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Re: Monacor SP-310CX build
Posted: Sat Jul 11, 2020 11:43 am
by NSNO2021
karatestu wrote: ↑Thu Jul 09, 2020 9:39 pm
That would be Simon Hickie by any chance ?
Yes it was and thanks for the reminder
Re: Monacor SP-310CX build
Posted: Sat Jul 11, 2020 5:07 pm
by Docfoster
karatestu wrote: ↑Sat Jul 11, 2020 7:29 am
Hey Doc.
Glad to see you are not going overboard with the xover. No notch filters, baffle step correction etc etc etc
If I was doing it they would be first order all the way but I have learned that the average 1" dome tweeters sound much better when using a single capacitor if the filter knee frequency is as high as possible or you use more than one tweeter to share the work and drastically reduce distortion.
At least you don't have to worry about woofer / tweeter time alignment
Tbh I only understand how to make a basic crossover! :-D
Yeah it would be good to try some 1st order crossovers. In fact it'd be an interesting bake off comparing 1st and 2nd order crossovers! Maybe I should build some external ones that would be easy to switch around...
So no attenuation on your tweeters to reduce overall load, just more of them to spread it...?
What's a filter knee frequency?
Re: Monacor SP-310CX build
Posted: Sat Jul 11, 2020 6:08 pm
by karatestu
No padding resistors on my project. I managed to get rid of the 12R I had when using only one tweeter. I then added another non identical tweeter (in series) firing up. The reduction in distortion and increase in resolution was remarkable even though the xover frequency lowered because I doubled the resistance and didn't lower the capacitor value.
I am always looking to get rid of components where possible (wonder who influenced me there ?) so at this point Itried removing the 12R padding resistor. It wasn't too bad a result but a bit on the hot side. Not knowing where to stop I added a third and fourth tweeter firing in and out. Distortion reduced and resolution improved on each addition and the tweeter level seemed to reduce to a point where things were nicely balanced.
All these tweeters are wired in series and it works a treat but I had to reduce the tweeter filter cap from 3.3uf to below 1uf (can't remember exact capacitance). Latest addition was a fifth tweeter firing to the rear. Firing tweeters in all directions and increasing the impedance seen by the amp from 8 ohms to 30 ohms brought down the level to the same same as the isobaric 12 inchers and two 5.25" mid bass.
Best sound I have witnessed in my ĺife (no shit) and I realise I have traded imaging for things that are more important to me. I'm a detail junkie at heart but at the same don't like harshness. Part of the reason I love nva.
Anyway , enough about me
Filter knee frequency is the point on the graph where the driver and filter response turns from flat to sloping down (or something like that). I rely on getting bass drivers close to walls to compensate for baffle step losses rather than putting more components in and ferking the music.
I hope you do experiment with first order and compare the two. We won't disown you if you prever the second order
Re: Monacor SP-310CX build
Posted: Sat Jul 11, 2020 10:30 pm
by Docfoster
karatestu wrote: ↑Sat Jul 11, 2020 6:08 pm
No padding resistors on my project. I managed to get rid of the 12R I had when using only one tweeter. I then added another non identical tweeter (in series) firing up. The reduction in distortion and increase in resolution was remarkable even though the xover frequency lowered because I doubled the resistance and didn't lower the capacitor value.
I am always looking to get rid of components where possible (wonder who influenced me there ?) so at this point Itried removing the 12R padding resistor. It wasn't too bad a result but a bit on the hot side. Not knowing where to stop I added a third and fourth tweeter firing in and out. Distortion reduced and resolution improved on each addition and the tweeter level seemed to reduce to a point where things were nicely balanced.
All these tweeters are wired in series and it works a treat but I had to reduce the tweeter filter cap from 3.3uf to below 1uf (can't remember exact capacitance). Latest addition was a fifth tweeter firing to the rear. Firing tweeters in all directions and increasing the impedance seen by the amp from 8 ohms to 30 ohms brought down the level to the same same as the isobaric 12 inchers and two 5.25" mid bass.
Best sound I have witnessed in my ĺife (no shit) and I realise I have traded imaging for things that are more important to me. I'm a detail junkie at heart but at the same don't like harshness. Part of the reason I love nva.
Anyway , enough about me
Filter knee frequency is the point on the graph where the driver and filter response turns from flat to sloping down (or something like that). I rely on getting bass drivers close to walls to compensate for baffle step losses rather than putting more components in and ferking the music.
I hope you do experiment with first order and compare the two. We won't disown you if you prever the second order
This site owns me now...?
Ah. Filter knee. I understand. Wasn't familiar with that term. Ta.
Some leftfield choices in your build.
I'd love to hear your speakers.
So the padding resistor was just 12R in series between the crossover and speaker?
A single 3.3uF on an 8 ohm tweeter will crossover at 6000Hz at 6dB per octave I think. 4x 8ohm tweeters would obviously take the impedance up to 32 ohms. Looks like 0.83uF would achieve the same 6000Hz crossover frequency for that, so well done your ears.
Great that you've taken your system in the direction that you wanted. Sounds like you're delighted with it.
Re: Monacor SP-310CX build
Posted: Sun Jul 12, 2020 6:08 am
by Ali Tait
Nice job there Doc. Had a pair of speakers with the same driver, would have kept them if a pair of H2 hadn’t come my way. Some details here-
http://www.audio-talk.co.uk/phpBB3/view ... it=Monacor
Re: Monacor SP-310CX build
Posted: Sun Jul 12, 2020 11:29 am
by Docfoster
Thanks Ali.
Yes! I read through that audiotalk thread a couple of times before embarking on this. In fact, that thread was crucial to my building confidence in these particular drivers and in using them as a starting point for a build. (The Monacor blurb suggests they were designed to be used in compact stage monitors, so I was initially sceptical about their hifi credentials. As its turned out, their high power handling capabilities has meant that I haven't worried about dropping the crossover frequency to the tweeter.)
I don't know Scott or Toppsy, but clearly they're in a different league, probably different sport, to me. Very professional looking in process and result! Rather than some goon hacking away at a sheet of MDF on his garden table, and then repeatedly burning his thumb with the world's shittest soldering iron.
Scott and Toppsy's cabinets are obviously more voluminous than mine, and possibly more than Monacor imply. I have Scott's designs saved somewhere. (Kind of him to make them freely available.) Maybe one day I'll build those to see how they compare to my smaller ones.
Re: Monacor SP-310CX build
Posted: Sun Jul 12, 2020 4:58 pm
by Ali Tait
Yes, Colin makes some nice cabinets. He did make one pair with the 12” Monacor drivers, never got to hear them though.
Very good drivers for the money I thought.
Re: Monacor SP-310CX build
Posted: Thu Jul 16, 2020 7:26 pm
by Docfoster
Back home.
Listening suggested -14dB on the tweeters were required.
As luck would have it, I already had the necessary resistors in my bits and bobs box to make L-pads for that.
Sounded just a tiny bit peaky.
Pushing them back about 15cm towards the rear wall has improved that.
Pretty happy with what's going on.
Re: Monacor SP-310CX build
Posted: Tue Jul 21, 2020 11:45 am
by Docfoster
I think I've now settled on around -16.3dB attenuation. (L-pad 6.8R series, 1.5R parallel).
It was a little trickier than normal as the amount of sonic overlap of woofer and tweeter between 700Hz and 930Hz made it less easy to predict how digitally reducing the overall level from 700Hz would translate into L-pad values on the tweeter alone. Once I'd narrowed it down a bit, I had to do a lot of trial and error with various resistor values until I got it right.
Anyway. Very happy now.
Final steps:
1. Get the speakers covered. Will try a self-adhesive vinyl.
2. Sell the Tannoy 295/8 drivers, and sell the Goodmans 18P drivers. Hopefully get about a grand from those sales. (I have run out of money.)
3. Plan next project!
Re: Monacor SP-310CX build
Posted: Mon Jul 27, 2020 8:16 pm
by Docfoster
Been playing around a bit with mounting and positioning.
Made some stands.
Deciding to go for maximum coupling...Thought about spikes, but felt I could do better...So screwed the base of the stands down onto those big 600mm concrete slabs, and the top plates into the bottom of the speakers.
Definitely tightened up the sound.
Decided to further attenuate the compression driver tweeter. Now up to around 18dB.
