Critique my 8" Pro Audio Woofer 8" Waveguide / Compression Driver Plans

[gibbed]

I am wondering how well these components would work together, and what style crossover would be best. I am currently running a pair of 38 Hz Volvotreter tapped horns, "Microbe" 5 inch bookshelves, and a Dayton amp (subs) and Panasonic XR57 class D amp (microbes). These will be the first speakers I have designed myself - I have built the Microbes and volvotreter tapped horns from plans. I like the microbes sound quality wise, but I am looking for more clean output to match the tapped horns.

B&C 8PS21 8" Woofer (as reviewed by Zaphaudio)
Parts-Express.com:*B&C 8PS21 8" Woofer | 8ps21 8" pa midrange cone midrange b&c midrange pa woofer

Eminence PSD:2002S-8 1" Titanium Driver 8 Ohm
Parts-Express.com:*Eminence PSD:2002S-8 1" Titanium Driver 8 Ohm 1-3/8"-18 | compression driver tweeter horn driver screw on high frequency 1" exit i" throat HF PA driver tweeter driver

Dayton H08RW 8" Round Waveguide
Parts-Express.com:*Dayton H08RW 8" Round Waveguide 1" Threaded | horn lens horn tweeter horn bell horn compression driver DaytonAudioWaveguides070109

The box would be about 20L with a port, tuned to 89 Hz and crossed at 100 Hz to the subs from the receiver. I would use the biamp feature of the XR57 to balance the output to the woofer and compression driver circuits, and adjust the time delay between the two. I would have separate low and high pass circuits for the woofer and compression driver.

Questions:
1. Is this a workable setup?
2. What order crossover would be best?
3. What frequency crossover would be best?
4. Will additional padding be needed to ensure somewhat smooth upper frequency response from the compression driver / waveguide?

[Inductor]

Use this 2-way xover, sensitivity/impedance@xoverpoint is similar, here :
Kit DIY enceintes B&C Speakers Box 8
Kit DIY enceintes B&C Speakers Box 8

[tinitus]

8PS21 may be ok, but it looks somewhat peaked, maybe its that nasty inverted dustcap
And you will end with a 90db design, considering BSC

And a cheap Eminence CD on a random waveguide may not work too good either

But i say that without knowing any of those drivers

Fore a nice cheap 8", maybe look at Eminence BETA-8A, and at about the price of B&C you can get two Beta8
Maybe two will really rock
But xo fore compression drivers may not be that easy to handle
As fore the waveguide, there hav been a few suggestions
One was from this company http://www.qscaudio.com/products/acc...ccessories.htm under replacement parts

[col]

Maybe the Eminence Beta 8A with the B&C DE10 crossed at 2.5khz with the Dayton 8" ? Iv'e used the Beta 8a in a ported 20-30ltr box before it sounds very good. I crossed it at 2khz into a BMS4540 (MINIRIG » minirig V6). I had issues with the mid-high porting and the phasing with the ported sub though. Now I am running sealed mid-highs using Eminence Beta 10 and a B&C DE10, using the Dayton 10". Much better, easier to blend with the subs.

http://minirig.org.au/2008/11/13/min...ession-driver/

col.

[gibbed]

I will also consider the Eminence Beta 8A and B&C DE10. What makes them a better combination than the B&C and Emenence (other than price?).

Will a 12 db/octave crossover around 2500 Hz be a good starting point? Remember, I can adjust phasing to each speaker individually with my Panasonic class D amp.

[Inductor]

Originally Posted by tinitus

And a cheap Eminence CD on a random waveguide may not work too good either

Hi Tinitus,
Can you say what "cheap" has to do with "technique" (Do you mean is bad?!).

(Having said that) As a good resource for working with the Eminence PSD2002 go look at the work of W.Parham at PiSpeakers (you can buy his xovers too):
Pi Speakers - unmatched quality and state-of-the-art performance

[gibbed]

Originally Posted by Inductor

Hi Tinitus,
(Having said that) As a good resource for working with the Eminence PSD2002 go look at the work of W.Parham at PiSpeakers (you can buy his xovers too):
Pi Speakers - unmatched quality and state-of-the-art performance

Thanks for the link - I'm giving his crossover write-up a couple read throughs. Hopefully it will click after a while.

[Patrick Bateman]

Originally Posted by tinitus

8PS21 may be ok, but it looks somewhat peaked, maybe its that nasty inverted dustcap

I have the neodymium version of that woofer, and I've done a ton of measurements. It's an exceptional eight, possibly the best I've ever used. IMHO, the response isn't peaking because of the dustcap. The response is peaking because the woofer is beaming. Beaming will occur at a frequency which is equivalent to the piston diameter. For the 8PS21, that's about 2khz.

In an average speaker the inductance in the motor begins rolling off the response of the woofer. But the 8PS21 (and the 8NDL51) has a copper cap to extend the high frequency response.

Combine these two things, and you end up with a rising response above 1khz. This is actually a good thing - it demonstrates that the speakers performance is nearly perfect.

Here's a comparison of the distortion performance of the neo and ferrite versions of the B&C. One was measured by John Krutke and the other by AUgerpro

This is my own personal measurement of the 8NDL51. I didn't calibrate the SPL level (I don't have an SPL meter.) My measurements shows higher distortion than the others because it's done with 10 watts at 10 feet. Look how smooth the response is! Just crazy flat. This graph has 3rd octave smoothing. One of the reasons it's so flat is that it's measured from ten feet away, but increasing the distance makes it easier to get low frequency resolution. I'm not sure why 3rd harmonic looks higher on my measurements. The rolloff at 5khz is due to the sampling rate.

Originally Posted by tinitus

And you will end with a 90db design, considering BSC

And a cheap Eminence CD on a random waveguide may not work too good either

But i say that without knowing any of those drivers

Fore a nice cheap 8", maybe look at Eminence BETA-8A, and at about the price of B&C you can get two Beta8
Maybe two will really rock
But xo fore compression drivers may not be that easy to handle
As fore the waveguide, there hav been a few suggestions
One was from this company QSC Audio - Loudspeaker Accessories under replacement parts

IMHO, the B&C eights are superior to the Eminence. The eminence is a good buy, but the B&C's price is justified by it's excellent performance.

I would consider BMS, B&C or Celestion for the top end instead of Eminence.

[Patrick Bateman]

Originally Posted by Patrick Bateman

I have the neodymium version of that woofer, and I've done a ton of measurements. It's an exceptional eight, possibly the best I've ever used. IMHO, the response isn't peaking because of the dustcap. The response is peaking because the woofer is beaming. Beaming will occur at a frequency which is equivalent to the piston diameter. For the 8PS21, that's about 2khz.

In an average speaker the inductance in the motor begins rolling off the response of the woofer. But the 8PS21 (and the 8NDL51) has a copper cap to extend the high frequency response.

Combine these two things, and you end up with a rising response above 1khz. This is actually a good thing - it demonstrates that the speakers performance is nearly perfect. The extended response also makes it easier to integrate the B&C with a waveguide.

Here's a comparison of the distortion performance of the neo and ferrite versions of the B&C. One was measured by John Krutke and the other by AUgerpro

This is my own personal measurement of the 8NDL51. I didn't calibrate the SPL level (I don't have an SPL meter.) My measurements shows higher distortion than the others because it's done with 10 watts at 10 feet. Look how smooth the response is! Just crazy flat. This graph has 3rd octave smoothing. One of the reasons it's so flat is that it's measured from ten feet away, but increasing the distance makes it easier to get low frequency resolution. I'm not sure why 3rd harmonic looks higher on my measurements. The rolloff at 5khz is due to the sampling rate.



IMHO, the B&C eights are superior to the Eminence. The eminence is a good buy, but the B&C's price is justified by it's excellent performance.

I would consider BMS, B&C or Celestion for the top end instead of Eminence.

[tinitus]

Originally Posted by Inductor

Hi Tinitus,
Can you say what "cheap" has to do with "technique" (Do you mean is bad?!).

It is based on Waynes(pispeakers) and a few others experiences from an older debate on these CDs
B&C CD was concluded to be a significant upgrade over Eminence
The word "cheap" maybe should not have been used that way, wasnt meant to be

B&C woofer looks way better than the cheap Beta8, sure
I have no problem with a cheap driver, if it sounds good
Cheap compression drivers, may be different matter tho
I suppose 100USD is already cheap as is

Well, response on B&C woofers looks like obvious breakup to me, maybe its not
And I really didnt know "beaming" looked like that
It usually doesnt bother me much
Reason I mention Beta8 is that its known to be good even used "fullrange"
I expect xo point to end up relatively high as is
I have never heard much about the B&C and I have nothing against it
It just didnt look like a woofer I would use high up, or suggest to a "newbie", due to special topend
Sensitivity is avrage, but I guess ok fore 8"
Thats about all there is to it
But if its better than factory suggest, then fine
Its not that I try to argue either

If you dont know about BSC, its a loss in low midrange
If you do not compensate the result will be thin and edgy sound
If you compensate with 3db you will have a 90db speaker
With double woofers in a 2.5way you may get 95db, or more
and more midbass pressure as well
Also note that many high sensitive smaller pro drivers may have even further relative loss of midbass SPL