Advice? Single full range open baffle design?

[RockRolley]

I just got my first ‘flea watt’ valve amp and understand I need efficient, sensitive speakers to go with the amp. I’ve seen some Richard Allan full range drivers around and am considering having an open baffle design made and I’d love advice on baffle dimensions to get the most out of all frequencies, timber type and treatment that can help or hinder acoustics and where on the baffle to place the driver. I’ve learned about myself that I know nothing about crossovers or even finding the right crossover for a project so inevitably get tripped before the finish line with multiple driver DIY designs. Hence I love the plug and play approach with full range drivers. I know a woodworker who can handle the timber side, and if the rest is just mounting a single driver to plug and play, I’m home and hosed. I only paid $250 for a McChanson amp from an SNA member, so I’m only looking at accessibly priced drivers and the Richard Allans tick that box and seem to get praised although they don’t seem to be widely discussed. Open to other brands though. Please don’t recommend adding a tweeter or a sub unless you can direct me to available crossovers to match-as said, I’ll be lost otherwise. There are some 8 inch drivers available but I could hold out for 10 or 12. If you have designs for suitable boxed enclosures I’d also be interested to hear. Thanks SNA brains trust!!  See below some examples of simple designs I like. Not my pics FYI 

Edited February 27, 2022 by RockRolley
Fix typos

[mwhouston]

Fostex 8” are a good and inexpensive start. Open baffle won’t provide a lot of bass but if your fav music is more about acoustic instruments in simple open settings these should be fine. Make and female jazz singers will sound breathy and in room. Acoustic guitar, cello, piano and violin will also shine.  

[mwhouston]

https://www.madisoundspeakerstore.com/approx-8-fullrange/fostex-fe206nv-8-full-range/
 

[RockRolley]

Thanks for your feedback I’ll look into it. Are these good with low watt amps to your knowledge? 

[mwhouston]

16 minutes ago, RockRolley said:

Thanks for your feedback I’ll look into it. Are these good with low watt amps to your knowledge? 

How many watts RMS. And yes. 

[mwhouston]

No Xover required. 

[mwhouston]

96db efficient. Loud for even 1W. 

[mwhouston]

http://retro-thermionic.blogspot.com/2009/11/fostex-fe206e-back-loaded-horn.html
 

https://retro-thermionic.blogspot.com/2012/09/fostex-fe206en-drivers-in-dual-bass.html

 

 

[davewantsmoore]

 

59 minutes ago, RockRolley said:

timber type and treatment that can help or hinder acoustics

Anything non-resonant will be fine.   MDF, ply, etc. of 3/4 inch or more.

 

59 minutes ago, RockRolley said:

and where on the baffle to place the driver.

Centred, at ear level.

 

59 minutes ago, RockRolley said:

I’d love advice on baffle dimensions to get the most out of all frequencies

 

Open baffle speakers can have the correct amount of frequency response flatness (including the right amount of bass) if designed correctly.

 

When you put a speaker on an open baffle.... it will not have enough bass, and so things need to be done to correct the amount of bass... and these things all work in combination with each others.

 

1.   The narrower the baffle the more bass goes missing (ie. wider baffle will give you more bass).

 

2.   Properties of the speaker driver itself may place a peak in the bass ..... giving you back (some of) the missing bass

 

3.   Some sort of correction filter to the signal (like a crossover filter does) to push the mid and treble down (ie. bring the bass level up).   This could also be using an amplifier which has a peak in the bass.

 

 

You are always doing #2.... how much the speaker driver is helping or hindering the bass level depends on the driver.

 

Getting the right amount of bass can be hard using number 1 alone (ie. using a wide baffle) .... but that depends on #2 also (if you drive rhas a big peak in the bass, then maybe a "not crazy big" baffle will be enough to get the right bass level.

 

 

"Old school" open baffle design does not use #3 ... and relies on picking #1 to match with #2 ..... but as mentioned, it cannot always provide enough bass.

 

"Modern" open baffle design is very different....  it uses high performance drivers (which typically don't have any peak in the bass). whcih means the bass level is even more compromised....   It uses baffles which are as narrow as possible  (which makes the bass level even more compromised) ..... and then relies on #3 to make the speaker response flat.    It might sound silly, but there's a lot of advantages to that approach (which are a bit technical).

 

 

That's a very long way around to saying that if you are set on a driver ... and will not use any correction filter .... then all you have to play with is the baffle width.

 

If you don't know how to calculate a baffle size, then you'll need to "experiment".

 

Get a large sheet of cheap wood (ply or MDF, 18mm+) .... make the panels big enough to get the drivers up near to ear level (or tilt them back a small amoutn so you don't have to make them so high) .... and start with them very wide (say 1.2m wide), and progressively cut the sides narrower untli too much bass is gone.   Then re-make the final set with the finish you want.

 

 

 

 

 

 

[RockRolley]

These just came up on SNA: any thoughts on suitability for this type of project? Also begs the question whether these more vintage drivers are a good bet or if brands offering new options like the Fostex ones are as good or better than the vintage options like warfedale, Richard Allan, Celestion, Goodmans etc.

Edited February 27, 2022 by RockRolley

[RockRolley]

56 minutes ago, mwhouston said:

How many watts RMS. And yes. 

I believe just 2W 

this is the unit. PS. I don’t have it yet, a friend in Sydney picked it up for me and I’ll grab it whenever we catch up 

 

[mwhouston]

5 minutes ago, RockRolley said:

I believe just 2W 

this is the unit. PS. I don’t have it yet, a friend in Sydney picked it up for me and I’ll grab it whenever we catch up 

 

If the tubes are as aged as they may look you may not get 2W unless you test for at least emissions. 

[RockRolley]

1 hour ago, mwhouston said:

http://retro-thermionic.blogspot.com/2009/11/fostex-fe206e-back-loaded-horn.html
 

https://retro-thermionic.blogspot.com/2012/09/fostex-fe206en-drivers-in-dual-bass.html

 

 

Nice. Did you hang onto these speakers? 

[Nada]

1 hour ago, RockRolley said:

I just got my first ‘flea watt’ valve amp and understand I need efficient, sensitive speakers to go with the amp.

 

This is a fun quick project.  How did you get here?

 

What music do you like to listen to? 

How loud?

Room size.

Have you heard any full range drivers? 

[Blood_Red_Bird]

2 hours ago, mwhouston said:

https://www.madisoundspeakerstore.com/approx-8-fullrange/fostex-fe206nv-8-full-range/
 

Look for a driver with a higher "qt " spec if you can,

something above 0.5 at least will better suit an open baffle

[davewantsmoore]

3 hours ago, RockRolley said:

any thoughts on suitability for this type of project?

 

Any driver can be suitable.... depending on the permutations of 1/2/3 in my post above.

 

This one has a moderate bass boost, which could help..... but it performs no good above about 3khz.    The real (potential) problem is what condition the driver is in after 60 years.... without measuring them, and knowing they are similar to original spec, then it's a bit of a lottery.

 

3 hours ago, RockRolley said:

Also begs the question whether these more vintage drivers are a good bet

In general I would say no.... there are modern drivers that are much better, and that's before considering that the old driver might be way out of spec.

 

3 hours ago, RockRolley said:

2W

How loud do you want this speaker to play?    You will need a very efficient speaker if you want to go above modest levels.

[RockRolley]

4 hours ago, davewantsmoore said:

 

Anything non-resonant will be fine.   MDF, ply, etc. of 3/4 inch or more.

 

Centred, at ear level.

 

 

Open baffle speakers can have the correct amount of frequency response flatness (including the right amount of bass) if designed correctly.

 

When you put a speaker on an open baffle.... it will not have enough bass, and so things need to be done to correct the amount of bass... and these things all work in combination with each others.

 

1.   The narrower the baffle the more bass goes missing (ie. wider baffle will give you more bass).

 

2.   Properties of the speaker driver itself may place a peak in the bass ..... giving you back (some of) the missing bass

 

3.   Some sort of correction filter to the signal (like a crossover filter does) to push the mid and treble down (ie. bring the bass level up).   This could also be using an amplifier which has a peak in the bass.

 

 

You are always doing #2.... how much the speaker driver is helping or hindering the bass level depends on the driver.

 

Getting the right amount of bass can be hard using number 1 alone (ie. using a wide baffle) .... but that depends on #2 also (if you drive rhas a big peak in the bass, then maybe a "not crazy big" baffle will be enough to get the right bass level.

 

 

"Old school" open baffle design does not use #3 ... and relies on picking #1 to match with #2 ..... but as mentioned, it cannot always provide enough bass.

 

"Modern" open baffle design is very different....  it uses high performance drivers (which typically don't have any peak in the bass). whcih means the bass level is even more compromised....   It uses baffles which are as narrow as possible  (which makes the bass level even more compromised) ..... and then relies on #3 to make the speaker response flat.    It might sound silly, but there's a lot of advantages to that approach (which are a bit technical).

 

 

That's a very long way around to saying that if you are set on a driver ... and will not use any correction filter .... then all you have to play with is the baffle width.

 

If you don't know how to calculate a baffle size, then you'll need to "experiment".

 

Get a large sheet of cheap wood (ply or MDF, 18mm+) .... make the panels big enough to get the drivers up near to ear level (or tilt them back a small amoutn so you don't have to make them so high) .... and start with them very wide (say 1.2m wide), and progressively cut the sides narrower untli too much bass is gone.   Then re-make the final set with the finish you want.

 

 

 

 

 

 

Thanks so much for such a comprehensive response. All excellent suggestions. I like the sound of trying with a cheap baffle before committing to a nicer piece of wood. I must confess that aesthetics are very important to me and I foresee that I'll either get a very nice veneered ply or even solid wood for the final product. Regarding frequency correction, as mentioned, I'm willing to go beyond just the baffle and driver if the other items are easily accessible and easily employed by a novice. I can solder in a beginner type way but that's about the extent of my electronics skills. When you say the driver should be centred, do you mean bang in the middle length and width, or just centred width wise? A few examples I've seen play with off centred... is that a bad way of designing them? Another thing is that (as well as CD and vinyl) I'll be using roon which has (and I'm a novice with this too) DSP which I understand means you can eq to certain spaces. Maybe I could flatten the response with DSP

 

 

[RockRolley]

3 hours ago, Nada said:

 

This is a fun quick project.  How did you get here?

 

What music do you like to listen to? 

How loud?

Room size.

Have you heard any full range drivers? 

Thanks for asking: I was chatting with another member who has a McChanson paired with full range drivers although his McChanson is closer to 6 watts as opposed to my supposed 2 watts. Essentially I saw the one I bought come up for $250 and couldn't pass it up. I have a couple of Radford tube amps and just love valves so I thought it could be a fun way of playing with one of my smaller rooms at home. I can't measure the spaces right now, but wed be talking a small to medium sized room. Truth is some of the music I listen to, I understand, won't suit this gear. Like 80's metal... but I also listen to a lot of 60's and 70's rock, beach boys, beatles, Pink Floyd as well as acoustic guitar based music, Dire Straits, a very little jazz etc. On my Radford STA15 I rarely drive it more than quarter volume and never really to half, but I'd say if I'm by myself I'd listen at levels that you couldn't comfortably have a conversation over. I got a pair of what were supposed to be Richard Allan CG8T in some small enclosures. Turned out to be mismatched, one was a magnavox-same specs. Either way, I was quite impressed by the range of frequencies from such small drivers. I also really enjoyed the timbre of them.

[davewantsmoore]

23 minutes ago, RockRolley said:

aesthetics are very important to me

... to most people as well, I assume  

 

23 minutes ago, RockRolley said:

and I foresee that I'll either get a very nice veneered ply or even solid wood for the final product.

Yep.   Just go with some cheap ply/mdf for the prototype.

 

Solid/real wood is of no benefit (but will be fine) .... you could go for some sort of pre-venered plywood/mdf, and get oak veneer. 

 

23 minutes ago, RockRolley said:

When you say the driver should be centred, do you mean bang in the middle length and width, or just centred width wise?

Just width.   Height wise, it doesn't matter a lot, but needs to be pointing towards you.... so you could go with something like a ~80cm high baffle, with a small amount of tilt... or whatever.

 

23 minutes ago, RockRolley said:

A few examples I've seen play with off centred... is that a bad way of designing them?

No.    You can do that, but the devil is in the detail.   If unsure, centred.

 

23 minutes ago, RockRolley said:

Another thing is that (as well as CD and vinyl) I'll be using roon which has (and I'm a novice with this too) DSP which I understand means you can eq to certain spaces. Maybe I could flatten the response with DSP

Yes, altering the signal before the amplifiers is ideal ..... but this will leave your other sources uncorrected, which will be a problem.    Also 2w is going to make the available volume before distortion very limited.

Edited February 27, 2022 by davewantsmoore

[davewantsmoore]

12 minutes ago, RockRolley said:

some of the music I listen to, I understand, won't suit this gear

A well performing speaker will play any type of music properly.... and just about any type of music will make a badly performing speaker sound bad.

 

...   but almost all speakers are going to be severely limited by 2w.

[Nada]

1 hour ago, RockRolley said:

some of the music I listen to, I understand, won't suit this gear.

 

You just might develop a love for acoustic ensembles with the new setup. Solo guitar, baroque ensembles, vocals and piano could be amazing.

 

I wonder if a 2W tube amp made for speakers might double as a headamp for low impedance power hungry headphones?

[Full Range]

I built a set for my son in law a few years ago 

My preference is larger diameter drivers 

However an active subwoofer would be beneficial if you play music with lots of bass 

 

Below is the build thread 

 

Edited February 27, 2022 by Full Range

[crtexcnndrm99]

If you’re not committed entirely to the OB design (although it could work on such a baffle, a helper woofer would definitely be needed), the Beyma 15” 15xa38nd coaxial driver I’ve been using for over a year has been excellent driven by as little as 2W and continues to improve. 
 

id recommend a sealed enclosure. I’d think making a box look aesthetically pleasing is easier than trying to make an open baffle look like furniture? I’ve struggled with that one, trying to think of how I’d make an OB cross into furniture territory. 
 

Im not the only one who has used this driver for a simple high efficiency build, so if you would like more info, just shout! 

[RockRolley]

1 hour ago, Nada said:

 

You just might develop a love for acoustic ensembles with the new setup. Solo guitar, baroque ensembles, vocals and piano could be amazing.

 

I wonder if a 2W tube amp made for speakers might double as a headamp for low impedance power hungry headphones?

Could possibly do, although, I don't have much of a headphone setup. On the ad for these, the seller said he commissioned it for his active setup. I would have thought a preamp, i.e. unpowered, would be used for active speakers, although I'm not certain of it. I'm sure I'll start exploring headphones at some point. Any secific types you think may suit this amp?

[RockRolley]

5 minutes ago, crtexcnndrm99 said:

a helper woofer would definitely be needed

Thanks for your input. Ahhh, well, I suppose that would bring me into needing a crossover, which, as mentioned is where I may find I'm lost..

6 minutes ago, crtexcnndrm99 said:

Beyma 15” 15xa38nd coaxial driver

They look great, but would cost more than the amp, which i'm trying to avoid ATM. If the flea watt amp and full range works well for me, I'll certainly keep it in mind for an upgrade down the track, so, thanks

9 minutes ago, crtexcnndrm99 said:

id recommend a sealed enclosure. I’d think making a box look aesthetically pleasing is easier than trying to make an open baffle look like furniture?

I'm definitely up for having a sealed enclosure made, although, I'd love to find out what the optimal dimensions etc. would be. At this stage, I have some 8 inch drivers to play with. I was actually considering doing both sealed and open Baffle and playing around for fun

11 minutes ago, crtexcnndrm99 said:

Im not the only one who has used this driver for a simple high efficiency build, so if you would like more info, just shout! 

Consider me shouting!  although, at this stage, more focussed on generic full range advice as I'm not likely to get a hold of one of those drivers just yet.