Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

2 Way PA system with Celestion CDX1-1745
2 Way PA system with Celestion CDX1-1745
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st June 2018, 06:52 PM   #1
darrylis is offline darrylis  Canada
diyAudio Member
 
Join Date: Oct 2016
Location: Canada
Default 2 Way PA system with Celestion CDX1-1745

Folks,

I'm new to speaker builds etc., however, found a compression driver at a sale i.e.: Celestion CDX1-1745.

I'm planning on building a small PA system for guitars, keys, bass and vocals etc. I was wondering what would be a suitable woofer to mate with it. One that came to mind was the Eminence Alpha 15A and the other was a generic B&C. Any advice would be of great help.

I want to keep the following goals in mind:
  • Great sound quality (least distortion etc.) and dynamics
  • Freq range from 40-20k at least
  • Two way speaker only

The following questions come to mind:
  1. Should I be indifferent between the woofers listed below?
  2. Would both woofers be capable of an open and closed baffle design?
  3. Are there better woofers at the $100 price point?
  4. What would be the best crossover point 2.5k or 2k for either of them?
  5. Can a crossover be eliminated completely, by using a low/high pass filters using capacitors and resistors only?

Details are stated below:

Celestion CDX1-1745 Ferrite 1" Compression Driver 75W
Celestion CDX1-1745 Ferrite 1" Compression Driver 75W

Eminence Alpha-15A 15" Driver
Eminence Alpha-15A 15" Driver

B&C Generic Woofer 15” 8 Ohm Neo
(See attachment)

Attached are some details for the drivers.

Thanks in advance for all the help.
  Reply With Quote
Old 21st June 2018, 06:55 PM   #2
darrylis is offline darrylis  Canada
diyAudio Member
 
Join Date: Oct 2016
Location: Canada
I don't think the attachment came across. Here it is.2 Way PA System.jpg
  Reply With Quote
Old 23rd June 2018, 09:39 PM   #3
Think is offline Think  Netherlands
diyAudio Member
 
Join Date: Nov 2017
Location: Den Haag/The Hague, Holland, The Netherlands
2 Way PA system with Celestion CDX1-1745
Off axis response of the 15" will be crap at 2k. Better go 3 way or 2 way with a smaller woofer and a separate sub-woofer.
__________________
* It's better to have a system which sounds good and measures bad, then one which measures good and sounds average.*
  Reply With Quote
Old 23rd June 2018, 11:56 PM   #4
turnitdown is offline turnitdown  United States
diyAudio Member
 
Join Date: Feb 2014
Cross your woofer lower and you should be good. Read Wayne Parham of Pi speakers. It's done very satisfactorily with a 15 and horn/cd.
  Reply With Quote
Old 24th June 2018, 05:16 PM   #5
chris661 is offline chris661  United Kingdom
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
I don't like to be the bearer of bad news, but you've a lot of reading and learning to do.

First up, go and learn to use WinISD Pro. That'll let you get an idea of the cabinets that might meet your targets.
It'll probably tell you that the Eminence Alpha 15A isn't suitable for much in the PA world, and the B&C driver will probably want a very large enclosure to get to 40Hz with authority. Even then, it won't have much output due to the limited Xmax.

You're going to need to use ported boxes. Sealed boxes are rarely enough for a PA situation - I used 4x Beyma 15P1200Nd in sealed boxes, and they were just about enough for smaller gigs. Ported boxes give the driver much more help.
Open baffles actually throw away low-frequency output, so you'll need a lot of cones to come close to a single good ported driver.

Generally, the larger the cone, the worse the midrange performance, as well as the narrower the dispersion. I'd be hesitant to run a 12" driver up to 2kHz, and would much rather keep it to 1kHz. A 15" driver running that high is going to sound bad in front of the speakers, and will lose a lot of midrange as soon as you take two steps to the side. When you want the entire audience to get a good clear sound, a 15" cone crossing to a small compression driver simply isn't going to cut it.


IMO and IME, you need to re-think your targets.

Some things to think about:
- What are you going to power this with?
- Do you have a measurement setup, or are you going to be doing this by ear?
- Do you have all the other things required to get a band PA system up and running?


I can see two ways for you to proceed here:
1 - 2x10" 2.5-way with that compression driver, and maybe stretch to a 2kHz crossover point.
2 - 15" two-way cabinet, with a decent 15" unit and a large-format compression driver with a <1kHz crossover point.
3 - Buy an active PA speaker and have done with it. All the work is done for you, including driver protection etc etc.

If you wanted a one-box two-way full-range solution, #2 is the answer. Smaller drivers compromise low-frequency extension, but are easier to manage in the midrange.

Chris
__________________
My work: www.grimshawaudio.com
  Reply With Quote
Old 24th June 2018, 06:02 PM   #6
weltersys is offline weltersys  United States
diyAudio Member
 
weltersys's Avatar
 
Join Date: Jan 2008
Location: Florida
Quote:
Originally Posted by darrylis View Post
Folks,

[1]Should I be indifferent between the woofers listed below?
[2]Would both woofers be capable of an open and closed baffle design?
[3]Are there better woofers at the $100 price point?
[4]What would be the best crossover point 2.5k or 2k for either of them?
[5]Can a crossover be eliminated completely, by using a low/high pass filters using capacitors and resistors only?
1) The +10dB spike at 2kHz in the Alpha 8 is difficult to eliminate with passive components.
2) Yes, but you will want ported enclosures to achieve usable bass output with those drivers.
3) Not much, if any.
4) Around 1500 Hz would be "tops" for a 15", around 800 Hz better, but requires a larger diaphragm HF driver to "keep up".
5) A crossover can't be eliminated.
Passive line-level crossovers (PLLXO) can be made using capacitors and resistors. Input impedance of the power amplifier and insertion loss need to be factored in.
With the price of active crossovers and digital processors so low, little money could be saved by the time all the components for a PLLXO are sourced, and still don't address the EQ needed to make a system sound decent.
Passive crossovers in the speaker cabinets are difficult to design properly, and use rather expensive capacitors, inductors and resistors, but do save an amp channel.

Have fun, good luck!

Art
  Reply With Quote
Old 25th June 2018, 05:54 PM   #7
darrylis is offline darrylis  Canada
diyAudio Member
 
Join Date: Oct 2016
Location: Canada
Folks,

Thanks for all the pointers. I've been trying to read up on some material as suggested i.e.Wayne Parham etc., but is quite technical.

In the meantime I'll download the WinISD to figure out enclosures etc.

Since I am getting the compression drivers for $25 a pop, I thought I could learn and build something at the same time.

However, from all the comments, I can gather the following:
  • Ported enclosure may be my best bet.
  • Crossover should be lower than 1.5k, at a minimum (dependent on woofer size, I presume).
  • Smaller woofer size will help tremendously especially with the mid range, two 10" woofers may be a better option than one 15" (though 15" may go lower).

Thanks to all of you i.e.:
  • Think
  • turnitdown
  • chris661
  • weltersys
  Reply With Quote
Old 26th June 2018, 01:08 PM   #8
Think is offline Think  Netherlands
diyAudio Member
 
Join Date: Nov 2017
Location: Den Haag/The Hague, Holland, The Netherlands
2 Way PA system with Celestion CDX1-1745
YW, the best choices are the ones best for your use.
In general a 2 way top (6-8" woofer) speaker with a separate sub-woofer(s) is probably the most efficient way to go in terms of sound quality, money, portability and placement options.

Placement is IMO so much overlooked; subs like to be one the ground in corners or at walls and all close together or more the 40feet apart at 40hz up; to prevent cancellations and to get 'tight' bass.


If your also have to buy an amp, a 3-4 channel model with an internal/onboard ~100hz x-over is an interesting option for a small PA system.

A step up and a lot more flexible and a great way to experiment with / learn from your system is to get yourself a DBX PA2, which is a digital crossover, equalizer, RTA (with setup wizard which is quite good) limiter, compressor, etc. and use separate amps for sub and tops and maybe even the tweeters. You can adjust this unit from your phone, pc or tablet while listening to it. Good PA (high power) passive crossover components get expensive to, and designing a good crossover is not simple, setting up a digital one is.

Also consider to go with 4 tops, where your can put the upper one upside down on the lower one to keep the distance between the tweeters the smallest. 4 Small top speakers are much easier to carry around and versatile then 2 big ones. You won't need extra amps to run the 4 as they are probably 8ohm and almost all amps run at 4Ohm. (2 speakers per channel/side)
4 (5+ in reality, power compression) times the amount of power or doubling the speakers gives you +6dB extra. So generally 4x100w is about as loud as 2x500w and will sound better.

It started with a cheap tweeter...

Last edited by Think; 26th June 2018 at 01:20 PM.
  Reply With Quote
Old 28th June 2018, 02:26 PM   #9
darrylis is offline darrylis  Canada
diyAudio Member
 
Join Date: Oct 2016
Location: Canada
Quote:
It started with a cheap tweeter...
Unfortunately, was getting a good deal on a tweeter and was wondering what I could potentially do with it.

I should perhaps rephrase my original question:

If I had to build a 2 way PA system, how would I go about, keeping the following in mind..:
  • 200 watts per channel
    No active crossover/bi-amping etc.
    40-20K freq range
    Great sound and dynamics
    Component cost max $400 i.e. for woofers and crossovers

The question is what components should I buy ?
  Reply With Quote
Old 28th June 2018, 02:56 PM   #10
chris661 is offline chris661  United Kingdom
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
I don't think it's possible.

Getting 40Hz at decent volumes from a PA speaker is non-trivial in itself. To give you an idea, I use ported boxes with Faital Pro 15HP1060 drivers and hit them with a Crown MA12000i. A pair of those will do rock 'n' roll levels for a couple of hundred people indoors. Those particular drivers (and other 15" subwoofer drivers like them) get quite ragged above 1kHz, so wouldn't be able to meet your compression drivers.
There are 15" midbass drivers available that are more efficient, but they don't have enough linear cone excursion to get down into the bass like the sub drivers do.

If you relax the low-frequency requirement to 65Hz, life will get much easier for you. There's even a chance it'll sound good.

Chris
  Reply With Quote

Reply


2 Way PA system with Celestion CDX1-1745Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Celestion CDX1-1425 deviations Salas Multi-Way 36 30th April 2016 03:43 PM
FS: 2 Celestion CDX1-1745 Ferrite 1" Compression Driver 75W doug20 Swap Meet 1 20th January 2016 08:38 PM
USA Supplier for Celestion CDX1-1747 POOH Multi-Way 11 15th February 2014 05:05 PM
Celestion CDX1-1745 ..... What can I do with them? poynton Multi-Way 2 22nd June 2010 06:01 PM
BMS 4538 Driver vs Celestion CDX1-1745 gkoutz Multi-Way 0 1st August 2007 02:54 PM


New To Site? Need Help?

All times are GMT. The time now is 05:48 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki