Starting Out - Fostex 127

Tetsuo36 · 8th April 2009, 04:25 PM

Hi,

Just finished my first audio DIY, an AMP6 from 41hz. Really nice.

Now moving on to speakers as my 8ohm low sensitivity Tannoys are just not up to it.

Intended to use Fostex 127 and to go the madisound bass reflex route, my DIY skills are not up to the horns just yet. It seems to be a simple introduction for me and cheap, £300 all in.

The Amp6 is 4ohms so i intend to use 2 drivers, in parallel for each channel, this would be 4 speakers in total. Not sure whether it would be best to combine 2 speakers to appear as one, with parallel wiring length kept to the very minimum, or 4 seperate speakers paralleled at the binding posts? I think trying to incorporate 2 drivers in a single cabinet is a more difficult proposition.

Also is a BSC required or should i just do it, allow burn in and assess later?

In fact any advice/opinion would be appreciated. Alternative drivers, designs, issues etc...

Thanks in advance.

HareBrained · 8th April 2009, 05:11 PM

When working with two drivers playing the same frequencies (all in this case), at some point, their separation (center-to-center) will greater than the wave length of some audible range. This can result in the two drivers being identifiable and interference effects. You should have them as close as mechanically possible. They also need to be on the same acoustic center plane. In separate cabinets, it can be physically done but in the same cabinet, it is assured.

Baffle step diffraction is a function of speaker placement. When close to the wall or TV or other large planer surfaces, the amount of compensation is reduced. If you're going to put them into the room and away from other things (i.e. dedicated listening room), you'll want the full compensation (~6db). Most people have spouses and thus don't need full compensation, so 3-4db is typical.

One alternative to the LR when using 2 drivers is to create a 1.5-way crossover. This is where one driver is used as the BSC and has a low pass filter set to 800-1000Hz. This is a better alignment because instead of suppressing the upper frequencies of both drivers, one driver is full range and the other contributes it full capabilities up to the LP filter.

John

inrank · 8th April 2009, 05:16 PM

or use two in bipole

Tetsuo36 · 11th April 2009, 07:36 PM

Hi, my understanding (limited) of bipole is for surround sound speakers with 2 drivers directing sound to the front and back of the room. I do not think this is what i am after, i just want to create a good stereo sound. I do not have a dedicated listening room (wife/kids) so the speakers are in the corners of the room, 12" from the wall.

I was seeking to use 2 drivers in parallel simply to get to the total ohms down to 4 to maximise my amps 2 x 25w output and because i could find easy to build bass reflex plans. Additionally Fostex are well thought of.

Maybe i need to research more, find some 4ohm drivers etc and alternative cabinet designs? Any pointers would be good. I am very new to this.

Regards, Mark.

planet10 · 11th April 2009, 08:43 PM

Quote:

Originally posted by Tetsuo36
I was seeking to use 2 drivers in parallel simply to get to the total ohms down to 4 to maximise my amps 2 x 25w output and because i could find easy to build bass reflex plans. Additionally Fostex are well thought of.

If you think it thru, that might not be the best idea. 1st the Fostex are quite efficient and 10 w is just fine (my main amps which i drive my 127s with is 3.8 W. At 4 ohms your amplifier has ~ 2x the distortion it does at 8 ohns (and the Fostex are revealing enuff to show it up)

Quote:

so the speakers are in the corners of the room, 12" from the wall

Another approach would be to take advantage of the corners ... build a set of Frugal-Horns or RonHorn A126 that use the corners... the FE126 you use in those is ~ 3dB more efficient than the FE127, so that is like doubling the available power. The box isn't as easy to build thou.

dave

AdamThorne · 11th April 2009, 09:33 PM

Planet10 and his cohorts are an excellent resource when it comes to fostex speakers, if you didn't already know. Check his websites, and depart from his advice at your own peril.

Tho if I had corners to load, I'd want to make a BIB my first build. Simple enough construction that one wouldn't feel too bad about discarding the box and making something else w/ the drivers, should it be necessary.

HareBrained · 12th April 2009, 08:35 PM

Tetsuo36, Have you researched getting a prebuilt cabinet? I only know of ones here in the US and would be costly to ship but there are some that would be reasonable for the Fostex drivers.

I will mention that I just completed a set of computer speakers using the Mark Audio CHR-70 and I'm very impressed with them. They're an incredible value if cost is an issue but sensitivity is only marginally better then your Tannoys. They're already 4-ohms and thus only one would be needed.

The Audio Nirvana drivers at http://www.commonsenseaudio.com/ would be an interesting complement to the Amp6.

Lastly, consider the Fonkens over on P-10. All straight cuts and fairly simple to build. While you're there, check out the phase plugs for the Fostex drivers. As Scottmoose says, they're a must.

planet10 · 12th April 2009, 09:57 PM

Quote:

Originally posted by HareBrained
While you're there, check out the phase plugs for the Fostex drivers. As Scottmoose says, they're a must.

For the whizzer cone drivers. For FE127primamrily for accident recovery

dave

Tetsuo36 · 12th April 2009, 11:24 PM

The horns are a little past my current DIY skill (i truely wish), but the Audio Nirvana tip is a really good one, it has opened up a new range of options for me and indicates i need to do much more research before jumping into anything. Thanks for the links and web site tips, greatly appreciated.

HareBrained · 12th April 2009, 11:38 PM

Quote:

Originally posted by Tetsuo36
The horns are a little past my current DIY skill (i truely wish), but the Audio Nirvana tip is a really good one, it has opened up a new range of options for me and indicates i need to do much more research before jumping into anything. Thanks for the links and web site tips, greatly appreciated.

It's really difficult to know when you know enough. When it comes to full range drivers, it's an obscure topic within a small hobby, and the alternatives are not going to be found at your common parts supplier. This forum is an excellent source for suppliers. I've also found that people's sigs are a great resource. Good luck.

A couple of other considerations:
Pioneer B20FU20-51FW 8" Full Range Driver
Visaton B200

8th April 2009, 04:25 PM	#1
Tetsuo36 diyAudio Member Join Date: Apr 2009	Starting Out - Fostex 127 Hi, Just finished my first audio DIY, an AMP6 from 41hz. Really nice. Now moving on to speakers as my 8ohm low sensitivity Tannoys are just not up to it. Intended to use Fostex 127 and to go the madisound bass reflex route, my DIY skills are not up to the horns just yet. It seems to be a simple introduction for me and cheap, £300 all in. The Amp6 is 4ohms so i intend to use 2 drivers, in parallel for each channel, this would be 4 speakers in total. Not sure whether it would be best to combine 2 speakers to appear as one, with parallel wiring length kept to the very minimum, or 4 seperate speakers paralleled at the binding posts? I think trying to incorporate 2 drivers in a single cabinet is a more difficult proposition. Also is a BSC required or should i just do it, allow burn in and assess later? In fact any advice/opinion would be appreciated. Alternative drivers, designs, issues etc... Thanks in advance.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
fostex 208ez and fostex ft17 h good kombo?	almightybozo	Full Range	1	24th September 2010 07:00 PM
Just starting	GrooveCat	Introductions	4	11th January 2008 03:37 PM
WTB: a pair of Visaton B200 or Fostex F108ES or Fostex FE126e or Jordan JS92S	Rafal	Swap Meet	0	10th November 2006 02:35 PM
just starting	v1d9uy	Subwoofers	6	20th December 2005 01:19 AM
starting over	trailsnail85	Car Audio	6	12th December 2005 06:20 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

8th April 2009, 05:11 PM	#2
HareBrained diyAudio Member Join Date: Mar 2009	When working with two drivers playing the same frequencies (all in this case), at some point, their separation (center-to-center) will greater than the wave length of some audible range. This can result in the two drivers being identifiable and interference effects. You should have them as close as mechanically possible. They also need to be on the same acoustic center plane. In separate cabinets, it can be physically done but in the same cabinet, it is assured. Baffle step diffraction is a function of speaker placement. When close to the wall or TV or other large planer surfaces, the amount of compensation is reduced. If you're going to put them into the room and away from other things (i.e. dedicated listening room), you'll want the full compensation (~6db). Most people have spouses and thus don't need full compensation, so 3-4db is typical. One alternative to the LR when using 2 drivers is to create a 1.5-way crossover. This is where one driver is used as the BSC and has a low pass filter set to 800-1000Hz. This is a better alignment because instead of suppressing the upper frequencies of both drivers, one driver is full range and the other contributes it full capabilities up to the LP filter. John

8th April 2009, 05:16 PM	#3
inrank diyAudio Member Join Date: Oct 2005	or use two in bipole

11th April 2009, 07:36 PM	#4
Tetsuo36 diyAudio Member Join Date: Apr 2009	Hi, my understanding (limited) of bipole is for surround sound speakers with 2 drivers directing sound to the front and back of the room. I do not think this is what i am after, i just want to create a good stereo sound. I do not have a dedicated listening room (wife/kids) so the speakers are in the corners of the room, 12" from the wall. I was seeking to use 2 drivers in parallel simply to get to the total ohms down to 4 to maximise my amps 2 x 25w output and because i could find easy to build bass reflex plans. Additionally Fostex are well thought of. Maybe i need to research more, find some 4ohm drivers etc and alternative cabinet designs? Any pointers would be good. I am very new to this. Regards, Mark.

11th April 2009, 09:33 PM	#6
AdamThorne diyAudio Member Join Date: Oct 2006 Location: Minneapolis, MN	Planet10 and his cohorts are an excellent resource when it comes to fostex speakers, if you didn't already know. Check his websites, and depart from his advice at your own peril. Tho if I had corners to load, I'd want to make a BIB my first build. Simple enough construction that one wouldn't feel too bad about discarding the box and making something else w/ the drivers, should it be necessary.

12th April 2009, 08:35 PM	#7
HareBrained diyAudio Member Join Date: Mar 2009	Tetsuo36, Have you researched getting a prebuilt cabinet? I only know of ones here in the US and would be costly to ship but there are some that would be reasonable for the Fostex drivers. I will mention that I just completed a set of computer speakers using the Mark Audio CHR-70 and I'm very impressed with them. They're an incredible value if cost is an issue but sensitivity is only marginally better then your Tannoys. They're already 4-ohms and thus only one would be needed. The Audio Nirvana drivers at http://www.commonsenseaudio.com/ would be an interesting complement to the Amp6. Lastly, consider the Fonkens over on P-10. All straight cuts and fairly simple to build. While you're there, check out the phase plugs for the Fostex drivers. As Scottmoose says, they're a must.

12th April 2009, 11:24 PM	#9
Tetsuo36 diyAudio Member Join Date: Apr 2009	The horns are a little past my current DIY skill (i truely wish), but the Audio Nirvana tip is a really good one, it has opened up a new range of options for me and indicates i need to do much more research before jumping into anything. Thanks for the links and web site tips, greatly appreciated.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)