MY own OB speaker project

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ed
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#46 Re: MY own OB speaker project

Post by ed »

Toppsy wrote: Fri Nov 03, 2017 5:49 pm
Well now Ed as it happens last that Scott was over he did comment that he thought you would like these. You are most welcome to pop over to have a listen anytime that is convenient or wait till the next Owston.
very kind, I will make a point of asking next time I get a red rose visa stamp in my passport....but seriously I have to take the troops to the airport sometime in December so may ask you if its convenient then.....

I was intrigued by the 100-500hz area cos the celestion/monacor is no good there and after all my horrid experiences with large drivers coping with that area I'm sceptical to say the least....
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#47 Re: MY own OB speaker project

Post by IslandPink »

I'd have to say I share Ed's concerns too - after the time it took me to find drivers that could do midrange and dynamics that would keep up with compression driver or ribbon tweeter. I am happy with a 3-way with the FX120's and there is little else I've heard short of expensive stuff like the AER's that would do what they do. Anyway, keen to hear what the 'team' think today.
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#48 Re: MY own OB speaker project

Post by simon »

Ditto. We all like a good OB :-)
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#49 Re: MY own OB speaker project

Post by Nick »

Ok, so a good time was had by all. First off the OB's with the Monacore coax unit was in use first. Initial problems we heard was lack of bass and midrange a bit confused. with some thinking (and beer) we solved both of these by adding some side wings to the lower bass driver (pair of LP's propped each side. The muddle was I think due to it being too close to the rear wall so the reflections from the rear wall were getting back out the mid range driver. Pulling it out another foot solved that. After that they sounded great, we spent the evening listening and I must say they work very well indeed very very revealing, we heard lots of stuff down in the mix that had always been there, but was just a sound before, with these speakers it became instruments making that sound. For me, not so good driven by the 300b's, most of the listening was driven by the lda mosfets, and the clarity of both seemed to be a good match. We did try altering the xover point to give a bit more from the coax horn tweeter, but started to hear the same problem that I heard when we had them at Davids. But as they were they work great. We did try adding a pair of super tweeters, and that did make it even better, but it was only the icing on the cake, without them you would not be missing much.

The next morning, we replaced the monocor unit with the horn and compression driver. Removed the passive xover and drove the bass units with the LDA mosfets and the horm with the MF SS amp. Crossover done by the mini DSP. To my ears that also worked very nicely indeed. The bass of the OB's probably better than the passive sound, and after dialling the horn down about 13dB (though we didn't know how the two amps gain differed). The initial crossover point was probably about right, low pass 48dB/Octave LR, same for the horn, but a high pass. Trying to bring the xover point down, and trying a slope that could be made with a passive xover was less successful. Letting the horn work below 1k5 brought out a horn shout that was unacceptable, and asking the bass units to work much about 1k5 started to allow the cone breakup of the bass units to be heard. But with the above xover, it was very very acceptable, and I would recommend it to anyone. Not certain though if the same could be done with a passive xover, don’t think you could do it without hearing a problem from one or both of the drivers. But as a speaker to use with a DSP xover and a pair of amps, I think would be very successful.

Hopefully the time was helpful to Colin, and thanks for the beer and food.
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#50 Re: MY own OB speaker project

Post by IslandPink »

Good effort !
So remind me, what's the bass unit for this ?
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#51 Re: MY own OB speaker project

Post by Toppsy »

OK I'll kick off of what I can remember of the weekend meet, hopefully Andrew, Nick and Chris will contribute with comments when they have the time.
Andrew arrived the Friday evening and we fired up the 3-way OB's with my 300B SET's. His initial reaction was not as positive as I hoped. He thought the bass was still lacking in the bottom registers so I swapped out the 39uF for a 22+10uf paralleled to give us 32uF, since I didn't have a 33uF next value down single cap. Andrew thought this was too much so I paralleled to this a 2.7uF and to Andrew's ears that sounded a lot better so we stuck with this set up for night and played several CD's for the rest of the night, but Andrew still couldn't put his finger on why to him they were not boogying, he did say he rather tired from a long day so we called it a night and retired early to await the arrival of Nick and Chris in the morning.

Saturday after an initial listen Nick suggested we move the speakers further out into the room and increase the depth of the side panels with some LP covers. This improved things all round and bass depth and extension also increased. To Andrew the speakers were now 'playing music'. His term to mean they were making his foot tap along to the music and Nick agreed. Both liked very much what the Monacor coax drivers were doing and both commented they were hearing nuances in the music they had not noticed before. Still Nick thought the bass could be better having heard them run full range without XO direct from the Longdog P6 amps. So out came the miniDSP to just help boost the bottom end bass. The end result of this experiment though it did incres the bass a little it killed the sound and showed just how bad an effect the standard minDSP was having. So this was abandoned and then it was suggested to try my Fostex T90 supertweeters with the OB's. This had a very positive effect and gave us the best sound of the day (well early evening by then) from the 3-way OB's. I learned 3 things from this:

1. miniDSP's have a detrimental affect on the sound though it may be the latest models have improved some and may not be so poor.
2. OB's need at least 1.5m or more space from walls to give there best.
3. Side wings are an important design aspect of OB's to get good bass response and definition.
So I am now going to make a new set of side frames and bases and inset my T90's into the centre baffle next and inline with the coax drivers.

Unfortunately by that time we all agreed we had had too much beer to try and swap out the coax drivers for the horn tweeters and set the fully active arrangement to test these. This we did Sunday morning.

Image
Image

Before we changed the speakers over to 2-way we refreshed our memory of the sound of the 3-ways.
For the 2-ways the horn tweeter were hooked up to my MF A300 stereo amp, and the 15" bass drivers to the P6 monoblocks.

I suggested a start XO at 1.5kHz. Nick dialled this in the miniDSP and used a very high 48dB/octave slope second order XO. We all commented how good this sounded and that had we not heard how good the 3-way baffles sounded we would all be really impressed how these sounded. We tried 1kHz and a higher XO frequency (I think) and lower order slope XO'ers buy all agreed the initial set up was the best and most satisfying a sound.

The upshot of this though is it would be near impossible to duplicate the miniDSP set up with a passive filter and that the 2-way arrangement would have to be a fully active set up to sound right. Not sure where I'll go with the 2-way OB's.

Sorry to have waffled a little and I may have got a few things wrong. Too much beer, still rather tired from a long exhausting, but thoroughly enjoyable, weekend. I'm sure the other member of the 'committee' will correct me and make further feedback and comments of there views to these speakers.

Ah! I see Nick has beaten me in feedback :oops:
Last edited by Toppsy on Sun Nov 05, 2017 5:59 pm, edited 2 times in total.
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#52 Re: MY own OB speaker project

Post by Toppsy »

IslandPink wrote: Sun Nov 05, 2017 5:32 pm Good effort !
So remind me, what's the bass unit for this ?
Mark,
they are the Monacor SP-382PA, probably one of Monacors cheapest 15" bass units. They are wired in parallel.
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#53 Re: MY own OB speaker project

Post by Nick »

Just to add to Colins, when we first tried the mini dsp to boost the bass it was between the CD and preamp, and with hindsight, was doomed to failure as the signal level was too high so the dsp input was clipping, we did drop the output of the CD player to avoid this, but I think it threw too many bits away in the cd player, so all in all it was not a success,
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#54 Re: MY own OB speaker project

Post by steve s »

Sounds like a good weekend was had gents.... and some successful conclusions gained, there are ways of overcoming most things without reverting to dsp but it's always a tradeoff to some degree
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#55 Re: MY own OB speaker project

Post by Cressy Snr »

Yes, sounds like a productive time was had. :)
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#56 Re: MY own OB speaker project

Post by pre65 »

Nice to see you lads all had a good weekend. :)

How would Nick (and others) compare Colins baffles with the James Doddington design that Nick currently uses ?
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#57 Re: MY own OB speaker project

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How would Nick (and others) compare Colins baffles with the James Doddington design that Nick currently uses
I would put them both in the same room and play the same music through the two.
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#58 Re: MY own OB speaker project

Post by pre65 »

Nick wrote: Mon Nov 06, 2017 10:16 am
How would Nick (and others) compare Colins baffles with the James Doddington design that Nick currently uses
I would put them both in the same room and play the same music through the two.
:lol:

I can see how the way I worded the question would elicit that answer. :)

Without doing such a test how do you feel Colins baffles might compare with yours Nick ?
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#59 Re: MY own OB speaker project

Post by IslandPink »

Sounds like a fair question Nick - any pros/cons between those options ?
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#60 Re: MY own OB speaker project

Post by Nick »

It is a fair question, but I dont think I can give a answer without doing a closer test between the two. They are all good, but each with a different version of good I would say. What you want to know which is better, that’s the bit I am unsure about.
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