Full speaker refurbish - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

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 April 2017, 11:10 AM   #1
Mrcloc is offline Mrcloc  South Africa
diyAudio Member
 
Join Date: May 2016
Location: Pretoria
Default Full speaker refurbish

Hi. I bought a pair of unknown speakers years ago, and they weren't ever that bad. Over time I've come to see how badly built the boxes are, and they're very ugly, so I've taken everything out and I want to do a rebuild (refurbish in a way) with those speakers. I'm hoping to end up with very tall speakers.

So I've measured the bass-midrange's - there are four of them. Their specs are not ideal, to say the least. However, they did sound quite fine, so I think they're usable.

Fs is around 72 - 80 Hz
Qms is sporadic, but more or less 5
Qes is also sporadic, but averages to something like 7
Qts is average >3

They're 5" each.

In the boxes, I discovered the simplest crossovers. I know I won't be able to use them - a single 4.7 uF capacitor in series with the (laughable) tweeters.

I have a number of drivers. These four things, the two tiny tweeters, two 1" fabric tweeters (very nice Wharfedales) and a pair of 6.5" bass-mids with about Fs=65Hz and Qts of about 2.

I've also bought a cheap set of "woofers". 6.5" 8 ohm. I'll have to measure them, but they look alright. They claim to be 200W. The build quality isn't the best I've seen, but I'm guessing they're going to provide some decent bass. I have attached photos of them. If anyone can identify them, I'll be grateful.

So, I'm thinking of using a Wharfedale tweeter, two 5" mids, one 6.5" bass mid, and a 6.5" bass per speaker. The 6.5" bass mid will be in a sealed box, and the 6.5" bass will be in a ported box (probably). The idea is to make something of the bits and pieces I have. With some clever electronics, can this work well? I'm not talking B&W, but just something that looks great and goes loud with enough bass.
Attached Images
File Type: jpg WP_20170421_12_54_43_Pro.jpg (426.8 KB, 186 views)
File Type: jpg WP_20170421_12_54_56_Pro.jpg (405.2 KB, 184 views)
  Reply With Quote
Old 21st April 2017, 12:39 PM   #2
ICG is offline ICG  Germany
diyAudio Member
 
Join Date: Jul 2007
Location: Germany
Quote:
Originally Posted by Mrcloc View Post
So I've measured the bass-midrange's - there are four of them. Their specs are not ideal, to say the least. However, they did sound quite fine, so I think they're usable.

Fs is around 72 - 80 Hz
Qms is sporadic, but more or less 5
Qes is also sporadic, but averages to something like 7
Qts is average >3

They're 5" each.
A Qts of OVER 3?! No, that can't be, I don't believe that. How did you measure that?
__________________
Due to recent public demand, the light at the end of the tunnel will be turned on 7:00 to 23:00 weekdays and 9:00 to 2:00 on sa and su. And stay out of the ladies room!
  Reply With Quote
Old 21st April 2017, 01:03 PM   #3
Mrcloc is offline Mrcloc  South Africa
diyAudio Member
 
Join Date: May 2016
Location: Pretoria
Quote:
Originally Posted by ICG View Post
A Qts of OVER 3?! No, that can't be, I don't believe that. How did you measure that?
Click the image to open in full size.

I measured twice. I could have written an incorrect Qts there - it may be between 2 and 3, but it's very high. I'll post the exact measurements when I am near the speakers again (2 hours time about).

Here's an example (very similar to my real measurements):
Vrms of amplifier: 0.92 V
Test resistor: 10.1 ohm
Fs: 79 Hz
Speaker current: 65 mA at linear region
Speaker current: 42 mA at resonance
Reference value: 1.55
Measure Fh and Fl of 90 Hz and 70 Hz respectively
Qms = (Fs x reference) / (Fh - Fl) = 5.83
Qes = Qms / (reference - 1) = 10.6
Qts = (Qms x Qes) / (Qms + Qes) = 3.76

This is using this method.

If I'm doing it wrong, I'd love to know.
  Reply With Quote
Old 21st April 2017, 06:03 PM   #4
ICG is offline ICG  Germany
diyAudio Member
 
Join Date: Jul 2007
Location: Germany
Firstly, where's your Re? Secondly, you don't measure the current, you're measuring the voltage over the resistor! If you did, fine - but that's the value(s) needed to verify it, not the (calculated) current. Note down the voltages, without that it's useless. To adjust the frequency, you have to increase it - to the linear range. There's no way it's already linear at 90Hz, we're talking about probably 1kHz. See, there's one massive error wich alone makes your measurement completely useless.
And to add to it, that would be the f-range where the practically all cheap digital multimeters don't measure anything usable anymore.

There are a lot of guides how to measure it, I don't want to write the 100. one and explain it too.

Finally I have to say I find it very annoying you're trying to 'back up' your measurements with a very bad meme gif because measurements and physics doesn't found on beliefs.
__________________
Due to recent public demand, the light at the end of the tunnel will be turned on 7:00 to 23:00 weekdays and 9:00 to 2:00 on sa and su. And stay out of the ladies room!
  Reply With Quote
Old 21st April 2017, 08:51 PM   #5
Mrcloc is offline Mrcloc  South Africa
diyAudio Member
 
Join Date: May 2016
Location: Pretoria
I measure the voltage on the resistor to calculate the current. My oscilloscope measures 200 - 1000 Hz with ease. I summarized my method. Re is 3.9 ohms. And yes, 90 Hz is not in the linear region, it's Fh (measured).
  Reply With Quote
Old 21st April 2017, 10:48 PM   #6
ICG is offline ICG  Germany
diyAudio Member
 
Join Date: Jul 2007
Location: Germany
You wrote 70 and 90Hz:

Quote:
Originally Posted by Mrcloc View Post
Measure Fh and Fl of 90 Hz and 70 Hz respectively
And neither are in the linear range.

And for the osci: You have to calculate with rms, not pp. Either way, the calculation or measurement aren't correct, at the Qts check it shows a huge discrepancy, the TSP aren't consistent, these values aren't mathematically possible.
__________________
Due to recent public demand, the light at the end of the tunnel will be turned on 7:00 to 23:00 weekdays and 9:00 to 2:00 on sa and su. And stay out of the ladies room!
  Reply With Quote
Old 22nd April 2017, 06:28 AM   #7
Mrcloc is offline Mrcloc  South Africa
diyAudio Member
 
Join Date: May 2016
Location: Pretoria
70 and 90 Hz are measured points and used to calculate Q. They're described in the link. I use rms, not peak. Like I said, I would love to know if I'm doing something wrong. I'm going to do a measurement now and post the actual values.
  Reply With Quote
Old 22nd April 2017, 07:22 AM   #8
Mrcloc is offline Mrcloc  South Africa
diyAudio Member
 
Join Date: May 2016
Location: Pretoria
Here is the full calculation. I hope I'm doing it correctly.
Attached Images
File Type: png Calc.png (15.5 KB, 102 views)
  Reply With Quote
Old 22nd April 2017, 09:14 AM   #9
Lojzek is online now Lojzek  Croatia
diyAudio Member
 
Lojzek's Avatar
 
Join Date: Feb 2012
Location: Croatia
I have found ARTA so easy to use when one needs an impedance measurement that it would seem unnecessary complicated to use anything else. No amplifier needed, just one resistor and some wires.
__________________
Mankind is created for eternity.
  Reply With Quote
Old 22nd April 2017, 09:34 AM   #10
ICG is offline ICG  Germany
diyAudio Member
 
Join Date: Jul 2007
Location: Germany
Your Im is wrong.

Im = Vm / Rs
Im = 0,424 V / 10,1 Ohm
Im = 0,04198 A (let's round to 0,042 A)

And that results in a wrong Rm, the right is

Rm = (Vs - Vm) / Im
Rm = (0,94 V-0,424 V) / 0,042 A
Rm = 0,516 V / 0,042 A
Rm = 12,3 Ohm
__________________
Due to recent public demand, the light at the end of the tunnel will be turned on 7:00 to 23:00 weekdays and 9:00 to 2:00 on sa and su. And stay out of the ladies room!
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
refurbish bose 1800 HIFI4LIFE Solid State 0 5th July 2013 05:39 AM
how to refurbish speaker cones angeloitacare Multi-Way 3 24th August 2009 11:24 AM
anyone know How to refurbish Large caps? gto127 Parts 11 29th January 2009 01:09 AM
refurbish mainstream bookshelves lascalafreak Multi-Way 5 3rd July 2005 07:18 AM
About to refurbish my Cambridge R50's quick-sand Multi-Way 4 22nd February 2005 05:47 AM


New To Site? Need Help?

All times are GMT. The time now is 06:30 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki