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Old 3rd May 2013, 08:43 PM   #1
diyAudio Member
 
Join Date: Nov 2011
Location: Minnesota, Land of 10,000 lakes
Default New proposed system feedback

Greetings,
I’m helping my nephew out with a system for his garage (system listed below). The purpose of this system is for decent full range sound not audiophile precision staging, imaging etc. The garage is approximately 23’ x 40. The goal is to concentrate on sound in half the space not the entire garage.
In order to stay within the budget by avoiding a third amp, the plan is to incorporation a Piezo tweeter with the Beta 8 coaxial. According to what I’ve been able to find on the Piezo’s, they don’t require dedicated crossing if some combination of resistors are added to the tweeter. I’d like to use PVC pipe for the mid/tweet combo and will follow the manufactures suggested (sealed) enclosure size.
Regarding speaker placement, the sub will be located in a corner to take advantage of boundary gain. The Mid/tweet can be placed where ever they sound the best.
Hoping for some feedback on the following.

A) Overall, does the approach make sense?
B) If the Piezo works, as contemplated, should this driver be upgraded?
C) Any Piezo attenuation recommendations?
D) Will the CDA 254L amp provide adequate power for the folded horn sub?
E) Other thoughts, suggestions?
Thanks in advance for any input that you’d care to share.
Kindest,
Marko

GARAGE SYSTEM
Docking station – Pure I-20
http://www.soundandvisionmag.com/article/review-pure-i-20-and-pro-ject-dock-box-s-digital?page=0,2
Folded horn sub-woofer – Tuba 60 (single driver slim version)
http://www.billfitzmaurice.com/T60.html
Sub-woofer driver – Lab 12
http://www.parts-express.com/pe/showdetl.cfm?partnumber=290-570
Midrange drivers – Eminance;Beta-8CX Coaxial
http://www.parts-express.com/pe/showdetl.cfm?partnumber=290-500
Tweeters - GRS PZ 1188
http://www.parts-express.com/pe/showdetl.cfm?partnumber=292-450
Sub amp - Class D Audio; CDA-254L
http://classdaudio.com/amplifier-kits/cda-254l-kit.html
Mid/tweet amp- Class D Audio; CDA-254
http://classdaudio.com/amplifier-modules/cda-254-audio-amplifier-125w-x-2-8-ohm-250w-x-2-4-ohm.html
Crossover- Behringer Ultradrive; DCX 2496
http://www.parts-express.com/pe/showdetl.cfm?partnumber=248-669
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Old 7th May 2013, 02:19 PM   #2
Zero D is offline Zero D  United Kingdom
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Join Date: Aug 2009
Hi, first off, the Beta 8 coaxial is NOT a coaxial ! It's Very misleading. It "appears" that it can be converted into one though.

Quote:
Eminence Beta-8CX 8" Coaxial Driver - HF device sold separately

BETA 8CX, 10CX, 12CX and ACOUSTINATOR™ CX 2008 are coaxial speakers with tweeter sold separately. Published Usable Frequency response contingent upon use of APT 50 HF Driver.
Speaker Detail | Eminence Speaker
But i expect you realise that, which is why you want to use a Piezo with it.

GRS PZ1188 Piezo Horn Driver - Standard 1-3/8" 18-TPI threads facilitate use with 1" horns.

You would require a Horn to couple it to, of which there are a Great many to choose from ! Alternatively you could use one of these combined units.
Quote:
GRS PZ1025 2" x 6" Piezo Horn Mid/Tweeter Similar to KSN1025 GRS PZ1025 2" x 6" Piezo Horn Mid/Tweeter Similar to KSN102 292-444
I've used KSN1025's in the past on a 100W Amp with no problems. & IF used with a passive HP Xover are fine. Nothing complicated is needed, just a parallel 10W power resistor & series capacitor. I can calculate it for you if you like. No attenuation required on this model with that driver. Plus you will need a LP passive Xover for the Beta 8 to match it. Again a simple Xover would be fine, just an Inductor, which i can calculate for you.

The CDA-254L = 125 watts/channel at 8 ohms and 250 watts/channel at 4 ohms, or 500W bridged Mono @ 8 ohms.

The LAB 12 = 6 ohms & 400 Watts so somewhere inbetween.

Are you planning on 1 Tuba 60 or 2 ? If only one then bridging makes sense.
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Old 7th May 2013, 03:44 PM   #3
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Join Date: Nov 2011
Location: Minnesota, Land of 10,000 lakes
Hello Zero D, thank you for responding and offering some help.
I'm reconsidering the following. Using the Beta 8 with the APT-50 and adding in the smallest Class D amp dedicated to the tweeters. If I have this right...I could then get 2-mini 2x4 DSP's and actively cross sub,mids and tweets independently (2496 no longer needed).
I believe this would allow the most flexibility.

Currently planning on only one sub, bridged mode makes sense with the 254L.

I now need to check back in with The amp manuf. on power supplie(s).

Does this new direction make sense to you? Have you worked with a folded horn before? I ask about the sub because it sounds like I will need to add some delay to the mid/tweets. Do you know if the DSP'S add-in's will offer enough delay?
Kindest,
Marko
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Old 7th May 2013, 06:10 PM   #4
Zero D is offline Zero D  United Kingdom
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Quote:
Hello Zero D, thank you for responding and offering some help.
Pleasure

Quote:
I believe this would allow the most flexibility.
Indeed

I downloaded the Beta_8CX.pdf & can NOT see Any mention of using it with the HF driver ? How strange ! I would have thought they would have shown this.

On here it actually gives much more info, & about other HF options too Eminence Beta 8CX coaxial speaker. The Eminence Beta 8CX is a 8" 8 ohm coaxial speaker. An APT-3 adaptor must be used with the APT-50

Quote:
Currently planning on only one sub, bridged mode makes sense with the 254L.
OK & yes.
Quote:
Does this new direction make sense to you?
Yes

Quote:
Have you worked with a folded horn before?
Yes

Quote:
I ask about the sub because it sounds like I will need to add some delay to the mid/tweets.
Good thinking

Quote:
Do you know if the DSP'S add-in's will offer enough delay?
I'm not sure how much delay they offer, as i havn't used the DSP, but you can easily find out from available data, i expect. Plus until you actually biuld & test the sub, you won't know for SURE how much delay you'll need. Check some of the folded horn designs on here, & elsewhere for more info. Plus you could ask Bill Fitzmaurice if he knows what the actual delay is, or should be.
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Old 9th May 2013, 03:24 AM   #5
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Join Date: Nov 2011
Location: Minnesota, Land of 10,000 lakes
Hi Zero D,
Still working on this system in my spare time.
I've been having a little trouble getting back onto Bill Fitzmaurie's site to ask about delays. Never received a registration confirmation and his site only lets me back on as a guest with no options. Can't even order a set of plans...I'll just keep trying.
After digging a little deeper with mid range drivers it looks like it may make more sense to go with the Beta 10 coaxial vs. the 8". The Lab 10 Pro specs indicate an upper limit of 125 hz which may be low for the 8" crossing range. The 10" seems like it may be a better fit?
I'm sure this info is rather elementary to you, however, while I've spent many years enjoying music on decent systems, getting into the DIY stuff is all rather new and very enjoyable.
Kindest,
Marko
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Old 9th May 2013, 08:59 AM   #6
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Quote:
Originally Posted by mnsouthpaw View Post
Hello Zero D, thank you for responding and offering some help.
I'm reconsidering the following. Using the Beta 8 with the APT-50 and adding in the smallest Class D amp dedicated to the tweeters. If I have this right...I could then get 2-mini 2x4 DSP's and actively cross sub,mids and tweets independently (2496 no longer needed).
I believe this would allow the most flexibility.

Currently planning on only one sub, bridged mode makes sense with the 254L.

I now need to check back in with The amp manuf. on power supplie(s).

Does this new direction make sense to you? Have you worked with a folded horn before? I ask about the sub because it sounds like I will need to add some delay to the mid/tweets. Do you know if the DSP'S add-in's will offer enough delay?
Kindest,
Marko
Hi Marko.

Just want to mention that if you decide on the miniDSP's, it might be better to just get 1. Analog filters may be a bit more difficult to get right, but I personally think they sound much better than digital when 100%.

Just saying this because I bought 2 miniDSP's myself, and went back to analog, sold one of the miniDSP's and kept one for future xo experiments, good thing about digital filters are that they are great for finding out which analog filter design you should use!

The delay feature may not give the same sound quality as a well designed and thought out analog setup.

But this is just my opinion.

Last edited by KaffiMann; 9th May 2013 at 09:04 AM.
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Old 9th May 2013, 12:53 PM   #7
Zero D is offline Zero D  United Kingdom
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Quote:
Still working on this system in my spare time.
That's good to hear

I would try & email Bill Fitzmaurie directly & explain the situation, & ask for the delay info you seek.

Re eminence Beta 10 coaxial.

It should be fine with the subs. I'll sim it for you & post back with a screenie. It might not be today though.

Quote:
I'm sure this info is rather elementary to you,
We all have to start somewhere, & i only know what i know We never stop learning = All good

Quote:
getting into the DIY stuff is all rather new and very enjoyable
.

Yes it's almost better than *** sometimes it is

KaffiMann makes a good point.
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Old 10th May 2013, 03:44 AM   #8
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Join Date: Nov 2011
Location: Minnesota, Land of 10,000 lakes
KaffiMann, thanks for chiming in!

Your comments about passive vs active x-overs are consistent with what I've heard and read from others. For this application I'd prefer to stay with an active approach. If we are disappointed with the results we should have a good basis of info to convert to passive...as you chose to do. Certainly do appreciate your opinion though.
Kindest,
Marko
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Old 18th May 2013, 07:41 AM   #9
Zero D is offline Zero D  United Kingdom
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@ mnsouthpaw

Are you still going ahead with this, as you havn't responded for nearly a week ?
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Old 19th May 2013, 07:47 PM   #10
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Join Date: Nov 2011
Location: Minnesota, Land of 10,000 lakes
Hi Zero D,
Thanks for checking back in. I was not able to spend much time on this last week outside of placing an order for the subwoofer plans. Lots of good info, looks like a fun build.

I might like to reconsider the Piezo tweeter with the beta 10. Earlier you mentioned using a horn with this type of driver. I'd prefer attaching it to the back of the beta, similar to the APT-50, it looks like the treads work together. Will it not perform properly this way?
Thank you,
Marko
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