Another PAP inspired OB job

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iansr
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Re: Another PAP inspired OB job

Post by iansr » Mon Nov 19, 2018 9:12 am

PS. Have you got a link to that Art Welter testing ?
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iansr
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Re: Another PAP inspired OB job

Post by iansr » Mon Nov 19, 2018 1:04 pm

Found it.
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chris661
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Re: Another PAP inspired OB job

Post by chris661 » Tue Nov 20, 2018 9:09 am

iansr wrote:
Mon Nov 19, 2018 9:06 am
Chris
I haven’t paid for them yet but I have found a nice pair of the JBL drivers. The intended crossover point is c.600hz. I’m anticipating some bass boost will be needed for the woofers and that some EQ will be required at various points. Interesting that you got such good bass from a low Q woofer on OB. There does seem to be a minority school of thought that a high Qts is not essential.
With regards to Qts on an OB, it's obvious that low-Q drivers need help via EQ. However, I think the benefit is there. Low-Q drivers have powerful motors that can control the cone. No overshoot, start and stop on a sixpence, etc etc. The higher-Q drivers I've been exposed to always had a slightly mushy quality to me*, where the Beyma units were, as I said, the best low-frequency reproduction I've ever heard.
* Then again, it could equally have been an unknown room, the amplification, etc.

I might put something temporary together for the next Owston.

Chris

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Re: Another PAP inspired OB job

Post by steve s » Tue Nov 20, 2018 10:24 am

chris661 wrote:
Tue Nov 20, 2018 9:09 am

With regards to Qts on an OB, it's obvious that low-Q drivers need help via EQ. However, I think the benefit is there. Low-Q drivers have powerful motors that can control the cone. No overshoot, start and stop on a sixpence, etc etc. The higher-Q drivers I've been exposed to always had a slightly mushy quality to me*, where the Beyma units were, as I said, the best low-frequency reproduction I've ever heard.
* Then again, it could equally have been an unknown room, the amplification, etc.

I might put something temporary together for the next Owston.

Chris
Totally agree with the above Chris, but my ported design seems to work well without the need for a separate amp.

I have used twin 15s and twin 18s
Neither seems to work really well in a plain baffle. Mixing an 18 with a high eff 12 has worked the best for me as they seem to blend together better and give better dynamics and leading edges to the sound.( the 18 starts to sound slow as the freq rises, the 12 is quicker so produces the leading edges better and the larger driver giving a little weight to the sound
Getting good drivers that match is the difficult thing.
There are far to many internet experts when it comes to speakers in my view... so it's difficult to job to know the very best route.
Your welcome to listen to my set up If you want..
What speakers do you use at the moment ?
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IslandPink
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Re: Another PAP inspired OB job

Post by IslandPink » Tue Nov 20, 2018 11:22 am

chris661 wrote:
Tue Nov 20, 2018 9:09 am
With regards to Qts on an OB, it's obvious that low-Q drivers need help via EQ. However, I think the benefit is there. Low-Q drivers have powerful motors that can control the cone. No overshoot, start and stop on a sixpence, etc etc. The higher-Q drivers I've been exposed to always had a slightly mushy quality to me*, where the Beyma units were, as I said, the best low-frequency reproduction I've ever heard.
* Then again, it could equally have been an unknown room, the amplification, etc.

I might put something temporary together for the next Owston.
I understand why low-Q driver could sound better. With the driver operating on the 'upslope' of the response ( velocity-controlled region ) the phase shift ( & hence group delay ) from bass to mids is low, so dynamics and tone ought to be good. Another way of saying the powerful motor controls the cone.
The idea of 27dB of boost does worry me a bit though - this means if you can run 5W in the midrange, the speaker needs approx. 2.5kW to provide for the low bass. Sort-of limits your amp options !

As I said to Nick yesterday - you really need a horn for the low-Q driver :D
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iansr
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Re: Another PAP inspired OB job

Post by iansr » Tue Nov 20, 2018 11:37 am

There are clearly diverging views on this but the prevailing view does seem to be that you should have a higher Qts for OB i.e. it’s a compromise buts it’s a better one than the alternative. I’m in no position to argue so I think the lowest Qts I would go is about 0.5, and preferably higher. Notwithstanding what Lynn Olsen concluded about the normal AE woofers, there is a lot of love out there for the OB variants so I’m drawn to them. And they look the DBs to boot.
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Re: Another PAP inspired OB job

Post by chris661 » Tue Nov 20, 2018 12:08 pm

IslandPink wrote:
Tue Nov 20, 2018 11:22 am
I understand why low-Q driver could sound better. With the driver operating on the 'upslope' of the response ( velocity-controlled region ) the phase shift ( & hence group delay ) from bass to mids is low, so dynamics and tone ought to be good. Another way of saying the powerful motor controls the cone.
The idea of 27dB of boost does worry me a bit though - this means if you can run 5W in the midrange, the speaker needs approx. 2.5kW to provide for the low bass. Sort-of limits your amp options !

As I said to Nick yesterday - you really need a horn for the low-Q driver :D
Hi Mark,

Yeah, the power requirements were on the steep side. Running a live sound business means I do have some fun toys to play with, though - check out the Crown MA12000i for example.
It's been a while since I had that OB, but IIRC I was lighting up the -6dB light on a Behringer NU6000 which was driving the 15"s. -6dB is 300w per driver, so the power levels were in excess of that. Cone excursion was getting to around 30mm p/p, which is asking quite a lot. However, this was enough to measure flat down to 25Hz, and I was playing bass-heavy material at demo levels. Good fun, and if the driver's weren't broken in before, they were afterwards.

I think the high vs low Qts debate goes like this:
High Qts means the system can still be efficient at LF, at the potential expense of "sloppy" bass*.
Low Qts means the system has low efficiency at LF, and will therefore require a lot of power dumping in to get the levels up.

It's important to note that both systems have equal requirements when it comes to cone excursion, it's just that the high-efficiency system will use that excursion more readily around Fs.

*It's difficult to describe sounds with words, but it's akin to what I heard at Steve's meetup a little while ago. It was like the big solid state amps were telling the cone exactly how far to move and then come back again, while the transformer-coupled valve amps were more "we'll set off in that direction and see where we end up". That's exaggerating the difference, of course, but hopefully you see my point.

A mid-Qts option would probably be a good move - it keeps power levels sane while hopefully retaining the performance of a lower-Q driver.

Chris
If you can see the cone move regularly, you haven't got enough speaker.

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Re: Another PAP inspired OB job

Post by MJK » Wed Nov 21, 2018 1:19 am

Simulate the different 15" woofers (high and low Qts) in the baffle you have in mind with either a passive or active crossover in BASTA and see what you get. No guessing or assuming, you design the speaker to meet you goals and select the driver that works best. No "experts" needed.

http://www.tolvan.com/index.php?page=/basta/basta.php
Martin

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Re: Another PAP inspired OB job

Post by iansr » Wed Nov 21, 2018 5:00 pm

Thanks, that looks like a really powerful tool. It also looks like it would require some serious time investment to learn how to use it!
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Re: Another PAP inspired OB job

Post by MJK » Thu Nov 22, 2018 1:26 am

If you have the driver T/S parameters then it will only take an hour or two of playing to get some decent results. It is not that hard, just jump in. It is free, what have you got to loose other than a little time. Faster and cheaper than trial and error building.
Martin

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Re: Another PAP inspired OB job

Post by iansr » Fri Nov 23, 2018 11:43 am

OK thanks Martin, I’ll have a go.
In the meantime, just came across these
http://www.sbacoustics.com/index.php/pr ... 4nrx75-16/

SBA seem to get very good write ups.
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Ali Tait
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Re: Another PAP inspired OB job

Post by Ali Tait » Sat Nov 24, 2018 10:43 am

The tweeters are good.
Image[/img]

iansr
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Re: Another PAP inspired OB job

Post by iansr » Sat Nov 24, 2018 11:06 am

Good to hear Ali 😀. They were recommended by the aforementioned M.

Re the woofers, I’ve negotiated a good deal on 8 x AE Dipole 12”, so the new plan is 4 per side. 2 above the horn and 2 below like the PAP Quintet.
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Re: Another PAP inspired OB job

Post by chris661 » Sat Nov 24, 2018 11:48 am

That'll be pretty amazing.
Looking forward to the results.

Chris

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Re: Another PAP inspired OB job

Post by iansr » Fri Dec 14, 2018 10:56 pm

Update: I bought a used pair of Yamamoto F350 horns made from solid Asada wood. Currently in transit from Japan. I’ve also ordered some aluminium 1.5 to 2 inch throat adapters for them. The next job will be to do some outdoor measurements of the various drivers.
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