What to do with old Audax fiberglass 6.5" and dome tweets - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

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 12th September 2012, 01:43 AM   #1
todd is offline todd  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Boston, MA
Default What to do with old Audax fiberglass 6.5" and dome tweets

I just wanted to introduce myself and try to identify some type of appropriate enclosure/crossover for these old Audax HT170f0 and TW025a1 still-in-the-box drivers which I bought over 15 years ago in high school before I knew any better.

I'm an engineer living in Arlington, MA (outside Boston) and I listen almost exclusively to classical/western art/acoustic/what-have-you with the occasional dabbling in Frank Zappa or Tom Waits.

My current equipment, which I got really cheaply is:
Naim NAIT 2 solid state, puts out a low but punchy 20W
Cambridge Audio SACD player
Systemdek IIX w/Denon DL301mkII MC cart
really beat up goodwill Thiel CS1's which I'm willing to bastardize
My reference speakers, Platinum Audio PT801, which are a 2-way with 6.5" two forward ports and metal dome supposed 45-20k -3db response.

So I think what I'm aiming at is a classic passive 3-way or maybe an open baffle, for a change. I'm willing to buy either a larger woofer or smaller mid to augment these. If I can get anything even remotely close to the sound of my current speakers I'd be happy. At the time I bought them, I figured, 90db spl for the "woofer"+ 90db spl for the tweeter and bingo I'm good to go! Now, after trolling this board for a few months I know a bit more. These are the specs I'm working off since I have no provision to measure:

HT170f0
TW025a1

So the first and most obvious thought is a typical box, I could use the 6.5" as a sealed mid and buy a good woofer to augment it at the bottom. Basically the 6.5 would operate on the upper end as if it was a 2-way then right? My issue with this is that the tweeter seems to like crossing over in the mid-2k range but the FR chart for the 6.5" looks like it has a major hump starting at 500k, how can I deal with this? I was thinking maybe a simple 1st order low pass somewhere around 1k might bring it down but then I'd need to cross the tweeter at 1.5k with a steeper slope and I don't believe it can handle that. So either I ditch the tweeter for something that can, or instead of buying a woofer I buy something that'll fill in from 500 to 3 or 4k and just accept the limited extension of the 6.5" working as strictly LF. I've read the beginner's crossover design sticky but I'm still at a loss.

Either way this driver seems like a drag to me. What am I not seeing here?

My other thought is to just go open baffle with it, then I'd certainly need a big "pro" type unit down below for the low end. Maybe like a manzanita-with-a-tweeter type thing?

So, boiling this all down. My main question is how to mate these things reasonably with the tweeter, if it's even possible. And should I be looking at a big ole' woofer or pro driver for the low end?

I realize this isn't the proper way to engineer a speaker, but as I said, I have the drivers already so I'm just trying to come up with something interesting to do with them.
  Reply With Quote
Old 12th September 2012, 04:25 AM   #2
diyAudio Member
 
Join Date: Feb 2002
Location: Western Sydney
I think a good 2-way is possible with these, but you've correctly identified that the main issue is dealing with the woofer crossover. The 500Hz hump could be dealt with by adding a BSC inductor, the tweeter will need some corrseponding attenuation. More importantly, the FR response graph seems to have been smoothed rather optomistically, the fibreglass cone is a bit peaky higher up, if you use a 2nd order crossover (at 2.5KHz) + the baffle step inductor this may reduce those peaks enough. Box size & tuning & the tweeter crossover can come straight from the data sheets.
__________________
Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency

Last edited by PeteMcK; 12th September 2012 at 04:28 AM.
  Reply With Quote
Old 12th September 2012, 10:07 PM   #3
todd is offline todd  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Boston, MA
Hey, that's great! Thanks for the response, so you think baffle step will do it for the woofer eh? Last night I was looking into notch filters but I'm not sure they'd be any help afterall. Your plan sounds as good as any to me. Would it be easy enough to convert it to a 3-way after making a 2-way version? (lord knows I have enough 2-way's kicking around right now...) I suppose the mids won't get much better than I'm used to being peaky as you said, but perhaps the low end would.

At any rate, I guess that could be a battle for another day. The enclosure on the sheet looks pretty big though, 45L for 40-50hz. Maybe I can use the old Thiels for them and avoid having to make enclosures, I believe they are around that size and although tired and chipped up they are extremely heavy and solid. They also have the same size and number of drivers. If they turn out to sound nice then maybe I can take the next step and build some tall 3-way cabinets and add the woofer.
  Reply With Quote
Old 13th September 2012, 03:54 AM   #4
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
Todd,
I don't really know the 61/2" driver but I do have a bunch off the tweeters. As far as a soft dome tweeter goes this is one of the nice ones. I cross them over at 2.5khz myself with a 4th order L-R crossover to a 6 1/2" that I make myself so they are unobtainium. But I wouldn't count out that tweeter it is very flat out to the top end and very few other soft domes sound any better than they do. You could easily add a larger bass speaker to your system but then you will have to use a band pass filter on the mid driver.

Steven
  Reply With Quote
Old 25th September 2012, 07:47 PM   #5
todd is offline todd  United States
diyAudio Member
 
Join Date: Nov 2004
Location: Boston, MA
Thanks, I like the tweeter, although the FR chart makes it look a little bright in the dog-hearing range... Not sure that I'd even notice since it's over 15k. So, I guess I'm looking at a 2.5k crossover point and a BSC. Do you think 830hz is a good F3 for the BSC based on the audax chart link for the 6.5?

Once I do that BSC it'll level off that big 1.5khz hump, but it seems like it'll roll off naturally at around 2.5khz after that, maybe I wouldn't even need anything besides that and a high-pass for the dome.

I bought some thin masonite HDF just for mocking something up so I can get an idea of the sound of these things and what the crossover bits will do. I'm just about to order a 1.5mH inductor and an 8 ohm resistor for the BSC if someone can verify that 830Hz or so is a good spot for it.
  Reply With Quote
Old 25th September 2012, 08:43 PM   #6
diyAudio Member
 
mondogenerator's Avatar
 
Join Date: Sep 2009
Location: City Of Villans
Blog Entries: 1
Yes I agree the tweeters look good, the 30deg plot tells the important story. I never owned that model, but ive owned TW025F1 which are OK, and the titanium coated solf poly domes, which were rank awful. At least in my use of them...
__________________
Every new piece of knowledge pushes something else out of my brain - Homer.....................Simpson
  Reply With Quote
Old 26th September 2012, 03:15 AM   #7
diyAudio Member
 
Moondog55's Avatar
 
Join Date: Jun 2007
Location: Norlane; Geelong: Victoria: Australia
I just had a look at the FR for the drivers, since I never made a 2-way I ever considered any good in the bass I would go for a classic 3-way with a decent big woofer. Even better 2 woofers on opposite sides of the box and forget about BSC. I'd be tempted to design a little higher (3250) and use a shallow peak filter centered on or around 1200/1500.
__________________
QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"
  Reply With Quote
Old 26th September 2012, 03:38 AM   #8
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
MoonDog55,
I use to have a handbook that Audax had with all of their different drivers in there. They were one of the early adopters of the Thiel-Small method of qualifying a driver and they seemed to make a damned good device for the price. If I remember the cone speakers they usually had a rather oversized magnet structure and light weight paper cones. I use that tweeter cut at 2.6khz and have not every burned one out myself and that is at some very high SPL levels. I go with your plan for a three way design though. A good size driver over 10" should do what you are looking for. Even a nice 15" crossing over low enough to the 6 1/2" will work great. I'd probably get into the 6 1/2" lower than most as the problem with going higher with a 15" is that though it might get up to 1Khz that would be my upper limit before the off axis control goes away. That is my opinion and I am sure that others will have there own.
  Reply With Quote
Old 26th September 2012, 03:59 AM   #9
diyAudio Member
 
Moondog55's Avatar
 
Join Date: Jun 2007
Location: Norlane; Geelong: Victoria: Australia
My reason for the higher XO point was merely that this is where I thought mine hit the sweet spot. I was lucky enough to get a pair cheap a few years ago. I first used them @~6k with a 2uF cap but I thought they sounded better down lower.
3250 was my best guess for equal slopes on each side of the peak filter and is a reasonable compromise for the midrange. Note the usual provisos that i don't know what I am doing sometimes and i do not have "Golden Ears" or even copper ones sometimes
__________________
QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"
  Reply With Quote
Old 26th September 2012, 04:07 AM   #10
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
Just seems like you are starting to get into the cone breakup mode of the 61/2" around that frequency. Not knowing the exact od of the cone I am surmising from experience here. Perhaps a little high for my taste to crossover the two devices.
  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
The ubiquitous 1/2"...um....3/4"...er 1" ?? polycarbonate "dome" tweeter River757 Multi-Way 16 8th July 2013 01:45 AM
b/n harman h25-1 1" woven textile soft dome tweets, 4 ohm, neo mag honkyg Swap Meet 0 12th April 2012 04:56 PM
Wanted Dead Audax HD3P gold dome pizzo tweeters spresto9 Swap Meet 0 24th June 2010 09:33 AM
Replacement dome for Audax tweeter JohnL Multi-Way 2 24th October 2007 12:00 AM
Has any one use the AUDAX TW025A18 1" TITANIUM DOME TWEETERS ? jewilson Multi-Way 3 5th July 2004 10:34 PM


New To Site? Need Help?

All times are GMT. The time now is 08:05 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2