SE Measurements

[curtis]

I'd love to curtis.
I'd get to meet you and listen to some great tunage on some great speakers.
I'd guess the HTDs sound great from all the talk, I KNOW the Ascends do from personal listening.

I'd love to just take the 1/2hr drive over...... OOOOOO wait........

I don't give much credit to what someone says about a speaker on the forums much any more unless I know the person and his/her tastes. I have heard some speakers that others love, but only make me shrug my shoulders.

One of the greatest things I enjoy when people come over to listen to the speakers, or when I go somewhere to listen to speakers, is being exposed to great music that I hadn't heard before.

[muzz]

I'm hearing ya curtis, but physics have a tendency to make me think twice.

I guess as long as folks like their speakers, then thats all that really matters.....

[Quinn]

The whole HTD thing on AVS from one person is a strange to me. HTD been around for about 5 years and has never gotten the posts like it is suddenly.

I thought about getting a pair of HTDs and doing my listening. I feel that I couldn't write anything up without it being a group listening session. I'd be written off as an Ascend homer if I didn't care for the HTDs.

I've heard the previous generation HTD 3s at a get together. That version didn't have a ribbon tweeter.

[curtis]

I've heard the previous generation HTD 3s at a get together. That version didn't have a ribbon tweeter.

It was the old Level 4's that we heard. Not a bad speaker.

[davef]

HTD is probably the only major ID loudspeaker I haven't heard or measured so I am curious about them too.

I do have some issues with the design of the Level 3 bookshelf. That style of ribbon tweeter is generally only usable from 4kHz on up -- and even that is pushing it for a small kapton ribbon. Ribbons like these usually get crossover over at around 6kHz.

According to the level 3 specs, the crossover point is 2700Hz. That is both, a very low crossover point for this style tweeter and a very high crossover point for a 6.5", stiff, high mass woofer (I must assume it is quite stiff due to the ceramic cone and it must be a heavy cone based on the impressive bass performance). These are all features not condusive to clean and accurate midrange performance. However, I could definitely be wrong and I do look forward for a chance to evaluate them in the future.

[BradJudy]

Sounds like you need to place an order Dave.

I wonder if they are going to come out with a new level 4.

[Jay_WJ]

As I described in my review, there's somthing wrong around the Level 3's crossover frequency. Most ribbon tweeters, including even highly regarded ones like Aurum Cantus, LCY, and Fountek, according to what I read in some DIYer's extensive test report, have significantly high 3rd- and higher-order harmonic distortions at frequency region below 4khz.

What I found is that the response of the Level Three around its CO frequency is weak and makes instruments sound unnaturally thin.

Anyway, I ordered Level Two to complete my speaker search for this season. I'll update my review when I audition them.

[muzz]

Speaking of measurements, I have been studying alot of graphs lately, and one of the things I've noticed is the SPL level used for +/-3db.
Why does it seems that some use 80db, and some use 85db?
I am especially paying attention to bass rolloff.

I have also noticed a sharp difference in impedance curves, cheaper speakers tend to have high spikes(40ohms ), I think I have tracked that down to crossover type, 2nd order/4th order etc...
I could be wrong on that, but there seems to be a correlation.

Now if there is a sharp spike in the audible range, wouldn't this frequency have a tendency to be lower in amplitude?
I noticed that 4th order helps keep the spikes in the lower frequencies, EDIT:Some below the speakers rated FR, and that more expensive speakers use these.

Any assistance on this would be great.

Thx

[muzz]

I know the answer to question 1, so disregard that 1 please.......

[davef]

I have also noticed a sharp difference in impedance curves, cheaper speakers tend to have high spikes(40ohms ), I think I have tracked that down to crossover type, 2nd order/4th order etc...
I could be wrong on that, but there seems to be a correlation.

Now if there is a sharp spike in the audible range, wouldn't this frequency have a tendency to be lower in amplitude?
I noticed that 4th order helps keep the spikes in the lower frequencies, EDIT:Some below the speakers rated FR, and that more expensive speakers use these.

The impedance peaks you see represent an increase in reactance of the driver at that particular frequency. The summit of the peak is the point in which the driver has the most reactance to the frequency and is usually the resonance frequency of the driver.

The crossover network used will have varying affects on the overall impedance curves, but not significant unless impedance compensation circuits (Zobel networks) are used. The reason you might see smaller peaks with higher order crossovers is simple. Those resonant peaks are audible sources of distortion and should be damped. For a mid or high frequency driver, the crossover point for those drivers should be well above the frequency of the resonant peak. One damping method is by reducing the amplitude of that particular frequency (another damping method for lower frequencies is by port / cabinet tuning) and a higher order crossover will provide greater amplitude reduction below the -3dB point of the filter when compared to a lower order crossover given the same crossover point.

Impedance curves can be used to determine the port tune or cabinet tune (for a sealed enclosure) and overall load placed on the amplifier, but they should not be used to determine loudspeaker performance.