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Exodus: A Beast of 100dB :)

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After a long hiatus and anticipating the warmer weather I want to build something with a goal of ultra-high sensitivity (100dB) along the lines of Econowave constant directivity. Some design goals are:

 

1) Small form factor.

I was looking at 8" Klipsch R28 floorstanders at harvey norman and thought the size is great.

 

2) Constant directivity. At about 24cm baffle width I can expect 2khz - 2.5khz

 

3) High SPL and sensitivity . I want 100dB, but even 94-96dB should be great.

 

 

S18.png

 

Waveguide: Faital Pro STH100

Great price, good looks, cast alumunium, and directivity to die for'.

 

In the past I had been skeptical about small waveguides, but upon hearing the Redefy TWO I was an instant convert. 2khz directivity I think should be great.

 

faital_sth100.jpg STH100_hor-beamwidth.jpg

 

Compression Driver: B&C DE250

"Geddes approved" .. enough said :D

 

269338.jpg

 

Woofers: PRV Audio 8MR500-PhP-4

Smooth response from what I can see, 100dB sensitivity too (4ohms)

 

84-prvaudio-8mr500-php-4-1_1%252520small

 

I am however still thinking whether to sacrifice sensitivity with this B&C 8PS21 which has very venerable status in terms of distortion. ie "The scanspeak of pro audio!"

 

88-bc-8ps21-1small.png

 

 

Subwoofers: Eminence Beta 12A

Two of them in parallel should provide 102dB :)

 

BETA12A-large-small.png

 

I want to start naming my speakers with current events, and 'Exodus' seems like an appropriate reminder of the sad plight of people from troubled areas in the world.

 

 

 

 

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Hi again!  :)

 

In the past I had been skeptical about small waveguides, but upon hearing the Redefy TWO I was an instant convert. 2khz directivity I think should be great.

 

The most work I have done has been to this issue.     Take the controlled directivity as low as you can IMO.

 

Although of course, once we set the width of the speaker/horn .... then there isn't much more we can do.   The speaker I build the most of, uses an even slightly smaller horn (135mm wide), for a crossover point @ 1.7khz (as aggressively low as it can be pushed)..... sure, small waveguides can be improved on by bigger waveguides, but for the comparison between a speaker with one, and without one .... there is no contest   :)

 

 

I want to try this horn too.    It could almost be too narrow though?!

 

 

Without a passive crossover to worry about, I wouldn't get too caught up in sensitivity, as long as you're using drivers in their linear range.   Frequency response (directivity) is what you hear.

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When I heard Redefy TWO, definitely the horn is great and there was nothing offensive about it. They just 'sing'.

 

However as you said I have not done a longer listening. The other issue is with narrower baffle, the baffle step frequency moved up. With my 12" econowave it's 500hz but 24cm baffle I can expect 900ish hertz.

 

maybe I just listen to the horn for longer period before cutting the wood...

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Yep.     If you want to make a 24cm wide speaker .... then you already have made good choices in post 1.    Wider can be better for baffle step and allow bigger horn ....  If wider is an option, consider it.

 

... but sometimes the first thing which is decided is the 'look'.     The reason I have spent so much time working on little waveguides is because everyone who wants to buy a speaker, thinks shoebox sized is already 'too big'.

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I like these horns and use them with DE250 also in some speakers that @@Paul Spencer made for me. smile.png

 

I think the 8in B&C even got discussed between Paul and myself when we were looking at the options for my speakers. I kind of wanted it, but I don't regret the choices Paul made at all.

 

See - http://www.stereo.net.au/forums/index.php?/topic/53609-introducing-cinem8/page-1

Edited by hochopeper

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I'd go straight for the b&c. The prv driver below 2khz is 98db at best and thats 2.83v at 4 ohm. Only really touches 100db in a peak and then rises above 100db above 2khz.

What do the 12s model like in an enclosure that size? Will they need a bit of low end boost? Would a pair of 10s give a bit more in that kind of airspace? The beta 10cx woofer with the hole plugged only needs a smallish box and the two together will still be plenty loud!

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Yep.     If you want to make a 24cm wide speaker .... then you already have made good choices in post 1.    Wider can be better for baffle step and allow bigger horn ....  If wider is an option, consider it.

 

... but sometimes the first thing which is decided is the 'look'.     The reason I have spent so much time working on little waveguides is because everyone who wants to buy a speaker, thinks shoebox sized is already 'too big'.

 

I already have my 12" econowaves which is 37cm wide. So wider option might not be desired.

 

I have been toying with the idea of 10" woofers though with B&C 10PS. With this the speakers will be 28cm.

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I'd go straight for the b&c. The prv driver below 2khz is 98db at best and thats 2.83v at 4 ohm. Only really touches 100db in a peak and then rises above 100db above 2khz.

What do the 12s model like in an enclosure that size? Will they need a bit of low end boost? Would a pair of 10s give a bit more in that kind of airspace? The beta 10cx woofer with the hole plugged only needs a smallish box and the two together will still be plenty loud!

 

Thanks I'm starting to want the B&C :). I think 94 dB should be 'sufficient'.

 

The 12" subs will be in sealed enclosure. Having DSP, it will be a matter of EQ to achieve flat down to 30hz.

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Novice question....

 

Why would you put the 12 inch drivers on the same side ?

 

I want to avoid bi-pole radiation pattern which will cause nulls and peak. 

 

Also, having them on one side allows playing around with placement for best room modes :)

 

 

radpat1.gif

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I'd go straight for the b&c. The prv driver below 2khz is 98db at best and thats 2.83v at 4 ohm. Only really touches 100db in a peak and then rises above 100db above 2khz.

 

Sensitivity isn't necessarily a good benchmark ... but I agree in the B&C.    They have a much more powerful motor and more linear movement, than the PRV driver mentioned (which has only xmax=1mm)

 

 

So wider option might not be desired.

 

Yeah, sure.... that's what I was getting at.   Just because a 12" wide horn will be better, doesn't mean that fits the 'design brief'.   :)

 

 

What about this B&C 8PE21

 

This driver has a very powerful motor.    Will it go low enough?    xmax = only 3.5mm .....   I'm assuming you need it to run down to a crossover point of 200Hz or lower?

 

If it passes your sims, go for it  (except it's ugly IMO).

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acg   

is because everyone who wants to buy a speaker, thinks shoebox sized is already 'too big'.

 

Not me..haha!

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Well, after putting stuff in PE cart, I realise now how the low AU$ is impacting this hobby :(.

 

I might just wait a while for better rate, if ever...

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acg   

Well, after putting stuff in PE cart, I realise now how the low AU$ is impacting this hobby :(.

 

I might just wait a while for better rate, if ever...

 

The AUD has gone up a cent or two in the past week or so, but I think that in general it is on its way lower...at least I hope it is still falling...60 cents would be nice for my business...but I ain't no economist.  I am just glad I made the bulk of my overseas purchases when the AUD was significantly higher.

 

Now might be the best time for some time.  When it is low it takes years to come back, and I would be very surprised if the dollar leapt say 10c before the end of this year or perhaps even the next, but I would not be particularly surprised if it fell another 10c by the end of this year (famous last words!).

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Newman   

I want to avoid bi-pole radiation pattern which will cause nulls and peak. 

 

Also, having them on one side allows playing around with placement for best room modes :)

 

 

radpat1.gif

 

Your diagram correctly shows no difference between bipole and monopole in the frequencies of your 12" driver.

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I bought heaps of stuff when it was $1.1 to the green paper. That was great  :cool:

 

Me too.   I could start up a scanspeak disty .... well not quite, but I have enough for quite a few more builds.

 

 

Your diagram correctly shows no difference between bipole and monopole in the frequencies of your 12" driver.

 

Yes.   It depend on how high he intends to run the woofers.

 

This is where the comments to do with the different midwoofers  (and their xmax)  was coming from.     The lower knee of the midwoofer  (assumed to be somewhere between 80 and 300Hz)  is going to be a critical element of the design.

 

Too high, and the side woofers might be a problem

Too low, and the driver might be hurting to reach up the ~2khz crossover point

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I haven't done any simulations yet. But perhaps it would be around 200-300hz.

 

In any case having them on one side allows more versatile placement. E.g. if they are near my TV cabinet.

 

I might just build one with what I have (w22, L21).... it's too expensive at the moment.

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baMarek   

I don't know how you ran them, but those Beta 12s are sounding (and measures) great on my speakers :D

 

Eminence Beta is one of the few 12" which does not have harsh breakup and went to over 4-5 khz. That's impressive for a 12" driver and even arguably better than B&C!!  :cool:

 

My own raw measurement of Beta 12A:

 

Eminence%252520Beta%25252012A%252520Raw.

 

 

 

Actually now I am looking at Eminence beta 8a. The response is very..very  good and at half the price of B&C. 95dB.

 

290-404_ALT_1small.png

 

 

 

beta8A-f-size475.gif

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These Eminence drivers do get a rep for sounding "bad". 

 

I suspect this could be to do with being used outside their linear range, which is easy to do (low xmax) .....  coupled with a low cms and bl.

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baMarek   

They may measure fine and you can get flat response but measurements are only half of the story. The sound of pretty much all Eminence I tried, with small exception of Delta used in a box, was very disappointing. No timbre, no emotions. Thomann have some nice RTF speakers that should do the job much better and don't break the bank.

Sent from my GT-I9192 using Tapatalk

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Interesting. That actually convince me more as 'boring' and 'no fuss' sound is what I am looking for in a speaker. They should convey neutrality and not 'injecting' a certain character.

 

The excitements should come when fed in correct material and played at realistic level :D

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acg   

Interesting. That actually convince me more as 'boring' and 'no fuss' sound is what I am looking for in a speaker. They should convey neutrality and not 'injecting' a certain character.

 

The excitements should come when fed in correct material and played at realistic level :D

 

I find this the most interesting question in audio...what is neutral?  BaMarek did not mention injection of character by the driver he suggested...he mentioned a lack of character timbre the Eminence drivers.  Which one is neutral if you can pick a colour from neither??

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