Choosing between 2 types of Jensen Ultra-flex (onken) cabinet designs - 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 9th August 2011, 04:48 AM   #1
diyAudio Member
 
Join Date: Apr 2005
Location: Maryland
Default Choosing between 2 types of Jensen Ultra-flex (onken) cabinet designs

I am making plans to build a cabinet based on the Jensen Ultra-flex design. A Jensen DIY manual from the 1950's shows two versions---one that looks like a modern Onken with vertical vents on the front of the cabinet, and a second that has the vents on the back corners at a 45 degree angle. Both types have about the same footprint so size isn't a factor. The two versions are shown on the sites below:

http://www.dcaudiodiy.com/jensen_imperial/page_13.jpg

http://www.dcaudiodiy.com/jensen_imperial/page_14.jpg

Does anyone have experience with both types of designs to help me choose one over the other?

I will be using Jensen P15LL woofers which are the intended drivers for each of these Ultra-flex designs. The woofer will hand off around 1K to an Altec 802-8G in an Altec 32A horn.
  Reply With Quote
Old 11th August 2011, 01:42 AM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I built the front firing design and it is certainly easier to build, and perhaps is a little less critical as to placement, but that is a swag. The rear port version might avoid the comb filtering issue that exists with the front firing design, but I suspect might be happier in a corner.. All a guess on my part, all I can say is I am pretty happy with the ones I built 5yrs ago, and they are the "built in" forward firing style. With some sadness I might note that I am absolutely the only one with a pair within the group I run with - plenty of interest, just too big I guess for most hobbyists. So far I have not heard anything else that makes me think I made a mistake..

I am crossing at 800Hz and 8kHz to a JBL 2440 on 2311 short conical horn/2308 vane diffuser and 2402 ring radiator.. Directivity is deliberately narrow in both the horizontal plane and vertical plane, and imaging is very good at my listening spot - the room is fairly modest in size with a 7' ceiling.. Cross-overs are 12dB/octave butterworth passive types of my own design.. Power is 7-8Wrms per channel of broadband 300B power..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 11th August 2011, 06:17 AM   #3
GM is online now GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
For me, the corner cab is the only Ultra-flex, but then I prefer corner loading regardless of cab design. It works best against a really rigid corner though, so ideal for the below grade concrete constructed basement I had mine in.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 11th August 2011, 06:39 PM   #4
diyAudio Member
 
Join Date: Apr 2005
Location: Maryland
Thanks for the replies. I agree with Kevin that the possible comb filtering with the front-facing ducts may be a concern, especially since I will be using a slightly higher crossover (1K vs. 800). Right now, however, I am leaning towards the front-facing approach mainly due to the simplified woodworking; only right angle cuts are needed. Plus my cabinets will be a few feet out into the room, not in corners or near the back wall.

Dave
  Reply With Quote
Old 11th August 2011, 08:50 PM   #5
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Hi Dave,
Although I can measure some bleed through the ports at higher frequencies and there is probably some comb filtering going on as well due to the configuration I don't hear anything untoward. It may also be that my cabinets are a bit under damped due to my light use of acousti-stuff on the back, bottom and side panels - my ports aren't stuffed either. I'm quite happy with the results and have heard VOTs, RCA Ubangis, JBL C37, C40 and a number of bass reflex cabs and remain satisfied. Efficiency is high, extension is into the low 30s and they are very tight & clean sounding..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 11th August 2011, 10:46 PM   #6
GM is online now GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
Originally Posted by kevinkr View Post
Hi Dave,
Although I can measure some bleed through the ports at higher frequencies and there is probably some comb filtering going on as well due to the configuration I don't hear anything untoward. It may also be that my cabinets are a bit under damped due to my light use of acousti-stuff on the back, bottom and side panels - my ports aren't stuffed either.
Greets!

Vents 'close up' with increasing frequency, so what you're hearing are the strong half WL pipe harmonics of all those crude musical instruments and with minimal internal damping you may also be getting some bleed through due to reflections modulating the back of the driver diaphragm, both of which are comb filtering with its output and at higher SPL may be loud enough for the higher orders to comb filter with the mids/HF horn.

This was a major problem with the large Altec 210 combination horns and why I finally whacked off all the excess to make them compression loaded and added a sub system.

Well, there's clean and then there's 'clean' which is more accurate, but folks who prefer the 'richer' harmonic distortion of these types of cabs, especially when tube driven, don't much care for the price of increased accuracy, i.e. it sounds too 'dry'/'sterile' in comparison.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  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
Onken cabinet The gun Multi-Way 9 11th November 2008 06:35 PM
TAD TL-1603 in Onken Cabinet ? matsj Multi-Way 9 28th August 2008 07:12 PM
Flex hose as port in vented cabinet ? Jan Dupont Subwoofers 19 27th March 2007 04:53 PM
Anyone familiar with the Jensen Sono-Dome Ultra tweeter. Shoog Full Range 2 1st June 2005 09:36 PM
Jensen Onken f.bcn Multi-Way 1 13th November 2002 08:09 PM


New To Site? Need Help?

All times are GMT. The time now is 07:11 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2