch - Can you double check the files you posted? The FRD files are fine. I'm guessing the files with no extension are ZMA files. Where are the project (CSP) files?

Thanks!