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Re: More woofers - helps to smooth room modes [message #52213 is a reply to message #52211] Thu, 12 June 2008 19:08 Go to previous messageGo to next message
PaulW is currently offline  PaulW
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Viscount
So is that literally put the LAB12's in a 4.5 cu-foot sealed box and connect them in parallel to the existing pro 15's in the 7 Pi's? If so, I'll investigate some prices.

Paul

Re: More woofers - helps to smooth room modes [message #52214 is a reply to message #52213] Thu, 12 June 2008 20:22 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)

Yes, if your amp can handle a 3Ω load, you can use a series coil and wire across your existing speakers. But it would be better to use a plate amp mounted on the subwoofer box. They don't cost much and will allow you to set the volume level of the subs to help blend them better. Something like one of these will do nicely:


Re: More woofers - helps to smooth room modes [message #52216 is a reply to message #52214] Fri, 13 June 2008 10:48 Go to previous messageGo to next message
PaulW is currently offline  PaulW
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Wouldn't it be easier just to get a couple of small commercially available subs and hook into the system, or is the something special about the LAB12's? One reason for asking this is that my small KEF sub I use for the home cinema set-up has died and I was looking to replace it anyway, but was only going to go for relatively low powered 8" based unit.

Paul

Re: More woofers - helps to smooth room modes [message #52218 is a reply to message #52216] Fri, 13 June 2008 11:33 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)

That would be fine. The LAB12 in a 4.5ft3 box was just a suggestion. I picked it mostly for price/performance. There are plenty other options that would work well for you. The main thing is to use several woofers in strategic places in the room to smooth room modes.


Re: 7 Pi bass cabinet [message #52243 is a reply to message #52167] Wed, 25 June 2008 00:27 Go to previous messageGo to next message
Matts is currently offline  Matts
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Registered: May 2009
Grand Master
Paul, do you have any upgraded iron in your Paramours? I have a pair with the original upgraded output transformers, and they made a huge difference in the quality/quantity of the bass. I imagine the upgrades currently sold would be even more of a difference. I just finished a second pair of Pi 4's, and am familiar with the upgrade process, so it didn't bother me to have no bass to start out with. I also used Auricaps in the xovers, and they take a good 50-100 hrs to smooth out. Be patient! Get some hip-hop on 'em... haha

Re: 7 Pi bass cabinet [message #52244 is a reply to message #52243] Wed, 25 June 2008 04:29 Go to previous messageGo to next message
PaulW is currently offline  PaulW
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Matts - I have only the original iron in the Paramours, which I run on 4 ohms which providers a slightly 'tighter' sound, but with reduced output and slight loss of 'air' about the sound overall. I will be considering the MagneQuest iron later as an upgrade option, when funds become available.

The bass is almost sorted now after bringing in some room treatment - just a few more changes to make. So now my focus is moving toward the treble which I'm finding a bit hard edged - still low hours yet, but as the bass gets better the treble seems to worsen.

Paul

Re: 7 Pi bass cabinet [message #52245 is a reply to message #52244] Wed, 25 June 2008 15:52 Go to previous messageGo to next message
Matts is currently offline  Matts
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Registered: May 2009
Grand Master
Paul, So far, much of what you're experiencing seems to me to be normal for new speakers. I'd wait until you have 100 hours or so on them to tinker too much. Have you tried the 8-ohm taps? You'll be shocked at what the upgraded iron does over the whole freq spectrum. You may have room modes, etc. that do need correcting, but I'd wait until the speakers stabilize before going all out. If you upgrade caps to Auricaps or something, you go through it again... Wayne breaks his speakers in fast- with a zillion watt Crown or two. hahahaha.

Re: 7 Pi bass cabinet [message #52246 is a reply to message #52245] Wed, 25 June 2008 19:29 Go to previous messageGo to next message
PaulW is currently offline  PaulW
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Hi Matts, I use the 4 ohm tap (in preference to the 8) as although this provides a slightly less open sound and reduced output, overall the bass is better controlled and the tendency for the upper frequency shout is reduced. I'd hope the MagneQuest iron did provide a significant upgrade as the output transformer supplied as standard costs under $5! I'm also running the HF compression horn with a small (thin) amount of wadding placed in the throat to further tame the hard edge I'm hearing - hopefully this will tone down a bit over time and I can remove the wadding. But may also be an indication of upper frequency 'room effects'.

Paul

Uniform directivity [message #52248 is a reply to message #52246] Thu, 26 June 2008 13:50 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

The B&C DE250 is one of the smoothest compression drivers I've ever heard or measured. For that matter, it's one of the smoothest tweeters of any type I've measured. It doesn't reach beyond 18kHz, but up to that point, it is smooth as silk. A DE250 on an H290 or a π wood horn is as good as it gets, in my opinion.

The crossover is nailed down too. It was designed taking into account the characteristics of each driver and the sound source locations to provide constructive summing, not just straight on the forward axis but also at all angles off-axis within the 90° x 40° coverage angle. The net effect is that the reverberent field is uniform.

But if you're used to the sound of a typical direct radiator that falls off off-axis, then having a uniform reverberent field can sound fuller. There is definitely a difference. It's unnatural to me to hear speakers with non-uniform polar response, so I would expect people that are used to hearing a non-uniform sound field would notice the difference when the reverberent field was made to be uniformly charged.

Uniform directivity has been one of my main design goals for a long time. My speakers have been built like this for well over a decade, so I'm used to it. When I walk around in my room, the sound is balanced no matter where I go. I can even leave the room, walk down the hall, and the sound volume falls off but the spacial balance doesn't change. It is nice to be able to move freely in the room and hear the same tonal balance wherever I go. I like not having to sit in a specific central spot to have the sound "click" for natural imaging. When I'm listening to my speakers, the sweet spot is very large.

That's the benefit of constant directivity. It makes the spectral balance uniform throughout the room. I think speakers that generate a uniform reverberent field are much more natural sounding than those that don't.


Re: Uniform directivity [message #52251 is a reply to message #52248] Thu, 26 June 2008 14:55 Go to previous messageGo to previous message
PaulW is currently offline  PaulW
Messages: 71
Registered: May 2009
Location: UK
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I absolutely agree with everything you've said and the more I adjust and add/remove elements of room treatment, I'm coming to the conclusion that perhaps the speakers are just to big for the room (approx 195 sq feet). This combined with the seating position at no more than 11 feet makes for a very intense listening experiance. I would also mention that due to their overall clarity I have been, without realising it, playing these at much higher volumes than normal, it is only when trying to hold a conversation you realise just how loud they really are. Anyway, I'm getting there, the bass is much better balanced now, but I may have to live with a small amount of wadding in the compression horn until I can remedy these higher register (room?) artifacts I'm hearing. It is also worth perhaps noting that I'm very treble intolerant and find most speakers far too bright for my liking - so it really is issue for me to resolve as best I can. At a recent gathering of Hi-Fi enthusiasts I had to leave the room several times due to the overall sound, others didn't seem to mind finding the presentation a bit bright, for me it was just plain painful!

I actually like the 7 Pi's very much and will be aiming to remake the mid horn cabinet again as I'm not happy with the one I've done and add a more aesthetically pleasing surround for the DE250/H290.

Paul

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