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Acceptable transition freq between dipole panel and boxed sub ?
Acceptable transition freq between dipole panel and boxed sub ?
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Old 1st May 2009, 04:12 PM   #1
ashok is offline ashok
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Acceptable transition freq between dipole panel and boxed sub ?
Default Acceptable transition freq between dipole panel and boxed sub ?

I've been listening to my three way active dipole speakers and like a lot of things about it. However the bass department is disappointing. My mid is a 6 inch and bass a 12 inch driver. The bass is also listener position dependant. At about 12 feet from the speakers the low end is 'light'. At 6 feet from the drivers it sounds good with good 'weight' in the low end. Doesn't look like I can solve this with small positional changes of the speakers.

SO, I tried adding a 10 inch ( yech !?) sealed mono sub to it . WOW , it transformed the system. However all is not really well as I have not set the cross over frequency properly. I was just testing a repaired sub amp that I had built for a friend 18 years ago. As expected the bass isn't as nice as the plain dipole at 6 feet ! But it does have weight and is better than the usual boxed speaker bass.
So I'm beginning to feel that I needn't equalise my dipole to go down low with plenty of eq but let the boxed sub take over at some lower frequency.
Anyone been using such a system? I'm sure many have but how about some details about crosover freq/rolloff and listening test results. I feel 60 Hz might be a good point to crossover to keep as much of the dipole sound as possible. This is just gut feeling and not based on any maths or measurements!
Cheers.
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Old 1st May 2009, 09:16 PM   #2
Cal Weldon is offline Cal Weldon  Canada
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Acceptable transition freq between dipole panel and boxed sub ?
Hi,

It may be that you end up tuning it by ear rather than to a number. What sounds good to you is the most important, no?
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Old 1st May 2009, 09:21 PM   #3
MaVo is offline MaVo  Germany
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Depending on the frequency response of all involved drivers, crossover order and room modes, the "real" acoustical crossover point, where the one driver starts to be louder than the other one, may be not the point you dialed into the crossover but lower or higher. This means, what Cal says is the best practical advice
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Old 2nd May 2009, 01:52 AM   #4
ashok is offline ashok
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Acceptable transition freq between dipole panel and boxed sub ?
Yes of course, it always ends up at the ear !

We do need to start some place that 'might' have a good reason .
Well I'll just go ahead with my guesstimate and see how it works out. I did expect a flurry of 'number' suggestions but doesn't look like it .
However I 'feel' that a sealed box sub might work better than a reflex box. Might retain some of the tactile feel.........?
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Old 3rd May 2009, 12:52 PM   #5
paulspencer is offline paulspencer  Australia
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Your question seems to be based on the assumption that dipole bass will always sound better, and that it is a compromise when using monopole, therefore the higher you cross from monopole to dipole, the greater the SQ compromise.

I've found that monopole vs dipole can actually be very difficult to distinguish. With my current Rythmik subs I've found this true - EQ monopole vs open baffle dipole to the same response, they both sound the same (in my room).

An alternative approach is multiple monopoles, as suggested by Geddes.

Coming back to your question. First thing to do is measure! I've found dipoles don't behave exactly as you expect. Find out where they are actually rolling off. If it turns out you need EQ only below 40 Hz, then it would make sense to cross at this point. This would be ideal.

You might also experiment with placement of additional monopole subs - some locations will work better. Ideally you want to be able to measure and use eq.
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Old 3rd May 2009, 05:59 PM   #6
ashok is offline ashok
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Acceptable transition freq between dipole panel and boxed sub ?
Quote:
Your question seems to be based on the assumption that dipole bass will always sound better, and that it is a compromise when using monopole, therefore the higher you cross from monopole to dipole, the greater the SQ compromise.
Paul you hit the nail on the head !!

Multiple monopoles is out of the question for me. I'm on the last thread with respect to being thrown out of home ( due to too much equipment ). More subs and I definitely will have to find a new home !

Yes..... measure..... . measure, measure ! My 12 inch sub measures quite well but doesn't sound as I think they should after looking at ( the graph of ) what I measured.
A lower transition frequency would be ideal. I will work on that sometime this week. Weekends are becoming too busy for me . I prefer to keep eq at a minimum if possible.

Haven't done anything for the last few days with temperatures rising every day. Today it was 40 deg C at mid day ! Not to mention the accompanying high humidity ! Couldn't be worse.
Sweat , sweat , sweat all the time. Can't have aircon all over the place.
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Old 4th May 2009, 12:13 AM   #7
jamikl is offline jamikl  Australia
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I believe there was a thread in this forum a long time ago where Thorsten Loesch recommended going boxed below the lowest room node. I can't remember where I saw it though.
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Old 4th May 2009, 02:07 AM   #8
ashok is offline ashok
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Acceptable transition freq between dipole panel and boxed sub ?
Yes I remember someone mentioning the use of boxed subs with dipoles. I can't recollect the details and I think it was a post in some other thread. Will do a search again and see what it finds.
Thanks everyone for your opinions.
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Old 5th May 2009, 03:30 AM   #9
paulspencer is offline paulspencer  Australia
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Quote:
Paul you hit the nail on the head !!
Do you realise I was challenging the idea, not reinforcing it?

Open baffle bass involves either a major reduction in output, or a big increase in cost.

Consider this. You start with one 10" monopole sealed sub. To match the output you use four of the same in a H frame and give up room gain therefore a lot of extension. Four times the cost!

Now instead you decide to try four monopoles. You'll probably get a decent smooth response (perhaps even better). Perhaps even use smaller drivers.

Do you get complaints based on how many subs, or based on how loud you play them?

If you find that your subs sound way better as open baffle, then this suggests there is a problem that isn't related to dipole vs monopole. Monopole can match the sound quality of a dipole with less drivers, less cost and more output.

Of course, if you still want to do OB, I say go for it. However, don't do it thinking you can't achieve the SQ any other way.

While you have you AC on, over here in Australia we are starting to put our heaters on. It's winter!

Just one question:
If you discovered that you were able to get a monopole to sound as good as an OB dipole, would you still be interested in dipole bass?
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Old 5th May 2009, 05:41 AM   #10
ashok is offline ashok
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Acceptable transition freq between dipole panel and boxed sub ?
Hi Paul,
I meant exactly what I said .However it does look unclear what I meant.
I understood that you were challenging my 'idea' and I meant that I figured you understood that part of it ! You don't obviously subscribe to my ( current ) point of view.

Well at the moment it "appears" to me that the OB bass sounded less boomy ( at times !) and clearer than my boxed speakers. Now there could be many factors that could cause that. First of all the drivers are not the same. But I did get the impression that OB bass had a tactile feel to it that I couldn't get in my boxed sub. Maybe that my boxed sub isn't good ?
It's a sealed unit with a Qtc of about 0.6 and low Fc ( can't remember the figure ).

I've done OB with boxed bass crossed over over at 600Hz. Sounded good but not quite the same as a full range OB. But there again no point going into all this as there are so many variables involved in those units that I tried.
I'll just focus on what I'm trying now. My biggest problem being that I don't have enough time to check all possibilities.

Answer to your question about using a monople if it is as good as a dipole. The answer is YES of course. In fact I HOPE it will turn out that way . Like you said , more spl for the same power input , smaller drivers , smaller baffle etc. For the same performance I'd be crazy to use an OB sub !
Cheers.
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