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-   -   Box port or crossover dippity do (https://www.diyaudio.com/forums/multi-way/344144-box-port-crossover-dippity.html)

AllenB 22nd October 2019 06:58 AM

Holm will measure phase including delay, accurately with a one channel measurement. This way you can use the results directly, and decide while simming whether to go with different slopes or actual delay.

Do not change the woofer delay in your sim. It is already included in the measurements and you'll double up. (Erik, I think the woofer delay setting is better used with simmed baffles.)

The two things to set after a measurement are the start point and the end point. If you set each measurement to the same start point, the delay will be correctly included. This can be done in the lower impulse plot, or in the measurement options beside each measurement set on the left. (There is an auto time lock in the middle tab, but for some reason I don't like using it.) Set the time at the beginning of the earliest arriving driver :).

The gating time should be just long enough to get the lowest frequencies you need but if you need to cross into a reflection (you can see them on the impulse), you'll compromise higher frequencies.

8ntractor 23rd October 2019 09:27 AM

HI thank you

I have an old MacBook I am using as a music server and as a soundcard since it has separate mic and toslink output it works well for the measurements. I will have to figure out how to use my windows computer with the mic and output on the same jack. after reading I will first try to import the rew data. may be quicker.

with using the mtm baffle will the second woof even thou it is disconnected will it kind of work as a passive radiator and mess up the readings?

when measuring the tweeter should I start at the resonate frequency to avoid tweeter damage say 500hz?


Sorry for all of the questions. The book I am reading has a lot of information but does not really cover these issues. also how do you decide what style of crossover to use which order and which style and series or parallel. Mr Weems does a good job of explaining the crossover and the math to choose components but I really don't get how to make the choice of which crossover. thanks again

AllenB 23rd October 2019 11:07 AM

Quote:

Originally Posted by 8ntractor
when measuring the tweeter should I start at the resonate frequency to avoid tweeter damage say 500hz?

I'd be interested in what Erik has to say here as I haven't used a dome designed in recent years. I've always found them to handle a 20Hz sweep at good volumes but am reluctant to recommend it.
Quote:

Originally Posted by 8ntractor (https://www.diyaudio.com/forums/multi-way/344144-box-port-crossover-dippity-post5952993.html#post5952993)
the mic and output on the same jack.

Is there a reason you can't use one output channel from a stereo output and one input from a stereo input?


IntelHDA will do jack retasking if you have anything unusual you want to do.



Quote:

with using the mtm baffle will the second woof even thou it is disconnected will it kind of work as a passive radiator and mess up the readings?
Since both are meant to play together over the same band, why not measure them together? Even if doing full angular measurements it would be best to have them together. Unless maybe you plan to do a half measured, half simmed crossover.

AllenB 23rd October 2019 11:22 AM

Quote:

how do you decide what style of crossover to use which order and which style and series or parallel.
The order, the slope will hopefully be gradual but in reality design constraints tend to push things tighter. I reckon that when you give it enough thought, set your priorities and learn about your drivers, you'll begin to settle on a crossover frequency.

Say then you find that there is a woofer breakup mode at some frequency and you want things to be down by some level of dB at that point, now you have your slope decided. The tweeter could also be the limiter.

You could get the same result with a series or parallel crossover if you try. However I would stay with parallel for now, unless you are planning to get the best results you can with fewer components?

8ntractor 23rd October 2019 03:42 PM

thank you Allen
I think the reason for measuring one driver is how you enter it in sim. as two individual drivers at least that was my thinking. Is there an issue with measuring in REW and transfering the data to Holm and the gating ? I tried it and it seems to work ok.


thank you I will go parallel I use bi wire so I think parallel may be better for that also.

AllenB 23rd October 2019 10:09 PM

Quote:

Is there an issue with measuring in REW and transfering the data to Holm and the gating ?
It depends how you do it. If you transfer a frequency response plot, the delayed energy including speaker diffraction will not have its delay registered. You would need to transfer an impulse response. However, it can't be an impulse that was constructed from the frequency response either. The thing with Holm is that it knows the signal it put out, and specifically waits for its return so it knows which parts of the incoming signal are direct and which are delayed.

Regarding bi-wire, yes use parallel.

AllenB 23rd October 2019 10:30 PM

Quote:

Originally Posted by 8ntractor (https://www.diyaudio.com/forums/multi-way/344144-box-port-crossover-dippity-post5953244.html#post5953244)
I think the reason for measuring one driver is how you enter it in sim.

Sims tend to cater for two types. Those that want to measure everything and sim the crossover, and those that start with manufacturer response plots and want to sim the whole speaker around it. (Of the first type, there are those that use single plots per driver and those that use many.) .. This is why these options exist.

8ntractor 24th October 2019 10:05 AM

thank you AllenB I have spent some time on holms and will continue to do so. I will try to get it to do the measurements. The one meter measurement is troublesome. moving the speaker from across the room to the length of the room totally changed the woofer response.

AllenB 24th October 2019 01:48 PM

If you move them around the middle of the room you'll get a larger reflection free time. Try to position the speaker and the mic around half the room height.

8ntractor 24th October 2019 05:55 PM

every movement changes the FR. Reading Weems he builds a 6 ft round baffle. this may sound crazy but I am not sure of what I am shooting for I know I want an FR to match the one posted slight rolloff to the high end. I think I know that the impedance should be smooth with a small hump in the bass and a small hump at the crossover and stay above 4ohms. Is there more that I am missing.


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