Definitive technology DR7 Tower(1992) mod/refresh - diyAudio
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Old 20th April 2014, 12:04 AM   #1
juliopr is offline juliopr  Puerto Rico
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Default Definitive technology DR7 Tower(1992) mod/refresh

Hello there.. I have a pair of Definitive Technology DR7 speakers which somehow sound a little tired.. I would like to know if anyone has ever worked with these.. They came with a Vifa P17WJ-00 4ohm midbass and a Vifa D26TG-05 6ohm tweeter. It has a linkwitz-riley type crossover and a great anti- resonant cabinet. I would like some ideas of drivers as replacements.. I plan to eliminate the passive crossover and use an analog active one that I already have with a multi channel amp for biamping. I have a Pair of Vifa DX25TG05-04 tweeters and SB Acoustics SB17NRXC35-8 midbass units that I could use. Thing is, Are these units suitable for the task? Opinions? Comments? Ideas? All are very welcome....
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Old 20th April 2014, 02:38 AM   #2
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Hi,
If, if, if...
What kind of sound you have; describe, is it the full range or only at crossover frequency, nulls(?)... tweeter or midbass... is it "tired" in the fullrange.
Do you want to resurrect the speakers or build new ones?
Post some pictures of the crossover (front and back) in the forum so that other members can review your bads like lytic cap, tweeter ferrofluid, etc.
(Good) Speakers don't get "tired", they get better with time like the wine (some).

Your drivers:
Vifa P17WJ-00-04 link1
Vifa D26TG-05-06 link2, link3

So after checking that drivers are fine (or not) substitute the dubious caps in the crossover.()
Checking the tweeter: use the new tweeter you have available just as a test to see how this plays the high frequencies and crossover range (as an experience just checking, one tweeter is 4 ohms the other is 6 ohms). Waiting for results but my impression is if your (first) tweeter is louder then is fine, they might be similar the new sounding nicer in frequency range(?).

New OP drivers, available for new build:
SB Acoustics SB17NRXC35-8 6.5" link4
Vifa DX25TG-05-04 link5

If you want to use a substitute for the original midwoofers you can with this new 180mm driver (reference is 170mm) but I would think that a vintage driver with rubber surrounds is better now, after all...
Vifa PL18WO09-04 7" link6 - pdf
A few suggestions are given here that might look stupid at first but it all depends of your tests and feedbacks and I believe you can resurrect your original speakers/enclosures and build a new nice set with such nice drivers. If your option is to save the enclosure from the original to the new drivers and put apart the drivers then it needs to be seen. Some adjustments in the original crossover might have/give the results you would expect also. So better to have some feedback here where you want to go.
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Old 20th April 2014, 11:59 AM   #3
juliopr is offline juliopr  Puerto Rico
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Thank You, Inductor, for your reply.. I took out the woofers and their cones are at a lower level in the basket and when you push them softly, a raspy sound appears, as if the coils were making contact with the magnet pole piece. and the highs are pretty recessed.. The drivers I have available were purchased for an Open baffle 3 way project, but I am no longer considering them for that anymore and I think will make a great difference in the DR7 cabinets.. These towers are pretty rigid, elegant and well built.. I once made a comparison removing the passive crossover and using the active one I have and biamped the drivers and it made a hole lot difference in detail and dynamics...So that is why I would like to go active, but also replace the drivers with new (better?) ones..
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Old 20th April 2014, 01:12 PM   #4
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You can use the same new drivers SB Acoustics SB17NRXC35-8 6.5" in the original enclosures for the Vifa P17WJ-00, after we check it's dimensions.
Post internal or external dimensions (1). If posting external dimensions please be sure to add thickness of the enclosure (pictures help).
The same for the old Vifa drivers if using an upgrade with the active system (2 amps) you can use a standard 8 ohms but be sure to check enclosure dimensions for the alignment first. Add here the port (2) dimensions: it's internal diameter and length.
To upgrade to a 8 ohms:
ScanSpeak Classic P17WJ00 6.5" Woofer
Post dimensions for #1 and #2.
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Old 20th April 2014, 01:54 PM   #5
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I'm not sure if the monitor is a reflex and the tower a TL (transmission line), anyway.
Dimensions (tower):
8.5in = 21.59cm W
11.5in = 29.21cm D
35in = 88.90cm H
Front baffle, approximate 1in = 2.54cm
Volume in Liters: 33.4L = 1.1795ft³ ~31 Liters* (net)
(*Considering internals, driver + bracing)
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Old 20th April 2014, 02:15 PM   #6
sreten is offline sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Hi,

No analogue active x/o will work properly unless
specifically designed to do the same job as a
properly designed passive x/o.

It will be wrong, but will sound "bright and detailed".

Take a look at this properly designed 2 way :

Zaph|Audio - ZA-SR71

The x/o functions (for 4th order L/R acoustic @ 1.75KHz):

Click the image to open in full size.

Note they are nothing like preset 2nd or 4th order L/R active x/o's.
(Except in this case the high pass is ~ 2KHz 2nd order L/R electrical.)

rgds, sreten.


http://audio.claub.net/Simple%20Loud...ign%20ver2.pdf
http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://web.archive.org/web/200909021...esigningXO.htm
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Last edited by sreten; 20th April 2014 at 02:34 PM.
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