Update for you,
I have made the baffle as suggested by are sreten, just one sheet of ply so far. It sound very promising, the midrange has returned!
I have adjustment left for both gain and crossover frequency on the plate amps too.
Next step is to add the second ply sheet and stand.
I mounted the beta 15 3" from the bottom edge of the baffle, I couldn't wait for an answer, had to seize the moment 🙂
I have a question, I don't have a router, so how large Should I make the holes on the rear baffle to avoid adversely effecting rear radiation of the drivers.
It's not the end of the world to by a cheap router if necessary, And required bit.
One option is to use wood filler to shape the rear chamber?have them
Many thanks
Ian
I have made the baffle as suggested by are sreten, just one sheet of ply so far. It sound very promising, the midrange has returned!
I have adjustment left for both gain and crossover frequency on the plate amps too.
Next step is to add the second ply sheet and stand.
I mounted the beta 15 3" from the bottom edge of the baffle, I couldn't wait for an answer, had to seize the moment 🙂
I have a question, I don't have a router, so how large Should I make the holes on the rear baffle to avoid adversely effecting rear radiation of the drivers.
It's not the end of the world to by a cheap router if necessary, And required bit.
One option is to use wood filler to shape the rear chamber?have them
Many thanks
Ian
Just to show how impatient I am.
I bought a router and bits, which one would be the most suitable. I am thinking the 45 degree, would be the easiest to make over two baffle, I think?
Would flush mounting make much difference?
And a pic of the temporary setup.
Many Thanks
Ian
I bought a router and bits, which one would be the most suitable. I am thinking the 45 degree, would be the easiest to make over two baffle, I think?
Would flush mounting make much difference?
And a pic of the temporary setup.
Many Thanks
Ian
Attachments
Flush mounting the woofer isn't necessary at all. I even question the need to chamfer the hole on the rear.
Chamfering and flush mounting would be basically helpful for the AN8, but flush mounting will be difficult to achieve. Getting the crossovers right certainly makes more of a difference than any work with the router.
What kind of crossover will you apply?
Hi,
45 degree chamfer the current 8" hole down about halfway / 1cm.
Then for the rear sheet just make the hole ~ 1.5" diameter wider
for the 8". Flush mounting is very pointless for both drivers.
FWIW use lots of contact adhesive, not wood glue to glue
the sheets together. Ridge one sheet down and one across
(a old saw blade is good for this) and let it dry properly
before mating. With any luck you'll get a constrained
damping layer, with much more damping than PVA.
Experimenting on some scrap might be a good idea.
rgds, sreten.
Spraying the back with bitumen gutter sealer / car underseal spray
would also add some unconstrained damping to the arrangement.
You can also do the front, if near matt black is acceptable.
45 degree chamfer the current 8" hole down about halfway / 1cm.
Then for the rear sheet just make the hole ~ 1.5" diameter wider
for the 8". Flush mounting is very pointless for both drivers.
FWIW use lots of contact adhesive, not wood glue to glue
the sheets together. Ridge one sheet down and one across
(a old saw blade is good for this) and let it dry properly
before mating. With any luck you'll get a constrained
damping layer, with much more damping than PVA.
Experimenting on some scrap might be a good idea.
rgds, sreten.
Spraying the back with bitumen gutter sealer / car underseal spray
would also add some unconstrained damping to the arrangement.
You can also do the front, if near matt black is acceptable.
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Looks good. This is the way to go IMO regarding an easy all OB setup. You can roll drivers on top (Betsy, Fostex 207e, etc.) and enjoy.
Zilla
Zilla
Here is a quick update, In between posts i have been busy.
Before reading your suggestions Sreten, I had already glued the second baffle, 45 degree chamfered both holes for both drivers, mounted them on a base with some 2x2 to add rigidity screwed and glued.
I tried flush mounting on some scrap, I don't have the skills yet, made a mess.
Just couldn't miss the opportunity of having my 18 month old daughter and wife out of the house for the day.
Left to do is,
1 Rubber damp the rear of the baffle, glued with silicon.
2 Cover the front of the baffle with a cosmetically friedney fabric, maybe faux suede. The bitumen sealer would not be acceptable to my wife, the smell too 🙂
3 Crossover for the an8
Rudolf, I will apply any crossover ideas you have, the current cap is a mundorf 150Uf cap bypassed with a .002 auricap to the AN8, the plate amps have both gain and freq adjustment left to play with.
Any thoughts on decoupling the drivers with rubber washers etc, is this worth doing?
And round over the edges, will this be necessary or worth the effort? I have a new toy to play with 😉
Over all the sound is improved, and they intrude into the room a lot less.
Many thanks
Ian
Before reading your suggestions Sreten, I had already glued the second baffle, 45 degree chamfered both holes for both drivers, mounted them on a base with some 2x2 to add rigidity screwed and glued.
I tried flush mounting on some scrap, I don't have the skills yet, made a mess.
Just couldn't miss the opportunity of having my 18 month old daughter and wife out of the house for the day.
Left to do is,
1 Rubber damp the rear of the baffle, glued with silicon.
2 Cover the front of the baffle with a cosmetically friedney fabric, maybe faux suede. The bitumen sealer would not be acceptable to my wife, the smell too 🙂
3 Crossover for the an8
Rudolf, I will apply any crossover ideas you have, the current cap is a mundorf 150Uf cap bypassed with a .002 auricap to the AN8, the plate amps have both gain and freq adjustment left to play with.
Any thoughts on decoupling the drivers with rubber washers etc, is this worth doing?
And round over the edges, will this be necessary or worth the effort? I have a new toy to play with 😉
Over all the sound is improved, and they intrude into the room a lot less.
Many thanks
Ian
I would like some input on the crossover please?
And any thoughts on decoupling the drivers with rubber washers etc, is this worth doing?
And round over the edges, will this be necessary or worth the effort?
The charcoal suedette is ordered, wife thinks it will look cool!
Many Thanks
Ian
And any thoughts on decoupling the drivers with rubber washers etc, is this worth doing?
And round over the edges, will this be necessary or worth the effort?
The charcoal suedette is ordered, wife thinks it will look cool!
Many Thanks
Ian
I see three different strategies:
A fully passive solution. I can post the Xover parts values if interested:
An externally hosted image should be here but it was not working when we last tested it.
This has a bass boost around 70 Hz which comes free with the filter configuration.
A full active solution that tries (somewhat) to follow the passive one above:
An externally hosted image should be here but it was not working when we last tested it.
You will need the bass boost of your plate amp to give this any "ummmph" 🙂
And a full active alternative:
An externally hosted image should be here but it was not working when we last tested it.
Now the Beta is boosted 8 dB entirely. Be aware that this solution will run out of Xmax rather soon.
SPL values are for 10W listened from 3 m distance at 10° off axis to the "short" side of the baffle.
The filters are separate for each driver, yes:
Fullrange driver and woofer are in phase.
This is just a proposal. You can change any value by up to 20%, depending on what you have at home or can get. We would do a new sim when you have sorted it out.
Don't become too demanding with the big coils.They don't need to be air coils. Ferrite or iron core would be fine too.
You don't need any more filters, if frequencies above 2 kHz of the AN had worked for you with your 150 µF highpass. Dipoles don't need BSC. Above filters will achieve the response as shown in the graph.
Rudolf
Fullrange driver and woofer are in phase.
This is just a proposal. You can change any value by up to 20%, depending on what you have at home or can get. We would do a new sim when you have sorted it out.
Don't become too demanding with the big coils.They don't need to be air coils. Ferrite or iron core would be fine too.
You don't need any more filters, if frequencies above 2 kHz of the AN had worked for you with your 150 µF highpass. Dipoles don't need BSC. Above filters will achieve the response as shown in the graph.
Rudolf
How much is the cut-out for the AN8 chamfered? Sorry, but that single shot doesn't tell me much about it. Looks like it should be wider.
What will you do to make that tiny baseplate stick to that floor? I believe you don't want spikes. But you probably need something to press the base plate firmer to the ground.
What will you do to make that tiny baseplate stick to that floor? I believe you don't want spikes. But you probably need something to press the base plate firmer to the ground.
I'm going to recommend that you put some sides on the rear from the floor
to halfway up, maybe 12" deep or so. This will give you a little more loading
for the bottom end.
😎
to halfway up, maybe 12" deep or so. This will give you a little more loading
for the bottom end.
😎
Thanks for the crossover design Rudolf, very king of you.
I'll start tracking down some parts at the weekend.
Thank you Nelson for the suggestion, but the flat baffle stays. My wife much prefers them against the wall when not in use.
Did you have any thoughts on rounding the baffle edges or decoupling the drivers?
Many thanks
Ian
I'll start tracking down some parts at the weekend.
Thank you Nelson for the suggestion, but the flat baffle stays. My wife much prefers them against the wall when not in use.
Did you have any thoughts on rounding the baffle edges or decoupling the drivers?
Many thanks
Ian
Hello Ian,
I assume that your largest router bit does a 2,5 cm radius. The baffle edge radius must be at least a quarter wavelength to be of any use. This results in 3,4 kHz as the lowest affected frequency. At 3,4 kHz your AN8 is quite directive already. Only a small fraction of the sound will reach the baffle edges. In your case I don't see any acoustic advantage in rounding the edges.
Decoupling the drivers from what? Is your baffle vibrating in itself, or is it rocking as a whole? Don't we need to know the disease before we can talk about the cure? 😉
Rudolf
Hi,
http://www.quarter-wave.com/OBs/OB_Design.pdf
Take a look at the crossover arrangements here.
Your concern is the treble section and melding
it to the active bass section seamlessly.
rgds, sreten.
http://www.quarter-wave.com/OBs/OB_Design.pdf
Take a look at the crossover arrangements here.
Your concern is the treble section and melding
it to the active bass section seamlessly.
rgds, sreten.
A Little update
Hi All,
I have damped the rear with heavy 8mm rubber sheet, added floor spikes and covered with grey felt. They sound much more detailed and soundstage better. I haven't got hold of the crossover parts yet, next on the list.
Unfortunately, my cats have been using them as scratchers so might have to cover with another material. It looks worse than it is in the photos.
Cheers
Ian
Hi All,
I have damped the rear with heavy 8mm rubber sheet, added floor spikes and covered with grey felt. They sound much more detailed and soundstage better. I haven't got hold of the crossover parts yet, next on the list.
Unfortunately, my cats have been using them as scratchers so might have to cover with another material. It looks worse than it is in the photos.
Cheers
Ian
Attachments
The rear wings Nelson suggested could simply be the depth of the base plate and taper down as they go up to the half way point. They have the added advantage of transferring some vibration from the woofer away from the baffle to the floor and also take some stress off the screws holding the baffle upright. Great job by the way..
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HI All,
Had to abandon this project as I ran out of options,time and money!
We have moved house and I am ready to get going again.
I have a Umik mic, two amp pcbs, TDA7492 for Bass and TPA31162 for the rest.
Mini DSP 2x4 on route.
Buying the 2 way advanced plug-in, unless anyone says otherwise?
Can you guys explain the crossover details Rudolf kindly suggested to me in Mini DSP terms or give me some tips?
Many Thanks
Ian
Hi Again,
I now have the 2 way advanced plug-in installed.
I have a TDA7498 up and running, 35volts dc, should get me started.
Mini DSP should be here any day.
I'm planning to start with the following Mini DSP config, please any advice welcome?
Low freq LR4 100Hz boost 4DB, with the intention to increase to the suggested 8DB.
High freq LR2 100Hz.
I am unsure what the baffle step config should be, can anyone help?
Also the TDA7498 & TPA31162 boards have input gain jumpers, currently in default positions.
Would upping the gain on the TDA7498 help with matching sensitivity or power output?
Any suggestions, or leave them be?
Many thanks
Ian
I now have the 2 way advanced plug-in installed.
I have a TDA7498 up and running, 35volts dc, should get me started.
Mini DSP should be here any day.
I'm planning to start with the following Mini DSP config, please any advice welcome?
Low freq LR4 100Hz boost 4DB, with the intention to increase to the suggested 8DB.
High freq LR2 100Hz.
I am unsure what the baffle step config should be, can anyone help?
Also the TDA7498 & TPA31162 boards have input gain jumpers, currently in default positions.
Would upping the gain on the TDA7498 help with matching sensitivity or power output?
Any suggestions, or leave them be?
Many thanks
Ian
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