18" speakers

Dedicated to those large boxes at one end of the room
User avatar
Ali Tait
Eternally single
Posts: 4374
Joined: Fri Jun 08, 2007 8:10 pm
Location: Galashiels

#226

Post by Ali Tait »

To be slowly digested over a thousand years.
User avatar
Dave the bass
Amstrad Tower of Power
Posts: 12273
Joined: Tue May 22, 2007 4:36 pm
Location: NW Kent, Darn Sarf innit.

#227

Post by Dave the bass »

Unless you happen to be Bobba Fett. <pushes glasses up nose and blinks awkwardly> :)

DTB
"The fat bourgeois and his doppelganger"
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#228

Post by pre65 »

After extensive listening since the full range speaker was replaced, and with the aid of Andrew I's ears, I'd like to experiment with the sound balance between the two drivers.

Ideally I'd like to reduce the full range output just a tad, or increase the woofer volume.

Thing is, with a series crossover, I'm not sure how to do it. :oops: :?

Here is the crossover diagram. Any hints or tips from crossover experts ?

Image
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8873
Joined: Mon May 21, 2007 9:42 pm

#229

Post by Paul Barker »

Image
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#230

Post by pre65 »

Thanks Paul.

I clip leaded in a 1R resistor, and that has made a positive difference.

Will try other values later on. :)

Somewhere I have a few 0-2.5R pots, could try those if I can find them.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#231

Post by pre65 »

Now trying a 2R resistor.

Slightly better on first listen.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8873
Joined: Mon May 21, 2007 9:42 pm

#232

Post by Paul Barker »

many years ago it was discovered on the forums that Lowthers benefited from thin wire. But all that was happening was a series resistance was applied. Just as you are doing here with your fostex. Maybe the fostex benefits like the lowther from a little series resistance. All of which is asside from the fact that you need to attenuate the fostex. you could have done it with an L Pad attenuator but this way tends to work well in the circumstances, at least that has always worked well for me on listening tests.

Although what I know in this scenario could fit on a postage stamp.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
User avatar
Scottmoose
Needs to get out more
Posts: 1802
Joined: Sat Sep 08, 2007 11:03 am
Contact:

#233

Post by Scottmoose »

They can do: depends on the driver Q, the output impedance of the amp, box / baffle / whatever alignment, what you like & what you're trying to do. ;) Many of the large motor Fostex units have similar basic Q & general characteristics to Lowther drivers. You're just adding distributed series R so a slightly different effect to an L-pad where impedance is held constant. In the rising response (acceleration) BW, that has the effects you'd expect. Can also be beneficial higher up in the mass controlled BW, providing system efficiency is high enough.

Leaving aside the increase in system Q I suspect one of the reasons for the brief flurry of interest back around the turn of this century was that the really thin gauges can't properly handle low-frequency current demands, so for want of a better phrase, LF dynamic peaks were 'clipped' relative to the rest of the range, which can have the effect of seeming to enhance detail in the 'unclipped' mid - high range. Either way, it's a valid enough approach & resistive wire is not something to be ignored, providing it's employed with care.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#234 Re: 18" speakers

Post by pre65 »

I've bought a couple of Mark Audio tweeters from Colin, and they are destined for my baffles.

I have ordered a 43mm hole saw today, so perhaps by next week something might have happened. :wink:
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#235 Re: 18" speakers

Post by pre65 »

I had a lull in the mosfet amp proceedings, so using the 43mm hole saw I've cut out the tweeter apertures.

They are now in situ, but I'll leave wiring up and cap selection testing till another day, I've got too much on at the moment.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Nick
Site Admin
Posts: 15708
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#236 Re: 18" speakers

Post by Nick »

I would have thought after 7 years of this thread it would be time for some measurements :-)
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#237 Re: 18" speakers

Post by pre65 »

Nick wrote: Fri Mar 31, 2017 2:27 pm I would have thought after 7 years of this thread it would be time for some measurements :-)
Quite possibly Nick. :)

Although some would say that measurements are totally unnecessary. :wink:
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Dr Bunsen Honeydew
Old Hand
Posts: 1358
Joined: Mon Sep 21, 2009 10:50 am
Location: Muppet Labs

#238 Re: 18" speakers

Post by Dr Bunsen Honeydew »

If you are going to design the drive unit you need to measure, if you are just going to use those designs you only need to listen
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#239 Re: 18" speakers

Post by pre65 »

I sorted through my capacitor box a while ago and thought I had got some polyprops to try with the MA tweeters I got from Colin, but I can't find them now. :(

I might have put them somewhere "safe". :lol:

Anyway, I've found a pair of MKT 3.3uf so I'm trying those as a first step. Just listening to Solid Air, and the treble is more prominent.I'll try some contrasting tunes later.

Just ordered two 2.2uf MKP for the next trial.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
cressy
Shed dweller
Posts: 2906
Joined: Fri Aug 03, 2007 7:07 pm
Location: the great white space
Contact:

#240 Re: 18" speakers

Post by cressy »

Pad it down with a 0.5r resistor, it may be that the efficiency means a little padding is necessary. Mine have a 1r in series to do this as they are a little more efficient than the 6" drivers
Post Reply