FE108E BLH question

[rockthebox]

Hi folks,

I've decided to take the plunge and build the Fostex BLH with FE108E sigma's.. all the talk on this forum convinced me it was the way to go.

The plan at the moment is to couple them with a REL R205 sub as I've read that the bass performance although very accurate, doesn't go massively low and I want to fill out the bottom end.

I'm planning on driving the FE108's from a pair of Hypex class D power amps.

What I am considering is putting a High Pass active filter in front of the power amps to take the low frequency elements that the REL will be handling away from the horns.

My questions are:

1) Is this a good idea? Will this help the Fostex driver and give better sound quality?

2) If so, what is the recommended cut off frequence and order of the filter.

I'm currently thinking about putting a 2nd order HP LR filter at 80Hz.

Thanks in advance for your help. I can't wait to get them built. Will keep you updated if people are interested.

Cheers,

 

[Andrewbee]

Is this a good idea? Will this help the Fostex driver and give better sound quality?

In theory yes, but in reality "maybe". In my experience the will be a definate loss of cohesion when filtering the fullrange and adding a sub. I personally have never had a seamless transition but ymmv.

If so, what is the recommended cut off frequence and order of the filter.

You need to experiment, I would suggest cutting off @ 80 - 90hz @ ~24db/ as a start.

If you need bass, the Nagaoka Swan will do it for you with the same driver.

Sorry that I could not be more helpful.

Andrew

 

[chrisb]

Hi folks,

I've decided to take the plunge and build the Fostex BLH with FE108E sigma's.. all the talk on this forum convinced me it was the way to go.

The plan at the moment is to couple them with a REL R205 sub as I've read that the bass performance although very accurate, doesn't go massively low and I want to fill out the bottom end.

I'm planning on driving the FE108's from a pair of Hypex class D power amps.

What I am considering is putting a High Pass active filter in front of the power amps to take the low frequency elements that the REL will be handling away from the horns.

My questions are:

1) Is this a good idea? Will this help the Fostex driver and give better sound quality?

2) If so, what is the recommended cut off frequence and order of the filter.

I'm currently thinking about putting a 2nd order HP LR filter at 80Hz.

Thanks in advance for your help. I can't wait to get them built. Will keep you updated if people are interested.

Cheers,

I can't speak to the questions regarding most suitable XO frequency and slopes for your particular application (regardless of others pet favorite formulas, experimentation in your system will provide the answers) .

However, I can attest that having heard the driver in question in quite a few enclosure designs, Fostex and otherwise, by far the best sounding was Scott Lindgren's Aiko (originally intended for a Lyeco 4", but for me the Fostex kicked it to the curb)

http://homepage.mac.com/tlinespeakers/FH/download/Aiko-LY401F-NDH-map-010407.pdf

 

[rockthebox]

Hi guys,

Many thanks for your replies.

I'll take your advice and start with an Xover 80-90 Hz 24db/oct and experiment from there.

I already have a REL sub, so will try that for a start as well and see how well I can get it integrated.

Thanks also for passing on the Scott Lindgren design. That does look like a nice design. I'm wondering just how much better it is than the Fostex plan? What was your impression of how different the speaker sounded?

Cheers,

jason

 

[rockthebox]

Another quick question if that's OK..

I've ordered the Fostex drives and they should be with me soon. Is it OK to break in the drivers with program material before they are put in the cabinets, or should they really be broken in when in the boxes?

I know I'm going to be mad keen to listen to them and start the fine tuning when the boxes are finishes. So it would be good to start the break in period now. However is having the real loading an important part of break in?

Cheers,

jason

 

[Scottmoose]

Better done out of the final cabinet, or you'll spend the best part of a year or more getting the suspension loosened up (horns & their subsets tend to control driver excursion better than other types of enclosure).

Re cabinets -I'm not a fan of the Fostex box; it isn't really one of their best & has some cuppy colourations across the midband. Chris & DaveP10 have a lot of experience with the 108, so I suggest you be guided by them WRT cabinets for it.

 

[rockthebox]

Thanks for the info..

I've been studying the Scott Lindgren plans and have a cutting plan which I'm going to take to the local timber supplier to get a quote for supply of the wood cut to size. (will go for 15mm birch ply)

I think it's actually going to be easier to construct than the Fostex one as it's all right angles.

I'll keep the group updated with posts and pictures.

Cheers,

jason

 

[Scottmoose]

It should be an easy enough build -I designed it, & the larger cabinets in the range, with that in mind. Complex angles can be off-putting to a lot of people, especially if they're not over-confident in their woodworking, so this style of design tends to encourage them to have a go.

 

[rockthebox]

I'm definately feeling like giving it a go

Thanks for sharing your design. It looks great.

jason

 

[Jamesuk1]

Scott's design

Hi,I for one can vouch for scotts Designs.I built my Chilli Changs a few weeks back and to be honest i cant stop listening to them.They have a very involving sound that draws you in to the music.I used to read while listening to my music.
Not anymore !!!

 

[rockthebox]

Hi James,

Very nice work on the horns.. just wondering how you find the positioning of the drive units to ear height? I think they will be a little low for my sitting position. Had a quick scan for suitable speaker stands but don't see anything obvious out there with the right height (~250mm) and a small enough top plate.

I have drawn out a cut plan for the local timber merchant, they will be cutting them tomorrow, so should have them soon Have plumped for 15mm oak veneered MDF.

Cheers,

jason

 

[Scottmoose]

You might want to add some internal braces then as MDF isn't all that great for this application. As for the driver height, you could install outriggers at the front for increased stability, and also to allow you to tilt them back slightly if you feel the need.

 

[Jamesuk1]

HORNS

Thanks Jason.i actualy measured my ear height whilst seated.I then built the plynths to raise the drivers up a tad.
....regards... james
Ps youll need to get some iron on veneer for the edges too..

 

[rockthebox]

Progress report

Hi folks,

Thought I'd post an update to show progress on the speakers. Very pleased with the way they are coming together. Nice design scott, thanks.

One small problem with the plans - top/bottom are given as 300mm in length. The correct dimension should be 15mm less than that as the back is full height of speakers. Just in case anyone else is planning on building a pair.

Cheers,

jason

 

[rockthebox]

PS

A long story, but ended with 15mm marine ply.

Planning on painting them. (the girlfriend has plans!)

Cheers,

jason

 

[Scottmoose]

You're welcome. Hope you like them.

 

[rockthebox]

Size of round baffle

I'm wondering how you chose the size of the round baffle that the driver is bolted to? I've cut one at ~210mm diameter as this is the biggest my hole cutting tool goes to.

I'm guessing the purpose of this is to help imaging?

Cheers,

jason

 

[chrisb]

Jason - if you plan on painting the inside of the mouths, unless there's a special pattern involved, you'll probably find it a lot easier to finish the visible parts before assembly. Trace the panels locations with masking tape to provide an unfinished gluing surface.

FWIW, when we calculate the dimensions of supra-baffles (whether square, round or elliptical) we are trying to bridge the frequency range between the main cabinet baffle's step loss and the horn action lift. When I built the Aikos, I tried an ellipse, at 273 x 440mm - it sounded wonderful, and looked pretty cool too.

A large radius edge ( I used an 1 1/2" handrail profile router bit) helps reduce diffraction effects on round/curved baffle shapes, as does a 45 deg chamfer on rectangular or square baffles.

 

[rockthebox]

Cheers Chris.. so I guess my round supra-baffle is a tad on the small side.

I've got plenty of wood left over, so will have a bash at the weekend and see how my jig saw skills hold up. I was using a hole cutter to keep things symmetrical

I'd been considering painting before sticking the boxes together, think I'm probably going to risk painting afterwards. I think there is enough room. I'll probably live to regret that decision though!

I'm hoping to get to listen to the (unpainted) boxes by this weekend. Looking forward to it.

 

[chrisb]

Cheers Chris.. so I guess my round supra-baffle is a tad on the small side.

I've got plenty of wood left over, so will have a bash at the weekend and see how my jig saw skills hold up. I was using a hole cutter to keep things symmetrical

I'd been considering painting before sticking the boxes together, think I'm probably going to risk painting afterwards. I think there is enough room. I'll probably live to regret that decision though!

I'm hoping to get to listen to the (unpainted) boxes by this weekend. Looking forward to it.

I don't think there's enough hard science on the subject of "supra-baffles to categorically pontificate that any one dimension, parametric formula or cross sectional profile is "the best way".

So, in other words, by all means use the baffle you've already cut, but if you can make allowances on your install for experimentation with others.

Most importantly, when you sit down to listen on the weekend, relax and - trust your emotional reaction.